Directing a Drilling Operation Using an Optical Computation Element
Technical Field
The present invention relates generally to apparatus for making
measurements related to oil and gas exploration.
Background
In drilling wells for oil and gas exploration, understanding the structure
and properties of the associated geological formation provides information to aid
such exploration. Optimal placement of a well in a hydrocarbon-bearing zone
(the "payzone") usually requires geosteering with deviated or horizontal well
trajectories, since most payzones extend in the horizontal plane. Geosteering is
an intentional control to adjust drilling direction. An existing approach based on
geosteering in well placement includes intersecting and locating the payzone
followed by moving the drill string to a higher position and beginning to drill a
new branch that approaches to the target zone from top. This first approach is
time consuming, where drilling needs to be stopped and a device for branching
needs to be lowered into the well. Another existing approach based on
geosteering in well placement includes intersecting and locating the payzone
followed by continuing drilling to approach the well from the bottom. This
second approach can result in overshoot of the well path from the desired target
zone and may only be effective if the well is highly deviated at point of
intersection.
Brief Description of the Drawings
Figure 1 shows a block diagram of an example apparatus having an
optical computation element for operation downhole in a well, in accordance
with various embodiments.
Figure 2 shows features of an example method of determining a property
in a borehole using an optical computation element, in accordance with various
embodiments.
Figure 3 shows features of an example method using an optical
computation element in a drilling operation, in accordance with various
embodiments.
Figure 4 shows a block diagram of an example system using an optical
computation element operable in a drilling operation, in accordance with various
embodiments.
Figure 5 shows the example system of Figure 4, where a probe device is
physically arranged on the housing to contact a borehole wall, in accordance
with various embodiments.
Figure 6 illustrates a block diagram of an example logging while drilling
tool having a window through which light can be reflected off a borehole wall, in
accordance with various embodiments.
Figure 7 shows signal logs at two different times relative to the operation
depicted in Figure 6 with respect to the tool as it rotates while moving in the
drilling direction, in accordance with various embodiments.
Figure 8 shows a block diagram of an example arrangement of an optical
computation element that examines drilling fluid flowing to and from a drill bit
in a drilling operation, in accordance with various embodiments.
Figure 9 shows features of an example method that includes using data
from an optical computation element with other data in a geosteering procedure,
in accordance with various embodiments.
Figure 10 depicts a block diagram of features of an example system
having a tool structured with an optical computation element, in accordance with
various embodiments.
Figure 11 depicts an example system at a drilling site, where the system
includes a tool structured with an optical computation element, in accordance
with various embodiments.
Detailed Description
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
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
sense.
In various embodiments, an optical computation element can be arranged
to operate in a downhole environment to provide optical analysis of fluid and
material composition of the downhole environment associated with a drilling
operation. An example of an optical computation element is a multivariate
optical element (MOE). An optical computation element, arranged in a device
or system to provide operational functionality with other components, may be
referred to as an integrated computational element. An example of the principles
of MOE operation can be found in Myrick, Soyami, Schiza, Farr, Haibach,
Greer, Li and Priore, "Application of multivariate optical computing to simple
near-infrared sample point measurements", Proceedings of SPIE vol. 4574
(2002). Light from a light source can pass through a sample, or reflect off the
sample, and be partially transmitted and reflected from the MOE, which includes
an interference filter. The difference between the transmitted and reflected light
spectra is S(X)L(X), where S(X) is the spectrum of light from the sample and L(X)
is the spectral characteristic that the MOE is designed to provide. Since
detectors measure intensity, the measured difference is the integral of S(X)L(X)dX
over the bandwidth of the system. When the MOE spectral characteristic L(X) is
chosen to provide a measurement of a specific substance, the output of the
system provides a relative measure of that substance's concentration. Multiple
MOEs can be used to test for different substances. An example of multivariate
optical elements for an optical analysis system can be found in U.S. Patent
Application US 7,91 1,605. In addition, one approach to MOE design, including
techniques for nonlinear calibration, can be found in U.S. Patent Application
Publication 2010/0153048.
A MOE is an optical computation element that may be viewed as an
analog computer, which uses light, to perform only one computation. A MOE
can be arranged such that it adds, subtracts, multiplies, and divides. It is noted
that addition, subtraction, multiplication, and division are operations that can be
used to perform what is called a regression. A regression is typically an
inversion process to extract information, which is specific data, from a broader
form of data. When light (electromagnetic radiation) interacts with matter, in
whatever form the matter has, the chemical and physical characteristics of the
matter, which are optically active, effectively encodes itself into that light.
MOEs can be designed essentially as optical processors with regression vectors
to extract the relevant data of the matter interacting with light.
MOEs that perform a computation in the optical domain can be
constructed in a manner similar to construction of an optical filter. Optical
filters can be constructed as an interference filter, an absorption filter, a
holographic filter, or other form of filter of electromagnetic radiation. An
optical filter is typically designed to pass or reject a specific band of light, where
a band is generally a continuous subset of light. For example, an optical filter
can be realized as a Gaussian filter, a cut-off filter, a broadband filter, or other
type of filter structured with respect to one or more continuous ranges of
frequencies (wavelengths) of light such that the filter transmits, or rejects, light
with respect to these frequencies. An optical filter, in general, has a specific
transmissive characteristic such that it transmits or rejects a certain amount of
light over a range of frequencies that can be referred to as the width of the band.
The output of these filters is light at selected frequencies, whose total intensity
can be detected. However, unlike filters, a MOE can provide more extractible
data than the total intensity of light that is passed.
