Winch control system to prevent cable damage

Abstract

Cable tension is continually "mapped" at every position on a winch. A crush ratio is calculated, stored, and / or displayed. The winch operation is adjusted by a drive to control the cable tension of the "over" layer as it is being applied to remain below a value. The value is calculated by multiplying the tension of the cable on the "under" layer by a maximum crush ratio. The drive also adjusts the cable tension to a value that is based on a predetermined spooling profile. The drive can include a powered capstan.

Description

WINCH CONTROL SYSTEM TO PREVENT CABLE DAMAGECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to US provisional application serial no. 63 / 642,420, filed on May 3, 2024, and incorporated herein by reference.FIELD OF THE INVENTION

[0002] The disclosure relates generally to cable winches in the oilfield, marine, utility, and defense industries. The disclosure relates more specifically to oilfield operations where a cable, typically a wireline cable, is connected to downhole tools that are lowered / retrieved from a well by unwinding and winding the cable from the drum of a winch. The winch operation is controlled to prevent damage of the cable that may be caused by improper tension of the cable wound on the drum.BACKGROUND OF THE INVENTION

[0003] In oilfield applications, armored electrical conductor cable (wireline) is used to convey various devices into a well with a winch. The cable can be tens of thousands of feet long and would be wound onto the winch in several layers. The winch will wind and store cable under a tension load. Many factors contribute to the tension load on the cable, such as, cable and tool weights, drag force when moving, well fluids and well bore conditions.

[0004] “Cable crush,” sometimes called “drum crush,” is defined as a failure of the outer armor or jacket, or electrical short of the conductor inside the cable preventing it from performing its defined purpose. Cable crush is usually caused by storing cable which is wound under high tension on top of a layer wound at low tension, damaging the cable on the lower tension layer. The ratio of high tension to low tension is referred to as the “crush ratio” and its maximum allowable value is typically defined by the cable manufacturer.

[0005] Currently, only the tension in the cable is monitored and the crush ratio is not computed. As such, the crush ratio can exceed its maximum allowable value and cable crush can occur. When cable cush occurs, the entire cable must often be discarded and replaced by a new cable.

[0006] In view of the foregoing, there is a need for winch systems and methods of using winch systems in which the crush ratio is computed and the tension in the cable is adjusted such that the crush ratio does not exceeds its maximum allowable value.SUMMARY

[0007] A winch system has the ability to control the stored tension to prevent cable crush. The system is capable of determining the position of any segment of the cable in the drum (i.e., a height from the barrel, sometimes expressed as a number of layers, and a distance from a flange, sometimes expressed as a number of rows). The system is capable of determining the tension of any segment of the cable before it is reeled or stored on the drum. The system is capable of determining the crush ratio of any “under” segment of the cable already reeled or stored in an “under” layer that is expected when another “over” segment of the cable is reeled or stored will be reeled or stored in an “over” layer at a particular cable tension. The system is capable of operating the winch so that the cable tension can be adjusted, and the crush ratio remains below a maximum allowable value.

[0008] The invention is susceptible to various modifications and alternative forms, and specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and description are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives available to a person having ordinary skill in the art.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] For a more detailed description of the embodiments of the disclosure, reference will now be made to the accompanying drawings, wherein:

[0010] FIG. 1 illustrates a half cross-section of a cable wound on a drum;

[0011] FIG. 2 illustrates a graph of the tension of a cable wound on a drum as a function of the length of cable wound on the drum;

[0012] FIG. 3 is a display of values of the crush ratio as a heat map on a drum cross-section, and FIG. 3 A is a magnified view of FIG. 3; and

[0013] FIGs. 4-9 are flowcharts of a method of controlling a winch.DETAILED DESCRIPTION

[0014] FIG. 1 schematizes a cable stack cross-section. For simplicity, FIG. 1 is a sketch that may not be drawn to scale and the number revolutions to span the entire length between the flanges may differ from ten / eleven. Indeed, there are typically over 100 revolutions per layer. The cable cross-section is indicated by a circle. The number in the circle correspond to the number or revolutions made to have this section of the cable wound and stored on the drum. For simplicity, the number is an integer in the example of FIG. 1 , but the number may not be an integer. For example, the numbers could be 0.6 revolutions, 1.6 revolutions, etc. By way of example, the dashed box 10 surrounds all the cable sections that correspond to the same distance X from the drum flange (which could be expressed as a number of rows), regardless of the height Y from the barrel (which could be expressed as a number of layers). In this box, revolution 23 sits on top of revolutions 19 and 18. Revolutions 19 and 18 sit on top of revolution 2.

