Waterfooding and Simulation
Contents Abstract..................... ................................ ..................... ..................... ..................... ..................... ..................... ..................................... ........................... 3 1.0
Introduction.................... .............................. ..................... ..................... ..................... ...................... ................................. ...................... 4
2.0
Part A..................... ............................... ..................... ..................... ..................... ..................... ..................... ................................. ...................... 5
2.1
Reservoir eservoir simulatio simulation.... n........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ...... ..5 5
2.2
Principl Principle e o waterfo waterfooding. oding..... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ .......... .........6 ...6
2.3
Waterfoo aterfood d candidate candidates... s....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........... ............... ............... .............. ......... ..
2.4
!ptimum !ptimum waterfo waterfoodin oding.... g........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ............ ............... .............. ............... .......... .." "
2.5
Selectio Selection n o waterfood waterfood pattern. pattern..... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........... ..............1# .......1#
2.5.1 2.5.1
$rregula $rregularr in%ection in%ection pattern patterns.... s........ ........ ........ ........ ........ ........ .......... ............. .............. ............... ...............1# .......1#
2.5.2 2.5.2
Perip& Perip&eral eral in%ection in%ection patter patterns.. ns...... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........... ...............1# ........1#
2.5.3 2.5.3
Regular egular in%ection in%ection patterns... patterns....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ............ ..........11 ..11
2.5.4 2.5.4
'resta 'restall and (asal (asal in%ection in%ection pattern patterns.... s........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ......12 ..12
2.6
)stimatio )stimation n o o t&e overall overall waterfo waterfood od recove recover* r* e+cienc*.. e+cienc*......... ......................13 ...............13
2.6.1 2.6.1
,&e oil oil in place place at at t&e start start o t&e pro pro%ect.. %ect...... ........ ........ ........ ........ ........ .......... ............. .........13 ..13
2.6. 2.6.2 2
-isp -ispla lace ceme ment nt swee sweep p e+ci e+cien enc* c* )-...................................................13
2.6. 2.6.3 3
/rea /reall swee sweep p e+ci e+cien enc* c* ) /..................... ................................ ..................... ................................. .......................14 14
2.6. 2.6.4 4
0erti ertica call swee sweep p e+ci e+cien enc* c* ) 0.............................................................15
2.
'ase 'ase stud* Ro(ert Ro(ertson son ield..... ield......... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ..........16 ......16
2.
-iscussio -iscussion... n....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........... .............. .............1 ......1
3.0
Part B:.................... .............................. ..................... ..................... ..................... ...................... ..................... ..................... .................... ......... 1
3.1
Simulatio Simulation... n....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ .......... ............. ..............1 .......1
3.1.1 3.1.1
$nitial $nitial case.... case........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ .........1" .....1"
3.1.2 3.1.2
irst Strateg* Strateg* $nverte $nverted d nines ninespot pot pattern pattern.... ............ ............... .............. ............... .............2# .....2#
3.1.3 3.1.3
Second Second strateg* strateg* ives ivespot pot pattern. pattern..... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ .........21 .....21
3.2
Result.... esult........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ............ ............... .......... ... 22
3.3
-iscussio -iscussion... n....... ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........ ........... .............. .............24 ......24
4.0
Conclusion.................... .............................. ..................... ..................... ..................... ...................... ..................... ....................... .............25 25
5.0
Reference..................... ................................ ..................... ..................... ..................... ..................... .................................. ....................... 26
2
/(stract ,&e main aim o t&is report is to conduct a researc& in waterfooding process and to implement t&e undamentals o waterfooding process in reservoir simulation. Waterfooding is per&aps t&e most common tec&niue used so ar as a secondar* recover* mec&anism (ecause o t&e availa(ilit* o t&e water t&e low cost o water compared wit& ot&er fuids and t&e water can (e in%ected into t&e reservoir ormation easil*. ,&e principle o waterfooding is (rief* de7ned as t&e in%ection o water into t&e reservoir ormation to displace t&e oil and t&ereore ma8imi9e t&e oil production and increase t&e recover* actor. $n Part / a (rie introduction o reservoir simulation is present wit& t&e steps involved in simulation. ,&e principle o waterfooding and t&e actors w&ic& ma:e t&e reservoir a successul candidate or waterfooding pro%ect will (e discussed in Part /. ,&e critical point or a successul waterfooding pro%ect is determining t&e optimum time to start. ,&us t&ere are several aspects must (e considered to decide t&e optimum time. ,&ese aspects are also discussed (rief* in t&e part. urt&ermore t&e met&od o estimating t&e waterfooding recover* actor is descri(ed in detail wit& t&e e8pressions used. /t t&e end o t&is part a case stud* o Ro(ertson 7led is considered to e8amine and discuss t&e success o waterfooding in t&e 7eld. $n Part ; a simulation is perormed (* using Petrel )
3
1.0
Introduction
Reserve o an oil 7eld is de7ned as t&e uantities o t&e &*drocar(ons in a reservoir w&ic& are commerciall* recovera(le rom :nown accumulations and a given date (* various tec&niues. ,&e e8tracta(le amount o &*drocar(on is dominated (* a recover* actor w&ic& depends on man* varia(les suc& as t&e reservoir properties fuids properties reservoir drive mec&anisms etc. ,&e reservoir drive mec&anism reers to t&e natural energ* o t&e reservoir t&at moves t&e oil to t&e well(ore wit&out using an* additional supplements. ,&e natural drive mec&anisms li:e t&e gas cap drive and water drive are :nown as t&e primar* oil recover*. $n most cases onl* 5 to 3# > o t&e original oil in place !!$P can (e recovered (* t&e primar* oil recover*. ,&e insu+cient recovered oil in t&is mec&anism led to di=erent practices to support t&e neutral energ* o t&e reservoir (* in%ecting immisci(le gas or water into t&e reservoir ormation w&ic& is :nown as t&e secondar* oil recover*. ?p to 3# > additional recover* o t&e !!$P can (e recovered (* using t&e secondar* oil recover* tec&niue. $n some certain reservoirs a tertiar* oil recover* en&anced oil recover* )!R is reuired to recover t&e residual oil let (e&ind in t&e reservoir ater ine+cient primar* and secondar* recover* met&ods. ,&e use o t&e )!R met&ods is usuall* limited due to economic considerations. ,&e oil recover* classi7cations are s&own in Fig. 1. $n t&is report t&e waterfooding process as a secondar* oil recover* is &ig&lig&ted. ,&e cost o waterfooding process is relativel* low in comparison wit& ot&er oil recover* met&ods. ,&e process oten involves converting some production wells into in%ection wells to increase t&e contacted 9one (etween t&e oil and in%ected water. urt&ermore reservoir simulation ma* also (e involved in waterfooding process to predict t&e fuid (e&aviour in t&e reservoir and t&ereore optimi9ing t&e process and ma8imi9ing t&e recovered oil rom waterfooding pro%ect. @ore detail o t&e process is discussed in t&e su(seuent section and lin:ed wit& simulation studies to (etter understanding.
