Gripper control in a coiled tubing system

A system is provided including a coiled tubing injector including at least two gripper chains for gripping a coiled tubing and a gripper system for generating a gripper force applied to the at least two gripper chains by adjusting gripper pressure on at least one gripper cylinder. A gripper controller is configured to determine a minimum gripper pressure and a maximum gripper pressure for the gripper cylinders, based on a current set of parameters related to lowering the coiled tubing into a wellbore or pulling out the coiled tubing from the wellbore. The gripper controller selects a target gripper pressure between the minimum gripper pressure and the maximum gripper pressure based on a historical data model and sets the target gripper pressure for the at least one gripper cylinder.

TECHNICAL FIELD

The present disclosure relates generally to well drilling and completion operations and, more particularly, to gripper control in coiled tubing systems.

BACKGROUND

Reeled or coiled tubing has been run into wells for many years for performing certain downhole operations, including but not limited to completions, washing, circulating, production, production enhancement, cementing, inspecting and logging. Such tubing is typically inserted into a wellbore by a coiled tubing injector apparatus which generally incorporates a multitude of gripper blocks for handling the tubing as it passes through the injector. The tubing is flexible and can therefore be cyclically coiled onto and off of a spool, or reel, by the injector which often acts in concert with a windlass and a power supply which drives the spool, or reel.

While aspects of this disclosure have been depicted and described and are defined by reference to exemplary aspects of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described aspects of this disclosure are examples only, and not exhaustive of the scope of the disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide improved techniques for automatically determining an optimized gripper pressure to set for gripper cylinders of an injector to apply a corresponding optimized gripping force on a set of gripper chains that engage a coiled tubing during a coiled tubing injector operation.

The disclosed system and methods provide several practical applications and technical advantages. For example, the disclosed system provides the practical application of automatically determining an optimized target gripper pressure to set of gripper cylinders of an injector during a coiled tubing injector operation. As described in accordance with one or more embodiments of the present disclosure, a gripper controller automatically determines an operating pressure window for the gripper cylinders at any stage during the injector operation, and then determines an optimized target gripper pressure to be applied to the gripper cylinders based on a historical data model. To determine the operating pressure window, the gripper controller determines a minimum gripper pressure that is to be applied to the gripper cylinders to avoid pipe slippage and a maximum allowed gripper pressure that can be applied to the gripper cylinders to avoid pipe damage. The gripper pressure set for the gripper cylinders controls the gripping force applied to the gripper chains of the coiled tubing injector. Thus, the operating window for the gripper pressure defines an operating window for the gripping force. The gripper controller selects a target gripper pressure that lies within the determined pressure window and is optimized based on the historical data model. By determining the gripper pressure window, gripper controller avoids the target gripper pressure from being set too low resulting in pipe slippage or set too high to damage the coiled tubing. The historical data model provides the gripper controller benefit of past experiences under similar conditions and a concrete guide to what target gripping pressures can be optimal for the given conditions. For example, as described above, the historical data model provides gripper pressure values and/or corresponding gripping force values that were determined to be optimal for a given set of conditions (e.g., parameter values). Optimizing the target gripper pressure to be set for the gripper cylinders based on the historical data model helps minimize pipe damage. In one or more embodiments, the gripper controller may be configured to continuously monitor one or more parameters relating to the injector operation and adjust the target gripper pressure as needed when an injector operation is in progress. For example, the gripper controller may be configured to determine and adjust the target gripper periodically, randomly or based on a pre-selected schedule. The entire operation including monitoring the parameters related to the operation of the injector, determining the gripper pressure window, selecting an optimized target gripper pressure and adjusting the target gripper pressure for the gripper cylinders is designed to be fully automatic and not needing operator intervention. Thus, the disclosed system and methods significantly reduce operator burden. Further, by determining optimized gripper pressure values in accordance with techniques disclosed herein, the disclosed system and methods avoid the gripper pressure from being set too low resulting in pipe slippage or too high resulting in pipe damage. Further, the adjustment of the gripper pressure throughout the operation of the injector may ensure minimal damage to the coiled tubing.

The disclosed system and methods provide an additional practical application of using a hoisting load of the injector and an internal pressure of the coiled tubing to determine the maximum gripping force to be applied to the gripper chains. Both the hoisting load and internal pressure of the coiled tubing at any time during an injector operation can affect the maximum gripper pressure or resulting gripping force that can be applied to the injector. Thus, considering the hoisting load and the internal pressure of the coiled tubing when determining the maximum gripping force may yield a more accurate value of the maximum gripping force which may help avoid damage to the coiled tubing.

For the purposes of this disclosure, computer-readable media may include any instrumentality or aggregation of instrumentalities that may retain data and/or instructions for a period of time. Computer-readable media may include, for example, without limitation, storage media such as a direct access storage device (for example, a hard disk drive or floppy disk drive), a sequential access storage device (for example, a tape disk drive), compact disk, CD-ROM, DVD, RAM, ROM, electrically erasable programmable read-only memory (EEPROM), and/or flash memory; as well as communications media such wires, optical fibers, microwaves, radio waves, and other electromagnetic and/or optical carriers; and/or any combination of the foregoing.

To facilitate a better understanding of the present disclosure, the following examples of certain aspects are given. In no way should the following examples be read to limit, or define, the scope of the invention. Aspects of the present disclosure may be applicable to horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean formation. Aspects may be applicable to injection wells as well as production wells, including hydrocarbon wells. Aspects may be implemented using a tool that is made suitable for testing, retrieval and sampling along sections of the formation. Aspects may be implemented with tools that, for example, may be conveyed through a flow passage in tubular string or using a wireline, slickline, coiled tubing, downhole robot or the like. “Measurement-while-drilling” (“MWD”) is the term generally used for measuring conditions downhole concerning the movement and location of the drilling assembly while the drilling continues. “Logging-while-drilling” (“LWD”) is the term generally used for similar techniques that concentrate more on formation parameter measurement. Devices and methods in accordance with certain aspects may be used in one or more of wireline (including wireline, slickline, and coiled tubing), downhole robot, MWD, and LWD operations.

A coiled tubing injector (also referred to as injector head) utilizes a pair of opposed endless drive chains which are arranged in a common plane. These opposed endless drive chains are often referred to as gripper chains because each chain has a multitude of gripper blocks attached therealong. The gripper chains are driven by respective drive sprockets which are in turn powered by a reversible hydraulic motor. Each gripper chain is also provided with a respective idler sprocket to maintain each gripper chain within the common plane. Both the drive sprockets and idler sprockets are mounted on a common frame wherein the distance between centers of all the sprockets are essentially of a constant distance from each other. That is, the drive sprockets are free to rotate, but are not free to move either vertically or laterally with respect to each other. The idler sprockets are not free to move laterally with respect to each other but are vertically adjustable within a limited range in order to set the amount of play in each gripper chain. Such vertical adjustment is made by either a mechanical adjusting means or a hydraulic adjusting means. Typically, for injectors having mechanical adjustment means, the adjustment is made when the injector is not in operation.

The opposed gripper chains, preferably via the gripper blocks, sequentially grasp the tubing that is positioned between the opposed gripper chains. When the gripper chains are in motion, each gripper chain has a gripper block that is coming into contact with the tubing as another gripper block on the same gripper chain is breaking contact with the tubing. This continues in an endless fashion as the gripper chains are driven to force the tubing into or out of the wellbore, depending on the direction in which the drive sprockets are rotated. Gripper blocks such as those set forth in U.S. Pat. No. 5,094,340, issued Mar. 10, 1992, to Avakov, which is incorporated herein by reference, may be used.

The gripper chain is provided with a predetermined amount of slack which allows the gripper chain to be biased against the tubing to inject the tubing into and out of the wellbore. This biasing is accomplished with an endless roller chain disposed inside each gripper chain. Each roller chain engages sprockets rotatably mounted on a respective linear bearing beam, referred to herein as a linear beam. A linkage and hydraulic cylinder mechanism allows the linear beams to be moved toward one another so that each roller chain is moved against its corresponding gripper chain such that the tubing facing portion of the gripper chain is moved toward the tubing so that the gripper blocks can engage the tubing and move it through the apparatus. The gripper blocks will engage the tubing along a working length of the linear beam.

