DETERMINATION OF TRUE FORMATION RESISTIVITY

The present invention relates generally to apparatus and methods related
to oil and gas exploration.
Backgroiind
In drilling wells for oil and gas exploration, understanding the structure
and properties of the associated geological formation provides information to aid
10 such exploration. True formation resistivity is a key petrophysical parameter
(hat. helps petrophysicists to characterize and develop a reservoir. A resistivity
measurement presents an electrical property of formations surrounding the
logging tools, where different formations have distinct and unique resistivity
readings. For example, a salt water formation presents a low resistivity reading
15 and an oil reservoir presents a high resistivity reading. A continuous resistivity
log allows petrophysicists to recognize formation geology and to develop a good
wellbore placement program for maximum oil production in the reservoir.
However, a resistivity measurement is often problematic in layered formations,
especially while the logging tool is near the boundary between the layers, each
20 with different resistivity value. Such boundary effects, known as polarization
horn effects, can produce significant responses to conventional propagation
electromagnetic (EM) wave tools and unrealistic resistivity reading with very
high value may be measured. Consequently, misinterpretation of formation
geology may occur based on. such resistivity measurements.
25 In general, one-dimensional (ID) inversion is often used to eliminate
such horn effects and explore the true formation, resistivity profiles. Inversion
operations can include a comparison of measurements to predictions of a model
such that a value or spatial variation of a physical property can be determined.
In inversion, measured data may be applied to construct a mode] that is
30 consistent with the data. For example, an inversion operation can include
determining a variation of electrical conductivity in a formation from
measurements of induced electric and magnetic fields. Other techniques, such as
1
a forward model, deal with calculating expected observed values wilh respect i:o
an assumed model. In zero-dimensional (OD) inversion, there is no variation in
the formation, such as in a homogenous formation. In. 1D modeling, there is
variation in one direction such as a formation of parallel layers. In. two
5 dimensional (2D) modeling, there is variation in two directions. In three
dimensional (3D) modeling, there is variation in three directions. However,
inversion schemes can be complicated and can have several uncertainties, such
as initial formation mode], number of input signals for the inversion, etc., that
may cause different inverted results. The usefulness of such traditional
10 measurements and inversion analysis may be related to the precision or quality
of the information derived from measurements and processes to evaluate the
information.
Brief Description of the Drawings
15 Figure 1 shows a block diagram of an example system to determine
formation resistivity, according to various embodiments.
Figure 2 illustrates an electromagnetic tool located in a homogeneous
formation, medium, according to various embodiments.
Figure 3 A shows an example of phase attenuation conversion charts,
20 according to various embodiments.
Figure 3B shows an example of attenuation conversion charts, according
to various embodiments.
Figure 4 illustrates an electromagnetic tool equipped with a tilted antenna
design, according to various embodiments.
25 Figure 5 depicts a three-layer isotropic formation model, according to
various embodiments.
Figure 6 shows a configuration of an electromagnetic measurement tool
equipped with symmetrical antenna structures, according to various
embodiments.
30 Figure 7A shows compensated average phase resistivity measurements of
two measurement tools in the formation model of Figure 5 with relative dip
angle of 85°, according to various embodiments.
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WO 2014/120150 PCT/1JS2013/023826"
Figure 7B shows compensated average attenuation resistivity
measurements of two tools in the formation model of Figure 5 with relative dip
angle of 85°, according to various embodiments.
Figure 8A shows compensated average phase measurements of the tool
5 structure in Figure 6 with non-tilted transmitters and various tilted receivers in
formation model of Figure 5 with relative dip angle of 85°, according to various
embodiments.
Figure 8B Compensated average attenuation resistivity measurements of
the tool structure in Figure 6 with non-tilted transmitters and various tilted
10 receivers in formation model of Figure 5 with relative dip angle of 85°,
according to various embodiments.
Figure 9A shows compensated average phase measurements of the tool
structure in Figure 6 with non-tilted transmitters and various tilted receivers in
formation, model of Figure 5 with relative dip angle of 75°, according to various
15 embodiments.
Figure 9B shows compensated average attenuation resistivity
measurements of the tool structure in Figure 6 with non-tilted transmitters and
various tilted receivers in. formation, model of Figure 5 with relative dip angle of
75°, according to various embodiments.
20 Figure 10A shows compensated average phase measurements of the tool
structure in Figure 6 wish various orientations of the transmitters and the
receivers in formation model of Figure 5 with relative dip angle of 85°,
according to various embodiments.
Figure 10B shows compensated average attenuation resistivity
25 measurements of the tool structure in. Figure 6 with various orientations of the
transmitters and the receivers in formation model of Figure 5 with relative dip
angle of 85°, according to various embodiments.
Figure 11 shows a configuration of a measurement, tool's azimuthal angle
at each bin direction, according to various embodiments.
30 Figures 12A-12C show tool antenna structures and defined quadrants for
tools arranged with antennas having tilted angles, according to various
embodiments.
WO 2014/120150 PCT/1JS2013/023826"
Figures 13A-13C show tool antenna structures to provide similar
functionalities as structures in Figures 12A-12B, according to various
einboditnents,
Figures 1.4A-1.4C show tool antenna structures to provide compensated
5 resistivity measurements with respect to arbitrary tilted transmitted s) and tilted
receiver(s), according to various embodiments,
Figure 15 shows a configuration of a nseasurement tool structured to
provide deep azimuthal resistivity tneasuretnenls, according to various
embodiments,
10 Figure 16A shows cotnpensated average phase resistivity responses from
the measurement tool of Figure 15 for two specific tilted receivers, according to
various embodiments.
Figure 16B shows a geosignal phase image from the measurement tool of
Figure 15, according to various embodiments.
15 Figure 17 shows a flowchart, of an example processing scheme to
determine true formation resistivity, according to various embodiments,
Figure 18 shows a flowchart of an example processing scheme to
determine true formation resistivity, according to various embodiments,
Figure 19A shows compensated average phase measurements of the tool
20 structure in Figure 6 with various orientations of the transmitters and the
receivers in formation model of Figure 5 with relative dip angle of 0°, according
to various embodiments,
Figure 19B shows compensated average attenuation resistivity
measurements of the tool structure in Figure 6 with various orientations of the
25 transmitters and the receivers in formation mode] in Figure 5 with relative dip
angle of 0°, according to various embodiments,
Figure 20 shows features of an example method to determine true
formation resistivity, in accordance with various embodiments.
Figure 21 shows features of an example method to determine true
30 formation resistivity, in accordance with various embodiments,
Figure 22 shows features of an example method to determine true
formation resistivity, in accordance with various embodiments.
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WO 2014/120150 PCT/1JS2013/023826"
Figure 23 shows features of an example method to determine true
formation resistivity, in accordance with various embodiments,
Figure 24 depicts a block diagram of features of an example system
operable to determine true formation resistivity, in. accordance with various
5 embodiments.
Figure 25 depicts an embodiment of a system at a drilling site, where the
system includes an apparatus operable to determine true formation resistivity, in
accordance with various embodiments.
10 D§lslMI)fiscrigtion
The following detailed description refers to the accompanying drawings
that show, by way of illustration and not limitation, various embodiments in
which the invention may be practiced. These embodiments are described in
sufficient detail to enable those skilled in the art: to practice these and other
15 embodiments. Other embodiments may be utilized, and structural, logical, and
electrical changes may be made to these embodiments. The various
embodiments are not necessarily mutually exclusive, as some embodiments can
be combined with one or more other embodiments to form new embodiments.
The following detailed description is, therefore, not to be taken in a limiting
20 sense,
Figure 1 shows a block diagram of an embodiment of a system 1 (X)
operable to determine formation resistivity. The system 1(X) includes a
measurement tool 105 operable in a well. The measurement tool 105 has an
arrangement of sensors 111-1, 111-2. . , lll-(N-l), 111-N along a longitudinal
25 axis 117 of measurement tool 1.05. Each sensor 111.-1, 11.1.-2 . . . 1.1.1-(N-1),
111 -N can be utilized as a transmitting sensor or a receiving sensor under the
control of a control unit: 115. The transmitting sensors and receiving sensors can
be realized as transmitter antennas and receiver antennas. The sensors 1.11-1,
111 -2 . . . 111 -(N-1), 111 -N may be arranged as a plurality of groups, where
30 each group includes a transmitter sensor and a receiver sensor spaced apart by a
separation distance. Sensors disposed in the various groups can be structured in
a number of ways that: may depend on the application of the measurement: tool
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WO 2014/120150 PCT/1JS2013/023826"
1.05 in a measurement process. Each group can include tilted antennas and nontilted
antennas. Each group can include a grouping of a number of transmitter
sensors and a number of receiver sensors. For example, each group can include,
but is not limited to, a grouping of two transmitters and two receivers. The two
5 transmitters and the two receivers in a grouping can be arranged with a
symmetrical orientation. Sensors that are tilted can be arranged with respect to a
longitudinal axis 11.7. Groups having different separation distances between
transmitting sensors and receivers can be used to investigate formations over
different distances from the measurement tool 105. The larger separation
10 distance corresponds to investigating formations over larger distances Irons the
tool.
The control unit 11.5 is operable to manage generation of a probe signal
from the transmitter sensor from each group and collection of received signals in
the respective group, where She received signals can be acquired relative to a
15 rotation of the measurement tool 105. The rotation of the measurement tool 105
can he partitioned into N segments, called bins, in which completion of the N
bins is one complete rotation of the tool, N > 2, where Ar is the total number of
bins. Each bin has an associated azimuthal angle cp. In various applications, N
can be equal to 32. However, N can be set to other values. The received signals
20 can correspond to She bins associated wish She measurement tool 105. The
control unit 115 is operable to select one or more transmitter sensors from
among the sensors in the arrangement of the sensors 111-1,111-2... lll-(N-l),
111 -N and to select one or more receiver sensors from among the sensors in the
arrangement of the sensors 111.-1,1.11-2 . . . lll-(N-l), 1.11-N. System 100 can
25 include a processing unit 120 to process the received signals to determine the
formation resistivity, which can include evaluating She validity of the measured
formation resistivity.