4
Figure 1A ,&e categories o t&e oil recover* mec&anisms S;' 2#15.
2.0 2.1
Part A Reseroir si!ulation
;asicall* t&e term simulation means t&e representation o d*namic processes (* eit&er a p&*sical or t&eoretical model. $n petroleum engineering modelling t&e fuid fow in porous media is signi7cant and t&ereore reservoir simulation must (e preormed. Reservoir simulation reers to t&e use o means t&at provides a numerical model o t&e petrop&*sical and geological c&aracteristics o a reservoir in order to predict and anal*9e t&e reservoir fuid perormance under di=erent conditions. ,&e reservoir simulation modeling usuall* consists o t&ree parts in its (asic ormA 1. / geological modelA it is a mat&ematical description o t&e reservoir and its petrop&*sical and geological c&aracteristics to orm a volumetric grid w&ic& descri(es t&e porous roc: ormation. 2. / fow modelA it is a mat&ematical model w&ic& descri(es t&e fuid fow in a porous media. ,&is is t*picall* given as a set o euations o t&e conservation o mass and volume toget&er. 3. / well modelA it descri(es t&e fow in and out o t&e reservoir fuids and computes t&e production and in%ection rates or a given (ottom &ole pressure or t&e opposite. ,&e ma%or purpose o reservoir simulation is to predict t&e reservoir fuids (e&aviour over time and optimi9e t&e development plans to ma8imi9e t&e oil recover*. ,&is o(viousl* will assist in ta:ing t&e investment and operational decisions. /lt&oug& t&e reservoir simulation is an invalua(le tool t&e need o simulation studies depends greatl* on some actors suc& as t&e geological setting t&e 7eld maturit* and t&e production environment o=s&ore or ons&ore.
5
,&ere are several reservoir simulators designed to model t&e fow in reservoir s*stem. ,&ese simulators are computer programs t&at solve fuid fow pro(lems using mat&ematical tec&niues (ased on t&ree undamental euations 1 -arc*Bs law 2 material (alance euation and 3 conservation o mass euations. / t*pical simulator fow c&art is s&own in Fig.2.
2.2
Figure 2A / t*pical simulator fow c&art anc&i and Co&n 2##5. Princi"le of #ater$ooding
,&e in%ection o water into t&e reservoir to displace t&e oil and t&ereore increase t&e production is called waterfooding as illustrated in Fig. 3. ,&is process is per&aps one o t&e most common met&ods used as secondar* oil recover*. Distoricall* waterfooding was recogni9ed accidentall* in more t&an 1## *ears ago w&en s&allow water entered an oil well and conseuentl* t&e oil production rom t&at well was diminis&ed w&ereas t&e production rom t&e surrounding wells was increased. ,&e widespread waterfooding (egan in t&e earl* 1"5#Bs and grew steadil* until now to (ecome t&e dominant fuid in%ection tec&niue. $n act t&e principle o waterfooding is t&e same as t&e pressure maintenance principle. $n (ot& cases t&e oil is displaced (* t&e in%ected water (ut t&e onl* di=erence is t&at t&e waterfooding results a signi7cant increase in t&e oil production w&ile t&e pressure maintenance mig&t not. $n t&e t*pical pressure maintenance process t&e water is in%ected into t&e auier to eit&er maintain or increase t&e reservoir pressure at or near t&e (u((le point pressure or to augment t&e water drive (* retarding t&e natural decline in t&e e8isting reservoir pressure.
6
Figure 3A $llustration o waterfooding process.
,&ere are di=erent reasons in w&ic& t&e waterfooding &as (ecome t&e most widel* and successull* met&od ever used in t&e world as an oil recover* mec&anism. ,&ese primar* reasons areA 1. 2. 3. 4. 2.3
,&e ease availa(ilit* o t&e water particularl* in o=s&ore 7elds. ,&e low cost o water compared wit& ot&er fuids. ,&e water can (e in%ected into t&e reservoir ormation easil*. ,&e e+cient and e=ective displacement o t&e oil (* t&e water. %ater$ood candidates
0arious actors ma:e an oil reservoir a successul candidate or waterfooding. ,&omas @a&one* and Winter 1"" generali9e t&ese actors (* considering t&e ollowing reservoir c&aracteristicsA Reseroir geo!etr&
,&e geometr* o t&e reservoir pla*s an important role in t&e (e&aviour o t&e waterfooding. ,&e reservoirBs geometr* will directl* impact on t&e location o t&e wells and also t&e num(er o platorms in case o an o=s&ore 7led and t&ereore will essentiall* govern t&e oil recover* (* t&e water in%ection practices. ,&e previous perormance o t&e reservoir and good anal*sis o t&e reservoirBs geometr* are necessar* not onl* to de7ne t&e strengt& o natural water drive (ut also to :now t&e need o an additional supplement o t&e natural energ* (* in%ection. ,&e water in%ection is considered unnecessar* i t&e natural water derive classi7ed as an active mec&anism.
