The first successful case for exploration oil in New China was the discovery of the Daqing oil field in 1958. The discovery of the Daqing oil field subverted the concept that oil can only be formed in marine strata, and proved that oil field could also be formed in continental strata. Besides, in the exploration of Daqing oil field advanced geophysical methods were adopted to carry out strategic regional investigation, and the geophysical work was no longer confined to front basins with oil seepage.
In the upcoming oil exploration, we should create a common perspective that oil is generated in the mantle, and hence the work should expand to the whole lithosphere.
According to thermodynamics, methane is the sole hydrocarbon which can be stably living under the standard temperature and pressure condition; straight-chain alkanes hydrocarbons can be formed only under the condition pressure > 30 kbar and temperature > 700℃ (corresponding to a depth about 100 km). Therefore, both marine oil generation theory or terrestrial oil generation theory cannot hold the water. In fact, oil is generated in the mantle, and then migrate to marine basins or terrestrial basins for accumulation of petroleum.
Geophysical methods play an important role in prospecting for deep oil reservoir. Many petroleum geologists have considered that the low velocity-low resistivity layer is closely related to oil reservoir. Besiders, researchers have found that, under the known oil fields, there frequently exists asthenospheric matter. Asthanosphric matter is active and can penetrate mantle matter to form a mushroom cloud in the mantle.
Based on seismic tomography and regional geological environtal condition, the authors put forward three perspective regions for oil exploration:
(1) The East Asia-West Pacific Oceanic low-velocity region. There are three zones which were formed in MesozoicCenozoic period and are different in depth, extent and shape. From west to east, they are Songliao-North China -SE China coastal continental rift zone; Japan Sea-Yellow Sea-East Sea-South China Sea marginal sea rift zone, and Shikoku Sea basin-Parece Vela Sea basin -Papua New Guinea marine rift zone
(2) East Tetisi mantle uprifting region:The East Tetisi mantle uprifting region consists of Lanping basin, Simao basin and Chuqiong basin in Southwest China. This region originally had the richest oil and gas reservoirs in the world, but its structures were severely destroyed under the extrusion of the Indian block
(3) The deep faults in Xinjiang region:The Xinjiang region formed a series of synformal and antiformal structures under the extrusion of the Indian block, and hence deep oil may migrate upward to the surface through deep faults. According to satellite gravity, the authors hold that Bayan-Ovoo-Xining discontinuous zone, Naomaohu-Mangnai discontinuous zone, Yutian-Keriya Hu discontinuous zone, and Alma-Ata-Taxkorgan discontinuous zone are favorable areas for oil exploration.