Each gripper chain has a gripper block that contacts the tubing at the top of the working length as a gripper block on the same chain is breaking contact at a bottom of the working length of the linear beam.

The fixed distance between each set of drive sprockets and idler sprockets requires some significant lateral movement in the gripper chain when engaged by the roller chain on the corresponding linear beam in order to allow the gripper chains to engage the tubing by way of the gripper blocks. The reason for having the requisite amount of lateral play in the gripper chains is to provide a limited amount of clearance between the gripper chains, upon moving the respective roller chains away from the vertical centerline of the injector, to allow the passage of tubing and tools having larger outside diameters or dimensions.

FIG.1is a schematic of an example coiled tubing injector system100in which aspects of the present disclosure may be practiced.

As shown inFIG.1, coiled tubing injector10(also referred to as injector head) is shown positioned above a wellhead12of a well13at a ground surface or subsea floor14. A lubricator or stuffing box16is connected to the upper end of wellhead12.

Coiled tubing18, having a longitudinal central axis20and an outer diameter or outer surface22, is supplied on a large drum, or reel24and is typically several thousand feet in length. Tubing18of sufficient length may be inserted into the well13either as single tubing, or as tubing spliced by connectors or by welding. The outer diameters of the tubing18typically range from approximately one inch (2.5 cm) to approximately five inches (12.5 cm). The disclosed injector10is readily adaptable to even larger diameters. Tubing18is normally spooled from drum24typically supported on a truck (not shown) for mobile operations.

Injector10is mounted above wellhead12on legs26. A guide framework28having a plurality of pairs of guide rollers30and32rotatably mounted thereon extends upwardly from injector10.

Tubing18is supplied from drum24and is run between rollers30and32. As tubing18is unspooled from drum24, generally it will pass adjacent to a measuring device, such as wheel34. Alternatively, the measuring device may be incorporated in injector10.

Rollers30and32define a pathway for tubing18so that the curvature in the tubing18is slowly straightened as it enters injector10. As will be understood, tubing18is preferably formed of a material which is sufficiently flexible and ductile that it can be curved for storage on drum24and also later straightened. While the material is flexible and ductile, and will accept bending around a radius of curvature, it runs the risk of being pinched or suffer from premature fatigue failure should the curvature be severe. Rollers30and32are spaced such that straightening of the tubing18is accomplished wherein the tubing18is inserted into the well13without kinks or undue bending on the tubing18. However, the disclosed injector10can be used for injecting, suspending, or extracting any generally elongated body.

FIG.2illustrates details of an example injector10in which aspects of the present disclosure can be practiced.

Injector10includes a frame36(shown inFIG.1). Frame36has legs38, rear supports40, and side supports (not shown). Injector10further comprises a base44which makes up a part of frame36, and a pair of substantially similar carriages46(shown inFIG.2) extending upward therefrom. The injector10also includes hydraulic gripper cylinders66for moving the carriages46laterally with respect to one another and with respect to the base44. Carriages46comprise a first or right side carriage72and a second or left side carriage74. Carriages72and74can move towards and away from each other when gripper cylinders66are actuated. Carriages72and74are substantially similar in that, as seen inFIG.2, carriages72and74are mirror images of one another. Right side carriage72comprises first outer plate76and the left side carriage74comprises a second outer plate78(shown as partially cutout). Outer plates76and78are mirror images of one another. First outer plate76may include a rectangular cutout80at or near a lower end82thereof. A pair of bosses84extend along the sides of rectangular cutout80. First outer plate76has a mounting boss88at an upper end90thereof. Second outer plate78, being a mirror image of first outer plate76, likewise includes a rectangular cutout (not shown) at or near a lower end thereof and a pair of bosses (not shown) extending downwardly along sides of rectangular cutout. Second outer plate78also has a mounting boss at an upper end thereof.

Each carriage46also includes a gripper chain drive system106and a roller chain drive system108. Gripper chain drive system106includes a pair of spaced gripper chain drive sprockets110rotatably disposed in the carriage46. Drive sprockets110are mounted on respective drive sprocket shafts112having a centerline, or longitudinal central axis corresponding to, or collinear with, an axis of rotation of the drive sprockets110. Each drive sprocket110is driven by a reversible hydraulic motor (not shown) attached to each carriage46on the back side of the injector10. The hydraulic motor may be any type known in the art and is driven by a planetary gear and has an integral brake. Thus, the hydraulic motor can inject, retract, or suspend tubing18in the well13. Drive sprocket shafts112may be keyed or otherwise connected to drive sprockets110, so that rotation of drive sprocket shaft112will rotate drive sprockets110.

Gripper chain drive system106also includes a pair of spaced gripper chain idler sprockets120which are rotatably disposed in the lower end of each carriage46. Idler sprockets120are mounted on idler sprocket shaft122, having a centerline, or longitudinal central axis corresponding to, or collinear with, an axis of rotation of the idler sprockets120. In the embodiment shown, the idler sprocket shaft122and idler sprockets120are one piece. However, idler sprocket shaft122may be keyed or otherwise connected to idler sprockets120so that idler sprocket shaft122and idler sprockets120will rotate together. The gripper chain drive system106further includes a pair of opposing gripper chains126mounted on respective drive sprockets110and idler sprockets120. Each gripper chain126is engaged with a drive sprocket110and an idler sprockets120in each carriage46. Each gripper chain126may be of a kind known in the art and includes a plurality of outwardly facing gripper blocks128(or grippers) disposed thereon.

Gripper blocks128are adapted for engaging tubing18and moving it through injector10. Gripper blocks128may be like those set forth in U.S. Pat. No. 5,853,118, issued Dec. 29, 1998, to Avakov or U.S. Pat. No. 6,230,955, issued May 15, 2001, to Parks, both of which are incorporated herein by reference and assigned to the assignee of the present invention. When gripper cylinders66are actuated to move carriages72and74together, a gripping force is applied to tubing18by gripper blocks128. Griper blocks128generally have an inner face defining an inner profile. The gripper blocks128contact the outer diameter22of tubing18on both sides of longitudinal central axis20.

Tensioners (not shown) may be provided for adjustment of the position of the idler sprocket shafts122so that proper tension on gripper chains126may be maintained, and so that the proper distance, and parallel relationship between idler sprocket shafts122and drive sprocket shafts112may be maintained. Drive sprocket shafts112are generally fixed in position relative to the outer plates76and78. Idler sprocket shafts122are vertically adjustable so that proper chain tension can be achieved.

The roller chain drive system108is rigidly positioned in each carriage46between outer plates76and78. Roller chain drive system108includes a linear or pressure beam150rigidly fixed to the outer plates76and78of each carriage46. Linear beam150may be rigidly attached to the carriage46with bolts extending through outer plates76and78. A working length158is defined on the linear beam150. A pair of spaced upper roller chain sprockets (not shown) of roller chain172are rotatably disposed on an upper end of the linear beam150, and a pair of spaced lower roller chain sprockets (not shown) of the roller chain172are rotatably disposed on a lower end of the linear beam150. The roller chain172engages the upper and lower roller chain sprockets. An outer side of the roller chain172engages with an inner side of gripper chain126. Lower roller chain sprockets incorporate a tensioner (not shown), of a type known in the art to keep the proper tension on roller chain172.

Gripper cylinders66may include a plurality of, and preferably four, hydraulic actuator cylinders (shown as185,188). As shown inFIG.2, the injector10may include upper cylinders185and lower cylinders188. In an embodiment, actuator mounting plates190and192having clevis lugs191and193, respectively, extending therefrom are rigidly mounted to outer plates76and78. The ends of cylinders185and188are attached to clevis lugs191and193, respectively. Actuator mounting plates190and192may be attached utilizing bolts or other means known in the art which extend through the actuator mounting plates190and192and the outer plates76and78of carriages72and74, respectively. The cylinders185,188may be simultaneously actuated to pull the outer plates76,78and corresponding carriages72and74respectively closer or push them apart. Pulling the carriages72and74closer causes the respective linear beams150of each carriage72and74to push the respective roller chains172on to the gripper chains126, thus causing the gripper blocks128to apply a higher gripping force on the outer diameter of the tubing18. On the other hand, pushing the carriages72and74apart in turn causes the linear beams150of each carriage72and74to push the respective roller chains172away from the gripper chains126, thus causing the gripper blocks128to apply a lower gripping force on the outer diameter of the tubing18.

