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2.1 SUMMARY OF THE GELAMA MERAH FIELD
Geological Area : Sabah Basin
Area : Offshore Sabah
Country : Malaysia
Reservoir Structure : Anticlines
Coordinate : Longitude 114 !"# $%&'4#(
: Latitude $! ''# 4"&")#*
+y,e of -ield : Oil and gas
2.2 INTRODUCTION
2.2.1 REGIONAL SETTING
Gela.a Merah field is located in the offshore of Sabah Basin& /t 0as believed that the
field is located nearby the Se.arang Asa. aya roduction Sharing Contract 0hich in (ast
Malaysia at Sabah offshore& +his field 0hich is about 4! .iles 235.6 north0est of theLabuan Gas +er.inal is surrounded by shallo0 reed 0ith the 0ater de,th of '$ feet 2".6&
+he location of the Gela.a Merah field is sho0n in the figure belo0& Sabah7 located in the
northern ,art of Borneo7 lies at an i.,ortant 8unction bet0een the (urasian7 /ndo9Australian7
acific and hili,,ines Sea ,lates& +he Sabah Basin7 0hich is located in *orth est of Sabah7
is .ainly offshore 0hile the other t0o basins cover so.e areas in the *orth (ast and South
(ast of onshore Sabah& +he Sabah Basin contains 195. thic5 *eogene sedi.ents that 0ere
de,osited 0ithin the dee, .arine and ,rogradational shelf slo,e environ.ent& +here are si;
tectonostratigra,hic ,rovinces are identified in Sabah Basin 0hich is Ra8ang Grou, -old9
+hrust Belt7 /nboard Belt7 Bara.
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-igure 1&1 = Location of Gela.a Merah field
+he Geogra,hical Coordinate of Gela.a Merah is $! ''# 4"&") *7 114 !"# $%&'4(&
+here are three 0ell on Gela.a Merah field 0hich is Gela.a Merah 17 Gela.a Merah S+91
and finally Gela.a utih& +he last and .ost recent tie9in to Sa.arang Asa. aya SC is
fro. the nearby Su.anda5 field& +he fault that is occurred in Gela.a Merah is regional
0rench fault&
&1&1 late +ectonic Syste.
+here are four .a8or tectonics event occurred in Sabah Basin that contribute to the
fault align.ent> 16 develo,.ent and de,ositional during syn9riff ,hase2(ocene =Oligocene67
6transgression of deltaic de,osits of during late syn9riff ,hase2Late Oligocene9(arly
Miocene67 '6 .ar5ed by tectonic ?uiescence during Middle Miocene7 and 46 /nversion and
folding of tectonics during Middle Miocene9leistocene&
+he tectonic setting and basin evolution of the Sabah Basin is very .uch related to
the closing of the ,roto9South China Sea@ Ra8ang Sea& +he o,ening of the South China Sea
since Oligocene causing .icrocontinents of
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-igure &1& = +ectonic (vent of Sabah Basin
2.1.2 Exploration Opportuniti!
+he e;,loration of Sabah Basin 0as carried out by nu.erous ty,e of oil co.,anies& A
nu.ber of initiatives by (+RO*AS and SC contractors to test ne0 ,lay9ty,es and
continuous studies to .ature ,lays have resulted in recent discoveries& +he success story
begins 0ith the discovery of Gela.a Merah by Gela.a Merah 1 0ere drilled in Se,te.ber
$$1& +hen7 seven .ore e;,loration 0ell 0ere drilled on the sa.e ,lay in the area bet0een
$$1 until $$'&
+o date7 t0enty9eight 2)6 develo,.ent 0ells have been drilled on Gela.a Merah
area and the fields are currently on ,roduction& /n order to further e;,lore the hydrocarbon
,otential of this area7 a regional study 0ith se?uence stratigra,hic a,,roach 0as carried out in
$$)& +he .ain ob8ective of this study is to generate stratigra,hic fra.e0or5 of Su.anda5
that can be correlated to the Sabah regional chronostratigra,hic fra.e0or5&
+he generated stratigra,hic fra.e0or5 0ill hel, to facilitate inter,retation in the
Bloc5 SB'1$ and surrounding areas& /n addition7 the study 0as also ai.ed to identify any
u,side hydrocarbon ,otential for further e;,loration& +he a,,roach ado,ted in this study 0as
based on (;;on#s techni?ues 2an agoner et& al& 1""$6 0hich defined Se?uence Boundary
2SB6 as a ,roduct of relative falls is sea level&
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Seis.ic data and 0ell data 2logs7 cores biostratigra,hic data 0ere used to identify
.a8or bounding surfaces in order to establish a fra.e0or5 in 0hich genetically related facies
can be studied and a realistic de,ositional .odel can be constructed&
2.2 2"DIMENSIONAL CROSS IMAGING
Contour line that is in surface .a, indicate the de,th of the area fro. to, vie0&
Contour lines connect all the sa.e elevation ,oint and are used to illustrate relief on a .a,&
Contour .a,s for e;,loration .ay de,ict geologic structure as 0ell as thic5ness of
for.ations& By this contour7 the angle of a fault and 0here it intersects 0ith the for.ations
and other faults as 0ell as 0here the for.ations ta,er off or sto, abru,tly can be sho0n&
Basically7 geologist used iso,ach .a,s to assist in e;,loration 0or5 0hich is to calculate ho0
.uch ,etroleu. re.ains in a for.ation and to ,lan 0ays to recover it& +he range of de,th
that ,lotted on to, of .a, is 0ithin 1'$$91)$$.& +here are a total of " layers of surface .a,
0hich are '&7 4&$7 !&$7 %&$7 3&$7 )&$7 "&$7 "&1 and "&& +he .a,s 0ere scaled
