Pumpjack production control
Contents
1. 5 372 482 A 12 1994 London et al 5 441 389 A 8 1995 Wolcott et al 5 634 522 A 6 1997 Hershberger 5 829 530 A 11 1998 Nolen 6 176 682 Bl 1 2001 Mills 6 599 095 BI 7 2003 Takada et al 6 631 762 B2 10 2003 Collette 7 083 391 B2 8 2006 Sievert et al oo 417 42 2010 0038078 Al 2 2010 Fink 2010 0101774 A1 4 2010 Ocondietal 166 66 2011 0103974 Al 5 2011 Lamascus et al 417 45 OTHER PUBLICATIONS Lea et al What s New in Artificial Lift article from World Oil Online vol 227 No 4 Apr 2006 downloaded from http www worldoil com April 2006 Whats new in artificial lift html gt 13 pages Telemecanique ATV 71 Beam Pump Controller User Manual 34 pages Nov 8 2007 cited by examiner Primary Examiner Yong Suk Philip Ro 74 Attorney Agent or Firm Banner amp Witcoff Ltd 57 ABSTRACT A method software and apparatus for controlling a pump configured to pump liquid out of a well Such control may involve determining whether a production rate of gas from the well is increasing decreasing or steady and whether to switch the pump between an OFF state and an ON state Whether the pump is switched may depend upon whether the production rate of the gas is determined to be increasing decreasing or steady 18 Claims 6 Drawing Sheets U S Patent Fig 1 Dec 16 2014 SAN WS aN 101 a 106 107 108 0 112 rr2. 12 United States Patent Krauss US008910710B2 US 8 910 710 B2 Dec 16 2014 10 Patent No 45 Date of Patent 54 75 73 21 22 65 51 52 58 56 PUMPJACK PRODUCTION CONTROL Inventor Alan Frederick Krauss Knightdale NC US Assignee Schneider Electric USA Inc Palatine IL US Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 594 days Appl No 13 114 508 Filed May 24 2011 Prior Publication Data US 2012 0298375 A1 Nov 29 2012 Int Cl E21B 43 12 E21B 47 00 US Cl CPG maawa Kitaan E21B 47 0008 2013 01 USPC 166 250 15 166 369 166 53 417 20 Field of Classification Search CPG uus E21B 43 00 E21B 43 12 E21B 44 00 E21B 47 0008 Sese 166 369 53 250 15 417 53 12 20 417 36 44 1 See application file for complete search history 2006 01 2012 01 References Cited U S PATENT DOCUMENTS 3 269 320 A 3 851 995 A 4 318 674 A 4 390 321 A 4 541 274 A 8 1966 12 1974 3 1982 6 1983 9 1985 Fredriksson et al Mills Godbey et al Langlois et al 417 15 Purcupile 73 152 61 Neh 417 12 7 4 859 151 A 8 1989 Reed 4 972 705 A 11 1990 Fryer et al 4 973 226 A 11 1990 McKee ses 417 18 5 044 888 A 9 1991 Hester II 5 064 349 A 11 1991 Turner et al 417 53 5 284 422 A 2 1994 Turner et al
3. CuSum lt 2 LowThresh LowThresh Confirmed down slope set SubMin Steady or up slope set AddMin go to go to step 803 810 step 802 813 US 8 910 710 B2 1 PUMPJACK PRODUCTION CONTROL BACKGROUND Pumpjack systems often include a pump off controller that switches a pump between an ON state and an OFF state based on how long the pump has been in a particular state These pump off controllers may also switch the pump to the OFF state when a pump off condition is detected such as an under filled pump stroke In some systems the well is intended for producing gas and the pump is used to remove largely unde sirable liquid from the well to make room for the gas to enter the well for extraction In these types of wells the pump may run regardless of whether liquid extraction at a given time is beneficial to gas production SUMMARY Various aspects are described herein that may provide for example systems methods and software for controlling a pump such as a pump that is configured to pump liquid out of a gas producing well The state of the pump may be con trolled based on feedback information regarding the rate of a product being produced by the well For example where gas e g natural gas is being produced by the well the pump may be switched between the ON state and the OFF state depending upon whether the production rate is determined to be increasing decreasing or steady The switching of the pump from
4. component of the pumpjack such as the prime mover 105 Torque may be measured in a variety of ways such as using an ammeter on current fed to a prime mover 105 if prime mover 105 is an electric motor When the measured torque is graphed against the displacement of a reciprocating component of the pumpjack system such as the reciprocating polished rod 107 such a graph results also in a curve that is known to provide information that may be used to estimate various conditions experienced by the pumpjack system 100 such as pump fill and or whether a pump off condition exists Any of the functions and steps described herein may be performed and or controlled by controller 130 An example block diagram of controller 130 is shown in FIG 4 Controller 130 may be orotherwise include a computer and may include hardware that is hard wired to perform specific functions and or hardware that may execute software to perform spe cific functions The software if any may be stored on a non transitory computer readable medium 402 in the form of computer readable instructions Controller 130 may read those computer readable instructions and in response per form various steps as defined by those computer readable instructions Thus for example any of the steps and func tionality described in connection with FIGS 5 8 may be implemented for example by reading and executing such computer readable instructions for performing such steps and implementing s
5. decrease increase increase increasing decreasing OFF steady increasing increase decreasing decrease The example operation according to Table 1 is arranged such that the system is biased to maintain production while not expending energy by operating the pump unless it is deemed necessary In comparison with a simple ON OFF time pump off controller utilizing the above operating prin ciple may result in a relative increase in production and possibly a relative decrease in energy expenditure or at least a relatively small increase in energy expenditure compared with the increase in production Variations on the operating characteristics of Table 1 may be used while still achieving increased production in an efficient manner Studying the example of Table 1 more closely it will be seen that the pump is turned to or maintained in an ON state only ifthe ON state is apparently benefitting production That is if gas production is increasing while the pump is in the ON state the system will maintain the ON state in the hope that this will continue to cause production to increase at least for some period of time And if production is steady e g rela tively constant such as within an upper and lower threshold or having a very small slope then the pump may remain ON because it can be assumed that the status quo may be helping US 8 910 710 B2 7 to maintain production However if production is steady for an extended