Using filter construction techniques, a regression vector can be encoded
into the filter forming an MOE. The encoded regression vector uses the
interference properties of light. Light can interfere with itself, providing positive
or negative interference. This positive and negative inference allows for a
mathematical calculation on the light itself. With a regression vector encoded
into the optical filter, as light passes through the encoded optical filter, a
calculation is performed. An encoded filter in such a configuration is no longer
a filter in the conventional sense of the filter. In addition, by encoding a pattern
recognition or a dot-product regression vector into the filter forming the MOE,
information can be extracted from the optical stream to the MOE at a much
higher resolution than the bandwidth of the MOE. Since the transmission and
absorption properties of materials are typically wavelength dependent, an optical
computation element can be arranged with respect to other optical components
that provide to light to the optical computation element in a selected range of
wavelengths.
In various embodiments, an optical computation element, such as a
MOE, can be arranged to operate downhole in a well. Optical computation
elements structured as part of a drilling tool can be used for a variety of
applications including, but not limited to, extraction of physical and/or chemical
information about the well bore, extraction of physical and/or chemical
information about fluids in the well bore, application of the extracted
information to monitor the safety of a drilling operation, and application of the
extracted information for steering a drill bit in a drilling operation. To collect
information about the well bore, light from an interaction with the well bore can
be passed through an optical computation element, which is designed to examine
a property of the well bore under investigation. With the light interacting with
the optical computation element, the light has been mathematically operated on
by this optical computation element. The output from the optical computation
element can be passed to an optical detector. The signal output from the optical
detector is specifically related to the answer from the query made by the encoded
optical computation element. For example, the signal output from the optical
detector can be specifically related to an estimation of the property of the well
bore or the fluids in the wellbore. The property can include, but is not limited to,
concentration of the analytes of the wellbore or fluids. The output of the
detector may be directly proportional to the property being investigated. The
output may differ from direct proportionality due to such factors as slight
non-linearities of the detector or the calibration of the system may not be
perfectly linear. For example, if a slightly non-linear calibration is encoded into
MOE, then the output light might be slightly non-linear as well. Due to these
variations, the signal output from the detector is an estimation of the property
under investigation. However, the signal output may be directly related to the
property under investigation.
The property under investigation may include, among other properties,
composition of the wellbore, fluid composition, fluid composition at the contact
with the well bore surface, or the porosity of the wellbore. The property under
investigation can include relative concentrations of different materials associated
with a drilling operation. For example, when examining a reservoir section, an
optical computation element can provide data with respect to relative
concentrations of such materials as sand, a carbonate, and clay in the section.
This data can provide information on the quality of the reservoir section, where
the quality is based on materials present in the section. The quality analysis can
be made with respect to fluids such as oil and water. In addition, data provided
by the optical computation element can be used to steer a drilling operation away
from a water section or towards an oil section.
Figure 1 shows a block diagram of an embodiment of an apparatus 100
having an optical computation element 105. Light can be directed to optical
computation element 105, which can be arranged such that a portion of light
passes through optical computation element 105 to detector 107 and a portion of
the light is reflectively directed from optical computation element 105 to
detector 109. The light directed to optical computation element 105 can the
result of an interaction of material under investigation. The interaction may be
realized with light transmitted through the material, light reflected from the
material, light emitted from the material, or light scattered from the material.
For transmission or reflection from the material, the light can be provided to the
material by a source incorporated in apparatus 100. Apparatus 100 can also
include other optical components such as filters and beamsplitters to provide the
light to optical computation element 105 that can be limited to a wavelength
range correlated to the material under investigation.
Figure 2 shows features of an embodiment of a method of determining a
property in a borehole using an optical computation element. At 210, light from
a borehole wall is directed to an optical computation element. A probe light can
be directed at the borehole wall such that redirection of the probe signal from the
borehole wall provides the light directed from the borehole wall to the optical
computation element. The probe light can be generated using a probe device
such that the probe device physically contacts the borehole wall, where the probe
light passes from the probe device to the borehole wall. Material can be scraped
off from the borehole wall using the probe device. The material scrapped off can
include some of the filter cake that naturally builds up on the wellbore.
Removing such material provides a mechanism to reflect light from the interface
of the optical probe and the wellbore. This process yields data about this
interface. In various embodiments, sapphire, zinc sulfite, a diamond, or silicon
carbide can be used as materials for the optical probe device. These are hard
materials that can both serve as an optical conduit to the wellbore and as a
method of removing the filter cake. The use of these materials can be correlated
with the selection of an optical source such that the wavelength is optically
transparent in certain optical regions for the selected material for the probe
device. The probe light can be also generated by transmitting the probe light
from a source, disposed in a tool containing the optical computation device,
through a fluid to the borehole wall.
In an embodiment, an optical conduit for probe light propagating
between the tool containing the optical computation device and the wellbore can
be formed using drilling fluid. A portion of the drilling fluid flowing down the
center of the drillstring can be tapped near the location of the tool such that the
tapped portion of the drilling fluid flows between the tool and the wellbore wall.
This tapped drilling fluid provides the conduit through which light can propagate
between the wellbore wall and the tool. The drilling fluid provides a relatively
transparent medium that is substantially free of solids, since the drilling fluid in
this portion of its flow pattern in the drilling operation has been provided
substantially free of solids. This formed conduit allows examining the wellbore
wall without a probe contacting the wellbore wall.
At 220, light output from the optical computation element in response to
the optical computation element receiving the light from the borehole wall is
analyzed. At 230, a property associated with the borehole wall is determined
from analyzing the light output from the optical computation element. Based on
the determined property, a signal can be generated to direct a drilling operation.
