AIIuvial Fan Facies and Their Distribution in the Lower Talang Acar Formation,

8/13/2019 AIIuvial Fan Facies and Their Distribution in the Lower Talang Acar Formation,

1/11

2007 Petroleum Science Vo l.4 NO.2

AIIuvial Fan Facies and Their Distribution in the Lower Talang Acar Formation,Northeast Betara Oilfield, Indonesia

Xie Chuanli, Ma Haofan , Liang Honggang, Li Dongmei, Qi Xiuli and Xian BenzhongLaboratory 1 e t r o Engineering under Ministry 01Education China University 01 Petroleum Beijing 102249 China

Abstract: Th is paper studies the alluvial fan facies characteristics and distribution in the Lower Talang Acar Formationin the Northeast Betara Oilfield. The conglomerate sedimentary characteristics and its distribution were studied based oncore data, logging interpretation and seismic property analysis. The research indicated that alluvial fan deposits of Bed Fin the Lower Talang kar Formation were characterized by granularity, poor sorting and low quality. Sand-bodiesaccumulate longitudinally, and inter-layers are poorly developed, extending locally in the transverse orientation. Typicallogging response of alluvial fan system is summarized, and conglomerate is characterized by low gamma-ray GR)intensity, low resistance, high density and low value between DLD and LLD , which reflects poor physical reservoirproperties, coarse rocks and relatively high density. Conglomerate is developed mainly in the northeast and middle-southofthe studied area. The upper part ofbed F is found in a small area in the middle-south, while the lower part ofbed F isdeveloped in a relatively large area in the middle-south.Key words: NOrtheast Betara Field, Lower Talang Acar Formation, alluvial fan facies, logging responses, conglomerate

1. In t roduc t ionNortheast Betara NEB) Field is located in the

Jabung Block in South Sumatra. It is the middle host

of the Betara Complex and is immediately to the westof and adjacent to the Betara Deep hydrocarbonkitchen Fig. 1) Santa Fe Energy Resources JabungLtd. , 1999).

Strait

Fig. 1 Jabung Block and N.E. Betara Field location map Santa Fe Energy Resources Jabung Ltd., 1999)The NEB structure, seismically defined as an

anomalous faulted anticline, was found on June 16,1995 by Well NEB-1 that encountered 266 feet ofLower Ta1ang Akar Formation with 117 feet of nethydrocarbon-bearing sand in eight individualsandbodies Santa Fe Energy Resources Jabung Ltd. ,

1999). Three of the sandbodies were tested at acombined rate of 18.22 MMCFID million cubic feetper day) and 432 BCPD barrels condensate per day).Well NEB-2 , drilled in March, 1996, encountered 42feet of net gas pay in two sandbodies of Lower Ta1angAkar Formation Sa1am, et l 1996). In the following


2/11

l.4 NO.2 Al luvial Fan Facies and Their Distribution in the Lower Talang Acar Fonnation Northeast Betara Oilfield Indonesia 19

of this Talang kar many delineation and development wells

ed and successfully resulted in gas and oilUp to date fifty two oil and gas wells have been

ed. Twenty wells among these existing wells haveSixteen 8 9 16 17 18 19 20 21 25 27 28 29

33 34) are being put on production (Lu et l , and

CO z content in the gas varies grea t y. Accordinglyis generally divided into three regions: Region1 in the east COz content about 52%; Region 2 in the CO z content about 27%; and Region COz content about 16%. The

and gross interval ratio compared to the time where this interval is a major

et a l. 1997 .From the results of production and previous studies

trata distribution sandstones prediction fluids et al ,

1997). So an integrated study was carried out based on lithologyas well as

eological settingNortheast Betara is located in the Jabung Block

outh Sumatra Basin near the transition to the CentralSumatra Basin Indonesia. The Jabung Block is a t e dn the island of Sumatra along the Sunda Island Archere the ocean crust of the Indian Ocean subductedorthward under the Sundaland Craton (Durlofsky

1992). Extensional back-arc stresses along this Sumatra

ource rocks (Wang et al , 1997 .Compressive tectonic movement began in the

of these earlier basins and graben andg a variety of structural trap configurations calledSunda Fold types which are characterized by the

ting of reactivated older normalau ts. The majority of the oi and gas fields in CentralSumatra South Sumatra and Sunda Basins occur in

these structural settings (Zhang et l , 1997 .Hydrocarbon sources for oil and gas charging ofBetara Complex could have come from the Betara Deepa large half-graben that lies adjacent to and to the east ofthe Northeast Betara discoveries (Cimolai et l , 1993 .Coals and organic-rich sediments within the LowerTalang Akar and Lahat formations in the deepestportion of Betara Deep the proven hydrocarbongeneration area are the hydrocarbon source rocks forthese fields. The seal for the Lower Talang Akarreservoir is the regional transgressive shale of the UpperTalang Akar as well as locally intra-formational shaleof the Lower Talang Akar.

