Quantitative Evaluation Of Structural Compression And Pressurize Of Pore Fluid In Brittle And Brittle-plastic Rock And Its Significance Of Hydrocarbon Migration And Accumulation

Tectonic compression and pressurize is one of the important mechanisms for forming overpressure in sedimentary basins,and is the main driving force for hydrocarbon migration and accumulation and control the oil and gas accumulation in compressional basins.A lot of work has been done on the relationship between rock tectonic stress and abnormal pore fluid pressure,and a corresponding quantitative evaluation model for structural compression pressurization was proposed.However,these models have many parameters and are easily influenced by human factors,or they are not sufficiently considered in rock deformation process,deformation mechanism and pressure evolution,which limits the applicability and operability of the models to some extent.In view of the above problems,a new geomechanical model of structural compression pressurization(i.e.,stress-pressure coupling)is established based on rock mechanics and fluid mechanics.The new model divides the process of structural compression pressurization into three stages: volumetric pressurization,deformational pressurization and fracture decoupling.On the basis of the establishment of geomechanical model,a mathematical model for quantitative evaluation of structural compression pressurization is put forward.The new model takes into account the volume deformation and shape deformation of rock under the maximum,minimum horizontal and vertical stress states.it has high feasibility and practicability.Kuqa depression is an ideal area for the study of structural compression pressurization.Taking the bashijiqike formation of the lower cretaceous in kuche depression as an example,based on the empirical model of the compaction law of mudstone in the maximum burial stage,the fluid pressure before structural compression(the maximum burial stage)is obtained by using the balanced dept method.Then,with experimental data of acoustic emission from rock constraint,on the basis of geological model and boundary conditions,using ANSYS17.0 stress simulation software to reconstruct the horizontal maximum effective stress field and the horizontal minimum effective stress field in the kuqa depression during the maximum folding period,and Substituting into the new model of structural compression pressurization to obtain the fluid pressure after structural compression.After that,by comparing the fluid pressure before and after structural compression,the amount of structural compression pressurization was obtained.Finally,the use of stress and pressure under the coupling action of fluid potential and custom ? deformation degree coefficient,to evaluate the significance of hydrocarbon accumulation in structural compression pressurization.1.On the basis of fully considering the process of compression deformation,a new quantitative evaluation model for structure compression pressurization of brittle and brittleplastic rock with high practicability and feasibility is established.2.The incremental characteristics of tectonic compression in kuqa depression show that the pressure in the Dabei region is generally higher in the east and lower in the west,and the pressure range is 45-78 MPa.In the west and southeast of Keshen region,the pressurization is as high as 56-80 MPa,while in the northeast,its pressurization decreased to 30-56 MPa.3.Under the coupling of stress and pressure,the structural compression pressurization can increase the plane fluid potential gradient of bashijiqike formation of the lower cretaceous in kuqa depression by 1.1-2.8 times,which significantly improves the lateral migration dynamics of natural gas.4.Under the coupling of stress and pressure,tectonic compression pressurization can promote rock deformation,fracture activity and trap formation,which is a key factor in the accumulation of large gas fields in kuqa depression,such as kela 2,dabei and keshen.