The processing unit 120 can be structured to control and process
measurement values from operating the measurement tool 105. The processing
30 uniS: 120 can be structured to acquire measurement, values from operating She
measurement tool 105 in a borehole corresponding to drilling at a dip angle
greater than zero. The measurement tool 105 once structured with transmitter
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WO 2014/120150 PCT/1JS2013/023826
antennas and receiver antennas and deployed may have a fixed arrangement of
transmitter and receiver antennas. The fixed arrangement can include transmitter
antennas antl receiver antennas a!: fixed distances from each other with iili: angles
with respect to the longitudinal axis of the measurement tool 1.05. Non-tilted
5 antennas have a tilt angle of 0°. Tilted antennas may have a tilt angle of ranging
from above 0° to near 90°. The processing unit 120 can treat the arrangement of
transmitter and receiver angles as having antennas whose tilt angle can operably
be adjusted. With the deployed the measurement tool 105 having fixed tilt
angles, treating the arrangement of transmitter and receiver angles as having
10 antennas whose tilt angle can operably be adjusted effectively defines a virtual
arrangement of the same transmitter and receiver antennas,
Instructions stored of the processing unit: 120 can be executed to generate
new measurement values for the virtual arrangement of the same transmitter and
receiver antennas by processing the measurement values front operating the
15 measurement tool, where the processing uses a relationship including a tilt angle
of a receiver antenna in the lixed arrangement that is different from a tilt angle of
the same receiver antenna in the virtual arrangement. The new measurements
can be used in the processing unit 120 to determine an estimate of a true
formation resistivity of Che formation being investigated. In an embodiment,
20 from acquiring values from making measurements during a rotation of the
measurement tool relative to N bins, the processing unit 120 can generate new
measurement values, which can include generating V^ (i) according to
^'(o=^"(i>^+-yv;"(oxsin(gri"g f i ) ,i=iz...,N a)
for the fixed arrangement having two receiver antennas and two transmitter
25 antennas, where T;„j indicates different available transmitters) and R;„j
indicates different available receiver(s) and V^""' (i) is the signal measured at
receiver Rind, in response to a signal being transmitted from transmitter 7;„j> in
bin /", i=l . . . N, and V^ (/) is the new measurement value for the receiver
antenna /?,-„,/ at tilt angle 0r> in the virtual arrangement with the receiver antenna
30 Riflj at tilt angle 6t\ in the fixed arrangement at which the measurement values
WO 2014/120150 PCT/1JS2013/023826"
from operating the measurement tool are acquired.
The processing unit 120 can be used with a number of antenna
arrangements to generate new measurement values via a transformation
procedure. For example, in the fixed arrangement and in the virtual
5 arrangement, two transmitters are non-tilted. Alternatively, the two transmitters
can be tilted in the fixed arrangement such that two transmitters are
perpendicular to two receivers. For transmitters having tilted antennas,
generating new measurement values can include determining coupling
components to calculate V^™!(0 from, which. V^ (0 is generated. The fixed
10 arrangement can include two transmitters or two receivers arranged such that
separation between each transmitter and each receiver is at a fixed distance.
The transformation procedure performed by the processing unit 120 can
be implemented to avoid the polarization horn effects. As noted, polarization
horn effects occur when a measurement tool is near a boundary between
15 formation layers of different resistivity. Determination that the measurement
tool 105 is near a boundary may be used to initiate the transformation procedure.
Proximity to a boundary between formation layers can be provided by use of
geosignals.
Geosignals are indicative of the direction of drilling tools downhole as
20 well as being capable of detecting boundaries. Capabilities of geosignals are
useful in geosteering to optimize well placement for maximum oil recovery.
Apparatus and processing schemes, as discussed herein, allow for the generation
of a geosignal. A geosignal may be based one or more properties of earth
formations as a function of distance from a reference point. The geosignals
25 defined herein have a variety of applications. Geosignals also provide azimuthal
orientation information of rotary tools. In addition, the geosignal can be used for
the calculation of distance to bed boundaries.
Geosignals can be defined in a number of ways. For example, two kinds
of geosignal definitions, VGcol and VGeo2, have been used with respect to a signal
30 acquired at a receiver in response to a signal transmitted from a transmitter.
Geosignal V^ can. be defined by
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WO 2014/120150 PCT/1JS2013/023826"
and geosignal VGfg2 can. be expressed as
V (i)^Yl^lj = h...>N, (3)
In these geosignals, ; is the index of bin number of a rotating tool, L- are
defined based on the quadrants in Figure 6, where the z direction is tool's
drilling direction and the x direction is often determined by magnetometer or
gravity devices. With an operating frequency of 2 MHz, spacing (SO of 8 inches
30 between receivers, and spacing (S2) of 16 inches from a transmitter to the center
of the two receivers, Figures 7 A-7B demonstrate the average phase and
attenuation resistivity responses when two commercial LWD tools are operated
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WO 2014/120150 PCT/1JS2013/023826"
in the formation model in Figure 5 with the relative dip angle of 85°. One of the
two tools was equipped with all non-tilted antenna loops and the other tool was
installed with tilted central receivers (0t = 45°) and non-tilted transmitters.
As illustrated in Figures 7A-7B, the measurements from both tools are
5 essentially the same such that basically only one curve is shown in each of
Figures 7A-7BL Both tools measure good resistivity reading consistent with true
formation resistivity, while the tools are away from the boundaries. However,
resistivity reading becomes unrealistic and do not present true formation
resistivity value at and near a boundary. Using such unrealistic measurements
10 without performing a 1D inversion, misinterpretation of formation geology can
occur.
In various embodiments, techniques are implemented to directly
determine true formation resistivity without running a 1D inversion. First, sets
of measurements were considered with an arrangement of the measurement: tool
15 in Figure 6 with the transmitters' tilt angle fixed to be 0° and the receivers' tilt
angle adjusted from 0° to 85°. Similar to Figures 7A-7B with the same
formation parameters in Figure 5 and relative dip angle of 85°, average
resistivity measurements were computed with respect to several specific
orientations of the receivers with non-tilted transmitters. Figure 8A shows
20 compensated average phase measurements of the tool structure in Figure 6 with
non-tilted transmitters and various tilted receivers in formation model of Figure
5 with relative dip angle of 85°. The group 841 of results includes non-tilted
transmitters and receivers having tilt angles of 5°, 15°, 25°, 35°, and 45°. Curves
842, 844, 846, and 848 of results are for non-tilted transmitters and receivers
25 having tilt angles of 55°, 65°, 75°, and 85°, respectively. Figure 8B shows
compensated average attenuation resistivity measurements of the tool structure
in Figure 6 with non-tilted transmitters and various tilted receivers in formation
model of Figure 5 with relative dip angle of 85°. The group 851 of results
includes non-tilted transmitters and receivers having tilt angles of 5°, 15°, 25°,
30 35°, and 45°. Curves 852, 854, 856, and 858 of results are for non-tilted
transmitters and receivers having tilt angles of 55°, 65°, 75°, and 85°,
respectively. The results provide conclusions that some receiver orientations
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WO 2014/120150 PCT/1JS2013/023826"
produce very good phase resistivity measurements with no polarization horns
and close to true formation resistivity value; on the other hand, at the same
receiver orientations, corresponding attenuation resistivity measurements
enhance horn effects while the measurement tool is relatively far away from the
5 boundaries.
For example, the tool structure with 85° tilted receivers develops average
phase resistivity reading similar to the true resistivity in layers with resistivity
value of lilm, whereas, in the middle layer with resistivity value of 20ft' m, the
tool structure with 65° tilted receivers gives average phase resistivity reading
10 close to She formation model. On She other hand, attenuation resistivity
responses of the structure with 85° tilted receivers incur a horn effect before the
measurement tool passes She boundaries. For example, the horn effect for Shis
structure occurs approximately 0.65 ft before the boundary when tool is located
in the \Cl- m formation, and approximately 0.98 ft before She boundary when tool
15 is located in the 200- m formation. Consequently, by adjusting the orientations
of the receivers, the coiTesponding phase resistivity measurements can be used to
denote true formation resistivity reading and the corresponding attenuation
resistivity can be utilized So figure out boundary positions.
Figures 9A-9B show the resistivity measurements for the relative dip
20 angle being 75°. Figure 9A shows compensated average phase measurements of
the tool structure in F'igure 6 with non-tilted transmitters and various tilted
receivers in formation model of Figure 5 with relative dip angle of 75°. The
group 941 of results includes non-tilted transmitters and receivers having tilt
angles of 5°, 15°, 25°, 35°, and 45°. Curves 942, 944, 946, and 948 of results
25 are for non-tilted transmitters and receivers having Silt angles of 55°, 65°, 75°,
and 85°, respectively. Figure 9B shows compensated average attenuation
resistivity measurements of She tool structure in Figure 6 with non-tilted
transmitters and various Silted receivers in formation, model of Figure 5 with.
relative dip angle of 75°. The group 951 of results includes non-tilted
30 transmitters and receivers having tilt angles of 5°, 15°, 25°, 35°, and 45°. Curves
952,954,956, and 958 of results are for non-tilted transmitters and receivers
having Silt angles of 55°, 65°, 75°, and 85°, respectively. Again, changing
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WO 2014/120150 PCT/1JS2013/023826"
receiver orientations lias no influence on resistivity measurements if the
measurement tool is far away from the boundaries, whereas it enables different
resistivity reading nearby She boundary. Such findings can be utilized to directly
evaluate true formation resistivity and detect boundary positions.
5 In addition, it has been discovered that resistivity measurements
calculated by traditional conversion charts can be also acquired by antenna
structures where transmitter(s)' orientations are perpendicular to receiver(s)'
orientations. Figures 10A-10B show She compensated phase and attenuation
resistivity responses at relative dip angle of 85° of two perpendicular
10 arrangements between She transmitler(s) and She receiver(s), where one
arrangement has the transmitters' tilt angle of-45° and the receivers' tilt angle
of 45° (curves 1042 and 1052) and the other arrangement has She transmitters'
tilt angle of 5° and the receivers' tilt angle of-85° (curves 1044 and 1054).
