Measuring Hookload
Background
[0001] During typical hydrocarbon drilling operations, a drill string, drill bit, and other elements of the
drilling system are suspended in a borehole from a hook at the surface. The load on the hook caused by
the suspended elements (i.e. the "hookload") is measured for a number of purposes, including monitoring
the amount of force being applied by the drill bit to the floor of the borehole, which is referred to as
weight on bit (WOB). Accurate hookload and WOB measurements are important to prolonging the
usable life of the drill bit, among other uses.
Brief Description of the Drawings
[0002] Fig. 1 illustrates a drilling system incorporating aspects of the present disclosure.
[0003] Figs. 2 and 3 illustrate placement of a hookload measurement device in accordance with aspects
of the present disclosure.
[0004] Figs. 4A and 4B illustrate the forces acting on a drill line in accordance with aspects of the present
disclosure.
[0005] Fig. 5 is a perspective view of an example hookload measurement device in accordance with
aspects of the present disclosure.
[0006] Figs. 6-8 are cross-sectional views of example embodiments of hookload measurement devices
in accordance with aspects of the present disclosure.
[0007] Fig. 9 is a cross-sectional view of an example hookload measurement device in accordance with
aspects of the present disclosure.
[0008] Fig. 10 is a flow chart in accordance with aspects of the present disclosure.
[0009] Fig. 11 illustrates an environment in accordance with aspects of the present disclosure.
Detailed Description
[0010] A system for drilling operations (or "drilling system") 5, illustrated in Fig. 1, can include a
drilling rig 10 at the surface 12, supporting a drill string 14. In one or more embodiments, the drill string
14 is an assembly of drill pipe sections which are connected end-to-end through a work platform 16. In
alternative embodiments, the drill string comprises coiled tubing rather than individual drill pipes. In
one or more embodiments, drill bit 18 couples to the lower end of the drill string 14, and through drilling
operations the bit 1 creates a borehole 20 through earth formations 22 and 24.
[001 1] In one or more embodiments, the drilling system 5 includes a drill line 26 to raise and lower the
drill string 14 in the borehole 20. In one or more embodiments, the drill line 26 is spooled on a winch
or draw works 28. In one or more embodiments, the drill line 26 passes from the winch 28 to a crown
block 30. In alternative embodiments, the drilling system is sea based and is mounted on a floating rig.
The drill line passes from the crown block 30 to a traveling block 32 back to the crown block 30 and to
an anchor 34. A hook 36 couples the traveling block 32 to the drillstring 14. The crown block 30 and
the traveling block 32 act as a block-and-tackle device to provide mechanical advantage in raising and
lowering the drillstring 14. In one or more embodiments, the drill line 26 includes a fast line 38 that
extends from the draw works 28 to the crown block 30 and a deadline 40 that extends from the crown
block 30 to the anchor 34. In one or more embodiments, a supply spool 42 stores additional drill line 26
that can be used when the drill line 26 has been in use for some time and is considered worn.
[0012] In one or more embodiments, a hookload measurement device 44 is coupled to the drill line 26
to measure the tension in the drill line 26. In one or more embodiments, signals from the hookload
measurement device 44 are communicably coupled to a processor 46 by a cable 48. In one or more
embodiments, the signals from the hookload measurement device 44 may be communicably coupled to
the processor 46 by one or more wireless communication channels. The processor 46 may be part of an
information handling system or computing device. As used herein, an information handling system or
computer device may comprise a processor and a memory device, such as a non-transitory computer
readable medium, communicably coupled to the processor. The memory device may contain a set of
instructions that, when executed by the processor, cause the processor 46 to perform certain actions or
steps. The set of instructions may comprise a computer program or other software. In certain
embodiments, a non-transitory computer readable medium, such as a CD, DVD, flash drive, etc.,
separate from the information handling system, may contain the set of instruction or computer code.
[0013] The processor 46 may be coupled to a memory device that contains a set of instructions to cause
the processor 46 to receive and process output signals from the hookload measurement device 44 to
determine hookload. An output signal may comprise a voltage or current signal generated by the
measurement device 44, with the amplitude of the voltage or current signal corresponding to the
elongation of the drill line 26. Processing the output signals to determine the hookload may include an
intermediate step of determining an elongation of the drill line 26 using the output signals, as will be
described below. The processor 46 may then use the calculated hookload to, for example, calculate
WOB, which is used to make a variety of decisions about drilling operations.
