Basic research progress and development suggestions on hydraulic fracturing

There are abundant oil and gas resources of high recovery difficulty in China, e.g. low-permeability, shale and tight oil and gas, and the efficient development of this type of oil and gas resources is now one of the important measures to guarantee domestic oil and gas supply. Hydraulic fracturing is widely applied to the reservoir stimulation of oil and gas resources of high recovery difficulty and presents remarkable effect of reserve increase and production improvement. In order to research and develop hydraulic fracturing technology better, domestic and foreign new hydraulic fracturing technologies and basic research results (e.g. theoretical study, numerical simulation and physical simulation of hydraulic fracture initiation and propagation) in recent years were reviewed, and the shortages of the current researches were pointed out. It is indicated that the match between engineering and geology, the selection of steady and non-steady injection modes, and the similarity between the physical simulation of hydraulic fracturing and its field prototype are the key factors controlling the effectiveness of new hydraulic fracturing technology. Then, the key research contents on hydraulic fracturing of cyclic water injection and fluctuating water injection were proposed, including the formation mechanism of non-steady fluid injection, wellbore pressure fluctuation behavior, fracture initiation and propagation mechanism of reservoir rock, physical simulation experiment and pilot test of fracturing, and downhole string mechanics and control technology, so as to develop the basic theories and supporting technologies of non-steady hydraulic fracturing technologies suitable for low-permeability, shale and tight reservoirs in China as soon as possible and prepare the design criterion and construction norm of non-steady hydraulic fracturing.