Breakthrough and potential of natural gas exploration in multi-layer system of Penglai gas area in the north of central Sichuan paleo-uplift

In recent 3 years, breakthroughs have been made in exploration of Member 2 and 4 of Dengying Formation of Upper Sinian in Sichuan Basin, Member 1 of Canglangpu Formation of Lower Cambrian, and Member 2 of Maokou Formation of Permian in the north slope of the central Sichuan paleo-uplift. After the discovery of Anyue gas area, a new large gas area of trillion cubic meters, namely Penglai gas area, has been formed. Under the joint control of large extensional strike-slip faults, paleo-taphrogenic trough and platform margin zones, multi-layer large-scale source rocks, reservoirs and fault-controlled lithologic traps are vertically developed upwards in Penglai gas area; the good source-reservoir configuration and vertical transport pathways promote the efficient filling of multi-layer oil and gas; the tectonic evolution of "ancient uplift and present slope" ensures the efficient accumulation of oil and gas; the development of direct cap rocks and regional cap rocks in the multilayer system provides good conditions for hydrocarbon preservation. Thanks to the good spatio-temporal collocation of accumulation elements, the Sinian-Permian system in Penglai gas area has formed a unique three-dimensional accumulation model of deep, ultra-deep, multi-layer and marine carbonate rocks in the slope area, i.e., "three-dimensional hydrocarbon supply, three-dimensional reservoir formation, three-dimensional transportation, early oil and late gas, three-dimensional accumulation". The breakthrough in the natural gas exploration in multi-layer system of Penglai gas area can not only greatly expand the exploration of deep and ultra-deep natural gas in Sichuan Basin, but also prove that after multi-period tectonic movements, the ultra-deep and ultra-old strata at the slope of the ancient uplift still have the potential to form large-scale natural gas accumulation, which is of great significance for guiding the further exploration of ultra-deep natural gas in Sichuan Basin.