Origin of High Oil and Gas Saturation in Deep and Ultra-Deep Tight Clastic Rocks
The deep and ultra-deep tight clastic oil and gas reservoirs in the southern margin of Junggar basin have high productivity and long stable production time,which are closely related to the high oil and gas saturation of the oil and gas reservoirs,and their genetic mechanism is unclear,which brings confusion to the understanding and evaluation of such oil and gas reservoirs.Based on the data of well logging,geology,oil testing,rock physics experiment and previous research results,the petrophysical experiments of rock thin sections,reservoir physical properties and rock electrical parameters under simulated dynamic formation pore pressure are carried out.The research results show that the ultra-high pressure and high temperature strata are widely developed in deep and ultra-deep layers,and the overpressure strength of the formation controls the development degree of fine fractures in the oil and gas layers and improves the pore structure of the reservoir.The double pore structure of the oil and gas layer is the main cause of the high yield of the ultra-deep tight clastic rock.At the same time,formation overpressure makes the lithologic cementation index of Archie formula decrease with the increase of pore pressure.The saturation index decreases with the increase of pore pressure,decreases with the increase of formation temperature.Therefore,the formation with extremely high overpressure and high temperature is conducive to the formation of high oil and gas saturation.The research results reveal the changes of pore structure and oil saturation in deep and ultra-deep strata under extreme overpressure and high temperature,which provide reference for the understanding of high oil and gas saturation in deep and ultra-deep tight clastic strata.
log evaluationdeep and ultra-deep strataformation overpressureoil-gas saturationrock physics experimentsouthern margin of Junggar basin
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