Large-scale fracturing technology suitable for casing damaged wells in Daqing Oilfield and its supporting tools

There are cumulatively about 10 thousand casing damaged wells in Daqing Oilfield. In order to activate the potential wells whose fracturing degree is low and remaining oil is relatively enriched, large-scale multi-stage fracturing technology was researched in this paper. Firstly, the relationships of shoulder angle and length of rubber cylinder vs. stress were analyzed by using the finite element analysis software, and the temperature and pressure resistance of rubber cylinder in the case of great deformation was verified by conducting oil immersion experiments. Then, the size of key components was adjusted and optimized by using the independently developed software, and the supporting tools were designed. It is eventually determined that the shoulder angle of rubber cylinder in the pony packer is 50° and its length is 550 mm. In addition, small-diameter sand blower is applicable to the casing damaged wells whose casing ID is larger than 104 mm and its technological coverage rate is increased to 70%; the novel anchor tool can ensure tools to run through the casing damage points while keeping the string stable; and bi-functional blowout preventing packer can realize the isolation of target layer and the blowout prevention of tubing. Field test results show that this technology and its supporting tools can be used for fracturing of casing damaged wells. In one trip of string, 5 layers can be fractured with proppant of 289 m³. Thus, the large-scale fracturing of casing damaged wells is preliminarily realized.