U.S. patent application number 14/285475 was filed with the patent office on 2014-09-11 for system and method for obtaining load measurements in a wellbore.
This patent application is currently assigned to Schlumberger Technology Corporation. The applicant listed for this patent is Schlumberger Technology Corporation. Invention is credited to Carlos Foinquinos Bocco, Michael H. Kenison, Robin Mallalieu, Richard Morrison, Jose Vidal Noya, Robert Van Kuijk.
Application Number | 20140251602 14/285475 |
Document ID | / |
Family ID | 40453232 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140251602 |
Kind Code |
A1 |
Kenison; Michael H. ; et
al. |
September 11, 2014 |
System And Method For Obtaining Load Measurements In A Wellbore
Abstract
A technique for determining conditions downhole in a well,
particularly load conditions acting on a well tool, e.g. a bottom
hole assembly. The loads acting on a bottom hole assembly or other
well tool during a well related operation are measured. Load data
is collected and may be transmitted uphole in real time for
evaluation at a surface control unit. Based on the load data and
other possible data related to the downhole operation, corrective
actions can be taken to improve the operation.
Inventors: |
Kenison; Michael H.;
(Richmond, TX) ; Morrison; Richard; (Sugar Land,
TX) ; Van Kuijk; Robert; (Le Plessis Robinson,
FR) ; Noya; Jose Vidal; (Dubai, AE) ; Bocco;
Carlos Foinquinos; (Katy, TX) ; Mallalieu; Robin;
(Sugar Land, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schlumberger Technology Corporation |
Sugar Land |
TX |
US |
|
|
Assignee: |
Schlumberger Technology
Corporation
Sugar Land
TX
|
Family ID: |
40453232 |
Appl. No.: |
14/285475 |
Filed: |
May 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12113437 |
May 1, 2008 |
8733438 |
|
|
14285475 |
|
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60973211 |
Sep 18, 2007 |
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Current U.S.
Class: |
166/250.01 ;
166/66 |
Current CPC
Class: |
E21B 44/00 20130101;
E21B 47/007 20200501; E21B 47/00 20130101 |
Class at
Publication: |
166/250.01 ;
166/66 |
International
Class: |
E21B 47/00 20060101
E21B047/00; E21B 47/12 20060101 E21B047/12 |
Claims
1-29. (canceled)
30. A method of facilitating a downhole operation, comprising:
disposing a bottom hole assembly via a conveyance into a wellbore,
wherein the tool comprises a housing defining a flow passage
therethrough for accommodating fluid flow through the bottom hole
assembly, a seal structure formed as a pressure compensating
piston, wherein fluid pressure in an annulus of the wellbore does
not impart a net axial force on the pressure compensating piston,
and a load cell disposed and sealed in an atmospheric chamber,
wherein the housing and the pressure compensating piston cooperate
to isolate the load cell from undesirable loading effects, and;
performing a downhole operation with the conveyance and bottom hole
assembly in the wellbore; measuring loading with the load cell
during the downhole operation, transmitting load data uphole in
real-time via telemetry via an optical fiber deployed along a
tubular conveyance; evaluating the load data at a surface control
unit; and making a corrective action downhole based on the load
data.
31. The method as recited in claim 1, wherein a working surface of
the pressure compensating piston is not in direct contact with
fluid in the annulus of the wellbore.
32. The method as recited in claim 30, wherein measuring loading
comprises measuring loads acting on a bottom hole assembly during a
milling operation.
33. The method as recited in claim 30, wherein measuring loading
comprises measuring loads during the setting of a packer.
34. The method as recited in claim 30, wherein measuring loading
comprises measuring loads during actuation of a downhole tool.
35. The method as recited in claim 30, wherein measuring loading
comprises measuring loads during a fishing operation.
36. The method as recited in claim 30, wherein measuring loading
comprises measuring loads to ensure excess detrimental loading is
not incurred at a given downhole tool.
37. The method as recited in claim 30, wherein measuring loading
comprises measuring loads during a perforating operation.
38. The method as recited in claim 30, wherein measuring loading
comprises measuring comprises measuring a compressive load, a
tensile load, a torque load, and/or a shock load.