[0015] FIG. 2 schematizes the curve 50 of the tension T in the wound cable as a function of the length L between the origin of the cable at the drum and any short segment of cable wound on the drum. There are several ways to determine the tension T in the cable as it is about to be wound, and there are several ways to determine the length L of the cable that has been wound. For simplicity, FIG. 2 may not be to scale.

[0016] The length intervals 11-16 correspond to the first, second ... sixth layer of cable on the drum. For example, 11 corresponds to the length of cable of revolutions 0 to 10 in FIG. 1, 12 corresponds to the length of cable of revolutions 11 to 20 in FIG. 1, etc.

[0017] By way of example, the greyed boxes 12-22 correspond to the length of wound cable for a short segment of the cable to be in the same cross section as illustrated in FIG. 1, for example, in the box 10 of FIG. 1. For example, the greyed boxes 12 may correspond to the fist layer, third row, and revolution “2” in FIG. 1; the greyed boxes 14 may correspond to the second layer, third row, and revolution “18” in FIG. 1 ; the greyed boxes 16 may correspond to the second layer, second row, and revolution “19” in FIG. 1; and the greyed boxes 18 may correspond to the third layer, third row, and revolution “23” in FIG. 1.

[0018] In this example, the cable is being reeled in. The controls in the winch system prevent the cable tension, in particular in the "under" and "over" layers, from raising above acceptable limits. This is accomplished when winching by at least decreasing the winch speed / decreasing the winch torque if the cable tension T raises above the proper spooling profile (shown as curve 40 in FIG. 2).

[0019] When a prior art system is used, the tension 36 in “over” layer at length 24 may exceed the value 34, which is the product of the tension 32 in “under” layer at length 22 (or length 20) multiplied by the maximum allowable value of the crush ratio.

[0020] Another representation of a section exceeding the crush ratio is shown in FTGs. 3 and 3A. The cable tension at the origin of FIGs. 3 and 3 A is obtained with a prior art system, that is, without adjustment of the cable tension to limit the crush ratio. However, the inventors discovered how to generate the representations such as shown in FIGs. 3 and 3A, and prior art systems do not display the representations shown in FIGs. 3 and 3A. An entire cable is wound on the drum of the winch, during which the cable parameters (e.g., X, Y, T) are continually "mapped" at every position on the winch. The tension was continually monitored, and the crush ratio was calculated and displayed as a heat map on a drum cross-section similar to the section of FIG. 1. FIG. 3 shows the entire crosssection of the drum. FIG. 3A is a magnified view of FIG. 3 centered around revolution 3050. FIG. 3A shows that the crush ratio on the two revolutions 2955 and 2956, which are beneath revolution 3050. Notably, this example illustrates that the tension applied to the “over” layer at revolution 3050 is such that the crush ratio computed with the tension of the “under” layer at revolution 2955 is 1.33, and the crush ratio computed with the tension of the “under” layer at revolution 2956 is 2.2. The maximum the two values is displayed as a heat level at revolution 3050. Thus, the heat map in FIGs. 3 and 3A shows where the tension in the reeled cable in an “over” layer is so high that the crush ratio may be exceeded in the “under” layer below it. The heat map may be used to show where, in the prior art, additional control of the stored tension may be beneficial to prevent cable crush.

[0021] In alternative heat map representations, the heat map can show where the crush ratio may be exceeded in the “under” layer because of the high tension in the reeled cable in an “over” layer above it. This may be achieved by displaying the maximum of the crush ratio of any “under” segment of the cable already reeled or stored in an “under” layer caused when both “over” segments of the cable are reeled or stored in an “over” layer as a heat level at the location corresponding to the “under” segment. The alternative heat map may be used to show where, in the prior art, cable may have been crushed, which can help with cable maintenance. Note that the crush ratio would not be calculated until the “over” layer is reeled in.

