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  • SPESPE 21174

    Computerized Well Analysisby A. L. Podio* - UNIVERSITY OF TEXAS AT AUSTIN and J. N.McCoy* - ECHOMETER CENTER

    * SPE members

    Copyright 1990, SocIety 01 Pelroleum Englnee,.

    This paper was prepared lor presentation al the SPE latin American Plllroleum Engineering Conlerence held In Rio de Jenelro, October 1~19. 1910.This Paper waa selected lor presentallon by an SPE Program Coomlttee lollowlng review oflnlorma1lon contained In an alllllrllCt .,bmlI1ecI by the Eauthor(s). Contents ollhe peper, as presented, have not been reviewed by lhe SocIety 01 Petroleum Englnee,. and era .,bjee:l1O correction bythe author(s). The malerlal, as pr_ted, does nOI _rtly reflect any p

  • 2 CDMPOTERlZED WELL ANALYSIS SPE 21174

    Well performance in the context of thispaper addresses the complete well system in-cluding: the reservoir, the wellbore and thepumping components. Visualization of wellperformance is thus defined as: the ability tounderstand how these elements interactto yield the present conditions ofpressure, flow rates, loads, efficiency,etc.

    This ability allows the production engineerto evaluate the effect of changes in the operatingparameters such as speed, stroke, surfacepressure, on/off time, etc. and/or changes in thewell configuration such as pump depth, rodsizes, surface unit geometry, well stimulation,etc. on the overall performance of the well.

    For many years, the industry has had accessto the individual components of this system:acoustic well soundings, dynamometermeasurements, well test records, pressuresensors, transient well test data, etc. The WellVisualization System unifies all these elementsto provide the complete picture of theperformance of the well. Figure 2 is a schematicthat allows visualization of the well'sperformance.

    The data presented in this graphic displaygive at a glance the principal parameters to makean initial evaluation of the well's performance.'fhe operator controls the data in the boxedfields and performs any of four operationsdepending on the nature of the parameter:

    Enter a new value. Acquire data. Recall stored values. Request More Details.

    For example: values such as gas, oil andwater production are parameters that are gen-erally entered manually or recalled from adata base; polished rod load, annular liquidlevel, motor current, are generally acquiredusing the Analyzer. Plunger travel, pumpefficiency and flowing bottom-hole pressure areparameters that are calculated in detail fromanalysis of the other data.

    Figure 3 is a block diagram illustrating thehardware and software configuration that arerequired for implementation of the WellVisualization System for which the two corner-stone elements are Acoustic Well Soundings andPump Performance Measurements.

    Acoustic Well Soundings

    Acoustic echo-ranging techniques to gener-ate well soundings have been in effect for overfifty years to aid in the analysis of pumping

    wells 1. Early application was limited todetermining the presence of liquid in the annulusabove the pump. If liquid was found over thepump then the operator knew that additionalproduction was available if a larger pump "Yasinstalled; or, if the pump were not operatmgproperly, that the pump should be pulled andrepaired.

    Soon after the development of these in-struments, some operators realized that properinterpretation of the records could yieldadditional information. In particular bottom-holepressure was calculated from the summation ofthe surface casing pressure plus the gas columnhydrostatic and the liquid column hydrostaticpressures. This presumed some knowledge ofthe density and distribution of the oil and waterin the liquid column especially in the case ofshut-in wells where relatively high liquidcolumns were observed.

    Operators also observed that in those in-stances where gas was vented from the annulusthe calculated bottom-hole pressure was ex-cessively high. This was attributed to thelowering of the effective liquid gradient by thepresence of gas bubbles in the liquid columnabove the perforations. C. P. Walker2 patenteda method for determining the density of annularliquid columns whiCh are ar~at~d by gasbubbling upward through the hqUld. Walkerpresented a technique wherC?by a back-pres~urevalve is used to control and mcrease the casmg-head pressure causing the annular liquid level tofall a distance corresponding to the pressureincrease. The gradient of the gaseous liquid iscalculated by dividing the change in pressure atthe top of the gaseous liquid column by thecorresponding drop in liquid level. This gradientis then used to calculate the bottom-hole pres-sure.

    If the back-pressure valve setting is furtherincreased until the the top of the gaseous liquidcolumn is stabilized in the vicinity of the pumpintake, which generally is near the perforations,then the producing bottom-hole pressure can beestimated quite accurately since the contributionof the hydrostatic pressure from a shortgaseous-liquid column is small in. relation to. thecasing-head pressure, and errors m the gradi~ntestimate will not significantly affect the resultmgtotal pressure. In the majority of producingwells in the United States, the liquid level isnear the pump inlet and the casing-head pressureplus the gas hydrostatic will yield a very closeestimate of the producing bottom-hole pressure.This method which was presented over 50years ago is still one of the most useful methods

  • SPE 21174 A. L. PODIO AND J. N. MOODY 3

    of obtaining accurate producing bottom-holepressure.

    Recent studies by Podia, McCoy, et a1. 3have presented a technique of obtaining thecasing annulus gas flow rate by measurement ofthe casing annulus gas pressure buildup rate.Utilizing the casing annulus pressure builduprate and the void volume in the annulus, areasonably accurate casing-head gas flow ratecan be obtained. Knowing this flow rate, anestimate of the liquid column gradient ismade.using an experimentally determined fielddata correlation. This permits to calculate areasonably accurate producing bottom-holepressure even when gaseous liquid columnsexist above the pump.