6. production rates of the gas is decreasing 3 The method of claim 2 wherein the changing the state of the pump comprises changing the state of the pump from an OFF state to an ON state and the changing the pump off time comprises decreasing the pump off time 4 The method of claim 2 wherein the changing the state of the pump comprises changing the state of the pump from an ON state to an OFF state and the changing the pump off time comprises increasing the pump off time 5 The method of claim 1 wherein the state of the pump is OFF and wherein the method comprises maintaining the pump in the OFF state responsive to the determining that the second one of the plurality of production rates of the gas is increasing and responsive to determining that the pump has remained in the OFF state for less than a predetermined amount of time 6 The method of claim 1 further comprising measuring the plurality of production rates of the gas 7 A method of controlling a pump configured to pump liquid out of a well comprising determining by a computer whether a production rate of gas is increasing decreasing or steady determining by the computer what state the pump should be in according to the following 1 while the pump is in an ON state and the production rate ofthe gas is determined to be steady maintain the pump in the ON state and increase a pump off time of the pump 2 while the pump is in the ON state and the production ra
7. the OFF state to the ON state may also be based on a parallel decision based on whether a pump off condition has been reached Moreover the pump off time may be adjusted based on the determined production rate This type of pump control may allow for a system that is biased toward running the pump only when deemed neces sary in accordance with the determined production rate This may potentially allow for the system to be more efficient by not running the pump when it would likely not provide any benefit This may be in contrast to simpler pump off control lers that control the pump based merely on timers and or on detected traditional pump off conditions Moreover the pro posed pump control may be used in conjunction with tradi tional time based control and or traditional pump off condi tion based control In some cases the additional control functionality may even be retrofitted to traditional pump off controllers According to some aspects as described herein example methods software and apparatuses are described for control ling a pump configured to pump liquid out of a well Such control may involve for example determining whether a production rate of gas from the well is increasing decreasing or steady determining whether the state of the pump should be changed depending upon whether the production rate of the gas is determined to be increasing decreasing or steady and responsive to determining to that the pump should be
8. the pump In the latter case commands from pump off controller 501 and produc tion controller 502 to the pump may be arbitrated in the event of conflicting commands For example a command to turn or maintain the pump OFF by either of the controllers 501 502 may take precedence over a command to turn or maintain the pump ON Or a command to turn or maintain the pump ON by eitherofthe controllers 501 502 may take precedence over a command to turn or maintain the pump OFF At a high level pump off controller 501 and production controller 502 together e g as controller 130 may operate for example as shown below in Table 1 This example assume that the production product is gas e g natural gas and that downhole pump 117 is used mostly for removing waste prod ucts e g water and other liquids from annulus 115 to make room for the desirable natural gas to enter annulus 115 and rise upward for collection While the waste products may themselves include one or more desirable products such as oil for the present example it will be assumed that production refers only to the gas that is produced for collection TABLE 1 OFF Time Adjustment Pump Control Pump Status Production Action ON steady stay ON unless increase production is consistent for threshold time otherwise turn pump OFF stay ON turn pump OFF stay OFF unless maximum OFF time is reached stay OFF unless maximum OFF time is reached turn pump ON
9. 27 Gg 7 113 AN 2 N14 UA UA 2 2 eed A15 f f Sheet 1 of 6 US 8 910 710 B2 a 100 ATA RREY nn nent lt NNI basa en OR EO ath lt etn Ne HA paka on Soe HA Katana IC ODIO ODD RNA 7 M RES EEES Za REIHE LESE ese A amp PS OR HOMME SK M II one tons SS nn Metz SR TR ANTE ANH NOH REZ EN LE AAA x1 1 BAK ne EZ PRE PRE babaen abo NARI AM 2 NAHE notant ner SOD nd nie RE BN D NEEN EEN EEE none SD rte SW GN ESSEN RR E pO e ese IEI PEEN EE oo AA re ER Nba bab MG YENG I HONORE HEN PI NNN HES SRK EEEN OLE GAS NAATASANG ad M ne SD E UA SDE KGG AN PI Ls US 8 910 710 B2 Sheet 2 of 6 Dec 16 2014 U S Patent Extracted FJ S E my Extracted fluid gas fluid gas o zl SE MS Fig 3 Fig 2 U S Patent Computer Readable Medium 402 Pump Off Controller Dec 501 Production Controller 502 16 2014 Sheet 3 of 6 Processor 401 Pump Driver 404 Control Pump off measurements Production status Control lI AU mMMM M settings and commands Fig 5 US 8 910 710 B2 User Input Output Interface 403 Pump Jack 100 U S Patent Dec 16 2014 Sheet 4 of 6 US 8 910 710 B2 Raw production data Low Pass Filter 601 ProdData Sample1 Sample2 ud lama ProdFast Sample3 4 ProdSlow Slow Low P
10. as expired 17 The method of claim 14 wherein the switching the pump to the ON state comprises switching the pump to the ON state before the pump off time has expired 18 The method of claim 13 further comprising responsive to determining that a third one of the plurality of directions of change is neither the increasing direction nor the decreasing direction increasing the pump off time of the pump koko ox