Generating the signal to direct the drilling operation can include geosteering the
drilling operation. Geosteering the drilling operation can include maintaining
the borehole within a reservoir pay zone. Generating the signal to direct the
drilling operation can include generating a monitoring signal to provide
advanced warning with respect to a safety condition of the drilling operation.
Determination of a property associated with the borehole wall can
include determining one or more of a porosity of the borehole wall, a
composition of the borehole wall, or a formation fluid measurement
corresponding to the borehole wall. In addition, values of the property
associated with the borehole wall can be determined as the tool, on which the
optical computation device is disposed, moves along a length of the borehole. A
two-dimensional map of the borehole wall can be generated from these values.
In addition, contamination within a drilling fluid from the drilling action can be
monitored from analyzing the light output from the optical computation element
with respect to a frequency of light, in the light directed to the optical
computation element, at which the drilling fluid is transparent.
Figure 3 shows features of an embodiment of an example method using
an optical computation element in a drilling operation. At 310, one or more
optical computation elements are used to determine an optical characteristic of a
drilling fluid within a drillstring of a drilling operation. In an embodiment, only
one optical computation element is used to determine an optical characteristic of
a drilling fluid within a drillstring of a drilling operation. At 320, the one or
more optical computation elements are used to determine an optical
characteristic of a fluid within an annulus of the drillstring. The annulus is the
space between two objects, such as between the wellbore and casing, where the
casing is a pipe disposed in the wellbore, between casing and tubing, or between
drillstring and wellbore wall.
At 330, a difference between the optical characteristic of the drilling fluid
and the optical characteristic of the fluid within the annulus is monitored. The
method can include measuring fluids leaking into a formation due to drilling at a
drill bit location in the drilling operation. Based on monitoring the difference
between the optical characteristic of the drilling fluid and the optical
characteristic of the fluid within the annulus, a property associated with the fluid
within the annulus can be determined. A signal can be generated to direct a
drilling operation based on the determined property. Generating the signal to
direct the drilling operation can include geosteering the drilling operation or
generating a monitoring signal to provide advanced warning with respect to a
safety condition of the drilling operation.
Figure 4 shows a block diagram of an embodiment of an example system
400 using an optical computation element 405 operable in a drilling operation.
Optical computation element 405 is disposed in a housing 401, where housing
401 is attachable to a drillstring. A window 402 in housing 401 can be arranged
to receive light from exterior to housing 401 such that the light is directed from a
region, exterior to the drillstring, to optical computation element 405 when
housing 401 is mounted on the drillstring. An analysis unit 420 can be
structured to provide a signal based on an output from optical computation
element 405 in response to optical computation element 405 receiving the light
from exterior to the drillstring, where the signal is provided from analysis unit
420 to direct a drilling operation based on a property of the region determined
from the output from optical computation element 405. System 400 can also
include an optical source 415 to generate light that is reflected from exterior to
the housing such that the reflected light provides the received light directed to
optical computation element 405. System can also include an additional window
403 structured such that the generated light by the optical source 415, with
optical source 415 disposed in housing 401, exits housing 401 to reflect from
exterior to housing 401 .
Windows 402 and 403 can consist of a material that is transparent at the
desired wavelengths of operation for optical computation element 405. The
material selected for windows 402 and 403 may be a hard material such as
sapphire. Other transparent materials that have hardness characteristics for use
downhole can include silicon carbide or other hard materials that provide optical
transparency for the selected application.
System 400 can include optical detectors 408 arranged relative to optical
computation element 405 to detect light directed from optical computation
element 405 to the respective optical detector. The arrangement of optical
detectors 408 can be coupled with analysis unit 420 to provide signals to
analysis unit 420. An analysis unit 420 can be structured to determine a
difference between a drilling fluid within a drillstring of a drilling operation and
a fluid within an annulus of the drillstring based on the signals. System 400 can
also include optical elements 4 1 to direct light from optical computation
element 405 to optical detectors 408. Optical elements 4 11 can include one or
more optical components such as lenses, filters, or beamsplitters. System 400
can also include optical elements 413 to direct light to optical computation
element 405 from window 402. Optical elements 413 can include one or more
optical components such as lenses, filters, or beamsplitters.
Figure 5 shows system 400 structured with a probe device 515 physically
arranged on housing 401 to contact a borehole wall. Probe device 515 can be
structured to generate a probe light, with probe device 515 physically arranged
on housing 401 to contact a borehole wall, such that probe light passed from
probe device 515 to the borehole wall provides the received light from exterior
to housing 401 directed towards optical computation element 405. Probe device
515 can be structured as conduit to transit light from source 415 outward from
housing 401 . Probe device 15 can be structured to be operable to scrap off
material from the borehole wall. Sapphire, zinc sulfite, diamond, or silicon
carbide can be used as materials for probe device 515. These are hard materials
that can both serve as an optical conduit to the wellbore wall and as a structure to
remove filter cake from the wellbore wall. The use of these materials can be
correlated with the selection of the optical source such that the wavelength is
optically transparent in certain optical regions for the selected material of probe
device 515.
Probe device 515 can be realized using a pad pressed firmly against the
borehole wall. Using the pad, fluid can be withdrawn from the formation into
the wellbore, which clears out the filter cake and provides a clear fluid path to
the formation. The clear fluid path provides an optical conduit to direct light
from source 4 1 to the borehole wall. The fluid may be water, oil, gas, or
combinations thereof. The quality of the optical conduit depends on the type of
fluid withdrawn using the pad. Alternatively, rather than withdrawing fluid from
the formation to provide an optical conduit, the pad can be flushed with a
designed optically transparent fluid. To effectively scrap off the material from
the wellbore wall, probe device 515 may also be realized by pressing a snorkel
like device an inch or so into the wellbore. The pressing activity can be
conducted by hydraulically placing about 10,000 to 20,000 psi onto the snorkel
that presses it into the wellbore.
