Abstract:
The present invention relates to a downhole hydraulic pump monitoring system and more specifically relates to a system which detects and/or anticipates pump malfunctions by processing readings taken by a pressure transmitter on the operating pressure and the stroke rate of the downhole hydraulic pump where decisions are reached regarding positive pump operation or inefficient pump malfunction based upon comparisons between the instantaneous pressure readings of the pressure transmitter and a time-averaged operating pressure of the power fluid taken over a multitude of pump strokes.

Description:
BACKGROUND OF THE INVENTION 
     When the internal pressure in an oil well formation is not great enough to move oil to the surface of the well, a pump is required to move or produce the oil from the well. A downhole pump is one type of pump commonly used to produce the oil and derives its name from the fact that it is actually placed down within the oil well as opposed to a pump having the pumping rod located on the surface above the well. Certain conditions dictate the use of downhole pumps as opposed to surface pumps. 
     Problems occur when a downhole pump malfunctions or breaks down. Malfunctions or breakdowns result in decreased production, temporary halts in production, inaccuracies in oil volume measurements, maintenance expenses, and expenses required to oversee, repair and check such pumps. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a downhole hydraulic pump monitoring system and more specifically relates to a system which detects and/or anticipates pump malfunctions by processing readings taken by a pressure transmitter on the operating pressure and the stroke rate of the downhole hydraulic pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of the system incorporating the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the downhole hydraulic pump monitoring system 8 is shown. The system 8 is used in an oil well 10 which is producing oil. A downhole hydraulic pump 12 is placed down within the oil well 10. An inflowing supply line 14 conveys a power fluid, typically oil, to a supply line 15 which runs into the well 10 to power the hydraulic pump 12. Oil or fluid produced from the well is typically pumped up the sides of the well 10 along with the power fluid supplied to power the hydraulic pump 12. This oil flows through an outflowing line 19. 
     A power fluid flow meter 16 is mounted in the inflowing line 14. Flow meter 16 detects the amount of power fluid flowing through lines 14 and 15 to power hydraulic pump 12. A pressure transmitter 18 is mounted either on the inflowing supply line 14 or the downhole supply line 15 at a position where pressure fluctuations can be accurately detected (preferably as close to the pump 12 as is practical). The pressure transmitter 18 is preferably a 4-20 Ma pressure transmitter. A production flow meter 20 is typically mounted in the outflowing line 19. Flow meter 20 measures the amount of outflowing power fluid combined with the fluid produced from the well 10. 
     A pump monitor 22 including a data processor can be used to monitor the inflowing flow meter 16, the production flow meter 20, and the pressure transmitter 18 via transmitter lines 24, 26, and 28 respectively. A user interface 30 is connected to the pump monitor 22. The user interface 30 may comprise a hand held programmer or keypad 32 and a display or terminal 34. The user interface could also comprise a computer. The user interface 30 allows data retrieval and programming. 
     The pump monitoring system 8 uses a combination of hardware and software to perform several functions: the pressure of the power fluid in inflowing line 14 is measured and converted to PSI and a supply operating pressure reading is recorded; the stroke rate of the downhole pump 12 is detected and calculated; malfunctions of the downhole hydraulic pump are determined or anticipated; the flow rate of power fluid through inflowing line 14 is determined; the flow rate of power fluid through outflowing line 19 is determined; to enable the input of higher and lower limits or setpoints into the system 8; to output several types of data from the system 8; and to automate control of the system 8. 
     The hydraulic pump 12 accepts varying volumes of power fluid when the pump 12 is operating, reciprocating or stroking. Variations cause pressure fluctuations to be reflected up the downhole line 15. Therefore each stroke of the hydraulic pump 12 will create a pressure fluctuation. The pressure transmitter 18 detects an instantaneous power fluid supply pressure which will vary due in part to these pressure fluctuations. The pressure of the supply power fluid at the wellhead or surface is typically between 1,000 and 3,000 PSI and the pressure fluctuations detected by the pressure transmitter 18 typically range between 50 and 200 PSI. 
     In order to calculate the stroke rate of the hydraulic pump 12 the instantaneous supply pressure is first detected by pressure transmitter 18. The pump monitor 22 then calculates an average or operating supply pressure by taking the average of a series of instantaneous pressure readings (e.g. separate instantaneous pressure readings of 1275, 1290, 1290, 1275 would result in an operating pressure of 1282.5). When the instantaneous pressure rises above the average pressure, a stroke is detected and recorded. The total number of strokes are counted and used to calculate the strokes per minute or the time between successive strokes. 
     The pump monitor 22 is the device which calculates the number of pressure fluctuations per minute in order to measure the rate at which the pump is stroking. This data can be outputed at user interface 30. The pressure fluctuation readings or calculations are used to determine and/or anticipate downhole hydraulic pump malfunctions. The user interface 30 can also include a relay for turning the oil supply on or off. A suitable control system including pump monitor 22 and user interface 30 is available from Ryo-Tech of Monahans, Tex. 
     The power fluid flow meter 16 is used to count and record the volume (BBLS) of fluid flowing in. The production flow meter 20 is used to count and record the volume of fluid flowing out. The volume of fluid flowing out is compared to the volume of fluid flowing in in order to determine and record the volume of fluid produced. 
     User interface 30 can be used to input high and low limits or set points for pressure, stroke rate, flow rate through inflowing line 14, and flow rate through outflow line 19. If a high or a low limit is violated a set number of times (as set through the user interface 30) a predetermined action can be triggered. The pump monitor 22 may be programmed to take the following actions: no action, step and restart after downtime, stop and wait for a manual reset, and/or to trigger an alarm. A malfunction of the downhole pump 12 can be anticipated or detected by deviations beyond the high and low limits set for stroke rate and operating pressure. Each well has its own characteristics and therefore, the user should program the upper and lower limits based upon the individual characteristics of each will. Nevertheless, the violation of a lower limit suggests a rupture or break between the supply line and the pressure transmitter and the pump, that the supply pressure has failed or there is a transducer failure; the violation of an upper limit suggests that the pump is stuck or there is a broken transducer; and the violation of the stroking rate limit implies a malfunction in the pumping system except for any effects due to the possible occurence of well-producing fluid or formation fluid induced-flow variations. 
     Data can be outputed from the user interface 30 at user selected intervals. When the selected intervals occur data may be outputed on status, time, operating pressure, stroke rate, flow rate through inflowing line 14 and flow rate through outflowing line 19. The keypad 32 allows the user to change various parameters used by the system 8. The system can also be started and stopped from the keypad 32. The display 34 will preferably display various parameters entered via keypad 32 and any output data. 
     For communications the System can be equipped with a connector such a 9 pin RS 232 style connector to access the system from a portable computer or by radio from a central computer (not shown). The invention can be used to monitor several wells at the same time and to store data for retrieval at a later time. 
     A flow chart for the downhole hydraulic pump monitoring system 8 follows: 
     