[0014] In one or more embodiments, one of which is illustrated in Figs. 1, 2, and 3, the hookload
measurement device 44 is coupled to the deadline 40. The deadline 40 is wrapped around a spool (not
shown) in the anchor 34. A set of bolts 202 secure the deadline 40 to the anchor 34 during normal
operations. The bolts 202 can be released for "slip and cut" operations, in which a new length of cable
204 is added to the drill line 26 from the supply spool 42.
[0015] In one or more embodiments, one of which is illustrated in Fig. 3, the hookload measurement
device 44 includes a first cable clamp 302 and a second cable clamp 304. In one or more embodiments,
the first cable clamp 302 and the second cable clamp 304 wrap around and securely clamp the hookload
measurement device 44 to the drill line 26. In one or more embodiments, a first apparatus section 306
is coupled to the first cable clamp 302 and a second apparatus section 308 is coupled to the second cable
clamp 304. In one or more embodiments, the hookload measurement device 44 includes a measuring
device 310 that produces the output signal described above. In one or more embodiments, the measuring
device 310 is coupled to the first apparatus section 306. In one or more embodiments, the measuring
device 310 is coupled to the second apparatus section 308. In one or more embodiments (described in
connection with Figs. 6-9), the measuring device 310 comprises a first measuring device portion that is
coupled to the first apparatus section 306 and a second measuring device portion that is coupled to the
second apparatus section 308. In one or more embodiments, the first measuring device portion and the
second measuring device portion are in at least one of mechanical, optical, and electromagnetic
communication
[0016] In one or more embodiments, at least a portion of the hookload measurement device 44 is
fabricated of light portable material, such as glass fiber reinforced plastic, anodized aluminum, nylon,
DELR N® provided by E.I. du Pont de Nemours and Company (a thermoplastic also sold under other
names such as CELCON® provided by Celanese Corporation, DURACON® provided by Polyplastics
Co., Ltd. and HOSTAFORM® provided by Hoechst Aktiengesellschaft), ABS (Acrylonitrile butadiene
styrene - a thermoplastic), or HDPE (High Density Polyethylene).
[0017] In one or more embodiments, the first apparatus section 306 and the second apparatus section
308 move relative to each other when affixed to the drill line 26 but are held together so that they are
easily portable, as described below in connection with Figs. 4-6. In one or more embodiments, the first
apparatus section 306 and the second apparatus section 308 are clamped to the drill line 26 using the first
cable clamp 302 and the second cable clamp 304, respectively, in a place that is easily reached, which,
in one or more embodiments, is above the anchor 34.
[00 18] In one or more embodiments, the output signal produced by the measuring device 310 is related
to the elongation of a length of drill line 26, e.g., the distance "d" between the first apparatus section 306
and the second apparatus section 308 (reference points other than those shown in Fig. 3 could be used).
[0019] An equation for elongation is derived as follows with reference to Figs. 4A and 4B. Fig. 4A
shows a model of the drill line 26 restrained at one end by the anchor 34 (represented as a box in Figs.
4A and 4B and more realistically illustrated in Fig. 2) in which the drill line 26 is treated as a column.
It is believed that the crown block 30 and traveling block 32 do not affect the analysis and they are not
shown. The drill line 26 has an initial length of Lo and in Fig. 4A has no force exerted on its lower end
(at x = 0), meaning that the drill line 26 is unloaded or is carrying a standby load. The first apparatus
section 306 is attached to the drill line 26 at a location x = li and the second apparatus section 308 is
attached to the drill line 26 at a location x = .
[0020] In Fig. 4B, a load Pi is applied to the drill line 26 (e.g., the drill line 26 begins to lower the drill
string 14 into the borehole 20). The drill line 26 stretches to have a length Li and the first apparatus
section 306 is attached to the drill line 26 at a location x = and the second apparatus section 308 is
attached to the drill line 26 at a location x = .