Figures 10A-10B also compares the resistivity responses of another two
15 structures where both are equipped with non-tilted transmitters but the receivers
are tilted at two different tilt angles (curves 1046 and 1056 for receiver tilt angle
of 45° and curve 1048 and 1058 for receiver tilt angle of 85°). As illustrated in
Figures 10A-10B, similar conclusions reveal that phase resistivity measurements
of specific antenna orientations significantly reduce or eliminate resistivity horn
20 effects and accurately estimate true formation resistivity; conversely, attenuation
resistivity measurements of She same antenna orientations emphasize horn
effects and early discovery of nearby boundaries.
The findings discussed above were made with respect to two kinds of
tool structures and corresponding simulations that were performed. One tool
25 structure is equipped with non-tilted transmitters and tilted central receivers, and
the other structure is established by both tilted transmitters and tilted receivers
with perpendicular arrangements between, the transmitS:er(s) and She receiver(s).
Owing So reciprocity theorem, all She described transmitters and receivers can be
exchangeable. Consequently, similar simulation results and conclusions can be
30 obtained if a transmitter becomes a receiver or a receiver becomes a transmitter.
Consider the tool structure of Figure 6 with non-tilted transmitters and
arbitrary Silted receivers. With a firing of She transmitters (Ti or JY), She voltage
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WO 2014/120150 PCT/1JS2013/023826
received at one of the two central receivers can be written as:
y^ ((j>) = V^*M cox0r + Vj;;"'RM sin 6>.cos^ (6)
Where, Tind indicates transmitters and Rind indicates receivers (ind is 1 or 2), is
tool a/.imuthai angle, Qr is tilt angle of the receivers, v!},jR",J is a coupling
5 component: when the transmitter Tind is orientated in z direction and the receiver
Rf„,i is orientated in z direction in Figure 6, and y^R^ is a coupling component
when (he transmitter 7,w is orientated in z direction and the receiver Rf„j is
orientated in x direction in Figure 6. In practice, the measurements of a
complete tool rotation are divided by A* bins with each at a distinct azimuthal
10 angle$, as shown in Figure 11. liquation (6) can be modified as
vr"(i) = V>*"cos0r+V.^f f"sin0roos# , i' = l, 2 ;V (7)
where i denotes different bins defined in Figure 11. The measurement tool to
make measurements in a borehole have the receivers with tilt angles fixed that
cannot be randomly changed. In a measurement tool structure for LWD
15 applications, owing to LWD rotating operation, all azimuthal measurements of a
complete rotation are available during downhole drilling. Consider an EM tool
with tilted receivers, having tilt angle of {),\, 0(t^O, and non-tilted transmitters.
Based on equation (7), an average of all azimuthal measurements of a complete
rotation can be expressed as:
20 -1J V^ (0 = V*""" cos 0r} (8)
liquation (9) can be derived from equation (7) and equation (8) to obtain a new
azimuthal measurement Vl"'" (i) received at: the same receiver but with different
tilt angle, 0L-2'.
v;wo>v;wo>^+-yv^tox^-"^} ,*=1,2,...,*• c»
*" • *« • siRffr] Nfe «<« sin.(2<9H)
25 Since 0L-j is known and defined by the tool design, equation (9) presents an
approach to calculate the new azimuthal measurements Vj"' (0 associated with
the desired tilted receivers with tilt angle B& on the basis of raw
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WO 2014/120150 PCT/1JS2013/023826"
measurements Vj"' (/).
Consider the tool structure of Figure 6 with both tilted transmitters and
tilted receivers with perpendicular arrangement between the transmitters) and
the receiver(s). A measurement signal received at a receiver corresponding to
5 the transmitting signal of a transmitter can be expressed as:
y';.A< _y *;.«*«,• \/':«*,.« + y *;.«*,<• i..';„•*.« y *;.«*«,• y *;.«*..<• _ \ / ' w *«
v';"M0 = ° ™ E eos2£ ~~2—• £ siji2<* "a—•— •- —em& ~-E_ s: ^ i , ,^
4 4 2 2
- j y f i A j _y''^IiiJ _yl;jR;j
+ ^ ^ 2 j = 1 2 A'
4
(10)
V|, , A i is a coupling component when the transmitter T,:na- is orientated in jf
direction ancl She receiver Riflj is orientated in. k direction in. Figure &,j or k
10 denotes x, y, or z direction. Consequently, nine coupling components are
essential to decouple equation. (10) and then calculate new measurements of
desired antenna orientations. This demonstrates that the related processing
schemes are more complicated for a tool structure wish tilted transmitters and
tilted receivers than the tool structure with non-tilted transmitters and tilted
15 receivers.
In order to adjust bosh transmitter(s) and receiver(s) orientations and
obtain new measurements with respect to arbitrary antenna orientations, a multicomponent
antenna system can be utilized. Figures 12A-12B show examples of
antenna designs to achieve such purpose. The tool must be equipped wish at
20 least one tilted transmitter and two tilted receivers, or one tilted receiver and two
tilted transmitters, where the two antennas (either transmitters or receivers in
Figures 12A-12B) are located at the same position, with same distance (S) to She
third antenna. Thus, one of the two antennas that are placed at the same position
in Figures 12A-12B can have an arbitrary tilted angle in any quadrants of Figure
25 12C, the other must have a tilted angle in the quadrant adjacent to the quadrant
in which the first antenna orientation, is, and the third antenna can be tilted at:
arbitrary angle. For example, if 0ri (or Qu) in Figures 12A-12B is in quadrant 1
of Figure 12C, 0,?. (or Oa) must be in either quadrant 2 or quadrant 4 of Figure
12C. In addition, Figures 13A-13C show more tool structures ShaS: having the
30 capacity to attain the same functionalities as the structures in Figures 12A-12B.
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It is noted that transmitters) and receiver(s) can he exchangeahle in both. Figures
12A-12B and Figures 13A-13C. In addition, Figures 14A-14C illustrate the
structures that are capable of acquiring compensated measurements with respect
to arbitrary transmitter(s) and receiver(s) orientations to achieve desired
5 resistivity measurements on the basis of the processing schemes discussed
herein,
A geosignal is also an important parameter to predict when the
measurement tool is approaching, leaving, or passing She boundary between
layers, F'igure 15 shows a configuration of a measurement tool structured to
10 provide deep azimuthal resistivity measurements that is available as a
commercial LWD tool, as an example. Figure 15 shows one spacing of 16
inches of antenna structures with non-tilted transmitters and 45° tilted receivers.
F'igure 16A shows compensated average phase resistivity responses from the
measurement tool of Figure 15 for two specific tilted receivers having tilt angles
15 of 85° and 65°. Hie compensated average phase resistivity of (he structure of
F'igure 15 is depicted by curve 1641, F'igure 16B shows a geosignal phase image
from the measurement tool of F'igure 15, with respect to the formation model of
F'igure 5 with the relative dip angle of 85°. The geosignal image for this case
was provided with respect: to the number of total bins per rotation being 32.
20 F'igure 16A shows that as the measurement tool approaches the first
boundary at TVD of 10 ft, at: around 9.3 ft, the geosignal shows significant
responses. Also, based on the positive and negative sign of the geosignal
azimuthal responses, it demonstrates that drilling is from a layer with lower
resistivity to a layer with higher resistivity. Consequently, at TVD of 9.3 ft, the
25 phase resistivity can be retrieved by adjusting the tilt angle of the central
receivers to 85° tilt angle using the techniques discussed herein. The new phase
resistivity reading is illustrated in F'igure 16 A by curve 1642. After passing the
first, boundary, She sign of the geosignal responses changes and predicts that, the
tool is now located in the layer with higher resistivity value. At: this moment, the
30 phase resistivity reading can be recalculated by 65° tilt angle receivers, indicated
in curve 1643, in the middle layer. While the measurement tool is passing the
second boundary at TVD of 20 ft, the sign of the geosignal responses changes
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WO 2014/120150 PCT/1JS2013/023826"
again and a new phase resistivity can be determined by 85° tilted receivers,
indicated in curve 1644, owing to expecting the new layer with lower resistivity
value on the basis of the sign changes of the geosignal azi.mut.hal responses.
Consequently, curve 1642, curve 1643, and curve 1644 of Figure 16Acati.be
5 combined to estimate resistivity reading very close to true formation models and
to effectively eliminate horn effects of phase resistivity reading, depicted in
curve 1641, of the measurement tool structured to provide deep azimuthal
resistivity measurements of Figure 15.
The tool arrangement in F'igure 15 includas the transmitters being non-
10 tilted in the geosignal application discussed above to determine an estimate of
true formation resistivity and to effectively eliminate horn effects. Geosignal
phase image and similar processing schemes to determine true formation
resistivity can he also achieved by both tilted transmitters and tilted receivers
with perpendicular arrangements between the transmitter(s) and the receiver(s).
15 Other arrangements may be used that can take advantage of the tilt angle
transformation scheme discussed herein.
Figure 17 shows a flowchart of an example embodiment of a processing
scheme to determine true formation resistivity. At: 1710, regular measurements
for average phase resistivity are performed using a physical measurement tool
20 structure downhole and average phase resistivity is calculated based on this tool
structure. At. 1720, corresponding geosignal responses are utilized. The
corresponding geosignal responses can include those generated from the
measurements relative to the tool structure. At 1730, these corresponding
geosignal responses are applied to determine formation models. These
25 formation models can include resistivity as a function of layer position. At
1740, a determination is made as to whether the measured rasistivity is true
formation resistivity or not based on. the utilization of the geosignal responses. If
the geosignal responses identify significant signals, there should be a boundary
nearby and the resistivity reading may not be accurate. Without: a boundary, the
30 geosignal responses are essentially zero. At 1750, if significant signals are
identified, an adjustment to antenna orientations is identified. At: 1760, the
identified adjustments to the antenna orientations can be processed to transform
18
WO 2014/120150 PCT/1JS2013/023826"
the measurement values from operation of the physical measurement tool
structure to measurement values corresponding to the adjustments to the antenna
orientations and to recalculate the average phase resistivity. The adjustment
using geosignal responses may be directed to a best antenna orientation from
5 stored data or may be an iterative process. At 1770, a determination of a true
formation resistivity is made based on the use of the geosignal responses. Thus,
the processing scheme can use recalculation of new average phase resistivity
readings associated with specific antenna orientations based on geosignal
responses. At the end, this processing scheme can obtain accurate resistivity
10 measurements and avoid polarization horn effects.
