the magazine for pump users worldwidethe magazine for … papers/downhole pump... · 2020. 9....

May 2004The Magazine For Pump Users Worldwide May 2004The Magazine For Pump Users Worldwide

wood group reprint 1-8 5/25/04 8:34 AM

Reprinted from the May 2004 issue of PUMPS & SYSTEMS22

sed in a variety of petroleum and industrial applica-

tions, electric submersible pump (ESP) systems are

now providing specific solutions to a wide range of

surface fluid-movement applications. Once relegated

to downhole operations only, ESP technology has

moved on up to find its place in the sun.

The Downhole ConnectionIn the oil and gas industry, ESP units are the fastest-growing pumping technology, and are often

considered the high-volume and depth champion among artificial lift systems. On a cost-per-barrelbasis, they’re considered to be both economical and efficient. An ESP requires very little surface space,is well- suited for offshore applications and works well in both highly deviated and vertical wells.

ESP systems incorporate an electric motor and multistage centrifugal pump unit (Figure 1) runon a production string and connected back to the surface control mechanism and transformer via anelectric power cable. When other lift systems seem to be over-matched by heavy columns of oil, orwhen large volumes of water are needed to be pumped-off a well to free gas production, the ESP isusually the system of choice.

U

The well test service vessel Toisa Pisces is shown prior to com-missioning in the Gulf of Mexico. Installed on a lower deck (seeinset) are four SPS units from Wood Group ESP. Each of them israted for 1000 HP. Two are used for water injection (foreground)and two for crude oil transfer (far background)


By nature, these rugged downhole sys-tems are required to work in hostile envi-ronments. Wells deeper than 12,000 ft.can be produced efficiently with thesepumps, which can be used in casing assmall as 4.5” outside diameter. Productionrates range from 2 to 2000 GPM (70 to64,000 BFPD), and variable-speed drivesadd pump rate flexibility. Modified equip-ment and special features allow sand andabrasive particles to be pumped withoutadverse effects.

Multistage centrifugal pumps consistof stages with rotating impellers and sta-tionary diffusers cast from a Ni-resisthigh-nickel iron containing destruction-resistant properties. For severe environ-ments, optional tungsten carbide radiallystabilized and corrosion-resistant pumpmaterials, including various stage coatingsand boron diffusion hardening processes,are available. The impeller is mounted ona shaft made of either Nitronic 50 or otherhigh-strength corrosion-resistant nickel-based alloy or stainless steel.

3

Greg Dover, Denbury Resources, Inc., Gabriel Delgado-Saldivar, Maritima de Ecologia S.A. de C.V., and Neil Ferrier, Wood Group ESP, Inc.

Discovering multiple surface applications for multistage centrifugal electric submersibles. . .

Daylight Shines OnDownhole PumpTechnology

The SPS AlternativeBuilding on rugged oilfield ESP tech-

nology, the SPS™ Surface Pumping Systemfrom Wood Group ESP has developed a rep-utation as a low-maintenance, cost-effec-tive alternative to vertical turbine, split-caseand positive displacement units. These sys-tems feature a direct-drive, multistage cen-trifugal design ideally suited for most high-pressure, high-volume and environmentallysensitive applications.

Offering a low surface profile coupledwith quiet vibration-free operation, the SPSunit is available in electric, gas or dieselpowered versions. These systems can typi-cally handle up to 2,000 GPM (64,000BFPD) and discharge pressures ranging upto 6,000 PSI. This versatile and reliablepumping system features design flexibilitythat facilitates onsite installation and main-tenance with minimal site preparation.

Figure 1. A mixed-flow, multistage centrifugal pump


Reprinted from the May 2004 issue of PUMPS & SYSTEMS Magazine

Due to limited well-casingdiameters, the lift or head devel-oped by an individual stage is rel-atively low. This requires stagesto be stacked together to meetthe lift requirements for variousapplications. At each stage, therotating impeller adds velocity tothe fluid stream by centrifugalforce and tangential redirectionat the impeller outside diameter.The stationary diffuser convertsthis high-velocity energy to pres-sure as it redirects the flow to thenext impeller. Diffusers also act asa bearing surface, providing addi-tional stability to the pump shaft.

