spe 17522 predicting power cost and its role in esp economics

5/23/2018 SPE 17522 Predicting Power Cost and Its Role in ESP Economics

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SPE 17522Predicting Power Cost and Its Role in ESP Economicsby R.E. Pankratz and B,L. Wilson, Oil Dynamics Inc.SPE Member

Copyr ight 19SS Society of Petroleum EngineersThi s paper waa prepared for presentati on at t he SPE Rocky Mountain Regional Msetlng, bald i n Caapsr, WY, May 11-13, 19SS.Thla papar waa se lec ted for presen ta tion by an SPE Program Committee fol lowing review of ioformatlon contained in an abatrac t eubmlt te~ by theauthor (a) , Con ten ts o f the paper, as praasn tsd, have no t bean rev iewed by the society o Psl ;uieum Eng lnse ra and are eub ject to correc tion by theauthor(a). The mater ia l, aa presented, dcwa not nsceaaarlly reflect any fmltion of the SocIefy of Petroleum Enginaera, ite officara, or members. Paparapreaantad a t SPE meet ings are aubjac t to pub lica tion review by Edi tor ial Committees of the Soc Ie fy o f Pe troleum Engineers. Permiaalon to copy lares tricted to an abatrac t of not more than 200 words. I llua tr at lona may not be wpled. The abatract should con ta in conspicuous acknowledgment o fwhere idby whom the paper Isp resen ted. Wri te Publ icat ions Manager, SPE, P.O. Sox 833836 , R ichardson, TX 75063.3636. Te lex , 730989 SPEDAL.

ments for the cable and the loaded motor based onINTRODUCTION the published manufacturers data and establishedEngineering principles, To adjust for totsl con-With the current pressure on profitability, the sumption, it uses a rule of thumb multiplier foreconomics of oil production are being closely switchboard and transformers efficien-scrutinized by most producers. This paper develops cy loeses.a method for estimating the power cost for elec-trical submersible pumping systems (ESPs) and views ?fostESP sizing procedures follow five basic steps;the role of power cost in the overcll picture of 1,2,5*economics for this tyrs of artificial.lift. Tovalidate the procedure that is used, the calcu- 1. Calculate the required total dynamic headlations have been compared to actual data taken from (rDH)for the desired flow rate. Thisfield tests of operating ESP S. inc .idesthe lift for produced fluid

rela:f.veto the inflow performance of theThis paper is directed toward the Engineer who is well, the losses in the tubing, and theresponsible for the selection of artificial lift required surface pressure,equipment. To increase the utility of the method,it uses only data published by the equipment man- 2. Select the pump that will meet theseufacturer and well established calculating routines, condf.tions,The total econon,icpicture of artificial lift would 3. Size the motor to fit the pump.have tn include many factors which are beyond thescope of this paper. This paper will limit itself 4. Size the cable to meet the motnrto the factors that are involved in the choices an requirements.Engineer has to make in the selection of ESPS.

5. Select the surface equipment for the cableOPERATTNG COSTS and downhole equipment needs.There are two methods for establishing ESP operating In general, the same steps are followed in calculat-Costs. The simplest is to actually measure the ing predjcted power costs for an ESP system. Thepower consum,.do In situations where meters are procedure starts after step 4, assuming that theinstalled on individual wells and monitored by the downhole equipment and power cable have already beenoperator or the power company, this method is selected or are already in operation.readily available and should be pursued. The majordrawback to this approach is that it can only be ESTABLISH OPERATING RPMapplied to equipment that iS already ?n operation orin locations that have metering svailable. Motor speed wfll vary with the load applied in

operation and since this speed variation will affectIf the installation is new or individual well meters pump performance and horsepower load as dictated bynot available then power consumption must be pro- the affinity laws, the first step in accuratelyjetted from available data. A rigorous analysis predicting power cost for a defined system ia tomust include every element in the system that will establish the actual operating speed of the motorconsl-tleower. The method that follows develops when I.oaded.power costs at the welJhead, including the require-All ESP manufacturers provide pump performancecurves that describe the expected performance of a*References and illustrations at end of paper. pumpunrieroperating conditions (Fig. 1). In the