The sedimentary succession in the South SumatraBasin comprises a single transgressive cyc e whichcommenced from Late Eocene to Early Oligocene withdeposition of the syn-rift transgressive alluvial fluviode taic locally lacustrine and marginal marine facies ofLahat and Talang Akar Formations. These sedimentsprogressively filled the subsiding half-graben andeventually covering the basement highs (Simlote et l ,1985).Marine conditions were eventually establishedduring the continuing transgression sequence withdeposition of an open marine facies of the GumaiFormation which consists of marine shale clay-stonemarls and fine-grained sandstones (Fig. 2 .

Initial uplift of the Sunda Shield to the east in theMiddle Miocene marked the end of the Early Tertiarytransgression sequence and the beginning of theregression sequence that continues to the present day.The Middle Miocene uplift and compression causedinversion of the previous depocenters as well as furtheruplift of basement highs. The compression alsocontinues to the present day and has resu ted in many ofthe hydrocarbon traps found in the Jabung Block as wellas through South Sumatra.The regressive distal de ta front to marginal marinefluvio-de taic facies of the Gumai and Air BenakatFormations were deposited as a resu t of increasedsediment load from the Sunda landmass to the northeastThis regressive cyc e was periodically interrupted bysubt e transgressive events primari y comprising distalde ta front shale distributary mouth bar sands de ta barsands channel sands and interdistributary shale (Fig. 2 .A rapid increase in compressive tectonic movementin the Late Miocene accelerated sediment influx fromthe emergent areas. The regressive lower


3/11

20 Petroleum Science 2007

which may be a continuation of the regressive fluviodeltaic Muara Enim Formation Fig.2) Santa Fe Energy

Southi t h o f c i

l pper sandy memberLower member

Resources Jabung td. 1999).No h

Hvdrocarbonl Seismicelemen ll. I horizon

Rcd

y n r iallllvialtolluviolac l strine

Pre collisionpaSS Vc margm

rcctononicevents

^ccrction ofcontinentala g m e n t s

Fig. 2 Generalized a t i g r a p h y and tectonic evolution ofthe Jabung Block Santa Fe Energy Resources Jabung Ltd. 1999)3. lluvial fan facies characteristics anddistribution

Terrestrial sedimentation occurred during the Eoceneage. This filled in the half rift valley and denudationregion locally. As well tuf aceous sandstoneconglomerate breccia and clay-stone filled in grabensand low-lying topography by alluvial fluvial lacustrinesedimentation during the rift valley period.Transgression began in part of the study area during the

Late Eocene and extended largely from Late Oligoceneto Miocene continuously. Petroclastic rocks on thebasement formed overlying deposits and carbonaterocks were developed on tableland as well as on highsof the fault blocks. During sea level fall carbonaterocks experienced weathering and dissolution thenformed secondary holes in ancient highs. Sea floor fansconsisting of petroclastic rocks) were developed in

deep water. The most widespread transgression occurredduring the Middle Miocene and shale as the cap bed of


4/11

Vo 4 No.2 Al luvial Fan Facies and Their Distribution in the Lower Talang Acar Fonnation,Northeast Betara Oilfield, Indonesia 21

Gumai spread widely in the study area. Then elevationand extrusive volcanism began, shallow sea depositsand terrestrial clay-stone were developed (Fig3).Extrusion happened in the northwest direction in the

Western rise

0.5l

5'~ 2.0

2.53.03.5

a r e a Pliocene to Pleistocene, and terrestrialsediments were developed. Subsequently, frequentlyvolcanic activity was found everywhere in the SouthSumatra Basin.

