Distribution Characteristics And Identification Of Pressure Compartments In Eastern Kuqa Depression

The theory of pressure compartment is an important method to study hydrocarbon accumulation.However,so many years have passed,the research on pressure compartment mostly stays in the macroscopic and large-scale direction,at the same time,some experts and scholars regard the material composition in the sedimentary basin as homogeneity when studying the pressure compartment.Obviously,the understanding is not appropriate.It is difficult to study the heterogeneity of sedimentary and diagenesis,especially for the study of small-scale heterogeneous pressure compartment.Overpressure is widely developed in Kuqa depression.It is not only closely related to hydrocarbon accumulation,but also plays an indispensable role in the tectonic deformation stage.Therefore,the study of overpressure in Kuqa depression is important and meaningful.The theory of pressure compartment can be said to be an extremely effective means of studying overpressure.In the research,based on the comprehensive analysis of the compaction curves,the seals of pressure were identified on the macroscopic level,and the influence of the pressure compartment on the pressure was analyzed according to the pressure calculated by the equivalent depth method and the measured pressure distribution characteristics.And then,according to the results of X ray diffraction and scanning electron microscopy,the microscopic features of the pressure seals and non-pressure seals were analyzed.The geological model was established by Software-S and the data body of impedance was obtained based on the model inversion.Furthermore,the seismic multi-attribute inversion method was used to predict the corresponding pressure of the whole study area by combining single well fluid pressure and residual pressure on Software-E.By comparing the logging response of acoustic time difference,natural gamma and density in a single well through the seismic profile,the pressure compartments were identified.Finally,probabilistic neural network inversion was used to predict the gas saturation of the study area,and the relationship between gas saturation and pressure compartment was analyzed.The following points are recognized:(1)There are three sets of regional pressure seals in eastern Kuqa depression.According to the lithological distribution characteristics and location of the pressure seals,it is determined that there are three pressure compartments in the area,named the top gypsum pressure compartment,the middle mudstone pressure compartment and the bottom mudstone pressure compartment.(2)The pressure seals and the non-pressure seals have significant differences in mineral composition and microscopic pores.The pressure seals have high clay mineral content,over seventy percent,micropores,organic pores and micro cracks are seen frequently;the non-pressure seals have low clay mineral content,and the perforation micro crack is seen regularly.(3)The seals of partial pressure compartment have two genetic mechanisms,which are capillary seal and overpressure seal.