3D Facies Modelling of Tuban Formation, North East Java Basin

Abstract

Summary Based on the BP Statistical Review of World Energy 2021, at the end of 2020 Indonesia’s proven oil reserves are still around 2.4 thousand million barrels. Indonesia’s average daily oil production is 743 thousand barrels, while the average daily demand for oil is 1449 thousand barrels. In fact, the oil and gas reserves have not met the energy needs in Indonesia. Therefore, it is necessary to optimize the utilization of one of the productive marginal oil and gas fields by building a 3D facies model approach as a reference to increase production in S Field. 3D facies model is a computational depiction of the earth’s crust based on petrography analysis, electrofacies analysis, well correlation, facies association analysis, structural modelling and variogram analysis. The aim is to determine the type of platform, lithofacies, depositional environment and facies distribution in S Field. Geologically, S Field is an oil field located in the Tuban Formation, North East Java Basin. The Tuban Formation is a carbonate build-up that has grown since the Early Miocene with a depositional location in the form of an Isolated Platform. Based on petrographic analysis, the Tuban Formation consists of 3 lithofacies including Skeletal Grainstone, Skeletal Packestone, and Skeletal Wackestone which are physiographically associated with Fore Reef and Inter Reef ( Enos and Moore, 1983 ). 3D modeling of carbonate rock facies was built using the Truncated Gaussian simulation (TGS) with trend method. TGS method is a stochastic facies modeling method that is suitable for modeling reservoir units or facies that have natural sequences (Matheron et al., 1987). This sequence can be either a reservoir quality sequence or a stratigraphic sequence, either vertically or laterally. Based on the results of 3D modeling of carbonate rock facies, the facies association of Fore Reef is in the middle as an elongated shelf in the west-east direction, which is dominated by Skeletal Grainstone and Skeletal Packstone as carbonate peaks in the S Field, while the facies association of Inter reef is the result debris or detritus from the Fore Reef in the slope transition area.