Middle depression Eastern slope E

l mI @o [ jill [Mj5jJUpper Talang kar Forrnation Lower Talang kar Forrnation Gumai n a t i o n irBenakai Formation M u a r a K a FormationFig. 3 Seismic interpretation section in the Jabung Block

There are 6 sets of reservoir bottom to top:1 Basement reservoir beds: Mesozoic uplife , ancienthighs, as well as Eocene cranny or weathered graniteand quartzite, which are good reservoir beds; 2) Lahatreservoir beds: Tuffaceous sandstone, conglomerate andbreccia deposited in faulted or low-lying regions ,which belonged to lake , brackish lake s e d i m e n t a r system; 3) Talang Akar reservoir beds: Sandstone,sandy conglomerate, siltstone, and shale developed inLower Talang Akar Formation, including most1y deltaand river depositional environment system. It is one ofmost important sandstone reservoir beds in the study area,and experienced depositional periods from t1uviallacustrine to early sea transgression; 4) Batu Rajacarbonate rock reservoir beds: Tableland carbonate rockswidely distributed, 18-68 meters thick, and associatedcarbonate swell and organic reefs , 36-110 meters thick;5) Gumai reservoir beds: Fine sandstone and siltstonedistributed along basin margin; 6) Air Benakat reservoirbeds: Formed in the environment of regression, marinefacies sandstone increasing gradually upwards. Theshallow sea and de1ta sandstones are good reservoir beds.

Most of conglomerate o s i t s in bed F at the bottomof the Lower Talang Akar Formation are basalconglomerates o s i t e d on the Pre-Tertiary unconforrnity,and belonging to a terrestrial environment of alluvial fan orbraided river origin. Alluvial fan deposits characteristicsand their planar distribution are discussed as follows.3.1 Lithology characteristics

Bed F in the Lower Talang Akar Formation,

generally speaking, belong to alluvial fan to t1uvialsedimentary environments, in which alluvial fandeposits are characterized by coarse granularity, poorsorting and low reservoir quality. Sand bodiesaccumulate longitudinally, and inter-layers are poorlydeveloped, extending locally in the transverseorientation (Fig. 4).1 Grains characteristics

Poorly sorted sub-round coarse and very coarsesands with small pebbles up to 1 cm are loosely packedin light brown clay (Fig. 5). granite and gneissiccomposite quartz; fragments of well sortedmetaquartzite are more abundant than in other samples;

C h e r t a g m e n t s with quartz veins and pale brownclaystone fragments with radiolarians are also foundhere.

2) Pores cementsRounded pebbles of granite composite quartz (below)and metaquartzite (above) and a few of smaller quartz

grains t10at in pale brown clay matrix, along withsiderite crystals. This is probably paleosol (Fig. 6).

Ductile rock fragments compressed. Single crystalsof siderite with round margins t10ated in matrix.

3) Porosity and permeabilityDue to poor sorting and abundant rock debris ,

bottom conglomerate in Lower Talang Akar F O I n a t i o nhas no good property. Core experiment result of wellNEB 7 indicate change of rock porosity from 2.8 to12.8 and air permeability from O . O l m to

2 5 3 x l 0 with the difference of sorting (Fig. 6).


5/11


1 og curves Physical propertyK mD POR ,

CorephotoGRI , API m l c c I I s f t80 100 10002000 }OOO 1 0 1 02 03

Fig.4 Bottom alluvial fan and its logging response and physical property in the Lower Talang Akar Formation in Well NEB-12

t

07 I 11 1 1 I,1>a, x25, polar b, x25 , X polar

l q j i ? 1 2 : l

c, x25, polar d, x25, X polar 9 I 1 iZ }

Fig. 5 Lithology characteristics of alluvial fans in bed F ofthe Lower Talang Akar Formation in NEB Oilfield(Well NEB 12, 5554.7ft, TVD)

N o t e Top: parti es and their roundness; Bottom: matrix with floating quar z grains and siderite


6/11

23lluvial Fan Facies a n d l e Distribution Lower Talang Acar FormationNortheast Betara Oilfield Indonesia

slate basement Each type of basement has its typicallogging response (Fig. 7).

Vo 4No.2

40MSFL. n l1l I . 3 0 5 1 1 1

2001140

D Carbonate Cranite D SandstoneNotcs: NU l11bcr on thc Ic ft of scction is d ~ p t h .

Fig.7

DST3.DST7 DST6

Strata

TConglomerate structure and its p r o p e characteristic in Well NEB-7

Notes: Left: 5341 5 ft rock debris/pebble located in channel bottom dif erentm b e d E = 1 2 . 8 K . . Right: sorted

erosive structure in alluvial o s i t s top ofbed = 2 . 8 K . . = O . 0 I x l 0 Very poorly sorted alluvial plain wash deposits interval E-water z o n e )

2 . 8 . = 0 . 0 1 X

Fig.6

Pre-Tertiary basement reservoir beds in the SouthSumatra basin Yu et al. 2005

On the above basis bed F in the Lower Talang AkarFormation trace correlation was carried out in thetransverse orientation to confirm distribution of alluvialfan conglomerate in bed F In the research typicallogging response of alluvial fan is summarized (Fig.8)

