TECTONIC EVOLUTION AT MUSI HIGH AND ITS INFLUENCE TO GUMAI FORMATION AS ACTIVE SOURCE ROCK AT SOPA FIELD, SOUTH SUMATERA BASIN
Shale from Lahat and Talang Akar Formations were widely accepted by many geoscientists as general source rocks in Palembang sub-Basin. The oil from Sopa Field was considered as hydrocarbon accumulation that had been migrated from local and regional deeps around Sopa Field, where Lahat and Tala...
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Format: | Theses |
Language: | Indonesia |
Subjects: | |
Online Access: | https://digilib.itb.ac.id/gdl/view/73350 |
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Institution: | Institut Teknologi Bandung |
Language: | Indonesia |
Summary: | Shale from Lahat and Talang Akar Formations were widely accepted by many
geoscientists as general source rocks in Palembang sub-Basin. The oil from Sopa
Field was considered as hydrocarbon accumulation that had been migrated from
local and regional deeps around Sopa Field, where Lahat and Talang Akar
Formations were deposited.
Based on subsurface physiographic that was obtained from integration of
interpretation of well and seismic data, the closest deep is more than 20 km,
therefore it is difficult to explain hydrocarbon migration mechanism from kitchen
to reservoir. Besides that, Sopa Field is located at paleohigh since Eocene to
Middle Miocene, consequently Lahat and Talang Akar Formations were not well
developed. With these facts, reservoir carbonates of Baturaja Formation were
deposited directly on the top of pre-Tertiary basement.
This thesis is directed to obtain information of other formation potential as a
source rock that charge hydrocarbon in Sopa Field, which is Gumai Formation.
Not only act as regional seal in South Sumatera Basin, Gumai Formation may also
act as active source rock, therefore this hypothesis must be proven with analytical
geologic in a simple model.
The result of comprehensive geochemical analysis shows that oils at Sopa wells
migrated from source rock that had been deposited at transition environment. Oil
from Sopa is correlated with bitumen that was extracted from sediment sample of
Gumai. The sample of Gumai Formation was deposited at lagoon environment.
On the other hand, extracted bitumen of Baturaja Formation sample was analyzed
as non-indigenous or has been migrated from other sources. Therefore, the
bitumen for sample of Baturaja Formation was not valid for further analysis.
Seismic data interpretation is transformed into a geology model that will give
explanations of maturity and migration mechanism of shale in Gumai Formation.
Tectonic evolution at South Sumatera Basin since Middle Miocene to recent time,
had been forming a massive number of thrust faults that make some blocks
becoming higher, while the other was buried deeper. Some part of Gumai
Formation at fault’s footwall was reached maturation zone. These tectonic
evolutions was also made carbonate reservoir became tilted, therefore it helped
hydrocarbon to move from the lower part to the shallower part. Hence, Gumai
Formation is also acting as active source rock at Sopa Field.
Gumai Formation has been proved as active source rock at Sopa Field, and it may
open the new vision of hydrocarbon exploration with the same play. The model
that was resulted from this thesis, may be used as an analog to define a source
rock that younger than its reservoir. |
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