Figure 18 shows a flowchart of an example embodiment of a processing
scheme to determine true formation resistivity. At 1810, raw measurements are
acquired from a measurement tool operating in a borehole with an arrangement
of antennas. At 1820, multiple antenna orientations are applied to the raw
15 measurements. These multiple antenna orientations can he used to transform the
raw measurements to new measurements in accordance with techniquas
discussed herein. At 1830, various average phase resistivities are calculated
corresponding to the multiple antenna orientations to obtain several average
phase resistivity measurements. At 1840, a determination can he made as to
20 whether these average phase resistivity measurements provide an estimate of a
true formation resistivity. If no boundary effect exists, all the phase resistivity
measurements should he identical, meaning the phase resistivity measurements
estimate true formation resistivity. However, if differences exist among the
phase resistivity measurements associated with distinct antenna orientations,
25 standard Geosignal responses are be included, at 1850, to determine a proper
resistivity reading for determination of true formation resistivity at 1860.
Various transformation techniques to provide new measurement values
from raw measurements similar to or identical to techniques discussed herein can
be applicable to different processing schemes. Such combinations of
30 transformation techniques and processing schemes can provide very fast and
simple methodology to significantly reduce or eliminate horn, effects and directly
detect Srue formation resistivity. In addition, such combinations can be used to
19
WO 2014/120150 PCT/1JS2013/023826"
attain a resistivity value that can be applied as an initial guess of 1D inversion,
and afterward perform inversion to optimize the inverted formation geology.
Techniques discussed above are basically used during horizontal and
deviated drilling. In. vertical drilling with 0° relative dip angle, Shese techniques
5 are not able to adjust antenna orientations as described above. Figure 19A
shows compensated average phase measurements of the tool structure in Figure
6 with various orientations of the transmitters and the receivers in formation
model of Figure 5 wish relative dip angle of 0°. Figure 19B shows compensated
average attenuation resistivity measurements of the tool structure in Figure 6
10 with various orientations of the transmitters and the receivers in formation model
of Figure 5 with relative dip angle of 0°. The various orientations included nontilted
transmitters with receivers tilted at 5°, 25°, 45°, 65°, and 85° and tilted
orientation pairs of (0„ 9r) = (45°, 45°), (25°, 65°), and (5°, 85°). However,
Figures 19A-19B each essentially show two curves (curves 1941 and 1943
15 corresponding to non-tilted transmitter arrangements and curves 1942 and 1944
corresponding to tilted transmitter arrangements), since the results for all
orientations with non-titled transmitters have assentially the same responses and
the results for all orientations with both tilted transmitters and receivers have
essentially identical results.
20 For the cases with non-tilted transmitters corresponding to drilling in a
vertical well with 0° relative dip angle, the coupling component of y^-" will be
null and thereby the received signal in equation (7) is revised as
V^(i)=Vli'Acos0l_ ,i=1.2 N (11)
Since the resistivity measurement is calculated by She ratio between, the signals
25 at the central receivers with one firing of the two transmitters in Figure 6, the
ratio signal can be expressed as
vl""* (0 v T""R''- cos $ v T,"!R''-
Therefore, equation (12) explains that the tilt angle of the receivers have no
impact on the average resistivity measurements. On the other hand, for the cases
30 with bosh tilted transmitters and tilted receivers corresponding to drilling in She
20
WO 2014/120150 PCT/1JS2013/023826"
vertical well, all She cross-coupling components
(v'^'-",y^A', yTjA ^y£,A ^ yW- ^ m $ ^ ^ j a r e nujj m(\ the directcoupling
components of V'J1""^""i and V^™^"^ are the same. Consequently,
received signal in equation (1.0) can be modified as
5 yWi")=— £— , / = ]., 2 A' (13)
It can be seen that tools with any tilt angle of transmitters and receivers will have
the same received signals during vertical drilling with very low relative dip
angle. It is noted that resistivity polarization horn effects do not exist: in vertical
drilling (0° relative dip angle) so thai: conventional resistivity measurements can
10 be directly used for geology interpretation and/or ID formation inversion in
vertical drilling (0° relative dip angle) applications. Thus, the embodiments of
processing techniques described herein need not be applied for a vertical drilling
(0° relative dip angle) operation.
All methods mentioned above are implemented by virtually adjusting
15 antenna orientations to eliminate resistivity polarization horn effects in the new
measurements. On the other hand, the methods can also be implemented by
physically adjusting antenna orientations to attain the same results. For the
physical adjustment of antenna orientations, She control unit 115 in Figure 1 can
be operable to assign the desired antenna orientation to a particular transmitter or
20 receiver sensor such that the sensor can be physically orientated. Then the
processing unit 120 in F'igure 1 can thereafter acquire the real measurements
from the new physically orientated transmitter and receiver sensors.
In various embodiments, useful processing schemes are provided to
eliminate resistivity polarization horn effects and further determine true
25 formation resistivity. These processing schemes can be implemented using
azimuthal LWD propagation wave tools. These processing schemes can provide
simple and fast techniques to understand formation geology and directly
compute true formation resistivity without ID inversion, which may provide an
enhancement, over approaches in which resistivity horn effects often occur
30 during horizontal drilling accompanied by misinterpretation of formation
geology if a 1D inversion is not. performed. Such technologies are applicable to
21
WO 2014/120150 PCT/1JS2013/023826"
a number of different commercial tools. In addition, using such processing
schemes may he beneficial for field operations in which 1D inversion results
may be improved and related real-time applications may be optimized, such as
distance to bed boundary inversion (DTBB).
5 Figure 20 shows features of an embodiment of an example method to
determine true formation resistivity. At 2010, measurement values are acquired
from operating a measurement tool in a borehole. The measurement tool
obtaining the measurement values has an arrangement of transmitter and receiver
antennas. Acquiring measurement values can include acquiring values from
10 making measurements during a rotation of the measurement tool, the rotation of
the measurement tool partitioned into N bins, in which completion of the N bins
is one complete rotation of the measurement tool, N > 2, where A7 is the total
number of bins.
At 2020, new measurement values are generated for a modified
15 aiTaogement. The modified arrangement may be a virtual arrangement. The
modified arrangement: has the same transmitter and receiver antennas as the
arrangement with the orientation of transmitter antennas, receiver antennas, or
both the transmitter and receiver antennas adjusted from the orientation of the
arrangement. The new measurement values can be generated by processing the
20 measurement values from operating the measurement tool using a relationship
including the tilt angle of a receiver antenna in the arrangement: and the tilt angle
of the same receiver antenna in the modilied arrangement:, where the tilt angle of
the receiver antenna in the arrangement is different from the tilt angle of the
same receiver antenna in the modified arrangement. Generating new
25 measurement values can include generating V^'"1 (/} according to
V^\i) = V^(i)x^f^ + lfy^(0xSiDi^~9^ , i = l, 2,...,A-
*M • *M • sin0ri Nfc *M si.n.(2<9„)
for the arrangement having at: least two or more receiver antennas and at: least
one or more transmitter antennas, where l)fiii indicates different transmitters and
RM indicates different receivers, Vl™ (i) is the signal measured at receiver R^,
30 in response to a signal being transmitted from transmitter Tina; m bin /, i=\ . . .
99
WO 2014/120150 PCT/1JS2013/023826"
N, and Vh"" (/} is the new measurement value for the reeeiver antenna /?,-„,/ at tilt
angle 9& in the modified arrangement with the reeeiver antenna Rirlj at tilt angle
&ti in the arrangement: at: which iihe measurement values from operating the
measurement tool are acquired. The transmitters can be non-tilted in. the
5 arrangement and in the modified arrangement. The transmitters can be tilted in
the arrangement sueh that the transmitters are perpendicular to the receivers.
Generating new measurement values can include determining coupling
components to calculate V^(i) from which Vl'"" (i) is generated. The
arrangement, can include at least one or more transmitters or at least two or more
10 receivers arranged such that: separation between each transmitter and each
receiver is at: a fixed distance
At 2030, the new measurements are used to determine an estimate of a
true formation resistivity. The estimate of the true formation resistivity can he
used as an initial guess in a one-dimensional or multi-dimensional inversion
15 procedure such that an inverted geology formation is optimized. The method
can he conducted in real time. In an embodiment, a method associated with
Figure 20 can include physically adjusting the arrangement, of the transmitter and
the receiver antennas to form new oriented transmitter and receiver antennas;
obtaining measurements from the new oriented transmitter and receiver
20 antennas; and using the new measurements to determine the estimate of a true
formation resistivity.
Figure 21 shows features of an embodiment of an example method to
determine true formation resistivity. At 2110, measurement values are acquired
from operating a measurement tool in a borehole. The measurement tool
25 obtaining the measurement values has an arrangement of transmitter and receiver
antennas. Acquiring measurement values can include acquiring values from
making measurements during a rotation of the measurement tool, the rotation of
the measurement tool partitioned into N bins, in which completion of the N bins
is one complete rotation of the measurement tool, N > 2, where A7 is the total
30 number of bins. At. 2120, an average phase resistivity is determined from the
measurement values.
WO 2014/120150 PCT/1JS2013/023826"
At 2130, a determination is made as to whether the average phase
resistivity corresponds to a true formation resistivity. Determining whether the
average phase resistivity corresponds to a true formation, resistivity can include
determining whether the measurement tool is near a boundary when acquiring
5 the measurement values, Geosignals can he generated from operating the
measurement tool in the borehole and the geosignals can be used to determine
whether the measurement: tool is near a boundary when acquiring the
measurement: values.