Fluid "ro"erties
,&e p&*sical fuid c&aracteristics o a given reservoir &ave an important e=ect on w&et&er t&e reservoir is reuired a urt&er development or not (* t&e water in%ection. ,&e oil viscosit* is considered as t&e principal fuid c&aracteristic w&ic& a=ects on t&e percentage o success o t&e waterfooding process. ,&e most important varia(le to (e considered is actuall* t&e mo(ilit* ratio @ t&at de7nes as t&e mo(ilit* o t&e displacing fuid to t&e mo(ilit* o t&e displaced fuid i.e. t&e e=ective permea(ilit* to t&e viscosit* o t&e displacing and displaced fuids t&e mo(ilit* ratio @ can (e e8pressed as ollowsE
So or waterfoodingE
,&e a(ove e8pression o t&e mo(ilit* ratio &as (een standardi9ed (* t&e Societ* o Petroleum )ngineering SP) since 1"5 Cames and William 1""". / good waterfooding &as a avoura(le mo(ilit* ratio euals to or is less t&an 1. ,&is means t&e oil will fow (etter t&an t&e water and t&e water will displace t&e oil easil*. 'onversel* i t&e mo(ilit* ratio is greater t&an 1 unavoura(le mo(ilit* ratio t&en t&e water will fow (etter t&an t&e oil and t&e displacement e=ectiveness o oil (* water will decrease. $n t&is case e8tremel* viscous oil t&e water will leave (e&ind muc& o t&e (*passed oil. Fenerall* a range rom #.#2 to 2.# o t&e mo(ilit* ratio was encountered during t&e waterfooding orrest 1"5. Reseroir de"t'
,&e dept& o t&e reservoir is an important actor on eit&er a secondar* or tertiar* oil recover* process and it ma* a=ect (ot& t&e economic and tec&nical sides o t&e pro%ect. $n t&e economic aspect t&e operating costs and investment increases as t&e reservoir dept& increases. ,&is generall* results an increase in t&e drilling and liting operation costs. $n t&e tec&nical aspect t&e reservoir dept& s&ould (e deep enoug& so t&at t&e in%ection pressure would (e less t&an t&e racture pressure o t&e reservoir. !t&erwise a poor waterfooding process would (e occurred as a conseuence o t&e &ig& water in%ection rates. $n a t*pical waterfood process a critical pressure o appro8imatel* 1 psiGt o dept& must not (e e8ceeded so no ractures will (e induced in t&e reservoir. /s a result
a gradient pressure o #.5 psiGt o dept& would (e normall* su+cient to provide e+cient waterfood /&med 2##6. Fluid saturations and roc( "ro"erties
,&e petrop&*sical roc: properties suc& as porosit* average permea(ilit* and fuid saturations &ave a direct infuence on t&e success o t&e waterfooding process. $nsu+cient oil saturation and porosit* in a reservoir will result a none=ective waterfooding process and t&us would not (e economicall* %usti7ed (ecause o t&e produced oil will not (e enoug& to o=set t&e operating costs and investment. ,&e average permea(ilit* o t&e reservoir must (e &ig& enoug& to allow su+cient water in%ection wit&out racturing t&e reservoir. Reseroir unifor!it& and "a& continuit&
,&e reservoir uniormit* considers as a main p&*sical criterion or successul waterfooding. ,&e e8istence o aults reservoir structure and permea(ilit* trends a=ect t&e location o new in%ection wells w&ere a good communication must (e introduced (etween t&e production and in%ection wells. $n some reservoirs w&ic& are signi7cantl* &eterogeneous a serious c&annelling e8ists and t&ereore a lot o reservoir oil will (*passed and t&e waterfooding mig&t (e considered useless and unpro7ta(le. /lso t&e pa* continuit* pla*s an important role or a successul waterfooding. Pri!ar& reseroir driing !ec'anis!
,&e primar* oil recover* mec&anism s&ould (e considered careull* or an* potential waterfooding process. Fas cap and water derive reservoirs are not normall* considered to (e appropriate candidates or waterfooding. Dowever water in%ection ma* (e introduced or (ot& cases in order to maintain t&e pressure. / reservoir dominated (* solution gas drive mec&anism is usuall* considered t&e (est candidate or successul waterfooding due to low primar* recover* e8ists in t&e reservoir.
2.4
)"ti!u! #ater$ooding
,&e critical point or a successul waterfooding pro%ect is determining t&e optimum time to start. ,&e optimum time is actuall* determining on t&e (asis o t&e reservoir pressure. /&med 2##6 summari9ed t&e most important procedure w&ic& &as to (e considered and calculated to determine t&e optimum time or waterfooding as ollowsE
"
• • • • •
• •
Prospect oil recover*. Production rates o fuids. inancial investment o t&e pro%ect. ,&e ualit* and availa(ilit* o t&e reuired water to (e in%ected. 'osts involved in drilling new wells or in%ection or converting e8isting wells rom producer to in%ector. 'osts involved in pumping euipment and water treatment. 'osts involved in operation and maintenance o t&e water acilities.
,&ese points s&ould (e e8amined and calculated or man* times to determine t&e net income or eac& case w&en t&e waterfooding is reuired. ,&e (est case w&ic& meets t&e desira(le o(%ectives and ma8imi9es t&e pro7t is selected. /dditionall* 'ole 1"6" suggested tec&nical and economic actors w&ic& also must (e considered to determine t&e optimum time or pressure to start waterfooding. ,&ese actors are listed (elowE Reseroir oil iscosit&
/s mentioned earlier t&e oil viscosit* is t&e principle fuid c&aracteristic t&at a=ects on t&e degree o success o waterfooding pro%ect. ,&e water in%ection process is usuall* initiated w&en t&e reservoir pressure closes to its (u((le point pressure w&ere t&e oil viscosit* (ecomes at its minimum value at t&is pressure. ,&ereore t&e oil mo(ilit* increases as t&e oil viscosit* decreases resulting mo(ilit* ratio around 1 and (etter sweeping e+cienc*. Free gas saturation and "roductiit& of "roducing #ells
$n case o water in%ection it is preerred t&at t&e reservoir &as initial gas saturation up to 1# > and t&is occurs onl* at a pressure w&ic& is (elow t&e (u((le point pressure. 'onversel* a &ig&er pressure is desira(le to increase t&e productivit* o producing wells and w&ic& t&ereore e8tends t&e fowing time o t&e wells s&ortens t&e pro%ectBs overall lie and decreases t&e operating costs. Cost of in*ection e+ui"!ent
,&e cost is related directl* to t&e reservoir pressure w&ere at &ig&er pressure t&e cost increases. !n t&e ot&er &and t&e cost o in%ection euipment is relativel* less at low reservoir pressure. )erall life of t'e reseroir and t'e e,ect of dela&ing inest!ent
/s t&e operating e8penses are a ver* important part o t&e total costs t&e water in%ection s&ould start as earl* as possi(le. !n t&e ot&er &and a dela*ed investment in t&e acilities o water in%ection ma* (e desira(le (ecause o t&e e=ect o time on t&e value o mone*. 2.5
-election of #ater$ood "attern
1#
,&e selection o waterfood pattern is one o t&e most important steps w&en designing a waterfooding pro%ect. ,&e ma%or goal is to c&oose t&e appropriate pattern w&ic& provides a ma8imum contact o t&e in%ection fuid wit& t&e target oil. ,&e c&oice must (e consistent and related wit& t&e e8isting well pattern t&e reservoir geometr* and geolog* and t&e o(%ective o waterfooding. ,&e economics o t&e waterfooding pro%ect can dictate t&e selection o t&e fooding pattern (* eit&er converting e8isting producer wells into in%ectors or drilling in7ll in%ection wells. ,&is will lead to eliminate some patterns rom consideration automaticall*. $n general a proper waterfood pattern or a reservoir s&ould meet t&e ollowing criteriaA 1. Provide t&e desired oil production rate. 2. Provide necessar* water in%ection rate to *ield t&e desired oil production rate. 3. @a8imi9e oil recover*. 4. ,a:e advantage o reservoir c&aracteristics suc& as aults ractures permea(ilit* trends etc. 5. /d%ust wit& e8isting well pattern and reuire less in7ll wells. ;asicall* t&ere are our common t*pes o t&e well arrangements (eing used as waterfood patternsA 2.5.1 Irregular in*ection "atterns
Some 7elds were developed using irregular patterns due to t&e use o slant &ole drilling tec&niue andGor t&e surace or su(surace topolog*. ,&is results non uniorm location o t&e production or in%ection wells. !t&er actors suc& as t&e aults variation in porosit* and permea(ilit* trends ma* *ield irregular patterns. 2.5.2 Peri"'eral in*ection "atterns
,&e perip&eral fooding patterns utilise all or a part o reservoir e8ternal (oundar* as locations o t&e in%ection wells see Fig. 4. $t usuall* reers as a line food i a single line o wells located eit&er along one side or down t&e middle o t&e 7eld. ,&is t*pe o fooding patterns &as several advantages suc& as 1 it *ields a ma8imum oil recover* wit& ewer in%ection wells and t&us less initial investment 2 it results less water production and dela*s t&e water (rea:t&roug& and 3 it can (e used wit& dipping reservoir and reservoir wit& permea(ilit* variations. ,&e main disadvantage o perip&eral fooding patterns &appens w&en t&e reservoir &as &ig& gas saturation since it will ta:e a long time until t&e reservoir gas space is 7lled up wit& t&e in%ected water. 'onseuentl* a dela* in a signi7cant oil recover* response will occur and a considera(le water in%ection e8pense is reuired.