    ~he operator can also determine the specificgraVIty of the gas when an acoustic wellsounding is made since the acoustic velocity andthe pressure are measured and the average gastemperature can be estimated. Determination ofthe annular gas specific gravity permits a moreaccurate calculation of the gas column pressure.

    Funher refinements in obtaining bottom-hole pressures by improvements in determiningthe gas column pressure and the liquid columnpressure along with electronic and mechanicalimprovements in processing and automation de-vices resulted in the development of equipmenttQ obtain acoustic liquid level data and casingpressure data automatically without the need ofoperator assistance4

    Computer-based Acoustic Measurements

    Digital signal processing, utilized so ex-tensively by the geophysical industry, and theavailability of small lap-top computers offersignificant advances and improvements inacoustic well sounding. Three importantachievements are possible by utilization of amicrocomputer. First, the computer can processthe acoustic data digitally to obtain moreaccurate liquid level depths, automatically.Second, the determination of bottom-holepressures from the acoustic liquid levelmeasurement, the surface pressure, and prop-erties of the produced fluids is automaticallyavailable. Third, the computer offers automaticoperation of the equipment in that the computercan be programmed to perform well soundingsand obtain casing pressure measurements oncommand, without operator attention.

    The Well Analyzer's computer and AID con-verter can be used in conjunction with anymodern manually or remotely operated acousticgas gun and microphone. The gas gun gener-ates an acoustic pulse. The microphone con-

    verts the reflected acoustic pressure pulses toelectrical signals. These signals are digitized bythe analog to digital (AID) converter and storedin the computer. This configuration is illustratedin Figure 4. The computer displays these signalsand processes the data as instructed by softwareto automatically determine liquid level depth.

    The analysis yields not only the distance toliquid level, but also the producing bottom-holepressure, therefore, the casing pressure must bemeasured at the time of liquid leveldetermination. If liquid is present above theformation and gas is flowing upward in thecasing annulus, the casing vent valve should beclosed and sequential measurements of casingpressure should be made for approximately 10-15 minutes so that an accurate casing pressurebuildup rate can be obtained. From this and theannulus void volume, the casing annulus gasflow rate is calculated. This allowsdetermination of the gaseous liquid columngradient if liquid exists above the pump.

    Software performs multiple functions in thisanalysis. First, well data are recalled from thedatabase. This includes the well depth, pumpdepth, average tubing joint length, formationfluid properties, formation temperature, well testdata and other parameters. These data arenecessary for accurate bottom-hole pressuredetermination. Software also processes thesignal echoes from the well and determines thedistance to the liquid level. The operator isalerted if liquid exists above the formation and acomputer analysis of the background noiseindicates the probability of a gaseous liquidcolumn. Further analysis based on inflowperformance includes an estimate of themaximum production rate of the well if theproducing bottom-hole pressure were reduced toa minimum value.

    Detailed Acoustic AnalysisWhen the acoustic liquid level is determined,

    the display, shown in Figure 5, is observed bythe operator after an acoustic pulse has beengenerated at the surface of the well and reflectedsignals are received by the microphone. The topinsert shows the raw data. The beginning is atthe left. The background noise, the initialacoustic pulse and the reflected signals areshown. Data are recorded past the time at whichthe liquid level reflection is expected. Thevertical line at the liquid level kick indicates theexact time which the software selected as theonset of the liquid level signal. The liquid levelkick is at 8.113 seconds.

    Automatic selection of the liquid levelreflection is undertaken by a pattern recognitionscheme that involves the amplitude, polarity,

  • 4 CXMPUTERlZED WELL ANALYSIS sPE 21174

    width and phase shift of the received signals.The software scans the digitized record andselects all the signals that satisfy the patternrequirements, then selects the most probable topresent to the operator. The arrow keys can beused to scan through the other possible liquidlevel signals.

    The lower right hand inset shows the detailof the liquid level signal.selected by thesoftware. Note that for this well, which istypical of many pumping wells with the fluid ator I1ear the perforations, the liquid level signal ispreceded by a negative-going signal producedby the tubing anchor ( at about 7.9 seconds).The presence of the perforations just above theliquid level is observed as a positive-goingsignal prior to the large negative spike caused bythe liquid reflection.

    The two vertical lines shown in the mainupper window at 3.5 and 4.5 seconds delimitdata which are shown as raw signal on thelower left hand insert. This raw signal isprocessed to accent collar reflections and isdisplayed immediately above the raw signal.The software determines an estimate of the totalnumber of collars from the surface to the liquidlevel using the frequency of this processedsignal as an average value of collar count perunit time;

    Using the PAGE-UPIPAGE-DOWN keysthe operator controls the signal scale for the toppresentation of the data. This allows detailedexamination of the raw signal as a means ofquality control and to insure that the proper kickhas been selected for the liquid level response.