At 2140, the average phase resistivity can be reevaluated with respect to
10 a different: tilt angle of a receiver in the antenna arrangement using the
measurement values. The reevaluation can be based on the determination
regarding true formation, resistivity. Reevaluating the average phase resistivity
can include transforming the acquired measurement values such that a signal
corresponding to a signal at the receiver having a tilt angle in the arrangement
15 from transmitting a signal from a transmitter in the arrangement is converted to a
signal at the receiver having a different tilt angle. Transforming the acquired
measurement values can include adjusting the acquired measurement values with
respect: to coupling components. The reevaluated average phase resistivity can
be used as an initial guess in a one-dimensional or multi-dimensional inversion
20 procedure such that an inverted geology formation is optimized. The method
can be conducted in real time.
Reevaluating the average phase resistivity with respect to a different tilt
angle of a receiver in the original antenna arrangement using the measurement
values can include a physical adjustment to the arrangement. In an embodiment,
25 a method can include acquiring measurement: values from operating a
measurement tool in a borehole, the measurement tool having an antenna
arrangement:; determining an average phase resistivity from the measurement
values; determining whether the average phase resistivity corresponds to a true
formation resistivity; physically adjusting the arrangement of the transmitter and
30 the receiver antennas, forming new oriented transmitter and receiver antennas;
obtaining measurements from the new oriented transmitter and receiver
antennas; and using the new measurements to evaluate the average phase
24
WO 2014/120150 PCT/1JS2013/023826"
resistivity. The average phase resistivity from new measurements can be used as
an initial guess in a one-dimensional or multi-dimensional inversion procedure
such that an inverted geology formation is optimized. The method can be
conducted in real time.
5 Figure 22 shows features of an embodiment of an example method to
determine true formation resistivity. At 2210, measurement values are acquired
from operating a measurement tool in. a borehole. The measurement tool
obtaining the measurement values has an arrangement of transmitter and receiver
antennas. Acquiring measurement values can include acquiring values from
10 making measurements during a rotation of the measurement tool, the rotation of
the measurement tool partitioned into N bins, in which completion of the N bins
is one complete rotation of the measurement tool, N > 2, where A7 is the total
number of bins.
At 2220, an average phase resistivity is calculated from the measurement
15 values. At 2230, geosignal responses are used to determine whether the
measurement tool is near a boundary.
At 2240, antenna orientations are adjusted to specific antenna
orientations based on the geosignal responses. Adjusting to specific antenna
orientations can be conducted virtually or physically. The specific antenna
20 orientations can be at least: in part different from antenna orientations of the
antenna arrangement:. The antenna arrangement can include at least: one or more
non-tilted transmitters and at: least two or more receivers having a same tilt: angle
and the specific antenna orientations have the at least two or more receivers with
a tilt: angle different from the tilt angle of the antenna arrangement. The antenna
25 arrangement can include at least: one or more tilted transmitters arranged
perpendicular to at least two or more receivers having a same tilt angle and the
specific antenna orientations have the receivers with a tilt angle different from
the tilt: angle of the antenna arrangement. A voltage signal can be determined at
one receiver of the receivers in response to one of the transmitters generating a
30 signal in the antenna arrangement and the voltage signal is transformed to a new
voltage signal of the one receiver by processing based on the same tilt angle and
a tilt angle of the specific orientation that is different from the same tilt angle.
WO 2014/120150 PCT/1JS2013/023826"
At 2250, a new average phase resistivity is recalculated with respect to
the specific antenna orientations to estimate a true formation resistivity. The
recalculated new average phase resistivity can be used as an initial guess in. a
one-dimensional or multi-dimensional inversion procedure such thai: an inverted
5 geology formation is optimized. The method can be conducted in real time,
Figure 23 shows features of an embodiment of an example method to
determine true formation resistivity. At 2310, measurement values are acquired
from, operating a measurement tool in a borehole. The measurement tool
obtaining the measurement values has an arrangement of transmitter and receiver
10 antennas. Acquiring measurement values can include acquiring values from
making measurements during a rotation of the measurement tool, the rotation of
the measurement tool partitioned into N bins, in. which completion of the N bins
is one complete rotation of the measurement tool, N > 2, where N is the total
number of bins.
15 At 2320, an average phase resistivity is calculated from the measurement
values for each of a plurality of antenna orientations. The plurality of antenna
orientations can include the antenna arrangement.
At 2330, the average phase resistivities can be compared to determine if
the average phase resistivities estimate a true formation resistivity. Comparing
20 the average phase resistivities can include determining if magnitudes of
respective differences between the average phase resistivities are greater than a
threshold. The threshold can be set to zero. However, noise and imperfections
can cause the threshold to be non-zero. To take such small variances into
consideration, the threshold can be an error amount greater than zero.
25 At 2340, geosignal responses are used to determine a reading
corresponding to the true formation resistivity, if the comparison does not
identify an estimate of the true formation resistivity. The reading corresponding
to the true formation resistivity can be used as an initial guess in. a onedimensional
or multi-dimensional inversion procedure such that an inverted
30 geology formation is optimized. The method can be conducted in real time.
In various embodiments, sets of measurement values from operating a
measurement tool downhole can be processed as the measurement tool moves in
26
WO 2014/120150 PCT/1JS2013/023826"
the borehole. Processing of the measurement values can include determining
values for formation resistivity and generating geosignals, The geosignals
provide an indication that the measurement is moving near a boundary between
formation layers. When the presence of the boundary is determined, the
5 measurement values can be transformed to measurement values corresponding to
antenna orientations of the measurement tool that reduce or eliminate the horn
effect associated with the downhole measurement values. The resistivity can be
recalculated for the transformed measurement corresponding to a tilt angle
adjusted from that of the measurement based on the geosignal response. For
10 each boundary encountered in the movement of the measurement tool, two or
more recalculations can be performed; at least one approaching the boundary and
at least one leaving the boundary. The multiple recalculations can be attributed
to measurement values being related to different tilt angles of the antennas of the
measurement tool on. the diflerent sides of the boundary between formation
15 layers of different resistivity for compensation of the horn effect. The selection
of the adjusted tilt angle may be an iterative process using the geosignal
responses. These processes can be conducted real time to determine the true
formation resistivity. In addition, processes to determine the true formation
resistivity may include features of different embodiments discussed herein,
20 In various embodiments, a machine-read able storage device can be
structured having instructions stored thereon, which, when performed by a
machine, cause the machine to perform operations that include using a processor
and processing unit structured to process measurement values acquired from a
measurement tool operating downhole to determine a true formation resistivity,
25 The measurement tool has arrangement of transmitter antennas and receiver
antennas structured similar to or identical to any of the arrangements of
transmitters and receivers discussed herein. The processor and processing unit
can be coupled to measurement tool operating in the borehole. The operations
performed from executing instructions can include, but are not limited to,
30 determining resistivity from measurement values, generating geosignals,
determining adjustment tilt angles for the measurement tool, transforming the
measurement values to new measurement values based on She adjusted tilt
27
WO 2014/120150 PCT/1JS2013/023826"
angles, determining the presence of nearby boundaries operations, determining
whether a resistivity is a true formation resistivity, and conducting procedures to
detemrine an estimate of the true formation resistivity. The instructions can be
executed to perforin operations in a manner identical to or similar to processes
5 discussed in herein. The instructions ean be executed in conjunction with a
control unit to control the firing of selected transmitters and/or receivers and
collection of signals at selected receivers and/or transmitters (in view of
reciprocity) in a manner similar to or identical to operations associated with
methods discussed herein. Further, a machine-readable storage device, herein, is
10 a physical device that stores data represented by physical structure within the
device. Examples of machine-readable storage devices include, hut are not
limited to, read only memory (ROM), random access memory (RAM), magnetic
disk storage device, optical storage device, Hash memory, and other electronic,
magnetic, and/or optical memory devices.
15 In various embodiments, a system comprises a measurement tool having
one or more transmitters and one or more receivers in an antenna arrangement; a
control unit operable to generate signals and collect signals in the antenna
arrangement; and a processing unit to control and process measurement values
from operating the measurement tool. The measurement tool, the control unit,
20 and the processing unit are configured to operate to perform features of methods
similar to or identical to features associated with methods discussed herein. The
one or more transmitters and the one or more receivers can be realized as
transceivers, The control unit is operable to manage selective generation of
signals from transceivers and to manage selective collection of received signals
25 at transceivers. The control unit and the processing unit can be structured as
separate units or as an integrated unit. The control unit and the processing unit
can be separate or integrated with the measurement tool.
Figure 24 depicts a block diagram of features of an example system
operable to determine true formation resistivity. System 24(X) includes a tool
30 2405 having an arrangement of transmitters 2410-1 and receivers 2410-2
operable in a borehole. The arrangements of the transmitters 2410-1 and the
receivers 2410-2 of the tool 2405 can be realized similar to or identical to
28
WO 2014/120150 PCT/1JS2013/023826"
arrangements discussed herein. The system 24(X) can also include a controller
2415, a memory 2442, an electronic apparatus 2443, and a communications unit
2445. The controller 2415 and the memory 2442 can be arranged to operate the
tool 2405 to acquire measurement data as the tool 2405 is operated and to assign
5 the acquired data to a number of bins, each correlated to an azimuthal angle in a
rotation of the tool 2405. The controller 2415 and the memory 2442 can be
realized to control activation of selected ones of the transmitter antennas 2410-1
and data acquisition by selected one of the receiver antennas 2410-2 in the tool
2405 and to manage processing schemes to determine a true formation resistivity
10 in accordance with measurement procedures and signal processing as described
herein. Processing unit 2420 can be structured to perform the operations to
manage processing schemes to determine a true formation resistivity in
accordance with measurement procedures and signal processing in a manner
similar to or identical to embodiments described herein.
15 Electronic apparatus 2443 can be used in conjunction with the controller
2415 to perform tasks associated with taking measurements downhole with the
transmitters 2410-1 and the receivers 2410-2 of the tool 2405. Communications
unit: 2445 can include downhole communications in a drilling operation. Such
downhole communications can include a telemetry system.
20 The system 24(X) can also include a bus 2447, where the bus 2447
provides electrical conductivity among the components of the system 2400. The
bus 2447 can include an address bus, a data bus, and a control bus, each
independently configured. The bus 2447 can also use common conductive lines
for providing one or more of address, data, or control, the use of which can be
25 regulated by the controller 2441. The bus 2447 can be configured such that: the
components of the system 2400 are distributed. Such distribution can be
arranged between, downhole components such as the transmitters 2410-1 and the
receivers 2410-2 of the tool 2405 and components that can be disposed on the
surface of a well. Alternatively, the components can be co-located such as on
30 one or more collars of a drill string or on a wireline structure.
