SEQUENCE STRATIGRAPHY ANALYSIS AND POROSITY DELINEATION OF CD CARBONATE UNIT AT KETAPANG AREA, MADURA NORTHERN OFFSHORE, NORTH EAST JAVA BASIN
BT field is one of the discovery in the Ketapang area that was discovered in the 2000s. Hydrocarbon test result from several wells within the field ranges from 2000 to 3000 BOPD from CD Carbonate unit. In 2010s, hydrocarbon was discovered at BTS prospect with BTS-1 well test result ranges from 400 t...
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Format: | Theses |
Language: | Indonesia |
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Online Access: | https://digilib.itb.ac.id/gdl/view/17059 |
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Institution: | Institut Teknologi Bandung |
Language: | Indonesia |
Summary: | BT field is one of the discovery in the Ketapang area that was discovered in the 2000s. Hydrocarbon test result from several wells within the field ranges from 2000 to 3000 BOPD from CD Carbonate unit. In 2010s, hydrocarbon was discovered at BTS prospect with BTS-1 well test result ranges from 400 to 600 BOPD from the same Carbonate unit. The discrepencies of the test result incurred queries on the similarity between BT field and BTS prospect. Sequence stratigraphy analysis is expected to be able to understand the carbonate development of CD Carbonate unit within the research area.
Data used for this research are full stack cube of 3D seismic PSDM data, wireline logs and mudlogs. Other data that wee used for this research are core, side wall core (SWC) and drilling cuttings sedimentology description, petrography description and biostratigraphy description. Sequence Boundary (SB) determination at each wells was conducted by seeking the karstification features on the interpreted core barrel, SWC and drilling cuttings combined with wireline logs data. Well correlation was conducted to build the geological model used as the guidance for seismic interpretation. Seismic stratigraphy analysis was conducted by referring to the geological model generated from well correlation and tied to seismic data. Depth structure maps were generated from the seismic interpretation results and continued with isopach maps generation. Acoustic
Impedance (AI) inversion data was used to assist the delineation of porosity distribution.
Sequence stratigraphy analysis using well data was able to identify 4 SB, while seismic stratigraphy analysis was able to identified 3 SB. CD Carbonate were devided into 3 deposition cycle which were bounded by SB 1 to SB 2, SB 2 to SB 3 and SB 3 to SB 4. SB 2, SB 3 and SB 4 events caused the forming of karstification zones with variation of thickness. SB 3 and SB 4 showed the lateral change of karstification where a more intensive karstification identified at the northern side of the area in BT-3A, BT-2 and BT-4 wells and relatively decreasing to the south at BTS-1 well area. CD Carbonate developed on a North East-South West trend high in a form of a big isolated platform. During a cycle when SB 1 and SB 3 deposited, area near BT-2 and BT-3 well was a lagoon/interior platform area while area near BT-4, BT-1 and BTS-1 well was reef area. During the SB 3 there was a relative sea level fall causing area near BT-3A, BT-2, BT-4, BT-1 and BTS-1 wells exposed to the surface and allowed the karstification to happen. At the same time horizon 3 was deposited at the southern past of the resarch area. In a cycle between SB 3 and SB 4, horizon 4 was deposited and it was part of back steping process in the Transgressive System Tract (TST). The area covered by horizon 4 are near BTS-1, BT-4 and BT-1 wells. During this period, the area near BTS-1 well was a shelf edge or reef. Meanwhile the area near BT-2 and BT-3A wells was a land which was proven by the existance coal/black shale at both wells. When SB 4 was deposited, area near BT-2 and BT-3A well was a platform interior while area near BT-4, BT-1 and BTS-1 was a shelf edge or reef. A generated porosity map shows a more porous area at the northern side of research area. This condition confirm that the development of porosity was controlled by karstification due to higher northern area compared to southern area. |
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