Development of Keshen ultra-deep and ultra-high pressure gas reservoirs in the Kuqa foreland basin, Tarim Basin: Understanding and technical countermeasures

Abstract

The Keshen Gas Field in the Kuqa foreland basin, Tarim Basin, is a rare fractured tight sandstone gas reservoir with ultra-depth and ultra-high pressure. During its pilot period of gas field development, the development effect is poor with a low development well success rate, a low utilization rate of production capacity and a rapid decline of gas well productivity. In view of these problems, development experiments and technological researches were carried out continuously after the geological characteristics of gas reservoirs, productivity control factors, reservoir connectivity, seepage characteristics, gas and water relations and water invasion laws were studied thoroughly. And consequently, the development countermeasures of “well placement in high position, moderate stimulation and early-stage drainage” were prepared, and five matching development technologies were formed, such as description technology of ultra-deep complex structures, well pattern optimization technology for fractured tight sandstone gas reservoirs, fracture net acid fracturing technology for fractured tight sandstone reservoirs, dynamic monitoring technology for ultra-deep and ultra-high pressure gas wells, wellbore integrity management and evaluation technology for high pressure gas wells. The following remarkable application results were achieved in the process of gas field development. First, the drilling depth error of the target formation drops from 125 m to less than 30 m. Second, the utilization rate of production capacity in the Keshen 8 Block reaches 100%. Third, the average absolute open flow rate is increased by 5 times to 273 × 104 m3/d from 50 × 104 m3/d before the stimulation. Fourth, safe and smooth production under high temperature and high pressure conditions is realized in the Keshen Gas Field. In conclusion, the successful and efficient development of the Keshen Gas Field provides experiences for the development of similar gas reservoirs at home and abroad, and its development countermeasures and matching technologies have important guidance and reference significance.