11
Figure 4A $llustration o two common cases in w&ic& perip&eral 2.5.3 Regular in*ection "atterns
@an* 7elds were developed (* using a regular in%ection pattern due to t&e act t&at most o t&e oil leases divided into suares wit& di=erent owners&ip. ,&e most common regular patterns o t&e production and in%ection well arrangements as s&own in Fig. 5 areA
Figure 5A ,&e geometr* o t&e most common regular in%ection patterns. irect line drie
$n t&is fooding pattern t&e lines o production and in%ection wells are directl* o=set eac& ot&er. ,wo important varia(les is c&aracteri9ed t&is patternA 1 d H w&ic& is t&e distance (etween ad%acent lines o t&e producers and in%ectors and 2 a H w&ic& is t&e distance (etween ad%acent wells in t&e same line. $n t&e direct line drive pattern t&e ratio o producers to in%ectors is unit*.
12
-taggered line drie
,&is pattern is actuall* a modi7ed direct line drive pattern w&ere t&e wells are in lines (ut not directl* oppased to eac& ot&er an* more. /ccordingl* t&e lines o porduction and in%ection wells in staggered line drive are moved in w&ic& t&e wells in alternate lines are dispalced (* a distance o aG2. Fie/s"ot
,&e 7vespot pattern is a special case o t&e staggered line drive pattern in w&ic& t&e dGa ratio is constant and euals #.5. ,&is pattern is t&e most commonl* fooding pattern used in most areas since its conductivit* is &ig& w&ere t&e s&ortest fow pat& is a straig&t line (etween t&e producer and in%ector. $n t&e 7vespot pattern an* our in%ector wells orm a suare wit& a producer well and t&us t&e ratio o producers to in%ectors is unit*. -een/s"ot
,&is pattern &as two in%ector wells per a producer well and its merit t&at t&e in%ectivit* is low. ,&is pattern can (e considered as a staggered line drive (ut wit& a dGa ratio o #.66. ,&e inverted sevenspot pattern &as onl* one in%ector well per a pattern and is occasionall* used. ,&e inverted sevenspot also reers as ourspot pattern w&ere (ot& are identical. ine/s"ot
,&is pattern can (e developed rom a 7vespot pattern (ut wit& e8tra in%ector wells to (e drilled at t&e middle o eac& side o t&e suare. ,&is pattern can (e ver* useul i a &ig& in%ection rate is reuired due to t&e low permea(ilit*. ,&e ma%or advantage o ninespot pattern is its fe8i(ilit*. ,&e inverted ninespot pattern is usuall* utilised more t&an t&e normal ninespot pattern especiall* w&en t&e fuid in%ectivit* is &ig&. 2.5.4 Crestal and basal in*ection "atterns
$n t&e crestal pattern t&e in%ector wells are located at t&e top o t&e structure and it is most li:el* used wit& gas in%ections pro%ect. $n t&e (asal pattern t&e in%ector wells are located at t&e (ottom o t&e structure and it is usuall* used wit& water in%ection pro%ects wit& e8tra (ene7ts can (e gained rom gravit* segregation. Fig. s&ows an e8ample o (ot& patterns.
13
Figure A 'restal and (asal in%ection patterns used wit& dipping reservoirs. 2. recoer& ecienc&
sti!ation
of
t'e
oerall
#ater$ood
,&e overall recover* e+cienc* actor due to waterfooding pro%ect or an* fuid displacement process can (e determined at an* time o t&e pro%ect rom t&e ollowing e8pressionE
,&e generali9ed e8pression used to predict t&e cumulative oil produced oil displaced (* water in%ection in waterfooding pro%ect is given (* t&e ollowing euationsA
,&ereore t&e oil recover* actor can (e estimated onl* i t&e ollowing actors are :nownA 2..1 'e oil in "lace at t'e start of t'e "ro*ect
Relia(le predications o t&e waterfooding perormance or accurate interpretations o &istorical waterfooding (e&aviour can onl* (e :nown i a good estimation o t&e reservoir oil in place at t&e start o waterfooding pro%ect is availa(le. ,&e oil in place at t&e start o waterfooding is given (*A
14
2..2 is"lace!ent s#ee" ecienc&
$t is de7ned as t&e raction o oil in place t&at will (e displaced (* water and &as (een recovered rom t&e swept 9one at an* particular time. ,&e displacement sweep e+cienc* will usuall* increase at di=erent stages o t&e waterfooding process and can (e e8pressed as ollowsE
2..3 Areal s#ee" ecienc& A
,&e areal sweep e+cienc* represents t&e raction o t&e reservoir area or t&e total food pattern w&ic& &as (een contacted (* t&e in%ected water at a given time during a food. ,&e areal sweep e+cienc* increases graduall* wit& t&e start o water in%ection until t&e (rea:t&roug& &appens w&ic& ater it continues to increase slowl*. $t depends primaril* on t&e ollowing actorsA 1. 2. 3. 4. 5.
,&e relative fow properties o water and oil mo(ilit* ratio. ,&e location o production and in%ection wells waterfood pattern. Pressure distri(ution (etween t&e production and in%ection wells. -irectional permea(ilit*. ,otal volume in%ected.