39. A method, comprising: detecting loading of downhole equipment
in a wellbore during a coiled tubing operation by utilizing a load
sub assembly having a housing, a pressure compensating piston, a
load cell and a flow passage for accommodating fluid flow from the
coiled tubing and through the load sub assembly, wherein the load
cell is disposed in and surrounded by a sealed atmospheric chamber
and isolated from undesirable loading effects that are both
internal and external to the load sub assembly, wherein fluid in an
annulus of the wellbore does not transfer a net axial force to the
load sub assembly through the pressure compensating piston; and
using telemetry to transmit load data to a surface control unit in
real-time by transmitting load data via optical fiber deployed
within a fiber optic tether within the coiled tubing.
40. The method as recited in claim 39, wherein detecting loading
comprises detecting compressive forces, tensile forces, torque,
and/or shock forces acting on a downhole equipment.
41. The method as recited in claim 39, further comprising utilizing
additional sensors to detect other desired downhole parameters; and
transmitting additional sensor data to the surface control unit in
real-time.
42. The method as recited in claim 39, wherein the internal loading
effects comprise at least loading effects from the flow of fluid
through the load sub assembly.
43. The method as recited in claim 39, wherein the coiled tubing
operation comprises at least one of a drilling operation, a
treatment operation, a tool actuation operation, a measurement
operation, and a fishing operation.
44. A system for detecting loads downhole, comprising: a coiled
tubing assembly comprising at least a load sub assembly having a
substantially unobstructed flow through passage for treatment fluid
downstream of the load sub assembly, the load sub assembly
comprising: a housing; a pressure compensating piston; and a load
cell, wherein the load cell comprises a load sensor mounted in a
sealed atmospheric chamber and wherein the housing and the pressure
compensating piston cooperate to isolate the load cell from
undesirable loading effects, wherein the loading effects comprise
at least loading effects from the flow of fluid through the load
sub assembly, wherein fluid pressure in an annulus of the wellbore
does not impart a net axial force on the pressure compensating
piston.
45. The system as recited in claim 44, wherein the load cell is
isolated from undesirable loading effects internal to the load sub
assembly, the internal loading effects comprising at least the
loading effects from the flow of fluid therethrough.
46. The system as recited in claim 44, wherein the load cell is
isolated from undesirable loading effects external to the load sub
assembly.
47. The system as recited in claim 44, wherein the load sub
assembly further comprises an electronic assembly constructed to
relay load data uphole in real-time via fiber optic telemetry.
48. The system as recited in claim 44, wherein the load sub
assembly further comprises a plurality of keys positioned to
transfer loading to the housing from the load cell.
49. The system as recited in claim 44, further comprising a
downhole tool bus for providing communication and/or power to a
device below the sub assembly.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present document is based on and claims priority under
35 USC 119(e) to U.S. Provisional Application Ser. No. 60/973,211,
filed Sep. 18, 2007.
BACKGROUND
[0002] A variety of hardware is used downhole to accomplish many
types of well related operations. The hardware, e.g. well tool,
often is delivered downhole as part of a tool string used to
perform the desired operation. For example, well tools can be
delivered downhole to perform drilling operations, treatment
operations, tool actuation operations, measurement operations,
fishing operations and other well related operations. During use
downhole, the hardware can be subjected to a variety of loads,
including compression loads, tension loads, torsion loads, shock
loads, and vibration loads. If the loading becomes excessive,
damage can be incurred by the downhole hardware.
[0003] Attempts have been made to detect and measure loading that
occurs in a downhole environment. For example, downhole sensor
packages with local data storage have been used to measure loads
experienced by a downhole tool string during coiled tubing
operations. The locally stored data is then retrieved for post job
analysis. However, the delayed access to data limits the usefulness
of the system with respect to making adjustments to reduce
detrimental loading during the well related operation. There is no
capability for optimizing performance through real time control.
Other attempts have been made to send load data to the surface, but
available systems have tended to be limited in data transfer
capacity and accuracy. Other drawbacks associated with existing
systems include relatively large outside diameters that restrict
the usefulness of such systems in a variety of downhole
operations.