    Observation of this display allows the op-erator to visualize the background noise presentin the well before the shot, the transmittedpulse, the reflections from the collars and theliquid level kick. In general the softwareselection of the liquid level will correspond tothe correct determination. However, if a tubinganchor, upper perforations, a paraffin ring orother obstructions exist in the annulus, theprogram may select one of these signals as theliquid level. In these instances the operator canuse the arrow keys to displace the liquid levelmarker to the proper time. After this is done insubsequent tests the software will not accept theearlier signal arrivals. In some extremelydifficult conditions, identification of the properliquid level reflection may necessitate artificiallymoving the liquid level either by shutting downthe well or increasing casing pressure in order toverify that the proper signal has been identifiedas the liquid level reflection.

    After the raw data has been displayed theoperator has the choice of a display of the wellanalysis sheet, a display of the acoustic data

    which was processed to accent and count thecollars, or a display of the raw signal andprocessed signals from which the operator cancount joints and analyze the signals. When theoperator acknowledges that the raw data andselected liquid level kick and indicated collarsare satisfactory for analysis, the softwareprocesses the raw data and counts the number ofjoints to the liquid level. The operator candisplay these processed data if desired, so as tovisualize the quality of the signal obtained fromthe well and the accuracy of the count of tubingjoints to the liquid level. If the display of theprocessed signal showing tubing joints is notsatisfactory to the operator, he has the option torequest a sideways printout of the raw signaland processed signals including a band-passfiltered signal to accent the deep collars and ahigh-pass filtered signal to accent all of thetubing collars in the well. This display andprintout of the raw data in conjunction withfiltered data allows the operator to perform adetailed study of variations in cross sectionalarea of the annulus. The printout will showanomalies such as different tubing joint lengths,salt rings, paraffin deposits, submersible pumpcable splices, casing holes, casing leaks, tubingleaks, multiple tubing strings, gas lift valves,upper perforations, changes in tubing andcasing diameters, and any other condition whichaffects the area of the annulus. Examples areshown in Figures 6a,6b and 6c. The bottomgraph displays data which has been processed toaccent deep collars by filtering so as to obtainsinusoidal signals which are easily counted interms of number of collars. The upper chartshows the raw signal processed with a highpass filter to remove the DC and low frequencycomponents. The collar reflections and signalsfrom small anomalies are accented in thispresentation.Figure 6a shows the portion of thesignal from 1 to 2 seconds (time increases to theright) after the shot.Collar reflection are easilynoted as sharp negative spikes. The maximumpeak to peak amplitude of the signal is 17.486mv. at the beginning and about 1/3 of thatamount at the end of the frame. .

    Figure 6b shows a detail of the signalbetween 3 and 4 seconds. The peak to peakamplitude has decayed to 2.716 mv. At about3.6 seconds a large positive cycle can beobserved. This corresponds to the annularenlargement caused by the change of tubing sizefrom 2-1/2 to 2 inch.

    Figure 6c shows the signal from 7 to 8seconds, just before the arrival of the liquidlevel reflection. The negative pulse at 7.9seconds corresponds to the annular restrictioncaused by the tubing anchor and should not be

  • SPE 21174 A. L. PODIO AND J. N. MCCDY. 5

    mistaken by the fluid level which was identifiedcorrectly at 8.113 seconds in Figure 5.Also notein Figure 6c that the filtered signal greatlyimproves the ability of the operator to recognizeand count the collars which are hardly visible inthe raw signal which at this time has decayed toa peak to peak amplitude of 1.657 mv.

    The complete signal record, after digitalprocessing using a narrow-band fIlter (15.8 to18.8 Hz. in this case) is shown in Figure6d.Superimposed on the signal are a series ofunit spikes in phase with the signal's negativecycles, and at a frequency which matches theprevailing frequency of the signal.Thesefrequencies are indicated on the display for eachgroup of ten cycles beginning from 1/2 secondafter the shot and ending just before the fluidlevel reflection.The first group frequency isused to extrapolate back to zero time (yielding8.7 cycles) and the last group frequency is usedto extrapolate forward to the fluid levelreflection yielding 1.4 cycles. The total numberof cycles is summed to yield 140.1 cyclescorresponding to an equal number of tubingjoints.Using the tubing tally or average tubingjoint length the distance to the fluid level is thencalculated to be 4260 feet

    The operator thus can use these screens andprintouts to analyze the conditions in the welland to insure that the data is satisfactory andfurther computations can proceed and will yieldaccurate results.

    Detailed Well Analysis DisplayAcceptance of the computer's interpretation

    of the acoustic data, results in the detailed wellanalysis screen display shown in Figure 7.

    The objective of this display is to providecomplete visualization of the wellboreconditions at the time of the measurement. Thefigure is divided in two sections: on the right isa schematic diagram of the wellbore andreservoir configuration, on the left are severalblocks containing quantitative infonnation aboutthe well and its past performance.

    The quantitative data on the left half of thefigure is designed to present vital informationabout the well. In the upper left hand block, thewell, company, operator and data are shown.Well data are shown in the block immediatelybelow. In the bottom block recent BHPmeasurements are summarized. In the upperright block, the results from the latestproduction test are included. The central block isused to present the results of well performanceanalysis based on a Vogel-type IPRrelationship. This includes the current producingrate efficiency and the maximum potential

    production achievable by reducing bottom-holepressure to a minimum value.

