Patent Application
20090063054
The present invention generally pertains to equipment used for repairing wells that have already been drilled. More specifically the present invention pertains to an analysis of rig loads and rig load data to determine and monitor tubing and/or rod removal overload conditions on a well service rig.
After a well has been drilled, it must be completed before it can produce gas or oil. Once completed, a variety of events may occur to the formation causing the well and its equipment to require a “work-over.” For purposes of this application, “work-over” and “service” operations are used in their very broadest sense to refer to any and all activities performed on or for a well to repair or rehabilitate the well, and also includes activities to shut in or cap the well. Generally, work-over operations include such things as replacing worn or damaged parts (e.g., a pump, sucker rods, tubing, and packer glands), applying secondary or tertiary recovery techniques, such as chemical or hot oil treatments, cementing the wellbore, and logging the wellbore, to name just a few. Service operations are usually performed by or involve a mobile work-over or well service rig (collectively hereinafter “service rig” or “rig”) that is adapted to, among other things, pull the well tubing or rods and also to run the tubing or rods back in to the well. Typically, these mobile service rigs are motor vehicle-based and have an extendible, jack-up derrick complete with draw works and block.
During rod or tubing removal, a rig operator typically lifts a stand of tubing (or rods) which is then held in place by slips (or elevators for rods) while the stand is separated from the remaining portion of the tubing or rod string in the well. Once the stand of tubing has been separated from that which is still in the well, the stand of tubing can be placed on a tubing board. During the initial lifting operation, the weight or load on the hook can fluctuate greatly based on the weight of the tubing string in the well, the conditions within the well, the condition of the tubing string, and the amount of acceleration of the tubing string. In general the tubing string acts similarly to a rubber band. As the operator begins to accelerate the block upward and pull the tubing string out of the well. the tubing string initially becomes elongated for a short interval before the entire tubing string begins to move upward through the well. The same elongation can occur when a portion of the tubing string encounters a part of the well with increased friction or gets snagged or stuck within a portion of the well. If the operator does not recognize the problem quickly enough, the amount of load on the hook (“hookload”) can increase very quickly to a level that is above the safe operating level of the rig. While alarms can be employed, if the operator cannot act quickly enough, the rig may be damaged and workers around the well could be injured.
In addition, as the stands of tubing (or rods) are being pulled out of the well, the total amount of weight on the string is reduced and the length of the string is reduced. When there are only a few stands of tubing left in the well, pulling the tubing out at a typical rate of speed, for example, six feet per second, can become more dangerous because if the tubing snags or drags in the well there is less overall elasticity within the remaining length of tubing, and therefore, less time to react to the increase in hookload. This can cause dangerous conditions around the wellhead.
Furthermore, while a stand of tubing (or rods) is being decoupled from the remaining string in the well, the operator brings his engine RPM up to drive the tongs that are used to unscrew the tubing from one another. When the previously pulled stand of tubing is fully disengaged from the remaining tubing in the well, the operator engages the clutch for the hoist and lifts the stand of tubing about another foot or two and places it onto the tubing board. The lifting of the stand of tubing that small distance prior to placement on the tubing board can cause a small spike in the rig load recorded at the rig load sensors. Much of this spike is caused by the acceleration of the block by the operator. Unfortunately, at times, the operator is in a hurry or is not cautious enough and can begin lifting the stand of tubing before the stand has been fully unscrewed from the tubing that remains in the well. When this occurs the rig load will suddenly and violently increase. The rig load can continue to increase until the stand of tubing breaks free of the final threads of the tubing at the wellhead. When the stand breaks free anyone in the vicinity of the wellhead is in danger of serious injury.
What is needed is a method and apparatus for evaluating the rig load or hookload of a service rig when removing tubing or rods from a well and disengaging the clutch for the hoist when the rig load reaches a level indicative of a problem with the tubing in the well, such as a snag or hang up. Furthermore, what is needed is a method and apparatus for evaluating the rig load or hookload of a tubing or rod string being removed from a well and limiting the speed of the block and hoist when only a small amount of tubing or rods remains in the well. In addition, what is needed is a method and apparatus for determining when a stand of tubing or rods is being decoupled from tubing or rods remaining in the well during a pull operation and preventing or limiting the ability for the block and hoist to lift the stand if the stand is not fully disengaged from the remaining tubing or rods in the well.
The present invention is directed to solving these as well as other similar issues in the well service area.