In operation, when it is desired that tubing18be lowered, raised, or suspended in the well13, actuator cylinders185,188may be actuated until gripper blocks128engage tubing18. Gripper chains126may engage tubing18along the working length158of the linear beams150and a corresponding working length252of the roller chain172. Thus, gripper chains126will first contact the tubing18at an upper end of the working length158of linear beam150, and the contact between the tubing18and gripper chains126breaks away as the tubing18passes a lower end of working length158. For example, a gripper operating pressure may be adjusted by an operator in the operator cabin which adjusts the hydraulic pressure on each of the gripper cylinders185and188causing the cylinders to pull the carriages72and74towards each other. Thus, the pressure adjustment on the gripper cylinders185and188translates into a corresponding force that is applied on the linear beams150. The linear beams150in turn apply a uniform radial force on the gripper chains126by pressing the roller chains172against the gripper chains126resulting in the gripper blocks128being pressed against the coiled tubing18with an increased force.

Coiled tubing grippers128serve a critical purpose in all well intervention operations involving the insertion of coiled tubing string18down the wellbore13or pulling out of the coiled tubing string18up the wellbore13. The gripper blocks128are used to firmly grasp the coiled tubing string18as the gripper chains126drive the coiled tubing string18while running into a wellbore or pulling out of a wellbore. The force, F, exerted via the gripper blocks128on the coiled tubing string18needs to be high enough to prevent pipe slippage when a hoisting load is applied, but not so much as to damage the coiled tubing string18, for example, by either increasing ovality, deformation or increasing pipe fatigue. Thus, an actual gripping force applied by the grippers128onto the coiled tubing18should be between a minimum force value required to avoid pipe slippage and a maximum force value over which pipe damage may occur.

Generally, the minimum force that is to be applied by the gripper blocks128onto the coiled tubing18to avoid pipe slippage varies during a coiled tubing injector operation based on a coiled tubing hoisting load held by the injector10at any stage during the injector operation. Hoisting load generally depends at least on the weight of the coiled tubing18underneath the injector10which may be measured by a load cell disposed at the base of the injector10. For example, when coiled tubing18is being lowered into the wellbore13, as more coiled tubing18is lowered, the hoisting load on the injector increases due to the additional weight of the coiled tubing supported by the injector10. A higher hoisting load means a higher amount of traction force must be applied by the gripper blocks128onto the coiled tubing18to support the additional weight and avoid pipe slippage. Other parameters such as a friction factor of the coiled tubing18and wear of the gripper blocks may also need to be considered when determining the minimum force to be applied by the gripper blocks128at any stage during the operation of the coiled tubing injector10.

The maximum force that can be applied by the gripper blocks128onto the coiled tubing18without damaging the coiled tubing18also varies based on the properties of the section of the coiled tubing18currently passing through the injector10. For example, the wall thickness of the coiled tubing18may vary along the length of the coiled tubing18. In some cases, a coiled tubing18may have up to 8 or 10 different wall thicknesses along the entire length of the coiled tubing18. A lower amount of force may damage a section of the coiled tubing18having a lower wall thickness as compared to another section of the coiled tubing18that can withstand a higher amount of force due to a higher wall thickness.

Thus, since the minimum required force to avoid pipe slippage and the maximum recommended force to avoid pipe damage may change during an injector operation, the operating pressure on the gripper cylinders185and188may need to be monitored and adjusted accordingly throughout the injector operation so that the operating pressure on the gripper cylinders185and188translates into a gripping force applied by the gripper block128that lies between the current minimum and maximum force values recommended for the current section of the coiled tubing passing through the injector10.

In present coiled tubing injector systems, adjustment of the operating gripping pressure on the gripper cylinders185and188is performed manually. For example, an operator sitting in the operator cabin manually turns a valve provided in the operator cabin to adjust the gripping pressure of the gripper cylinders to a pressure value, based on past operator experience and some basic guidelines including pressure look-up tables. For example, in present injector systems, the operator has access to look-up tables that provide recommended minimum and maximum pressure values calculated based on properties of the coiled tubing18, surface equipment properties related to the injector10, and measured parameters related to a job being performed by the injector system100(e.g., hoisting load). For example, minimum pressure values provided in the look-up table may have been calculated based at least on a current hoisting load. Similarly, the maximum pressure values provided in the look-up table may have been calculated based at least on one or more coiled tubing parameters related to the portion of the coiled tubing passing the injector including the wall thickness of the coiled tubing. One or more other parameters relating to the injector system, coiled tubing properties and a current injector job being performed may also be used to calculate the minimum and maximum pressure values. The operator generally selects an operating gripping pressure to set for the gripper cylinders185and188at any stage during an injector operation by selecting a pressure value that is between the recommended minimum and maximum pressure values (e.g., as provided by the pressure look-up table(s)) based on past experience. The manually selected operating pressure is not always the most optimal pressure value for the given set of conditions as it is based on the operator's past experience and not based on concrete guidelines and/or data relating to optimal operating pressures for the given set of conditions.

Monitoring the coiled tubing injector operation and manually determining and setting of the operating pressures for the gripper cylinders185and188places considerable burden on the operator throughout the coiled tubing injector operation. Further, as the pressure values are manually determined based on operator's past experience and other crude guidelines, the operating gripping pressure set for the gripping cylinders185and188is not always the optimal pressure for the give set of conditions.

Aspects of the present disclosure discuss techniques for automatically monitoring one or more parameters related to a coiled tubing injector operation, intelligently selecting an appropriate gripping pressure for the gripping cylinders (e.g.,185and188) of the injector (e.g., injector10) and automatically setting the selected gripping pressure for the one or more gripping cylinders of the injector.

FIG.3illustrates a schematic diagram of an example system300for adjusting gripper pressure in a coiled tubing injector system100, in accordance with one or more embodiments of the present disclosure.

As shown inFIG.3, system300includes a data acquisition system (DAS)330, a gripper controller340and a hydraulic gripper control circuit350. DAS330may be configured to collect data relating to properties of the coiled tubing18, surface equipment properties including properties of the injector10and measured parameters during a coiled tubing injector operation. For example, as shown inFIG.3, system300may include a plurality of sensors310measuring various parameters related to the coiled tubing injector operation and feeding the measured data to the DAS330. As shown, sensors310may measure the hoisting load312, depth314, gripper pressure316and coiled tubing internal pressure318. Hoisting load312generally depends at least on the weight of the coiled tubing18underneath the injector10. The hoisting load312may be measured by a load cell disposed at the base of the injector10. The load cell provides a signal relative to weight of the coiled tubing18that has passed the injector10. Depth314may refer to a length of the coiled tubing18in the wellbore13. The depth314may be used to determine properties (e.g., coiled tubing wall thickness) of a section of the coiled tubing currently passing through the injector10. For example, the section of the coiled tubing18passing through the injector10may be identified based on the measured depth of the coiled tubing. The depth314of the coiled tubing18may be measured by a depth sensor. Gripper pressure316may represent a current pressure at which the gripper cylinders185and188are operating. The gripper pressure316may be measured by a pressure transducer. The coiled tubing internal pressure318may represent internal pressure of a fluid being pumped through the coiled tubing18at any given time. The internal pressure may be measured by an appropriate pressure transducer known in the art.

The measured values of hoisting load312, depth314, gripper pressure316and coiled tubing internal pressure318are fed into the DAS330. DAS330may be configured to additionally obtain several parameters related to properties of the coiled tubing18and the injector10. These parameters may include, but are not limited to outer diameter (D) of the coiled tubing18, thickness (t) of the coiled tubing18(including data relating to which sections of the coiled tubing18have what thickness), length (L) of the linear beam150, area (A) of the gripper cylinders185and188, efficiency (η) of the cylinder, coiled tubing axial stress (σx) caused by coiled tubing hoisting load312and coiled tubing internal pressure318, yield strength (σys) of the coiled tubing18. In an additional or alternative embodiment, the gripper controller340may be configured to directly obtain one or more of the above described parameters (including corresponding parameter values). For example, the gripper controller340may directly obtain measured values of hoisting load312, depth314, gripper pressure316and coiled tubing internal pressure318from respective sensors. The gripper controller340may also be configured to obtain and/or determine one or more parameters (including corresponding parameter values) relating to properties of the coiled tubing18and injector10.

