Study on genetic mechanism of overpressure system in middle-deep layers in western sag of Liaohe Basin
The western sag develops obvious overpressure in the middle-deep layers.To identify the distribution and formation mecha-nism of overpressure is of great significance for oil and gas exploration in this area.The development characteristics,genetic mechanism and control effect of overpressure on reservoir formation in the middle-deep layers of the western sag were studied based on the measured formation pressure,logging curve combination,overpressure identification chart and basin simulation in this study.The results indicate that the western sag as a whole develops three types of thermal compression systems:overpressure type,normal pressure type,and low pressure type.Overpressure mainly develops in the middle-deep layers between 2 500 m and 4 000 m,and the overpressure is mainly caused by undercompaction.In the middle section of the Lengjia and Leijia area,in addition to the contribution of undercompaction,the overpressure of the Es3 Formation is locally accompanied by a mixture of hydrocarbon generation,diagenesis,and tectonic compression.Due to the strong uplift and denudation in the north area,the Es3 Formation is mainly characterized by abnormal low pressure.Basin simulation method is used to evaluate the genetic contribution of overpressure.There are three stages of pressure evolution,the first stage is dominated by undercompaction caused by tectonic subsidence.In the second stage,due to the formation uplift and pressure relief,un-dercompaction and fluid expansion stopped briefly.In the third stage,the source rock reached the peak of hydrocarbon generation,and the hydrocarbon generation pressurization gradually increased and the fluid expansion pressurization reached 5 MPa.
overpressure distributiongenetic mechanismamount of contributionmiddle-deep layerswestern sag
万方数据
维普
