The Study On Dynamic Fracture Propagation Mechanism In Carbonate Reservoir

The reservoir properties of carbonate reservoirs are complex,and fracture is the main space and migration channel of carbonate reservoirs.Therefore,it is particularly important to study the dynamic expansion law of carbonate reservoirs during long-term displacement,which is of great significance for understanding the mechanism of fracture propagation and guiding field practice.Firstly,the quantitative relationship between fracture and permeability is studied theoretically and practically.A theoretical model is established to study the relative permeability under different fracture lengths,and an equivalent permeability chart reflecting the relationship between dimensionless fracture lengths and dimensionless permeability is established through experiments.Then,the core with incomplete fracture penetration is obtained by using the improved radial extrusion method,and the experimental study of fracture oil-driven propagation is carried out,focusing on the changes of inlet pressure,equivalent permeability and relative fracture length in the process of fracture propagation.Finally,uniaxial stress is applied to the relatively homogeneous and strongly heterogeneous carbonate core to make it break.The elastic wave in the process of fracture is monitored and recorded by acoustic emission sensor.The change of rock mechanics parameters in the process of fracture generation and propagation is analyzed by the results obtained by acoustic emission signal.Through this study,the relationship between fracture length and relative permeability is clarified,and the fracture length of half-fractured core can be calculated quantitatively by chart,which lays a foundation for quantitative characterization of fracture propagation process.Furthermore,the physical properties of rocks during oil flooding are studied by the experiment of fractured oil driving state expansion.Finally,from the aspect of rock mechanics,the variation law of stress and strain parameters and the fracture morphology in the process of crack propagation are studied.Therefore,it can lay a foundation for the theoretical study of fracture propagation law and the consideration of the changes of reservoir physical parameters caused by fracture propagation in the process of mining.