Source: https://patents.google.com/patent/US7770667?oq=5%2C579%2C517
Timestamp: 2018-02-22 21:40:48
Document Index: 647140825

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60']

US7770667B2 - Electrically powered tractor - Google Patents
Electrically powered tractor
US7770667B2
US7770667B2 US12139385 US13938508A US7770667B2 US 7770667 B2 US7770667 B2 US 7770667B2 US 12139385 US12139385 US 12139385 US 13938508 A US13938508 A US 13938508A US 7770667 B2 US7770667 B2 US 7770667B2
US12139385
US20080308318A1 (en )
An electrically powered and controlled tractor system includes one or more electric gripper assemblies and one or more electric power train assemblies. Power and control signals for the gripper assemblies and power train assemblies can be delivered from a ground surface via a wireline. The gripper assembly employs a motor-activated lead screw and nut combination to expand passage-gripping elements, preferably by pushing the gripping elements radially outward from locations between opposing ends of the gripping elements. A failsafe mechanism can retract the gripping elements during a power interruption. The power train assembly employs a motor-activated lead screw and nut combination to expand and contract two ore more telescoping members. The tractor system can include multiple tractor units that each includes one gripper assembly and one power train assembly. A tractor can include one power train assembly and two gripper assemblies.
This application claims priority to Provisional Application No. 60/944,078, filed Jun. 14, 2007; Provisional Application No. 60/934,784, filed Jun. 15, 2007; and Provisional Application No. 60/964,788, filed Aug. 14, 2007.
This application incorporates by reference the entire disclosures of the following: U.S. Pat. Nos. 6,003,606 to Moore et al.; U.S. Pat. No. 6,241,031 to Beaufort et al.; U.S. Pat. No. 6,347,674 to Bloom et al.; U.S. Pat. No. 6,679,341 to Bloom et al.; U.S. Pat. No. 7,121,364 to Mock et al.; U.S. Pat. No. 6,464,003 to Bloom et al.; U.S. Patent Application Publication No. US2007-0209806-A1 to Mock; (now issued as U.S. Pat. No. 7,624,808); and U.S. patent application Ser. No. 11/939,375, filed Nov. 13, 2007 (now published as U.S. Patent Application Publication No. US2008-0149339A1). This application also incorporates by reference the entire disclosures of Provisional Application No. 60/944,078, filed Jun. 14, 2007; Provisional Application No. 60/934,784, filed Jun. 15, 2007; and Provisional Application No. 60/964,788, filed Aug. 14, 2007.
It is known to deploy various types of tools for moving and operating equipment in passages, such as wells and open boreholes. In oil and gas wells, such equipment is often referred to as a “bottom hole assembly” and can perform various functions, which may or may not require fluid for operation. Functions that typically require fluids include drilling, acidizing, and sand washing, and functions that typically do not require fluids include logging of open and cased boreholes, conducting pressure and temperature surveys, and caliper logs.
As used herein, the terms “hole,” “passage,” “well,” and “borehole” are used interchangeably. The inner perimeter of a hole is referred to herein as a “surface,” “inner surface,” or “wall” of the hole. A cased hole is one that has a casing or metal liner (such as so-called sand screen) formed at its inner surface. An open hole is one that does not have such a casing. As used herein, the term “downhole” refers to the direction pointing away from a ground surface at which a tractor is deployed, and the term “uphole” refers to the direction pointing toward the ground surface.
A tractor is one type of tool that can move and help to operate equipment in passages. A tractor may include an elongated body, one or more gripper assemblies (also sometimes referred to as “grippers”) along the body, and one or more propulsion assemblies. Each gripper assembly may have a radially expanded position in which the gripper assembly limits relative movement between the gripper assembly and an inner surface of a passage, well, or borehole. Each gripper assembly can also have a radially retracted position in which the gripper assembly permits substantially free relative movement between the gripper assembly and the inner surface of the passage. Each propulsion assembly can produce longitudinal displacement of the body with respect to one of the gripper assemblies when radially expanded.