3.2 Logging response ch r cteristicDue to scarce core materials in the studied area

logging information is the most important data to studydepositional environment and reservoir beds distribution.In order to distinguish bottom conglomerate in the LowerTalang Akar F o r m a t i o n o m the basement firstlylogging responses of different types are summarized andthe basement can be c1assified into sandstone basementgranite basement and carbonate rock basement as well as

NEB-32

iji {

B - 3 4

A \ H J 1 ; ~ ~ ; 1 1 ; ; . \ JJ

F:lij:Alluvial fan logging response characteristics of conglomerate in the Lower Talang Akar Formation in NEB Oilfieldig.8


7/11

4 Petroleum Science 2007and conglomerate is characterized by low GR , lowresistance, high density and low value between DLDand LLD, which reflects poor physical reservoirproperties, coarse lithology and relatively high density.3.3 Distribution of conglomerateOn the basis of logging p o n s e characteristics andseismic property analysis, logging interpretation data wereused c l a s s i f y conglomerate stages. There are 4 stages ofconglomerate recognized in bed F Conglomerates pile upon each other, and the boundary is unclear. There are only2 stages of conglomerate in some other wells. Clay-stoneswere developed between conglomerate deposits, whichwere studied by statistics ofthickness of different stages ofalluvial fans , and the map of conglomerate distribution

c o m p l e t d in the study area.Fig. 9 indicates that conglomerate was developed in

the northeast and middle-south of the study area. The60-70m upper part of bed F) conglomerate was foundin a small area in the middle-south. The 70-80m lowerpart of bed F) conglomerate was developed in arelatively large area in the middle-south. Logging curve

- - ( ) { \ ( ) I

L c g ~ n d

an l l n e linc

Sundstonc d i c t e d a n d S l o n c pr l di t tcdby sC i>n ic by logging dala

analysis indicates that logging response of conglomeratehas clear reflection in the northeast of the study area.There are no useful logging to recognizeconglomerate on the basement in the middle-south ofthe study area, because of the lack of useful GR curveswhich may have been caused by logging techniquelimitations. Therefore, a combination of seismic p r o p e and logging data was used to interpret conglomerates ofF bed area. Only basic interpretation could becarried out, due limitation of seismic informationresolution. The conglomerates of bed F could beclassified into two upper part and lower p a r t l eupper part of bed F is in a limited area, but the lower partis relatively widespread. Fig. 9 and Fig. 10).

Detailed interpretation of alluvial fan conglomerateswas carried out in the northeast area based on loggingcurves. Single c o n g l o m e r a t e i c k n e s s is from 25 to 30and each of them distributes fairly alike. It is manifest thatthe flow direction o southeast to northwest duringsedimentary stages of Fl and F2 , and the flow direction

o southwest to northeast during sedimentary stagesof F3 and F4, which could be recognized by contour ofsandstone thickness Figs. 11-14)

Fig. 9 Distribution ofalluvial fan conglomerate ofupper part F l+F2) ofbed F in the Lower Talang Akar n a t i o n NEB Oilfield


8/11

Vo l.4 NO 2 Alluvial Fan Facies and Their Distribution in the Lower Talang Acar Fonnation, Northeast Betara Oilfield, Indonesia 25

L o go hJl 2 J ]

h o l i e r l 1 1 1 1 S a n d l k ' p r e d l i : m d > k m predirlcd g d a t

Fig. lO i b u t i o n ofalluvial fan conglomerate oflower part F3+F4) ofbed F in Lower Talang ar Fonnation , NEB Oilfield

\ . A n . ~ n O ONLB IOJ NloB , P'. I + . J \ n v Nf l1.1


9/11

26

Petroleum Science

~ 1 f f1 1 - 1 y "

f n ~ 2 : : :

1 0 ' - : 1 1 zB . l h i k

O " ' l . ~ j : - l I l . I ~

I f l . . . j . j t J l 7 3 n \ I H . 2 ( ' O \

- \ ~ 1 - 4 l J ? 1 i r f l J . : J

: < . I l ( I ' \ J . (

I H . '

B

Fig 12 Contour map of a uvial fan conglomerate thickness of F2 in the Lower Talang Akar F ormation NEB Oilfield

1 1 m . ' Wdl

Fig 13 Contour map of alluvial fan conglomerate thickness ofF in the Lower Talang Akar Formation NEB Oilfield

2 7


10/11

Vo 4 No.2 Alluvial Fan Facies and Their Distribution in the Lower Talang Acar FonnationNortheast Betara Oilfield Indonesia 27

Fig. 14 Contour rnap of alluvial fan conglomerate thickness ofF4 in the Lower Talang Akar Formation NEB Oilfield

4. Summary1) Alluvial fan deposits of Bed F in the Lower

Talang Akar Fonnation are characterized by coarsegranularity poor sorting and low reservoir quality. Sandbodies accumulated longitudinally and inter-layerswere poorly developed extending locally in thetransverse orientation.