On the SurfaceThe petroleum industry has

historically used positive dis-placement (PD) reciprocatingpumps for a wide range of sur-face fluid-handling applications.With higher flow rates, somecompanies have also employedcentrifugal split-case (S-C) pumps.

In recent years, pressure toreduce initial capital expenditures,coupled with the desire to lowerever-increasing maintenance costsand reduce environmental impact,has encouraged the industry toevaluate alternative fluid handlingtechnologies including the WoodGroup’s SPS technology.

The SPS unit incorporatesthe same high-efficiency pumpsthat have been used for decadesin downhole applications. Forover 15 years, it has been utilizedas a cost-effective and reliablesolution in the petroleum indus-try for produced water injectionapplications. More recently, the

SPS product line has beenexpanded to handle higher andlower flow rates and pressures,with different material anddesign configurations to matchan increasingly diverse installa-tion base. As a result of successfulapplication in new markets, theseunits have become a popular

alternative for many serviceswhere plunger (triplex, quin-tiplex), split-case centrifugal orvertical turbine pumps (VTP)were previously employed.

SelectionWhen design consultants

and facilities engineers evaluatevarious pumping technologiesfor specific applications, numer-ous considerations come intoplay. Among the most importantare initial and life cycle costs,including maintenance require-

ments, environmental impact,efficiency and the ability/flexibil-ity for changing duty conditionswith minimal investment.

Table 1 provides a compari-son of surface pumping systemsto both positive displacementreciprocating and centrifugalsplit-case pumps. While some ofthe issues listed impact initialdesign considerations, othersprovide a comparison of long-term operational differences.

Making a Case forthe Technology

Over the last few years, thissurface pumping system technologyhas proven to be an effective alter-native in numerous fluid-handlingapplications in petroleum, miningand other industrial operations. Inpetroleum, for example, it’s beenemployed for the following:

■ Produced water injection

■ Produced water disposal

■ Waterflood injection

■ Pipeline booster

■ CO2 flood injection/

booster

■ Crude oil transfer

■ Cavern storage pumps

■ LPG/NGL/Amine gas services

■ Condensate transfer

■ FPSO fluid handling

■ Power fluid pumps for

downhole jet/piston pumps

Here are some examples of thetechnology’s versatility:

4

A large percent-

age of problem

pumps are sim-

ply oversized—

leading to unreli-

able, and ineffi-

cient operation.


Reprinted from the May 2004 issue of PUMPS & SYSTEMS Magazine 5

Gas Processing/Amine Service Liquid amine, a derivative of

ammonia, is used in the gas-sweetening process. Acidic gases,through a chemical reaction, areabsorbed and pumped through aseries of exchangers, towers andconcentrators. The amine solu-tion must be carried at certainpressures in order for the gassweetening to take place. Oncethe process has occurred, theamine solution is reclaimed andrecycled.

A Big Lake, TX operator, likemany others, has historically usedsmall PD pumps to move the liq-uid and to maintain pressures ingas plant amine applications. Theoperator found the PDs costly tooperate, as they:■ consistently leaked expensive

amine, which required costlyremediation;

■ required constant modifica-tion to meet changing plantand process conditions;

■ were prone to vibration,causing piping fatigue;

■ cost between $500 and$1,500/month to maintainand required excessive atten-tion from maintenancecrews; and

■ required extra capital toinstall 100-percent backup inan attempt to eliminate plantdowntime (increasing pumpavailability, but also boostingmaintenance expenses).