         ______________________________________FLOW CHART______________________________________POWER ONCLEAR MEMORY AND SET UP PROCESSORBEGIN MAIN LOOPSEND OR RECEIVE DATA VIA THE SERIAL I/OHAS 10 MILLISECONDS PASSEDNO             YES          SET FLAG B10MSA          INCREMENT THE TIMER          USED FOR MEASURING          STROKES/MIN.          READ A/D CONVERTER          CHECK FOR KEYS PRESSED          CHECK DISPLAY          IF 1 S HAS PASSED          INCREMENT THE RUNTIME          CHECK THE TIME          OF DAY CLOCKIF B10MSA IS SET GO TO THE NEXT TASKTASK RETURNCLEAR B10MSARETURN TO MAIN LOOPTASK 1CHECK THE KEYPAD 32 AND UPDATETHE DISPLAY 34 IF REQUIREDGO TO TASK RETURNTASK 2FILTER THE PRESSURE INPUT SIGNALIF A MESSAGE HAS BEEN RECEIVED VIATHE SERIAL PORT QUEUE THE ANSWERGO TO TASK RETURNTASK 3CALCULATETHE PRESSURE IN PSICHECK FOR HIGHEST ORLOWEST RECORDED PRESSUREIF TRIGGER IS SET ANDTHE PRESSURE HAS NOT BEENGOING DOWN FOR 0.5 SECCOUNT A STROKE AND CLEARTRIGGER - IF THE PRESSUREHAS NOT BEEN GOINGDOWN FOR THE SELECTED TIME SET TRIGGERGO TO TASK RETURNTASK 4READ THE FLOW METER INPUTSUPDATE THE FLOW VOLUMESGO TO TASK RETURNTASK 5CALCULATE FLOW RATEGO TO TASK RETURNTASK 6UPDATE THE FLOW RATE READINGSGO TO TASK RETURNTASK 7IF IT IS TIMETO STORE DATA DO ITGO TOTASK RETURNTASK 8IF ANY OF THE INPUTSARE ABOVE OR BELOW THEIRSET POINTS TAKETHE SPECIFIED ACTIONGO TO TASK RETURNTASK 9CALCULATE THE AVERAGESTROKES/MINUTE FORTHE LAST 10 STROKES AND UPDATETHE STROKES/MINUTE REGISTERGO TO TASK RETURNTASK 10IF IT IS TIME FOR THE DAILY REPORT DO ITGO TO TASK RETURN______________________________________ 
    
     Table 1 below is a sample display or output from the pump monitoring system used in connection with a single well having a downhole hydraulic pump. 
     
                       TABLE 1______________________________________    STROKES/PER INSTANTANEOUS  VOLUMETIME     MINUTE      PRESSURE (PSI) (BBLS)______________________________________11:42    0           1290           011:57    35.5        1290           512:12    24.5        1290           10.112:27    29.5        1290           15.212:42    33          1275           20.212:57    39          1290           25.213:12    30.5        1290           30.313:27    29          1275           35.313:42    29          1275           40.413:57    38          1275           45.414:12    31          1290           50.514:27    25          1275           55.514:42    35          1275           60.614:57    27          1290           65.615:57    30.5        1275           85.816:12    26          1290           90.916:27    37.5        1275           95.916:42    38.5        1260           10116:57    37          1275           10617:12    24.5        1260           11117:27    29          1260           11617:42    32.5        1260           121.117:57    36.5        1275           126.118:12    21.5        1260           131.118:21    31          1245           136.118:42    32.5        1245           141.118:57    25.5        1245           146.219:12    40.5        1245           151.219:27    40.5        1245           156.219:42    36.5        1245           161.219:57    37.5        12.45          166.220:12    35.5        1245           171.220:27    24          1245           176.220:42    24          1230           181.220:57    24          1245           186.221:12    30.5        1245           191.221:27    26          1245           196.221:42    27.5        1245           201.321:57    30.5        1245           206.322:12    35.5        1245           211.322:27    30.5        1245           216.322:42    31          1260           221.322:57    35.5        1260           226.323.12    33          1260           231.3______________________________________