interest of stendardfzation, all these pump cuwes Enter the 3500 RPM curve at Flow (3500), move up toare today published at 3500 RPM operating epeed. the head capacity curve and read the corresponding

head per stage (Catalog Hal/St @ IVOW (3500)).Motor performance cha~.acteriaticcurves are also Adjust the Catalog Head per ~tage at 3500 RPM foravailable from manufacturers. These curves (Fig. ~) the actual RPM to obtain the actual head per stageprovide expected performance of the motor as afunction of the percentage of full (nameplate) HP at operating RPM (Hal/St@ Flow (RPMo) with theformul.a:load when the speciff.ednameplate voltage is aup-plf.ed to the motor terminals. Performance Hal/St@ F1OY (RphfO)= Hal/St@ F1OW (3500) Xcharacteristics related to load in these curves (RPMo/3500) . . . . . . . . . . . . . . (5)include RPM, efficiency, power f.ictornd amPerafze.

Finally, multiply the Hal/St@ Flow times the numberDetermining actual operating RPM for an installed of stages to obtain the adjuated TDH (TDHo) producedunit is a four step iterative process; at the desired flow rate and operating RPM.

1. Determine the nonadlusted horsepower load TDHo = (Hal/St? Flow (RPMo)) x of Stages(HPn) developed by the pump and gas sepa- (6)rater usfng the formula; If TDHo is greater than or equal to the required

TDH, the installation will produce at least theHPn = ((Hp/staKe x Stages) + desired flow rate in the well. This flow rate and(Gas SepHP)) x Sp. Gr. . . . . . . . (1) power costs that exactly match the predicted figures

7 can be obt~jned by choking back the flow to the... Calculate the % motor load.(% Loadn) by target rate, or the system can be installed asdividing the motor nameplate horsepower defined and increased production will be obtained(HPm) into the nonedjusted pump horsepower as the pump operates further to the right on theload. performance curve. The calculation process for%Loadn=HPn/HPmx100.. . . ...(2) eatablshing this new production rate and the power

3.coat a~sociated with it involves the well IPR curveDetermine the intermediate motor speed and if beyond the scope of this paper.(RPMn) from the puhliahed motor

performance curve (Figure 2.) If IWO is lower than the required TDH, the operat-4. in% point wfll move to the left on the new headAdjust the horsepower load developed by capacity curve during operation to provide thethe pump for the intermediate motor speed necessary lift. This shift to the left of the head

using the affinitv law for horsepower. capacity curve will result in leas than desiredproduction flow. If this ia the case, f.twill beHPn+l =HPn x ((RPMn)/(3500))3 . . . .(3) necessary to select a larger pump and recalculate

5. the HPo, RPMo and TDHop to obtain an accurateReturn to steps 2 through 4 above and power cost prediction at the desired flow. Thisrecalculate % Loadn, RPMn and HPn+l. iterative procedure for determing RPMo, HPo andRepeat th~.sstep iteratively until TDHo la faf.rlytime consuming if done manually.convergence is reached and the adjust- A combination of the pump curve coeff?.cientssup-ment in RPMn and HPn are negligible. plied by most manufacturers with a fairly straight-At this point, the operating RPM forward computer program will simplifv this process(RPMo) and the horsepower load for the greatlv.system (HPol will have been determined.

Failure to make the RPM adjustment will affect pnwerOnce RPM convergence is found, it is a good practice consumption prediction significantly, resulting into recalculate the TJ)Hproduced by the svstem to errors that are proportional to the cube of themake certain that the pump will be large enough to ratio of the actual speed to 3500 RPM. It isme~t head requirements at the operating RPM and particularly crftf.calto take this into account whend,sired.flow. Omission of tkiisstep is one of the motor loads vary significantly from the load re-less understood reasons that ESP systems quired to produce 3500 RPM. Equipment in moat realoccasionally miss designed fluf.dproduction targets, life installations will rarely operate at 3500 RPM.To recalculate the produced TDH (TllHrJ)t is neces- MOTOR POWER CONSUMPTIONeary to adjust both the flow and the head shown ORthe 3500 RPM pump curve for the operating RPM Once the operating point has been estahl.ished,accordhg to the affinitv laws. For everv point on svstem power consumption can be determined. Thethe 3500 RPM curve which will produce the desired first step in this process is to establish thelow at operat.:ng RPM. This i.saccomplished bv Kilowatt requirements for the motor (KWm) undersolving the following equation: operating conditions. This is accomplished using