    The well schematic includes important pa-rameters such as tubing depth, perforation depthand other characteristics. The currentlymeasured casing pressure, casing pressurebuildup rate and the calculated casing annulusgas flow rate and gravity are printed oppositethe gas portion of the well. Just below areprinted the depth to the gas-liquid interface andthe percentage of liquid present in the gaseousliquid column. At the bottom of the well areprinted the calculated producing bottom-holepressure (PBHP) and the most current value ofstatic reservoir pressure (SBHP).

    Every fifteen seconds during the time sincethe fluid level shot was fired, the computerautomatically acquires the casing-head pressureto determine the annular gas flow rate.For thiswell this is shown in Figure 7a, which indicatesan increase in pressure of 1 psi in 2.5 minutes.The linearity of this increase is also an indicationthat steady state flow has been established inthis well. An erratic pressure profile wouldindicate that additional pumping should becontinued before additional testing is to beundertaken. This rate of casing pressure buildupis used to calculate the annular gas flow rate inconjunction with the annular geometry and thegas fraction in the fluid column is determinedusing a correlation determined from numerousfield measurements 3

    In this example, the 82-ft fluid columnabove datum consists of a mixture of oil and gaswith about 59% liquid. This column'shydrostatic, plus the annular gas hydrostatic andthe casing-head pressure result in a producingbottom-hole pressure of 103 psia.Consideringthat the stabilized formation pressure is 1214psia, and using Vogel's IPR relation, theprogram determined that this well is beingproduced at 98% of the maximum produciblerate.

    Analysis of Wells With Hi~h Fluid LevelsOperators often interpret the existence of a

    high fluid level as an indication that a well is notbeing produced as efficiently as possible.Remedies for this situation include increasingpump displacement by varying pump stroke andstrokes per minute, lowering the pump and/orreplacing the pumping unit with a larger one.Often however, the desired production increasedoes not materialize because the well'sperformance was not accurately analyzed

    Figure 8 shows an example of a well inwhich it was detennined that an annular fluidcolumn of about 3050 feet in height is presentabove the datum. Figure 8a shows that casing

  • 6 COMPlJTh'RIZED WEilJ ANALYSIS sPE 21174

    pressure buildup which was measured duringthe test and which yields an increase of 33.8 psiin 13.7 minutes. The software determined thatthis corresponds to an annular gas flow rate of147.9 MCF/Day, which yield an annular fluidcolumn which is a gas-oil mixture with only23% liquid. The resulting flowing bottom-holepressure of 321.4 psia indicates that the well isbeing produced at 96% of the maximum flowrate. In this case any attempts at decreasing thefluid level above the formation will result invirtually no increased production.

    ''On the other hand the well analysis shownin Figure 9, which indicates a fluid column of1835 feet above datum which is determined toconsist of 88% liquid based on the casingpressure buildup of 0.4 psi in 4.3 minutesshown in Figure 9a. In this case the producingbottom-hole pressure of 631.1 psia whencompared with the reservoir pressure of 1003psia indicates that additional drawdown ispossible and the present rate is only 56% of themaximum achievable rate. The well is thus agood candidate for a study to determine theappropriate actions needed to reduce the fluidcolumn above the formation.

    Automatic QperationThe automatic acoustic liquid level con-

    figuration (Figure 4) consists of the computer,AID converter and the remote-fire wellheadincluding the gas gun, microphone, andpressure transducer. A 12-volt battery (which issimilar to batteries used in automobiles) and alarger gas supply bottle for operating the gasgun are used when undertaking long durationtests.

    The operator programs the computer to ob-tain data points. Each data point consists of thetime, the distance to the liquid level and thecasing pressure measurement. Data points areobtained as programmed by the operator. Datapoints can be obtained on a shots per hour orshots per log cycle basis. This offersconsiderable versatility in the acquisition ofdata.

    The software obtains data points as pro-grammed by the operator. This data is pro-cessed to obtain bottom-hole pressures. Thecasing pressure, liquid level depths and bottom-hole pressures are utilized in conventionalbuildup analysis plots to determine well andreservoir characteristics as shown in Figure 10.Software also includes type-curves to aid inanalysis of data.

    Acoustic Data StorageThe computer and AID converter convert the

    analog signal from the microphone to digitized

    data. This data along with time and casingpressure are stored on a floppy disk. This datacan be transported to another computer forfurther processing.

    Beam Pump Performance Measurements

    In The United States rod pumping contin-ues to be the most widely used method of ar-tificiallift. Current economic conditions dictatethat maximum efficiency be maintained in theseinstallations at all times so that new and easiermethods of design and analysis are beingdeveloped almost continually. These methodsare principally based on Gilbert's5 and Fagg's6development of the beam pump dynamometerwhere the load at the polished rod was recordedgraphically as a function of the travel to generatea chart which represented the work undertakenat the surface unit for every pump stroke.Modern developments have concentrated inrefining the techniques for interpretation of thecharacteristics of this load-displacement curveso that a detailed analysis of the system can beundertaken which yields among other:

    Load distribution in the rodstring

    Load-displacement at the pump Valve operation and leakage Surface torque, counterbalance

    efficiency. Fatigue loading, rod buckling Motor performance

    Recently, with the advent of high perfor-mance digital data acquisition systems, attentionhas been given to an even more completeanalysis of pumping unit performance. Lea andBowen7 present results from simultaneousmeasurements of ten dynamic parameters(Kilowatts input,power factor, motor torque,gear torque,polished rod position, velocity,acceleration and load, motor speed and unit'sstrokes per minute. Their study concluded thatthis type of data was very useful in calculationof pumping unit losses which are needed foraccurate torque calculation and prime moversizing. They also indicate that these datacombined with simultaneous measurement ofdownhole pump performance and wellborepressures would yield a complete analysis of thebeam pumping system.

