Differential Evolutions of Hydrocarbon Generation and Expulsion History of Lower Cambrian Source Rocks in Tahe Oilfield and Accumulation Effects
In response to the unclear understanding of the main controlling factors for multiphase oil and gas enrich-ment of the Ordovician oil reservoirs in Tahe Oilfield,the basin simulation technology was used to reconstruct the thermal evolution history and hydrocarbon generation history of the Lower Cambrian source rocks,and oil and gas migration and accumulation processes of typical profiles.The research shows that the Lower Cambrian source rocks in Tahe Area have entered a mature stage from the early Caledonian period and are currently in a high maturity-wet gas stage.They have developed three thermal evolution models of intermittent burial,continuous burial,and long-term shallow burial,corresponding to three hydrocarbon generation models of dual peak,strong oil and weak gas,and single peak.The differential thermal evolutions of source rocks lead to the history of oil and gas evolution with multiple stages of filling,vertical migration,and lateral adjustment and transformation in the Ordovician.The oil and gas phases present an orderly distribution pattern of light-medium-heavy oil reservoirs.The thermal evolutions of the Lower Cambrian source rocks in different structural belts in Tahe Area show a trend of increasing from north-west to southeast,showing a clear positive correlation with the differences in oil and gas phases,reflecting the char-acteristics of"source control".The thermal evolution characteristics controlled the distribution of current oil and gas reservoirs in the Himalayan period.Research indicates that the hydrocarbon generation intensities in the salt zone and Tuofutai of Tahe Oilfield are high,and the total amount of hydrocarbon generation during the Himalayan period is relatively large,making it a favorable area for further exploration and development.The research results have certain guiding significance for the evaluation of deep oil and gas resources and targets in Tahe Oilfield.
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