In certain implementations, tractors are adapted to walk through a borehole or well. Typically, a first gripper assembly is expanded to grip the hole, and a propulsion assembly propels the tractor body longitudinally with respect to the expanded first gripper assembly. This is referred to as a “power stroke” with respect to the first gripper assembly. Simultaneously, a retracted second gripper assembly is moved longitudinally with respect to the body for a subsequent power stroke. This is referred to as a “reset stroke” with respect to the second gripper assembly. After these power and reset strokes complete, the second gripper assembly is expanded and the first gripper assembly retracts. Then, a propulsion assembly propels the tractor body longitudinally with respect to the expanded second gripper assembly. In other words, the tractor conducts a power stroke with respect to the second gripper assembly. Simultaneously, the retracted first gripper assembly is moved longitudinally with respect to the body for a subsequent power stroke. In other words, the tractor conducts a reset stroke with respect to the first gripper assembly. Tractors that employ this walking method include those described in U.S. Pat. Nos. 6,003,606 to Moore et al.; U.S. Pat. No. 6,241,031 to Beaufort et al.; U.S. Pat. No. 6,347,674 to Bloom et al.; U.S. Pat. No. 6,679,341 to Bloom et al.; U.S. Pat. No. 7,121,364 to Mock et al.
Other known tools are powered entirely electrically. Such tools are employed within wells, as opposed to open (i.e., uncased) boreholes. Such tools can employ wheels or moving traction belts for gripping and moving with respect to the inner surface of a cased well. Such tools often employ downhole electric motors that perform operations related to moving the tool downhole. Electrical power and signals for propelling and controlling the tool is normally provided through a wireline that extends from the ground surface to the tool, through the well. Electrically powered tools (or “wireline tools”) are preferred when payloads are relatively light (e.g., less than 2000 lbs) and the hole to be serviced is not extremely long. Examples of lighter payloads include logging tools and certain pipeline applications.
In one aspect, the present application provides a tractor for moving within a passage. The tractor comprises first and second body portions positioned along a longitudinal axis of the tractor, a gripper assembly, and a power train assembly. The gripper assembly comprises a gripper motor, first and second gripper interface portions, and at least two elongated gripping elements engaged with respect to one of the body portions. The gripper motor has an output shaft adapted to rotate about a gripper motor axis during activation of the gripper motor. The first gripper interface portion is oriented substantially along the gripper motor axis, and the second gripper interface portion is in engagement with the first gripper interface portion. One of the first and second gripper interface portions comprises a gripper rotating element configured to rotate about the gripper motor axis during rotation of the output shaft relative to the gripper motor. The other of the first and second gripper interface portions comprises a gripper extension element being configured to move longitudinally with respect to the gripper motor during rotation of the output shaft relative to the gripper motor, due to said engagement between the interface portions. The gripping elements have a movement-limiting mode in which the gripping elements limit relative movement between the gripping elements and an inner surface of a passage, and a movement-permissive mode in which the gripping elements permit substantially free relative longitudinal movement between the gripping elements and the inner surface. The gripper extension element comprises part of a gripper expansion assembly for converting longitudinal motion of the gripper extension element into movement of the gripping elements between said movement-limiting mode and said movement-permissive mode of the gripping elements. The gripper assembly is configured to limit longitudinal movement of one of the body portions relative to the passage when the gripping elements are in said movement-limited mode. The power train assembly comprises a power train motor and a power train subassembly for converting activation of the power train motor into relative longitudinal movement between the first and second body portions.
FIG. 1 is a perspective, sectional view of an embodiment of a wireline tractor.
Limitations of Prior Wireline Tools
FIG. 1 shows an electrically powered tractor or tool 10 in accordance with certain embodiments. The tractor 10 comprises an electrically powered and/or controlled gripper assembly 20, and an electrically powered and/or controlled power train assembly 30. When actuated, the gripper assembly 20 expands to grip onto the inner surface of a passage within which the tractor 10 is positioned. The gripping of the passage wall provides a point of contact against which the power train assembly 30 propels the tool 10. The power train assembly 30 produces longitudinal movement of the tractor 10 in a desired direction within the passage. As used herein, an “electric gripper assembly” refers to a gripper assembly that is electrically powered, and possibly electronically controlled. As used herein, an “electric power train assembly” refers to a power train assembly that is electrically powered, and possibly electronically controlled.
The physical size of the tractor 10 is preferably scalable and may vary depending upon the application. For example, the tractor 10, when used for open hole logging, may have a collapsed diameter (as used herein, “collapsed diameter” refers to the diameter when the gripper assembly 20 is radially retracted) that ranges from 2-6 inches, with approximately 5 inches being preferred for open hole logging within holes of approximately 6-9 inches diameter. The length of the tractor 10 can also be selected based upon its intended usage. For example, if it is necessary to deploy the tractor 10 into a well with a gin pole, then the length of the tractor 10 (or a held segment thereof) is preferably less than about 20 feet, and preferably about 12-15 feet.
