Mesozoic structural characteristics and exploration potential of the offshore Indus Basin

Due to the lack of drilling confirmation and the poor imaging quality of the early seismic data in deeper part, there was a great controversy on the understanding of the strata under the Cenozoic in the offshore Indus Basin: some scholars thought that the Deccan volcanic rocks were widely distributed; It is also believed to be Mesozoic sedimentary strata, but its stratigraphic framework, distribution and structural characteristics are not clear. This directly affects the evaluation of exploration potential in this area. Using the latest multi-channel seismic data, we have clearly identified Mesozoic sedimentary strata in the offshore Indus Basin. The offshore Indus basin is composed of the underlying Mesozoic rifting basin and the overlying Cenozoic passive continental margin sedimentary basin. It is a two-stage superimposed basin developed on the stretched and thinned crust of the Indian plate, drifting from the southern hemisphere to the present position together with the Indian continent. Through correlation of sea and land strata, it is found that the Mesozoic offshore Indus Basin is an offshore extension of the lower Indus Basin, and has similar stratigraphic distribution characteristics and structural characteristics to the lower Indus Basin. The correlation of seismic wave sets indicates that the Jurassic, Sembar Formation and Lower Goru Formation of Lower Cretaceous and the Upper Goru Formation of Upper Cretaceous were also deposited in the sea area. The Jurassic and Lower Cretaceous have the stratigraphic characteristics of eastern faulted and western overlapped, and the Upper Cretaceous has the characteristics of east-west double faulted. The basin rifting area expanded westward continuously during the Mesozoic. The Mesozoic strata were controlled by nearly N-S trending faults，the northern near-shore strata partially reformed by Cenozoic near E-W fault, and the western strata was influenced by the near N-S uplifting and strike-slip structure of Murray Ridge. The average thickness of Mesozoic strata is about 2000m, and the thickest can reach 12000m. The Mesozoic major depocenter is located in the southeast of the basin, the second one is in the northwest. The favorable structural types such as faulted nose, faulted anticline and anticline are mainly developed. These structures were mainly formed during the late Mesozoic compressive uplift period. Therefore, the Mesozoic in the Offshore Indus Basin has the material basis and structural geological conditions for the formation of oil and gas fields. If the favorable structure in Mesozoic can be configured with the depocenter, it will be conducive to hydrocarbon near-source charging. Like the Lower Indus Basin, the Mesozoic is also a favorable direction for petroleum exploration.