SUMMARY
[0004] In general, the present invention provides a system and
method for determining conditions at a well tool used in a downhole
well related operation. The system and method comprise measuring
loading on the well tool during a well related operation at a
downhole position. Load data may be transmitted uphole for
evaluation at a surface control unit. Although some applications
may use locally stored data, other applications benefit from the
transmission of some or all data uphole in real time. Based on the
downhole operational data obtained, corrective actions can be taken
to improve the operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Certain embodiments of the invention will hereafter be
described with reference to the accompanying drawings, wherein like
reference numerals denote like elements, and:
[0006] FIG. 1 is a schematic front elevation view of a well system
that can obtain and utilize load data, according to an embodiment
of the present invention;
[0007] FIG. 2 is a front elevation view of a load detection
assembly for use in the well system illustrated in FIG. 1,
according to an embodiment of the present invention;
[0008] FIG. 3 is a cross-sectional view taken generally along the
axis of the load detection assembly illustrated in FIG. 2,
according to an embodiment of the present invention;
[0009] FIG. 4 is a cross-sectional view similar to that of FIG. 3
but showing slightly different features, according to an embodiment
of the present invention;
[0010] FIG. 5 is a cross-sectional view of a portion of the load
detection assembly illustrating a compressive load path, according
to an embodiment of the present invention;
[0011] FIG. 6 is a cross-sectional view of a portion of the load
detection assembly illustrating a tensile load path, according to
an embodiment of the present invention;
[0012] FIG. 7 is a front elevation view of the load detection
assembly with a portion of the assembly removed to illustrate
torque keys, according to an embodiment of the present
invention;
[0013] FIG. 8 is a cross-sectional view of a portion of the load
detection assembly illustrating a strain gauge mounting area,
according to an embodiment of the present invention;
[0014] FIG. 9 is a cross-sectional view of an alternate load
detection assembly, according to an alternate embodiment of the
present invention; and
[0015] FIG. 10 is an illustration of one example of keys that can
be used to transfer torque loads if non-rotating tool connections
are used, according to an alternate embodiment of the present
invention.
DETAILED DESCRIPTION
[0016] In the following description, numerous details are set forth
to provide an understanding of the present invention. However, it
will be understood by those of ordinary skill in the art that the
present invention may be practiced without these details and that
numerous variations or modifications from the described embodiments
may be possible.
[0017] The present invention generally relates to a system and
method for detecting, measuring, and managing loads incurred by
downhole equipment during various well related operations. The load
data can be obtained in real time to facilitate a greater
understanding of those loads and to enhance the ability to take
corrective action. For example, the load data obtained downhole can
be transmitted to a surface control unit for analysis and
determination of appropriate corrective action. The data also can
be used to synchronize the operational equipment downhole with the
surface control unit. In some applications, responses to the load
data can be automated via the surface control unit so that
appropriate corrective actions are automatically taken to improve
the well operation.
[0018] The system and methodology described herein can be used to
detect and measure a variety of load forces to which a well tool
may be subjected during a downhole operation. For example, load
forces related to vibration forces, compressive forces, tensile
forces, torque forces, shock forces and other types of load related
forces can be detected, measured and transmitted uphole in real
time. Depending on the downhole operation, other well related
parameters also can be measured, and data on those parameters can
be transmitted to the surface control unit. By way of example, some
of these other parameters may include trajectory, reach, friction,
drilling speed, motion, pressure, temperature and other parameters
that can affect specific downhole operations.
[0019] Referring generally to FIG. 1, one embodiment of a system 20
is illustrated as deployed in a wellbore 22. The system 20 is
representative of a variety of well systems used in carrying out
many types of well related operations, as explained in greater
detail below. Additionally, system 20 is designed to detect,
measure and transmit load related data from a downhole location to,
for example, a surface location for analysis and use in improving
the specific well operation being performed. In the application
illustrated, the system is designed to transmit this load data in
real time to enable immediate corrective action during the downhole
operation. Additional parameter related data also can be detected,
measured and transmitted in real time to facilitate the
analysis.