[0021] The amount of elongation that can be detected by the first apparatus section 306 and the second
apparatus section 308 is:
d = 3 - - - 1 (1)
[0022] The elongation value can be determined using Hooke's law as follows:
1
AE
(2)
where
A is the cross-sectional area of the drill line 26, which is assumed to be a constant, and
E is the elastic modulus of the material from which the drill line 26 is made.
Note that equation (2) ignores all elongations other than elastic elongation. That is, it is assumed that
inelastic elongation, elongation due to rotation or wear, elongation due to thermal expansion and
contraction, etc. are minimal.
[0023] Since Pi, A, and E are constants, equation (2) can be rewritten as:
d = & d x (3)
AE J '
Solving the integral and evaluating it over the range of integration produces the following:
Solving for Pi:
[0024] Examining equation (5), it can be seen that hookload P i is proportional to the ratio of the change
in distance between the first apparatus section 306 and the second apparatus section 308 caused by the
load (i.e., d or "loaded distance") and the unloaded distance between the first apparatus section 306 and
the second apparatus section (i.e., / - h).
[0025] In one or more embodiments, the unloaded distance between the first apparatus section 306 and
the second apparatus section (i.e., / - li) is adjusted according to the measurement technique used (e.g.,
the techniques described in connection with Figs. 6-8 below), the accuracy desired from the measurement
device 310, and the convenience of attaching the measuring device 310 to the drill line 26. As can be
seen from equation (5), adjusting // - to a low value will make the calculation of P i more sensitive to
the measurement of d than adjusting / - h to a high value.
[0026] In one or more embodiments, the measuring device 310 does not put any stress or strain on the
drill line 26. In particular, the measuring device does not crimp or otherwise deform the drill line 26.
[0027] In one or more embodiments, the measuring device 310 can use fiber optic light, laser, inductive
components or variable linear transformers. In one or more embodiments, an output signal from the
measurement device corresponding to the elongation of the drill line 26 is received the processor 46. As
described above, an output signal may comprise a voltage or current signal generated by the measuring
device 310, with the amplitude of the voltage or current signal corresponding to the elongation of the
drill line 26. Once received, the processor 46 may calculate the elongation and hook-load using the
output signal, or may transmit or otherwise provide the received output signal and/or calculated
elongation to a second information handling system that may calculate the hookload. In one or more
embodiments, the processor 46 or the second information handling system may perform derivative
calculations using the calculated hookload which will benefit from the accuracy of the hookload
measuring device 44 and hence will improve the drilling operation.
[0028] In one or more embodiments, shown in Fig. 5, the first apparatus section 306 of the hookload
measurement device 44 includes a sensor mount 502, a transducer mount 504, and a rod guide 506. In
one or more embodiments, the sensor mount 502 is coupled to the first cable clamp 302, which is shown
in Fig. 5 in two parts for stability of mounting to the drill line 26. In one or more embodiments, the
transducer mount 504 is fixedly coupled to the sensor mount 502. In one or more embodiments, the rod
guide 506 is slidably coupled to the transducer guide 506, which allows the rod guide 506 to slide into
and out of the transducer guide in a telescope-like manner. In one or more embodiments, a rod 508 is
slidably coupled to the rod guide 506. In one or more embodiments, a rod nut 510 tightens to secure the
rod 508 in place. In one or more embodiments, the position of the rod 508 relative to the rod guide 506
is adjustable by loosening the rod nut 510, sliding the rod 508 into or out of the rod guide 506 to the
desired location, and tightening the rod nut 510.
[0029] Fig. 6 illustrates a cross-sectional view of one or more embodiments of the hookload
measurement device 44, in which the sensor mount 502, the transducer guide 504, and rod guide 506 are
shown in dashed lines to allow the interior workings to be seen. In one or more embodiments, the
hookload measurement device 44 includes a linear transducer 602. In one or more embodiments, the
linear transducer 602 includes a support rod 604 that is coupled to a clevis bracket 606, which is coupled
to the first cable clamp 302. In one or more embodiments, the linear transducer 602 includes a transducer
rod 608 that is coupled to the rod 506. The linear transducer 602 may be communicably coupled to a
processor, such as through the cable 48, although that connection is not shown for simplicity.
