CNPC discovers shale gas in the atmospheric zone
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On September 29, CNPC announced significant exploration results in the field of unconventional oil and gas. This year, significant progress was made in the exploration of shale gas in the Sichuan Basin. New proven geological reserves of shale gas were identified in the Changning-Weiyuan and Taiyang areas, amounting to 740.971 billion cubic meters; the total proven reserves now stand at 1061.03 billion cubic meters, thereby establishing a shale gas reserve area of trillions of cubic meters in the Sichuan Basin. In the field of shale gas exploration and development, CNPC has established two **-class shale gas demonstration areas in the Sichuan Basin, namely Changning-Weiyuan and Zhaotong. It achieved more than 10 firsts in China, including the first vertical shale gas well, the first horizontal shale gas well, the first commercially viable horizontal shale gas well, and the first shale gas \"factory-style\" operation platform. Over time, it has developed a set of technologies suitable for shale gas exploration and development under the complex geological and topographical conditions of the Sichuan Basin, playing an important role in promoting the large-scale and efficient exploitation of shale gas resources in China. This year, 7.7 billion cubic meters of shale gas are expected to be produced, and by the end of the year an annual production capacity of over 10 billion cubic meters will have been established. Especially since 2018, an additional 740.971 billion cubic meters of proven shale gas reserves have been identified, bringing the total proven reserves to 1061.03 billion cubic meters; this has created a shale gas resource area with reserves in the trillions of cubic meters, which is of great significance for enhancing China’s natural gas supply capacity.
The Longmaxi Formation in the Nanning–Weiyuan area, located in the southern part of the Sichuan Basin, is rich in shale gas resources, and its shale reservoirs possess good quality; it was designated as a **-grade shale gas demonstration area in 2012. To provide valuable experience for the exploration and development of shale gas in China, this study summarizes the key technologies developed and the achievements attained at each stage, based on an analysis of the exploration and development process in this demonstration area, with the aim of laying a solid foundation for taking shale gas exploration and development in the Sichuan Basin to a new level. The research findings show that: ① Through more than 10 years of continuous exploration, the exploration and development of shale gas in southern Sichuan has gone through three stages – layer assessment and site selection, pilot tests, and the establishment of demonstration areas – and it has now entered a new phase of development ； ②The construction of this demonstration area underwent 3 rounds of optimization and adjustment: in the first round, the main technologies specified in the development plan were strictly followed when drilling production wells; in the second round, the design and engineering solutions were comprehensively optimized; in the third round, integrated geological and engineering technologies were widely applied. These three rounds of adjustments improved the designs, refined the main technologies, and increased the output per shale gas well ； ③To date, this demonstration area has achieved an annual shale gas production capacity of 25×108 m3. It has mastered the methods and techniques for the effective development of shale gas at depths of up to 3,500 meters. Thanks to continuous technological advancements, large-scale and efficient development of shale gas has been initially realized. It is concluded that during the development of this shale gas demonstration area, the evaluation of shale gas resources was continuously refined, the resources and distribution in viable areas were identified, and the necessary infrastructure was established; thus, the conditions are now ripe for rapid production of shale gas in southern Sichuan.
The **-class shale gas demonstration area in Zhaotong is characterized by minor structural variations and well-developed fractures, poor stress conditions, and thin reservoir layers; as a result, it is difficult to control the drilling trajectory in horizontal wells, making efficient development of shale gas challenging. By taking into account comprehensive geological and engineering factors and conducting overall consideration, trajectory optimization control is implemented to establish a drilling model that enhances speed and efficiency, with economic benefits as the guiding principle. The core of this approach lies in continuously exploring the spatial distribution patterns of high-quality shale reservoirs and selecting the most suitable drilling techniques through pre-drilling analysis, in-drilling optimization, and post-drilling evaluation. By utilizing a combination of element logging and real-time gamma control technologies, seismic guidance at each point, ant-body and visual polarity-based early warning systems, as well as optimized steering tools, it is possible to achieve accurate landing of the drilling rig in the target area and precise navigation through horizontal sections. This ensures a high success rate in reaching high-quality reservoirs in these horizontal sections as well as smooth drilling trajectories, thereby continuously improving the quality of drilling and laying a solid foundation for achieving high yields per well. The integrated geological engineering steering technology has demonstrated significant effectiveness in practical applications.