Progress of normal-pressure shale gas engineering technology in southeast Chongqing and the research direction of next steps

Abstract

The normal-pressure shale gas block in southeast Chongqing is located in the transitional zone of the basin margin and the extrabasinal fold area, which has the geological characteristics of complex structure, large stress difference and low pressure coefficient, which brings great challenges to improve the efficiency and production of engineering technology. Shallow surface fractures and caverns are developed in this area, with many thief zones, and long drilling and completion period. The structural stress changes quickly and the difference coefficient is large, so it is difficult to form complex fracture network. The lack of formation energy and low drainage efficiency affect the continuous and stable production of gas wells. Therefore, with the goal of "increasing quality, speed, efficiency and yield", key technologies are innovated and implemented, and the benefits of engineering processes are created constantly. With the aim to "speed up, improve efficiency and reduce cost" in drilling projects, the normal-pressure shale gas drilling and completion technology is formed, which focuses on well structure optimization and drilling with optimized parameters, and integrates equipment and tools. The mechanical drilling rate increases by 14.90% per year, the drilling and completion period decreases by 10.67%, and the drilling cost decreases by 7.64%, setting multiple new records in the same period. Focusing on increasing efficiency and reducing cost of fracturing projects, fracture complexity is improved through "moderately close cutting + temporary plugging and turning", effective multi-scale support of fracture network is promoted by "high-strength sand injection + sand-ceramic particle size combination", low-cost fracturing materials and cost-reduced equipment and tools are integrated and applied, forming the characteristic fracturing process and supporting facilities of "complex fracture network + economic materials + intelligent fracturing equipment". The final EUR of one kilometer per well was increased from 34 to 45 million cubic meters, and the cost decreased by 34.6%. With the goal of "fine management of the whole life cycle, delay of decline, and efficiency improvement by tapping the potential", the full-life cycle drainage and gas production technology system of mechanical drainage such as early selection of pipe string, mid-stage foam drainage + compressor depressurized mining, late-stage single pipe jet pump and heavy-duty pump + liner pipe has been established, and precise policies have been implemented in different areas, classification and stages, and the annual decline rate of old wells has been reduced by 2.1%. The production time rate of the whole field increased from 95.9% to 98.7%. Through the research on the whole process of engineering technology, it strongly supports the efficient development of normal-pressure shale gas in southeast Chongqing, and provides beneficial reference for the efficient exploitation of other normal-pressure shale gas.

Keywords

• two-cut drilling
• fracturing of fracture network
• drainage gas production
• benefit exploitation
• normal-pressure shale gas
• southeast chongqing