WATER DUMPFLOOD INTO MULTIPLE LOW-PRESSURE GAS RESERVOIRS

Abstract

Water dumpflood into nearly abandoned gas reservoirs is a new promising approach to increase gas recovery by maintaining the reservoir pressures with much cheaper costs than waterflooding. Thus, a simulation study of water dumpflood into multiple nearly abandoned thin-bedded gas reservoirs commonly found in the Gulf of Thailand was conducted to demonstrate the advantage of the proposed method and to determine the most suitable operation conditions for reservoirs having different system parameters. This simulation study found that water dumpflood can increase gas recovery up to 10.5% depending on operational conditions and system parameters. It is best to start water dumpflood when the gas rate is below the plateau rate for systems having a large aquifer and long distance between wells because the long well distance helps delay water breakthrough and earlier dumpflood operation requires shorter production duration. On the other hand, for the systems having a large aquifer and short distance between the two wells, performing water dumpflood when the rate is close to the economic rate is better because water is more likely to cause an early breakthrough when the distance is short. For system having small or moderate aquifer size, water breakthrough is more likely to occur later, thus, dumpflood should be performed when the gas rate is below plateau as it requires shorter production duration. However, if booster compressor is used, water dumpflood is not recommended to perform because it yields very small incremental recovery factors.