11. ass Filter 603 Fast Low Pass Filter 602 Derivative Calculator 604 ProdFast Delta Calculator 606 Delta CuSum register DeltaSum DeltaSum 605 register 607 U S Patent Dec 16 2014 Sheet 5 of 6 Adjust PumpOffTime based on AddMin and SubMin 703 Turn Pump OFF Sample2 time ended 705 DerivSum 0 704 Clear AddMin and SubMin 706 Sample Filter ProdData to Generate ProdFast and ProdSlow 707 Generate Deriv and update CuSum 108 Evaluate CuSum 109 CuSum s UpperThresh and CuSum gt MidThresh US 8 910 710 B2 Turn Pump ON CuSum 0 clear AddMin and SubMin 701 CuSum s MidThresh Suspected up CuSum slope set SubMin A go to step 702 UpperThresh 711 Confirmed up slope set CuSum UpperThresh set SubMin go to step 702 else go to step 702 110 712 Steady if determined five times to be steady then go to step 703 and set AddMin CuSum gt LowThresh CuSum lt LowThresh Confirmed down slope set AddMin go to step 703 713 U S Patent Dec 16 2014 Sheet 6 of 6 US 8 910 710 B2 Adjust PumpOffTime based on AddMin and es Submin 803 umpOffTime Ended Turn Pump ON CuSum 0 804 time ended 805 yes Clear AddMin and SubMin 806 Sample Filter ProdData to Generate ProdFast and ProdSlow 807 Generate Deriv and update CuSum 808 Evaluate CuSum 809 CuSum
12. ausing travelling valve 120 to move downward This produces a relatively higher pressure between travelling valve 120 and standing valve 119 causing it to open and travel downward through the liquid that previously passed through standing valve 119 on the up stroke The higher pressure also causes standing valve 119 to close thereby forcing the pre viously drawn liquid to remain in place while travelling valve 120 moves downward through that liquid By alternating up and down strokes downhole pump 117 may therefore draw liquids that have fallen to the bottom of annulus 115 up and out of the well As previously explained while liquids fall to the bottom of annulus 115 gases tend to rise upward in annulus 115 Thus depending upon the level of the liquid at the bottom of annu lus 115 relative to the intake of downhole pump 117 gases are ideally not pumped through downhole pump 117 Instead gases may be collected and or disposed of from the well through an exit tube 111 disposed at or near the top of annulus 115 A measurement device 112 may be coupled to exit tube 111 for measuring the volume and or rate of the gas traveling through exit tube 111 Depending upon the desired product to be produced by the well either the gas or the liquid or both the gas and the liquid may be considered a production product Likewise depend ing upon what is desired the gas or the liquid may be con sidered a waste product For example depending upon wher
13. e the well is located the well may produce an excellent supply of oil whereas the gas also produced may be an unwanted byproduct or it may be a useful product In this case down hole pump 117 may be used to pump the desirable oil along with other liquids such as water Or where gas is considered the main product to be produced by the well such as where the well is located in a region that contains little to no liquid petroleum product to be extracted then the waste liquid may primarily include water with various contaminants In this case the downhole pump 117 may be used to draw up the waste liquid simply to prevent annulus 115 from becoming full of the liquid and thereby preventing the desirable gas product from entering annulus 115 Pumpjack system 100 may operate continuously or on a periodic basis under the control of controller 130 For example controller 130 may cause prime mover 105 to con tinuously run so as to cause pumpjack system 100 to perform a series of stroke cycles each stroke cycle including a pair of an upstroke and a downstroke Such continuous operation may carry on until a pump off condition occurs A pump off condition may occur where for instance it is determined that there is insufficient liquid in annulus 115 to be pumped by downhole pump 117 Continuing to pump under such a con dition may result in conditions that can cause damage to the pumpjack system 100 A pump off condition may also occur due to a
14. e g by five minutes If this shortening of PumpOffTime causes PumpOff Time to be less than or equal to zero then this may cause the process to immediately jump to step 804 such that the pump is imme diately turned ON Otherwise the process continues in its current state If the immediate reduction in PumpOffTime causes the process to jump to step 804 thus turning on the pump at least a predetermined number of times in a row e g three times in US 8 910 710 B2 11 a row then the conclusion may be that the process is not helping and that possibly ProdSlow is not keeping up with current baseline values In this case ProdSlow may be set equal to ProdFast and the process of FIGS 7 and 8 continued In the above discussion with regard to FIGS 7 and 8 the process may alternatively be implemented in which one or more of the less than conditions may be replaced with less than or equal to conditions and or vice versa and or one or more of the greater than conditions may be replaced with greater than or equal to conditions and or vice versa In addition while particular examples methods of determining whether the production rate is increasing decreasing or steady have been described such a determination may be performed in any of a number of ways and may even involve a direct evaluation of the raw production signal without the above described pre processing of FIG 6 or using a different type of pre processing Moreover there a
15. e is accordingly a level or range of levels at which the liquid level in annulus 115 should be maintained to provide a desired system efficiency In an ideal world one might directly measure the liquid level and control pumpjack system 100 based on the direct measurement While such an arrangement has been proposed this is not always practical because downhole pump 117 may be located extremely deep into the earth and subject to intense environmental conditions making the sensor and mainte nance thereof expensive Moreover such an arrangement would involve finding a way for the remote underground sensor to communicate with the above ground control sys tem thereby raising an additional challenge Another way to control a pumpjack is to measure the mechanical force experienced by certain system components over the duration of an upstroke and or a downstroke Force may be measured in a variety of ways such as using a con ventional downhole card inside the well and or a dynamom eter coupled to an above ground portion of the pumpjack system When the measured force is graphed against the displacement of the travelling valve of the downhole pump or against the displacement of any other reciprocating or rotating portion of the pumpjack such a graph results in a curve that is known to provide useful information about the conditions experienced by the downhole pump Another way to control a pumpjack is to measure the torque experienced by a