[0030] As illustrated in Fig. 6 :
• the first apparatus section 306 can include the clevis bracket 606, the sensor mount 502, and the
transducer guide 504, and can be coupled to the first cable clamp 302,
• the second apparatus section 308 can include the rod guide 506, and can be coupled to the second
cable clamp 304,
• a first measuring device portion 614 can include the linear transducer 602, the support rod 604,
and the transducer rod 608, which can be coupled to the first apparatus section 306, and
• a second measuring device portion 616 can include the rod 508, and can be coupled to the second
apparatus section 308.
[0031] In operation, as the drill line 26 elongates or contracts, the distance between the first cable clamp
302 and the second cable clamp 304 changes. The change in position of the first cable clamp 302 relative
the second cable clamp 304 causes the rod guide 506 to move relative to the sensor mount 502. Since
the rod 508 is fixed to the rod guide 506 by the rod nut 510, rod 508 moves the transducer rod 608 in
and out of the linear transducer 602. The linear transducer 602 detects the movement of the transducer
rod 608 and produces a signal that is reflective of that movement. The resulting signal is transmitted to
the processor 46 by the cable 48.
[0032] Fig. 7 illustrates aspects of the hookload measurement device 44, in which the sensor mount 502,
the transducer guide 504, and rod guide 506 are shown in dashed lines to allow the interior workings to
be seen, as in Fig. 6 . In one or more embodiments, the hookload measurement device 44 includes an
opto-reflective sensor 702. In one or more embodiments, the hookload measurement device 44 also
includes a reflector 704 coupled to the rod 508.
[0033] As illustrated in Fig. 7 :
• the first apparatus section 306 can include the sensor mount 502 and the transducer guide 504,
and can be coupled to the first cable clamp 302,
• the second apparatus section 308 can include the rod guide 506, and can be coupled to the second
cable clamp 304,
• a first measuring device portion 706 can include the opto-reflective sensor, and can be coupled
to the first apparatus section 306, and
· a second measuring device portion 708 can include the rod 508 and the reflector 704, and can be
coupled to the second apparatus section 308.
[0034] In operation, as the drill line 26 elongates or retracts, the distance between the first cable clamp
302 and the second cable clamp 304 changes. The change in position of the first cable clamp 302 relative
the second cable clamp 304 causes the rod guide 506 to move relative to the sensor mount 502. Since
the rod 508 is fixed to the rod guide 506 by the rod nut 510, rod 508 moves the reflector 704 with respect
to the opto-reflector 702. The opto-reflector 702 emits an optical signal, such as a laser beam, that
reflects from the reflector 704 back to the opto-reflective sensor 702. The opto-relective sensor 702
determines the distance between the opto-reflective sensor 702 and the reflector 704 from the transit
time of the optical signal. The determined distance is transmitted to the processor 46 by the cable 48
(not shown in Fig. 7).
[0035] Fig. 8 illustrates a one or more aspects of the hookload measurement device 44, in which the
sensor mount 502, the transducer guide 504, and rod guide 506 are shown in dashed lines to allow the
interior workings to be seen. In one or more embodiments, the hookload measurement device 44
includes an antenna 802 supported from a bracket 804, which is coupled to the first cable clamp 302,
through an antenna support 806. In one or more embodiments, the hookload measurement device 44
includes a target 808 that is coupled to the rod 508, so that the target 808 moves relative to the antenna
802 as the first cable clamp 302 moves relative to the second cable clamp 304 as the drill line 26
elongates or contracts. In one or more embodiments, the target 808 is offset from the antenna 802, as
shown in Fig. 9 . In one or more embodiments, the antenna 802 and the target 808 are an inductive linear
transducer, which inductively measures the position of the target 808 relative to the antenna 802. In one
or more embodiments, the antenna 802 provides the relative position to the processor 46 via the cable
46 (not shown in Fig. 8).
[0036] As shown in Figs. 8 and 9 :
• the first apparatus section 306 can include the bracket 804, the antenna support 806, the sensor
mount 502, and the transducer guide 504, and can be coupled to the first cable clamp 302,
• the second apparatus section 308 can include the rod guide 506, and can be coupled to the second
cable clamp 304,
• a first measuring device portion 810 can include the antenna 802, and can be coupled to the first
apparatus section 306, and
• a second measuring device portion 812 can include the rod 508 and the target 808, and can be
coupled to the second apparatus section 308.
