Research and Application of Weighted Slickwater in Sand Fracturing of Deep Fractured Tight Sandstone Reservoir

Deep fractured tight sandstone reservoir is characterized by poor physical properties of matrix rocks, high temperature, high pressure and high stress. Fractures are the main spaces and channels for the petroleum to stay and flow through, so low viscosity fluid is needed to improve the activation of natural fractures. But the deep reservoir has high breakdown pressure, low success ratio of breakdown and great difficulty in fracturing, so the stimulation technology is facing great challenges. Through laboratory experiments, high-efficiency weighting agent and cleanup additive were optimized, high salt resistance friction reducer was developed, and a new type of industrial calcium chloride weighted slick water system was formed. Laboratory study and numerical simulation were combined to ascertain the working mechanisms of slick water in volume fracturing. According to the characteristics of reservoir, the fracturing technology of combination of slick water, acid and gel is proposed. The results show that the calcium chloride weighted slick water system has excellent friction reduction performance, the friction reduction rate is 53–62%, and the density is 1.35 g/cm3, which can effectively reduce the wellhead pressure, enhance the pumping rate, and improve the success ratio of breakdown. The complex fractures are generated by weighted slick water injection with high pumping rate, low viscosity acid injection dissolves the filling natural fractures, weighted slick water and low viscosity acid injection alternately, activates the natural fractures, supports the main fracture with sand carrying gel, expands the fracturing volume, and forms the complex fracture network. The above research results achieved good results in the field test, which has important reference significance for exploring the stimulation technology of deep fractured tight sandstone reservoir.