[0020] In the example illustrated, system 20 comprises a well tool
24 that may be deployed to a desired location in wellbore 22 via a
conveyance 26, such as a coiled tubing conveyance, drill string,
jointed pipe, or other conveyance. Well tool 24 is engaged with a
load detection sub assembly 28 designed to detect one or more types
of loading that can be incurred by well tool 24. Sub assembly 28
sends load related data uphole to a surface control unit 30, such
as a computer-based control unit. The data is sent uphole via a
communication line 32, such as a fiber optic line. In the
embodiment illustrated, load detection sub assembly 28 is connected
to conveyance 26 via a connector assembly 34 which may be a "smart"
connector assembly able to convert data from sub assembly 28 to a
suitable format for transmission along a fiber optic communication
line. Suitable electronics for transmitting data uphole in real
time can be located in connector assembly 34, sub assembly 28, a
combination of the two assemblies, or at other suitable locations
along the tool string.
[0021] Load detection sub assembly 28 can be designed to detect one
or more of a variety of load forces, e.g. compressive loads,
tensile loads, torque loads, shock loads and other loads to which
well tool 24 is susceptible. Additionally, a variety of sensors 36
also can be deployed downhole to detect and measure other well
related parameters. Data on the additional parameters also can be
sent uphole to surface control unit 30 via communication line 32 or
via other suitable communication lines, including hard wired and
wireless communication lines. By way of example, sensors 36 may
comprise accelerometers, inclinometers, gamma ray sensors, gyros,
pressure sensors, casing collar locators, and temperature
sensors.
[0022] In many applications, the use of one or more fiber optic
communication lines 32 greatly facilitates the real time transfer
of data from load detection sub assembly 28 and potentially other
sensors 36. Fiber optic communication lines 32 also can be combined
with the conveyance 26, e.g. coiled tubing conveyance 26, and
deployed, for example, along the interior of the coiled tubing or
within a wall of the coiled tubing. In a specific example, the
fiber optic communication line 32 and coiled tubing conveyance 26
have been combined and are commercially available from Schlumberger
Corporation. In one embodiment, coiled tubing 26, fiber optic
communication line 32 and connector assembly 34 are combined as a
fiber optic telemetry platform available from Schlumberger
Corporation. The platform can be used to sense a variety of
wellbore parameters, e.g. temperature, annular pressure, applied
pressure, and data on those parameters is transmitted to surface
control unit 30 via fiber optic communication line 32. In this
embodiment, the load detection sub assembly 28 can be mounted to
the bottom of the measurement platform as a modular extension.
[0023] The measurement platform generally comprises coiled tubing
with a fiber optic tether deployed along an interior of the coiled
tubing. The fiber optic tether has one or more optical fibers
located inside a protective tube which may be formed of a metallic
material or other material having suitable properties. The coiled
tubing and the fiber optic tether have suitable upper and lower
terminations or connections that allow fluid to be introduced into
the coiled tubing and directed along the interior of the coiled
tubing. However, different arrangements of optical fibers can be
deployed in a variety of ways along coiled tubing, production
tubing or other appropriate conveyances.
[0024] In the example illustrated, system 20 is deployed in a
generally vertical wellbore that extends downwardly from a wellhead
38 positioned at a surface location 40. However, system 20 and its
load detection capabilities can be utilized in a variety of wells,
including horizontal wells and other types of deviated wells. The
system 20 also can be used in many types of environments and
applications, including land based applications and subsea
applications. The type of well tool or tools 24 used in cooperation
with load detection sub assembly 28 may vary substantially
depending on downhole operation. The illustrated well tool 24 is
representative of a variety of well tools that are run downhole to
perform one or more selected, well related operations.