[0022] FIG. 4 is a flowchart of a general method of winding or unwinding a cable of a drum that utilizes the system described herein. In this embodiment, the cable tension T is controlled by the torque of the winch drive system.

[0023] The system is configured to control torque to keep proper tension in the cable when reeling the cable out, that is, when the cable is moving in the down-hole direction, and the tools (e.g.,perforating guns) atached to the cable are being pumped or tractored into the well, for example, because the bottom of the wells is typically not vertical and the tools can no longer fall to the bottom. In particular, the system can be configured to maintain the desired tension profile on the drum when the cable is payed out so that when reeling-in starts back, the tension on the lower layers isn't too low, which can cause a cable crush situation.

[0024] The tension comparison and resulting adjustment performed at 100 are used to keep the tension from falling too low when reeling the cable out (i.e., the cable is moving in the down-hole direction). The resulting adjustment would typically be “increase winch torque” and / or “maintain winch torque.” However, there are cases where the system may need to decrease winch torque to keep the tension value from geting too high. The crush ratio comparison and resulting adjustment performed at 110 may be ignored when reeling the cable out.

[0025] Thus, in an example control algorithm usable when reeling the cable out in the down-hole direction, a comparison of the tension to a spooling profile (e.g., similar to curve 40 in FIG. 2 but starting at larger length of cable stored on the drum and finishing at lower lengths on the drum) preferably has priority. That is, if the current tension in the cable measured after the drum is lower than the desired profile value, then the system attempts to increase the tension by increasing torque, in order to maintain the desired tension profile. Conversely, if current tension in the cable measured after the drum is higher than the desired profile value, then the system attempts to reduce the tension by reduced torque, in order to maintain the desired tension profile.

[0026] Also, the system is configured to control torque when reeling the cable in, that is, when the cable is moving in the up-hole direction, to keep proper tension on the drum. If tension is the cable raises too high, a segment of cable with lower tension may end up below the cable being wound on the drum and potentially the crush ratio may be exceeded.

[0027] For example, the tension in the cable wound at lower location(s) on the drum multiplied by the maximum allowable value of the crush ratio usually leads to a lower value of the tension than the proper spooling profile. So, typically, the tension comparison and resulting adjustment performed at 100 may not provide sufficient tension control when reeling the cable in. Thus, the crush ratio comparison and resulting adjustment performed at 110 preferably has priority when reeling the cable in. The comparison of the tension to the lower location(s) on the drum (multiplied by the maximum allowable value of the crush ratio) is used to keep the tension from being too high.When reeling the cable in (i.e., the cable is moving in the up-hole direction), the resulting adjustment would typically be “decrease winch torque” and / or “maintain winch torque.” However, there are cases where the system may need to increase winch torque. Thus, in contrast to prior art system, the controls in the winch system also prevent the tension applied to the "over" layer from exceeding the crush ratio. This is accomplished when winching by recording the tension T and position of the cable (for example X and Y, as defined above) as it is wound onto the winch and limiting the tension in any "over" layer wound on top of an "under" layer based on the tension in the "under" layer at that position.

[0028] Thus, in an example control algorithm usable when reeling the cable in, the current cable tension measured in the cable segment about to be wound on the drum is measured. The tension in any "under" layer, which was previous measured and stored, is retrieved and a crush ratio is computed at 110. Also, the current tension is compared with desired profile value at 100. If the current the tension is lower than the desired profile value and the crush ratio is higher than the cable specifications, then the control system attempts to reduce the tension and decrease the crush ratio by reducing winch torque (which will also result in reduced winch speed). If the current tension is higher than the desired profile value and the crush ratio is higher than the cable specifications, then the control system attempts to reduce the tension by reducing winch torque. If the current tension is lower than desired profile value and the crush ratio is lower than the cable specifications, then the control system may maintain torque winch. If the current tension is higher than the desired profile value and the crush ratio is lower than the cable specifications, then the control system attempts to reduce the tension by reducing the winch torque.