the motor characteristic curve and the relationshipF1OW (3500) = FICJW(RPMo)/((RpMO)/3500) between motor efficiency (Eff) and input and outputKw.:Where Flow fRPMo) ~.sthe desired flow rate and Flow Eff = Output KW / Input Kw . . . . . . . . (7)

(3500) is the correspondin~ flow at 3500 RPM. but since,OUtput KW = HPo X 0.7457 . . . . . . . . . (8)The second step f.nadiusting TllHt.sto obtain from andthe 3500 RPM curvr the head per stage produced at InputKW=KWm . . . . . . . . . . . . . . (9)Flow (3500), and adiust for the difference in RPM.

.n



Therefore, this is;Eff = (fiPox O.7457) /KWm . . . . . . . . (10)Or COST/month = KWt x S/KWH x 30 x 2 4 , . . (17)KWm=(HPoxO.7457)/Eff . . . . . . ..(11)

EKAMPLEEnter the motor characteristic curve at the RPM corrected % load and read the efficiency. Plugging 185 stage example pump has been selected for a wellthis number into Equation 11 will provide the motor that la expected to produce 1400 BPD of fluid with aKw (KMn). bulk specific gravity of 1.05 and a downhole tem-Cable Power Consumption perature of 160 degrees F. IPR analysia indicatesthat at this rate, the pump will be required to

produce 4800 Feet TDH, The pump will be driven by aIn addition to the motor power requirements, the 90 horsepower, 1165 volt, 46 amp motor that ia to becable itself will consume power. This power is afunction of the operating amperage, the cable powered by 5000 feet of 4 AWG polypropylenenon-stranded cable.resistance, and the conductor temperature.

From the pump performance curve (Fig. 1),The operating amperage (knps) for the system will be Hp/Stage = .4138 Hp/Stagethe same as the motor operating amperage. Thisvalue is calculated by multiplying the motor From Equation I, HPn = ((0.4138 HP/St x 185 stages)nameplate amperage times the appropriate factor + (0.0)) x 1.05obtained from the motor character~.sticcurve (Fig.2) HPn = 80.38 RpAmps = % FL Amps x Namepl.steAmps . . . . (12) The percent motor load from Equation 2,Cable resistance (Rc) in Ohms per thousand feet is %Load 1 = (80.38 / 90) x 100

available from the cable manufacturer. These % Load 1 = 89.31%valuea are a functton of the size and type ofconductor. Charts provfding the resistance ttt68eFfor two common types of clownholecable are shown in Entering the manufacturers motor curve (Fig. 2) at89.31% load, the intermediate motor speed (RPM l) isFigure 3. These values must be adluated as a 3511.16 RPM.function of the conductor temperature, which isitself a function of ambient (dowehole) temperature Adjusting the pump horsepower load for the affinityand the operating amperage. Charts relat~ng laws per Eq, 3,conductor temperature (Tc) (in degrees C) to ambient Hp ~ - 80,38 ~ (3511,16/3500)3temperature and conductcr current are given in HP2=f11.15HpFigure 4

This provides a new percent motor load from EquationThe formula for cable power consumption (KWC) is; 2,7 Load 2 = (81.15 / 90) x 100KWc=(Amps2xRtx3x L)/lf)OO.. . .(13) %Load 2?= 90.17%

where L is the cable length in thousands of feet Entering the manufacturers motor curve (Fig. 2) atand; 90.09%, the .tntermecliateotor speed (RPM 2) is3510.20 RPM.Rt = (RCX ( (234.5 + Tc) X (234.5 + 20.0) )

. . . . . . ,...0. . . . . . . . . . (14) Adjusting the pump horsepower load for the affinityThe formula for KWC is simply the familiar I squared laws per Eq. 1,R formula times three phases times the length ofcable. HP 3 = 80.38 X (3510.20/3500)3