[0025] For example, well tool 24 may comprise a bottom hole
assembly used in a milling operation. In this example, the bottom
hole assembly comprises a bit driven by a motor that operates via
pressure applied with fluid flowing through conveyance 26 which is
in the form of a tubing. The load detection sub assembly 28 can be
used to detect load changes indicative of bit stalling. Stalling
causes the overall rate of penetration to decrease because the
operator must lift off and reposition the bit to begin milling
again. Stalling also reduces bit life as well as the life of the
motor and the coiled tubing. The sub assembly 28 is able to provide
torque data experienced by the bottom hole assembly 24 in real
time, and this torque loading is useful as an indicator of imminent
stalling. The information enables early corrective action to
prevent stalling and thereby increase the overall rate of
penetration and improve component life. In this embodiment, sensors
36 can be used to provide additional information. For example,
sensors 36 may comprise a gyro to indicate orientation, a gamma ray
sensor to indicate depth correlation, an inclinometer to track
orientation, and an accelerometer to detect shock and/or
inclination. The accelerometer can be provided as a separate sensor
or as part of the load detection sub assembly 28.
[0026] In another application, well tool 24 comprises a bottom hole
assembly, and load detection sub assembly 28 is used to measure
loads associated with setting inflatable or mechanical packers. In
deviated wells, for example, the set down weight required to
actuate a packer is difficult to determine with surface
measurements alone. The sub assembly 28 can be used to monitor and
output data on the set down force actually being applied downhole.
Tensile loads also can be measured and output to provide an
indication as to how much force can be applied during removal of
the bottom hole assembly. By providing this data in real time,
disconnect forces can be avoided. Similarly, by monitoring the
downhole loads, it is possible to prevent an overload situation
that might damage the tool.
[0027] Similarly the load detection sub assembly 28 can be used to
monitor and output load data when shifting sliding sleeves
downhole. The sub assembly 28 provides information on set down
weight or overpull applied to the sliding sleeve. Additionally, if
the shifting tool does not disengage from the sleeve, precise load
information can be provided in real time regarding the force
applied to break the shear screws as necessary for disengagement.
In a fishing operation, the sub assembly 28 can provide similar
load data related to forces applied to dislodge the "fish". Force
load data can make the fishing operation faster, safer and more
efficient.
[0028] In other applications, well tool 24 comprises a vibration
tool that generates vibration downhole to reduce friction forces
associated with moving the coiled tubing farther downhole. The
performance of the vibration tool 24 can be monitored by sub
assembly 28 and sensors 36 in real time to enable optimization of
the operational parameters and thus enhance execution of the
operation.
[0029] The well tool 24 also may comprise a tractor, and load
detection sub assembly 28 can be used to measure loads incurred
during tractoring operations. For example, it can be important to
know whether the tractor is on or off and to also know the amount
of force applied by the tractor while pulling the string. The sub
assembly 28 is able to provide loading information in real time so
that an operator has a more accurate understanding of the downhole
operation of the tractor. The real time observation of loads also
can prevent tool string failure and damage. Load data also can be
used in combination with a variety of surface measurements and
systems that enable optimal synchronization of tractor operation
with coiled tubing unit surface controls to avoid overloads and to
minimize failures.
[0030] In other applications, well tool 24 comprises a drilling
tool, and sub assembly 28 can be used to provide load data similar
to that described above with respect to the milling operation. For
example, real time tracking of weight on the bit and torque applied
to the drilling tool can be used to prevent stalls and to maximize
rate of penetration.
[0031] The load detection sub assembly 28 also can be used in a
variety of other operations. For example, the sub assembly can be
used during perforating jobs to monitor loads induced as result of
the perforating operation. In this application, the sub assembly 28
can be used to provide data indicative of how and whether the
perforating guns have been activated. An integrated accelerometer
also could be used to monitor shock, and a variety of other sensors
can be used to provide data on various aspects of the perforating
operation. The sub assembly 28 also can detect drag on the bottom
hole assembly 24 and the coiled tubing string that results from
excessive overloads of fill being lifted. Similarly, sub assembly
28 can be used to identify lock up situations, such as those that
result from an obstruction rather than an inability to transmit
loads to the bottom hole assembly.
[0032] Accordingly, the load detection sub assembly 28 provides a
better understanding, in real time, of how the well tool 24 is
being affected downhole by loading that results from a variety of
forces, torques, vibrations and movements. This is particularly
important in adverse scenarios when transmission of downhole loads
is affected by well geometry, completions, fluids, and other
downhole characteristics. The various measurements enable better
operational analysis and improve the ability to take appropriate
corrective action.