In various embodiments, an optical computation element, such as a
multivariate optical element, can be used in geosteering applications. When
incorporated into a logging-while-drilling (LWD) tool, MOEs can provide
measurements of borehole wall composition including boundaries, fractures, and
formation fluid measurements. These measurements can be converted into a
borehole wall map to enable drillers to visualize the downhole situation.
Information from processing MOE data can be combined with other information
to decide in which direction to steer the borehole. This other information can
include information regarding the drilling operation that includes data from
regions away from the drilling location near which the MOE-based tool is
located. Since data from a MOE-based tool is collected from regions within
close proximity, this other information essentially provides a bigger picture of
the drilling operation. In addition, information from processing MOE data can
be incorporated into electronic control systems to direct the drilling operation
autonomously such that activities of drillers can be directed to monitoring the
geosteering along with overall regulation of the drilling operation.
Figure 6 illustrates a block diagram of an embodiment of an example
logging while drilling tool 600 having a window 602 through which light can be
reflected off a borehole wall 604. Drilling tool 600 can be located in a pressure
housing behind drill bit 626. As shown in Figure 6, drill bit 626 is being
directed into bedding plane 606 in the L+ direction. Window 602 can be
positioned to minimize effects of borehole fluids. For example, window 602 can
be positioned on a stabilizer blade 612 or some other protrusion from the body of
drilling tool 600. Window 602 can be inset such that window 602 is protected
from abrasion. Window 602 can also be protected from abrasion by guard
structures of some form. Such guard structures can be used with window 602
inset or without window 602 inset. Window 602 can be very small, e.g., the size
of a fiber-optic terminus. Illumination of a borehole wall 604 can be provided
through the window 602 or through a separate window. As drilling progresses,
path of window 602 traces a tight spiral along the borehole wall 604, enabling
tool measurements to provide a two-dimensional (2D) map of the borehole wall
characteristics as indicated in Figure 7 .
Figure 7 shows signal logs at two different times relative to the operation
depicted in Figure 6 with respect to tool 600 as it rotates while moving in
direction L+. A monitored signal 721 from window 602 provides at pattern at
time ti, while monitored signal 723 from window 602 provides a pattern at a
later time t . As can be seen, the pattern is evolving from striking bedding plane
606 at an angle, indicated in 721 to being completely within the bedding zone,
indicated in 72 1.
The data from the tool using an optical computation element, such as an
MOE, can be used to determine and indicate that the drilling operation is within
a target zone. Continuing processing of the data from the tool can be used to
stay within a particular target zone, which may be an oil-bearing formation, for
the drilling operation. If the region entered is not the target, the data from the
tool can be used to continue drill laterally in the current direction for awhile until
a target zone is reached or the data from the tool can be used to alter the
direction of drilling. From the tool data, drilling direction can be altered to
progress through soft shell in the area rather than nearby hard sandstone. In
addition, steering using the tool is not necessarily solely for the purpose of
sniffing and staying within a reservoir section, but can be used to determine the
particular lithologic zone in which the tool is disposed.
Light reflected from a borehole wall can be processed by one or more
optical computation elements, such as MOEs, to measure various formation
characteristics. For example, processing of the reflected light by the optical
computation elements can provide a measurement of concentration of
hydrocarbon molecules and rock composition. A borehole wall map generated
by processing that uses the optical computation elements can provide indications
of reservoirs and boundaries penetrated by the borehole. An operator observing
the map can make steering decisions such as, for example, decisions to keep the
borehole within a reservoir pay zone. These decisions can include decisions to
steer away from regions. Alternatively, results of the processing can be
autonomously provided to an analysis unit of an automated system to determine
parameters to use to conduct drilling operations. The automated system can
include one or more processors, a memory system, and logic devices to compare
the results with stored information that represents properties of pay zones. The
stored information can include properties of regions to be avoided. The
geosteering analysis can include an iterative process of evaluating the changes in
the processed light with respect to the comparisons of the processed light with
respect the stored information. Evaluation of these changes can provide a basis
for making geosteering adjustments.
Measurement information from optical computation elements can be
communicated with associated tool position and orientation information to a
surface processing facility where it can be analyzed and presented to an operator
for use in steering the borehole. Alternatively, downhole electronics can be
structured to analyze data from the measurements of the optical computation
elements along with other information to autonomously steer the borehole.
Tools, with optical computation elements such as MOEs, used to
measure characteristics of a borehole wall can be structured to have the
capability to essentially look through the wellbore fluid using light, at radiative
energies transparent to the drilling fluid, that impinges on the borehole wall. The
optical computation elements also can be structured to have the capability to
monitor contamination within the drilling fluid. Such devices can be arranged to
operate as either in a differential technique or as a direct measurement of the
fluid in the annulus. A differential technique, for example, can include
monitoring the difference between the optical characteristics of drilling fluid
within the drill string to that in the borehole annulus. The arrangement of one or
more optical computation elements, such as MOEs, allows measurements of
fluids leaking into the formation via the drilling action at the bit. In a differential
configuration for monitoring fluid properties, a single optical computation
element can be used for monitoring "fresh drilling fluid" and annular fluid
canceling out a significant amount of common mode variation.