[0037] In one or more embodiments (not shown in the figures), the hookload measurement device 44
includes a white light interferometer to measure the distance between the first apparatus section 306 and
the second apparatus section 308.
[0038] In one or more embodiments (not shown in the figures), the hookload measurement device 44
includes two bundles of optical fibres. In one or more embodiments, light dispersed from one bundle is
sensed by the other and reflectometry of the sensed light is analyzed to measure the distance between
the first apparatus section 306 and the second apparatus section 308.
[0039] In one or more embodiments (not shown in the figures), the hookload measurement device 44
includes a solenoid coil, having a longitudinal axis and a bore through the longitudinal axis, coupled to
the first apparatus section 306 and a ferrous rod coupled to the second apparatus section 308. In one or
more embodiments, the ferrous rod extends into the bore of the solenoid coil by an amount related to the
distance between the first apparatus section and the second apparatus section. In one or more
embodiments, the inductance of the solenoid coil is varied by the amount of the ferrous rod that extends
into its bore. In one or more embodiments, the inductance is measured to determine d.
[0040] In one or more embodiments of use, for example as illustrated in Fig. 10, the drill line 26 is
unloaded or loaded with a "standby load" (block 1002), i.e., by uncoupling the drill line 26 from the drill
string 14 or engaging a structure on the drilling rig (not shown) to perform this function. In one or more
embodiments, the hookload measurement device is attached to the drill line 26 (block 1004) as shown,
for example in Figs. 2, 3, and 5-9. In one or more embodiments, the initial measurement distance (i.e.,
/ - in equation (5)) is adjusted as discussed above (block 1006). In one or more embodiments, the
drill line is loaded (block 1008), for example by coupling the drill line 26 to the drill string 14. In one
or more embodiments, the loaded measurement distance (i.e., d in equation (5)) is measured. In one or
more embodiments, hookload (Pi) is calculated using equation (5).
[0041] In one or more embodiments, shown in Fig. 11, the hookload measurement device 44 is
controlled by software in the form of a computer program on a non-transitory computer readable media
1105, such as a CD, a DVD, a USB drive, a portable hard drive or other portable memory. In one or
more embodiments, a processor 1110, which may be the same as or included in the processor 46, reads
the computer program from the computer readable media 1105 through an input/output device 1115 and
stores it in a memory 11 0 where it is prepared for execution through compiling and linking, if necessary,
and then executed. In one or more embodiments, the system accepts inputs through an input/output
device 1115, such as a keyboard or keypad, mouse, touchpad, touch screen, etc., and provides outputs
through an input/output device 1115, such as a monitor or printer. In one or more embodiments, the
system stores the results of calculations in memory 1120 or modifies such calculations that already exist
in memory 1120.
[0042] In one or more embodiments, the results of calculations that reside in memory 1120 are made
available through a network 1125 to a remote real time operating center 1130. In one or more
embodiments, the remote real time operating center 1130 makes the results of calculations available
through a network 1135 to help in the planning of oil wells 1140 or in the drilling of oil wells 1140.
[0043] References in the specification to "one or more embodiments", "one embodiment", "an
embodiment", "an example embodiment", etc., indicate that the embodiment described may include a
particular feature, structure, or characteristic, but every embodiment may not necessarily include the
particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the
same embodiment. Further, when a particular feature, structure, or characteristic is described in
connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art
to effect such feature, structure, or characteristic in connection with other embodiments whether or not
explicitly described.
[0044] Embodiments of the invention include features, methods or processes that may be embodied
within machine-executable instructions provided by a machine-readable medium. A computer -readable
medium includes any mechanism which provides (i.e., stores and/or transmits) information in a form
accessible by a machine (e.g., a computer, a network device, a personal digital assistant, manufacturing
tool, any device with a set of one or more processors, etc.). In an exemplary embodiment, a computerreadable
medium includes non-transitory volatile and/or non-volatile media (e.g., read only memory
(ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash
memory devices, etc.), as well as transitory electrical, optical, acoustical or other form of propagated
signals (e.g., carrier waves, infrared signals, digital signals, etc.).