[0033] The sensors 36 and load detection sub assembly 28 also can
be used in conjunction with a variety of other surface measurement
and control systems. For example, systems are available that
provide indications of coiled tubing weight or that prevent
unplanned overloading situations. These additional systems can be
operated by surface control unit 30 or in conjunction with surface
control unit 30. In many applications, surface control unit 30 can
be programmed to automatically take certain corrective actions
based on preset parameters when specific data is provided by load
detection sub assembly 28, sensors 36, and/or other cooperating
measurement and control systems.
[0034] Depending on the type of well tool 24 and the type of
operation in which well tool 24 is utilized, the shape, size and
configuration of load detection sub assembly 28 can vary. However,
one example of load detection sub assembly 28 is illustrated in
FIG. 2. In this embodiment, sub assembly 28 comprises an upper
housing 42, a load cell 44, and a load cell housing 46. Upper
housing 42 comprises a connector end 48 opposite load cell 44 to
enable connection of sub assembly 28 to connector assembly 34 via,
for example, threaded engagement or another suitable engagement
mechanism. At an opposite end, sub assembly 28 comprises a
connector 50 that may be any of a variety of connectors depending
on the well tool 24 to which it is connected for a specific well
related operation.
[0035] Referring generally to FIGS. 3 and 4, cross-sectional views
are provided of the sub assembly embodiment illustrated in FIG. 2.
As illustrated, sub assembly 28 comprises a tubular member 52
extending from load cell 44 and partially defining a flow passage
54 formed through sub assembly 28 to accommodate fluid flow through
sub assembly 28. Additionally, sub assembly 28 comprises
electronics 56 that may be mounted on a circuit board 58 for
processing signals received from load cell 44. Circuit board 58 may
be mounted between tubular member 52 and upper housing 42, as
illustrated. Signals are transmitted from electronics assembly 56
to a communication line connector 60 which is designed for
engagement with a corresponding connector in connector assembly 34,
thus enabling transmission of signals to the surface.
[0036] Sub assembly 28 comprises a chassis 64 that is disposed
within upper housing 42 in a manner that does not obstruct flow
passage 54. Tubular member 52 may be formed as an integral part of
chassis 64. Also, chassis 64 is rigidly connected to or integrated
with load cell 44, as illustrated in FIG. 3. A pressure balancing
seal structure 68 is installed at the lower or downhole end of load
cell housing 46 and a seal is formed between seal structure 68 and
the load cell housing 46 via a seal element 69. Seal structure 68
extends up into an interior of chassis 64 and forms a seal with
chassis 64 via a seal element 70, as illustrated. In the embodiment
illustrated, seal structure 68 is formed as a pressure compensating
piston.
[0037] Sub assembly connections, such as the connection of the
upper housing 42 with load cell 44 can be formed with split
connectors 71 which allow the connection of components without
requiring relative rotation of the electrical connections. With
respect to electrical connections, wiring may be routed from
connector assembly 34 and connector end 48 down along the outside
diameter of chassis 64. By way of example, the wiring may be
terminated on the uphole side of circuit board 58. From the
downhole end of circuit board 58, the wiring is further routed
along or through chassis 64 and integrated load cell 44. The wiring
is brought to the outside diameter of the load cell 44 via one or
more ports 72, illustrated best in FIG. 4. Routing the wiring to
the radially outward side of load cell 44/chassis 64 allows the
wiring to be appropriately connected to the load cell. For example,
the wiring may be connected to load measurement sensors, e.g.
strain gauges or other load measurement sensors, of the load cell
44.
[0038] The wiring route and the arrangement of components in load
detection sub assembly 28 enable the detection and monitoring of
loads without having the load measurements skewed by extraneous
elements. For example, the load measurements are isolated from the
effects of radial and hoop forces caused by the pressure of fluid
pumped along flow passage 54 and from similar effects due to
pressure that is external to the tool. The load measurements also
are isolated from axial forces induced by hydrostatic pressure in
the wellbore. Accordingly, more accurate measurements of load
forces, e.g. compressive and tensile load forces, are made
possible, as illustrated in FIGS. 5 and 6.