16. ed up slope Ifit is determined that CuSum is less than LowThresh then it may be concluded that there is a confirmed down slope in production In this case at step 810 the SubMin flag may be set and the process may move to step 803 such that the pump is turned back ON at step 804 This is because the assumption is that the OFF state of the pump is harming production If it is determined that CuSum is greater than or equal to LowThresh then it may be concluded that production is either steady or has a confirmed up slope In this case at step 813 the AddMin flag may be set and the process may move to step 802 The pump remains OFF for now because the assumption is that leaving the pump OFF is not harming production and that expending additional energy to run the pump may not be expected to result in a sufficient increase in production Thus while the pump is OFF if production is deemed to be decreasing then the process may cause the pump to turn ON Otherwise the pump remains OFF This is consistent with the example of Table 1 In addition to the above discussed process of FIG 8 a parallel process may run in which DeltaSum and or Delta may be evaluated periodically say every five Sample2 peri ods e g every five minutes If it is determined that Delta is less than LowThresh and or DeltaSum is less than LowThresh then PumpOfflime may be immediately reduced shortened by a greater amount than would be caused by setting SubMin
17. esirable for various reasons to pre process or condition the production data For instance the raw production data may be highly variable over short periods of time which may cause the control system to act in an unstable manner FIG 6 is a block diagram of an example production data conditioner that may generate indicators based on the raw production data The indicators rather than the raw produc tion data may be used to determine whether production is steady increasing or decreasing In the example of FIG 6 it is assumed that the raw production data is an analog signal as opposed to digital data However the raw production data may be digital data The raw production data may be pro duced and or sampled on a periodic basis The raw production data may be filtered by a low pass filter 601 to generate a data signal referred to herein as ProdData Low pass filter 601 produces ProdData at a sampling period referred to herein as Samplel which may have a sampling period appropriate for the sensor and overall system design of e g less than one second e g twenty milliseconds or some number of seconds Again all time periods discussed herein are merely examples Next ProdData may be filtered by two parallel low pass filters 602 and 603 Low pass filter 602 is referred to herein as a high cutoff low pass filter and low pass filter 603 is referred to herein as a low cutoff low pass filter The high cutoff and low c
18. haracteristics different from the first low pass filter to obtain a third signal determining by a computer using both the second signal and the third signal a plurality of directions of change of the production rate of gas 20 25 14 responsive to determining that a first one of the plurality of directions of change is an increasing direction while the pump is inan ON state decreasing a pump off time of the pump and responsive to determining that a second one of the plurality of directions of change is a decreasing direction while the pump is in the ON state switching the pump to an OFF state and increasing the pump off time of the pump 14 The method of claim 13 further comprising responsive to determining that the first one of the plurality of directions of change is the increasing direction while the pump is in the OFF state increasing the pump off time of the pump and responsive to determining that the second one of the plu rality of directions of change is the decreasing direction while the pump is in the OFF state switching the pump to the ON state and decreasing the pump off time of the pump 15 The method of claim 14 further comprising switching the pump from the OFF state to the ON state responsive to determining that the pump off time of the pump has expired 16 The method of claim 14 wherein the increasing the pump off time of the pump comprises increasing the pump off time after the pump off time h
19. his is the fifth time in a row that step 712 has been executed i e that it has been concluded that production is steady This implies that production is neither improving nor declining while the pump is running If that is the case then AddMin may be set indicating a desire to increase the amount of PumpOffTime such as by one minute and the process may instead move to step 703 thereby also causing the pump to change to the OFF state at step 704 The pump is turned OFF because the assumption is that running the pump is not necessarily help ing production and running the pump at this point may not result in a sufficient increase in production to justify running pump Thus continuing to run the pump may be considered a waste of energy and may incur unnecessary wear and tear on the pump apparatus If it is determined that CuSum is less than or equal to LowThresh then it may be concluded that there is a con firmed down slope in production In this case at step 713 the AddMin flag may be set and the process may move to step 703 thereby also causing the pump to change to the OFF state at step 704 Again the assumption here is that running the 30 35 40 45 50 55 60 65 10 pump is not helping production so the pump is turned off to avoid unnecessarily expending energy Thus while the pump is ON if production is deemed to be decreasing or is deemed to be steady over a sufficient period of time then the process
