EARTH

[31013-24-02] Additional Gas Recovery in Nearly Abandoned Gas Reservoir via Water Dumpflood

○Suwat Athichanagorn¹ (1. Chulalongkorn University)

Chairman: Suwat Athichanagorn （Chulalongkorn University）, Dawan Wiwattanadate （Chulalongkorn University）

Keywords:Gas recovery, Water dumpflood

Depletion-drive gas reservoir is abandoned when there is insufficient bottomhole pressure to produce gas to surface. However, the remaining amount of gas in the reservoir could still be partly recoverable if the reservoir is pressurized. Waterflooding has been proposed to increase gas recovery in low-pressure gas reservoir near the abandonment condition. However, the process needs water injection which incurs capital and operating costs. This makes waterflooding in a nearly abandoned gas reservoir to be less attractive. Water dumpflood, which is the process that water from an aquifer is allowed to flow into the gas reservoir via the wellbore, could be a possible solution as there is no additional investment on water injection facility nor operating cost. In this study, a hypothetical reservoir was created using reservoir simulation software in order to investigate the performance of water dumpflood in a nearly abandoned gas reservoir. Several system parameters which are terminal wellhead pressure, size of water aquifer, and reservoir dip angle were varied in order to study their effect on incremental gas recovery. The simulation study found that the proposed technique can increase up to 9.84% additional gas recovery factor depending on the system and operational parameters. The investigation also found that the higher the terminal wellhead pressure, the more the difference between gas recovery obtained from natural depletion and water dumpflood near abandonment. As the size of the aquifer is bigger, the additional amount of gas recovery increases significantly due to stronger pressure support. As the dip angle of the reservoir and the aquifer is increased, the additional recovery factor is larger because of better segregation of gas and water.