The present invention is directed to controlling the operation of a well service rig based on rig load data. By removing the need for or limiting the capabilities of the operator during situations of increased load on the well service rig the ability to prevent damage to the service rig and injury to the workers around the well head can be improved. Furthermore, by limiting the speed of the well service rig during periods where only a small amount of tubing or rods remains to be pulled out of a wellbore, the opportunity for a dangerous situation caused by the tubing or rod hanging or getting caught up in the wellbore is reduced based on the fact that reaction time is increased at the slower speeds.
For one aspect of the present invention, a method for determining the average load during the pulling of a stand of rods or tubing can be achieved by monitoring the load data of a well service rig. The load data can be received during the removal process from sensors on the well service rig that transmit inputs to a computer or monitor on the rig. The computer can calculate the average load during the pull of a stand of tubing or rods based on the load data received from sensors. The load data can include the hookload or the load of the rig. The upper load limit can then be determined based on the computation of the average load. The upper load limit can be a fixed amount above the average load for each pull of a stand of tubing or rods or a percentage of the hookload or rig load. The upper load limit can then be set for the next pull of a stand of pipe from the well. The pipe can include, but is not limited to, pipe, well casing, rods, tubing, or other tubulars.
For another aspect of the present invention, a method for determining when to reduce or limit block and/or hoist speed during a pulling operation can be achieved based on an evaluation of hook load data. Load data can be received from sensors on the well service rig related to load calculations taken during the removal of a pipe string from a well. The hookload or rig load can be calculated based on the load data. An evaluation of the hookload or rig load can be conducted to determine if the load has fallen to or below a certain level. That level can be indicative that the weight of the remaining pipe string in the well is much less than when the pull operation first began. If the load is below a certain level, the speed of the block or the hoist can be limited to an speed that is substantially slower than the normal operation of the block and hoist during a standard pulling operation. The reduced speed can increase reaction time in case the pipe string becomes caught in the well.
For still another aspect of the present invention, a method for preventing a well service rig from pulling a stand of pipe away from a pipe string while the stand of pipe is still engaged with the threads of the pipe string can be achieved based on an evaluation of rig load or hookload data. The system can receive information indicating that the rig is disengaging a stand of pipe from a pipe string, such as through the use of tongs. Load data, such as rig load or hookload data can be received when the stand of pipe is being disengaged from the pipe string. An evaluation of the load data can be conducted to determine if the load data has increased above a certain level that is indicative of a stand of pipe being pulled up before the de-threading process has occurred from the pipe string. If the load level has increased to or above a certain level, the clutch for the drive system that is raising the stand of pipe can be disengaged automatically or the throttle can be reduced to prohibit over pulling.
For a more complete understanding of the exemplary embodiments of the present invention and the advantages thereof, reference is now made to the following description in conjunction with the accompanying drawings in which:
Exemplary embodiments of the invention will now be described in detail with reference to the included figures. The exemplary embodiments are described in reference to how they might be implemented. In the interest of clarity, not all features of an actual implementation are described in this specification. Those of ordinary skill in the art will appreciate that in the development of an actual embodiment, several implementation-specific decisions must be made to achieve the inventors' specific goals, such as compliance with system-related and business-related constraints which can vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having benefit of this disclosure. Further aspects and advantages of the various figures of the invention will become apparent from consideration of the following description and review of the figures.
Referring to
The engine 26 selectively couples to the wheels 24 and the hoist 36 by way of the transmissions 34 and 32, respectively. The engine 26 also drives the hydraulic pump 28 via the line 29 and the air compressor 30 via the line 31. The compressor 30 powers a pneumatic slip (Not Shown), and pump powers a set of hydraulic tongs (Not Shown). The pump 28 also powers the cylinders 42 and 44 which respectively extend and pivot the derrick 40 to selectively place the derrick 40 in a working position, as shown in
Individual pipe segments (of string 62) and sucker rods are screwed to themselves using hydraulic tongs. The term “hydraulic tongs” used herein and below refer to any hydraulic tool that can screw together two pipes or sucker rods. An example would include those provided by B. J. Hughes company of Houston, Tex. In operation, the pump 28 drives a hydraulic motor (Not Shown) forward and reverse by way of a valve. Conceptually, the motor drives the pinions which turn a wrench element relative to a clamp. The element and clamp engage flats on the mating couplings of a sucker rod or inner pipe string 62 of one conceived embodiment of the invention. However, it is well within the scope of the invention to have rotational jaws or grippers that clamp on to a round pipe (i.e., no flats) similar in concept to a conventional pipe wrench, but with hydraulic clamping. The rotational direction of the motor determines assembly or disassembly of the couplings.
