Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

The Hailar basin in northeast China that extends to the petroliferous Mongolian Tamtsag basin is a cratonic rift basin that formed in the Late Jurassic to Early Cretaceous time contemporary with Songliao and Erlian basins. The basin is characterized by grabens and horsts that constitute structural elements of variable scale. The major sub-basins and uplifts include Jalai Nur sub-basin, Qagang uplift, Buir Nur sub-basin, Bayan Shan uplift and depressions, and Huhe Nur sub-basin from west to east. The stratigraphic sequences consist of syn-rift Xingganling and Jalai Nur Groups, and post-rift Buir Nur Group. The early rift phase is represented by volcanic and pyroclastic rocks with sedimentary interbeds of the Xingganling Group. The Jalai Nur Group of the main rift phase begins with alluvial fan and fan delta conglomerates of the Tongbomiao Formation. With intensified extension and subsidence, the deep lacustrine black shale and turbidites of the Nantun Formation was deposited. As the subsidence became stabilized and slowed, the deltaic system of the Damoguaihe Formation replaces the deep water facies. The rift phase closed with the deposition of the shallow lacustrine and fluvial coal bearing facies of the Yimin Formation. The regional unconformity separates the post-rift varicolored fluvial sequences of the Late Cretaceous to Cenozoic Qingyuangang Formation and Buir Nur Group. The source rocks of the basin are black shale and coal beds. Black shale occurs within Tongbomiao to Damoguaihe Formations, and organic matters are type II and III with abundance of average 2%. Coal beds occur in Yimin, upper Damoguaihe, and upper Nantun Formations, the vitrinite reflectances(Ro) of which are 0.38%~0.40%, 0.44%~0.57%, and 0.59%~1.01%, respectively. The oil generation for the Nantun Foramtion starts to operate in late Early Cretaceous at the time of deposition of the Yimin Formation. The main reservoirs are sandstone and sandy conglomerate beds in upper Damoguaihe and upper Nantun Formations, and some Yimin sandstones have good porosity as well. Seals are mudrocks of Damoguaihe and Yimin Formations, which make up 60~80% of the lithology. The petroleum system consists of Nantun(source and reservoir)- Damoguaihe(seal), Nantun and/or lower Damoguaihe(source)-upper Damoguaihe(reservoir)-Yimin(seal), and self- sourced and reservoired Nantun. Structures include fault-related anticlines, fault nose traps, and buried hills. The best hydrocarbon potentials are found in Wuerxun, Buir Nur and Hurun hu sags, the probable reserves of which are estimated to be 0.25, 0.22, and 0.44 billion tons, respectively.