11.. _ .-- -

Thermal heavy-oil recovery projects succeed in Egypt, SyriaFig 1

Thermal processesThe world contains about 10 trillion

bbl of heavy oil resources." Egypt hasabout 3 billion bbl of heavy oil in placewith about 40% in the Eastern desert,3% in the Western desert, 18% in Sinai,and 39% in the Gulf of Suez.!"

The recovery factors for the world'sheavy oil vary from a fraction of a per·cent to 80%, depending on the oil andthe reservoir characteristics. as well as

These methods extract remainingoil through increasing oil mobility byreducing oil viscosity, reducing watermobility by increasing water viscosity,or reducing capillary forces by reducinginterfacial tension between the displac­ing fluid and oil.

Thermal methods are usually suitablefor high viscosity oils, while chemicalmethods are mostly for low to mediumviscosity oils.

Remaining oil saturation is perhapsthe most critical criterion in selectingthe EOR method. The choice also de­pends on such considerations as depth,oil viscosity, etc."Thermal EOR methodsare often the best for recovering heavyoil. Thermal methods provide a drivingforce and heat for reducing oil viscosityand improving its mobility.

Source: Reference 11

ISSARAN FORMATIONS

improving the recovery factor.• Studying the overall economy of

the proposed development plan.Development and depletion strate­

gies depend on the life-cycle of a reser­voir. In a new discovery. the plan needsto address how best to develop the field,including well spacing, well trajectory,well planning, configuration, stimula­tion operations, and recovery scheme.If the reservoir has been depleted byprimary means, the plan needs to inves­tigate secondary and tertiary recoveryschemes.?"

Secondary recovery typically involvesdirect oil displacement with injectedwater into the oil zone or gas injectiongas from above the oil zone.

Waterflooding has generated bil­lions of barrels of additional oil. It isinexpensive and Simple to use, but thedisplacement and sweep efficiencies arelow. Additional recovery with secondaryrecovery methods average 3-10% of theoil-In-place.'

Substantial oil, as much as 60% ofthe initial oil in place, may remain aftersecondary recovery because of capillaryforces, interfacial tensions, and partialreservoir sweep by injected fluids. Thisremaining oil is the target for enhancedoil recovery methods.

Enhanced oil recoveryOperators are focusing on rede­

veloping and improving oil recoveryfrom existing oil reservoirs because ofincreased exploration costs for new oilfields, higher oil prices, and limited op­portunity for discovering major high­quality oil reserves.

The general approach for developingan oil field includes:1-3

• Collecting, evaluating, and analyz­ing geological, reservoir and produc­tion data if available.

• Estimating reserves and determin­ing the location of remaining oil.

• Selecting proper techniques for thedevelopment plan such as drilling newwells, performing stimulation works,applying secondary or tertiary recoverymethods.

• Selecting the best technique for

To increase oil recovery from exist­ing fields, operators in both Egypt andSyria have started producing heavy oilwith thermal enhanced oil recoveryprocesses.

In Egypt's Issaran oil field, cyclic­steam stimulation has increased oilproduction to 4,000 bid from 50 bidunder primary recovery.

In Syria's Oudeh and Tishrine oilfields, pilot cyclic-steam stimulationhas increased production to about 850bid from 550 bid in Oudeh and about2,500 bld from 7SO bid in Tishrine.Each field's pilot has five 25-MMbtusteam generators. The pilots include 14wells in Oudeh and 23 wells in Tishrine.

Mahmoud Abu ElElaWorleyParsons-EgyptCairo

Helmy SayyouhSayed ElTayebCairo UniversityCairo

Mohamed SamirScimitar Production Egypt Ltd.Cairo

40 Oil & Gas Journal ! Dec. 22, 200/1

Fig Z

Mar. 9

II

Jan. 18Nov. 29

waterflooding because heat losses insurface lines . wellbore, and formationare greater than the heat losses in theother thermal processes. The heat lossesreduce the processes effectiveness in

OCI. 10

I':

Aug. 21

- Actual cumulative oil

- Actual cumulative water

- Predicted cumulative oil

- Predicted cumulative water

61=~:(iI_.__._.-=-.-.May 13 July 2

Source: Reference 11

10

25:c.0ooo. 20

C.gc-5 15o0.

WElL CSS 1PERFORMANCE,UPPER DOLOMITE30-r-- - - - - - - - - - - - - - - - - - - - - - - - - ---.

rocks can consume a large proportionof the injected heat . Oil recovery factorsin California with steam injection areabout 55% of the initial oil in place."

Operators seldom employ hot

the technique used . Heavy oil viscositiesvary from 100 to 1,000 cp at reservoirtemperature. Heavy crudes typically alsocontain 3 wt % or more sulfur. 10-30%asphaltenes, and as much as 2,000 ppmof vanadium compounds."