FIG. 2 shows an embodiment of the gripper assembly 20 of a tractor unit 10 (FIG. 1). The illustrated gripper assembly 20 includes a gripper motor housing 202, a first toe anchor 204, a plurality of passage gripping elements or toes 206, and a second toe anchor 208. The gripper motor housing 202 houses a wireline connector 210, motor controller 212, and electric gripper motor 214. Also shown in FIG. 2 are a drive screw (or more generally an interface portion) 216 and a toe nut (or more generally an interface portion) 218 in engagement (e.g., threaded engagement) with one another. As used herein, the terms “lead screw” and “drive screw” are used interchangeably, and both may encompass different types of screws, including a ball screw. FIG. 2 also shows a conduit 221 that may contain electrical wires for conveying electrical power and electronic signals through the gripper assembly 20.
The housing of the motor 214 is preferably fixed with respect to the gripper motor housing 202. Generally, one of the drive screw 216 and the toe nut 218 can comprise a “rotating element” configured to rotate about the longitudinal axis of the tractor during activation of the gripper motor 214, and the other of the drive screw 216 and the toe nut 218 can comprise an “extension element” configured to move longitudinally with respect to the gripper motor 214 during rotation of the motor's output shaft relative to a housing of the motor, due to the threaded engagement between the drive screw and the toe nut. It should be understood that, in embodiments, the extension element does not necessarily move with respect to the motor 214 during motor activation (i.e., while the motor is powered on, but not necessarily rotating its output shaft, or while the motor's output shaft is rotating). For example, as described elsewhere herein, a clutch can decouple the gripper motor 214 from the rotating element. The rotating element can be coupled directly or indirectly with respect to an output shaft of the gripper motor 214. In the illustrated embodiment, the drive screw 216 is the rotating element, because it is coupled with respect to an output shaft of the gripper motor 214. The illustrated toe nut 218 is the extension element because it is prevented from rotating, such as by having a notch that engages an elongated spline 226. In an alternative embodiment, the toe nut 218 has an alignment pin that engages a longitudinal slot to prevent the nut 218 from rotating. It will be appreciated that alternative guidance features can alternatively be provided. Thus, the toe nut 218 moves longitudinally as the drive screw 216 rotates. In an alternative embodiment, the toe nut 218 is the rotating element, being coupled with respect to the output shaft of the gripper motor 214, and the drive screw 216 is the extension element.
The gripper assembly 20 is preferably longitudinally fixed with respect to a body portion of the tractor 10, the body portion being positioned along the longitudinal axis of the tractor. As used herein, a body portion “positioned along” the tractor's longitudinal axis may or may not intersect said axis. In the illustrated embodiment, the gripper assembly 20 is longitudinally fixed with respect to an outer torque slider housing 302. The gripper assembly 20 has a movement-limiting mode (e.g., a radially expanded position) in which it limits relative movement between the gripper assembly 20 and an inner surface of a passage within which the tractor is positioned. The gripper assembly 20 also has a movement-permissive mode (e.g., a radially retracted position) in which it permits substantially free relative movement between the gripper assembly 20 and the inner surface of the passage.
One advantage of a passage gripping element 206 comprising a single flexible beam 232 as in FIG. 2 a is that it is inherently failsafe, meaning that it has a proclivity to straighten itself when power to the gripper assembly 20 is terminated or interrupted. As used herein, the term “failsafe” refers to the quality of automatically retracting from the borehole surface during a power loss, which helps to prevent the tractor from getting stuck and being difficult to remove from the borehole. When the expansion force is terminated, the flexible beams 232 tend to straighten and move away from the borehole wall, which thereby collapses the gripper assembly when electrical power is interrupted. When retracting, the beams 232 can urge the drive screw 216 to rotate in reverse (i.e., the direction of rotation opposite that which cases the gripper assembly 20 to expand), if the friction associated with drive screw rotation is low enough. Examples of gripper assemblies employing flexible beams are disclosed in U.S. Pat. No. 6,464,003 to Bloom et al.
Alternatively, the gripper motor 214 can be an AC motor. AC motors require less downhole electronics, which are susceptible to being affected by heat. Moreover, in some configurations, all downhole electronics may be eliminated with a special connector that acts as both rotary joint and motor select. Certain types of AC motors are more reliable than some DC motors. Also, AC motors are compatible with inexpensive, surface-deployable, motor control electronics that are readily available “off-the-shelf.” AC motors provide good torque, low vibration, and speed control, as well as only stator winding. Downsides of AC motors include the need for more conductors, and the fact that the oil industry has a history of problems with AC motors.
Several suppliers of motors may supply off-the-shelf or specially made motors and controllers. Motor Appliance Corporation supplies AC induction motors that operate at temperatures up to 350° F. SI Montevideo Technology has built DC brushless servo and induction motors that operate at elevated temperatures. Esterline Corporation and Artus Corporation provide motors for borehole applications. These and other suppliers may provide motors and controllers for the electrically powered tractors 10 disclosed herein. In one embodiment, the gripper motor 214 delivers about 2.2 horsepower.
