四川盆地西北部陆相地层异常高压的形成与演化

FORMING AND EVOLUTION OF ABNORMAL HIGH PRESSURE IN TERRESTRIAL FORMATION IN NORTHWEST PART OF SICFIUAN BASIN

四川盆地西北部陆相地层广泛存在异常高压，纵向分布于上三叠统─上侏罗统，横向超压中心位于白龙场─丰谷镇一带。控制异常高压形成的因素主要有欠压实、蒙脱石脱水转化、生烃和构造等作用，但它们在地史中对异常高压形成的贡献及影响时间的长短各不相同。异常高压始于中侏罗世，止于第四纪早期．大规模增压发生在晚侏罗世。其演化模式是：起初由欠压实作用引起上三叠统三、五段产生异常高压，继而由生烃和蒙脱石脱水作用使异常高压增大，白垩纪─第三纪的生烃和构造作用使整个上三叠统─侏罗系出现异常高压。异常高压与油气藏的形成、分布有着密切关系，油气藏主要分布在裂缝发育的常压─超高压的过渡带。

The abnormal high pressure widely existing in the terrestrial formation in northwest part of sichuan Basin is distributed over Upper Triasic Series and Upper Jurassic Series in vertical direction and its centre in horizontal direction is located in the zone of Bailongchang-Fengguzhen, The main factors of controlling the abnormal high pressure forming are the actions of undercompaction, montmorillonite dehydration, hydrocarbon generating and structure.But the influences of the actions of undercompaction, montmorillonite dehydration, hydrocarbon generation and structure.pressure started from Middle Jurassic and ended at the early stage of Quaternary, Large-scale Pressure boost occurred in Late Jurassic. Its evolution pattern is that:at first, the abnormal high pressure of mimbers 3 and 5 of Upper Triassic Series was Caused by uneercompaction. Then the abnormal high pressure was enhanced by the actions of hydrocarbon generating and montmorillonite dehydration. Finally the actions of hydrocarbon generation and structure in Cretaceous Period and Tertiary Period made the abnormal high pressure formed. Abnormal high pressure is closely relative to the forming and destribution of oil-gas reservoirs. Oil-gas reservoirs are mainly destributed in the atmospheric-superhigh pressure transitim zone with growth fractures.