DAS330may further be configured to obtain a historical data model342including data relating to target gripper pressures previously set for the gripper cylinders185and188for a given set of parameters and/or corresponding target gripping forces previously applied to the gripper chains126for the given set of parameters. The gripper pressures and gripping forces provided by the historical data model342for each set of parameter values include gripper pressure values and gripping force values that were determined to be optimal for the set of parameter values. For example, the gripping pressures and gripping forces provided by the historical model342did not result in pipe slippage or caused pipe damage when applied for the corresponding set of parameter values.

The historical data model342may include data collected over a given time period (days, weeks, months or years) while conducting coiled tubing injector operations by the coiled tubing system100and/or by one or more other coiled tubing injector systems having similar properties including coiled tubing properties (e.g., coiled tubing outer diameter (D), coiled tubing thickness (t), coiled tubing yield strength (σys) etc.) and surface equipment properties (e.g., injector properties including length (L) of the linear beam150, area (A) of the gripper cylinders185and188, efficiency (η) of the cylinder etc.).

For example, for a given set of parameters, the historical data model342may include target gripper pressures applied to the gripper cylinders185and188and corresponding target gripping forces resulting from the application of the target gripper pressure. The set of parameters may relate to a coiled tubing injector operation and may include one or more of hoisting load312, depth314, gripper pressure316, coiled tubing internal pressure318, outer diameter (D) of the coiled tubing18, thickness (t) of the coiled tubing18(including which sections of the coiled tubing18have what thickness), length (L) of the linear beam150, area (A) of the gripper cylinders185and188, efficiency (η) of the cylinder, coiled tubing axial stress (σx) caused by coiled tubing hoisting load312and coiled tubing internal pressure318, yield strength (σys) of the coiled tubing18. The historical data model342may include target gripper pressures and/or corresponding target gripping forces for different combinations of the one or more parameters. Further, the historical data model342may include target gripper pressures and/or corresponding target gripping forces for different combinations of values for a given set of parameters. For example, the historical data model342may include one or more previously set target gripper pressures and/or one or more corresponding target gripping forces applied for a given coiled tubing outer diameter (D), coiled tubing thickness (t), coiled tubing yield strength (σys), hoisting load312and internal pressure318.

In one embodiment, the DAS330may be configured to obtain the historical data model342(e.g., from a data server, another computing system, via download from a portable data storage device etc.) and send the obtained historical data model342to the gripper controller340. The gripper controller340may be configured to locally store the historical data model342in a memory of the gripper controller340. In an alternative embodiment, gripper controller340may be configured to directly obtain the historical data model342and store the obtained data model342in a local memory device of the gripper controller340.

Gripper controller340may be configured to monitor operation of the injector10based on values of one or more parameters obtained from the DAS330and determine an optimized gripper pressure to be set for the gripper cylinders185and188. The gripper controller340may be configured to generate an electronic signal346based on the determined optimized target gripper pressure and send out the electronic signal346to the hydraulic gripper control circuit350.

The gripper control circuit350is designed to adjust gripper pressure of the gripper cylinders185and188. As shown inFIG.3, the gripper control circuit350includes a hydraulic pump352that provides hydraulic pressure for operating the gripper control circuit350. An electronically controlled electro-hydraulic valve356may be configured to receive a set-point for the target gripper pressure from the gripper controller340as an electronic signal and, in response, automatically actuate the valve356to regulate the pressure in the circuit350until the target set-point is reached in the hydraulic gripper cylinders185and188. A manually controlled hydraulic valve354may be connected in parallel to the electro-hydraulic valve356and can be used to manually adjust the hydraulic pressure of the gripper cylinders185and188, thereby providing manual over-ride capability to an operator.

Gripper controller340may be configured to determine an operating pressure window for the gripper cylinders185and188at any stage during the injector operation, and then determine an optimized target gripper pressure to be applied to the gripper cylinders185and188based on the historical data model342. To determine the operating pressure window, the gripper controller340may be configured to determine a minimum gripper pressure that is to be applied to the gripper cylinders185,188to avoid pipe slippage and a maximum allowed gripper pressure that can be applied to the gripper cylinders185,188to avoid pipe damage. As described above, the gripper pressure set for the gripper cylinders185and188controls the gripping force applied to the gripper chains126. Thus, the operating window for the gripper pressure defines an operating window for the gripping force. The gripper controller340may select a target gripper pressure that lies within the determined pressure window and is optimized based on the historical data model342. By determining the gripper pressure window, gripper controller340avoids the target gripper pressure from being set too low resulting in pipe slippage or set too high to damage the coiled tubing18. The historical data model342provides the gripper controller benefit of past experiences under similar conditions and a concrete guide to what target gripping pressures can be optimal for the given conditions. For example, as described above, the historical data model provides gripper pressure values and/or corresponding gripping force values that were determined to be optimal for a given set of conditions (e.g., parameter values). Optimizing the target gripper pressure to be set for the gripper cylinders185and188based on the historical data model342helps minimize pipe damage. In one or more embodiments, the gripper controller340may be configured to continuously monitor one or more parameters obtained from the DAS330and adjust the target gripper pressure as needed when an injector operation is in progress. For example, the gripper controller340may be configured to determine and adjust the target gripper periodically, randomly or based on a pre-selected schedule. The entire operation including monitoring the parameters related to the operation of the injector10, determining the gripper pressure window, selecting an optimized target gripper pressure and adjusting the target gripper pressure for the gripper cylinders185and188is designed to be fully automatic and not needing operator intervention. Thus, the disclosed system and methods significantly reduce operator burden. Further, by determining optimized gripper pressure values in accordance with techniques disclosed herein, the disclosed system and methods avoid the gripper pressure from being set too low resulting in pipe slippage or too high resulting in pipe damage. Further, the adjustment of the gripper pressure throughout the operation of the injector10may ensure minimal damage to the coiled tubing18.

Gripper controller340may be configured to determine the minimum gripper pressure that is to be applied to the gripper cylinders185and188in accordance with methods known in the art. For example, the gripper controller340may determine the minimum gripper pressure at any time during the operation of the injector10based at least on the measured hoisting load312at that time as received from the DAS330. In one embodiment, the gripper controller340may calculate a minimum gripping force that is to be applied to the gripper chains126and then calculate a corresponding minimum gripper pressure that is to be applied to the gripper cylinders185and188as a function of the minimum gripping force.

Gripper controller340may be configured to determine the maximum allowed gripper pressure that can be applied to the gripper cylinders185and188based on values of a plurality of parameters obtained from the DAS330. In one embodiment, the gripper controller340may calculate a maximum gripping force that can be applied by the gripper chains126onto the coiled tubing18in accordance with equation (1) as shown below.

Fy—the maximum gripping force that can be applied to the gripper chains126;

σx—coiled tubing pipe axial stress caused by hoisting load312and internal pressure318of the coiled tubing18;

σys—yield strength of the coiled tubing18;

C1—a constant accounting for properties of the coiled tubing18including one or more of outer diameter and wall thickness of the coiled tubing18; and

C2—a constant accounting for surface measurements of one or more parameters including one or more of hoisting load312and internal pressure318of the coiled tubing18.