It will be understood that the amount of electrical power available at the tractor 10 greatly affects the tractor's performance. It will also be understood that the amount of power depends upon the depth of the tractor 10, as well as the local temperature at that depth. Some down hole environments may have temperatures up to 300° F. Also, the motors of a tractor 10 can dissipate considerable heat during operation. For these reasons, special considerations may be made to control heat within the tractor 10.
The electronics of the tractor 10 can be designed to allow operation at temperatures up to 300° F. It is well known that elevated temperatures act to reduce operational life of electronics. The electronics can be tested and burned in for a selected time to eliminate initial burnout of electrical components. In addition, the electrical parts are preferably selected or manufactured to specifications to survive prolonged heat exposure.
A variety of materials may be used for the electrical components of the tractor 10. Various high grade winding insulations (such as irridated polyvinyl chloride) may be used, which are qualified for various downhole temperature ranges. For example, insulations that are capable of operation at 300-500° F. can be used.
The tractor units 10 desirably may be connected to various types of wireline 40 with a multiplicity of commercially available or specialized electrical connectors. These connectors may be hermetically sealed to preventingress of the various downhole fluids. Kemlon Corporation provides various types of connectors used for downhole applications, including “wet stab” connectors that allow for assembly in moist environments. A wet stab is a connection that can be assembled while wet. Field operations are typically conducted in fluid-rich environments, wherein fluids surround the electrical connections. Wet stab connections allow for electrical connections to be established in damp or even wet environments without shorting the electrical connections. Preferably, wet stab connectors are used at the connection of the wireline 40 to the wireline connector 210, as well as other electrical connections downhole (such as connections between tractor units).
For both pipelines and borehole, the turning radius that can be achieved is typically limited by the “stick length” of the tractor 10 or the flexibility of the tractor. “Stick length” is the length of a tool or segment of a tool that remains rigid under normal operations, and flexes only slightly. The “flexibility” is the product of the effective polar moment of inertia and the modulus of elasticity of the tool. When the tool or tool segment is rigid, the stick length is the maximum tool length or segment that can pass through a curved borehole without binding against the borehole wall. When a tool has moderate flexibility, a tool or tool segment can slide through a borehole of a particular radius of curvature without permanent deformation or yielding.
In the illustrated embodiment of the two-unit tractor system 400, the aft power train assembly 440 is physically and electrically connected to the forward gripper assembly 450. This is referred to herein as a “head-to-tail” arrangement, in which the tractor units 410 and 420 are connected in a repeating pattern. In embodiments of head-to-tail arrangements, a plurality of connected tractor units (including more than two units) has a repeating pattern of relative positions of the gripper assemblies and power train assemblies.
In another embodiment, the aft power train assembly 440 is physically and electrically connected to the forward power train unit 460, with the forward gripper assembly 450 being positioned forward of the forward power train unit 460. This is referred to herein as a “head-to-head” arrangement. In embodiments having more than two tractor units, a head-to-head arrangement may require that a gripper assembly connects to another gripper assembly, and that a power train assembly connects to another power train assembly. Thus, some of the gripper assemblies will have male connectors, and others will have female connectors. Likewise, some of the power train assemblies will have male connectors, and others will have female connectors. A head-to-head arrangement can have the disadvantage of doubling a required inventory of tractor units. It will be appreciated that a multi-unit tractor system can include pairs of tractor units that are connected head-to-head (or its complement, tail-to-tail), as well as pairs of tractor units that are connected head-to-tail.
Tool outside diameter (OD) when gripper 5 inches
Tool OD when gripper assemblies are 9.5 inches
Length <20 feet
Maximum well pressure 8000 psi
Maximum temperature 300° F.
Speed range without load 750-1000 feet/hour
Maximum pulling force 2400 lbs
Maximum turning capability (dog-leg) 30 degrees per 100 feet of
Tensile strength 30,000 lbs
Wireline configuration 7-conductor Hepta
Magnetic signature None
Estimated weight 350 lbs
Maximum operational distance from 25,000 feet
Many of the components of the surface equipment 910 and downhole equipment 920 can be purchased and integrated into the tractor system. For example, Scotland Electric International (LTD) of Scotland, UK commercially provides personal computer interface controls and monitors (i.e., computer, software, data acquisition), high voltage surface power supply units (element 916), communications and power interface modules (element 914), downhole electronic line conditioning units, downhole electronics over/under voltage protection units, downhole electronics for communications on power interface units (element 928), downhole electronics for DC/DC power supply units (DC transformer to step down the electrical voltage, element 926), downhole electronics for tool sensor power and conditioning, downhole electronics for tool sensors isolated data interfaces, and downhole electronics for data monitoring and control processors. Alternatively, Scientific Data Systems of Houston, Tex. provides surface control and communications units as well as a proprietary software packages (“Warrior”) that can be adapted for use in the tractor 700. Other providers supply downhole power supplies and tractor-surface communications hardware. The tractor can use different types of communication links from the ground surface to the tractor. In one embodiment, the tractor system uses an RS232 link in a DC power supply.
