Recommended Practices and Lesson Learnt from High-Efficient Hydraulic Fracturing Towards China's Unconventional Resources Recovery

Abstract

Abstract The latest research progress in the field of unconventional oil and gas reservoir hydraulic fracturing technology in China from the aspects of fracturing process optimization, electrification of fracturing equipment, upgrading of key devices, development of dissolvable materials, and R&D of downhole tools were proposed in this paper. Particularly since 2020, through a large amount of technical research and field trials, a comprehensive upgrade of the hydraulic fracturing technology system has been realized, supporting the confirmation of shale oil and gas geological reserves and the construction of scale benefits in the Sichuan Basin and Ordos Basin. The electrification upgrade of fracturing equipment was continually on the way, in 2022, the number of electric driven fracturing operations by PetroChina reached 8,474, with an electricity replacement rate of 27.4%, saving 39,000 tons of diesel and reducing carbon emissions by 32,000 tons. Two types of dissolvable magnesium alloys were developed, with high-strength dissolvable magnesium alloy having a tensile strength of over 500MPa and a high elongation dissolvable magnesium alloy having an elongation rate of over 60%. The high-strength magnesium alloy was used as the core component of the delay mechanism in the delay toe sliding sleeve, ensuring the reliability of the toe sliding sleeve during the whole wellbore pressure test and sliding sleeve opening, improving the efficiency of the first section fracturing process in horizontal wells. The high-strength magnesium alloy was also used for the main body of bridge plug, and the high elongation rate dissolvable magnesium alloy was used as the sealing part, improving the sealing pressure performance from 70MPa to 90MPa and widening the temperature tolerance range to 20-200°C. In 2022, more than 20,000 sets of dissolvable bridge plugs were used by PetroChina. The composite low-density temporary plugging ball was developed, based on high-strength magnesium alloy with a hollow design wrapped in dissolvable rubber, allowing for variability in density and shape within a certain range, and field tests of temporary plugging fracturing showed an average pressure increase of 11.2MPa. The comprehensive progress of domestic hydraulic fracturing technology systems from process to equipment, tools and materials has promoted the low-carbon and efficient utilization of unconventional resources and provided feasible technical ideas for the next step of high-quality development.