Paleoenvironment and Petroleum Potential of the Lacustrine Shales in the Lower Cretaceous Shahezi Formation of the Southern Songliao Basin, NE China

The occurrence of conventional and unconventional hydrocarbons is directly determined by organic matter (OM)-rich shales in fault-controlled sedimentary basins. Through integrated analyses of organic petrology, element concentrations, bulk organic geochemical characteristics, hydrocarbon generation, and expulsion of the Shahezi shales, we have conducted comprehensive studies on the paleoenvironment, OM source, and petroleum potential of the Shahezi shales: 1) the Shahezi deposition occurred under a cold and semi-humid to semi-arid paleoclimate, and sub-reducing to reducing redox conditions, favourable for OM preservation; 2) the OM origins of shales are primarily a mixture of aquatic microorganisms and terrestrial higher plants; 3) the shales demonstrate a fair to excellent source rock potential; 4) oil generation began around 130 Ma, while gas generation started around 105 Ma; 5) the shales have reached the hydrocarbon expulsion threshold; 6) the occurrence of burial-deep tight gas reservoirs, is predominantly controlled by the outer boundary of the shale distribution. [Received: December 29, 2023; Accepted: January 24, 2024]