Key technologies of multi-stage fracturing string in Sichuan-Chongqing high-pressure tight gas reservoirs

The potential of the old wells in the tight gas reservoirs in Sichuan-Chongqing area needs to be further tapped by multi-stage fracturing process, however, the existing process string cannot meet the complex requirements of high pressure, large-sand-volume erosion, setting under slurry conditions, and removable after fracturing, therefore, researches on multi-stage fracturing technology in high-pressure tight gas reservoirs were carried out. Y344 pressure-steering sand blasting packer was developed independently. This packer integrates blasting and packing functions, reducing tool size, and improving the passability of multi-layer fracturing strings. The structure of the sandblasting body and rubber cylinder of the packer was optimized by finite element analysis software, and 42CrMo high-strength material was selected to improve the pressure bearing performance. Researches on erosion and abrasion resistance of materials were carried out, the flow state was analyzed by using numerical simulation method, the layout of cemented carbide parts was optimized, and the problem of large wear in areas such as sandblasting ports was solved. Hydraulic anchors and other tools were designed with liquid inlet sand control structure to meet the requirements under slurry environments. Laboratory experiments show that the technical string meets the high-pressure requirement of 90 MPa, and the sand volume added into a single layer on site reaches 160 m³, which provides an effective technical means for solving the problem of high-pressure multi-stage tubing fracturing in similar reservoirs.