,&e progression o waterfooding process according to areal sweep view is illustrated in Fig. 6. /t ,ime 1 t&e in%ection is initiated and a water (an: is ormed. /t t&is time t&e fow is c&aracteri9ed (* a radial fow s*stem and t&e reservoir normall* doesnBt respond to t&e waterfooding. !nl* a rapid reservoir response will occur i no gas e8ists at t&e start o waterfooding. ,&e displacing water and displaced oil are moved to 7ll up t&e gas space and a complete 7llup
15
is occurred at t&e end o ,ime 2. -uring t&is time t&e fow s*stem is not strictl* radial and is relativel* comple8. /ppro8imatel* at t&e midlie o t&e waterfooding ,ime 3 t&e oil production rate will (e essentiall* t&e same as t&e water in%ection rate. ,&is is due to t&e act t&at no ree gas remaining in t&e food pattern. ,&e edge o water (an: will eventuall* reac& t&e producer well and t&e time o (rea:t&roug& is approac&ed. /t ,ime 4 a rapid rise in t&e water production is occurred wit& a signi7cant decrease in oil fow rate.
2..4 7ertical Figures#ee" 6A ,&e ecienc& progression o7 waterfooding process wit& 7vespot
,&e vertical sweep e+cienc* is de7ned as t&e raction o a pa* 9one in vertical plane t&at is contacted (* water. ,&e vertical sweep e+cienc* sometimes reers to t&e invasion sweep e+cienc* and it depends (asicall* on t&e mo(ilit* ratio t&e degree o t&e permea(ilit* strati7cation e8isted in t&e reservoir and t&e cumulative water in%ected. /s a result o t&e nonuniorm permea(ilit* t&e in%ected water will tend to move irregularl* t&roug& t&e reservoir and t&ereore it is oten una(le to contact t&e entire vertical section o t&e reservoir. ,&e permea(ilit* variation o t&e reservoir is per&aps one o t&e greatest uncertainties w&ic& can (e encountered in designing a waterfooding pro%ect. 'onseuentl* t&e permea(ilit* variation is considered as t&e most signi7cant actor a=ecting t&e vertical sweep e+cienc*. @oreover t&e mo(ilit* ratio is also important to estimate t&e vertical sweep e+cienc*E a decrease in t&e mo(ilit* ratio will improve t&e vertical sweep e+cienc*. /n estimate o t&e vertical sweep e+cienc* can (e calculated (* two traditional met&odsE 1 Stiles met&od and 2 -*:stra Parsons met&od. ;ot& met&ods are assumed t&at t&e reservoir is consisted o an ideali9ed la*ered s*stem w&ic& is (ased on t&e permea(ilit* ordering. !t&er assumptions are also considered in t&e two met&ods suc& as no crossfow (etween t&e la*ers linear fow immisci(le displacement and pistonli:e displacement. ,&ese met&ods can (e
16
ound in waterfood te8t(oo:s and t&e* are too lengt&* to (e presented in detail &ere see reerences 2 and 4. ,&e progression o waterfooding process wit& vertical crosssection o a reservoir is illustrated in Fig. 8. $n t&is e8ample t&e reservoir is composed o la*ers wit& di=erent permea(ilities. /t earl* time o waterfooding process t&e in%ected water displaces t&e oil in &ig& permea(le la*ers increasingl*. !n t&e ot&er &and some residual oil &as (een let (e&ind in t&e reservoir la*ers wit& low permea(ilit*. inall* a &ig& wateroil ratio W!R is noticed ater t&e water (rea:t&roug& time.
Figure 8A ,&e progression o waterfooding process in vertical plane o a reservoir wit& 2.6 Case stud& 9Robertson Field
$n t&e purpose o (etter understating o waterfooding process a case stud* o waterfood 7eld &as (een e8amined. ,&e selected 7eld is Ro(ertson 'learor: ?nit R'?. ,&e 7eld is located geologicall* in Faines 'ount* west ,e8as on t&e nort&eastern part o t&e 'entral ;asin Platorm. ,&e production (egan in t&e earl* 1"5#Bs wit& an initial well development o 4# acre. ,&e waterfooding (egan in 1"1 wit& si8 in%ectors and progressed t&roug&out t&e unit. $n spite o t&e economicall* success t&e results were less t&an predicted ;ar(e and Sc&noe(eien 1". ,&e reservoir is a s&allow s&el car(onate Permian Ieonard age and t*picall* &eterogeneous (ot& verticall* and laterall*. ,&e p&*sical properties o t&e reservoir are s&own in able 1. ,&e primar* oil recover* was dependent entirel* on t&e solution gas derive. ,&e recover* actor rom t&is mec&anism was
1
estimated > o t&e !!$P. ,&is relativel* low primar* recover* was t&e ma%or reason to initiate waterfooding process or t&e 7eld. able 1A ,&e p&*sical properties o t&e Ro(ertson 7eld reservoir Feorge and Stiles 1". Reseroi r "ro"erti es
Area 9acres ; de"t' 9ft
Porosit & 9<
Per!eabili t& 9!d
-aturation "ressure 9"si
)il iscosit& 9c"
alue
4## 8 55##
6.3
#65
164#
1.2
%ater$ooding strateg& of Robertson =led
,&e well arrangement o t&e 7eld was initiall* developed wit& 4# acres per producer well. Since t&e waterfooding (egan some wells were converted into in%ectors t&us creating 7vespot waterfood pattern. ,&e 7rst stage o in7ll wells was (* drilling one additional well on eac& 4# acre t&ereore developing t&e 7ve spot pattern to t&e inverted ninespot pattern i.e. one in%ection well per t&ree production wells. ,&is pattern is still in operation up to date as s&own in Fig. >. ,&e oil recover* actor o waterfooding was estimated to (e 1 > o t&e !!$P. ,&e data used to estimate t&e waterfood recover* actor is s&own in able 2. able 2A ,&e reservoir parameters or Ro(ertson 7eld at t&e start o waterfooding process ;ar(e and Sc&noe(eien 1". "ara!e ter
?ross t'ic(ness 9ft
@obili t& ratio
?as saturati on
%ater iscosit& 9c"
Initial oil saturat ion
Residual oil saturation
alue
14##
#."6
#65
#.6
#.#
#.34
2.8
iscussion Figure >A ,&e evolution o waterfooding patterns in Ro(ertson 7eld.