[0039] Referring to FIG. 5, a compressive load path 74 is
illustrated. The compressive load path 74 results from placement of
sub assembly 28 under compressive loading and illustrates the
components of sub assembly 28 that carry the load forces to load
cell 44. From the downhole end of the sub assembly 28, the loading
force is exerted through load cell housing 46 and transferred to
chassis 64 and the load cell 44 via a threaded region 76. The
compressive load force travels through load cell 44 and chassis
64.
[0040] In FIG. 6, a tensile load path 80 is illustrated. The
tensile load path 80 results from placement of sub assembly 28
under tensile loading and illustrates the components of sub
assembly 28 that carry the tensile load forces to load cell 44.
From the downhole end of the sub assembly 28, the tensile loading
force is carried through load cell housing 46 and transferred to
chassis 64 and load cell 44 via threaded region 76. The tensile
load force travels up through load cell 44 and is transferred to
the shouldered split ring connector 71. Split ring connector 71
transfers the tensile loading to upper housing 42 and upward
through the tool string.
[0041] Under torque loading, the torque loads can be transferred
between upper housing 42 and load cell 44 via one or more torque
keys 82, as illustrated in FIG. 7. The torque keys 82 are engaged
between load cell 44 and upper housing 42 such that any twisting
loads acting on conveyance 26 are transmitted to load cell 44 via
upper housing 42 and torque keys 82.
[0042] The arrangement of components in system 20 and load
detection sub assembly 28 facilitates the provision of accurate and
immediate information that can be used to avoid failures and to
optimize the downhole operation. For example, real time data can be
communicated to surface control unit 30 via, for example, fiber
optic telemetry. The fiber optic telemetry and arrangement of sub
assembly 28 enable transmission of data while the downhole
operation is underway, including while fluids are pumped through
flow passage 54. The design not only enables mechanical pressure
compensation and radial temperature compensation but also
eliminates the effect of "make-up force" on the strain gauge area
of the load cell 44.
[0043] By way of further explanation, the sub assembly 28 is
designed to compensate both for the radial and hoop forces that are
caused by the pressure of fluid as it is pumped along flow passage
54, as well as for similar effects caused by pressure external to
the tool. Additionally, the sub assembly 28 is designed to
compensate for axial forces induced by hydrostatic pressure in
wellbore 22. Compensation for these extraneous pressure/forces is
achieved in part by the design of load cell 44 which has a load
sensor mounting area 84 for receiving one or more load measurement
sensors 86, e.g. strain gauges, optical load sensors, or other load
sensors, as illustrated in FIG. 8.
[0044] The portion of the outside diameter of load cell 44 where
the load measurement sensor 86 is mounted is surrounded by a sealed
atmospheric chamber 88. Chamber 88 is sealed by a seal element 90
cooperating with seal elements 69 and 70. Additionally, the chassis
64 which forms tubular member 52 and flow passage 54 is sealed
downhole relative to the load sensor mounting area 84 by pressure
balancing piston/seal structure 68. Extra radial clearance can be
added between the outside diameter of chassis 64 and the inside
diameter of the load sensor mounting area 84 of load cell 44 to
ensure contact does not occur due to pressure induced or thermally
induced expansion of chassis 64. Thus, the inside diameter of load
cell 44 is only affected by atmospheric pressure.
[0045] Furthermore, the sealed area against which hydrostatic
pressure can act extends from the outside diameter of pressure
balancing seal structure 68, in the region where it seals against
the inside diameter of load cell housing 46 via seal element 69, to
the outside diameter of seal structure 68, where it seals against
the inside diameter of load cell 44/chassis 64 via seal element 70,
as illustrated in FIG. 8. In the axial direction, seal structure 68
enables the compression caused by the hydrostatic pressure to
bypass load sensor mounting area 84. This effect is due to the
outermost sealing diameter being the same on either side of the
atmospheric chamber 88. As a result, force is transferred to seal
structure 68 which acts as a compensating piston. With respect to
radial temperature differences, the atmospheric conditions
surrounding load sensor mounting area 84 along both the outside and
inside of load cell 44 negate any radial temperature differences in
the section of load cell 44 containing strain gauges 86.
