Research and Application of Dual-Packer Single-Layer Volume Fracturing String with Pressure Drag

At present, the dual-packer single-layer volume fracturing process is one of the main ways of re-fracturing old horizontal Wells in Changqing oilfield. However, there are still some problems, such as tubing erosion within the stuck distance, tool erosion damage, insufficient packer durability, long blowout time and low construction efficiency, which seriously restrict the scale promotion of old Wells. Therefore, the research on dual-packer single-layer pressure drag volume fracturing string was carried out. The transition between fracturing and plugging was carried out by using the controllable check valve switched by a ball, and the oil pipe dynamic sealing outside the oil pipe under the condition of annular pressure was realized by supporting the micro-collar oil pipe wellhead dynamic sealing device, finally achieving the purpose of dual-packer single-layer volume fracturing and continuous construction with pressure drag.The field application results show that the string can satisfy the pressure drag fracturing construction with dual-packer single-layer at the displacement rate of 8m3/min, effectively improve the overall construction efficiency, reduce the equipment occupancy rate, and solve the overflow problem during tripping, reduce well control risk and environmental protection pressure. It has a certain promotion and application prospect in the reconstruction of old Wells and the fracturing construction of casing damaged Wells.