In various embodiments, peripheral devices 2446 can include displays,
additional storage memory, and/or other control devices that may operate in
29
WO 2014/120150 PCT/1JS2013/023826"
conjunction with the controller 2441 and/or the memory 2442. In an
embodiment, the controller 2415 can be realized as one or more processors. The
peripheral devices 2446 can be arranged with a display with instructions stored
in the memory 2442 to implement a user interface to manage She operation of the
5 tool 2405 and/or components distributed within the system 2400. Such a user
interface can be operated in conjunction with the communications unit 2445 and
the bus 2447. Various components of the system 2400 can be integrated with
the tool 2405 such that processing identical to or similar to the processing
schemes discussed with respect to various embodiments herein can be performed
10 downhole in the vicinity of the measurement or at the surface.
Figure 25 depicts an embodiment of a system 2500 at a drilling site,
where the system 25(K) includes an apparatus operable to determine true
formation resistivity. The system 2500 can include a tool 2505-1, 2505-2, or
both 2505-1 and 2505-2 having an arrangement: of transmitter antennas and
15 receiver antennas operable to make measurements that can be used for a number
of drilling tasks including, but not. limited to, determining resistivity of a
formation. The tools 2505-1 and 2505-2 can be structured identical to or similar
to a tool architecture or combinations of tool architectures discussed herein,
including control units and processing units operable to perform processing
20 schemes in a manner identical to or similar to processing techniques discussed
herein. The tools 2505-1, 2505-2, or both 2505-1 and 2505-2 can. be distributed
among the components of system 2500. The tools 2505-1 and 2505-2 can be
realized in a similar or identical manner to arrangements of control units,
transmitters, receivers, and processing units discussed herein. The tools 2505-1
25 and 2505-2 can be structured, fabricated, and calibrated in. accordance with
various embodiments as taught herein.
The system 25(K) can include a drilling rig 2502 located at a surface 2504
of a well 2506 and a string of drill pipes, that is, drill string 2529, connected
together so as to form a drilling string that: is lowered through a rotary table 2507
30 into a wellbore or borehole 2512-1. The drilling rig 2502 can provide support
for the drill string 2529. The drill string 2529 can operate to penetrate rotary
table 2507 for drilling the borehole 2512-1 through subsurface formations 2514.
30
WO 2014/120150 PCT/1JS2013/023826"
The drill siring 2529 can include a drill pipe 2518 and a bottom hole assembly
2520 loeated at the lower portion of the drill pipe 2518.
The bottom hole assembly 2520 can include a drill collar 2516 and a drill
bit: 2526. The drill bit 2526 can operate to crease She borehole 2512-1 by
5 penetrating the surface 2504 and the subsurface formations 2514. The bottom
hole assembly 2520 ean include the tool 2505-1 attached to the drill collar 2516
to conduct: measurements to determine formation parameters. The f:ool 2505-1
can be structured for an implementation, as a MWD system such as a LWD
system. The housing containing the tool 2505-1 can include electronics to
10 initiate measurements from selected transmitter antennas and to collect
measurement signals from selected receiver antennas. Such electronics can
include a processing unit: to provide analysis of formation parameters over a
standard communication mechanism for operating in a well. The analysis may
include an analysis of an estimate of the true formation resistivity for each
15 formation layer investigated. Alternatively, electronics can include a
communications interface to provide measurement signals collected by the tool
2505-1 to the surface over a standard communication mechanism for operating
in a well, where these measurements signals can be analyzed at a processing unit:
at the surface to provide analysis of formation parameters, including an estimate
20 of the true formation resistivity for each formation layer investigated.
During drilling operations, the drill string 2529 can be rotated by the
rotary table 2507. In addition to, or alternatively, the bottom hole assembly
2520 can also be rotated by a motor (e.g., a mud motor) that is located downhole.
The drill collars 2516 can be used to add weight to the drill bit 2526. The drill
25 collars 2516 also can stiffen the bottom hole assembly 2520 to allow the bottom
hole assembly 2520 to transfer the added weight to the drill bit 2526, and in turn,
assist the drill bit: 2526 in penetrating the surface 2504 and the subsurface
formations 2514.
During drilling operations, a mud pump 2532 can pump drilling fluid
30 (sometimes known by those of skill in the ait as "drilling mud") from a mud pit
2534 through a hose 2536 into the drill pipe 2518 and down to the drill bit: 2526.
The drilling fluid can flow out from the drill bit: 2526 and be returned to She
31
WO 2014/120150 PCT/1JS2013/023826"
surface 2504 through an annular area 2540 between the drill pipe 2518 and She
sides of the borehole 2512-1. The drilling fiuid may then be returned to the mud
pit 2534, where such fluid is filtered. In some embodiments, the drilling fluid
can be used to cool the drill bit 2526, as well as to provide lubrication for the
5 drill bit 2526 during drilling operations. Additionally, the drilling fiuid may be
used to remove subsurfaee formation cuttings created by operating the drill bit
2526.
In various embodiments, the tool 2505-2 may be included in a tool tody
2570 coupled to a logging cable 2574 such as, for example, for wireline
10 applications. The tool body 2570 containing the tool 2505-2 can include
electronics to initiate measurements from selected transmitter antennas and to
collect measurement signals from selected receiver antennas. Such electronics
can include a processing unit to provide analysis of formation parameters over a
standard communication mechanism for operating in a well. The analysis may
15 include an analysis of an estimate of the true formation resistivity for each
formation layer investigated. Alternatively, electronics can include a
communications interface to provide measurement signals collected by the tool
2505-2 to the surface over a standard communication mechanism for operating
in a well, where these measurements signals can be analyzed at a processing unit
20 at the surface to provide analysis of formation parameters, including an estimate
of the true formation resistivity for each formation layer investigated. The
logging cable 2574 may be realized as a wireline (multiple power and
communication lines), a mono-cable (a single conductor), and/or a slick-line (no
conductors for power or communications), or other appropriate structure for use
25 in the borehole 2512. Though Figure 25 depicts both an arrangement for
wireline applications and an arrangement for LWD applications, the system 25(X)
may be also realized for one of the two applications.
Although specific embodiments have been illustrated and described
herein, it will be appreciated by (hose of ordinary skill in the art that any
30 arrangement that is calculated to achieve the same purpose may be substituted
for the specific embodiments shown. Various embodiments use permutations
and/or combinations of embodiments described herein. It is to be understood
'"*'")
jZ
WO 2014/120150 PCT/1JS2013/023826
thai: the above description is intended to be illustrative, and not restrictive, and
that the phraseology or terminology employed herein is for the purpose of
description. Combinations of iJie above embodiments and other embodiments
will be apparent to those of skill in the art: upon studying the above description

CLAIMS
1. A method comprising:
5 acquiringraeaOTrementvalujfroinopaatmgairieasiireiment toolm a
borehole, the measurement tool having an arrangement of transmitter and
receiver antennas;
generating new measurement values for a modified arrangement of the
same iransmi tter and receiver antennas by processing tin measurement values
10 from operating the measurement tool using a relationship including a tilt angle of
u receiver antenna in the arrangement that is different from a tilt angle of the
same receiver antenna in the modified arrangement; and
using die new measurements to determine an estimate of a true formation
resi.wvuy.
IS
20
2. The method of claim 1, wherein acquiring measurement values includes
acquiriog values from maJong measurements daring a rotation of the
measurement tool, the natation of the measurement tool partitioned into 14 bins,
in which completion Of the N bins is one eomplote rotation of the measurement
tool, N > 2, where AT is the total number of bin?, and generating new
measurement values includes generating Vjg (i) according to
*-. *«w ^^ Nft *" ' sin(2^.r)
for the arrangement having ut least two or more receiver antennas and at least
one or more transmitter antennas, where Tw indicates different transmitters and
25 HM indicates different receivers, v£j (i) is the signal measured at receiver RM,
in response to a signal being transmitied from transmitter 7"/^, m bin /, 1=1...
4
N, and v£f {/) is the new measurement value for the receiver antenna /&* at tilt
angle Gta in the modified arrangement with thn receiver antenna KimtOL tilt angle
$,\ in die avrangement at which die measurement values from operating the
30 measurement tool are acquired.
I
3. The method of ctehn 2, wherein the transmitters are non lilted in the
arrangement and in the modified arrangement.
5 4. The method ofclaUn 2, whweintbe transmitters fie tilted In tiw
arrangement such that the transmitters are perpendicular to the receivers.
5- Tl» method of claim 4, wherein generating new measurement values
includes determining coupling components to calculate v£ (/) fiom which
* •
10 v^ (i) is generated.
6. The method of claim 1, wherein the arrangement inclndca at least one or
more transmitters or at least two or more receivers arranged such that separation
between each transmitter and each receiver is at a fixed distance.
15
7. The method of claim 1, wherein the method includes osing the estimate
of the true formation resistivity as aa initial guess in a. one-dimensional or multidimensional
inversion procedure each that an inverted geology formation is
optimized.
20
8. The method of claim 1. wherein the method includes
physically adjusting the arrangement of the transmitter and the receiver
antennas to form new oriented transmitter and receiver antennas;
obtaining measurements from the new oriented transmitter tmi receives
25 antennas; and
using the new measurements to determine the estimate of a ime
formation resistivity.
9. A method comprising:
30 acquiring measurement values from operating a measurement too) In a
borehole, the measurement tool having an uitemm arrangement;
determining an average phase resistivity from the measurement values;
35
determining whether the average phase resistivity corresponds lo a true
formation resistivity, and
reevaluating the average phase resistivity with respect TO a different till
angle of a receiver in tbe antenna arrangement using the measurement values.
5
10. The method of claim 9, wherein determining whether the average phase
resistivity corresponds to a true formation resistivity includes determining
whether the measurement tool is near a boundary when acquiring the
measurement values.