In a field test, the operatorreplaced a small PD pump withan SPS unit rated for 20-75 HP

(Figure 2). At the end of the firstfive months of service, the opera-tor determined that the SPS unitprovided comparable efficiencieswhile eliminating amine leakage,environmental issues, vibration,expensive maintenance hoursand costly modifications to meetnew plant and process condi-tions. Additionally, due to rou-

tine maintenance cost and lostproduct inherent with the PDpump, the purchase price of thenew surface pumping unit had apayout of less than one year.

This operator is in the pro-cess of replacing the small PDpumps in all of his gas plantswith SPS centrifugal pumps. Healso is considering replacing larg-

5

Table 1. SPS vs. other surface pumping technologies

Figure 2. SPS unit in service at a liquid amine facility


Reprinted from the May 2004 issue of PUMPS & SYSTEMS Magazine6

er PD pumps with larger SPSunits rated for 1000 HP.

CO2 Flood Project/PipelineBooster

A pipeline operator in Little Creek, MS, was using two 700 HP compressors rated for 32 MMCF/D on a tertiary CO2flooding project. Low productdensity reduced the ratings to 27 MMCF/D. The compressorswere expensive to purchase, com-plicated to install (requiringextensive site preparation), costlyto operate (with large powerrequirements), maintenance in-tensive (resulting in loss of CO2injection during downtime), andvery large and noisy.

Engineers from WoodGroup ESP worked with thiscustomer to design a surfacepumping system to replace thetraditional compressor package.They developed an innovativetechnology using reliable rotat-ing-shaft seals for this high-pres-sure, multiphase, non-lubricatingenvironment. Extensive analysiswas performed for all compo-nents exposed to CO2.

As a result, permanent, self-lubricating shaft bearing andbushing surfaces were employedthroughout the pump assembly.Minor modifications to theplumbing system in the facilitywere made to ensure dense phaseliquid was being delivered to thepump.

The SPS unit (Figure 3) wasinstalled and operated for a peri-od of six months and was thendismantled to analyze and ensure

the integrity of all components.In this process, significant im-provements were noted.

■ It produced 26.7 MMCF/D

at 450 HP (22 MMCF/D at

60 Hz) compared to 700 HP

required for comparable

compressor volume—a 36-

percent reduction in HP

requirements.

■ The unit’s purchase price

was less than a three-month

rental of the compressor

package.

■ Maintenance requirements/

costs were eliminated.

■ Site preparation/pad was one

tenth the size of the compres-

sor pad.

■ Noise levels were dramatical-

ly reduced.

This operator needed tomove a large volume of CO2 athigh-intake and discharge pres-sures.

The SPS unit rated for 1000HP provided a smaller, quieter,more efficient solution, which inturn was easier to install, requiredless maintenance and was moreeconomical than the originalcompressor system.

Well test service vessel/injection and transfer pumps

This is the first known suc-cessful installation on a well testservice vessel, where four SPSunits (rated for 1000 HP) wereused to replace two PD pumpsfor water injection and two API

610 split-cased pumps for crudeoil transfer/export.

This system was installedDecember of 2003. The vessel,the Toisa Pisces, is currentlyoperating in the Gulf of Mexicofor PEMEX. Four additionalunits are being installed onBourbon Offshore Norway’sBourbon Opale, which will alsooperate for PEMEX following itsconversion. Maritima de Ecolo-gia S.A. de C.V. (Marecsa) hasbeen designing and supervisingthe construction and conversionof well test service vessels since1997, and specified the equip-ment to be installed on both vessels.

Delivery and installationtime played an important role inthe design and selection of thissystem. Depending on the com-plexity and conditions of service,SPS unit turnaround and imple-mentation is typically 12 weeksor less compared with API 610split-cased pump deliveries of26-52 weeks.

The reduction of extrainventory costs and the minimaldowntime also associated withthe SPS unit were important selection factors. Any systemdowntime in this application canequate to thousands of dollars inlost production.