20. k system 100 and or controller 130 may be turned on or otherwise started at which time the process of FIG 7 may begin at step 701 At step 701 the pump may be turned on such as by controlling prime mover 105 to the ON state and CuSum may be cleared by setting it to zero In addition one or more flags indicating whether a pump off time should be increased or decreased may be cleared In the example embodiment of FIG 7 a flag called AddMin when set may indicate that the pump offtime should be increased such as by one minute or another period oftime and another flag called SubMin when set may indi cate that the pump off time should be decreased such as by one minute or another period of time The pump off time would be the amount of time that the pump would remain in an OFF state as monitored by a timer The value ofthe pump off time is referred to herein as PumpOffTime In alternative embodiments AddMin and SubMin may be embodied as a single flag where one value representing increasing the pump offtime and another value represents decreasing the pump off time There may also be a defined pump on time monitored by a timer and represented in this case by the value PumpOnTime At step 702 it may be determined whether PumpOnTime has ended or expired and if so then at step 703 PumpOffTime is increased or decreased e g by one minute depending upon whether AddMin or SubMin is set At step 704 the pump is turned OFF and CuSum i
21. may cause the pump to turn OFF Otherwise the pump remains ON This is consistent with the example of Table 1 Once the pump is turned OFF at step 704 the process may move to step 802 of FIG 8 At step 802 it may be determined whether PumpOffTime has ended or expired and if so then at step 803 PumpOffTime is increased or decreased e g by one minute depending upon whether AddMin or SubMin is set At step 804 the pump is turned ON and CuSum is again cleared by setting it to zero The process would then move back to step 702 of FIG 7 which has already been discussed If at step 802 it is determined that PumpOffTime has not yet ended then the process may move to step 805 in which it is determined whether the current Sample2 period has ended Ifthe current Sample2 period has not ended then the process cycles back to step 802 Once it is determined at step 805 that Sample2 has ended the process moves to step 806 and clears AddMin and Sub Min Also at step 807 a new value of each of ProdFast and ProdSlow is generated and at step 808 Deriv is generated and CuSum is updated with the most recent value of Deriv by adding the most recent value of Deriv to the previous value of CuSum Next at step 809 the value of CuSum may be evaluated and compared with one or more thresholds The result of this evaluation may determine whether production is considered to be in one of two states 1 confirmed down slope and 2 steady or confirm
22. ng 116 includes a series of perforations 121 that expose annulus 115 to an oil or gas bearing region 123 of ground 122 Liquids such as oil and water and gases such as hydrocarbon gases e g methane ethane etc enter perfo rations 121 into annulus 115 through a combination of out side pressure and a vacuum produced by downhole pump 117 Liquids fall to the bottom of annulus 115 due to gravity and gases being lighter than the liquids rise upward in annulus 115 Downhole pump 117 may include a standing valve 119 a travelling valve 120 coupled to sucker rod 113 and a hollow region referred to as a pump barrel 118 disposed between the standing and travelling valves 119 120 Downhole pump 117 typically operates as follows Referring to FIG 2 as sucker rod 113 moves in an up stroke liquid above travelling valve 120 causes travelling valve 120 to close and so the upward movement creating a vacuum between travelling valve 120 and standing valve 119 This causes standing valve 119 to open allowing liquid that has accumulated at the bottom of annulus 115 to be drawn up through standing valve 119 Meanwhile if tubing 114 is sufficiently already full of previ ously pumped liquids then the liquid at the top of the liquid US 8 910 710 B2 3 stack in tubing 114 is pushed upward an outward through a junction 109 and an exit tube 110 for collection and or dis posal On the down stroke FIG 3 sucker rod 113 moves down ward also c
23. period of time then the pump may be turned OFF Likewise if the pump is in the OFF state then according to Table 1 the system would be reluctant to turn the pump ON unless the OFF state is associated with decreasing production Thus there is a bias in this example to maintain the pump in an OFF state unless it is deemed likely that the ON state would benefit production Another potential consequence of operating the system in accordance with the above operating principle e g Table 1 is that the level of the liquid at the bottom of annulus 115 may be naturally maintained at a level resulting in high production and possibly even optimal production for the operating con ditions This may mean that the level of the liquid may be generally located somewhere between the intake of downhole pump 117 and the bottom of perforations 121 For instance depending upon the particular operating conditions this oper ating principle may be expected to potentially result in the liquid level being maintained very close to the bottom of perforations 121 This may be in contrast to many systems using a simple conventional pump off controller in which the liquid level is typically maintained very close to the intake of downhole pump 117 Production data for use with Table 1 may be collected by e g measurement device 112 While the raw production data may be used directly to determine whether production is steady increasing or decreasing it may be d
24. put interface 403 may be used to indicate pump ON or OFF status time remaining until pump ON or OFF pump fill and or any other desired infor mation Controller 130 may further include a pump driver 404 for controlling whether prime mover 105 will operate to cause pumping action For example pump driver 404 may cause prime mover 105 to turn on and off as desired In some embodiments controller 130 via pump driver 404 may cause prime mover 105 to turn on or off or otherwise adjust its operation such as changing the speed ofthe pump chang ing the stroke speed As will be discussed such pump control operations may be performed in response to a pump off con dition and or another factor such as the expiration of a timer and or based on gas production rate FIG 5 is another block diagram of an example controller including a pump off controller 501 and a production control ler 502 Pump off controller 501 and production controller 502 may be physically separate units or they may be inte grated as a single controller with the functionality of both controllers 501 502 For example controller 130 may imple ment one or both of pump off controller 501 and production controller 502 In some embodiments pump off controller 501 and production controller 502 may utilize the same physical processor 401 but may be implemented using dif ferent portions of the above mentioned computer executable instructions In other embodiments pump off con