HP 3 = 81.08 HpSystem Power R.equirementaThis provides ~ new percent motor load from equationHaving calculated the motor KW demand (KWm) and the 2,cab.1.eW (KWc), we now can obtain the power consumed Z Load 3 = (81.08 / 90) x lCH_Iat the well head (KWW); Z Load 3 = 90.09%

KWw=KWm+KWc . , . . . . . . . . . . (15) llnterin~the manufacturers motor curve (Fig. ?) atThis requirement will be slightly increased by 90,09%, the intermediate motor load (ZLoad 3), wefind less than a .01 RPM change in motor speed fromlosses in the switchboard, transformers and related that at 90.17%. We can assume convergence. Thesurface equipment. For an estimate of these losses,they are assumed to be 2.5% of the well head power operating RPM (RPMo) is 3510 RPM, the operating loadHPo is 81.08, and the operating Z Load ia 90.09%requirement. The total.system requirement (KWt)becomes the well head power times one plus the To check that the TDH produced bv this jnatallationsurface losses; will be at least the required 4800 ft., find the

flow rate at 3500 RPM that will adjust to 1400 BPDKWt=KWw x(l+0.025). . . . . . . ..(16) 3510 RPM from Eq. 4,The monthly operating cost is the total system power Flow (3500) = 1400 BPJI/ (3510/3500)requirement times the cost of the power (S/KWH) for Flow (3500) = 1395,93 BPDthe time period desired, For a thirtv day month,

.



4 PREDICTING POWER COST AND ITS ROLL IN ESP ECONOMICS SPE 17522

From the pump performance curve (Fig. 1), at 1396BPD, the pump will produce 26.00 Ft/Stg at 35~0 RPM.Thts number is adjusted as in Equation 5 in acr.or-dance with the affinity laws:

HD/St @ F1ow(RPMo) = 26.00 X (3510/3500)2HD/St @ F1ow(RPMo) = 76.16 feet

Finally from Equation 6,TDHo = 26.16 X 185TDHo = 4838.79 feetThis TDH exceeds the required by approximately 38.8feet and therefore the installation will produce atleast 1400 EPD during operation providing theTDH required calculation is correct.From the motor curve, Fig. 2, we see that thin motorw~ll operate at 87.94Z efficiency when loaded at90.09% of nameplate. From Eq. 11,KWm = (81.08 X 0.7457) / .8794

KWm= 68.75The motor will consume 68.75 Kilowatts of power.Again from the motor curve, Fig. 2., we aee tl.ntthis motor will draw 91.22% of nameplate amps at90.09% load. From Eq. 12,AlllpS .9122 X 46Amps 41,96From Figure 3, it can be seen that the conductortemperature for 4 AWG cable carrying 41.96 amps inan ambient temperature of 160F will be 171.F or77.C.From Figure 4, the cable resistance, Rc is 0.259ohms per thollsandfeet. From Eq 14, the totalimpedance of the cable is;Rt = (0.?59 X ((?34.5 + 77) / 234.5 +20.0))

Rt = 0,317From Eq 13, the KW dem~nd for the cable will be;

KWC = (41,96 X 0,317 X 3 x 5.0) / 1000KWC = 8.3?

From Equation 15;KWw = 68.75 + 8.37Kww = 77.1%

From Equation 16,KWt = 77.12 X (1 + 0.0?5)KWt = 79.05

Finally, from Equstj.on17;COST/month = 79,05 x $f).115/KWH 3flx ?4COST/month = S?,845 ($34,5130/vear)

It should he noted that in thjs example, the annualpower cost of $34,500 is about 1.3 times the listprice of the downhole equipment (excluding cahl.e),This is not at all unusual. Typical power costs forESP installations will exceed the list price of newdownhole equfpment within the first year of opera-tion.

