Genetic mechanism and exploration significance of overpressure and low-saturation oil and gas in the hinterland of Junggar Basin
Overpressure and low-saturation are typical characteristics of reservoirs in the hinterland of Junggar Basin.Based on analyt-ical testing,drilling/logging,production test data,basin simulation results,as well as comprehensive geological analysis,this study clarifies the coupling relationship among reservoir diagenesis,hydrocarbon charging,and overpressure development,explores the pressure-stress coupling effect and its role in hydrocarbon accumulation,and reveals the genesis of overpressure and low-saturation oil and gas reservoirs and their main controlling factors.The results indicate that hydrocarbon charging stage lags behind the forma-tion of overpressure caused by chemical compaction and reservoir densification.The formation of overpressure and low-saturation reservoirs is controlled by the coupling of four key factors.Specifically,overpressure caused by chemical compaction reduces the ef-fective pore space in the reservoir available for hydrocarbon charging and decreases the height of hydrocarbon column.Then the over-pressure,coupled with tight reservoir,increases the threshold pressure required for hydrocarbon migration and charging.The cou-pling effect of overpressure and stress leads to the failure of fault-related traps,while late-stage tilting and uplifting movements result in hydrocarbon loss.The hydrocarbon exploration in deep overpressure reservoirs in the hinterland of Junggar Basin should avoid the areas with intense chemical compaction-induced overpressure.The study primarily targets at lithological traps,anticlinal traps,and lithological-tectonic traps,followed by fault-related traps.For the same type of traps and exploration targets,those with relatively greater depth should be prioritized for drilling.This understanding has been confirmed in recent oil and gas exploration in the hinter-land of Junggar Basin and provides significant guidance for the exploration of overpressure and low-saturation oil and gas in this area and regions with similar geological conditions.
overpressurelow-saturationdiagenesis-pressure-accumulation couplingpressure-stress coupling effecthinterland of Junggar Basin
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