The Songliao Super Basin in northeastern China
Bo Liu, Lingbo Liu, Jian Fu, Tiefeng Lin, Junling He, Xingzhou Liu, Yuchen Liu, Xiaofei Fu
Abstract
Abstract With several superimposed petroleum systems and a proven reserve of 200 billion bbl of oil and 160 TCF of gas, the Songliao Basin in northeastern China is considered a super petroliferous basin. This paper outlines the basin’s tectonic units, its tectono-stratigraphy, and the essential elements of each petroleum system and reviews the distribution of hydrocarbon plays and opportunities for future unconventional shale oil exploration. The Songliao Basin developed during an Early Cretaceous rifting event that resulted in localized petroleum systems with the limnic, swampy, coal-bearing Shahezi shale as the source rock for 156.4 TCF of gas discovered in synrift volcaniclastic reservoirs. Continued thermal subsidence during the Late Cretaceous resulted in two rapid flooding events, which resulted in the deposition of the organic-rich Qingshankou and Nenjiang Formations. The first member of Qingshankou shale (K2qn1), with a total organic carbon content ranging from 1 to 7 wt. % and a thickness of 50 to 100 m (165 to 330 ft), reached the oil window at 80 Ma and is the dominant source rock for the 103 billion bbl of oil and 4.4 TCF of gas discovered in sag-phase reservoirs. A total of 5 regional seal rocks and 10 stacked potential reservoir units have been identified within the basin, forming 5 hydrocarbon accumulation intervals from bottom to top: deep gas plays in the rift-phase sequence, lower, middle, and upper petroliferous plays in the sag-phase sequence, and shallow gas plays formed during the basin inversion phase. Additionally, shale oil is currently being produced from K2qn1, with estimated oil reserves of 95 billion bbl. The exploration history of the basin has evolved through structural traps, structural-stratigraphic composite traps, stratigraphic and volcanic traps, and unconventional reservoirs. After more than 60 yr of production, the basin still has significant potential for enhanced oil recovery applied to conventional reservoirs and the exploration and production of its shale plays.