[0029] In the embodiment of FIG. 4, the cable tension T is controlled by the torque of the winch drive system. However, in other embodiments, the cable tension T may alternatively be controlled by the speed of the winch drive system. That is, when reeling out, the cable tension is increased by decreasing the winch speed (and pumping / tractoring the tools faster), and the cable tension is decreased by increasing the winch speed (and pumping / tractoring the tools slower). Conversely, when reeling is, the cable tension is increased by increasing the winch speed , and the cable tension is decreased by decreasing the winch speed (and pumping / tractoring the tools slower).

[0030] Optionally, a powered capstan may also be used for assistance in controlling the cable tension T. For example, a powered capstan can force the cable tension at the desired tension profile.

[0031] In the embodiment of FIG. 4, the current cable tension is used for control. However, other values indicative of the tension, such as values calculated with a Proportional-Integral-Derivative (PID) algorithm, or equivalent can alternatively be used.

[0032] By way of example, a case of successful control of crush ratio when reeling in is illustrated. Referring back to FIG. 2, as the second row of the second layer is about to be wound in the third row of the second layer at length 14 corresponding to revolution “18” (or the third row of the second layer at length 16 corresponding to revolution “19”), the system can retrieve the value of the cable tension 26 measured in the third row of the first layer at length 12 corresponding to revolution “2”. The system can compute a maximum tension 28 by multiplying the value of the cable tension 26 by the maximum allowable value of the crush ratio to obtain a maximum tension value 28 at the length 14 (or length 16). The system may then adjust the cable tension 30 at the length 14 (or length 16) below the value 30.

[0033] FIG. 5 is a flowchart of a method of winding or unwinding a cable of a drum that utilizes the control system described herein.

[0034] In this embodiment, the position of a specific segment of cable on the winch can be calculated.

[0035] This embodiment utilizes a measuring head, which provides a measurement of the cable speed, and a measurement of cable tension (via a load pin on a reel of the measuring head)

[0036] This embodiment may utilize an electric winch having a resolver that provides a measurement of revolutions and / or rotation speed. Alternatively, a winch utilizing a hydraulic drive may be used, and an encoder placed on the motor drive or drum may be provided instead of the electric motor resolver.

[0037] The layer height Y may be calculated using the cable speed and rotation speed. A discontinuity of layer height Y indicates a stack height change, which is used to calculate the distance X from the flange.

[0038] FIG. 6 is a flowchart of a method of winding or unwinding a cable of a drum that utilizes the system described herein.

[0039] In this embodiment, the cable tension T is determined from the winch torque and cable stack height Y.

[0040] This embodiment utilizes a measuring head, which provides a measurement of the cable speed. However, the cable tension may not be provided by the measuring head. Instead, this embodiment may utilize an electric winch having a current sensor that provides a measurement of winch torque, and the cable tension is calculated as the quotient of the winch torque by the layer height Y. Alternatively, a winch utilizing a hydraulic drive may be used, and torque can be derived from a pressure transducer signal. Torque is a function of hydraulic pressure and motor displacement.

[0041] The distance X and the layer height Y may again be calculated using the cable speed and rotation speed, either provided with a resolver (when using an electric motor) or an encoder (when using a hydraulic motor), as was explained in FIG. 5.

[0042] FIG. 7 is a flowchart of a method of winding or unwinding a cable of a drum that utilizes the system described herein.

[0043] In this embodiment, the distance X and the layer height Y are determined by sensor (optical or laser sensors, acoustic sensors, or contact sensors with potentiometers).

[0044] FIG. 8 is a flowchart of a method of winding or unwinding a cable of a drum that utilizes the system described herein.

[0045] In this embodiment, the cable tension T is determined from a separate load cell.

[0046] FIG. 9 is a flowchart of a method of winding or unwinding a cable of a drum that utilizes the system described herein.

[0047] In this embodiment, a powered capstan is used for assistance in controlling the cable tension T. The capstan measures a well tension. The capstan is operated such that the cable tension at the winch T is within a range of ratio of the well tension.