as 1:!$. 0hich is in A' siDes& An identical scale of horiDontal and vertical are
reco..ended for conventional cross section i.aging as sho0n belo0&
ertical (;aggeration 2(6 E value of one unit .easure.ent on the ForiDontal 2MA6scale
value of the sa.e unit of .easure.ent on the ertical D
E 1:!$ E 1
1:!$
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Fi#ur 2.1= Surface .a, for nit '&
+he de,th of cross section 0as dra0n to visualiDe the contour line in t0o di.ensional
vie0s that is obtained fro. the surface .a,& +he vertical and horiDontal cross sections 0ere
both ,lotted using Microsoft (;cel& +he ;9a;is re,resents the horiDontal line 0hile the y9a;is
re,resent the thic5ness of each Done&
+he ater Oil Contact 2OC6 is found to be at 1!'!. +
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2.$ %ETROLEUM SYSTEMS
&'&1 Source Roc5
Success in the ,reservation of organic .atter in the * Sabah Basin see.s to be
related to the high ,ri.ary terrigenous ,roductivity7 high sedi.ent accu.ulation rates and the
resistant nature of the +y,e /// higher land ,lant 0a;es to o;idation and biodegradation&
/nterestingly7 as .uch of the Sabah shelf tended to be o;ic during Middle Miocene7 it a,,ears
that ano;ic de,ositional conditions 0ere not essential for organic .atter ,reservation& /n
origin7 de,osited in generally o;ic environ.ents such as deltaic@,eat s0a.,s7 brac5ish
.angrove s0a.,s and lagoons&
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&'& Migration
+he ti.ing of .aturation varies fro. Middle Miocene to the ,resent& Most of the area is still
undergoing subsidence& Migration along faults is ,robably a .a8or .ethod of .igration
though .any faults act as seals& So.e .igration through sedi.entary facies has ,resu.ably
occurred7 es,ecially in an u, di, direction fro. condensed intervals&
&'&' Reservoir Roc5
Reservoir roc5s for Gela.a Merah field consist of interbedded sandstone 0ith thin shales
layer of non9reservoir& ,,er shoreface sandstones of regressive ,arase?uence sets and
fluvial and tidal sandstones filling incised valleys cut during lo0stands& +he de,ositional
environ.ents for each sandstone reservoir differ 0ith the stratigra,hy& +he ,ri.ary
de,ositional environ.ent7 burial diagenesis and .ineralogical contents of the reservoirsandstone ,lay an i.,ortant role in the ?uality of the reservoir in Sabah Basin& -or.ation that
0as de,osited during .iddle to u,,er Miocene contains reservoir roc5s that are de,osited in
fluvial9deltaic7 coastal ,lain and shallo0 .arine environ.ent 2Madon M&7 1""46& +hese strata
contains .ediu. to very fine grained sandstone 0ith ,orosity value that .ore than '$H and
1$$$.< ,er.eability value 2Bisho,7 $$6&
&'&4 +ra, Seals
Most ,roducing reservoirs are anticlinal features& +his can be sho0n through the horiDontal
cross of the contour .a, in -igure &'& Based on the location of basin it is either rollover
anticlines ,roduced by gro0th faulting or anticlinal features associated 0ith .orris faults&
So.e reservoirs are related entirely to sealing against faults& +he seals are either .arine
flooding surfaces or faults 0ithin reservoirs& -urther.ore7 there are also stratigra,hic tra,s
unrelated to anticlinal features according to the basin 0here the Gela.a Merah located&
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-igure &' = ForiDontal Cross Section
2.& Strati#rap'( an) Corrlation
+he correlation is done across 0ell Gela.a Merah91 2GM916 to 0ell Gela.a Merah91 S+1
2GM91 S+16& +o, and base sand unit correlation data are given for GM91 and GM91 S+1&
Iuality chec5 of ga..a ray log res,onse is being used in order to identify the lithology of
the for.ation& Sand and shale unit identification is done using ?uic5 loo5 .ethod& -igure &4
illustrates the stratigra,hic correlation fro. sand and shale distribution fro. the log res,onse&
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GR: Lo0 2clean
for.ation6 9
indicate sand
for.ation&
GR: Figh
2radioactive
for.ation69indicate
shale
GR: /rregular readings 2lo0
high69indicate sand
for.ation
interbedding 0ith
shale layers
GR: /rregular readings
2lo0 high69indicate sand
for.ation interbedding0ith shale layers
GR: Lo0 2clean for.ation6
9 indicate sand for.ation&
GR: /rregular readings
2lo0 high6 9 indicatesand for.ation
interbedding 0ith shale
GR: Figh 2radioactive
for.ation69indicate shale
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-igure &4 : ell to, correlations using Ga..a ray log for GM91 and GM91 S+91
/t can be seen that the oil accu.ulation are distributed at a thic5 layer at Done "&$7 "&1 and
"& as sho0n in the .ulti9layered reservoir in -igure &'& +he thin oil layered are sho0ed
above the GOC is at Done '&7 !&$ and "&$ above the GOC level& tectonic .ight have
caused another ,ossible u,lift that gives the Gela.a Merah the current anticlinal sha,e it has
no0& +he hydrocarbon bearing reservoirs in Gela.a Merah area are re,resented by to,set