Cyclic-steam stimulation is one ofthe most common thermal processesin use. It involves injecting steam andthen producing oil for the same well. Itis considered an economic oil recoverymethod that costs about $20/bbl of oilrecovered.

Oil recovery factors for cyclic-steamin Cold Lake,Alta., are more than 25%,while in Venezuela recoveries as high as40% have been noted."

Continuous steamflooding, muchlike waterflooding, is a pattern drive,with arrays of injection and produc­tion wells. In this case, the recoveryfactor largely depends on the patternsize, since heat loss to the surrounding

• Slicld ne•Snu~WoI1<.oYer

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••

fig 3

•

•

••

•

••

•

•

••

••

primary recovery.The field is 290

km southeast ofCairo and 3 kminland from thewestern shoreof the Gulf ofSuez.The Issaranconcession has20,000 acres.General PetroleumCorp. (GPC) Egyptand Scimitar Pro­duction Egypt Ltd.started developingthe field in 1999 .

As of October2007, Scimitar haddrilled 120 wellson the concession

The majorheavy-oil ac­cumulations are

within shallow Miocene dolomites andlimestones (Upper dolomite, Lowerdolomite, and Gharandal and Nukhullimestones), and sandstones (Zeit). FigI shows the formations present.

The formations contain an oil with agravity of 10-12°.

In 2003, Scimitar initiated a res-

•

•

•

Issaran oil fieldA cost-effective development plan

with cyclic-steam injection allowedScimitar Production Egypt Ltd. toimprove oil recovery from the Issaranoil field. II With the process, productionrates increased to +,000 bold No­vember 2007 up from 50 bold under

• •t •

• • •• •• • •• ••• ••I •• •"2 •Green - 2006 •., •Yellow - 2007 •• •Blue - 2008 ... ••

~ •Source:Reference 11

STEAM PILOTS

decreasing oil viscosity.In situ combustion oxidizes a por­

tion, about 10%, of the in-place-oil togenerate heat . As such, the process has ahigh thermal efficiency but this processrequires more control.

Fig 4

IHigh water cut

in all steam wells

Steam in CSS J10,11,15, and 16

Steam in CSS 10 and 16

Stop injection in CSS 15...,and 16, and upsize CSS 46 +

CSS 6, 8, and 9stop injection

Steam in CSS 6, 8, and 9

CSS 3,5, and 7[ on Prod::~::ce tubing pump

w ith progressivecavity pump in

CSS 12, 13, and 14

1

Steam in CSS 3, 5, and 7

500

1,000

4,500

4,000

3,500

~ 3,000.cc'0

2.500.~

::J

"0c': 2,000

1,500

STEAM WELL PRODUCTION5,000 -r--"T- - - - - - - - - - - - - - - -r-- - - -r-- - - - - - - - - - -r--"T- - - - - - -

Apr.

Source: Reference 11

May June Ju ly

2007

Aug . Sept. Oct. Nov

42 Oil & Cas Journal /Dec. 22, 200/1

ervoir engineering study to evaluateenhanced oil recovery (EaR) in theUpper Dolomite of Issaran oil field. Ittargeted the Upper Dolomite because ofits large orig inal oil in place (more than50% of the concession OOIP) and itslow estimated primary recovery of lessthan 1%.

In 2004, the company conducted asuccessful cyclic-steam stimulation pilotin well Issaran-44. Initial evaluationindicated that the oil recovery factorfrom this reservoir could reach 20%compared with about 1% under naturaldepletion. Fig. 2 compares the simu­lated and actual results that confirm thepilot's success.

Based on the pilot. the company de­cided to begin commercial production.Its redevelopment plan included threephases. Two phases finished in 2007and the third phase will be finalized in2008 .

The phases involve cyclic-steam

stimulation along with seven-spot wellpatterns (Fig 3). The distance betweenwell is 60 m.

Injection rates start at 1,000 bld ofcold-water equivalent and each cyclelasts for 50 days.

Fig. 4 shows the production of thesteamed wells. Production rate fluctu­ates because of changes in the steamcycles among wells and some problemsduring the project's start-up.

Syria fieldsTanganyika Oil Co. Ltd. has imple­

mented cyclic-steam pilots in two giantheavy oil fields, Oudeh and Tishrine, inSyria.'?

These fields are in northeast Syria(Fig. 5) . Oudeh and Tishrine have anarea of 47 ,500 and 101,000 acres,respectively. The accompanying tableshows the reservoir rock and fluid char­acteristics in these fields.

