Development of High-Performance Completion and Stimulation Techniques for 200°C Extreme High-Temperature Reservoirs

The Kunteyi block is one kind of an ultra-deep, ultra-high pressure, and ultra-high temperature bedrock gas reservoir in the Qaidam Basin. The extreme reservoir characteristics of 7000m+ and 200°C pose significant challenges to well completion and stimulation. Three major challenges are: 1) lack of experience in well completion operations for ultra-deep reservoirs at 200℃; 2) what kind of well completion and Stimulation technology can meet the requirements for maximizing well productivity; 3) whether the performance of tools and fluids at 200°C meet the process requirements. This paper introduces four well completion and stimulation technologies for 200℃ deep wells, and provides field application scenarios and experiences of different types of well completion and stimulation. The well completion can be divided into four stages: First Stage: For the first well in this block, the THT completion packer was used after combined logging and perforation operations. Second Stage: The integrated acidizing completion string was adopted, which comprises single/multi-layer acidizing strings combined with THT permanent packers. Third Stage: After tubing perforation, an acidizing string with Y531 packers was used for well completion, followed by pilot production testing. Fourth Stage: For the ultra-deep, high-angle wells in this area, a combined plugging and perforation operation with casing fracturing stimulation was employed for well completion. Furthermore, the corresponding perforation technologies, types of packers, staged plug types, pressure-bearing calculations for hangers, and the performance of corresponding well completion tools for each of these four processes are introduced in detail. The reverse design and forward implementation method significantly reduce downhole accidents such as wellbore blockage and pipe sand burial. For a 7-inch + 5-inch wellbore, the selection of a THT packer corresponding to the 7-inch casing is optimized, with performance requirements meeting 103.4MPa pressure resistance and temperature resistance of 232°C. Field tests have shown that a downhole hanger with a pressure-bearing capacity of 105MPa can meet the stimulation treatment requirements, but there are certain risks involved. For subsequent wells, theoretical calculations have optimized the selection of a hanger with a pressure-bearing capacity of 140MPa. The perforating gun is preferably an ultra-high temperature 89-gun, using a second-generation-plus bullet type, which has a temperature resistance of 210°C/48h and a pressure resistance of 175MPa. Moreover, the ultra-high temperature fracturing fluid has achieved a 74% drag reduction, and the ultra-high temperature acid fluid has reduced the construction pressure by up to 15.4 MPa. This paper presents a novel integrated design approach for completion and stimulation for ultra-deep and ultra-high temperature wells. Four different completion techniques and treatment experiences are shared, providing referenceable insights and practical experience for optimizing well completion and reservoir stimulation in ultra-deep reservoirs at 200℃.