四川盆地元坝—通南巴地区须家河组致密砂岩封隔型超压系统压力结构特征

致密砂岩气层系通常发育封隔型超压系统，但是封隔型超压系统压力结构的实例研究少见报道。四川盆地北部元坝—通南巴地区须家河组致密砂岩层系发育典型的封隔型超压系统。基于丰富的实测压力数据，勾画了致密砂岩封隔型超压系统的压力结构轮廓；应用烃源岩与致密砂岩地质、地球化学以及构造演化分析资料，阐述了封隔型超压系统压力结构的影响因素。研究结果表明，须家河组致密砂岩封隔型超压系统的压力结构表现为各砂岩层段以及同一砂岩层段纵横向上压力系统彼此封隔不连通；呈现了多尺度、多层次的封隔型超压系统的特征。烃源岩生烃强度与超压发育幅度成正比，天然气充注是超压发育的主要动力机制；砂岩整体致密化形成了超压系统的背景，区域性泥岩和泥岩间层以及致密砂岩层系内部超致密砂岩层段的发育分布，构成了多尺度、多层次封隔型超压系统的总体格架。

Characteristics of overpressure regime in compartmentalized overpressured system within tight sandstones,Xujiahe Formation,Yuanba-Tongnanba areas,Sichuan Basin

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 the literature. The Upper Triassic Xujiahe tight sandstone formation in the Yuanba-Tongnanba area, northeastern Sichuan Basin, is a typical compartmentalized overpressured system. In this study, an overpressure regime in a compartmentalized overpressured system was delineated based on abundant measured pressure data, and the factors controlling overpressure regime in the compartmentalized overpressured system were clarified by comprehensively analyzing the geologic and geochemical data and the structural evolution of source rocks and tight sandstones. Results show that the overpressure regime in the compartmentalized overpressured system within tight sandstones of the Xujiahe Formation were separated from each other in both vertical and horizontal distribution of sandstone intervals, or even in the same intervals, exhibiting multi-scale and multi-level features for the compartmentalized overpressured system. Natural gas filling is a primary dynamic cause for overpressure generation, and its magnitude is directly related to gas generation intensity. The generally densified sandstones formed the background of overpressure system. Locally distributed mudstones and mudstone interbeds, and highly densified sandstone interbeds formed a multi-scale and multi-level framework of the overpressure system.