Abstract: About estimation of gas in place for gas reservoirs as confined fracture-vuggy carbonate, some generally recognized classical formulas were available before.But prediction and estimation of consealed gas in place from water-gas producers within a fracture-vuggy carbonate trap is a new challenge in recent years, Based on material balance priciple, such formulas are deduced, a new concept of “discounted gas concentration"is presented in this paper, and pressure drawdown diagram of P/Z vs G_p for water-gas producer is established by which prediction of consealed gas in place for water producers can also be made.This technique has been verified from the case estimation of Well H16.

Key words: Carbonate rock, Fracture, Cave, Subtle trap, Gas Reserve, Prediction