Abstract:

The multilayer source rocks in southern Junggar depression are characterized by their extremely high abundance of hydrocarbon generation.The Permian and Trassic have been buried very deeply in the depression,so they would not have any exploration significance anymore except transporting hydrocarbons upward along faults to shallow reservoirs.Although the Jurassic is a good source of hydrocarbons,conventional accumulations would not be formed in later stage,because it has been deeply buried,as deep as 10000m in the center of the depression,and has become tight and ultra-tight strata.The Jurassic had experienced early formation of deep basin gas and later destruction,modification and adjustment of deep basin gas.Gas accumulations may exist in the following areas. (1) Some deep basin gas reservoirs might have been preserved in Beidapo (Northern Big Slope) area; (2) The 3 rows of structures formed in foothill belt by compressive and shear tectonic movement.Hydrocarbons might have migrated along faults to the shallow structures,resulting in formation of secondary gas reservoirs; (3) Although the Jurassic has very large burial depth,it might become prolific gas reservoir with large reserves again,as a result of the fractures formed in Later stage,thus it would still have large exploration potential; (4) In the deep basin gas area,large attention should be paid to the gas potential in the "sweet points",such as thick and large sandbodies and ancient traps in the favorable facies zone.

Key words: high abundance of gas generation, early reservoiring, deep basin gas, modification during Himalaya movement, ultra-tightening, very deeply buried, southern Junggar depression