Study On Influence Of The Stress Sensitivity On Pore Structure And Fluid Flow In Porous Media

At present,large quantities of experiments related to stress sensitivities on macro scale have been studied.Pore structure is complicated,especially the unconventional reservoirs like tight sandstone,so stress sensitivity would have a great influence on changing the pore space.It is of great significance for development and enhancing the EOR to study the stress sensitivity systematically on pore scale.In this paper,based on CT scanning technology which could capture the pore space characters of the real core,combing the technology of digital core and pore network model,the relationship between the effective stress change and the pore structure is obtained.In the meantime,fluid structure interaction model coupling the fluid flow and deformation on pore scale is established,and simulation is done on images.In the aspect of experiments,firstly,the theory and method of constructing the digital core and extracting the pore network model according to CT scanning is introduced.3D core image could be got after CT scanning,and digital core is established after filtering and segmentation.The rock structure characters could be got when analyzing the geometry-topology structure of the pore network model extracted,and the fluid flow analysis could be got after flow numerical simulation.Then,the method of stress sensitivity experiment and analysis is built on the basis of manmade sandstone.According to the industrial standard,stress sensitivity experiments are done in the carbon fiber core holder,and the core is scanned under a series of pressures.As well as this,digital cores and pore network models under a series of pressures could be obtained,and the corresponding pore structure characters and fluid flow laws could be analyzed.Finally,this method could be used in the meso-high permeability sandstone and tight sandstone.The stress sensitivities of these sandstones are achieved and compared.In the aspect of simulation,the fluid structure interaction model could be established based on the uncompressible NS equation and Biot stress-strain equation.The physical models include 2D equal circle model,2D unequal circle model and real SEM image model,and the relationship between porosity-permeability and confining pressure as well as fluid pressure difference could be got when simulating based on finite element method.In this dissertation,one comparative integral stress sensitivity evaluation method is formed,which would have the value of practical application on enhancing the oil recovery.