25. re many other ways of implementing the actions set forth in example Table 1 In addition while the above examples have assumed that the pump may change between a single ON state and a single OFF state in further embodiments the pump may be con trolled by controller 130 to have multiple speeds e g mul tiple ON states In such embodiments where the process calls for changing the state of the pump from an ON state to an OFF state the process may instead changing the state of the pump by reducing the speed of the pump And where the process calls for changing the state of the pump from an OFF state to an ON state and where in these embodiments the pump had been previously slowed rather than actually turned OFF the process may instead change the state of the pump by increasing the speed of the pump Moreover any or all of the functions and steps described herein with regard to FIGS 6 8 may be performed in whole or in part by controller 130 Any of the blocks and steps of FIG 6 8 may be implemented as software modules e g in the form of computer readable instructions and or as hardware such as circuitry of controller 130 Moreover some or all of the functions and steps of FIGS 6 8 may be performed by production controller 502 of controller 130 and or by pump off controller 501 of controller 130 Thus various example systems methods and software have been described that may be used to control the produc tion efficiency of a p
26. s Next a derivative calculator 604 may be used to calculate the derivative of ProdFast and to output the calculated deriva tive as a data signal referred to herein as Deriv In alternative embodiments derivative calculator 604 may not take a true derivative but instead may calculate another type of delta value ProdSlow in the meantime may be processed by a delta calculator 606 to calculate a delta which may be calcu lated for example as follows Delta 100x ProdFast Prod Slow ProdSlow The resulting data signal Delta may be con sidered to generally represent a short term change from the average baseline value represented by ProdSlow Next Deriv is accumulated over time and the accumulated value CuSum is stored in a register referred to herein as CuSum register 605 Likewise Delta is also accumulated over time and the accumulated value DeltaSum is stored in a register referred to herein as DeltaSum register 607 As will be discussed below CuSum and or DeltaSum may be used as indicators from which decisions may be made as to whether production is currently steady increasing or decreasing FIGS 7 and 8 are a flow chart showing example steps that may be performed to control a pump and may operate based on the values of CuSum and or DeltaSum The process of FIG 7 may be performed while the pump is in the ON state and the process of FIG 8 may be performed while the pump is in the OFF state Referring first to FIG 7 pumpjac
27. s LowThresh The threshold values may be set to any values as desired In one example UpperThresh may be equal to 5 0 MidThresh may be equal to 2 5 and LowThresh may be equal to 10 0 However these values are merely examples and should not be considered as limiting to the present invention Ifitis determined that CuSum is greater than UpperThresh then it may be concluded that there is a confirmed up slope in production In this case at step 710 CuSum may be set equal to UpperThresh the SubMin flag may be set indicating a desire to reduce the amount of PumpOffTime such as by one minute and the process may move to step 702 The pump remains ON for now because the assumption is that the current pump state ON is benefitting production If it is determined that CuSum is greater than MidThresh and CuSum is less than or equal to UpperThresh then it may be concluded that there is a suspected up slope in production Inthis case at step 711 the SubMin flag may be set indicat ing a desire to reduce the amount of PumpOff Time such as by one minute and the process may move to step 702 The pump remains ON for the time being because the assumption is that the current pump state ON is benefitting production If it is determined that CuSum is greater than LowThresh and CuSum is less than or equal to MidThresh then it may be concluded that production is currently steady In this case at step 712 the process may move to step 702 unless t
28. s cleared again by setting it to zero The process would then move to FIG 8 which will be dis cussed later below If at step 702 it is determined that PumpOnTime has not yet ended then the process may move to step 705 in which it is determined whether the current Sample2 period has ended US 8 910 710 B2 9 As discussed previously Sample2 refers to the time period at which the data series of ProdFast and ProdSlow are gener ated Sample2 may be for example one minute If the current Sample2 period has not ended then the process cycles back to step 702 Once it is determined at step 705 that Sample2 has ended the process moves to step 706 and clears AddMin and Sub Min Also at step 707 a new value of each of ProdFast and ProdSlow is generated and at step 708 Deriv is generated and CuSum is updated with the most recent value of Deriv by adding the most recent value of Deriv to the previous value of CuSum Next at step 709 the value of CuSum may be evaluated and compared with one or more thresholds The result of this evaluation may determine whether production is considered to be in one of four states confirmed up slope confirmed increasing suspected up slope suspected increasing steady zone and confirmed down slope confirmed decreas ing The thresholds may include an upper threshold referred to herein as UpperThresh a middle threshold referred to herein as MidThresh and a lower threshold referred to herein a
