Latest Technological Progress in Drilling and Completion Operations of the Unconventional Reservoir in Xinjiang MaHu Oil Field and Key Suggestions for the Next Steps
Authors: Hu Huaigang , Xi Chuanming , Ji Guodong , Zhang Nan , Wu Qiang , Zhuo Lubin , Zou Lingzhan 
Published: February 2025

Due to the differences in sedimentary environments, compared with the exploitation of unconventional oil and gas resources in the United States and other countries, China has encountered greater difficulties in the drilling and completion processes of unconventional oil and gas. By analyzing the problems faced by drilling and completion in unconventional reservoirs in the MaHu area in recent years, the process of solving the issues and technical progress are summarized to form a technical template for drilling and completion in this area, which can also provide references for the next step to improve the drilling efficiency and reduce development costs.

By studying the lateral distribution law of the pore pressure, the placement of the technical casing was optimized to further develop a standard design for the wellbore structure applicable to this area. To adapt to the local environmental protection requirements, high-performance non-sulfonic treatment agents were selected to replace sulfonic treatment agents, and four sets of environmental protection drilling fluid systems were formed. Based on the rock mechanics and field tests, the personalized drill bit is continuously optimized. With the introduction of a rotary steering drilling system and high-performance positive displacement motor (PDM), the rate of penetration (ROP) has been greatly improved.

The transformation of horizontal Wells in the target Triassic formation from four types of casing strings with open hole completion + White oil-based/potassium-calcium based polysulfone organic salt drilling fluid to three types of casing strings with 5-inch casing completion + white-oil/potassium-calcium polyamine organic salt drilling fluid, from conventional rotary drilling + roller cone bit to rotary steering system/high-performance PDM +PDC bit, and the horizontal section length increased from 2000m to 2650m. Completion time decreased from an average of 144 days to 72 days. Speak of the Permian formation, the transformation from four types of casing strings with open hole completion + potassium-calcium based polyamine organic salt drilling fluid to three types of casing strings with 5.5-inch casing completion + white-oil based drilling fluid, from conventional rotary drilling + roller cone bit to rotary steering system/high-performance PDM +PDC bit, and the horizontal section length increased from 1070m to 1600m. Completion time decreased from an average of 175 days to 82 days.

It is a typical unconventional glutenite reservoir in the MaHu area of Xinjiang Oilfield, with tight lithology and poor drillability. The development layers have a large span and differences on the plane. The local fractures developed with seriously lost circulation. For the above-mentioned issues, targeted breakthroughs are still needed in the next step. By summarizing the progress of drilling and completion technology in recent years, it is expected to provide a mature scheme that can be used for reference and transplanted for the exploration and development of other similar reservoirs.