Since t&e gas solution drive was t&e primar* recover* mec&anism in Ro(ertson 7led and onl* > o !!$P was recovered t&e 7eld was &ig&l* candidate or waterfooding process. /lt&oug& some di+culties &ad (een encountered t&e waterfooding s&owed a successul recover* and increased t&e overall recover* e+cienc* to 1 >. ,&e di+cult* can (e summari9ed in t&e reservoir c&aracteristics. $n suc& car(onate reservoir a &ig& degree o vertical and areal 1
&eterogeneit* is present wit& relativel* low permea(ilit* and porosit*. urt&ermore t&e degree o t&e permea(ilit* strati7cation e8isting in t&e reservoir is signi7cant and t&us resulting poor sweep e+cienc* and poor lateral and vertical continuit* o t&e reservoir fow. ,&e inadeuate completions and t&e reservoir discontinuities limit t&e fooda(le volume o t&e total reservoir and t&ereore infuence on t&e waterfooding perormance. ,*picall* t&e waterfooding (egan wit& 7vespot pattern w&ic& is t&e most commonl* used in suc& condition. ,o overcome t&e reservoir poor continuit* and &ig& in%ectivit* t&e waterfood 7vespot pattern was modi7ed to inverted nine spot pattern (* drilling an e8tra producer at t&e middle o eac& side. ,&is o(viousl* increased t&e well densit* t&e num(er o wells in a speci7ed area. 'onseuentl* t&e well spacing is decreased and provided more access to t&e unswept parts o t&e reservoir. ,&is waterfood pattern was not adeuate to (alance t&e in%ectivit* wit& wit&draws so some production wells were converted to in%ection wells. $n terms o pressure t&e di=erential pressure (etween t&e production well and in%ection well &as decreased due to reducing t&e distance (etween wells. ,&e mo(ilit* ratio during t&e waterfooding process euals #."6 w&ic& is around t&e avoura(le range less t&an 1. ,&is indicates t&at t&e water fow was (etter t&an oil and t&us it displaced oil easil* and e=ectivel*.
3.0 3.1
Part B: -i!ulation
$n t&is part o t&e report a simulation o reservoir &as (een perormed (* using Petrel simulator reservoir engineering. Petrel is computer sotware owned (*
1"
Sc&lum(erger w&ic& provides integrated solutions rom e8ploration to production. ,&e main goal o using Petrel was to propose two development strategies using waterfooding. $n addition o t&e two proposed cases an initial case &as (een constructed in Petrel (ased on a given strateg*. ,&e given strateg* includes two production wells P#1 and P#2 and two in%ection wells $#1 and $#2. / simple gird &as (een made (* using t&ree suraces top middle and (ase suraces wit& 1## meters o JK and JL. So two 9ones &ave alread* (een created and eac& 9one &as 5 la*ers. ,&e petrop&*sical reservoir properties porosit* permea(ilit* and net to gross were populated (* using petrop&*sical modelling w&ic& &as produced a random distri(ution o t&e properties t&roug& t&e model according to a certain seed num(er. able 3 s&ows t&e given reservoir properties t&at &ave (een inputted into Petrel to ma:e a t&ree dimensions reservoir model. ,&e seed num(er used is 1615"#E t&ereore a uniue reservoir model &as (een created associating wit& t&at seed num(er. able 3A ,&e reservoir properties used or petrop&*sical modelling in Petrel. Pro"ert& Porosit& 9fraction Per!eabil it& 9! et to ?ross 9fraction
@ini!u!
@a;i!u!
@ean
-tandard deiation
istributi on
#.#3
#.45
#.2"
#.#5
Mormal
#
##
3##
15#
Iog Mormal
#.#5
#.65
#.5
#.134
Mormal
!t&er reservoir properties are listed (elowA • • • • • • • • • •
Fas oil contact H 15## m Water oil contact H 26## m ;u((le point o crude oil H # (ars racture pressure H 35# (ars $nitial pressure H 256 (arsN Reservoir dept& H 3### m Reservoir temperature H 6.5 o' !il gravit* H 3# /P$ !il densit* H 5 OgGm 3 Water salinit* H 3#### ppm
,&e original oil in place !!$P was calculated 12#" 8 1# 6 sm3. !t&er parameters were also calculated or (ot& 9ones as s&own in able 4.
able 4A ,&e calculated parameters or (ot& 9ones wit& t&e total t&e !!$P rom volume calculation in Petrel.
2#
Para!etersone ;ul: volume m3 Met volume m 3 Pore volume m3 Segments otal -)IIP 9s!3
one 1 63" 8 1#6 31#4 8 1#6 56 8 1#6 Segment 1
one 2 26#6 8 1#6 121# 8 1#6 353 8 1# 6 Segment 1 120> ;10
3.1.1 Initial case
$n t&e initial case t&e fuid model &as (een made (* using a deault model or ;lac: oil and t&e consolidated sandstone or t&e roc: p&*sic unction. /ter t&at t&e model &as (een initiali9ed (* using t&e euili(ration met&od and t&e wells also were completed and perorated. ,&e simulation was run rom 2#15 to 2#35 and t&e result was visuali9ed. $n t&is strateg* t&e oil production cumulative was 5.6 8 1# sm3 and t&e recover* actor was calculated according to t&e ollowing euationE Recover* actor R H cumulative oil G original oil in place •
R initial case H 5.6 8 1# G 12#" 8 1#6 H 4.6 >
$t seems t&at t&e recovered oil in t&is strateg* is relativel* low and t&is is (ecause t&e num(er and location o t&e wells used. ,&ereore additional two strategies &ave (een perormed to increase t&e oil recover* actor and ma8imi9e t&e oil production in t&e seam period. Dowever t&e new strategies were constructed (ased on t&e case stud* Ro(ertson 7eld and t&e waterfooding researc& in t&e Part / o t&is report. /s mentioned earlier in Part / a successul development strateg* o an* 7eld (* using waterfooding pro%ect depends on man* actors w&ic& must (e considered careull*. ,&e selection o t&e well pattern is one o t&e most important steps to (e considered w&en designing waterfooding. ,&is well arrangement will a=ect in somewa* t&e amount o in%ected water t&at s&ould (e in contact wit& t&e target oil in reservoir. ,&ereore t&e reservoir properties especiall* t&e mo(ilit* ratio and permea(ilit* will infuence directl* t&e distri(ution o t&e in%ected water and t&e e+cienc* o waterfooding process. $n Ro(ertson 7eld waterfooding pro%ect &as started since t&e recovered oil rom t&e primar* was onl* > o t&e !!$P. ivespot pattern w&ic& is t&e most common waterfood pattern was t&e 7rst well arrangement or waterfooding in t&e 7eld. ,&e oil production increased (ut also t&e in%ectivit* increased so t&e pattern was modi7ed to an inverted ninespot pattern to (alance t&e wit&draws wit& t&e in%ectivit*. $n t&e inverted ninespot pattern an* eig&t production wells orm a suare wit& an in%ection well and t&us t&e ratio o producers to in%ectors is t&ree. ;ac: to t&e simulation t&e 7vespot and inverted ninespot patterns were proposed and implemented as new two development strategies in t&e reservoir.