[0046] With certain types of bottom hole assemblies, such as bottom
hole assemblies that shoulder internally, the sub assembly chassis
can be subjected to substantial compressive make-up forces during
interactions downhole. However, when sub assembly 28 is "made-up"
at its upper end, chassis 64 shoulders internally which causes
compressive forces in the load cell 44 from the split connector
ring 71 along its length in the uphole direction and in the chassis
64 from its connection with the load cell 44 along its length in
the uphole direction. The load sensor mounting area 84 is not
subjected to these make-up forces. Additionally, when the downhole
end of sub assembly 28 is "made-up", compression is only
experienced by load cell 44 from the threaded region 76 of load
cell housing 46 to the location where the load cell housing 46
shoulders against the load cell, as illustrated in FIG. 8.
Accordingly, the load sensor mounting area 84 is not affected by
the make-up forces.
[0047] In FIG. 9, an alternate embodiment of sub assembly 28 is
illustrated. In this embodiment, the load detection sub assembly 28
comprises a passage 92 for receiving a downhole tool bus 94, e.g.
wires or cable, to provide communication and/or power to a desired
device located below the sub assembly 28. Many of the components in
this embodiment are the same as those described above with
reference to FIGS. 1-8, however passage 92 extends from an upper
connector block 96 to a lower connector block 98. The tool bus,
e.g. wires, is connected between circuit board 58 and connector
block 96. From connector block 96, the wires are passed through the
passage 92 that extends through load cell 44 until reaching lower
connector block 98. To avoid rotating connections, a split ring
connector 100 can be mounted proximate a lower end of the sub
assembly 28.
[0048] Tension and torsion are transmitted via a plurality of
loading keys 102, as illustrated in FIG. 10. The loading keys 102
are installed in corresponding slots 104 formed in a portion of
load cell 44. When the alternate sub assembly 28 is exposed to
compressive loads, the loads are transferred directly from load
cell 44 to chassis 64, as described above. However, under tensile
loading, the loads are transferred to upper housing 42 via loading
keys 102, and chassis 64 is bypassed. The loading keys are designed
to fit snugly into slots 104 and corresponding slots of upper
housing 42. As a result, torsion loads also are transferred from
the load cell 44 to upper housing 42 while bypassing chassis 64. In
this alternate embodiment, chassis 64 seals internally against load
cell 44 downhole of the load sensors/strain gauges. This
arrangement provides the same radial pressure and temperature
compensation as described with respect to the previous embodiment.
The effects of make-up forces on the load sensor mounting area 84
also are avoided in the same way as described with respect to the
previous embodiment.
[0049] As described above, system 20 can be constructed in a
variety of configurations for use in many environments and
applications. The load detection sub assembly can be constructed to
isolate a load sensor from extraneous loading internal to the sub
assembly, external to the sub assembly, exerted axially, resulting
from regular tool make-up, resulting from temperature and pressure
effects and/or other extraneous loads. Additionally, the size and
arrangement of the load detection sub assembly can be adjusted for
environmental and operational factors. The types of load sensors
and sensors incorporated into the load detection sub assembly, as
well as the additional sensors utilized in conjunction with the sub
assembly, can vary substantially depending on the desired
operations and the desired parameters to be monitored. The
electronics can be substituted with optical systems that rely an
optical sensors. Additionally, the surface control unit 30 may
combine a variety of systems and may be programmed in many
different ways to facilitate monitoring, analysis, and the taking
of corrective actions either automatically or with the assistance
of an operator.
[0050] Accordingly, although only a few embodiments of the present
invention have been described in detail above, those of ordinary
skill in the art will readily appreciate that many modifications
are possible without materially departing from the teachings of
this invention. Such modifications are intended to be included
within the scope of this invention as defined in the claims.
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