It may be noted that, unlike the above equation (1) used to calculate the maximum griping force in accordance with embodiments of the present disclosure, present systems do not consider the hoisting load312and/or the internal pressure318of the coiled tubing18to calculate the maximum gripper pressure or the maximum gripping force that can be applied to the injector10. Both the hoisting load312and internal pressure318of the coiled tubing18at any time during an injector operation can affect the maximum gripper pressure or resulting gripping force that can be applied to the injector10. Thus, not considering the hoisting load312and/or internal pressure318when calculating the maximum gripper pressure or resulting gripping force can lead to an erroneous (or less accurate) determination of the maximum gripper pressure or the maximum gripping force which can potentially lead to pipe damage. The weight on the coiled tubing18as a result of the hoisting load312and the internal pressure318of the coiled tubing18create axial stresses on the coiled tubing18which affect the maximum amount of gripping force that can be applied to the coiled tubing18before it starts to damage. For example, a larger hoisting load may create a higher axial stress on the coiled tubing pipe which may lower maximum gripping force. A higher internal pressure of a fluid inside the pipe opposes at least a portion of the gripping force applied onto the pipe by the gripper chains126, which may raise the maximum gripping force that can be applied to the coiled tubing pipe. Thus, considering the hoisting load312and the internal pressure318of the coiled tubing18when calculating the maximum gripping force may yield a more accurate value of the maximum gripping force which may help avoid damage to the coiled tubing18.

The gripper controller340may determine a maximum gripper pressure as a function of the maximum gripper force (Fy) according to equation (2) as shown below.

Py—the maximum gripper pressure that can be set for the gripper cylinders185and188;

A—area of the gripper cylinders185and188; and

η—efficiency of the gripper cylinders185and188.

Once the minimum and maximum gripping forces are calculated, the gripper controller340may determine an estimated gripping force that can be applied to the gripper chains126. In one or more embodiments, the gripper controller340selects an estimated gripping force value that lies within an operating gripping force window defined by the calculated minimum and maximum gripping force. For example, the gripper controller340may be configured to select a value of the estimated gripping force as a pre-configured percentage of the calculated maximum gripping force so that the selected estimated gripping force lies within the gripping force window. In one embodiment, the percentage of the maximum gripping force may be configured by the operator.

The gripper controller340may be configured to determine a target gripping force that is to be applied to the gripper chains126, by adjusting the estimated gripping force based on the historical data model342. In one embodiment, the gripper controller340may adjust the estimated gripping force based on one or more previously applied target gripping forces (as provided by the historical data model342) corresponding to the same or similar parameter values based on which the gripper controller340calculated the minimum gripper force, the maximum gripper force and determined the estimated gripping force. For example, the gripper controller340may extract from the historical data model342one or more previously applied target gripping force values corresponding to the same coiled tubing outer diameter, coiled tubing thickness, linear beam length, hoisting load and internal pressure based on which the gripper controller340calculated the minimum gripper force, the maximum gripper force and determined the estimated gripping force. The previously applied one or more gripping forces extracted from the historical data model342may be representative of optimal values of the gripping forces applied on previous occasions (e.g., to injector10or other injectors having similar properties) for the same or similar parameter values.

In one or more embodiments, the gripper controller340may be configured to determine an adjustment factor by comparing the estimated target gripping force and the one or more previously applied target gripping forces from the historical data model342. The gripper controller340may be configured to apply the adjustment factor to the estimated gripping force to determine the target gripping force to be applied to the gripper chains126. The gripper controller340may determine the adjustment factor as a difference between the estimated gripping force and at least one previously applied target gripping force from the historical data model. This difference may be used to adjust the value of the estimated gripping force and determine the target gripping force to apply to the gripping chains126. For example, when the estimated gripping force is3000newton and a previously applied target gripping force from the historical data model342is 3500 newton, the adjustment factor can be determined as 500, which can be added to the estimated gripping force to determine a target gripping force of 3500 newton. In one embodiment, when the historical data model provides several values of previously applied target gripping forces for the same set of parameter values, the grippier controller340may calculate an average of the previously applied values and determine the adjustment factor as a difference between the estimated gripping force and the average value of the previously applied target gripping forces. In one embodiment, the gripper controller340may be configured to limit the adjustment factor to a maximum value (e.g., a maximum amount of adjustment) to avoid large adjustments from being made at one time.

Once the target gripping force is determined, the gripper controller340may determine the target gripping pressure as a function of the target gripping force. The gripper controller may send an electronic signal to the gripper control circuit350(e.g., to electro-hydraulic valve356) to adjust the gripping pressure of the gripper cylinders185and188to the determined target gripper pressure. For example, the gripper controller340may be configured to calculate the target gripper pressure according to equation (3) as shown below.

PT—the target gripper pressure that is to be set for the gripper cylinders185and188;

FT—the target gripping force that is to be applied by the gripper chains onto the coiled tubing18;

A—area of the gripper cylinders185and188; and

η—efficiency of the gripper cylinders185and188.

The gripper controller340may be configured to continuously monitor parameters related to the injector operation and fine tune the gripper pressure as needed (e.g., by determining target gripping forces and gripper pressures as described above) to ensure that an optimal force continues to be applied by the gripper chains126onto the coiled tubing18as values of one or more parameters change during the duration of the injector operation.

In one or more embodiments, the gripper controller340may be configured to add the determined target gripping force and the corresponding target gripper pressure to the historical data model342for subsequent use in determining gripping force and gripper pressure.

In one or more embodiments, the gripper controller340may be implemented by an artificial intelligence (AI) model. The AI model may be trained using historical data relating to the previously set gripper pressures and corresponding applied gripping forces from the historical data model342. The trained AI model may be used to determine optimized gripping forces and gripper pressures in real world conditions. The gripper controller340may be configured to constantly update the AI model by adding newly set gripper pressures and corresponding applied gripping forces to the historical data model342and updating the training of the AI model based on the updated historical data model342. As more real-time data relating to gripper pressures and gripping forces is added to the historical data model342, the AI model may update itself thereby increasing the accuracy of determining optimized gripping force and gripper pressure values for a given set of parameter values.

FIG.4illustrates example operation400for determining an optimized gripper pressure to be applied for an injector10, in accordance with one or more embodiments of the present disclosure. Operations400may be implemented by a gripper controller340as discussed above with reference toFIG.3.

At step402, gripper controller340obtains a current set of parameters related to lowering the coiled tubing18into a wellbore13or pulling out the coiled tubing18from the wellbore13.

As described above, a coiled tubing injector system100includes an injector10(also referred to as an injector head) mounted above a wellhead12. Injector10utilizes a pair of opposed endless drive chains or gripper chains126which are arranged in a common plane. Each of the gripper chains126has a multitude of gripper blocks128attached therealong. The gripper chains126are driven by respective drive sprockets110which are in turn powered by a reversible hydraulic motor. The opposed gripper chains126, via the gripper blocks128, sequentially grasp the coiled tubing18that is positioned between the opposed gripper chains126. When the gripper chains126are in motion, each gripper chain126has a gripper block128that is coming into contact with the coiled tubing18as another gripper block128on the same gripper chain126is breaking contact with the coiled tubing18. This continues in an endless fashion as the gripper chains126are driven to force the coiled tubing18into or out of the wellbore13, depending on the direction in which the drive sprockets110are rotated. Each gripper chain126is provided with a predetermined amount of slack which allows the gripper chain126to be biased against the coiled tubing18to inject the coiled tubing18into and out of the wellbore13. This biasing is accomplished with an endless roller chain172disposed inside each gripper chain126. Each roller chain172engages sprockets rotatably mounted on a respective linear beam150. A linkage and hydraulic gripper cylinder (e.g.,185and188) mechanism allows the linear beams150to be moved toward one another so that each roller chain172is moved against its corresponding gripper chain126such that the coiled tubing18facing portion of the gripper chain126is moved toward the coiled tubing18so that the gripper blocks128can engage the tubing18and move it through the injector10. The gripper blocks128engage the tubing18along a working length158of the linear beam150. Each gripper chain126has a gripper block128that contacts the tubing18at the top of the working length158as a gripper block128on the same gripper chain126is breaking contact at a bottom of the working length158of the linear beam150.

In operation, when it is desired that tubing18be lowered, raised, or suspended in the well13, actuator cylinders185,188may be actuated until gripper blocks128engage tubing18. Gripper chains126may engage tubing18along the working length158of the linear beams150and a corresponding working length252of the roller chain172. Thus, gripper chains126will first contact the tubing18at an upper end of the working length158of linear beam150, and the contact between the tubing18and gripper chains126breaks away as the tubing18passes a lower end of working length158. For example, a gripper operating pressure may be adjusted by an operator in the operator cabin which adjusts the hydraulic pressure on each of the gripper cylinders185and188causing the cylinders to pull the carriages72and74towards each other. Thus, the pressure adjustment on the gripper cylinders185and188translates into a corresponding force that is applied on the linear beams150. The linear beams150in turn apply a uniform radial force on the gripper chains126by pressing the roller chains172against the gripper chains126resulting in the gripper blocks128being pressed against the coiled tubing18with an increased force. In one or more embodiments, the arrangement of components including the linear beam150, roller chains172and gripper cylinders185and188that help generate a gripping force applied to the gripper chains126as a result of hydraulic pressure set for the gripper cylinders185and188may generally be referred to as the gripper system.

