Play-Based Evaluation on Permian Carbonate Reservoir: Implications for Petroleum Exploration in Northeast Thailand

Abstract

Despite the long exploration history, success rate has been low in the Khorat Plateau region of northeastern Thailand. To date, only two gas fields (from 9 discoveries) have been produced from Permian carbonate reservoirs, the only successful play. PTTEP and Department of Mineral Fuels (DMF) of Thailand conducted a collaborative basin-wide study using a Play-Based Exploration (PBE) method to fully understand the remaining prospectivity. PBE combines all aspects of petroleum system to provide a holistic view on basin prospectivity. It integrates existing knowledge in literature with well failure analysis, well-seismic stratigraphy, reconstruction of paleogeography and depositional environments, structural interpretation and restoration, source rock characterization and 1D basin modeling into a comprehensive basin development model. The outcome from these analyses coupled with better understanding of the basin were used to generate common risk segment maps of key elements in the petroleum system. The common risk segments maps were combined into the total chance map, which was then used to identify play fairways. Two major rifting episodes during Carboniferous-Triassic and three compressional events during the Triassic and Paleogene resulting in closures of the Paleo- and Neo-Tethys Oceans were responsible for the complex tectono-stratigraphic history of this area. The deposition of marine source rocks and carbonate reservoirs were influenced by the Late Carboniferous to Permian rift structures. The Triassic and Paleogene compression subsequently created prospective structural traps as well as modified local reservoir qualities via fracturing and hydrothermal processes. The Permian carbonate reservoirs are sealed by a widely distributed Upper Triassic fluvial floodplain sediments. Play chance shows that the exploration sweet spots are related to karst features and fractures mainly in the western and north-western parts of the Khorat Plateau. Further detailed study and prospect level evaluation planned for these fairways. Identifying and delineating the karst features and fractures are key to success in future exploration. Additional infill seismic data will also help in achieving the goals.