The Reason Of Reservoir Overpressure In South Of Long Hu Pao Oil Field

The drilling data indicates that the Putaohua reservoir and the following reservoir exist overpressure in south of Long Hupao oil field, and mainly development in the Putaohua reservoir, Hei Dimiao reservoir doesn't exist overpressure, which is above the Putaohua reservoir; According to the formation test data, the formation research area have two pressure systems, the lower overpressure system (pressure coefficient 1.2~1.4) contains n2-qn1 section, which mainly distributes in Puxi and Xinzhao oil field with relative clear boundary in the center of Gulong depression, but the lateral boundary is fuzzy; The upside pressure system is an normal pressure system contains the n3 section to surface. With thorough research and exploration development in this area, we discovered that the overpressure, oil-gas generation, migration and accumulation have close relation, and we need thorough research on the overpressure and its development mechanism.According to the heat flow analysis and the nowadays tectonic stress field analysis, the reservoir overpressure is not caused by hydrothermal pressurizatio and tectonic stress. through the calculation of hydrocarbon generation intensity in the Source rock, the mud overpressure and the oil cracking, combining the quantitative analysis of the reservoir overpressure, we thought that the reservoir overpressure mainly compose the overpressure which derives from the transmission from mud layer hydrocarbon generation of overpressure system to the reservoir pressure, secondly is the crude oil cracking. The preservation of reservoir overpressure benefits from the pressure compartment in this area, the mud undercompaction of n1-2 and qn1 sections are the top-bottom partition board of Over-pressured Fluid Compartment, the diagenesis formed the lateral separate, the fault also play the certain seal role. The analysis of overpressure evolution history indicates that the reason of overpressure formation is different in various geological periods, qn1 section: the undercompaction and the tectonic compression are the main reasons for the overpressure development during 100~73 Ma , during the 67.7 Ma and 0 Ma hydrocarbon generation function is the main reason for overpressure development; Putaohua reservoir: the pressure transmission are the main reasons for the overpressure development during 76.8~65 Ma, in the 65~0Ma pressure transmission and the oil cracking are the overpressure mechanism.