Exploration and development in the Zhaotong national shale gas demonstration area: Progress and prospects

Abstract

The Zhaotong national shale gas demonstration area in Yunnan (hereinafter referred to as demonstration area) is China's third largest national shale gas production base after Changning–Weiyuan in Sichuan and Fuling in Chongqing. And after more than ten years of deep and careful cultivation, a series of important achievements have been obtained in the exploration and development. From the perspective of exploration and development history, theory and technology, this paper systematically summarizes the exploration discovery process and productivity construction progress of shale gas in the demonstration area, expounds the geological exploration theories and key technologies of mountain shale gas, and predicts their development prospect and direction. And the following research results are obtained. First, the exploration and development in the demonstration area has gone through five development stages, and so far, three major productivity construction zones have been formed, including Huangjinba and Zijinba middle–deep shale gas zones and Taiyang shallow shale gas zone, with cumulative proved geological reserves more than 3100 × 108 m3 and cumulative gas production more than 72 × 108 m3. It has been constructed into the third largest green shale gas demonstration base in China. Second, the “multi-field coordination and multi-element coupling” mountain shale gas enrichment, accumulation and occurrence theory of “sedimentary background controlling source rock and reservoir, reworking intensity controlling preservation, and three-dimensional sealing controlling enrichment” is put forward innovatively, and the “three-dimensional sealing system” accumulation model of extrabasinal shallow shale gas is established. Third, a series of zone selection and evaluation technologies for mountain shale gas in strongly reworked complex structural areas have been developed, and the concept of geology–engineering integration has first been adopted to create transparent shale gas reservoirs and cultivate high-yield wells. A major exploration breakthrough has been achieved from marginal basin medium deep shale gas layers to extrabasin ultra shallow to medium shallow ones, and domestic first large-scale monoblock shallow shale gas field with reserves over 2570 × 108 m3 has been discovered. Fourth, a landmark technological achievement and efficient development model with geology–engineering integration and shale geomechanical evaluation as the core has been formed, which leads the clean, green and efficient exploration and development of mountain shale gas. In conclusion, it is necessary to implement the exploration strategic idea of “two outgoing” in the demonstration area, i.e., “walking out of the stable area of the basin and marching into the complex structure areas in the Dianqianbei Depression” and “walking out of the Wufeng–Longmaxi Formation and exploring other layers for breakthrough”. What's more, it is recommended to carry out the double-layer stereoscopic horizontal well pattern deployment of “Leping Formation CBM (coal measure gas) + Longmaxi Formation shale gas” appropriately in a large scale, so as to establish a new integrated development model for the three-dimensional efficient development of mountain shale gas and CBM.