During a drilling operation, formation fluid can invade the drilling fluid
near the drill bit. Near the drill bit, the material of the drilling operation can
include drilling fluid with a small portion of formation fluid that is influx into
the wellbore with the drilling fluid. An approach to examining this relatively
small amount of influx of formation fluid can include subtracting the effect of
the drilling fluid itself. The drilling fluid itself, before the trace constituents are
added by the drilling action, is essentially the material flowing through the
annular pipe not far away from the drill bit. An indication of the drilling fluid
without this trace constituent can be attained by examining the fluid that is
flowing through the inside of the pipe. Thus, examining the fluid flowing
through the inside of the pipe versus the fluid with the trace constituents from
the formation on the outside of the pipe provides a differential measurement.
Making a differential determination of fluids between what is inside and outside
the drilling string generates a measurement of the formation fluid (trace
constituents) with enhanced resolution. The enhanced resolution results from the
large portion of the measurements that is common to the inside and outside being
removed from the measurement. The differential measurement can be made
with one or more optical computation elements.
Figure 8 shows an arrangement of an optical computation element 805
that examines drilling fluid flowing to and from drill bit 826 in a drilling
operation. Optical computation element 805 can be arranged on a drill string
829 near drill bit 826 in a wellbore having wall 804. A source 815 provides light
that is directed out window 802-2 towards the drilling fluid flowing towards drill
bit 826. The drilling fluid flowing towards drill bit 826 can flow within the drill
string 829. Source 815 can also provide light that is directed out window 802-1
towards the drilling fluid flowing back from drill bit 826 that can include
constituents 819 from the formation. Alternatively, two different light sources
can be used. A difference between the fluids flowing in the two directions is
essentially constituents 819. A difference operation on measurement signals
between the two directions can eliminate common factors that form the dominant
portion of each individual measurement. This difference operation should
provide data regarding constituents with higher resolution than measurements to
determine constituents 819 directly as part of the fluid flow away from drill bit
826.
Light reflected from drilling fluid flowing towards drill bit 826 is
received in window 802-2. Alternatively, window 802-2 can be arranged as two
windows with one to transmit the light from source 815 and the other one to
receive the light reflected from the drilling fluid flowing towards drill bit 826.
Light reflected from drilling fluid flowing away from drill bit 826 is received in
window 802-1. Alternatively, window 802-1 can be arranged as two windows
with one to transmit the light from source 815 and the other one to receive the
light reflected from the drilling fluid flowing away from drill bit 826. The light
received in window 802-1 and the light received in window 802-2 are directed to
optical computation element 805.
Optical computation element 805 can be arranged with four detectors
808-1, 808-2, 808-3, and 808-4, which can be referenced with respect to signals
Dl, D2, D3, and D4, respectively. Additional optical components can be used to
direct and provide the appropriate light to optical computation element 805 and
detectors 808-1, 808-2, 808-3, and 808-4. These additional optical components
can include lenses, filters, and beamsplitters, which are not shown for ease of
presenting the arrangement of optical computation element 805. Signals Dl and
D3 are reflected from optical computation element 805 to their respective
detectors 808-1 and 808-3, and signals D2 and D4 are transmitted through
optical computation element 805 to their respective detectors 808-2 and 808-4.
The difference between the transmissive signal and the reflected signal is
directly related to the concentration of interest. A ratio of the respective
properties can be formed as (kiDi-k 2D )/( 3 D3-k4D4), where k , k2, k3, and are
fitting constants.
Although it is possible to monitor differences in fluid content at the
surface using fluid measurements made at the surface, providing this service
downhole provides operational enhancements. For example, steering decisions
using a downhole MOE arrangement can be made immediately not delayed as
compared with surface measurements. Delays with surface measurements
include the transit time for cuttings and fluid to reach surface from the drill bit,
where such transit time is typically ½ hour to 1 hour.
Using one or more MOEs arranged to make downhole measurements, the
fluid emanating from the formation can be monitored for various compounds.
For example, the MOE arrangement can be used to monitor for methane, which
is one of the lightest components of petroleum and is likely to invade the
wellbore. Upon detecting methane, the drill bit can be steered towards higher
concentrations of methane.
Monitoring for compounds is not limited to methane. Compounds for
which MOE- based monitoring includes propane, light hydrocarbons, and other
compounds related to the particular drilling operation. The steering from
analysis of the output of the downhole MOE device can be conducted based on a
distribution, not just a single component. For example, if the MOE-based
monitoring shows an increase in a ratio of methane to butane, this increase may
indicate that the drilling is being directed into a gas cap, since the ratio of
methane increasing relative to the concentration of butane indicates that a region
enriched in gas components. For oil drilling steering, such indications can be
used to direct the steering back out of this gas-enriched region back to the oil
based reservoir section. The steering operation can be conducted maintain a
distribution of light hydrocarbon components, such as but not limited to
methane, ethane, propane, butane, pentane, and hexane, to appropriately place
the well. Such steering of the drilling operation uses the chemical information
from the downhole MOE arrangement that examines the constituents of the
drilling fluid filtrate itself.
In contrast to monitoring fluids at the surface via a surface run fluid log,
using an MOE downhole provides a sensor located closer to the drilling bit. At
the surface, the constituents of the mud brought to the surface have spread
transversely relative to the pipe as the fluid moves up the drillstring to the
surface. Mud is drilling fluid that may include solids and other constituents from
the drilling operation. Hence, a downhole MOE sensor arrangement located
closer to the drill bit versus the surface run fluid log provides a measurement in
which the drilling fluid examined has experienced less transverse dispersion for
the sensor located closer to the drill bit. In addition, uphole the properties of the
mud are only a proxy for the fluid downhole, whereas downhole the mud can be
directly monitored before and after the drill bit and hence provide a differential
of finer resolution. With less transverse dispersion, and finer resolution potential
pay zones may be better identified.
