FACIES DEPOSITIONAL ENVIRONMENT AND SEQUENCE STRATIGRAPHY OF THE TALANGAKAR FORMATION IN THE LMN FIELD - CIPUNEGARA SUB-BASIN, NORTH WEST JAVA BASIN: IMPLICATIONS TO SUPPORT EXPLORATION

摘要

This research is located in the LMN Field in Cipunegara Sub-basin, North West Java Basin which has been widely known as one of the most prolific hydrocarbon provinces in Indonesia. The research has been conducted to analyze the facies depositional environment and stratigraphic sequences of the Lower Cibulakan Formation (eq. Talang Akar Formation) integrated with various types of subsurface data: mudlogging, wireline logging, petrographic and biostratigraphy. Regional stratigraphy conducted by Arpandi and Padmosukismo in 1975 mentioned that the research area is started with Eocene-Oligocene volcanic of Jatibarang Formation (NP20) deposited in terrestrial environment followed by Early Oligocene to Late Miocene - Lower Cibulakan Formation (P18-N5) deposited in fluvial-transition environment then Early Miocene limestone of Mid Cibulakan Formation (N5-N11) deposited in shallow marine environment. The main structural trend in the research area is oriented North - South, parallel to a regional structural trend in North West Java Basin. Based on the analysis of lithology, electrofacies, biostratigraphy, facies depositional environment and sequence stratigraphy, the deposition mechanism on the area is related with transgressive system tract indicated by a predominantly shale layer in the observed wells. The results showed this area was deposited in estuarine environment, with associated facies amongst others are : salt marsh, mud flats, mix of flats and mud shelf during Early Oligocene to Late Miocene (P18-N15). There are 4 sequences with 11 system tracks that can be recognized as Lowstand System Track (LST), Transgressive System Track (TST) and Highstand System Track (HST) where are bounded by a Sequence Boundary. Also, other boundaries such as Maximum Flooding Surface and Transgressive Surface can be recognized.