While not explicitly shown in the figures, when installing the tubing segments 62, the pneumatic slip is used to hold the tubing 62 while the next segment of tubing 62 is screwed on using tongs. A compressor 30 provides pressurized air through a valve to rapidly clamp and release the slip. A tank helps maintain a constant air pressure. Pressure switch provides monitor 48 (
Referring back to
In the embodiment of
Returning to
A telephone accessible circuit 124, referred to as a “POCKET LOGGER” by Pace Scientific, Inc. of Charlotte, N.C., includes four input channels 126, 128, 130 and 132; a memory 96 and a clock 134. The circuit 124 periodically samples inputs 126, 128, 130 and 132 at a user selectable sampling rate; digitizes the readings; stores the digitized values; and stores the time of day that the inputs were sampled. It should be appreciated by those skilled in the art that with the appropriate circuit, any number of inputs can be sampled and the data could be transmitted instantaneously upon receipt.
A supervisor at a computer 100 remote from the work site at which the service rig 20 is operating accesses the data stored in the circuit 124 by way of a PC-based modem 98 and a cellular phone 136 or other known methods for data transfer. The phone 136 reads the data stored in the circuit 124 via the lines 138 (RJ11 telephone industry standard) and transmits the data to the modem 98 by way of antennas 140 and 142. In an alternative embodiment the data is transmitted by way of a cable modem or WiFi system (Not Shown). In one exemplary embodiment of the present invention, the phone 136 includes a CELLULAR CONNECTION™ provided by Motorola Incorporated of Schaumburg, Ill. (a model S1936C for Series II cellular transceivers and a model S1688E for older cellular transceivers).
Some details worth noting about the monitor 48 is that its access by way of a modem makes the monitor 48 relatively inaccessible to the crew at the job site itself. However the system can be easily modified to allow the crew the capability to edit or amend the data being transferred. The amplifiers 122, 144, 146 and 148 condition their input signals to provide corresponding inputs 126, 128, 130 and 132 having an appropriate power and amplitude range. Sufficient power is needed for RC circuits 150 which briefly (e.g., 2-10 seconds) sustain the amplitude of inputs 126, 128, 130 and 132 even after the outputs from transducers 46, 102 and 80 and the output of the generator 118 drop off. This ensures the capturing of brief spikes without having to sample and store an excessive amount of data. A DC power supply 152 provides a clean and precise excitation voltage to the transducers 46, 102 and 80; and also supplies the circuit 124 with an appropriate voltage by way of a voltage divider 154. A pressure switch 90 enables the power supply 152 by way of the relay 156, whose contacts 158 are closed by the coil 160 being energized by the battery 162.
Processes of exemplary embodiments of the present invention will now be discussed with reference to
Turning now to
In step 810, an inquiry is conducted to determine if the rig load weight is above the baseline weight or load level. The baseline weight is generally at a level that is marginally above the weight of the rig itself. In one exemplary embodiment, the baseline weight is approximately 40,000 pounds. However, those of skill in the art will recognize that this amount may be easily changed based on other factors, such as rig size, well conditions, etc. In an alternative embodiment, there may not be a need for an evaluation of the baseline weight, as any rig load limit weight will generally be above the baseline weight. If the weight is not above the baseline weight, the “NO” branch is followed back to step 805. On the other hand, if the rig load weight is above the baseline weight, the “YES” branch is followed to step 815.
In step 815, an inquiry is conducted to determine if the blocks 38 are moving in the direction to remove tubing 62 from the wellbore 58. In one exemplary embodiment, the direction of the blocks 38 can be analyzed by positioning an encoder (Not Shown) at the hoist 36 or at another position along the line coupled to the block 38. If the block 38 is not moving in the direction for removing the tubing 62, the “NO” branch is followed to step 805. Otherwise, the “YES” branch is followed to step 820.
