High-quality development of ultra-deep large gas fields in China: Challenges, strategies and proposals

Abstract Natural gas from ultra-deep reservoirs has been a major contributor for reserves boost, deliverability construction, and profits growth in natural gas industry in China. As a significant strategic domain in the future development of upstream business, the high-quality development of ultra-deep gas resources has great significance for economic benefits enhancement and sustained regional supply assurance. In this paper, based on the appraisal of development characteristics and effectiveness in the developed large ultra-deep gas fields, challenges for high quality development were indicated, which include the difficulties in structure confirm, uncertainties in reserves define and production optimization, risks of aquifer water early breakthrough and high investment of deep wells. Through indoor physical simulation experiments, reservoir characterization, performance evaluation, reservoir simulation and knowledge acquisition from analogous fields at home and abroad, the connotation and requirements for high quality development were discussed, and furthermore, strategies and proposals were thus proposed as follows: to strengthen the pre-development reservoir evaluation to define movable gas reserves and quantify rational production rate so as to avoid facility waste; to optimize both well pattern and well flow rate to achieve uniform depletion and high EUR; to continuously enhance drilling & completion technologies to further reduce drilling and completion circle and cost and targeted reservoir stimulation technologies to enhance movable reserves and single-well productivity and increase the depletion of inferior reserves; and to innovate management modes to establish scientific programs and procedures for the construction, production and operation of ultra-deep gas fields and strictly control the upper limit index of production rate so as to emphasize quality benefits. In conclusion, high-quality development of ultra-deep gas fields, a hard and complex system though, will be possibly achieved only by continuous innovation of exploration and development technologies and management modes.