Mechanism and Feasibility Analysis of Gas Injection for Enhanced Recovery in Fractured Tight Sandstone Gas Reservoirs: A Case Study of the Keshen 24 Gas Reservoir

The Keshen 24 gas reservoir is a typical fractured tight sandstone gas reservoir currently confronting challenges such as rapid water invasion, limited efficacy of conventional water drainage techniques, and escalating water encroachment, necessitating the exploration of effective enhanced recovery technologies. To address the geological and development conflicts in this reservoir, a systematic feasibility study on gas injection for enhanced recovery was conducted through mechanism investigation, theoretical calculation, and field testing. The research clarifies three core mechanisms of gas injection: replenishing formation energy, forming a gas barrier to suppress water influx, and mitigating water-blocking effects. The pressure gradient of nitrogen in the wellbore and a reasonable injection pressure window were determined through calculation. Key gas injection parameters were predicted by establishing a dual-porosity material balance model. Finally, a pilot well was selected for a field injection test, which practically validated the technical feasibility. The study demonstrates that gas injection is an effective and viable technology for enhancing recovery in the Keshen 24 gas reservoir and similar fractured tight sandstone gas reservoirs.