A preliminary analysis of natural CO2-saturated gas sands distribution in the Gemah Field-Jabung Block, South Sumatra Basin, Indonesia, by using simple seismic attributes

Abstract

The discovery of CO2-saturated gas in sandstone reservoirs of the Lower Talang Akar Formation (LTAF) in the Jabung Block of South Sumatra Basin is a significant exploration risk that affects development plans. Gemah Field is one of the fields that produces CO2-saturated gas in the area. The field has several oil rims that can be optimized for production by using carbon capture, utilization, and storage (CCUS) enhanced oil recovery (EOR). This paper discusses a preliminary analysis of the natural CO2-saturated gas sands distribution in the FS3 interval of Gemah Field by using simple seismic attributes. The results can be used for guiding the feasibility analysis of CCUS-EOR implementation and mitigation of drilling risk of subsequent developments wells. Poststack seismic attributes and inversion analysis were performed and constrained by data from 64 wells in the FS3 interval. Although these two methods give similar distribution of sandstone reservoirs, this study finds that the sum of negative amplitude (SNA) attribute is better because there is a linear relationship between SNA with sand thickness and CO2 saturation. High CO2 saturation gas reservoir zones are observed along the highly faulted areas. CO2 saturation decreases away from the faulted areas and follows the northeast–southwest direction of reservoir deposition. The identified high CO2 regions can be considered as zones of potential CO2 sources for CCUS-EOR. The low CO2 areas are a potential location for a subsequent drilling well to obtain cleaner gas reservoirs with low CO2 saturation.