21
,&e results were compared wit& t&e initial case and t&e grap&s were plotted as will (e discussed in t&e su(seuent section. 3.1.2 First -trateg& 9Inerted nine/s"ot "attern
,&e same procedures in t&e initial case were conducted in Petrel (ut t&is time new in%ectors and producers were inserted in order to improve t&e oil recover* and t&e waterfooding e+cienc*. $n t&e 7rst strateg* t&e well arrangement was (ased on t&e inverted ninespot pattern. ,&e well location and spacing was selected according to t&e net gross and permea(ilit* w&ere t&e new producers drilled in t&e most potential oil 9one. ,&e in%ection well pressure was set 2"# (ars w&ic& is less t&an t&e racture pressure 35# (ars to insure t&at it doesnBt e8ceed t&e saet* margin and t&en no ormation damage will occur. $n addition t&e production well pressure was set to (e "5 (ars w&ic& is &ig&er t&an t&e (u((le point pressure # (ars in order to &ave onl* oil production wit&out gas. $n Fig. 10 t&e inverted ninespot waterfood pattern is illustrated. $t is clear t&at onl* one in%ector in t&e middle surrounding wit& producers in w&ic& " wells in total were used. $n comparison wit& t&e initial case a massive increase in oil production rate was noticed and t&us &ig&er oil cumulative. ,&is is due to increasing t&e producer wells w&ere eac& t&ree orm a suare wit& t&e in%ector.
Figure 10A ,&e 7rst strateg* wit& inverted ninespot waterfood pattern.
$n t&is strateg* t&e oil production cumulative was calculated ".# 8 1# sm3. So t&e oil recover* actor was estimated as ollowsE
22
•
R 7rst strateg* H ".# 8 1# G 12#" 8 1# 6 H .5 >
,&ere is an increase around 3 > in t&e oil recover* rom t&e initial case. Dowever t&e water production was also increased and t&ereore more water &andling acilities s&ould (e ta:en in consideration. 3.1.3 -econd strateg& 9Fie/s"ot "attern
$n t&e second strateg* t&e 7vespot waterfood pattern was selected or t&e well arrangement. $n t&is pattern t&e ratio o producer to in%ector is unit*. ,&e pattern is ormed (* some modi7cation in t&e inverted ninespot pattern w&ere some wells were converted rom production wells to in%ection wells. ,&e reservoir model wit& t&e wells location is s&own in Fig. 11. /s a result o using t&is pattern a considera(le increase in t&e oil production occurred w&ere t&e cumulative oil production was 1.1 8 1# sm3. $n comparison wit& t&e initial case and t&e 7rst strateg* t&e second strateg* is t&e &ig&est oil production cumulative in t&e period o 2# *ears. urt&ermore t&e water production rate is too &ig& rom t&e (eginning o t&e waterfooding pro%ect. ,&e oil recover* actor was estimated as ollowE •
R second strateg* H 1.1 8 1# G 12#" 8 1# 6 H ".1 >
Figure 11A ,&e second strateg* wit& 7vespot waterfood pattern
$n all cases ater t&e well location was selected t&e well completion casing and perorations o t&e target interval were perormed automaticall* (* Well completion design in Petrel. /n e8ample o t&e well completion is s&own in Fig 12.
23
3.2 Result Fi ure 12A /n e8am le o t&e well com letion and eroration or in ector and
Figure 13A ,&e oil production cumulative or eac& strateg*. Fig. 13 s&ows t&e grap&s o t&e oil production cumulative or eac& case in t&e period rom 2#15 to 2#35. $n t&is period o t&e time t&e oil production cumulative o t&e second strateg* is t&e &ig&est production. ,&is is due to t&e well arrangement and spacing w&ere t&e ratio o producer to in%ector euals 1. ,&is pattern is &ig&l* conductive w&ere t&e s&ortest fow pat& is a straig&t line (etween t&e producer and in%ector. ,&is leads to an e=ective displacement o t&e oil (* t&e water and results good sweep e+cienc*. $n t&is case t&e second strateg* is preerred over t&e ot&er two strategies.
24
Figure 14: ,&e oil production rate or eac& strateg*. Fig. 14 S&ows t&at t&e oil production rates reac&ed t&eir pea: or all cases at t&e (eginning o t&e production w&ere t&e &ig&est rate was appro8imatel* 53### sm3Gda* in t&e 7rst strateg*. /ter t&at all rates &ave decreased and levelled o= at constant rates (ecause o t&e pressure decreased wit& t&e time. )ven alt&oug& t&e oil rate o t&e 7rst strateg* was &ig&er t&an t&e oil rate o t&e second strateg* in certain time t&e rate o second strateg* is preerred.
Figure 15A ,&e watercut or all cases.
25
Figure 1A t&e water production or all cases.
;ot& grap&s in Fig. 15 and Fig. 1 s&ow t&e water production or all strategies in 2# *ears period. ,&e watercut and water production rate reac&ed t&eir ma8imum value at 55 > and 1#1## sm 3 respectivel* (* 2#35 or t&e second strateg*. ,&is is too &ig& water production rate in comparison wit& t&e initial and 7rst strategies. ,&is &ig& rate can (e interpreted (ecause o t&e num(er o in%ector wells in t&e second strateg* w&ic& is relativel* &ig&er t&an t&e in%ector wells in t&e ot&er strategies. ,&is &ig& water rate indicates t&at t&e (rea:t&roug& time will de7antl* occur in t&e second strateg* muc& uic:er t&an t&e ot&er strategies. /ccording to t&e water production rates t&e 7rst strateg* is avoura(le over t&e second strateg*. /lt&oug& t&e water rate o t&e initial strateg* is relativel* less t&an t&e one o 7rst strateg* t&e &uge di=erence in t&e oil production o t&e 7rst strateg* ma:e it t&e (est case. ,&e watercut o t&e initial and 7rst strategies will reac& 12.5 > and 25 > in 2#35 respectivel*. Dowever t&e &ig& water production wonBt (e a pro(lem as soon as t&e water &andling production acilities is availa(le. 3.3
iscussion
$n t&is section o t&e report a sensitivit* anal*sis or all strategies is considered in t&e (asis o t&e num(er o wells and t&e di=erence (etween t&e production and cost. ,&e num(er o t&e wells and t&e oil production cumulative or all strategies are s&own in able 5. irst according to t&e num(er o t&e well it is clear t&at t&e initial strateg* &as ewer wells t&an t&e ot&er strategies. ,&ereore t&e total cost o t&e wells will (e a(solutel* less. ,&e cost o drilling well depends on man* actors suc& as t&e reservoir geolog* t&e production environment t&e dept& etc. ,&e average cost o drilling well according to C/S data /P$ 2##4 is 3.4 million or an average dept& o 34## m. ,&is cost includes t&e drilling operations completion and an* ot&er involved operating costs. So t&e total cost o t&e wells o t&e initial strateg* will (e 4 8 3.4 H 13.6 million and it will (e 3#.6 and 34 million or 26
t&e 7rst and second strategies respectivel*. /lt&oug& t&e num(er o wells is reasona(le or all strategies t&e initial strateg* is preerred (ased on t&e total cost o t&e drilled wells. Second t&e total price o oil production cumulative or 2# *ears is t&e second actor in w&ic& t&e (est strateg* will (e selected. ,&e oil price is c&angea(le wit& t&e time according several actors suc& as t&e politics t&e suppl* and demand tread oil t*pe etc. (ut in t&is estimation a constant price is considered. ,&e oil price toda* is 62 per (arrel so t&e total oil production or t&e second strateg* will ma:e 62 8 6"1"162 H 4.3 8 1# 1# w&ereas t&e oil production cumulative o t&e 7rst and t&e initial strategies will ma:e 3.5 8 1# 1# and 2.2 8 1# 1# respectivel*. ,&ereore t&e pro7t rom eac& strateg* will (e t&e oil production cumulative price t&e total cost o t&e wells. or e8ample t&e pro7t or t&e second strateg* euals 4.3 8 1# 1# Q 34 81# 6 H 4.2"6 8 1# 1#. ,&is is actuall* a roug& estimation (ecause man* ot&er costs are involved suc& as t&e cost o t&e in%ected water water euipment operating cost etc. Dowever it seems t&at all strategies are economic and t&us all o t&em can (e considered as a development pro%ect. /s soon as t&e second strateg* is t&e &ig&est oil production and t&e most pro7ta(le it &as (een selected to t&e waterfooding strateg* or t&e 7eld.
