Hydraulic Fracturing Mechanism And Quantitative Evaluation Method Of Caprock And Fault

Hydraulic fracturing is a common phenomenon in nature,which has an important implication for deeper insight into fluid migration,hydrocarbon conservation and field safety exploitation.Therefore,on the basis of detailed study,this paper defines the general concept of hydraulic fracturing,which points out that hydraulic fracturing is a kind of rock brittle failure process that is caused by the increase of pore fluid pressure,including both extensional failure,extensional-shear failure and shear failure.This paper determines the criterion of hydraulic fracturing and points out that hydraulic fracturing is characterized by episodic and transient.This paper illustrates geological conditions and influential factors of hydraulic fracturing and determines the depth range of hydraulic fracturing.This paper studies various quantitative evaluation methods of hydraulic fracturing,points out the applicable conditions of various evaluation methods,and concludes that reactivation risk is expressed as the pore fluid pressure increase required to induce failure.Considering the applicable conditions of various evaluation methods,we use fault analysis seal technology to evaluate hydraulic fracture risk of caprock and fault in the Banzhongbei Gas Storage,determine the amount of pore fluid pressure increase required to induce failure for caprock is 8.9MPa,the position of the maximal risk for fault is higher part of Banqiao fault,the amount of pore fluid pressure increase required to induce failure for Banqiao fault is 3Mpa.So we determine that the gas injection pressure for Banzhongbei Gas Storage can increase 3MPa.We hope this deep work can offer a reference for the future study of hydrocarbon reservation and safety operation of gas storage.