NUMERICAL SIMULATION OL LRACTURE STRENGTH FOR GLUTENITE BASED ON RFPA METHOD USING IN HYDRAULIC FRACTURING TECHNOLOGY

摘要

Glutenite reservoirs have huge development potential,but these reservoirs are characterized by tight oil with poor physical properties.These reservoirs need to undergo fracturing transformation to form industrial capacity requirements.Reservoir rock fracture toughness is the main influencing factor of hydraulic fracturing.Based on the rock fracture process simulation system RFPA,the influencing factors of sandstone glutenite core fracture toughness are studied.Based on RFPA,a central straight crack disc model was established to change the directional arrangement of crack dip angle,density and cement strength,and analyze their influence on the crack propagation morphology and fracture strength of sandstone.The results found that as the crack density increases,the occurrence of bifurcations or crack deflection increases during the crack extension process.As the angle between the prefabricated crack and the crack increases,the crack extension direction gradually deviates from the aligned cracks.Fracture toughness decreases as the crack surface mechanical properties decrease and the effect of crack inclination angle on fracture toughness increases.With the increase of crack density,the fracture toughness of the numerical simulation samples shows an overall decreasing trend,and the development of microcracks will lead to the reduction of the fracture toughness.This study can provide theoretical support for improving the hydraulic fracturing efficiency of glutenite reservoirs,and can effectively improve the safety risk and environmental protection performance of the fracturing process.