Multi-packer separate layer fracturing technology for deep, high temperature and high pressure gas wells in Kuqa piedmont

The multi-packer separate layer fracturing operation in the deep, high temperature, high pressure, low porosity and low permeability gas reservoirs of Kuqa piedmont area tends to suffer packer failure, steel ball blocking pipe string and incomplete fluid displacement at the lower part of perforation interval, which are the key problems impacting the success of reservoir stimulation operation. In order to solve these problems, the completion string was installed with a slip joint to extend to the bottom boundary of the perforation interval. A kind of high-strength dissoluble ball of aluminum alloy was developed, which takes the composite organosilicon resin coat with the transitional layer of melamine as the special protection film, has pressure bearing strength more than 69 MPa and dissolves slowly first and then fast. In addition, a kind of full-bore fracturing valve was developed, which adopts ratchet-type structure and dropping-to-pressurizing mode. When the side hole is opened by the sliding sleeve, the hole is enlarged to run the ball through it to the bottom of the string, so that the full bore can be kept consistent with the lower packer. Thus, the multi-packer separate layer fracturing technology suitable for deep, high temperature, high pressure deep gas wells was formed. It has been applied on site 14 well times, and no packer failure, string blocking or incomplete fluid displacement occurs during the fracturing. The analysis indicates that slip joints can alleviate the axial force generated by temperature effect and inner-outer pipe pressure difference; dissoluble balls avoid the occurrence of retention blockage while meeting the requirements of fracturing operation; extension string, combined with full-bore fracturing valve provides the channels for the effective injection of fracturing fluid and displacement fluid in the perforation intervals, so as to solve the settling blockage of drilling fluid in perforation intervals and the deposition of proppant at the bottom hole. In conclusion, the multi-packer separate layer fracturing technology can provide reliable technological support for the reservoir fracturing stimulation of deep, high temperature and high pressure gas wells.