    Dynamometer measurementsThe Well Analyzer provides means to ac-

    quire data from load and position transducers in

    L- -'- "_~__. .-l

  • SPE 21174 A. L. PODIO AND J. N. MCCOV 7

    order to undertake conventional and/or advanceddynamometer analysis.

    In this mode the system's principal objectiveis to provide the maximum flexibility withregard to data acquisition, so that the operatorcan select various types of commerciallyavailable transducers or use custom units of hisown design. The analyzer provides means foracquiring and displaying the dynamometer dataand to store the same information on diskette forfurther processing and analysis.

    Loatl Measurement

    The accuracy required for quantitative dy-namometer analysis limits load measurement tousing some type of strain gage load cell8 Ac-cordingly rod load input from multi-elementresistive bridges is provided with the capabilityof determining if accurate cell balance ismaintained. The display alerts th operator of anypotential problems. A regulated power supply isused for accurate bridge excitation.

    Position Measurement

    Various types of position transducers canbe used. The unit provides the necessary ex-citation voltage for resistive type positionindicators as well as for accelerometers in-corporating signal conditioning and amplifi-cation. The operator selects and enters thenecessary parameters through the set up menus.

    Data Acquisition

    The load and position input channels can besampled at a rate of up to 1000 per second,which for normal pumping speeds will yieldmore data than necessary. The operator thusselects adequate sampling rates from a menu ofsuggested values which depend on the pumpingspeed. Similarly the operator has the choice ofcontinually recording the data stream overnumerous pumping cycles or for a specifiednumber of cycles as necessary. Data is storedas pairs of values of load and position (oracceleration) as a function of time (time series).This is the preferred data set for subsequentdigital processing in dynamometer analysisprograms.

    Depending on memory and storage medialimitations the length of the data series that canbe captured for a given sampling rate will bedifferent in every case. In the continuousrecording mode the most recently acquired datawill be available at a given time. When theoperator determines from the display thatadequate data has been acquired he may then

    stop acquisition and the data is transferred to thediskette.

    Data presentation

    Due to the speed of the lap-top computer,the dynamometer data is displayed in real time,either as separate load and displacement timeseries or in the conventional dynamometerpresentation of load vs. displacement.

    The operator can select special portions ofthe data series for display in more detail so as tostudy special characteristics of the signal overone specific cycle or series of cycles. Theselected data can then be stored in separate datafiles for subsequent processing, analysis andplotting.

    This is illustrated in Figure 11 which showsthe computer screen during acquisition of thedynamometer data. The upper trace represent theload vs. time recording.The middle trace showseither the position, velocity or accelerationsignal vs. time depending on the type oftransducer used and the operator's choice. Datamay be acquired for a fixed length of time(selected by operator) or continuously in a free-running mode until interrupted from thekeyboard which freezes the display:

    When the operator is satisfied with thedynamometer waveforms, he branches to thedynamometer visualization display which isshown in Figure 12.

    The principal objective of this display is togive immediate indication as to whether thepumping unit is operating properly or not. Thisis achieved by presenting the current dy-namometer card as well as typical surface cardsobtained previously for the particular well. Theleft portion of the display contains quantitativedata describing the pumping systemconfiguration, last well test results, currentoperational parameters and a directory ofdynamometer data files acquired in the past.Theright portion of the display comprises threegraphic windows. The upper window showsthe dynamometer card that corresponds to thedata in Figure 11. (note that if the selected datacontains several pump strokes these. will besuperimposed). The middle window allows theoperator to display any of the previouslyrecorded dynamometer cards. The datadisplayed in the figure corresponds to what hasbeen identified as a NORMAL surface card forthis well. Any of the other cards in the directorycould have been displayed. The bottom windowalways displays the surface dynamometer cardthat has been identified as representing partiallyand fully pumped-off conditions for this well.

  • 8 CDMPUTERIZED WELL ANALYSIS SPE 21174

    In eac~ of the windows is also printed data forthe flUId level, casi~g-head pressure, pumpingspeed and stroke whIch were present at the timethat the data was recorded. Numeric values ofthe standard key parameters as defined in APIR P 11 -L 9 are tabulated for the currentdynamometer card and for the "type" cards as ameans of quantitative comparison of criticalvalues.

    . The dynamometer visualization display thusgIVes to the operator immediate indication thatthe pumping unit is operating normally or thatsome abnormal condition is present. Whenfurther dynamometer analysis is required thecurrent data is assigned an identifier and storedin the data base for subsequent processing.