As described above with reference toFIG.3, the gripper controller340may be configured to monitor operation of the injector10based on values of one or more parameters obtained from the DAS330and determine an optimized gripper pressure to be set for the gripper cylinders185and188. The gripper controller340may be configured to generate an electronic signal346based on the determined optimized target gripper pressure and send out the electronic signal346to the hydraulic gripper control circuit350.

In one embodiment, the gripper controller340obtains at least a portion of the current set of parameters (e.g., including parameter values of one or more of the parameters) from the DAS330. DAS330may be configured to collect data including several parameters (and corresponding parameter values) relating to properties of the coiled tubing18, surface equipment properties including properties of the injector10and measured parameters during a coiled tubing injector operation. For example, DAS330may collect measured values of one or more parameters including hoisting load312, depth314, gripper pressure316and coiled tubing internal pressure318from respective sensors measuring these parameters. DAS330may be configured to additionally obtain several parameters (and corresponding parameter values) related to properties of the coiled tubing18and the injector10. These parameters may include, but are not limited to outer diameter (D) of the coiled tubing18, thickness (t) of the coiled tubing18(including data relating to which sections of the coiled tubing18have what thickness), length (L) of the linear beam150, area (A) of the gripper cylinders185and188, efficiency (η) of the cylinder, coiled tubing axial stress (σx) caused by coiled tubing hoisting load312and coiled tubing internal pressure318, yield strength (σys) of the coiled tubing18. In an additional or alternative embodiment, the gripper controller340may directly obtain one or more of the above described parameters (including corresponding parameter values). For example, the gripper controller340may directly obtain measured values of hoisting load312, depth314, gripper pressure316and coiled tubing internal pressure318from respective sensors. The gripper controller340may also obtain and/or determine one or more parameters (including corresponding parameter values) relating to properties of the coiled tubing18and injector10.

The current set of parameters obtained by the gripper controller340may include one or more of the above described parameters (including values of the one or more parameters) relating to a current injector job and/or a current stage of the injector job being performed by the injector10. For example, the current set of parameters may include values of one or more parameters relating to properties of a section of coiled tubing18currently passing through the injector10.

At step406, the gripper controller340determines a minimum gripper pressure to be set for at least one gripper cylinder185and188, based on the current set of parameters (including values of the parameters) obtained by the gripper controller340.

As described above, gripper controller340may be configured to determine an operating pressure window for the gripper cylinders185and188at any stage during the injector operation, and then determine an optimized target gripper pressure to be applied to the gripper cylinders185and188based on the historical data model342. To determine the operating pressure window, the gripper controller340may be configured to determine a minimum gripper pressure that is to be applied to the gripper cylinders185,188to avoid pipe slippage and a maximum allowed gripper pressure that can be applied to the gripper cylinders185,188to avoid pipe damage. As described above, the gripper pressure set for the gripper cylinders185and188controls the gripping force applied to the gripper chains126. Thus, the operating window for the gripper pressure defines an operating window for the gripping force. The gripper controller340may select a target gripper pressure that lies within the determined pressure window and is optimized based on the historical data model342.

Gripper controller340may be configured to determine the minimum gripper pressure that is to be applied to the gripper cylinders185and188in accordance with methods known in the art. For example, the gripper controller340may determine the minimum gripper pressure at any time during the operation of the injector10based at least on the measured hoisting load312at that time as received from the DAS330. In one embodiment, the gripper controller340may calculate a minimum gripping force that is to be applied to the gripper chains126and then calculate a corresponding minimum gripper pressure that is to be applied to the gripper cylinders185and188as a function of the minimum gripping force.

At step406, the gripper controller340determines a maximum gripper pressure that can be set for the at least one gripper cylinder185and188based on the current set of parameters (including values of the parameters).

Gripper controller340may be configured to determine the maximum allowed gripper pressure that can be applied to the gripper cylinders185and188based on values of a plurality of parameters obtained from the DAS330. In one embodiment, the gripper controller340may calculate a maximum gripping force that can be applied by the gripper chains126onto the coiled tubing18in accordance with equation (1) as shown below.

Fy—the maximum gripping force that can be applied to the gripper chains126;

σx—coiled tubing pipe axial stress caused by hoisting load312and internal pressure318of the coiled tubing18;

σys—yield strength of the coiled tubing18;

C1—a constant accounting for properties of the coiled tubing18including one or more of outer diameter and wall thickness of the coiled tubing18; and

C2—a constant accounting for surface measurements of one or more parameters including one or more of hoisting load312and internal pressure318of the coiled tubing18.

The gripper controller340may determine a maximum gripper pressure as a function of the maximum gripper force (Fy) according to equation (2) as shown below.

Py—the maximum gripper pressure that can be set for the gripper cylinders185and188;

A—area of the gripper cylinders185and188; and

η—efficiency of the gripper cylinders185and188.

At step408, the gripper controller340selects a target gripper pressure between the minimum gripper pressure and the maximum gripper pressure based on a historical data model342including, corresponding to the current set of parameters, one or more of a plurality of target gripping forces previously applied to the gripper chains126and a plurality of corresponding target gripper pressures previously set for the gripper cylinders185and188.

At step410, the gripper controller340sets the determined target gripper pressure for the gripper cylinders185and188to apply a corresponding gripping force to the gripper chains126.

As described above, once the minimum and maximum gripping forces are calculated, the gripper controller340may determine an estimated gripping force that can be applied to the gripper chains126. In one or more embodiments, the gripper controller340selects an estimated gripping force value that lies within an operating gripping force window defined by the calculated minimum and maximum gripping force. For example, the gripper controller340may be configured to select a value of the estimated gripping force as a pre-configured percentage of the calculated maximum gripping force so that the selected estimated gripping force lies within the gripping force window. In one embodiment, the percentage of the maximum gripping force may be configured by the operator.

The gripper controller340may be configured to determine a target gripping force that is to be applied to the gripper chains126, by adjusting the estimated gripping force based on the historical data model342. In one embodiment, the gripper controller340may adjust the estimated gripping force based on one or more previously applied target gripping forces (as provided by the historical data model342) corresponding to the same or similar parameter values based on which the gripper controller340calculated the minimum gripper force, the maximum gripper force and determined the estimated gripping force. For example, the gripper controller340may extract from the historical data model342one or more previously applied target gripping force values corresponding to the same coiled tubing outer diameter, coiled tubing thickness, linear beam length, hoisting load and internal pressure based on which the gripper controller340calculated the minimum gripper force, the maximum gripper force and determined the estimated gripping force. The previously applied one or more gripping forces extracted from the historical data model342may be representative of optimal values of the gripping force applied on previous occasions (e.g., to injector10or other injectors having similar properties) for the same or similar parameter values.

In one or more embodiments, the gripper controller340may be configured to determine an adjustment factor by comparing the estimated target gripping force and the one or more previously applied target gripping forces from the historical data model342. The gripper controller340may be configured to apply the adjustment factor to the estimated gripping force to determine the target gripping force to apply to the gripper chains126. The gripper controller340may determine the adjustment factor as a difference between the estimated gripping force and at least one previously applied target gripping force from the historical data model. This difference may be used to adjust the value of the estimated gripping force and determine the target gripping force to apply to the gripping chains126. For example, when the determined estimated gripping force is 3000 newton and a previously applied target gripping force from the historical data model342is 3500 newton, the adjustment factor can be determined as 500, which can be added to the estimated gripping force to determine a target gripping force of 3500 newton. In one embodiment, when the historical data model provides several values of previously applied target gripping forces for the same set of parameter values, the grippier controller340may calculate an average of the previously applied values and determine the adjustment factor as a difference between the estimated gripping force and the average value of the previously applied target gripping forces. In one embodiment, the gripper controller340may be configured to limit the adjustment factor to a maximum value (e.g., a maximum amount of adjustment) to avoid large adjustments from being made at one time.

