Petroleum Geological Conditions and Exploration Potential Prediction of Deepwater and Deep Formations in the Under-Explored Offshore Indus Basin

The Offshore Indus Basin is located on the western margin of the Indian Plate, adjacent to the onshore Lower Indus Basin in Pakistan and the Kutch Basin along India’s western coast. Deepwater and deep formations in this basin are characterized by low exploration intensity and poor early data quality, which hinder the verification of hydrocarbon potential. Based on newly acquired high-resolution seismic data and onshore–offshore correlation, this study analyzes basin evolution and systematically evaluates petroleum geological conditions and exploration potential of deepwater and deep formations. The results show that the basin has experienced three evolutionary stages: Mesozoic rifting, Cenozoic post-rift thermal subsidence, and passive continental margin development, which collectively control the petroleum geological conditions of deepwater and deep strata. Mesozoic strata (Jurassic and Cretaceous) are widely developed beneath the Deccan volcanic rocks, with a stable distribution. Three sets of potential source rocks are identified: Cretaceous (Type II/III organic matter, high maturity, high quality), Paleo–Eocene (Type III, moderate maturity, high quality), and Lower Miocene (Type II2/III, low maturity, poor–moderate quality). Three sets of high-quality reservoirs are developed: Cretaceous deltaic–shallow marine sandstones, Paleocene reef limestones, and Miocene deltaic and subaqueous fan sandstones. Three hydrocarbon accumulation models are established. Favorable structural belts are mainly distributed in the NW, NE, and SE parts of the basin, dominated by structural and lithological traps. Thin Deccan volcanic rocks in deepwater areas exert a positive effect on the preservation of deep Mesozoic strata and petroleum system development. This study clarifies the key petroleum geological conditions and accumulation rules of deepwater and deep formations, providing a robust basis for hydrocarbon exploration potential evaluation in the Offshore Indus Basin.