SYSTEM COMPAR?SOWSWhen the method outlined above is used to compare

eeveral potential systems for the same well in aneffort to minimize monthly or annual operatingexpense, there is a danger of overlooking differ-ences in fluid produced. A power meter does notmeasure flow or produced head. To get a betterpicture of true operating cost, a total systemefficiency should b~ defined;

True Operating Cost = ($/KWX KWt X 24) / lOWX TDHo) . . . . (18)

In the example;True Operating Cost = ($0.05 X 79.86 X 24) /

1400 x 5000= $28.74 x 10V6 perBBL-FT-DAY

the first part, ($/KW X KW X 24), ia cost as read tiya power meter during a ?4 hour day but this costmust he normalized on a par barrel per foot of TDHbaais to make accurate comparisons between wellsthat produce at a different flow and TDH. Equation18 is nearly identical to the reciprocal of theformula for hydraulic efficiency of a pump;

Hydraulic Efficiency = (Flow X TJIH)/CXBHP . . . . . . . . . . . . . . . (10)where C is a constant

Tbe difference is that the true operating coat is ameasure of the total system efficiency instead ofthe pump-only efficiency. By using the reciprocalof this efficiency, higher efficiency in the systemis converted to lower cost,ACCURACYOne of the disturbing things about the methodpresented shove is the number of times that a numberis taken at three decimal accuracy from a manufac-turers curve or from well data and multiplf.edtimesa larfienumber. As an example, where horsepower Derstage is multiplied times the number of stages ifthe spectfic gravity is actually 1.06 in the aboveexample and the Hp/St is 0.42, the initial Z J.oadnis 91,51Z instead of 89.31Z. This will obviouslyaffect the accuracy of the calculations significant-ly. The question then becomes, assuming that thismethod is theoretically correct, how much faiths;louidan Engineer have in calculation of thisnature?.To address this iss teit is useful to examine thepotentjal sources of error in the method and identi-fy steps that w~.1.J help to control these errors..There are six main categories of potential error;calculation, equipment performance, well data, wellfluid properties, power supply, and surface losses.One of the first steps that should be taken toprovide accuracv in power cost prediction is toutilize the coefficients supplied by the manufactur-ers for establishing pump and mo~or performance andperform calculations based on these equations asopposed to attempting to read dst: directly from thecurves themselves. This step alone wI].]eliminate asignificant source of error. A computer programusing these coefficients will eliminate most calcu-lation errnra.A second main source of potential error ia theactual performance of the equipment installed ?-nthe

1.-.



.well as opposed to the published curves. With the lations. In an effort to validate the approach,advent of API standards on pump performance, there power meters were connected to thirty-five wellscan be much more confidence that new equipment will during 1987 in fields located in West Texas,perform (within specified limits) to the published California, Wyoming and Oklahoma including a widecurves. Specific test data on the pump to be range of downhole conditions, fluid properties,installed will increase calculation accuracy. Motor production requirements, and equipment from threeand cable performance are areaa that need to be vendors. A summary of the results is shown inaddressed by API to assure similar accuracy and Figure 5.industry understanding of tolerances.

}s shown, the range in error was from a 21.0%The Engineer should also keep in mind that any part overprediction of power cost to an 8.6% under-of the equipment system whether it is the pump, the prediction. The total average error was 0.8%.motor, or the cable will change in performance For twenty-seven of the wells (77.1%), the error waacharacteristics over time through use, at a rate less than 7%. This sample tends to indicate thatdependent on downhole conditions. Therefore, the method is accurate within +/- 7% more than threeinstallations with u,;edequipment will vary from times out of four. Cleari.y,many of the potentialpredicted levels. sources of error described above are either small orcompensating. Operating costs for ESP installationsInaccuracies i.nthe well data used in calculation can be approximated sufficiently to be included inwill directly impact performance. Specific gravity equipment selectfon and the economic valuation ofis a direct multiplier to develop horsepower load. proposed installations.well temperature will. impact cable resistance.Errors in calculating the required TDH will have a Economicsmajor impact. Wherever possible these parametersshould be double checked. In determining the economics of any operation, theproblem is one of trying to represent two differentAl.].ump performance curres are published for fluid tvpes of expenditures; initial outlays, whichwf.tha viscosity of 1.0 Cp that contains no free include purchase and installation costs, and period-gas. Gas intcrferenc~, fluid compression and ~c costs which will occur during the operating lifevj.scosityeffects will all cause deviations from of the equipment. Both represent real expenditures,predicted results. however, simply totaling the periodic costs and

