INTERPRETASI LINGKUNGAN PENGENDAPAN FORMASI TALANG AKAR BERDASARKAN DATA CUTTING DAN WIRELINE LOG PADA LAPANGAN X CEKUNGAN SUMATERA SELATAN

Abstract

A sedimentary environment is a part of earth’s surface which is physically, chemically and biologically distinct from adjacent terrains (Selley, 1988). The study of the depositional environment is one goal of many studies conducted for academic purpose and economically purpose in oil and gas exploration. The study of the depositional environment requires a fairly comprehensive analysis as to sequencestratigraphy facies analysis to obtain detailed interpretations or conclusions. The purpose of this study is to analyze cutting and wireline logs to determine lithology, facies and sedimentation history of theTalang Akar formation field X in South Sumatra basin. The method used to analyze the formation of depositional environment of Talang Akar field X in South Sumatra basin is the cutting description in order to know the composition of the constituent formations. While the analysis conducted is cutting analysis to get lithofacies interpretation, second is well log analysis method to get subsurface data such as physical rock properties then electrofacies analysis based on gamma ray log pattern and third is stratigraphy sequence analysis method so sea level changed can be known. Stratigraphy sequence interpretation did base on facies and gamma ray log pattern changed. Pratama-1 well lithology consists of shale, siltstone, very fine sandstone until medium sandstone and limestones. While the well lithology Pratama-2 is composed of shale, very fine until medium sandstone and siltstone. Facies found in wells Pratama-1 consists of distributary channel fill, prodelta, distal bar, distributary mouth bar, and marsh. Facies in wells Pratama-2 is a mud flat and mixed flat. In Pratama-1 wells are 2 sets sequence that bounded by 2 sequence boundary, with a stratigraphic unit LST, TST and HST with progradation and retrogradation stacking patterns. While the Pratama-2 wells contained one stratigraphic unit sequence that is only TST in progradation and agradation stacking patterns. Based on this analysis the Talang Akar formation field X in South Sumatra basin has a transitional depositional environment. Keywords: Talang Akar formation, cutting description, electrofacies analysis, transitional depositional environment