Using an arrangement of an optical computation element, such as a MOE
arrangement, downhole allows for better marking of a water oil contact point.
This enhanced operation is provided because methane, which is much less
soluble in water than hydrocarbons, can be detected by the optical computation
element close to its location downhole. In addition, a downhole optical
computation element can monitor for sharp rises of certain components before
they reach the surface. For example, a downhole optical computation element
can monitor for compounds such as ¾ S or methane, knowledge of which can
allow "kicks or blowouts" to be mitigated before they occur. A kick is a flow of
formation fluids into the wellbore during drilling operations. A blowout is an
uncontrolled flow of reservoir fluids into the wellbore, and sometimes
catastrophically to the surface. A blowout may consist of salt water, oil, gas, or
combinations thereof. If kick or blowouts do occur, a downhole optical
computation element can be structured such that a control system and/or drillers
receive advanced warning of the kicks or blowouts.
A measurement arrangement using an optical computation element, such
as a downhole MOE based measurement arrangement, can also be structured to
monitor for such compounds as methane, ethane, C0 2, H2S, or other volatile
components. This monitoring provides a safety mechanism in that it can
generate an early warning regarding the presence of these volatile compounds.
For example, H2S typically reacts a way in the caustic mud such that it is not
readily apparent that the drilling has gone through a reservoir section containing
¾ S based on the mud analysis at the surface.
A downhole MOE based measurement arrangement may be structured to
monitor the volatile components in the mud of the drilling operation as the
saturation point of the mud for those volatile components is approached. The
properties of the drilling fluid with respect to saturation by gases such as how
much gas can be dissolved in the mud before it goes two phase for a particular
pressure and temperature are typically well understood. Since the MOE based
measurement provides an analysis of chemical composition, the downhole MOE
arrangement can be used to monitor for these gases to provide early kick
detection. For example, with a downhole MOE arrangement providing the early
kick detection indicating that two phase has just been broken down hole,
appropriate actions can be taken at the surface. In addition, with the downhole
MOE arrangement structured to monitor a rapidly increasing concentration of
methane or volatile components, mitigating steps may be taken to prevent a kick
from occurring. The arrangement of a MOE or other optical computation
element as a downhole measurement tool, in accordance with arrangements as
taught herein, may provide for the prevention of blowup scenarios.
In contrast to surface fluid measurement, downhole measurements using
optical computation elements, such as MOEs, can provide immediate knowledge
as to location with respect to a pay zone, or target zone. Such knowledge may
be especially useful with respect to horizontal drilling to stay in a target zone.
Optical computation element based information of a LWD tool can be combined
with other "big picture" information to assist a drill rig operator in identifying
and following desirable borehole pathways or to provide data to an automated
system to identify and follow desirable borehole pathways. In various
embodiments, geosteering can be performed based in whole or part on MOE
measurements. The range of such measurements may be limited, and the
borehole fluids may interfere with the reliability of such measurements.
Nevertheless, such measurements offer a low power way to obtain high quality
measurements of formation composition.
Figure 9 shows features of an embodiment of a method that includes
using data from an optical computation element with other data in a geosteering
procedure. At 910, a set of data related to the drilling operation of interest is
acquired. This data can include data from one or more measurement techniques.
For example, the acquired data can include an acoustic image log, a gamma log,
and resistivity data from measurements using different tools. These can include
acoustic and electromagnetic tools that examine the formation over a relatively
large distance from the borehole. Acquisition of this set of data can include
operating these tools to collect the data.
At 920, data from a tool using an optical computation element downhole
in the drilling operation is generated. Signals output from detectors of the tool
arranged with the optical computation element can be analyzed to generate data
regarding the chemical composition near the tool. The tool can typically be
disposed near a drill bit in a logging while drilling operation. This arrangement
provides data for assessment of the formation near the drilling point.
At 930, the location of the drilling operation relative to the surrounding
formation using the acquired data and the generated data is assessed. The
chemical data generated from the optical computation element can be combined
with image data from other tools for display at the surface to monitor and/or
direct the geosteering activity. In addition, the chemical data generated from the
optical computation element near the drill bit can be combined with other data,
such as resistivity data, relative to regions away from the drill it to provide a
indication of which direction to geosteer the well.
At 940, the well is geosteered based on the assessment. The geosteering
can include, among other actions, maintaining the well in a desired target region
such as a reservoir, directing the well away from regions such as regions with
high water content, or directing the well through regions that are easier for the
drilling operation to traverse. The geosteering can be controlled from a surface
system under the direction of an operator. The geosteering can be controlled by
downhole electronics that are arranged to collect the data, make comparisons,
and generate control signals to operate the direction of the drill bit using
instructions stored in the electronics. The downhole control of the geosteering
can be monitored at the surface by an operator.
Figure 10 depicts a block diagram of an example embodiment of a
system 1000 having a tool 1010 structured with an optical computation element
1005 operable downhole in a well. Tool 1010 can include optical detectors
1008, optical elements 101 1, and a probe source 1015 that operate in conjunction
with optical computation element 1005. System 1000 can be structured to
operate optical computation element 1005 in accordance with the teachings
herein. System 1000 can include a controller 1025, a memory 1035, an
electronic apparatus 1065, and a communications unit 1040.
