Facies Characterization and Depositional Environment Relationship of Miocene Carbonates Reservoir in S Field, Central Sulawesi

Abstrak

Senoro gas field with 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.
Two main carbonate facies had been recognized across the area, which are the coral reefal buildup facies and platform facies. The platform facies is predominantly consists of muddy wackestone/packstone facies with unsignificant porosity development. The reefal build-up facies consists of Grainstone/Floatstone facies with more typical of reefal organism such as coral growth. The deposition of downslope distal facies consists of several coral-algal fragment was also developed adjacent to the area where reefal buildup grows. Most of the porosity in buildup facies are secondary vuggy and mouldic pore type of leached coral-algal framework, while in platform facies are fracture and vuggy porosities.
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.