SOURCE ROCK CHARACTERISTICS AND OIL/GAS SOURCES OF THE BACHU UPLIFT IN THE TARIM BASIN

On basis of studies of reservoir bitumen, liquid inclusion, saturation pressure/bubble point pressure of hydrocarbon pools, there are 4 stages of formation of hydrocarbon pools in Tahe Oilfield and its adjacent: (1) the destruction of pools was occurred in the Early Hercynian, pool-forming and modification in the Late Hercynian, formation of oil pools in the Yanshanian-Early Himalayan, and formation of light oil and gas pools in the Late Himalayan. The forming mechanism of hydrocarbon pools of the Tahe Oilfield can be superimposition, combination and modification of pools in the Tahe Oilfield were supported by the continuous supply of oil and gas from the Lower Paleozoic source rocks since the Hercynian; (2) the Tahe area was long located in a slope, where was the only way of hydrocarbon migration and provided basic condition for large scale of accumulation and multiple pool-forming; (3) efficient combination of reservoirs and seals in various level and the difference of hydrocarbon distribution in time and space resulted in multiple pool-forming and changes of oil and gas properties after pools were formed; (4) evolution of sealing system of pools played very important role in hydrocarbon preservation, destruction and modification. The formation and destruction of early sealing system provided clues for discovery of marine heavy primary oil reservoirs; and reconstruction of late sealing system was important factors for preservation of secondary and primary light oil reservoirs and especially gas reservoirs.