adding them to the initial costs does not take intoIn the same light, pump performance is based on account the time value of money and results in anfluid produced at the pump, not on the surface. inaccurate picture. For an accurate comparison, itFailure to account for formation volume factor and is necessary to either adjust the periodic costsother changes in fluid characteristics will affect with respect to the time value of money beforepreducted performance. The method assumes that the adding them to initial costs or similarly adjust thesystem will operate continuously for the period. initial cost and distribute it over the expectedCyclical.operation will add to the errora. Since life of the equipment. This is accomplished bythe TDH required changee until the well is sta- using ~e present value of an annuity factorbilized, results only apply to a well once it has (PVIFa) which is defined as follows;reached this point. Adjustments for these vari- PVIFa = (l-(l+i)n) /i . . . . . . . (20)nhles are topics for advanced applications desiRnand beyond the scope of this paper. Where: i = interest rate for the intervaln = number of intervals (months) in theThe method assumes that nameplate voltage is applied equipment lifeequally to all three phases. As the voltage varieafrom nameplate results will be significantly affect- To determine the total.present cost of a system, theed. Adjustment for voltage variation ir.~olvesvery PVIFa factor Ss multiplied by the interval cost ofdetailed knowledge of the specific motor perfor- op~ration and added to the initial equipment pur-mance. The manufacturer should be consulted for chase and installatf.oncost,assistance in determining motor performance whenthis condition exists. Also, if there is a phase Total Present Cost = Initial Cost + (PVIFa ximbalance in the power supplied to the unit, accura- Period Cost) . . . . . . . . . . . ..f21)CY ~f Power cost predicting W~ll suffer. Projects with unequal initial and periodic costs canFinally, a 7.5% loss for switchboard and transformer be accurately compared using total present cost. Inefficiencies has heen assumed. This iS a good the case of ESP installations, the system thatnumber as a rule of thumb, but ia ~ot accurate for provides the lowest total present cost will be theall installations. It is desirable to ~ither best alternative, assuming equal production.compare well t.aadpower requirements and eliminatethis variable or to obtain specific surface equip- Another approach to the same problem is to amortizement efficiencies from the manufacturer. the initial purchase and inste.llationcost for aproject out in monthly amounts over the eypectedl.TETHOflAI.TDATION operating life, resulting in a total.monthly equiva-

lent expense (TME) when added to monthly operatingLooking at al.].of these qualifications, it would Costs. The factor for amortizing initial expenseseem that power cost predict.fonwith any degree of over operating life is sometimes called the capitalcertainty fa impractl.caland that the method de- recovery factor (cRF).scribed above would only be useful in eva].uatingtheorcttcal differences between nroposed instal- CRF= 1 / PVIFa = i / (1 - (I+i)-n). . . (22)



R PREDICTING POWER COST AND ITS ROLE IN ESP ECONOMICS SPE 17522..-. .. .. .-.. .. -..- The total equivalent monthly cost of a project would for optimizing equipment selection as opposed tobe the CRF times the ~.nitialinvestment plus the ueing rul.eeof thumb (ROT) selection. The samemonthly operating cost; concept holds for pumpe and motors. In the se-lection of pumps, it is common practice in some

TME = (CRF x Initial Cost) + Operating locations to size the pump at the extreme right ofcost. . . . . . . . . . . . . . . . (23) the operating range in the belief that this will