Development of these fields started

in 2004. Initially, a simple sector modelevaluated the feasibility of implement­ing steam injection in the fields.Themodel considered vertical and high ­angle wells.

This model indicated that steam in­jection would succeed . It showed goodresults for small 1O-acre or less drain ­age areas and recovery factors of aboutdouble of those for cold recovery.

Later, the operator used a moresophisticated sector model to design thepilot project in Oudeh and Tishrine. Theblack-oil model included a geocellularmodel for each formation that historymatched associated production andpressure data.

All prediction runs considered steaminjection at 350 0 C, 80% steam quality,1,260 bwld injection, and maximum2,030 psia wellhead pressure .Themodel's objectives were to :

• Estimate maximum steam injectionrates and corresponding heat loss down

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RocK. FLUID CHARACTERISTICS Table 1

Oudeh Tishrine Tishrine TishrineShiranish B ChilouA Chilou B Jaddala

Reservoir pressure, psia 2,000-2,300 1,337 1,337 1,337Hoservo.r temperature, "C. 48-50 43 45 45Average reservoir depth, m 1,600 950 1,070 1,070Reservoir gross thickness, rn 20-120 10-40 80-250 60-160Average porosity, % 20 27 24 25Average water saturation, % 23 40 48 50Average permeability, rnd 40-150 1-200 1-16 1-25Oil gravity, °API 8-18 13 11-19 13-20Solution GaR, sct/stb 150-300 100-150 100-150 100-150Bubblepo.nt pressure, psra 2,000-2,300 470-600 470-600 470-600Oil formation volume factor, rb/stb 1.11-1 .17 1.05-115 1.05-1.15 1.05-1.15Oil viscosity, cp 40-3,000 800-1,800 100-1,500 100-15,000Asphaltene content, wt % 10-20 12-16 12-22 12-24Wax content, wt % 5-10 3-6 10-26 2-24

ReferencesI . Bahadagli, T., "Mature Field

Dcvclopmcut-e--A Review," Paper No.SPE 93884, SPE European/EAGE AnnualConference, Madrid.Tunc, 13-16,2005 .

2. Abu EI Ela, M., "Integrated ap­proach recommends redevelopmentplan," OGJ, A.ug. 7, 200 6, p. 55 .

3. Abu HI Ela, M., " Data Anal ysisMethodology for Reservoir Manage­ment," Paper No, SPE 106899, SPEEUROPEC/EAGE Annual Conference andExhibition, London, June 11-14, 2007 .

4 . Raza, S.H ., "Data Acquisition andAnalYSIS for Efficient Reservoir Manage­ment," JPT, April 1992.

5. Wiggins, M.L., and Startzman,R.A., "An Approach to Reservoir Man­agement," Paper No. SPE 20747, SPEATCE, New Orleans, Sept . 23-26, 1990.

6, Satter, Abdus, et al., "IntegratedReservoir Management" Paper No. SPI,22350, SPE International Meeting onPetroleum Engineering, Beijing, Mar.24-27, 1992 .

7. Abu El Ela, M., and Mahgoub, I. ,"Waterflood boosts oil production fr0111

field in Egypt," OGJ, Jan . 7, 2008, p . 4- 3.

AcknowledgmentThe authors thank the Financial,

Development and Investment (FDI)Holding Co. for contributing to the sci­entitl e research at Cairo University, andto Scimitar Production Egypt Ltd. forpermission to publish this article . •

wells in Tishrine. Initially, the operatorinjected s team through the annulus intill' first 3 wells of each pilot. Now, allinjection goes through vacuum insu­lated tuhing.

Figs. 6 and 7 show the performanceof th e pilots.

In Jun e 2008, the cyclic steam injec­tlOII increased production to 850 bidfrom about 550 bblld in Oudeh andto 2 , SOO bid from about 750 bblld inTishrine. Lack of steam injection fromFebruar>' to September 2007 affectedOudch production.

Th e steam/oil ratio in this pilotrang es from I in the very good wells to

20 in th e poorer wells ,

50

. .I~"-',

IRAQ

@ Oil-gas fields

- Pipeline

kmo

Fig 5

started preparation for the initial pilotplan for cyclic steam stimulation. Thispilot placed a 25-MMbtu steam genera­tor in each field and involved two wellsin each field .Th e pilot alternated steaminjection and production between thetwo wells.

Steam injection started in Oudehin September 2006 and in Tishrinein October 2006 . After 4 months ofoperation in Oudeh, steam injectionhad to stop for 8 months (February toSeptember 2007) due to excess H,S inthe fuel gas . •

The pilot projects have expandedwith time. Curreruly, they involve five25-MMbnl steam generators in eachfield and 14 wells in Oudeh and 23

SYRIA

/ . .- "-""""""-".' AI Oarnishli •

,/.'