[0045] Such instructions are utilized to cause a general or special purpose processor, programmed with
the instructions, to perform methods or processes of the embodiments of the invention. Alternatively,
the features or operations of embodiments of the invention are performed by specific hardware
components which contain hard-wired logic for performing the operations, or by any combination of
programmed data processing components and specific hardware components. One or more embodiments
of the invention include software, data processing hardware, data processing system-implemented
methods, and various processing operations, further described herein.
[0046] One or more figures show block diagrams of systems and apparatus for a system for monitoring
hookload, in accordance with one or more embodiments of the invention. One or more figures show flow
diagrams illustrating operations for monitoring hookload, in accordance with one or more embodiments
of the invention. The operations of the flow diagrams are described with references to the
systems/apparatus shown in the block diagrams. However, it should be understood that the operations of
the flow diagrams could be performed by embodiments of systems and apparatus other than those
discussed with reference to the block diagrams, and embodiments discussed with reference to the
systems/apparatus could perform operations different than those discussed with reference to the flow
diagrams.
[0047] In view of the wide variety of permutations to the embodiments described herein, this detailed
description is intended to be illustrative only, and should not be taken as limiting the scope of the
invention. What is claimed as the invention, therefore, is all such modifications as may come within the
scope and spirit of the following claims and equivalents thereto. Therefore, the specification and
drawings are to be regarded in an illustrative rather than a restrictive sense.
[0048] The word "coupled" herein means a direct connection or an indirect connection.
[0049] The text above describes one or more specific embodiments of a broader invention. The
invention also is carried out in a variety of alternate embodiments and thus is not limited to those
described here. The foregoing description of an embodiment of the invention has been presented for the
purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to
the precise form disclosed. Many modifications and variations are possible in light of the above teaching.
It is intended that the scope of the invention be limited not by this detailed description, but rather by the
claims appended hereto.
Claims
What is claimed is:
1. An apparatus comprising:
a first cable clamp;
a first apparatus section coupled to the first cable clamp;
a second cable clamp;
a second apparatus section coupled to the second cable clamp and slidably coupled to the first
apparatus section;
a first measuring device portion coupled to the first apparatus section;
a second measuring device portion coupled to the second apparatus section;
wherein the first measuring device portion and the second measuring device portion are in at least
one of mechanical, optical, and electromagnetic communication.
2. The apparatus of claim 1 wherein:
the first measuring device portion comprises:
a linear transducer coupled to the first apparatus section; and
a transducer rod coupled to the linear transducer, wherein the transducer rod is movable
relative to the first apparatus section;
wherein the linear transducer senses a position of the transducer rod relative to the first apparatus
section; and
wherein a relative movement between the first apparatus section and the second apparatus section
causes the transducer rod to move relative to the first apparatus section.
3. The apparatus of claim 1 wherein:
the second measuring device portion comprises a reflector coupled; and
the first measuring device portion comprises an opto-reflective sensor;
wherein the opto-reflective sensor senses a distance between the opto-reflective sensor and the
reflector.
4. The apparatus of claim 1 wherein:
the first measuring device portion comprises an antenna; and
the second measuring device portion comprises a target;
wherein the antenna detects the position of the target inductively.
5. The apparatus of claim 1 wherein the measuring device comprises:
the first measuring device portion comprises a solenoid coil comprising:
a longitudinal axis, and
a bore through the longitudinal axis;
the second measuring device portion comprises a ferrous rod;
wherein the ferrous rod extends into the bore of the solenoid coil by an amount related to the
distance between the first apparatus section and the second apparatus section.
6. The apparatus of claim 1 wherein the distance between the first apparatus section and the second
apparatus section is measured using a technique selected from the group consisting of:
measuring interference in light traveling between the first apparatus section and the second
apparatus section;
measuring a transit time of light between the first apparatus section and the second apparatus
section;
measuring an inductance of a solenoid coil in the first apparatus section as affected by a distance
a rod coupled to the second apparatus section extends into the coil; and
measuring an interaction between a first coil coupled to the first apparatus section and a second
coil coupled to the second apparatus section.
7. The apparatus of claim 1 further comprising:
a processor coupled to and receiving an output signal from a measuring device, wherein the
measuring device comprises at least one of the first measuring device portion and the
second measuring device portion.