    Dynamometer Analysis

    Acquiring the dynamometer data and storingit in diskette files in text form, allow theoperator to export this information to otherdynamometer analysis packages so as to gener-ate conventional or customized reports on pumpperformance etc. Recently developed expertsystemslO and pattern recognition software fordynamometer analysis also allow importingdata in time series format. These advancedprograms can generally operate in mediump'erformance lap-top microcomputers so thatsome of this analysis can be undertaken in thefield.

    In particular, given the time series data ofpolished rod load and displacement shown inFigure 11, it is possible to calculate thecorre~pondin~ lo~d vs. displacement diagramsat v~ous pomts m the sucker rod string and inpartIcular at the pump, as shown in Figure 13reprinted from Gibbs and Neely!!. This givesaccurate description of the stresses in the rods aswell as definitive evaluation of the efficiencyand conditions at the down-hole pump.

    Integration with Fluid Level Data

    From the Dynamometer mode it is possibleto return to Acoustic Well Sounding mode andperform measurement of the liquid level vir-tually simultaneously with the acquisition of thedyn.amometer data. This presumes that theeqUIpment has been previously set up to per-form acoustic measurements. Correlation be-tween the acoustic and dynamometer data canthen be undertaken since the system automati-cally records the time of day when all mea-surements are made. This capability allows theoperator to monitor the dynamometer data as afunction of varying fluid level above the pump.

    When this is carried out until pump-off takesplace it is possible to identify accurately thefeatures in the dynamometer card that correlatewith the onset of pump-off.

    A special mode of dynamometer data acqui-sition allows automatic continuous monitoringof the load and travel data for extended periodsof time while capturing data for a given numberof pumping cycles at specified time intervals oronly when the dynamometer data deviates froma predetermined base case or exceeds certainvalues.

    Since the system is capable of automaticacoustic liquid level measurements, the operatorcan specify that at any time when dynamometerdata is recorded then measurement of the liquidlevel be also undertaken. This capability greatlyenhances the diagnostic potential of this system.

    In addition, since liquid level data allowscalculation of bottom-hole pressure, the pumpintake pressure can easily be calculated and usedin more accurate analysis of pump dynagraphssince knowledge of this parameter allows abetter estimate of the rod system's friction anddamping factors.

    Well Performance Data Acquisition

    In certain applications to well performanceanalysis it may be necessary to have access todata which is not normally recorded for themajority of producing wells. For this purpose,the Well Analyzer includes three generalpurpose input channels, in addition to thechannels previously discussed, which greatlyenhance its versatility. These channels allow theacquisition of data from general purposetransducers so as to be able to generate timehistories of specific variables such as pressure,temperature, flow, composition, current,voltage, power, etc. with the only limitationbeing that appropriate transdUl~ers must beavailable to measure the varible of interest andthat they generate appropriate electrical signals.

    These applications may include monitoringof a number of additional parameters duringdynamometer measurements, such as the tubingpressure or temperature or the electric currentand power drawn by the prime mover. Duringflowing well testing, the data from a portabletesting unit, such as gas flow rate, liquid flowrate and water cut, could be monitoredcontinuously. In submersible pumping instal-lations, it is possible to monitor the motorcurrent, wellhead pressure and flowing tem-perature in order to characterize the performanceof the system. In unloading and tuning of gaslift installations the acoustic liquid level data canbe recorded while monitoring both the casing

  • References

    Conclusions

    1- Walker, C. P.,"Determination of Fluid Levelin Oil Wells by the Pressure-wave EchoMethod," AIME Transactions,1937,pp.32-43.

    2- Walker, C. P. , Method of Detennining FluidDensity, Fluid Pressure, and theProduction Capacity of Oil Wells, U.S.Patent No. 2,161,733 ftled October 26,1937.

    A portable, compact and complete systemhas been developed for acquisition of acousticwell soundings, polished rod dynamometer dataand other surface measurements and forintegration of these data in a series of co-ordinated graphic displays on a portable mi-crocomputer. These displays allow the operatorto v~sualize the current conditions and presentperfonnance of the well and to immediatelyidentify existing or potential problems. Accessto a data base of past well parameters and toapplication programs for interpretation ofpressure buildup data, beam pump design,dynamometer analysis, etc. further enhances thesystem's diagnostic capability and pennitsoperation at higher levels of efficiency andlower costs.

    SP,..E_2_11_7_4 A_.:..-L. IWIO AND J. N. Mccx)v 9and the tubing pressures so as to have detailed 3- Mc Coy, J. N., Podio, A. L., and K. L.infonnation about downhole valve operation. Huddleston :"Acoustic Detennination of

    Producing Bottomhole Pressure" SPEFonnation Evaluation, Septembet 1988,pp. 617-621.

    4- Godbey, J. K. and Dimon, C. A.: "TheAutomatic Liquid Level Monitor forPumping Wells," J. Pet. Tech., August1977.

    5- Gilbert, W. E., "An Oil Well Pump Dyna-graph," API Drilling And ProductionPractice, 1936, pp.94-115.

    6- Fagg, L. W.: "Dynamometer Charts and WellWeighing," Petroleum Transactions,AIME, Vol 189, 1950, pp.165-174.

    7- Lea, J. F. and J. F. Bowen,: "Dynamic Mea-surements of Beam Pump Parameters"SPE Preprint No. 18187, October 1988.