/

the well bore.• Optimize steam slug size, injection

period, and soak time.• Predict production rates and pro­

duction cycle length.• Estimate the optimal well spacing

for cyclic steam injection.• Evaluate the use of horizontal or

vertical wells in steamflooding.• Evaluate the effect of horizontal

well length.Key results indicated a recovery

factor of at least double because of thesteam, 30-40 days injection cycle yield­ing the highest recovery factor, 1-3 dayssoak period, and 120-day productioncycle.

By yearend 2005, the company

Oudeh

TURKEY

OUDEH. TISHRINE OIL FiElDS

4

r------, Sayed EI-To eb (sayed_dtay b62 hotmail.com) is(I professor in the petroleumengineering deportment, CairoUniversity and also works asa professor within the PPECGroup. Cairo Uni\'ersity.Since1998. hehas been a consultantengineer in petroleum nun ir

engineering and enhanced oil recovery. £1-Tayebholds a BSc and MSc in petroleum engineeringfrom Cairo Unh'ersity and a PhD from la bora­tories des Sciences du Genie Chimique. ENSIC• an . Unil rsity. Fmnce, He isa member of theEgyptian Engineers Syndicate and SPE.

Helmy Sayyouh (sll)'YOuhgmail.com) isa professor inthe petroleum engineering de­partment, Cairo University andalso works asa professor I~; thinPPEC Group, Cairo University.Since 1986, hehas been a con­sultant engineer in petroleumreserroi r engineering. enhancedoil recovery. reservoir simulation. and naturol gasengineering.Sayyouh has a BSc and an MS inpetroleum engineering from Cairo Univcrsity and(I PhD from Penn Stale Unilersity. Sayyouh isamember of the Egyptian Engineers Syndimre, SPE.and theNewYork Academy ofScien e.

Mohamed Samir (msamirscimltarcgypl.com) is wi thScimitar Production Egyptlid. He pm'iously worked forPetrobd in Egypt and AD 0in Abu Dhabi. Samir holds aBSc in petroleum engineeringfrom Sua Canal Unh-ersityand an MSc and a PhD from

Cairo Unjversity. Heisa member of theEgyptianEngineers Syndicate and SPE.

The authorsMahmoud Abu EI Ela (mah­moud.abueleJa@worleyparsons.com) is a lead process engineeratWorleyParsons EngineersEgypt LId., and works also asanassistanI professor withinthe Petroleum and Petrochemi­cals Enginuring Consul-tents (PPEC) Group. CairoUniversity, Hepreviously was an assistanl prof~rin thepetroleum cngineering at Cairo Unil'ersJly.p troleum process consulting mginro for Rha/doPetroleum Co.•and a research engineer atWoodsideResearch Foundation. urtin University ofTechno1­ogy, Ausuulia.Abu EI £10 holds a BSc and an MScin petroleum engin aing from Cairo University,and a PhD from Curtin University ofTechnol-ogy. Heisa member of theEgyptian EngineersSyndicate and SPE.

Fig 7

Fig 6

II;"

Cairo, May 2007 .11. Samir, M., "First Successful

Steam Injection Project in Egypt," lORW rk h p. harm El Shaikh. Egypt. June16 I .2008.

I2 Rahoma, A.. "Syria Carbonatet 11 Pro] cts and Experience," lOR

rk hop, harm EI Shaikh, Egypt, June16-19,2008.

Iii

- Expected hot

- Actual cold with decline

- Actual hot

o••••••••~• • • ~.

2,500

500

2.000

~co.~ 1,500"0ec.

o1.000

800"0:cc0.~

600Steam injection

:l suspended due"0e to gas supplyc.

0400

200

TISHRINE FIELD PERFORMANCE3,000 ..,....- - - - - - --- - - - - - - - - - - - - - - - ,

- Actual cold with decline

June Aug. Oc Dec. Feb. Apr. June Aug . Oct. Dec. Feb. Apr. June Aug.

- Expected hot

1,000 - Actual hot

0••• •••••• •••••

DUDEH FIELD PERFORMANCE1 ,200~------------------------...,

8. Donaldson, E.C., et al., EnhancedOil Recovery: Fundamentals and Analy­sis, New York: Elsevier Science Publish­ing Co. Inc., 1985.

9. Farouq Ali. SA, t al., PracticalHeavy Oil Re ov ry. draft v lume, 1997 .

10. Oil P tential in Egypt: Srati ticAnalysi • EGPC. SLXID 1i chnology

Transfer Workshop, SPE Egypt Section,

Oil & GasJournal/Dec. ZZ, Z008 45