4.0 •
•
Conclusion
Reservoir simulation reers to t&e use o means t&at provides a numerical model o t&e petrop&*sical and geological c&aracteristics o a reservoir in order to predict and anal*9e t&e reservoir fuid perormance under di=erent conditions. /lt&oug& t&e reservoir simulation is an invalua(le tool t&e need o simulation studies depends greatl* on some actors suc& as t&e geological
2
•
•
•
•
•
•
•
setting t&e 7eld maturit* and t&e production environment o=s&ore or ons&ore. $n most cases onl* 5 to 3# > o t&e original oil in place !!$P can (e recovered (* t&e primar* oil recover*. ,&e insu+cient recovered oil in t&is mec&anism led to di=erent practices to support t&e neutral energ* o t&e reservoir (* in%ecting immisci(le gas or water into t&e reservoir ormation w&ic& is :nown as t&e secondar* oil recover*. ?p to 3# > additional recover* o t&e !!$P can (e recovered (* using t&e secondar* oil recover* tec&niue. Waterfooding is per&aps one o t&e most common met&ods used as secondar* oil recover* (ecause o t&e availa(ilit* o t&e water t&e low cost o water compared wit& ot&er fuids and t&e water can (e in%ected into t&e reservoir ormation easil*. 0arious actors ma:e an oil reservoir a successul candidate or waterfooding suc& as t&e reservoir geometr* and dept& t&e mo(ilit* ratio (etween oil and water and roc: properties. ,&e selection o waterfood pattern is one o t&e most important steps w&en designing a waterfooding pro%ect w&ere appropriate pattern provides a ma8imum contact o t&e in%ection fuid wit& t&e target oil in t&e reservoir. )stimation o t&e overall waterfood recover* actor depends on t&e displacement e+cienc* t&e areal e+cienc* and t&e vertical e+cienc*. /lt&oug& t&e inadeuate completions and t&e reservoir discontinuities in Ro(ertson 7led waterfooding s&owed a successul recover* and increased t&e overall recover* e+cienc*. $n simulation able 5 summari9es all t&e considered strategies and t&e results o(tain.
able 5A ,&e di=erences (etween all strategies and t&e results o(tain. Para!eterstrateg& u!ber of #ells 9Producers D in*ectors %ater$ood "attern )il "roduction cu!ulatie for 20 &ears 9s!3 %atercut 9< Recoer& factor 9<
Initial strateg&
First strateg&
-econd strateg&
4
"
1#
$rregular pattern
$nverted ninespot
ivespot
5.6 8 1#
".# 8 1#
1.1 8 1#
12.5
25
55
4.6
.5
".1
2
5.0
Reference
1. S;' 2#15. Sei9ing t&e )!R !pportunit* !nline /vaila(le romA &ttpsAGGwww.s(c.sl(.comG!urT$deasG)nerg*TPerspectivesG2nd >2#Semester13T'ontentG2nd>2#Semester>2#2#13TSei9ing.asp8 . /ccessed #1 @a* 2#15. 2. Cames ,. Smit& and William @. 'o(( 1""". Waterfooding ?S/. 3. orrest 'raig Cr. 1"5. ,&e Reservoir )ngineering /spects o Waterfooding Spe @onograp& Series 0olume 3. )dition. Societ* o Petroleum. 4. /&med P&- P) ,are: 2##6. Reservoir )ngineering Dand(oo:. Ful Proessional Pu(lis&ing !nline /vaila(le romA &ttpAGG#www.m*ili(rar*.com.lispac.ls(u.ac.u:U$-H2555 /ccessed #1 @a* 2#15. 5. 'ole . 1"6". Reservoir )ngineering @anual. Douston ,KA Ful Pu(lis&ing 'ompan*. 6. ,&omas '. ). @a&one* '. . and Winter F. W. 1"". Petroleum )ngineering Dand(oo:. -allasA Societ* o Petroleum )ngineers. . ;ar(e C. /. < Sc&noe(eien -. C. 1". Vuantitative /nal*sis o $n7ll PerormanceA Ro(ertson 'learor: ?nit. Societ* o Petroleum )ngineers doiA 1#.211G1556P/. . Feorge '. C. < Stiles I. D. 1". $mproved ,ec&niues or )valuating 'ar(onate Waterfoods in West ,e8as. Societ* o Petroleum )ngineers doiA 1#.211G63"P/. ". anc&i P&- Co&n R. 2##5. Principles o /pplied Reservoir Simulation. Ful Proessional Pu(lis&ing !nline /vaila(le romA &ttpAGGwww.m*ili(rar*.comU$-H62"4" /ccessed #3 @a* 2#15. 1#./merican Petroleum $nstitute /P$ 1"62##4. Coint /ssociation Surve* C/S on -rilling 'osts.X Was&ington -.' !MI$M) /vaila(le romA &ttpsAGGwww1.eere.energ*.govGgeot&ermalGpdsGegsTc&apterT6.pd . /ccessed # @a* 2#15.
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