渤南洼陷古近系深层异常压力特征及成因

Characteristic and origin of the abnormal pressure in the deep Paleogene formation in Bonan Sub-sag

以声波时差资料为基础,结合测井、地质、钻井及试油试采资料,利用等效深度法计算渤南洼陷古近系的地层压力,并综合分析地层压力的分布特征.探讨了异常高压的成因机制,确定形成异常高压的主要原因为不均衡压实作用,烃源岩在埋藏过程中大量生烃进一步促进了异常高压的发育,另外,致密的盐膏层可有效保护异常高压.在此基础上,总结出渤南洼陷异常压力的2种结构模式.

By combining acoustic time data with a lot of logging data,geologic data,drilling data,oil testing and oil recovery data,the formation pressure in the deep Paleogene formation in Bonan Sub-sag is calculated using the contour depth method.The distribution characteristic of the formation pressure is analyzed.It is shown that there is widely abnormal pressure in the Paleogene formation pressure in Bonan Sub-sag,but the pressure coefficient is generally less than 1.6.Bonan Subsag can be divided vertically into two independent pressure systems,the shallower one is normal pressure systerm and the deeper one is abnormal pressure system.The plane distribution of the abnormal pressure is controlled by sedimentary facies zones and faults,its distribution presents cyclic zonal pattern around pressure center.It is held that disequilibrium compaction is the main cause leading to the abnormal pressure,the hydrocarbon generation of source rocks promotes the formation of the abnormal pressure,and the dense gypsum rock effectively protect the abnormal pressure.