Abstract:
In recent years, quite a few wells in the Eastern Uplift of Liaohe Depression have drilled significant hydrocarbon shows in the Paleozoic strata, revealing promising exploration potential. However, the main controlling factors and accumulation model for these hydrocarbons remain unclear, severely hindering further exploration. To better evaluate the exploration potential of the Paleozoic hydrocarbon in the Eastern Uplift, this study integrates data from outcrops, seismic surveys, exploration wells, and chemical experiments to analyze key conditions for hydrocarbon accumulation such as source rocks and reservoirs, and to identify the primary controlling factors and corresponding accumulation models. The results indicate that the Eastern Uplift develops three potential sets of source rocks, i.e. Carboniferous-Permian Benxi, Taiyuan, and Shanxi formations, in which dark mudstones and coal seams exhibit high organic matter content. Two main reservoir types, namely the Upper Paleozoic tight sandstone and the Lower Paleozoic weathered carbonate rock crusts, are identified. The accumulation of Upper Paleozoic lithologic gas reservoirs is primarily controlled by reservoir quality, whereas the formation of Lower Paleozoic weathered crust gas reservoirs is mainly governed by the distribution of overlying source rocks and karst reservoirs. Four hydrocarbon accumulation models are established: Upper Paleozoic self-sourced lithologic gas reservoirs; Lower Paleozoic weathered crust gas reservoirs with upper-source and lower-reservoir configuration; Upper Paleozoic and Mesozoic secondary gas reservoirs; and young-source-old-reservoir oil accumulations.