Once the target gripping force is determined, the gripper controller340may determine the target gripping pressure as a function of the determined target gripping force. The gripper controller may send an electronic signal to the gripper control circuit350(e.g., to electro-hydraulic valve356) to adjust the gripping pressure of the gripper cylinders185and188to the determined target gripper pressure. For example, the gripper controller340may be configured to calculate the target gripper pressure according to equation (3) as shown below.

PT—the target gripper pressure that is to be set for the gripper cylinders185and188;

FT—the target gripping force that is to be applied by the gripper chains onto the coiled tubing18;

A—area of the gripper cylinders185and188; and

η—efficiency of the gripper cylinders185and188.

The gripper controller340may be configured to continuously monitor parameters related to the injector operation and fine tune the gripper pressure as needed (e.g., by determining target gripping forces and gripper pressures as described above) to ensure that an optimal force continues to be applied by the gripper chains126onto the coiled tubing18as values of one or more parameters change during the duration of the injector operation.

In one or more embodiments, the gripper controller340may be configured to add the determined target gripping force and the corresponding target gripper pressure to the historical data model342for subsequent use in determining gripping force and gripper pressure.

In one or more embodiments, the gripper controller340may be implemented by an artificial intelligence (AI) model. The AI model may be trained using historical data relating to the previously set gripper pressures and corresponding applied gripping forces from the historical data model342. The trained AI model may be used to determine optimized gripping forces and gripper pressures in real world conditions. The gripper controller340may be configured to constantly update the AI model by adding newly set gripper pressures and corresponding applied gripping forces to the historical data model342and updating the training of the AI model based on the updated historical data model342. As more real-time data relating to gripper pressures and gripping forces is added to the historical data model342, the AI model may update itself thereby increasing the accuracy of determining optimized gripping force and gripper pressure values for a given set of parameter values.

FIG.5is a diagram illustrating an example information handling system500, for example, for use with coiled tubing injector system100ofFIG.1, injector10ofFIG.2and/or system300shown inFIG.3, in accordance with one or more embodiments of the present disclosure. The DAS330and/or the gripper controller340discussed above with reference toFIGS.3and4may take a form similar to the information handling system500. A processor or central processing unit (CPU)501of the information handling system500is communicatively coupled to a memory controller hub (MCH) or north bridge502. The processor501may include, for example a microprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), or any other digital or analog circuitry configured to interpret and/or execute program instructions and/or process data. Processor501may be configured to interpret and/or execute program instructions or other data retrieved and stored in any memory such as memory504or hard drive507. Program instructions or other data may constitute portions of a software or application, for example application558or data554, for carrying out one or more methods described herein. Memory504may include read-only memory (ROM), random access memory (RAM), solid state memory, or disk-based memory. Each memory module may include any system, device or apparatus configured to retain program instructions and/or data for a period of time (for example, non-transitory computer-readable media). For example, instructions from a software or application558or data554may be retrieved and stored in memory504for execution or use by processor501. In one or more aspects, the memory504or the hard drive507may include or comprise one or more non-transitory executable instructions that, when executed by the processor501cause the processor501to perform or initiate one or more operations or steps. The information handling system500may be preprogrammed or it may be programmed (and reprogrammed) by loading a program from another source (for example, from a CD-ROM, from another computer device through a data network, or in another manner).

The data554may include treatment data, geological data, fracture data, seismic or micro seismic data, data relating to properties of the coiled tubing18, data relating to properties of the injector10, data relating to measured parameters during a coiled tubing injector operation or any other appropriate data. In one or more aspects, a memory of a computing device includes additional or different data, application, models, or other information. In one or more aspects, the data554may include geological data relating to one or more geological properties of the subterranean formation. For example, the geological data may include information on the wellbore, completions, or information on other attributes of the subterranean formation. In one or more aspects, the geological data includes information on the lithology, fluid content, stress profile (for example, stress anisotropy, maximum and minimum horizontal stresses), pressure profile, spatial extent, or other attributes of one or more rock formations in the subterranean zone. The geological data may include information collected from well logs, rock samples, outcroppings, seismic or microseismic imaging, or other data sources.

The one or more applications558may comprise one or more software applications, one or more scripts, one or more programs, one or more functions, one or more executables, or one or more other modules that are interpreted or executed by the processor501. The one or more applications558may include one or more machine-readable instructions for performing one or more of the operations related to any one or more aspects of the present disclosure. The one or more applications558may include machine-readable instructions for determining optimized gripper pressures and gripping forces, as described with reference toFIGS.1-4. The one or more applications558may obtain input data, such as data relating to properties of the coiled tubing18, data relating to properties of the injector10, data relating to measured parameters during a coiled tubing injector operation, seismic data, well data, treatment data, geological data, fracture data, or other types of input data, from the memory504, from another local source, or from one or more remote sources (for example, via the one or more communication links514). The one or more applications558may generate output data and store the output data in the memory504, hard drive507, in another local medium, or in one or more remote devices (for example, by sending the output data via the communication link514).

Modifications, additions, or omissions may be made toFIG.5without departing from the scope of the present disclosure. For example,FIG.5shows a particular configuration of components of information handling system500. However, any suitable configurations of components may be used. For example, components of information handling system500may be implemented either as physical or logical components. Furthermore, in one or more aspects, functionality associated with components of information handling system500may be implemented in special purpose circuits or components. In other aspects, functionality associated with components of information handling system500may be implemented in configurable general purpose circuit or components. For example, components of information handling system500may be implemented by configured computer program instructions.

Memory controller hub502may include a memory controller for directing information to or from various system memory components within the information handling system500, such as memory504, storage element506, and hard drive507. The memory controller hub502may be coupled to memory504and a graphics processing unit (GPU)503. Memory controller hub502may also be coupled to an I/O controller hub (ICH) or south bridge505. I/O controller hub505is coupled to storage elements of the information handling system500, including a storage element506, which may comprise a flash ROM that includes a basic input/output system (BIOS) of the computer system. I/O controller hub505is also coupled to the hard drive507of the information handling system500. I/O controller hub505may also be coupled to an I/O chip or interface, for example, a Super I/O chip508, which is itself coupled to several of the I/O ports of the computer system, including a keyboard509, a mouse510, a monitor512and one or more communications link514. Any one or more input/output devices receive and transmit data in analog or digital form over one or more communication links514such as a serial link, a wireless link (for example, infrared, radio frequency, or others), a parallel link, or another type of link. The one or more communication links514may comprise any type of communication channel, connector, data communication network, or other link. For example, the one or more communication links514may comprise a wireless or a wired network, a Local Area Network (LAN), a Wide Area Network (WAN), a private network, a public network (such as the Internet), a wireless fidelity or WiFi network, a network that includes a satellite link, or another type of data communication network.

One or more embodiments of the present disclosure provide a system including a coiled tubing injector and an automatic gripper controller coupled to the coiled tubing injector. The coiled tubing injector includes at least two gripper chains, wherein each gripper chain has a plurality of gripper blocks for gripping a coiled tubing in a gripping zone between the gripper chains; and a gripper system for generating a gripping force applied to the at least two gripper chains, wherein the gripper system applies gripping force to the at least two gripper chains by adjusting gripper pressure of at least one hydraulic gripper cylinder. The gripper controller is configured to select a target gripper pressure between a minimum gripper pressure and a maximum gripper pressure; and set the target gripper pressure for the at least one gripper cylinder to apply a corresponding gripping force to the at least two gripper chains.

In one or more embodiments, the automatic gripper controller is configured to select the target gripper pressure based on a historical data model, wherein the historical data model includes, corresponding to a current set of parameters, one or more of a plurality of target gripping forces previously applied to the at least two gripper chains and a plurality of corresponding target gripper pressures previously set for the at least one gripper cylinder, wherein the current set of parameters is related to lowering the coiled tubing into a wellbore or pulling out the coiled tubing from the wellbore.

