Feasibility study of secondary gas production for PFW water-drive gas-cap reservoirs

Irrational production fashions during initial stage may cause premature water invasion in water drive gas reservoirs,thus resulting in a great deal of gas being trapped and incapable of being produced.It is feasible technologically and economically to change trapped gas into flowing gas through reducing the formation pressure of water sealed areas by large amount of water drainage.Based upon the three-phase three-dimensional simulation model,the development results of various secondary gas recovery were evaluated.The simulation results indicate that massive water displacement higher than formation water invasion speed will be beneficial for enhancing ultimate gas recovery factor,whereas it should be restricted by surface water processing facilities and economic factors.Horizontal well has distinct technical advantages in development of water drive gas reservoirs,especially bottom water-drive reservoirs.As for water drive gas reservoirs with normal formation pressure and moderate burial depth(not more than 3000 meters),the release of dissolved gas in the aquifer can only slow down the declining rate of formation pressure,and it won't have any remarkable influences on development results of gas reservoirs.The research results can provide us a new technical thinking for improving production results of water-drive gas reservoirs.