AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Facies Analysis and Sequence Stratigraphy of Tertiary Carbonates: Integrating Subsurface and Outcrop Data from the Cepu Block and Rajamandala Outcrops, Java, Indonesia
(1) Mobil Cepu Ltd. (MCL), Jakarta, Indonesia.
(2) ExonMobil Oil Indonesia (EMOI), Jakarta, Indonesia.
(3) Institute of Technology Bandung (ITB), Bandung, Indonesia.
(4) ExxonMobil Upstream Research Company (URC), Houston, TX.
The difficulty with attempting a quantitative analysis of facies in a complex depositional environment is the ability to constrain the data into easily recognizable and reproducible facies types. One of the most challenging environments is the shallow water carbonate depositional system. Using subsurface and outcrop data, a facies atlas for Tertiary carbonates of Southeast Asia was established to allow reproducible facies descriptions by multiple workers. The analysis was based on core data from the Cepu Block, East Java Basin, Indonesia (about 2,000 feet of core from 5 wells) and four outcrop cores (about 1,200 feet), recently drilled into the Rajamandala Limestone close to the city of Bandung (West Java, Indonesia).
Tertiary subsurface carbonates of the Cepu Block, range in age from Late Middle Eocene to Early Miocene and are comprised of diachronously deposited shallow water isolated carbonate build-ups and associated deeper water in situ and detrital (calciturbidites and debrites) carbonate sediments.
Time equivalent carbonates of the Rajamandala Limestone, showing the same range of environments, are well exposed in the vicinity of Bandung (Cikamuning and Batu Nunggal areas).
On the basis of faunal content, grain types, sedimentary texture, and sedimentary structure, fourteen autochthonous and five allochthonous (detrital) facies types have been identified. Autochthonous facies types represent reef margin, platform interior, and slope environments ranging from shallow-water, reefal boundstone and rudstone to deeper-marine planktonic foraminifera wackestone and packstone. Allochthonous facies types represent slope to basinal, grain-dominated, detrital facies types, intercalated within mud- to grain-dominated facies types; rich in planktonic foraminifera.
Age diagnostic, large benthic foraminifera (LBF), planktonic foraminifera, and calcareous nannoplankton enable the correlation of outcrop data to subsurface data and allow high-resolution sequence stratigraphic correlation throughout the Cepu Block.
Integration of subsurface and outcrop data leads to more insightful and realistic geological models of subsurface stratigraphy.