Formation conditions of deep hydrocarbon in Junggar Basin, NW China

With the increasing degree of identified shallow hydrocarbon resources, the possibility of making a breakthrough in shallow strata is decreasing and the direction of oil and gas exploration is turning to deep strata. All around the world, over one thousand hydrocarbon reservoirs have been discovered and developed in deep strata with buried depth greater than 4 500 m. At present, the depth of all the discovered and developed hydrocarbon reservoirs is less than 4 500 m in the Junggar Basin. Considering that a breakthrough has not yet been made in deep strata, a discussion of deep hydrocarbon accumulation conditions has important practical significance in the Junggar Basin. Based on previous studies, source rocks, reservoirs, cap rocks and preservation conditions are taken as research subjects and the accumulation conditions of deep hydrocarbon are analyzed. The southern margin and central depression of the basin developed many sets of argillaceous source rocks in the deep zone and have entered into the mature to high-maturity stage. Due to the geological processes of over-pressure and erosion, etc., relatively high-quality reservoir intervals are widely developed in deep strata. Many regional cap rocks can be effective seals, beneficial to deep oil and gas accumulation and preservation. Timing and spatial relationships among source rocks, reservoirs, cap rocks, and the hydrocarbon shows in deep strata of exploration wells suggest that the central depression and southern margin are favorable zones for deep oil and gas exploration.