In step 820, an inquiry is conducted to determine if the slips at the wellhead 68 are open. The slips are used when pulling tubing 62 out of the well 58. When the tubing 62 is being pulled out and it is time to unscrew one stand of tubing 62 from another, the tubing 62 is set on the slips, which suspend the remaining tubing 62 at the wellhead 186 and down in the wellbore 58. In one exemplary embodiment, the slips are engaged into position through the use of pneumatic pressure. IN this exemplary embodiment, the position of the slips can be determined through the use of a pneumatic switch that sense if opening or closing air pressure is being applied to the slips. In an alternative embodiment, the position of the slips can be evaluated using a slip sensor to evaluate and open/closed position. In this embodiment, the slip sensor can include a pressure-type input/output switch. Those of ordinary skill in the art will recognize that other methods of determine the position of the slips can also be employed, including photoeyes, proximity sensors and other positional indicators. If the slips are not open, the “NO” branch is followed to step 805. If the slips are open, the “YES” branch is followed to step 825.
In step 825, the rig load weight data is recorded and displayed at the computer 705.
Returning to
In step 840, an inquiry is conducted to determine if the rig load level is above the rig load limit. The current rig load level may be determined at the sensor 92 or by monitoring the data curve 910 on the chart 905. If the rig load level is not above the rig load limit, the “NO” branch is followed back to step 825 to continue recording rig load data at the computer 705. However, if the rig load level is above the rig load limit, the “YES” branch is followed to step 845, where the computer 705 sends a signal to apply the brake and disengage the clutch of the hoist 36 and reduce the engine throttle or any combination thereof, thereby stopping any additional pulling of the tubing 62 out of the wellbore 58. In step 850, the computer 705 sends a signal to activate an alarm and records the overload event for subsequent analysis and training of the rig operator. The alarm may be audible, visual or both. Audible alarms include, but are not limited to, sirens, horns and the like. Visual alarms may include, but are not limited to, flashing lights, a light turning on, or a display of a message at the computer 705. The process then continues to the END step.
A determination is made as to when the completion time for pulling a stand of tubing 62 has occurred in step 1010. In one exemplary embodiment, the time of completion occurs after the start time when the slips are closed. The time to pull a stand of tubing 62 generally takes approximately twelve seconds; however, shorter and longer periods are within the scope of this invention.
During the first interval 1115, the curve 1105 is reflective of Hooke's law, or the spring action of the tubing 62. If the operator pulls off the slips too fast or has a running start before the elevators engage the tubing collar, the peak at point 1105 will increase above the actual weight due to momentum. Additionally, not allowing the hoist chain sprocket and right angle drive (Not Shown) to come to a stop prior to engaging the clutch for the hoist 36 will cause the peak at 1105 to increase as well. In one exemplary embodiment, the first time interval will be between one and five seconds, however adjustments to the interval length may be made based on the length of tubing 62 remaining on the string, the amount of acceleration, and the condition of the wellbore 58. The second interval 1120 is the most reflective of the true rig load. The slope of the rig load data curve 1105 during the second interval 1120 is normally positive because the block speed is increasing, however, the slope can be zero if the block speed is constant. The third interval 1125 is the interval with the fastest ascending tubing 62 speed. The data 1105 during the third interval can be reflective of swabbing the hole. The increase in the apparent weight during the third interval 1125 is typically due to drag and speed of the tubing 62.
Returning to
The average rig load is reduced by the weight of the rig 20 in step 1210. In one exemplary embodiment, the weight of the rig can be determined prior to pulling the tubing 62 or manually input by the rig operator. In another exemplary embodiment, the rig weight can be determined by receiving the minimum rig load data point 915 of
In step 1220, the load safety factor is added to the average rig load for the most recent pull of a stand of tubing 62. The sum of the load safety factor and the average rig load are set as the rig load limit for the pull of the next stand of tubing 62. The process continues for each subsequent stand of tubing 62 until all of the tubing 62 has been removed from the wellbore 58. The process continues from step 1225 to step 840 of
The average rig load is determined in step 830 and is described in greater detail in
If the average rig load has not reached a predetermined level, then the “NO” branch is followed to step 1425, where additional stands of tubing 62 are removed with the operator having the complete range of speed control available. The process then returns to step 830 to determine the average rig load for the most current tubing pull. If the average rig load has reached the predetermined level, then the “YES” branch is followed to step 1430, where the computer 705 transmits a signal to limit block speed while pulling the remaining stands of tubing 62. The signal generally acts as a governor for the drive of the hoist 36. In one exemplary embodiment, the standard speed for removal of tubing 62 is approximately six feet per second and the limited block speed has a maximum of anywhere between one-half and four feet per second after the predetermined rig load is reached. In step 1435, the slippage in the transmission 32 can also be increased for the hoist 36. In one exemplary embodiment, the slippage in the transmission 32 can be increased by opening a solenoid valve (Not Shown) on the first transmission 32 case thereby relieving hydraulic pressure in the transmission lockup system. The reduction in hydraulic pressure induces slippage into the first transmission 32 and thereby offers another level of safety in case the rig 20 pulls tubing 62 that unexpectedly gets hung up on something in the wellbore 58. Additionally, the air pressure applied to the hoist clutch bladder can be reduced, thereby inducing slippage in the hoist clutch. In one exemplary embodiment, the clutch bladder generally is provided with an air pressure in excess of one hundred pounds per square inch when a hoist 36 is operating normally with a load. This air pressure can be reduced to induce the slippage described above and provide another level of safety in case the tubing 62 is hung up in the wellbore 58. The process then continues to the END step. While the present method has been described generally in terms of the rig load, those of ordinary skill in the art will recognize that, with minor modifications as discussed herein, the hookload could be substituted for the rig load in most instances.