29. s sectional view of an example pumpjack system 100 Such a system 100 may include an above ground structure that includes a walking beam 101 onto which a horse head 102 is mounted Walking beam 101 may reciprocate so asto move horse head 102 upward up stroke and downward down stroke on a periodic basis To move walking beam 101 a controller 130 may command a prime mover 105 such as a motor to send rotational power to a transmission 104 which may include a gear reducer that causes a crank arm and counter weight 103 to rotate at a reduced rotational speed and increased torque relative to prime mover 105 Because counter weight 103 is offset from its rotational axis this causes an arm attached to walking beam 101 to move walking beam 101 in a reciprocating manner As horse head 102 moves up and down this causes a string 106 also known as a birdie that is usually made of a steel cable to also move up and down In turn this movement causes a polished rod 107 to move up and down through a lubricated stuffing box 108 which in turn causes a sucker rod 113 typically made of a series of longitudinally intercon nected steel rods attached to the lower end of polished rod 107 to also move up and down Sucker rod 113 extends downward into a well in ground 122 through tubing 114 to a downhole pump 117 A hollow annular region referred to herein as annulus 115 encircles tubing 114 and is disposed between tubing 114 and an outer casing 116 Casi
30. switched changing the state of the pump The techniques described herein may be utilized in con nection with various types of pump systems such as but not limited to a pumpjack system for pumping water and liquid oil and for producing natural gas from a well These and other aspects of the disclosure will be apparent upon consideration of the following detailed description BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present disclosure and the potential advantages of various aspects described herein may be acquired by referring to the following descrip 20 25 30 35 40 45 50 55 60 65 2 tion inconsideration ofthe accompanying drawings in which like reference numbers indicate like features and wherein FIG 1 is a cross sectional view of an example pumpjack system FIG 2 is a cross sectional view of an example downhole pump in operation during an up stroke FIG 3 is a cross sectional view of an example downhole pump in operation during a down stroke FIG 4 is a block diagram of an example controller that may be used to perform various functions FIG 5 is another block diagram of an example controller including a pump off controller and a production controller FIG 6 is a block diagram of an example production data conditioner and FIGS 7 and 8 are a flow chart showing example steps that may be performed to control a pump DETAILED DESCRIPTION FIG 1 is a cros
31. te ofthe gas is determined to be increasing maintain the pump in the ON state and decrease the pump off time of the pump 3 while the pump is in the ON state and the production rate of the gas is determined to be decreasing switch the pump to an OFF state and increase the pump off time of the pump 4 while the pump is in the OFF state and the production rate of the gas is determined to be steady maintain the pump in the OFF state and increase the pump off time of the pump 5 while the pump is in the OFF state and the production rate of the gas is determined to be increasing maintain the pump in the ON state and increase the pump off time of the pump and 6 while the pump is in the OFF state and the production rate of the gas is determined to be decreasing switch the pump to the ON state and decrease the pump off time of the pump and responsive to determining to that the state of the pump should change between the ON state and the OFF state changing the state of the pump between the ON state and the OFF state 8 A method of controlling a pump configured to pump liquid out of a well comprising measuring a production rate of gas from the well determining by a computer whether the production rate of the gas is increasing decreasing or steady increasing a pump off time of the pump responsive to determining that the production rate of the gas is steady US 8 910 710 B2 13 determining after said increasing
32. timeout For instance controller 130 may be config ured so as to continuously cause pumpjack system 100 to pump for X amount of time or until another pump off condi tion is met whichever occurs first In other examples pump jack system 100 may be controlled to perform only a single stroke cycle at a time with a delay between cycles In still further examples pumpjack system 100 may be controlled to adjust the speed of a stroke The stroke speed continuous duration stroke frequency and or delay between stroke cycles may be set so as to ideally minimize energy expended minimize pumpjack system wear and maximize production All of these can depend upon a variety of factors For un 0 20 25 40 45 4 example if liquid is drawn through perforations 121 into annulus 115 very quickly and easily then pumpjack system 100 may need to operate downhole pump 117 more often or on a more continuous basis Otherwise the liquid level in annulus 115 may rise too high reducing the efficiency ofthe system especially where gas is the desired product since there will be less room in annulus 115 for the gas On the other hand if liquid is not drawn quickly through perforations 121 then the liquid level may be too low in annulus 115 unless pumping is reduced As discussed above this may allow gas to be pumped up through downhole pump 117 potentially causing production loss gas lock and or equip ment damage As can be seen ther
33. troller 501 and production controller 502 may utilize different physical processors and or other hardware and may communicate with each other in a wired and or wireless manner In either case if production controller 501 is already in operation in the field rather than replace the entire controller 301 production controller 502 may be retrofitted with production controller 502 such as via a software upgrade to controller 103 and or as a hardware addition to controller 103 Pump off controller 501 may be configured to control the ON and OFF states of pump jack system 100 in response to one or more measurements relevant to a pump off condition and or responsive to the expiration of a timer For instance pump off controller 501 may be configured to turn the pump ON until either a pump off condition is detected or a timeout occurs whichever occurs first Examples of measurements that may be relevant to a pump off condition include as discussed previously torque and or force measurements 5 jai 5 20 25 30 35 40 45 50 55 60 65 6 Production controller 502 may be configured to modify the operation of the pump based on actual production measure ments This may be done in various ways For example production controller 502 may provide an input to pump off controller 501 which may cause pump off controller 501 to modify how it controls the pump Alternatively production controller 502 may directly control