2) Typical logging response of alluvial fan wassummarized and conglomerate is characterized by lowGR low resistance high density and low valuebetween DLD and LLD which reflect poor physicalreservoir properties coarse lithology and relativelyhigh density.3) Based on logging response seismic p r panalysis and logging interpretation data 4 stages ofconglomerate are recognized in bed F in whichconglomerates pile up on each other and the boundary isunclear. There are only 2 stages of conglomerates insome other wells.

4 Conglomerate was developed mainly in thenortheast and middle-south of the study area. The upperpart of bed F was found in a small area in the middlesouth while the lower part of bed F was developed in arelatively large area in the middle-south.

ReferencesAmbrose W.A. Wang F. P. Akh ter M.S. Skolnakom J. M. M.and Alvarez R. 1 997) Geologic controls on remaining oil in

Miocene transgressive-barrier coastal-plain and mixed-loadf1uvial systems in the Miocene Norte Area Lake MaracaiboVenezuela. SPE 38662 209-218

Cimolai M. P. Gies R. M. Bennion D. B. and Myers D. L. 1993)Mitigating horizontal well fonnation darnage in a lowpenneability conglomerate gas reservoir. SPE 26166 277-287

Durlofsky L 1. 1 992) Modeling f1uid f10w through complexreservoir beds. SPE 21240 373 382

Lu X. G. Sihman M. Bradford W. S. Bambang W. H. andNyoman S. 2004) Integrated reservoir characterization andapproach for improving development dr i1ling of narrowchannel reservoirs within a thin oil rim. SPE 88599 18-20

Salam E. A. Mucharam L. Abdassah D. Budiman P. and PahalaR. P. 1996) Modification of the CVD test approach and itsapplication for predicting gas d e l i v e r i l i t y gascondensate reservoir of Talang Akar Formation in Indonesia.SPE 35648 649-664

Santa Fe Energy Resources Jabung Ltd. 1999) Betara ComplexPlan o Development. 1 36

Si rn10te V. N. Ebanks Jr. W. J Eslinger E. V. and Harpole K. 11 985) Synergistic evaluation of a complex conglomerate

reservoir for EOR Barrancas Fonnation Argentina. SPE11055 295 300


11/11


Tangkalalo D. Ma rufM. F. Sudiono A., and Widjiono P. (1 997)Gas reservoir delineation ofPantai Pakam Timur Field NorthSumatera - Indonesia. SPE 38753 507-520

Wang W. N. Zhang X. Geng X. W. and Chang Q. Z. (1 997)Experimental investigation on the die1 ectric constant of rockswith low porosity and permeability. SPE 30871 115-119Yu H. L. Xue L. Yang F. Z. Hong G. L. and Kong W. (2005)Reef trap and petroliferous t u r e s of Kais Formation in

Island Area Salawati Basin Indonesia. China PetroleumExploration 19(3) 409-415 (in Chinese)Zhang B. Q. Zhang S. Y. Wang B. C. and Zhang W. P. (1 997)The logging technology for determining production profilesthrough casing/tubing annulus in pumping wells. SPE 30868100-105

bout the first author4fh

Xie Chuanli bOm in 1957 graduated with PhD d e g r e eTOngji University in 1998. He nOw isan ass Ociate profess Or and engaged inthe teaching and research indevelOpment ge OlO y in ChinaUniversity Of Beijing102249 China.

E-mail: [email protected] July 9 2006)

Edited by Yang Lei)

N ew Editorial Committee for Petroleum ScienceThe secOnd Edit Orial C Ommittee f Or etroleum Science assumed resp Onsibility On April 18th 2007. PrOf Zhang

Yiwei is the H On Orary Chairman Of the C Ommittee which is fOrmally chaired by Dr Zhang Laibin President Of theChina University Of Petroleum Beijing). Twenty-One academicians and pr Ofess Ors have been app Ointed as adviserstO the C Ommittee. All 68 members fam Ous universities and giant Oil c Orp Orati Ons and Of these 21 membersare fr Om abrOad. Full details are given On the inside c Over Ofthe j Ouma1

Date post:	04-Jun-2018
Category:	Documents
Upload:	weny-astuti
View:	220 times
Download:	0 times

AIIuvial Fan Facies and Their Distribution in the Lower Talang Acar Formation,

Documents