Controller 1025, memory 1035, and communications unit 1040 can be
arranged to operate as a processing unit to control operation of tool 1010, in a
manner similar or identical to the procedures discussed herein. Such a
processing unit can be realized using a data processing unit 1030, which can be
implemented as a single unit or distributed among the components of system
1000 including electronic apparatus 1065. Controller 1025 and memory 1035
can operate to control activation of probe source 1015 and collection of signals
from tool 1010. The collection of signals can include acquisition from optical
detectors 1008 to analysis the chemical based data generated by tool 1010 in
accordance with measurement procedures and signal processing as described
herein. System 1000 can be structured to function in a manner similar to or
identical to structures associated with Figures 1-9 and 11.
System 1000 can also include a bus 1027, where bus 1027 provides
electrical conductivity among the components of system 1000. Bus 1027 can
include an address bus, a data bus, and a control bus, each independently
structured or in an integrated format. Bus 1027 can be realized using a number
of different communication mediums that allows for the distribution of
components of system 1000. Communications unit 1040 can include downhole
communications operable with bus 1027. Such downhole communications can
include a telemetry system. Use of bus 1027 can be regulated by controller
1025.
In various embodiments, peripheral devices 1045 can include additional
storage memory and/or other control devices that may operate in conjunction
with controller 1025 and/or memory 1035. In an embodiment, controller 1025 is
realized as a processor or a group of processors that may operate independently
depending on an assigned function. Peripheral devices 1045 can be arranged
with one or more displays 1055, as a distributed component on the surface, that
can be used with instructions stored in memory 1035 to implement a user
interface to monitor the operation of tool 1010 and/or components distributed
within system 1000. The user interface can be used to input operating parameter
values such that system 1000 can operate autonomously substantially without
user intervention.
Figure 11 depicts an embodiment of a system 1100 at a drilling site,
where system 1100 includes a measurement tool 1 1 10 structured with an optical
computation element. System 1100 includes tool 1110 having an optical
computation element that can be realized in a similar or identical manner to
arrangements discussed herein. System 1100 can include a drilling rig 1102
located at a surface 1104 of a well 1106 and a string of drill pipes, that is, drill
string 1129, connected together so as to form a drilling string that is lowered
through a rotary table 1107 into a wellbore or borehole 1112. The drilling rig
1102 can provide support for drill string 1129. The drill string 1129 can operate
to penetrate rotary table 1107 for drilling a borehole 1112 through subsurface
formations 1114. The drill string 1129 can include drill pipe 1118 and a bottom
hole assembly 1120 located at the lower portion of the drill pipe 1118.
The bottom hole assembly 1120 can include drill collar 1115,
measurement tool 1110 attached to drill collar 1115, and a drill bit 1126. The
drill bit 1126 can operate to create a borehole 1112 by penetrating the surface
1104 and subsurface formations 1114.
Measurement tool 1110 can be structured for an implementation in the
borehole of a well as a measurements-while-drilling (MWD) system such as a
LWD system. Measurement tool 1110 may include optical detectors, optical
elements, and a probe source that operate in conjunction with an optical
computation element. System 1100 can be structured to operate the optical
computation element in accordance with the teachings herein. Measurement tool
1110 can include a data processing unit to analyze signals generated by
measurement tool 1110 and provide measurement results from tool 1110 to the
surface over a standard communication mechanism for operating a well.
Alternatively, measurement tool 1110 can include electronics with a
communications interface to provide signals generated by measurement tool
1110 to the surface over a standard communication mechanism for operating a
well, where these signals can be analyzed at a processing unit at the surface.
In various embodiments, measurement tool 1110 may be included in a
tool body 1170 coupled to a logging cable 1174 such as, for example, for
wireline applications. Tool body 11 0 can include measurement tool 1110
containing optical detectors, optical elements, and a probe source that operate in
conjunction with an optical computation element. System 1100 can be
structured to operate the optical computation element in accordance with the
teachings herein. Measurement tool 1110 can include a data processing unit to
analyze signals generated by measurement tool 1110 and provide measurement
results from tool 1110 to the surface over a standard communication mechanism
for operating a well. Alternatively, measurement tool 1110 can include
electronics with a communications interface to provide signals generated by
measurement tool 1110 to the surface over a standard communication
mechanism for operating a well, where these signals can be analyzed at a
processing unit at the surface Logging cable 1174 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 in bore hole 1112.
During drilling operations, the drill string 1129 can be rotated by the
rotary table 1107. In addition to, or alternatively, the bottom hole assembly
1120 can also be rotated by a motor (e.g., a mud motor) that is located downhole.
The drill collars 1115 can be used to add weight to the drill bit 126. The drill
collars 1115 also can stiffen the bottom hole assembly 1120 to allow the bottom
hole assembly 1120 to transfer the added weight to the drill bit 1126, and in turn,
assist the drill bit 1126 in penetrating the surface 1104 and subsurface
formations 1114.
During drilling operations, a mud pump 1132 can pump drilling fluid
(sometimes known by those of skill in the art as "drilling mud") from a mud pit
1134 through a hose 1136 into the drill pipe 1118 and down to the drill bit 1126.
The drilling fluid can flow out from the drill bit 1126 and be returned to the
surface 1104 through an annular area 1140 between the drill pipe 1118 and the
sides of the borehole 112. The drilling fluid may then be returned to the mud
pit 1134, where such fluid is filtered. In some embodiments, the drilling fluid
can be used to cool the drill bit 1126, as well as to provide lubrication for the
drill bit 1126 during drilling operations. Additionally, the drilling fluid may be
used to remove subsurface formation 1114 cuttings created by operating the drill
bit 1126.