    8- Svinos, J. G.: "Effect of Input Data Errorson Diagnostic Analysis of Rod Pumps,"Southwestern Petroleum Short Course,Lubbock Tx.1989.

    9- API RPI1L,Recommended Practice forDesign Calculations for Sucker RodPumping Systems, February 1977.

    10- Foley, W. L. and Svinos, J. G.:"EXPROD: Expert Advisor Program forRod Pumping,: SPE Preprint No.16920, September 1987.

    11- Gibbs, S.G. and A. B. Neely, : "ComputerDiagnosis of Down-Hole Conditions inSucker Rod Pumping Wells," J. Pet.llih.. January 1966, pp. 93-98.

    DATA BASE

    AcoustiCWell Surveys

    Well ConfigurationPumping system

    Well TestingReservoirHistory

    /WEll. PERFORMANCE

    VISUALIZATION

    SYSTEM

    /DynamometerMeasurements

    OtherDiagnostic

    Measurements

    Figure 1 - Schematic diagram of the Well Performance VisualizationSystem

  • SPE 21174 /0I . tee....,..

    IN. ".f SI'II\\~-R I".,.,.ZWIIUS I

    1 ...... 1 ..1 ..

    I ...u ROO I'TMU, ."A.....- I

    1----,--11 104 ,,..,111O-F'T

    I~~~ - 11,--_'"_"_'__-"Well Number _BROWN # '0'__Lease __ABC USA__

    Figure 2 - Well Visualization Schematic

    OfL:f.STIIO ]

    Acquisition Data Processor and APPLICATIONand SOF1WARE

    control control unit Analysissoftware

    Modemng

    ! SimulationINTERFACE

    DATA ACQUISITIONAND

    Ga'ffilOL EL.ECTRONICS

    If J I I

    ACOUSTIC EJ GENERALSOONDINGS PURP

  • SPE 21174

    WELLANALYZER

    Nitrogengas

    supply

    ToWell

    Figure 4 - Computer-Based Acoustic Liquid Level System

    11

    t18IIy

    rOStD32.id1 81-82-1998 13:362 4 6 Stc

    f4-MultiTl'lct J'5-WtIl Data r6-IIIPData Display

  • SPE 21174

    We 11: rOSTER32, Ad! 1.m to 2. 999 Seconds afte!' sho t6,592""

    Raw SignalPeak-Peak:

    11.486 !IV

    -lU95 !IV

    1fJ-

    J'i Itmd Data

    -Anow keys Move Signal-Isc-SavelExit Fl-llain FHollll'S fHuing f4-Multi bace F5-Nell Data r6-l11P

    Figure 6a - Detail of Acoustic Signal, 1.0 to 2.0 seconds.

    Well: fOSTER32, ad! 3.M to Ull Seconds arte!' shot1.368 llIJ

    Raw SignalPeak-Peak:2,116 IIY

    -1.348 IIY

    Fi IteJ'l!d Data

    -1.121 !IV

    8,536 ""Raw SignalPeak-Peak:1.651 IW

    -Al'l'Ow keys Move Signal-Isc-Save/Exi t Fl-llain fHollll'S fHuing F4-lkIlti tl'ace FS-Nell Pata 16-BIIP

    Figure 6b - Detail of Acoustic Signal, 3.0 to 4.0 seconds.Well: FOSIEm.ad! 7,. to 8. Seconds artel' shot

    ~

    -ArJ'OW keys Move Si gnal-Isc-SavelExit Fl-llain fHollars FJ-CaSing f4-llulti T1'iCe i'S-WeIl Data f6-IlIlP

    Figure 6c - Detail of Acoustic Sianal. 7.0 to 8.0 seconds.

  • rOSrIR32.ad1 148.1 Joints 426U Vt SPE 21174 13

    I seclsJ1t

    2 Sec 7,8

    4 Sec

    nee

    ~ IrilteJl IIidth:l5.8 18.8 Hz

    Uelocity:1B59 It/secEsc-Saue Exit T!-Main rHuing Buildup r4-lIulti TNCe l'5-llell Data '6-BIIP

    Figure 6d - Complete Acoustic Signal after filtering and Processingto Obtain Collar Count.

    rOSTIR32 PJ'oduction Casing r--PHILLIP! 25 BOPD dr/dT

    ~-m8 298 BNPD !.9psi Casing(Psig): 61.335 IICFID 2.5 MinsIIILL MIA lJOGIL IPR AHALYSIS fMInulaJ' CiS Flaw

    35 API Oil PBHP/SBHP:U8 (MCr/D): 28.41.85 \IateJl SC EHiciency:98XCiS SC:8,82 Max PJIOducing Rate

    tl. HaS 3~:~ I~~ L~id @t,: 112 69 It8Y. CO2 MSeJlU01Jl PJleSSllH

    TelmJlatllH : 1214 ~ia 5'X Liquid78 r SUJllace test thod-

    138 r BottOM GAlICE2.875 luLing 4 da~ Shut-In5.588 Casing Test ate:5-H8

    .... mDatu.- ~I~IIIP :1214~ 4342 gf;IP~II~PIPPlpppPBIIP(Psia): 192.8

    Esc-SauelExit n-Main fHolliJ'S n-Casing Buildup F4-Multi T!'ace l'5-Well Dita..Figure 7 - Detailed Well Analysis Visualization Displav

    Casing PNSSUN Buildup-test In PJ'ogHSS-2.8: :: 63.3

    ,

    62.9CaS

    62.5 ing

    62.1PSI

    61. 7 C

    1.6 -:, ,.. ,-: ,., .. ,.:-, , , .. "

    " .