34. uch functionality and or by any hardware subsystem e g a processor 401 from which controller 130 US 8 910 710 B2 5 is composed Processor 401 may be implemented as for example a central processing unit CPU an application specific integrated circuit ASIC a field programmable gate array FPGA and or a programmable logic controller PLC Additionally or alternatively any of the above men tioned functions may be implemented by the hardware of controller 130 with or without the execution of software Computer readable medium 402 may include not only a single physical non transitory storage medium or single type of such medium but also a combination of one or more such storage media and or types of such media Examples of com puter readable medium 402 include but are not limited to one or more memory chips hard drives optical discs such as CDs or DVDs magnetic discs and magnetic tape drives Computer readable medium 402 may be physically part of or otherwise accessible by controller 130 and may store com puter readable instructions e g software and or computer readable data 1 e information that may or may not be execut able Controller 130 may also include a user input output inter face 403 for receiving input from a user e g via a keyboard mouse and or remote control and or for providing output to the user e g via display device an audio speaker and or a printer For example user input out
35. umpjack or other pumping system using as a feedback mechanism information about the actual cur rent and or past production While embodiments of the present invention have been illustrated and described it is not intended that these embodiments illustrate and describe all possible forms of the present invention Rather the words used in the specification are words of description rather than limitation and it is understood that various changes may be made without departing from the spirit and scope of the present disclosure The invention claimed is 1 A method of controlling a pump configured to pump liquid out of a well comprising determining by a computer a plurality of production rates of gas from the well calculating at least one derivative of data representing the plurality of production rates of the gas using the at least one derivative to determine whether the plurality of production rates ofthe gas are decreasing or increasing changing a state of the pump responsive to determining to that a first one of the plurality of production rates of the gas is decreasing and 20 25 30 35 40 45 50 55 60 65 12 maintaining the state of the pump responsive to determin ing that a second one of the plurality of production rates of the gas is increasing 2 The method of claim 1 further comprising changing a pump offtime ofthe pump responsive to the determining that the first one of the plurality of
36. utoff designations are relative and refer to how much of the higher frequency components are sup pressed by the filters the low cutoff low pass filter 603 suppresses more higher frequency components has a nar rower passband than the high cutoff low pass filter 602 Each of these filters 602 603 produce a data signal at a sampling rate of Sample2 which may be equal to or longer than Samplel For example where the period of Samplel is twenty milliseconds the period of Sample2 may be one or more orders of magnitude longer than Samplel such as one minute or longer The output data signal of high cutoff low pass filter 602 is referred to herein as ProdFast and the output data signal of low cutoff low pass filter 603 is referred to herein as ProdSlow each of which may include a Sample2 20 25 30 35 40 45 50 55 60 65 8 period series of data ProdSlow may represent a filtered ver sion ofthe raw production data that relatively speaking does not readily respond to variations in the raw production data Thus ProdSlow may be considered to generally represent a short term average baseline value of the production data ProdFast on the other hand may represent a filtered version ofthe raw production data but one that responds more readily to higher frequency variations in the raw production data while still suppressing much higher frequency variations that may represent noise or anomalie
37. whether the production rate of the gas remains steady for at least a predeter mined period of time and responsive to determining that the production rate of the gas has remained steady for at least the predetermined period of time changing a state of the pump 9 The method of claim 8 further comprising responsive to said determining that the production rate of the gas is steady and prior to said changing the state of the pump maintaining a state of the pump to be a same state as when the production rate of the gas was mea sured during said measuring 10 The method of claim 8 wherein the changing the state of the pump comprises hanging the state of the pump from an ON state to an OFF state 11 The method of claim 8 wherein said determining the production rate of the gas comprises filtering data represent ing measured gas production through a low pass filter 12 The method of claim 8 wherein said determining whether the production rate of the gas is increasing decreas ing or steady comprises comparing the production rate of the gas to an upper threshold value and a lower threshold value 13 A method of controlling a pump configured to pump liquid out of a well comprising receiving a first signal representing a measured production rate of gas from the well and filtering the first signal using a first low pass filter to obtain a second signal filtering the first signal using a second low pass filter hav ing filter c
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