10
11. The method of claim. 10, wherein the method includes generating
geosignals from operating die measurement tool in the borehole and using the
geosignals to determine wbether the measurement tool is near a boundary when
acquiring the measurement values.
15
12. The method of claim 9, wherein reevaluating the average phase
resistivity includes transforming the acquired measurement values such ihat a
signal corresponding to a signal at the receiver having a tilt angle in the
arrangement from transmitting a signal from a transmitter in tt» arrangement is
20 converted to a signal at the receiver having a different tilt angl e.
13. The method of claim 9, wherein transforming the acquired measurement
values includes adjusting the acquired measurement values with respect to
coupling components.
14. The method of claim 9, wherein the method includes using the
reevaluated average phase resistivity as an initial guess in a ono-dimensional or
multi-dimensional inversion procedure such dial an inverted geology formation
is optimized.
30
12. A method comprising;
acquiring measurement values from operating a measurement tool in a
36
borehole, toe measurement tool having an antenna arrangement;
determining an average pHase resistivity from the measurement values;
determining whether the average phase resistivity corresponds to a true
formation resistivity;
5 physically adjusting the arrangement of the transmitter and flic receiver
antennas, forming pew oriented transmitted and receiver antenna$;
obtaining measurements tram die new oriented transmitter and receiver
antennas; and
using the new measurements to evaluate the average phase resistivity.
10
16. A method comprising:
acquiring measurement values fro*u Operating a measurement tool in a
borehole. Hie measurement tool having an antenna arrangement;
calculating an average phase resistivity from the measurement values;
15 using geosigna} responses to determine whether the measurement tool Is
near a boundary average;
adj osting antenna orientations virmaUy or physically to specific antenna
Orientations based on the geosigna] responses, the specific antenna orientations
being at least in pare different from antenna orientations of tbe antenna
20 arrangement, and
recalculating a new average phase resistivity with respect to die specific
antenna orientations to estimate a true formation resistivity.
17. The method of claim 16, wherein the antenna arrangement iodudes at
25 least one or more non-tilted transmitters and at least vuo or more receivers
having a same tilt angle and the specific antenna orientations have the at least
two or more receivers with a bit angle different from the tilt angle of the antenna
arrangement.
30 18. The method of claim 16, wherein the antenna arrangement includes ax
least one or more tilted transmitters arranged perpendicular to at least two or
more receivers having a same tilt angle and the specific antenna orientations
have the receivers with a sit angle different from (he tilt angle of die antenna
arrangement
5 19. The method of claim 17 or 18, wherein a voltage signal is determined at
one receiver of tbe receivers in response to one of the transmitters generating a
signal in tbe antenna arrangement and the voltage signal is transformed to a new
voltage signal of tbe one receiver by processing based on tbe same tilt angle and
a tilt angle of tbe specific orientation that is different from the same till angle.
10
20. The method of claim 16, wherein the method includes using the
recalculated new average phase resistivity as an initial guess in n onedimensional
or muM-dimensional inversion procedure such that an inverted
geology ftaatwn Is opthnized,
15
21. A method comprising:
acquiring measurement values from operating a measurement tool in a
borehole, the measurement tool having an antenna arrangement;
calculating an average phase resistivity from rhe measurement values for
20 each of a plurality of amentia orientations, tbe plurality of antenna orientations
including the antenna arrangement;
cornparing the average phase resistivities to determine if the average
phase resistivities estimate a true formatjoa resistivity; and
using geosignal responses to determine a reading corresponding to the
25 true formation resistivity, if the comparison does not Identify an estimate of the
true formation resistivity.
22. The method of el aim 21, wherein comparing the average phuse
resistivities includes determining if magnitudes of respective differences
30 between tbe average phase resistivities are greater than a threshold.
23. The method o f claim 22, wherein the threshold is zero or an error anaorat
greater torn zero.
24. The method of claim 2 i , wherein the method Includes using the reading
5 cone^oB)ingtoihetiuefonrAtio«reastivityasaiiinitialgucssinaonedimcnsional
or mutri-dhnensional inversion procedure such that an inverted
geology formation is optimized.
25. The method of claims 1,9.15,16, or 21, wherein the method is
10 conducted in real time.
26. A machine-readable storage device having instructions stored tbereon,
which, when performed by a machine, cause the machine to perfoim operations,
the operations comprising:
15 acquiring measurement values from operating a measurement tool in a
borehole, the ms&sawment cool having an arrangement of transmitter and
receiver antennas;
generating new measurement values for a modified arrangement of the
same transmitter and receiver antennas by processing the measurement values
20 from operating the measurement too! using a relationship including a tilt angle of
a receiver antenna in the arrangement that is different from a tilt angle of the
same receiver antenna in the modified arrangement; and
nsing the new measurements to determine an estimate of a true formation
resistivity.
25
27. A system comprising:
a measurement tool having one or more transmitters and one or more
receivers in an antenna arrangement;
a control unit operable to generate signals and col lea signtds in (he
30 antenna arrangement; and
a processing unit to control aid process measurement vulues from
operating the measurement tool, wherein the measurement tool, tbe control unit,
39
and the processing unit arc configured to:
acquire measurement: values from operating the measurement tool
in a borehole;
generate new measuieme it values for a modified arrangement of
the same transmitter and receive antennas by processing the
measurement values from operating the measurement tool using a
relationship including a dlt angle of a receiver antenna in the
arrangement, thai is different froi»adit angle of the same receiver
antenna In the modified arranger! icnt and
use the new measurement 9 to determine an estimate of a true
formation resistivity.
28. The system of claim 27. wherein to acquire measurement values includes
acquiring values firom making measurer* cuts during a rotation of the
measurement tool, the rotation of the me inurement tool partitioned into N bins,
in which completion of the N bins is one complete rotation of the measurement
tool, N > 2, where N is the total number of bins, and generating new
measurement values includes generating V£ ©Bccoriinsto
^'w-v£mxffi+j;±vz generate new measurement vajoes
indndes detenninmg coupling components xo calculate v£<£) ftom which
V ^ ( 0 is generated.
10 32. Ilesystmiofelajm27,wheremthearr^6ementiiichide«atleascotwor
mors transmitters or at least two or more receivers arranged such that separation
between each transmitter and each receiver is at a fixed distance.
i
33. The system of claim 27, wherein the measurement tool, the control unit.
15 and the processing unit are configured to use The estimate of the true formation
resistivity as an initial guess m a one-dimensional or muM-dknensional
inversion procedure such that an inverted geology formation is optimized.
34. The system of claim 27, wherein the measurement too), the control unit,
20 aud me processugunbare configured to
physically adjust the arrangement of the transmitter nod me receiver
antennas to form new oriented transmitter and receiver antennas;
obtain measurements from the new oriented transmiUer and receiver
antennas; and
25 use the new measurements IO determine the estimate of a true formation
resistivity.
i
35. A system comprising:
a measurement tool having one or more transmitters and one or more
30 receive? in an antenna arrangement;
a control unit operable to generate signals and collect signals in the
antenna airanaeittAne and
a processing unit to control and process measurement values from
operating the measurement too), wherein tbc measurement tool, the control unit,
and the processing unit are configured lo:
acquire measurement values from operating the measurement tool
5 . ID a borehole;
determine an average phase resistivity Tram the measurement
values;
determine whether the average pbase resistivity corresponds to a
true formation resistivity; and
10 reevaluate the average phase resistivity with respect to a different
tilt angle of a receiver in the antenna arrangement using tbe measurement
values.
36. The system of claim 35, wherein to determine whether the average pbase
15 resistivity corresponds to a tme formation resistivity includes determining
whether the measurement tool is near a boundary when acquiring the
measurement values.
37. The system of claim 36, wherein the measurement tool, rhe control unit,
20 and the processing unit are configured lo generate geosignals from operating tbc
measurement tool in the borehole and using the geosignals io determine whether
the measurement tool is near a boundary when acquiring the measurement
values.
25 58. The system oF claim 35, wherein to reevaluate the average pbase
resistivity includes transforming the acquired measurement values such mat a
signal corresponding to a signal at tbe receiver having a tilt angle in the
arrangement from transmitting a signal from a transmitter in tho arrangement is
converted to a signal at toe receiver having a different lilt angle.
10
39- The system of claim 35, wherein, to transform the aequ ineU measurement
valu«s includes adjusting the acquired measurement values with respect to
coupling components.
40. The System of claim 35, wherein the measurement tool, the control unit,
and the pro cessing unit are configured to use the reevaj uated overage phage
resistivity as an initial guess in a one-dimensional or mold-dimcnsionnl
inversion procedure such ifeat an inverted geology formation fe optimized.
41. A system comprising:
a measurement tool having one or more transmitters and one or more
receivers in an antenna arrangement
a control unit operable to generate signals and eollect signals in the
15 antenna arrangement; and
a processing unic to control and process measurement values from
operating the measurement tool, wherein the-measurement tool, the control unit,
and the processing unit are configured to:
acquire measurement values Bom operating the measurement tool
20 in a borehole;
determine an average phase resistivity from the measurement
values;
determine whether the average phase resistivity corresponds to a
(rue formation resistivity;
25 physically adjust me arrangement of the transmitter and the
receiver antennas, forming new oriented transmitter and receiver
antennas;
obtain measurements from the new oriented transmitter and
receiver antennas; and
30 use the new measurements to evaluate the averagp phase
resistivity.
42. A system comprising:
a measurement tool having one or mote transmitters and one or more
receivers in an antenna arrangement;
5 a control unit operable to generate signals and collect signals in the
antenna arrangement; and
a processing unit to control and process measurement values from
operating the measurement tool, wherein ibe measurement tool, the control unit,
and the processing unit are configured lo:
10 acquire measurement values from operating the measurement tool
in a borehole;
calculate an avenge phase lesistlvby from ibe measurement
values;
use gcosignal responses to determine whether me measurement
15 tool is near a boundary average;
adjust antenna orientations virtually or physically to specific
antenna onerjizruocs based on the geosignal responses, the specific
antenna orientations being at least in part different from antenna
orientations of the antenna, arrangement, and
20 recalculate a new average phase resistivity with respect to the
specific antenna orientations to estimate a true formation resistivity.
