Research On Hydraulic Impact Fracturing Technology For Oil And Water Wells In Deep-sea Low-permeability Reservoirs

China not only has vast onshore oilfields,but also is rich in offshore petroleum resources.Increasing the production of oil and water wells in deep-sea low-permeability reservoirs has gradually become a major problem in production.Hydraulic impact fracturing technology is a new technology that uses hydraulic impact fracturing to generate multiple fractures in the reservoir and extend the fracture to the deep to enhance reservoir permeability,thereby increasing oil production.The technology is simple in construction,reliable in technology,low in cost and high in safety.It uses hydraulic impact fracturing technology to transform the near-wellbore zone of oil and water wells to improve the injection and production capacity of oil and water wells.This technology has achieved satisfactory application effect in onshore oilfields at home and abroad.Although this technology has achieved good results in onshore oilfields,it has not been used in offshore oil and water wells.Compared with land,offshore oil and water wells are mostly large-sized casing completions,if applied in offshore platforms,further tests and researches are needed.Firstly,by analyzing the components of the hydraulic impact generator,this thesis studies its working principle and explores the fracturing principle and fracture mechanism of the technology.Subsequently,the blank control test of hydraulic impact fracturing and the ground target test are carried out to measure the pressure change curve and observe the crack shape of cement target and the damage degree of sieve tube;then through calculation,the influencing factors and variation rules of the instantaneous pressure above the plunger are found.Finally,the optimum hydraulic impact fracturing tool size is obtained by optimizing the size parameters of the supporting impact chamber for 9-5/8" casing and 7"casing with 4000 m vertical depth and 4-1/2" sieve tube with 2000 m vertical depth in offshore oilfields respectively,which provides a new technology and method for offshore oil exploitation and oil recovery enhancement.