In one or more embodiments, the plurality of target gripper pressures of the historical data model comprises corresponding to the current set of parameters one or more target gripper pressures previously set for at least one second gripper cylinder of a second coiled tubing injector at a different wellbore

In one or more embodiments, the plurality of target gripper pressures of the historical data model comprises corresponding to the current set of parameters one or more target gripper pressures previously set manually by an operator of the coiled tubing injector.

In one or more embodiments, the automatic gripper controller is further configured to determine the minimum gripper pressure to be set for the at least one gripper cylinder based on a current set of parameters related to lowering the coiled tubing into a wellbore or pulling out the coiled tubing from the wellbore; and determine the maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters.

In one or more embodiments, the automatic gripper controller is configured to determine the maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters by:

determining a maximum gripping force that can be applied to the at least two gripper chains based on the current set of parameters as:

Fy—the maximum gripping force that can be applied to the at least two gripper chains; and the current set of parameters include:

σx—coiled tubing pipe axial stress caused by coiled tubing pipe hoisting load and internal pressure;

C1—a constant accounting for properties of the coiled tubing including one or more of coiled tubing outer diameter and a wall thickness of the coiled tubing; and

C2—a constant accounting for surface measurements of one or more parameters including one or more of hoisting load and internal pressure of the coiled tubing

In one or more embodiments, the automatic gripper controller is configured to determine the maximum gripper pressure as:

Py—the maximum gripper pressure that can be set for the at least one gripper cylinder; and

the current set of parameters further includes:

A—area of the at least one gripper cylinder; and

η—efficiency of the gripper cylinder.

In one or more embodiments, the automatic gripper controller is configured to select the target gripper pressure by: determining an estimated gripping force to be applied to the at least two gripper chains as a percentage of the determined maximum gripping force and above a minimum gripping force that is to be applied to the at least two gripper chains, wherein the minimum gripping force is a function of the determined minimum gripping pressure; determining a target gripping force that is to be applied to the at least two gripper chains by adjusting the estimated gripping force based on the plurality of previously applied target gripping forces corresponding to the current set of parameters; and determining the target gripper pressure as a function of the target gripping force.

In one or more embodiments, the percentage of the determined maximum gripping force is pre-configured.

In one or more embodiments, the automatic gripper controller is configured to determine the target gripping force by: determining an adjustment factor based on a difference between the estimated gripping force and at least one previously applied target gripping force from the historical data model; and applying the adjustment factor to the estimated gripping force to determine the target gripping force.

In one or more embodiments, the automatic gripper controller is further configured to add one or more of the determined target gripping force and target gripper pressure to the historical data model.

One or more embodiments of the present disclosure provide a method for operating a coiled tubing injector, comprising: automatically selecting a target gripper pressure between a minimum gripper pressure and a maximum gripper pressure, wherein a gripping force is applied to at least two gripper chains of the coiled tubing injector by adjusting gripper pressure of at least one gripper cylinder of the coiled tubing injector; and automatically setting the target gripper pressure for the at least one gripper cylinder to apply a corresponding gripping force to the at least two gripper chains.

In one or more embodiments, the target gripper pressure is selected based on a historical data model, wherein the historical data model includes, corresponding to a current set of parameters, one or more of a plurality of target gripping forces previously applied to the at least two gripper chains and a plurality of corresponding target gripper pressures previously set for the at least one gripper cylinder.

In one or more embodiments, the method further includes determining a minimum gripper pressure to be set for the at least one gripper cylinder based on a current set of parameters related to lowering a coiled tubing into a wellbore or pulling out the coiled tubing from the wellbore; and determining a maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters.

In one or more embodiments, wherein determining the maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters comprises: determining a maximum gripping force that can be applied to the at least two gripper chains based on the current set of parameters as:

Fy—the maximum gripping force that can be applied to the at least two gripper chains; and

the current set of parameters include:

σx—coiled tubing pipe axial stress caused by coiled tubing pipe hoisting load and internal pressure;

C1—a constant accounting for properties of the coiled tubing including one or more of coiled tubing outer diameter and a wall thickness of the coiled tubing; and

C2—a constant accounting for surface measurements of one or more parameters including one or more of hoisting load and internal pressure of the coiled tubing

In one or more embodiments, wherein determining the maximum gripper pressure further comprises determining the maximum gripper pressure as:

Py—the maximum gripper pressure that can be set for the at least one gripper cylinder; and

the current set of parameters further includes:

A—area of the at least one gripper cylinder; and

η—efficiency of the gripper cylinder.

In one or more embodiments, wherein selecting the target gripper pressure comprises: determining an estimated gripping force to be applied to the at least two gripper chains as a percentage of the determined maximum gripping force and above a minimum gripping force that is to be applied to the at least two gripper chains, wherein the minimum gripping force is a function of the determined minimum gripping pressure; determining a target gripping force that is to be applied to the at least two gripper chains by adjusting the estimated gripping force based on the plurality of previously applied target gripping forces corresponding to the current set of parameters; and determining the target gripper pressure as a function of the target gripping force.

In one or more embodiments, wherein the method further comprises pre-selecting the percentage of the determined maximum gripping force.

In one or more embodiments, wherein determining the target gripping force comprises: determining an adjustment factor based on a difference between the estimated gripping force and at least one previously applied target gripping force from the historical data model; applying the adjustment factor to the estimated gripping force to determine the target gripping force.

One or more embodiments of the present disclosure provides a computer-readable medium storing instructions which when processed by at least one processor perform a method for operating a coiled tubing injector comprising: automatically selecting a target gripper pressure between a minimum gripper pressure and a maximum gripper pressure, wherein a gripping force is applied to at least two gripper chains of the coiled tubing injector by adjusting gripper pressure of at least one gripper cylinder of the coiled tubing injector; and automatically setting the target gripper pressure for the at least one gripper cylinder to apply a corresponding gripping force to the at least two gripper chains.

In one or more embodiments, the target gripper pressure is selected based on a historical data model, wherein the historical data model includes, corresponding to a current set of parameters, one or more of a plurality of target gripping forces previously applied to the at least two gripper chains and a plurality of corresponding target gripper pressures previously set for the at least one gripper cylinder.

In one or more embodiments, the computer-readable medium further includes instructions for determining a minimum gripper pressure to be set for the at least one gripper cylinder based on a current set of parameters related to lowering a coiled tubing into a wellbore or pulling out the coiled tubing from the wellbore; and determining a maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters.

In one or more embodiments, determining the maximum gripper pressure that can be set for the at least one gripper cylinder based on the current set of parameters comprises: determining a maximum gripping force that can be applied to the at least two gripper chains based on the current set of parameters as:

Fy—the maximum gripping force that can be applied to the at least two gripper chains; and

the current set of parameters include:

σx—coiled tubing pipe axial stress caused by coiled tubing pipe hoisting load and internal pressure;

C1—a constant accounting for properties of the coiled tubing including one or more of coiled tubing outer diameter and a wall thickness of the coiled tubing; and

C2—a constant accounting for surface measurements of one or more parameters including one or more of hoisting load and internal pressure of the coiled tubing.

In one or more embodiments, determining the maximum gripper pressure further comprises determining the maximum gripper pressure as:

Py—the maximum gripper pressure that can be set for the at least one gripper cylinder; and

the current set of parameters further includes:

A—area of the at least one gripper cylinder; and

η—efficiency of the gripper cylinder.

In one or more embodiments, selecting the target gripper pressure comprises: determining an estimated gripping force to be applied to the at least two gripper chains as a percentage of the determined maximum gripping force and above a minimum gripping force that is to be applied to the at least two gripper chains, wherein the minimum gripping force is a function of the determined minimum gripping pressure; determining a target gripping force that is to be applied to the at least two gripper chains by adjusting the estimated gripping force based on the plurality of previously applied target gripping forces corresponding to the current set of parameters; and determining the target gripper pressure as a function of the target gripping force.

In one or more embodiments, determining the target gripping force comprises: determining an adjustment factor based on a difference between the estimated gripping force and at least one previously applied target gripping force from the historical data model; applying the adjustment factor to the estimated gripping force to determine the target gripping force.

Therefore, the present disclosure is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present disclosure may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present disclosure. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. The indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the elements that it introduces.