increase the life of the unit. another practiceBoth methods use four factors to determine cost; the that is sometimes ueed is to oversize the motors asinitial investment cost including purchase and much as 20%, also in the belief that this willinstallation, the operating cost or power consumed increase the unit life. Such practices are often the$y the equipment during operation, the life expec- result of experience in a particular field andtancy of the equ:.pment,and the cost of money or the should not be lightly disregarded. However, theseinterest rate for the duration of the investment. uractices are sometimee the reeults of the opera-Of these four factors, the Engineer aeleuting the cional grapevine and may have no validity for theequipment hss the least control over the interest specific situation being evaluated.rate. For comparison, the interest rate can beassumed constant and equal to Jell established Figure 8 is presented to show the impact of incor-rates, such as the interest rate for treasury bills. rectly applied rules of thumb on the economics ofoperation. In Figure 11, a 5000 foot well producingJ.ifeexpectancy of the equipment has a major impact 2400 BPD has been sized with two different units.on system economics. It is greatly dependent on One is sized with the pump close to the right hadthe specific well conditions. It can usually be limit of the operation range, the motor at 10%estimated by the Engineer based on past experience oversize, and a cable selected for a 38.2 voltagewith equipment from the same vendor ex?osed to drop per 1000 ft. The second unit has been sizedsimilar well conditions. with the pump and motor close to optimized efficien-

cy and an optimized cable. The curve represents thePurchase coet depends on the equipment selected and point in months of operation at which the totalis available from the manufacturer. Installation equivalent monthly costs for the two systems arecosts can usually be estimated with a high degree of equal. The curve indicates that for an expectedaccuracy by the Engineer. life of 12 months for the rule of thumb unit, the

optimized unit would only have to run 8 1/2 monthslheoperating cost or cost of power consumed by the to be an equal economic alternative.equipment has historically been one of the mostdifficuit for the Engineer to establish in advance This representation is somewhat exaggerated in thatwith any degree.of accuracy. This paper has pre- ~t ignores pulling costs snd lost production due tosented a method for establishing this figure with a downtime and in that it makes no effort to take intofair degree of accuracy. account salvage value of the failed equipment.

However, it very clearly indicates that applicationsEconomic Perspective design by rule of thumb can be a very expensive

habit and that power cost is a major factor in ESPTo put operating cost in the proper perspective economics.relative to the economics of ESP operations, Figure6 shows the total monthly equivalent cost as defined Conclusionin Eq. 23 for three different units sized for thesame well at 6, 12, and 24 months assumed life. The This paper has presented a method for calculatingwell produces 3500 BPD and requires approximately500 feet TDH.

power cost and overall economics for artificial.liftThe TM? attributable to initial and with Electric Submersible Pumps.j~stallation cost varies significantly depending onthe projected operating life, decreasing as life Since the method uses only published equipmentexpectancy increases and indicating that these performance data, established principles of Engi-factors decrease j.nimportance as expected life neerin.gand routinely available well parameters, itincreases. application to specific situations is straight-forward.Figure 7 represents the ratio of power cost toamortized initial cost as a function of life expec- A field study over a wide varietv of well and fluidtancy for unit B from Fig. 6. At approximately conditions has indicated the method can be used withfive months operation, power cost is equal in impact an average accuracy of 0.8%to initial cost for thi~ example, increasing to fourtimes as significant at slightly over 22 months The economic analysis has demonstrated that theexpected life. Of course, as expected life ap- power cost of an ESP installation can only heprnaches zero, power cost decreases in significance. ignored if the expected life is exceedingly short orThis indicates that power costs can he tgnored only the cost incurrml in replacement are extremelv high.if the projertcd life of the equipment is veryshort. The economic analysis has also indicated that the

run life of an overdesigned unit must be substan-In order to achieve the most economjc installation tiallv lon~er than that of an optimized unit toit is necesssry to optimize the selection of equip- justify the investment.ment, Two papers ha eJ .ande,j~~r;~e~~~t~~t~{%~~~~~~~leubject; , It should be noted that for wells with high oil

selection and M, on the optimization of cuts, emulsion, viscosity, or gas problems, cor-tubing and cable. Both of these papers make a case rectinns for the performance of the pump and tubingmust he applied.