Flexibility is the key to suc-cessful operation of well test ser-vice vessels. The SPS unit ismodular and can be easily retro-fitted to meet unique pumpingrequirements. In this case, thecustomer needed the two SPS

Circle 257 on Reader Service Card


Reprinted from the May 2004 issue of PUMPS & SYSTEMS Magazine 7

transfer pumps to run over awide operating range in terms ofpressure and flow, in order tofeed into various existing crudeoil pipelines. Similarly, on theinjection pumps, the various injection locations have differentpressure and flow requirements.

ConclusionIn many cases, SPS units

offer inherent advantages, such aslow NPSH, lack of pulsation,product containment, volumeand pressure flexibility and thelack of high-pressure packingglands that helps eliminate costlymaintenance repairs, nuisanceshutdowns, product leakage, pip-ing stresses and man-hour con-sumption.

These systems are flexibleand can be easily modified tohandle a variety of service require-ments. Design adjustments tosuch items as the seal assembly,elastomers and metallurgy areroutinely made to accommodatespecial applications.

Multistage centrifugal sur-face pumping systems may havecut their teeth in the petroleumindustry, but that’s not wherethey’ll stay. As design engineersand operators evaluate costs,maintenance requirements, envi-ronmental impact, efficiency andflexibility, they’re sure to find a

range of other applications—inmany other industries—wherethese multi-tasking high-achiev-ers can shine. P&S

Greg Dover is a petroleumengineer with Denbury Resources,Inc., of Plano, TX. He has over 20years of experience in the industryand has been working onDenbury's CO2 floods in south-western Mississippi since 1999. Amember of the Society of PetroleumEngineers, Dover holds a B.S. inPetroleum Engineering from theUniversity of Wyoming.

Gabriel Delgado-Saldivar isGeneral Director of Maritima deEcologia S.A. de C.V. (Marecsa).Mexico-based Marecsa has beendesigning and supervising the construction and conversion ofwell test service vessels since 1997.Delgado-Saldivar and his team ofengineers recently helped commis-sion the Toisa Pisces, which isowned by Toisa Shipping Ltd(USA/Greece) and operated bySealion Shipping (U.K.) forPEMEX in the Gulf of Mexico.

Neil Ferrier is Manager ofSurface Pumping Systems forWood Group ESP, Inc., inHouston, TX. A mechanical engi-neer with 27 years of experience inthe pump industry, he served hisapprenticeship with Weir Pumpsin Scotland. Later, he worked forMono Pumps Ltd, in Australia,the U.K. and the U.S. Ferrier is amember of the Society of PetroleumEngineers and is a U.S. Patentholder. He’s been with Wood GroupESP for four years.

For more information, log on to:

www.woodgroup-esp.com.

Figure 3. SPS unit installed at a CO2 flood project

To ensure reliable

bids, furnish a

detailed process

specification,

then confirm that

suppliers are

quoting a good fit

for the service.


Wood Group ESP, Inc.The Smart Choice™

www.woodgroup-esp.com

Our multi-stage centrifugalSurface Pumping System(SPS) provides a versatile,low-maintenance alterna-tive to many split-casecentrifugal, positive-dis-placement and vertical-turbine pump applications.The SPS is a cost-effectivesolution for petroleum,mining, processing, waterand other industries thatrequire high-pressuremovement of fluids. Provenbenefits include:•Lower initial and

whole-life cost•Short construction

lead time•Increased reliability

and runtime•Low noise and

vibration levels•Remote monitoring

and control•Worldwide supportWe’re committed to turn-ing your downtime costsinto runtime profits. Formore information, call 1-405-670-1431. Or [email protected] inquiries welcome.

BOOSTER•TRANSFER•CIRCULATION•INJECTION

AMINE PROCESSING FACILITY, CENTRAL TEXAS

Say goodbye to pumpmaintenance.Say hello to a bettersolution...SPS™.

Say goodbye to pumpmaintenance.Say hello to a bettersolution...SPS™.


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