43. The system of claim 42, wherein the antenna arrangement includes at
least one or more non-tilted transmitters and at Icust two or more receivers
25 having a same lift angle and uhe specific antenna orientations have the at least
TWO or more receivers with a bit angle different from the tilt angle of the antenna
arrangement
44. The system of claim 42, wherein the antenna arrangement includes at
least one or more lilted transmitters arranged perpendicular to at least two or
more receivers having a same bit angle and the specific antenna orientations
5 have, the receivers -with a lilt angle different from the tilt angle of the antenna
arrangement.
45. The system of claim 43 or 44, wherein the measurement tool, the control
unit, and tbe processing unit are configured such mat a voltage signal is
10 determined at one receiver of the receivers in response to one of the transmitters
generating a signal in me antenna arrangement and the voltage signal is
transformed to a new voliagc signal of me one receiver by processing based on
the same tilt angle and a tilt angle of tbe specific orientation tbat is different from
die same lit angle.
15
46: Tne system of claim 42, wherein me measurement tool, the control unit,
and the- processing unit axe configured to use tbe recalculated new average phase
resistivity as an initial guess in a one-dimensional or multidimensional
Inversion procedure such that an inverted geologyformation is optimized,
20
47. A system comprising:
a measurement tool having one or more transmitters and one or more
receivers in an antenna arrangement;
a control unit operable to generate signals and collect signals In the
25 antenna arrangement; and
a processing unit to control and process measurer/tent valves from
operating the measurement tool, wherein the measurement tool, the control unit,
and the processing unit arc configured to:
acquire measurement values from operating the measurement tool
30 In a. borehole;
calculate an average phase resistivity from the measurement
values for each of a plurality of antenna orientations, the plurality of
antenna orientations including the antenna arrangement.;
compare the average phase resistivities 10 determine if the
5 average phase resistivities estimate a true formation resistivity; and
use geo$i£nal responses to determine a reading corresponding to
the true formation resistivity, if tho comparison does not identify an
estimate of the true formation resistivity.
10 48. The system of claim 47, wherein to compare the average phase
resistivities includes determirang if magnitudes of respective differences
between tho average phase resistivities am greater than a threshold.
49. The system of claim 48, whei^tlw threshold te zero or an ema-amoinit
15 greater than zero.
50. The system of claim 47, whenein the measurement tool, the control unit,
and the processing uiri t are configured to use the reading corresponding to die
true formation resistivity as an initial guess in a one-dimensional or multi-
20 dimensional inversion procedure such that an inverted geology formation Is
optimized.
51. The system of claims 27,35,41,42, or 47, wherein the measurement
tool, (he control unit, and the processing unit are configured to conduct
25 operations in real lime. •
i
52. The machine-readable storage device of claim 26, wherein acquiring
measurement values includes acquiring values from making measurements
during a rotation of the measurement tool, the rotation of the measurement tool
30 partitioned into N bins, in which completion of the N bins is one complete
rotation of the measurement tool. N > 2, where AT is the total number of bins,
mt
MA
and generating new measurement values includes generating Vj~ (/) according
to
for tho arrangement having at least two or more receiver antennas and at least
one or more transmitter antennas, where T!nt Indicates different transmitters and
Rind indicates different receivers, V^ (i) is tbe signal measured at receiver Rtmi,
in response to a signal being transmitted from transmitter 7f«rt in bin i, *vj . . .
N, and Vjfc (0 is the new measurement value for tbe receiver antenna AM HI tile
angle fti in the modified arrangement with tho receiver antenna R&i at till angle
$rt In the arrangement at which the measurement values from operating the
measurement tool are acquired
53. The machine-readable storage device of claim 52, wherein the
transmitters are non-tilted in the arrangement and in the modified arrangement
54. The machine-readable storage device of claim 52, wherein the
transmitters are tilted in the arrangement Such that the transmitters are
perpendicular to the receivers.
55. The machine-readable storage device of claim 54, wherein generating
new measurement values includes determining coupling components to calculate
V£(i) from which V"£ (1) is generated.
56. The machine-readable storage device of claim 26, wherein the
arrangement includes at least one or more transmitters or at least WO or more
receivers arranged such that separation between each Transmitter and each
receiver is at a fixed distance.
57. The machine-readable storage device of claim 26, wherein the method
includes a sing the estimate of the trae formation resistivity as an initial guess in
A oner dimensional or multi-dimensional invasion procedure such that an
5 inverted ecology formation is optimized.
58. The machine-readable storage device of claim 26, wherein the method
includes
physically adjusting the arrangement of the transmitter and the receiver
10 antennas to form new oriemed transmitter and receiver antennas;
obtaining measurements from the new oriented transmitter and receiver
antennas; and
using the new measurements to determine the estiijwte of a true
formation resistivity.
15
59. A machine-readable storage device having mstructions stored thereon,
which, when performed by a machine, cause the machine to perform operations,
the operations comprising:
acquiring measurement values from operating a measurement tool in a
20 borehole, the measurement tool having an antenna arrangement;
determining an average phase resistivity from the measurement values;
determining whether the average phase resistivity corresponds to a true
formation resist) vjty; and
reevaluating the average phase resistivity with respect to a different tih
25 angle of a receiver in the antenna arrangement Wing the measurement values.
60. The machine-readable storage device of claim 59, wherein determining
whether the average phase resistivity corresponds to a true formation resifltivity
includes determining whether the measurement too) is near a boundary when
30 acquiring die measurement values.
<5I. The mathine-readable storage device of claim 60. wherein the method
includes generating geosignals from operating the measurement tool in the
borehole und using the gcosignals to determine whether tbe measurement tool is
5 near a boundary when acquiring the measurement values,
62. The macMne-readable storage device of claim 59, wherein reevaluating
the average phase resistivity includes transforming the acquired measurement
values such that a signal corresponding to a signal at the receiver having a tilt
10 angle in the arrangement from transmitting a signal from a transmitter in the
arrangement is converted to a signal at the receiver having a different Uit angle.
63. The machine-roaiiable storage device of claim 59, wherein transforming
the acquired measurement values includes adjusting tbe acquired measurement
15 values with respect to coupling components,
64. The machlAt-ieadable storage device of claim 59. wherein (lie method
includes using the reevaluated average phase resistivity as an initial guess in a
one-dimensional or multi-dimensional inversion procedure such that an inverted
20 geology formation is optimized.
65. A machine-readable storage device having instructions stored thereon,
which, when performed by a machioe, cause, the machine to perform operations,
me operations comprising:
25 acquiring measurement values from operating a measurement tool in a
borehole, the measurement tool having an antenna arrangement;
determining an average phase resistivity from the measurement values;
determining whether the average phase resistivity corresponds to a true
formation resistivity;
30 physically adjusting the arrangement of the transmitter and ihe receiver
antennas, forming new oriented transmliiftr and receiver antennas;
obtaining measurements from the new oriented transmitter and receiver
antennas; and
using die new measurement* to evaluate the average phase resistivity.
5 66. A machine-readable storage device having instructions acred thereon,
which, when performed by a machine, cause the machine ta perform operations,
the operations comprising:
acquiring measurement values from operating a measurement tool in a
borehole, the measurement tool having, an antenna arrangement;
10 calculating an average phase resistivity from the measurement values;
using geosignal responses to determine whether the measurement tool is
near a boundary average;
adjusting antenna orientations virtually or physically to specific amerma
Orientations based on the geosignal responses, the specific antenna orientations
IS being at least in part different from antenna orientations of the antenna
arrangement, and
recalculating a new average phase resistivity with respect to the specific
antenna orientations to estimate a true formation resistivity.
20 67. The machine-readable storage d evice of claim 66, wherein the antenna
arrangement includes at least one or mare non-iilted transmitters and at least two
or more receivers having a same nit angle and the specific antenna orientations
have the at least two or more receivers with 4 tilt angle different, from the tilt
angle of the antenna arrangement,
25
68. The macMne-rcadablc storage device of claim 66, wherein the antenna
arrangement includes at bast one or more tilted transmitters arranged
perpendicular to at least two or more receivers having a same tilt angle and the
specific antenna orientations have the receivers with a tilt angle different from
30 tbe tilt angle of the antenna arrangement.
39m
69. The machine-readable storage device of claim 67 or 68, wherein a
voltage signal is determined at one receiver of the receivers in response to one of
die transmitters generating a signal in the antenna arrangement and the voltage
5 signal is transformed io a new voltage signal of the one receiver by processing
based on the same tilt angle and a till angle of the specific orientation that is
different from the same tilt angle,
70. The machine-readable storage device of claim 66, wherein the method
10 includes using the recalculated new average phase resistivity as an initial guess
in a one-dimenslonaJ or multi-dimensional i nversion procedure such that an
inverted geology formation is opiimteed.
71. A Jjiachine^ieadabfc storage device having instructions stored thereon,
15 which, when performed by a machine, cause the machine n> perform operations,
the operations comprising:
acquiring measurement values from operating a measurement tool in a
borehole, the measurement tool having an antenna arrangement;
calculating an average phase resistivity front the measurement values for
2Q each of a plurality of antenna orientations, the plurality of antenna orientations
including die antenna arrangement;
comparing rhe average phase resistivities to determine If the average
phase resistivities estimate a true formation resistivity; and
using geosignal responses to determine a reading corresponding to die
25 true formation resistivity, if the comparison does not identify an estimate of the
true formation resistivity.
72. The machine-readable storage device of claim 71, wherein comparing the
average phase resistivities includes determining if magnitudes of respective
30 differences between the average phase resistivities are greater than a threshold.
73. The machine-readable Storage device of elajm 72. wherein die threshold
Is zero w un error annum greater than zero.
5 74. Hie machine-readable storage device of claim 71, wherein ths method
includes urag^ei-eadingcoiiespomiingio the tni* formation nsistivkyas an
initial guess in a one-dimensional or rnutt-djroeasional inversion procedure such
that an inverted geology formation is optimized.
10 75. Tiw machioe-readable storage device ofclaims 52.59,65,66, or 71,
wherein me method is conducted in real time.