In various embodiments, a machine-readable storage device, such as a
computer-readable storage device, has machine-executable instructions, which
when executed by a controller, such as a processor, cause a measurement tool to
operate downhole in a well using an optical computation element. These
instructions provide a mechanism for the measurement tool to operate in a
manner similar to or identical to a measurement having an optical computation
element associated with Figures 1-1 1. The machine-readable storage device is
not limited to any one type of device. Further, a machine-readable storage
device, herein, is a physical device that stores data represented by physical
structure within the device. Machine-readable storage devices may include, but
are not limited to, solid-state memories, optical devices, and magnetic devices.
Examples of machine-readable storage devices include, but are not limited to,
read only memory (ROM), random access memory (RAM), a magnetic disk
storage device, an optical storage device, a flash memory, and other electronic,
magnetic, and/or optical memory-like devices.
Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the art that any
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
that 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 the above embodiments and other embodiments
will be apparent to those of skill in the art upon studying the above description.
CLAIMS
What is claimed is:
1. A method comprising:
directing light from a borehole wall to an optical computation element,
analyzing light output from the optical computation element in response
to the optical computation element receiving the light from the borehole wall;
and
determining a property associated with the borehole wall from analyzing
the light output from the optical computation element.
2. The method of claim 1, wherein the method includes generating a signal
to direct a drilling operation based on the determined property.
3. The method of claim 2, wherein generating the signal to direct the
drilling operation includes geosteering the drilling operation.
4 . The method of claim 3, wherein geosteering the drilling operation
includes maintaining the borehole within a reservoir pay zone.
5. The method of claim 2, wherein generating the signal to direct the
drilling operation includes generating a monitoring signal to provide advanced
warning with respect to a safety condition of the drilling operation.
6 . The method of claims 1 or 2, wherein determining the property
associated with the borehole wall includes determining one or more of a porosity
of the borehole wall, a composition of the borehole wall, or a formation fluid
measurement corresponding to the borehole wall.
7. The method of claim 1, wherein the method includes generating probe
light directed at the borehole wall such that redirection of the probe signal from
the borehole wall provides the light directed from the borehole wall to the optical
computation element
8. The method of claim 7, wherein generating the probe light includes using
a probe device such that the probe device physically contacts the borehole wall
and the probe light passes from the probe device to the borehole wall.
9 . The method of claim 8, wherein the method includes scraping off
material from the borehole wall using the probe device.
10. The method of claim 7, wherein generating the probe light includes
transmitting the probe light from a source, disposed in a tool containing the
optical computation device, through a fluid to the borehole wall.
11. The method of claim 1, wherein the method includes determining values
of the property associated with the borehole wall as a tool, on which the optical
computation device is disposed, moves along a length of the borehole; and
generating a two-dimensional map of the borehole wall from the values.
1 . The method of claim 11, wherein the method includes monitoring
contamination within a drilling fluid from analyzing the light output from the
optical computation element at a frequency of light, in the light directed to the
optical computation element, for which the drilling fluid is transparent.
13. A method comprising:
using one or more optical computation elements to determine an optical
characteristic of a drilling fluid within a drillstring of a drilling operation;
using the one or more optical computation elements to determine an
optical characteristic of a fluid within an annulus of the drillstring; and
monitoring a difference between the optical characteristic of the drilling
fluid and the optical characteristic of the fluid within the annulus.
14. The method of claim 13, wherein the method includes measuring fluids
leaking into a formation due to drilling at a drill bit location in the drilling
operation.
15. The method of claim 13, wherein the method includes using only one
optical computation element.
16. The method of claim 13, wherein the method includes determining a
property associated with the fluid within the annulus based on monitoring the
difference between the optical characteristic of the drilling fluid and the optical
characteristic of the fluid within the annulus; and generating a signal to direct a
drilling operation based on the determined property.
17. The method of claim 16, wherein generating the signal to direct the
drilling operation includes geosteering the drilling operation or generating a
monitoring signal to provide advanced warning with respect to a safety condition
of the drilling operation.
18. A machine-readable storage device having instructions stored thereon,
which, when performed by a machine, cause the machine to perform operations,
the operations comprising the method of any of claims 1 to 17.
19. A system comprising:
an optical computation element disposed in a housing, the housing
attachable to a drillstring.
a window in the housing arranged to receive light from exterior to the
housing such that the light is directed from a region, exterior to the drillstring, to
the optical computation element when the housing is mounted on the drillstring;
an analysis unit structured to provide a signal based on an output from
the optical computation element in response to the optical computation element
receiving the light from exterior to the drillstring, the signal provided to direct a
drilling operation based on a property of the region determined from the output
from the optical computation element.
20. The system of claim 19, wherein the system further comprises an optical
source to generate light that is reflected from exterior to the housing such that
the reflected light provides the received light directed to the optical computation
element.
2 . The system of claim 20, wherein the system includes an additional
window structured such that the generated light by the optical source, with the
optical source disposed in the housing, exits the housing to reflect from exterior
to the housing.
22. The system of claim 19, wherein the system includes a probe device
structured to generate a probe light, the probe device physically arranged on the
housing to contact a borehole wall such that probe light passed from the probe
device to the borehole wall provides the received light from exterior to the
housing.
23. The system of claim 22, wherein the probe device is operable to scrap off
material from the borehole wall.
24. The system of any of claims 19 to 24, wherein the system includes
optical detectors arranged relative to the optical computation element to detect
light directed from the optical computation element to the respective optical
detector.
25. The system of claim 24, wherein the arrangement of optical detectors are
coupled with the analysis unit to provide signals to the analysis unit, the analysis
unit structured to determine a difference between a drilling fluid within a
drillstring of a drilling operation and a fluid within an annulus of the drillstring
based on the signals.