Reference~:1. Shepler, R. P.: Applications Training Manual,

Oil Dynamics, Inc., Tulsa (19S7)2, API RF lIU: 11~1 Reco~ended Practice orSizing & Selection of Electrical Submersible

Pumps, First Edition, June 20, 1984.3. Brown, K. E., et al: The Technology ofArtificial Lift Methods, Penwell Publishing

co., Tulea, OK (1977)4. Newman, D. G.: Engineering Economic Ans.lysis,1980 Engineering Press, Inc.5.. Vandevier, J. E.: Optimum Power Cable Sizingfor Electrical Submersible Pumps, presented at

the 1987 SPE Production Operations Symposium,Oklahoma City, OK Mar 8-10, 1987, Paper 15195

6. Powers, M. L.: Economic Considerations forSizing Tubing & Power Cable for ElectricalSubmersf.blePumps, presented at the SPE 61stAnnual Technical Conference & Exhibition, NewOrleans, LA Ott 5-8, 1986 Paper 15423.

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SPE 17522 RON PANKRATZ AND BROWN LYLE WILSON 7

A4U5



2 S STA6 E P EWWSW4XFIW IMTI-S1A2+EST

ISJRIES SS ltWl 3500 I

o 400 I?410 Ed 1604 S&o 2400 hoBARRELS PER DAY (42 U . S . GALLONS)

40 60 120 iio 200 240 2io Si o sixCUBIC METERS PER OAY

R14 0.0,1, PUMP FOR 5 1/2 CASING

FIG. 2

MOTOR COMPOSITECHARACTERISTIC CURVE70 SERIES (Sotlz)

400 440

RPM

3000

36003400

3300

60 76% 100s 126%

A:P.SFASFL. AMPS

140 4

120%

ioo%

80%

60%

PERCENTFULL LOAO



m w

FIG.4

PoLYPROPYLENE, ROUND EPDM, ROUNDRzo x Rm x

AWG COND. 11/1000fl/1000 AWG COND. 0/1000 11110006 1 Solid 0.41I 0.037 6 1 Solid 0,411 0,1394 I :.lid 0.2S9 0.037 4 1 Solid 0.259 0.0?64 7 Sfrand 0.263 0.03s 4 7 Strand 0,263 o,03b2 7 Strand 0.165 0.(333 2 1 Solid 0.162 0.034I 7 Strand 0.131 0,032 2 7 Strand 0,165 0,0351 7 Strand 0.131 0.033

EQUIPMENT191sTRA22, 120HP2280V125STS(20.150HP 2250V76S3203sT100sT284sT11osT50ST90ST83ST65ST164STS3ST72ST273ST89ST241ST330sTS5ST59ST60ST202sT114STlsIsT234ST45ST95ST201sT107ST122ST74ST162ST172ST223ST

59ST GN3iO0, 100HP 10701K-20, 90HP 1165VDN450, 30HP 1215VK34, 180HP, 1365VD550, 50HP 955VD1350, 50HP 725VK16. 50HP 750VGN3iO0, 130 HP 9251GN25U0, 100HP 835VK28, 100HP 1200VX34, 125HP 21SOVG31OO, 120HP 1295VK20, 75HP 1160VDN1750, 120HP 21651K70, 85HP 1270VR-14, 90HP 1290VD1350, 120HP 2245VRB12 , 30HP 725VG2000, 50HP 725VK20, 75HP 1160VD1350, 60HP 97oVD950, 30HP 71OV142B, 60HP 1570VG48, 85HP 1270VK16, 50HP 1200VDN1OOO, 30HP 71OV269, 100HP 1150VRA16, 50HP 750VY62B; 125HP 1125VR14 . 30HP 1200VKA1OO, 125HP 2770VR9, 50HP 975VRB12, 901iP 2070V

FIG, 5

lDH

5527713720893637&36545794991119630313563367.s2957161531233354444130265642689326932615113836402478715055>:.24082567408325284016190287364777528C

FLOW

1440131533462150367>80063618711185300021503200417732002227188527971587128082714143274148585515001224154072021001694254o142025449801350

TOTAL A407

PRSD204

99.2118.2982.375.923.4186.556.137.643.1134.794.692.0112.4114.779.696.7989.4105.0104.826.149.064.264.025.154.961.9940.525.898.548.1131.6428.8102.449.075.78

ACTKw

82.098.575.069.621.5.73.753.035.541.1.29.091.389.0L09.0111.378,095.5889.0105.0105.026.550.366.066.025.957.0.?5.1742.327.0L03.551.3L40.5431.0L12.O54.084.59

RAGE ERRoR



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