Development and Controlling Factors Of Syn Rift Miocene Carbonate Buildups and its Relation to Facies and Reservoir Quality in Banggai Basin, Central Sulawesi

Abstract

In Indonesia and much of SE Asia, some of the largest and most prolific hydrocarbon reservoirs are derived from isolated, shallow-water Tertiary carbonate buildups, including Senoro field, the field of Central Sulawesi of Senoro-Toili block. The depositional history and controls on carbonate growth of the Carbonate reef has been of great interest to geosciences study due to the importance of the carbonate buildup play in Eastern Indonesia. Reservoir quality in the research area appears to change with stratigraphic age with the buildup reef facies having better reservoir quality than the platform facies. In addition, there are reservoir quality differences between fields of similar age. Research area has a typical carbonate reservoir type of play, is located within Batui Thrust Belt. Tectonic activity in the Early Miocene was followed by the development of platform and reefal carbonate of Minahaki and Mantawa Formation. The difference on depositional environment from landward to basinward is shown by the increasing thickness of Mentawa reef carbonate from NE to SW. Transgression related with relative sea level rise in the Late Miocene time resulted to shutdown the development of Mantawa reefal carbonate and subsequently had changed the facies succession into more marine sediments. Facies analysis in a complex depositional environment is have some difficulty in terms of ability to constrain the data available into easily recognizable and reproducible facies types. The objective of this paper are to determine the reservoir facies and diagenetic, to observe the relationship between reservoir properties, to analyze the facies development and diagenetic succession and to determine the depositional model of the Miocene carbonate in Research area, Banggai Basin, based on well and 3D seismic data which indicate two type of carbonate reservoir. i.e: platform and reefal carbonate. The analysis was based on core data from Research area (about 2,000 feet of core from 5 wells). Core analysis and thin section studies show that these isolated carbonate buildups were all deposited as grain dominated shallow water platforms with some differences facies distribution. Reservoir quality can be correlated directly to subsidence rates. Improved age control and facies analysis coupled with 3D seismic imaging and depth volumes have allowed a more detailed interpretation of these carbonate buildups. Age diagnostic, large benthic foraminifera (LBF), planktonic foraminifera, and calcareous nannoplankton enable the correlation of subsurface data and allow high-resolution sequence stratigraphic correlation throughout the research area. Integration of subsurface data leads to more insightful and realistic geological models of subsurface stratigraphy. The sequence stratigraphic development of the subsurface Paleogene in Research area, Central Sulawesi, was defined using well cuttings, core data and wireline logs tied into largely published biostratigraphic and available seismic data. Time equivalent carbonates of the Mentawa member Limestone, showing the same range of environments. On the basis of faunal content, grain types, sedimentary texture, and sedimentary structure, Autochthonous facies types represent reef margin, platform interior, and slope environments ranging from shallow-water, reefal boundstone and rudstone to planktonic foraminifera wackestone and packstone. Allochthonous facies represent grain-dominated, detrital facies types, intercalated within mud-dominated to grain-dominated facies types; rich in planktonic foraminifera, Additional factors with major impact on reservoir quality are frequent and high-amplitude relative sea level fluctuations, ocean currents, and prevailing wind directions. Primary depositional reservoir-quality distribution has been overprinted by diagenetic events, primarily as a result of repeated platform-top exposure and submarine cementation. Diagenetic process indicating creation and destruction of carbonate porosity, due to presence of marine, fresh water, pressure and temperature that present in term of tectonic and subsidence. Some of the micritization, recrystallization, neomorphism.

AAPG Datapages/Search and Discovery Article #90336 ©2018 AAPG Asia Pacific Region, The 4th AAPG/EAGE/MGS Myanmar Oil and Gas Conference, Myanmar: A Global Oil and Gas Hotspot: Unleashing the Petroleum Systems Potential, Yangon, Myanmar, November 13-15, 2018