CLASSIFICATION AND DISTRIBUTION OF THE COMBINED STRUCTURAL SANDBODY OIL AND GAS POOLS IN MESO-CENOZOIC CONTINENTAL BASINS OF CHINA

Based on the results of our recent investigation of the oil and gas pools in Meso-Cenozoic continental basins of China, a new classification of the oil and gas pools of various sedimentary facies developed in the basins has been proposed. The structural settings in which the oil and gas pools are formed include anticlinal traps, fault traps and anticlinal-fault traps, and in combination with sandbodies developed in various sedimentary facies, these traps, in turn, are assembled by 33 types of the oil and gas pools embodied into five categories, i. e. structural-alluvial fan, structural-channel sandbody, structural-deltaic, structural-beach/bar sandbody and structural-turbidite sandbody oil and gas pools.
The distibution of the combined structural-sandbody oil and gas pools in Meso-Cenozoic continental basins of China is controlled by the regional tectonic framework which resulted from collision and compression between the Indian plate, Pacific plate and Asiatic block, respectively. In the west of China, the depressed basins were forme on account of compresso-shear stress resulting in the formation of the combined structural-sandbody oil and gas pools on the steeper flanks of the piedmont depressed zone. It is expected that the structural-turbidite sandbody oil and gas pools will be recognized in the middle depressed zone, whereas the structural-deltaic (small scale) and/or structuralbeach/bar sandbody oil and gas pools in the slope zone or on the margins of the ancient rises. In the fault basins of eastern China originated dominantly from extensional faulting are the combined structural-sandbody oil and gas pools being characterized by zoning parallel to the long axis and by blocking parallel to the short axis of the basins (or depressions). The oil and gas pools here vary much in type and are aligned regularly. In the transitional basins of central China, the combined structural-sandbody oil and gas pools, the compound oil and gas pools being characterized by compressional structures, are believed to be related to the depressed zone.
The author suggests in this paper that the repeated occurrence of subsidence and return phases of various cycles in the Meso-Cenozoic continental basins of China is due to multicyclinal features of these basins in vertical orientation. Therefore, the more the assemblages of source, reservoir and caprock in the basins, the more abundant the oil and gas, and vice versa.
The formation of the combined structural-sandbody oil and gas pools reflects not only the structural settings during the formation of the pools, but also the sedimentary environments, facies and hydrodynamic regime for the formation of the reservoirs. It will be of great importance to the exploration and exploitation of the old oil and gas fields and prognostication of the new oil and gas pools.