HT/HP Fracturing Process String Evaluation and Application in Deep Volcanic Gas Reservoir

Abstract The function of the fracturing strings is to transfer mechanical energy to crack the formations, and conduct proppant to the formations. Because the deep volcanic reservoir has the properties of deep burial, tight and complex formation lithology, the fracturing operations in such reservoir may encounter the issues of high downhole temperature, high operation pressure and high operation friction. The conventional fracturing strings are not capable of overcoming these problems. The fracturing strings are facing the following challenges: 1. Deeply buried volcanic reservoirs, which are normally deeper than 3000 meters, have very high temperatures, which are higher than 150 degrees Celsius. How to improve the temperature adaptability of the fracturing rubber packer is technically challenging. 2. The formation lithology of volcanic reservoirs is tight and complex, the initiation and extension of the fractures are relatively difficult. The operation pressure is high, so that the fracturing strings and other downhole equipment have to be able to sustain this high pressure. 3. Due to the high discharge rate and large scale operation in the process of volcanic reservoir fracturing, the fracturing strings should have low streamwise friction, strong anti-proppant erosion ability. In order to meet these challenges, we conduct the research on the fracturing equipment and fracturing strings used in the volcanic reservoirs. By studying the theoretical mechanics, optimizing packer structure, improving the temperature and pressure bearing ability of rubber packers, we design special tools such as anchoring tools to improve the adaptability of the fracturing technique, and also generate the safety specifications and operating regulations for the fracturing tools stripping in and out in the deep gas reservoir wells. All these achievements make the large scale fracturing remodeling of the deep gas volcanic reservoir possible. After the field tests, the success ratio is 97.5%.