Technology of production enhancement by fracturing of multiple branch fracture in vertical well in low permeability oilfields in the periphery of Daqing

Conventional fracturing in low-permeability oilfields in the periphery of Daqing creates the small scale double-wing fracture, and the small fracture controlled volume and the poor stimulation effect were obtained. Increasing the fracture length promotes communication with offset wells and fails in improving the controlling degree of sand body between well arrays, and the development cost increases. The fracturing technology of multiple branch fractures in the vertical well creates multiple branch fractures on both sides of the major fracture under the condition of well pattern, increases the fracture controlled volume, improves the controlling degree of sand body between well arrays, and enhances the stimulation effect. Through physical and numerical simulation, the formation mechanism of branch fractures was obtained. Based on variation of rock mechanical parameters and the characteristics of branch fracture initiation, an optimization design method integrating computation of in-situ stress evolution and optimization of fracture parameters was formed. The fiber temporary plugging agent inside the fracture was optimized, the temporary plugging process of fiber + proppant in the fracture was formed, and the field diagnosis and control method was developed. The technology has been applied in 310 wells. The increase in daily oil production per well at the initial stage is 1.9-4.8 t, which is 2.1-4.0 times that of conventional fracturing, and the return on investment is 1:2.5, providing technical support for efficient development of low-permeability reservoirs in Daqing Oilfield.