8. A method comprising:
measuring, with a drill line unloaded, an unloaded distance between:
a first apparatus section coupled to the drill line at a first point on the drill line, and
a second apparatus section coupled to the drill line at a second point on the drill line;
measuring, with a drill-string load on the drill line, a loaded distance between the first apparatus
section and the section apparatus section;
computing a hookload using the unloaded distance and the loaded distance.
9. The method of claim 8 further comprising:
unloading the drill line;
coupling the first apparatus section to the drill line at the first point on the drill line; and
coupling the second apparatus section to the drill line at the second point on the drill line.
10 . The method of claim 8 wherein measuring comprises using a technique selected from the group
consisting of:
measuring interference in light traveling between the first apparatus section and the second
apparatus section;
measuring a transit time of light between the first apparatus section and the second apparatus
section;
measuring a position of a transducer rod in a linear transducer;
measuring an inductance of a solenoid coil in the first apparatus section as affected by a distance
a rod coupled to the section apparatus section extends into the coil; and
measuring an interaction between a first coil coupled to the first apparatus section and a second
coil coupled to the second apparatus section.
11. The method of claim 8 wherein computing the hookload comprises:
calculating:
P = A E -
where
P i is the hookload,
A is a cross-section area of the drill line,
E is an elastic modulus of a material from which the drill line is made,
- is the unloaded distance, and
d is the loaded distance.
1 . A non-transitory computer readable storage medium, on which is recorded a computer program
comprising executable instructions that, when executed, cause a processor to perform a method
comprising:
determining, based on a first output signal from a measurement device and with a drill line
unloaded, an unloaded distance between:
a first apparatus section coupled to the drill line at a first point on the drill line, and
a second apparatus section coupled to the drill line at a second point on the drill line;
determining, based on a second output signal from the measurement device and with a drill-string
load on the drill line, a loaded distance between the first apparatus section and the second
apparatus section; and
computing a hookload using the unloaded distance and the loaded distance.
13. The computer program of claim 13 wherein computing the hookload comprises
calculating:
P = A E -
where
P i is the hookload,
A is a cross-section area of the drill line,
E is an elastic modulus of a material from which the drill line is made,
- is the unloaded distance, and
d is the loaded distance.
14. A system comprising:
a drilling system comprising a drilling line;
a first apparatus section coupled to the drill line at a first point on the drill line,
a second apparatus section coupled to the drill line at a second point on a drill line;
a processor communicatively coupled to a memory; and
a computer program comprising executable instructions stored on the memory that, when
executed, cause the processor to perform a method comprising:
determining, based on a first output signal from a measurement device and with a drill
line unloaded, an unloaded distance between the first apparatus section and the
second apparatus section coupled to the drill line;
determining, based on a second output signal from the measurement device and with a
drill-string load on the drill line, a loaded distance between the first apparatus
section and the section apparatus section; and
computing a hookload using the unloaded distance and the loaded distance.
15. The apparatus of claim 14 wherein the measuring device comprises
a first measuring device portion coupled to the first apparatus section; and
a second measuring device portion coupled to the second apparatus section.
16. The apparatus of claim 14 wherein the measuring device comprises:
a linear transducer coupled to the first apparatus section; and
a transducer rod coupled to the linear transducer, wherein the transducer rod is movable relative
to the first apparatus section;
wherein the linear transducer senses a position of the transducer rod relative to the first apparatus
section; and
wherein a relative movement between the first apparatus section and the second apparatus section
causes the transducer rod to move relative to the first apparatus section.
17. The apparatus of claim 14 wherein the measuring device comprises:
a reflector coupled to the second apparatus section; and
an opto-reflective sensor coupled to the first apparatus section;
wherein the opto-reflective sensor senses a distance between the opto-reflective sensor and the
reflector.
18. The apparatus of claim 14 wherein the measuring device comprises:
an antenna coupled to the first apparatus section;
a target coupled to the second apparatus section;
wherein the antenna detects the position of the target inductively.
19. The apparatus of claim 14 wherein the measuring device comprises:
a solenoid coil coupled to the first apparatus section;
the solenoid coil comprising:
a longitudinal axis, and
a bore through the longitudinal axis;
a ferrous rod coupled to the second apparatus section;
wherein the ferrous rod extends into the bore of the solenoid coil by an amount related to the
distance between the first apparatus section and the second apparatus section.