When operated at temperatures above 225° F., many motor controllers and electronic components are unable to achieve a long life. Thus, the motor controllers and other components of the tractor 700 (and preferably the other tractors described herein) are preferably selected or tested to verify reliable operation at a higher temperature, such as 300° F. In addition, heat dissipation features and pressure-compensation can be incorporated to increase motor life, as discussed above. Accordingly, the downhole electronics can be housed in an atmospheric chamber to prevent damage to the electronics caused by downhole pressures.
Tractor system range
description (ft/hr)* Advantages Disadvantages
Two gripper 850-1150 Only three motors. Power train motor
assemblies and Complies with operating
one power existing safety constantly,
train assembly requirements of involving potential
surface voltages. for short life.
Shorter, lighter, and Tractor failure
less expensive. occurs when power
train motor fails.
Two gripper 1000-1350 Faster operation than Tool is longer,
assemblies and single drive. Can heavier, more
two power drive two power train complex, and more
train assemblies at shallow expensive than
assemblies, depth and single tractor with one
with only one power train assembly power train
power train at the bottom of the assembly.
assembly motor hole. Power train
operating at redundancy allows
a time tractor operation if
one power train
assembly fails
Two gripper 2000-2300 Runs faster than other Tool is longer,
assemblies and configurations at heavier, more
two power light loads. Can complex, and more
train convert to single expensive than
assemblies, power train operation tractor with one
with if electrical power is power train
simultaneous limited. Power train assembly.
operation of redundancy allows
the power tractor operation if
train motors one power train fails
(*with load of 2300 lbs and 25,000 feet wireline; 900 V power at surface)
Another feature or advantage of embodiments of the tractor systems of this application involves a high turning radius. Embodiments may have “ball and socket” connections that allow the tool to have a high turning radius, thus allowing operations in highly curved and deviated boreholes and certain pipeline applications.
FIG. 13 shows an embodiment having a gripper expansion assembly comprising an expandable assembly that includes segments 1310 and 1320 pivotally connected in series. The expandable assembly is coupled with respect to the extension element (not shown) such that the expandable assembly is selectively moveable between a first position and a second position. In the first position, the segments 1310 and 1320 are substantially aligned and substantially parallel to the longitudinal axis of the tractor. In the second position, the segments 1310 and 1320 are buckled radially outward with respect to the longitudinal axis of the tractor. In this embodiment, the passage-gripping elements comprise flexible beams 232. A roller 1330 is coupled to each flexible beam 232 at an inner surface of the beam. Each roller 1330 is configured to roll upon an inclined portion of one of the segments 1320 to initiate radial expansion of the beam 232. When buckled radially outward, the segments 1310 and 1320 move the beams 232 to their expanded positions. In this context the term “buckled” means that the joint at which the linked segments 1310 and 1320 are connected moves radially outward. “Buckled” is not meant to imply mechanical failure in this context. Further details concerning the gripper expansion assembly of FIG. 13 are shown and described in U.S. Pat. No. 7,624,808 to Mock.
50. The tractor system of claim 44, wherein the gripping elements in said movement-limiting mode have a radially expanded position relative to the tractor's longitudinal axis, and wherein the gripping elements in said movement-permissive mode are radially retracted from their expanded position.
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US96478807 true 2007-08-14 2007-08-14
US12139385 US7770667B2 (en) 2007-06-14 2008-06-13 Electrically powered tractor
US12840166 US8028766B2 (en) 2007-06-14 2010-07-20 Electrically powered tractor
US20080308318A1 true US20080308318A1 (en) 2008-12-18
US7770667B2 true US7770667B2 (en) 2010-08-10
ID=40131268
US12139385 Active 2028-10-03 US7770667B2 (en) 2007-06-14 2008-06-13 Electrically powered tractor
US12840166 Active US8028766B2 (en) 2007-06-14 2010-07-20 Electrically powered tractor
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MOORE, NORMAN BRUCE;REEL/FRAME:021426/0523