Key technologies for well completion and commissioning of ultra-deep sour gas reservoirs in the Yuanba Gasfield, Sichuan Basin

The Yuanba Gasfield is another large gas field with reserves of a hundred billion cubic meters that was discovered by Sinopec after the Puguang Gasfield in the Sichuan Basin. At present, it is the deepest marine carbonate sour gas field in China. Its principal reservoir, the Upper Permian Changxing Fm, is characterized by ultra depth, high temperature, high sulfur content, high CO2 content, and complex gas-water relationship. Therefore, well completion is faced with complicated engineering geological conditions, diverse well types and well completion modes and high-difficulty operation. In view of this, Sinopec Southwest Petroleum Engineering Co., Ltd. carried out technical research and practice. As a result, a series of key well completion and commissioning technologies were developed, including well completion testing and ground control, in-depth acid fracturing stimulation, ultra-deep slim-hole wellbore processing, micro-tooth mark make-up and air tightness detection, and safety control. Based on these technologies, the worldwide technical difficulties of well completion and commissioning in the process of gas field development are settled, such as string corrosion prevention, in-depth acid fracturing, high-yield testing, and safety control. These technologies have been applied successfully in nearly 40 wells, providing an important technical support for the realization of 34 × 108 m3 annual gas production capacity construction in the Yuanba Gasfield.