The timing of gas pooling in the Upper Paleozoic in the northern Ordos Basin:A case study of the Hangjinqi Block

The Hangjinqi Block,one of Sinopec's major exploratory blocks in the northern Ordos Basin,is favorable for its source rocks,reservoirs and sealing conditions.At present,there is still much controversy over the timing of hydrocarbon pooling in the Upper Paleozoic in the study area.So various methods,such as hydrocarbon generation time,trap forming stage,fluid inclusions,reservoir tightening time and coal pyrolysis simulation,are used to study the timing of hydrocarbon pooling.The study shows that there are two periods of large-scale hydrocarbon migration and accumulation in the Upper Paleozoic in the Hangjinqi Block.And the analysis of peak hydrocarbon generation and homogeneous temperatures of fluid inclusions reveals that these two periods correspond to a stage of co-generation of oil and gas from Middle to Late Jurassic and a stage of large-scale gas generation from late of the Early Cretaceous till present respectively.The application of multiple methods overcomes the limits and shortcomings of a single one,thus improving the reliability of the conclusions.