[0048] In any of the embodiments, the cable parameters (e.g., X Y, T) are continually "mapped" at every position on the winch. The tension may be continually monitored, and the crush ratio may be calculated, stored, and / or displayed. The crush ratio may be used to schedule maintenance or replacement of the cable. An example of such a display is illustrated in FIGs. 3 and 3A (note that the operation of the winch was not adjusted in the example of FIGs. 3 and 3 A).

[0049] Furthermore, in any of the embodiments, a cable data interface is capable of providing a cable tension, and a position of any segment of cable that is wound, such as shown at step 120 of FIG. 4.

[0050] In any of the embodiments, the operation of the winch may be adjusted to control the cable tension of the "over" layer as it is being applied to remain below a value by a winch drive programmed at step 110 shown in FIG. 4. The value is calculated by multiplying the tension of the cable on the "under" layer by the maximum crush ratio, for example by using the computer 130 of FIG. 4.

[0051] In any of the embodiments, the computer is optionally programmed to display of values of the crush ratio as a heat map on a drum cross-section, for example as shown in FIG. 3.

[0052] In any embodiments, the winch drive is capable of adjusting the tension in the segment of cable about to be wound to a value that is based on a predetermined spooling profile at step 100 shown in FIG. 4. The tension in the segment of cable about to be wound may be maintained below the predetermined spooling profile when reeling in. The tension in the segment of cable about to be wound may be maintained above the predetermined spooling profile when reeling out. The predetermined spooling profile used when reeling may or may not differ from the predetermined spooling profile used when reeling out. The winch drive optionally includes a powered capstan.

Claims

What is claimed is:

1. A winch system, comprising: a cable data interface capable of providing a cable tension, and a position of any segment of cable that is wound; a computer capable of retrieving a cable tension of one or more segments previously wound that will be directly adjacent to a segment of cable about to be wound; and a winch drive programed for adjusting the tension in the segment of cable about to be wound to a value that is so that a crush ratio remains below a predetermined allowable value.

2. The winch system of claim 1 wherein the winch drive is further programmed for adjusting the tension in the segment of cable about to be wound to a value that is above a predetermined spooling profde when reeling out.

3. The winch system of claim 1 wherein the winch drive is further programmed for adjusting the tension in the segment of cable about to be wound to a value that is below a predetermined spooling profde when reeling in.

4. The winch system of claims 2 or 3 wherein the winch drive comprises a powered capstan.

5. The winch system of claim 1 wherein the computer is programmed to display of values of the crush ratio as a heat map on a drum cross-section.

6. The winch system of claim 1 wherein the computer is capable of determining the position of any segment of the cable in the drum.

7. The winch system of claim 6 wherein the position of any segment of the cable in the drum includes a height from a barrel of a drum, and a distance from a flange of the drum.

8. The winch system of claim 7 wherein the height from the barrel is expressed as a number of layers.

9. The winch system of claim 7 wherein the distance from the flange is expressed as a number of rows.

10. A method of controlling tension of a cable stored on a winch, comprising: providing a cable tension, and a position of any segment of cable that is wound; retrieving a cable tension of one or more segments previously wound that will be directly adjacent to a segment of cable about to be wound; and adjusting the tension in the segment of cable about to be wound to a value that is so that a crush ratio remains below a maximum allowable value.

11. The method of claim 10 further comprising adjusting the tension in the segment of cable about to be wound to a value that is above a predetermined spooling profde when reeling out.

12. The method of claim 10 further comprising adjusting the tension in the segment of cable about to be wound to a value that is below a predetermined spooling profile when reeling in.

13. The method of claims 11 or 12 wherein the winch drive comprises a powered capstan.

14. The method of claim 10 further comprising displaying values of the crush ratio as a heat map on a drum cross-section.

15. The method of claim 10 further comprising determining the position of any segment of the cable in the drum.

16. The method claim 15 wherein the position of any segment of the cable in the drum includes a height from a barrel of a drum, and a distance from a flange of the drum.

17. The method of claim 16 wherein the height from the barrel is expressed as a number of layers.

18. The method of claim 16 wherein the distance from the flange is expressed as a number of rows.

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