    .

    1.4 ':.... . .. ' , :'., :., .. .

    . .

    6 1.2' . .. .. .: .. ... .. .. ........ ':" ....... :" ....... " .PS 8.8 : , :. .. : ..

    I

    I, 61.3

    -9,4 r----r.r-r--"T"""!"-.......~---..~-T 68.9I I ,86Tilll! Minutes

    Esc-SavelExit T!-Main F2-CollaJ' FHlultill'ace l'5-Data f6-BIIP r1a-OO IlIILDIIPFigure 7a - Casing Pressure BUildup Data, for Well in Figure 7.

  • SPE 21174 /i 1iridlk PJIoduction Casing .---84 BOP dP/dTNORXDl 163 BUP 33.8 psi Casing(Psig): ,51.691-93-1998 159 ItCr/D 13.1 MinsIIILL DAtA VOGEL IPR ANALYSIS ~nllliJI Gas Flow39 API Oil PBHPISBHP:8.12 (1U1D):147.9

    1.85 Ilatel'SC Etriciency:96Y.Gas SC:U9 Max Pl'oducing Rate

    8'/. H2S 1~1t ~~ Li id' ~8'/. H2 2~4 rt ~ ,~tI. CO2 ~mvOll' P1'eSSlll'f ~ I~'. m: LiquidTe~l'itlll'e : 2644 ~ia '179 r SUl'tace Test thad- 'I

    136 r BottoR BOP ;~ :12.788 Tubing 3 da~SlIut-in ~ ,I,5.588 Casing Test te:4-8-99 ,:~~ ,:~ ;2644Datu :~~III

    n793 ~,I,IN,I~,I,IN~,PIIP(Psial: 321.4

    :Sc-SavelExit rHlain rZ-CollaP5 r3-Cising Buildup r4-~Hi TNet F5-IItH hta..Figure 8 - Well Analysis Display for Well With a High Annular FluidColumn Containing 77% Gas.

    Cas

    78.1 ing

    PSIG64.5

    11.3

    84.9

    .. , -:. ....... , , ..:., " ..

    . .

    .................... " , , .

    . ' .

    27.2 : : ; : .. . '

    6.8 .,

    6 29.4 .,."

    PS 13.6 .I

    - ure UI up aa or e In I)JOlU148L PI'ocluction Casing .---BIPCO 11 BOP dP/dTG.tlIHARD 273 BWPD 8.4 psi Casing(Psig): 44.1 .87-92-1998 6 IICfID U MinsNELL DATA UOCIL IPH AllALYSIS AnnuliJI Gas Flo.

    38 API Oil PBIIPISBHP:8.63 (MCfID): 6.71.85 Watu SC Utici ency:56Y.Cas SC:9.88 Max PI'oducing Rate

    tI. H2S 4~~:~ I$~ Li~id ~8'/. HZ 3 4t&Yo CO2 ~~el'VDll' FNssW'e ~ WTeMpmtlll'f: 1883 ~ia 88y. Liquid79 r SUI'ace Test thad- ~/ I129 r BottOM GAUCE ~/ t2.387 tulling 3 da~ Smt-In ~/ i7.989 Casing test ate:5-S-99 'I' t~I' t :1lW~11I11111

    )atWil ':~~WL! ~/ :1993.,~:I,lnpl:~~, 4929 ~~;lplnN/

    PBIIP( Psia): 631.1

    Isc-SavelExi t Fl-Main rZ-Collm F3-casing Buildup rHalti t!'ace I'S-Ilell Data,.

    II II ----:-----:-----:----...:----l 57.7'''III ."

    . . .

    . . .

    . . .

    -6.8 : 59.9, I I .i

    6TiM MinutesIsc-SavelExi t fl-Main rHolliJI r4-l'1ltit!'ace I'S-Data F6-BHP F19-00 B11ILD11P

    Figure Sa Casing Press 8 'Id 0 t f W II' F ure 8.

    Fiaure 9 - Well Analvsis Disolav for Well With a Hiah Annular Fluid

  • 15

    45.2

    45.9

    Cuing PreSSUN Buildup-Test Finished-1.1 : : :

    . . .

    1.8 -: : : .Cas

    44.8 ing

    44.6PSI

    44.4 C

    44,2

    44,8

    9,2

    . .

    6 8.6' .. . ..

  • SPE 21174 16

    DYNAMOMETER VISUALIZATIONBrown f 1 lAST TESt 240001!C llS.& 10 IOtD ~".ck saith " I"'~10/3'89 4S I:F/O_tt ""TA "".A!:N' "" 12000,_11\9 ""It N 15."

    -'J'rpe:CoGYeatiooal S .. "".0aod! 16 CUNU:.NT oyHNtOHEnllPPP.L 214'75...= .2.00 indl 1G'1lL ,on 0

    -1Io