Characteristics Of Overpressure-regime And Contributing Factors In Compartmentalized Overpressured System, Xujiahe Formation, Yuanba-Tongnanba Area

Compartmentalized overpressured systems are commonly developed in tight gas sandstones.However,studies about the characteristics of overpressure-regime in compartmentalized overpressured system are rarely reported in literatures.The Upper Triassic Xujiahe tight sandstone in the Yuanba-Tongnanba Area,northeastern Sichuan Basin,is a typical compartmentalized overpressured system.In this study,an overpressure-regime in compartmentalized overpressured system was delineated based on abundant measured pressure data,and factors controlling overpressure-regime in compartmentalized overpressured system were clarified by comprehensively analyzing geology and geochemistry data of source rock and tight sandstone,and structural evolution.Results show that the characteristics of overpressure-regime in compartmentalized overpressured system within tight sandstone of Xujiahe Formation are separated from each other in both vertical and horizontal distribution of sandstone intervals,or even in the same intervals,exhibiting multiscale and multilevel features for this compartmentalized overpressured system.Natural gas filling is the primary dynamic cause of overpressure generation,and its magnitude is directly related to the gas generation intensity.The generally densificated sandstones forms the background of overpressure system,locally distributed mudstone,mudstone interbed and the highly densificated sandstone interbed are collectively form a multicale and multilevel framework of the overpressure system.