In step 1510, an inquiry is conducted to determine if the rig load weight is above the baseline level. The baseline weight is generally at a level that is marginally above the weight of the rig 20 itself. In one exemplary embodiment, the baseline weight is approximately 40,000 pounds. However, those of skill in the art will recognize that this amount may be easily changed based on other factors, as described above. In an alternative embodiment, there may not be a need for an evaluation of the baseline weight, as any rig load limit weight will generally be above the baseline weight. If the weight is not above the baseline weight, the “NO” branch is followed back to step 1505. On the other hand, if the rig load weight is above the baseline weight, the “YES” branch is followed to step 1515.
In step 1520, an inquiry is conducted to determine if the blocks 38 are moving in the direction to remove tubing 62 from the wellbore 58. In one exemplary embodiment, the direction of the blocks 38 can be analyzed by positioning an encoder at the hoist 36 or at another position along the line coupled to the block 38. If the block 38 is not moving in the direction for removing the tubing 62, the “NO” branch is followed to step 1505. Otherwise, the “YES” branch is followed to step 1520. In step 1520, an inquiry is conducted to determine if the slips (Not Shown) at the wellhead 186 are closed during a tubing pull or if the elevator (Not Shown) is in use during a rod pull. If the slips are open or the elevator is not in use for the rod pull, the “NO” branch is followed to step 1505. Otherwise, the “YES” branch is followed to step 1525.
In step 1525, the computer 705 evaluates the rig load data. The computer 705 can evaluate the raw data from the sensor 92, data that has been “cleansed,” or it can review the data points on the chart 905. In step 1530, an inquiry is conducted to determine if the rig load is above a predetermined level. In one exemplary embodiment, the predetermined level is a hookload of between two and ten thousand pounds or a rig load having a predetermined level of between two and ten thousand pounds plus the weight or estimated weight of the rig 20. As described above, the weight of the rig 20 can be manually input at the computer 705 or determined based on an evaluation of the lower limits of the rig load data 915 on the rig load data chart 905.
If the rig load is not above the predetermined level, the “NO” branch is followed to step 1525 to continue evaluation of the rig load data. On the other hand, if the rig load is above the predetermined level, the “YES” branch is followed to step 1535, where the computer 705 transmits a signal to apply the brake and disengage the clutch for the hoist 36 and block 38, thereby stopping any additional pulling of the tubing 62 out of the wellbore 58. An alarm is initiated and an overload event is recorded in step 1540 for subsequent analysis and training of the rig operator. The alarm may be audible, visual or both. Audible alarms include, but are not limited to, sirens, horns and the like. Visual alarms may include, but are not limited to, flashing lights, a light turning on, or a display of a message at the computer 705. The process continues from step 1540 to the END step.
Although the invention is described with reference to preferred embodiments, it should be appreciated by those skilled in the art that various modifications are well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the claims that follow. From the foregoing, it will be appreciated that an embodiment of the present invention overcomes the limitations of the prior art. Those skilled in the art will appreciate that the present invention is not limited to any specifically discussed application and that the embodiments described herein are illustrative and not restrictive. From the description of the exemplary embodiments, equivalents of the elements shown therein will suggest themselves to those or ordinary skill in the art, and ways of constructing other embodiments of the present invention will suggest themselves to practitioners of the art. Therefore, the scope of the present invention is to be limited only by any claims that follow.
