Evaluation of Combined Gas Dumpflood with Gas Injection into Gas Condensate Reservoir

Abstract

Conventional gas injection is an improved condensate recovery technique by injecting the gas from surface to displace condensate and maintain the reservoir pressure above the dewpoint pressure as long as possible. However, this method requires large volume of gas to be injected into the reservoir and incurs high capital and operating costs. Gas dumpflood is a condensate recovery technique achieved by allowing the gas from an underlying source gas reservoir to flow through dumping well to displace condensate and maintain the reservoir pressure. Gas dumpflood has lower capital and operation cost. Nevertheless, some of the source gas reservoir is small and may not be enough to recover condensate effectively. In order to extract more condensate, combined gas dumpflood with gas injection should be applied. A reservoir model was built by using ECLIPSE300 compositional simulator to predict gas and condensate production under different production scenarios including natural depletion, conventional gas injection, gas dumpflood, and combined gas dumpflood with gas injection. Effects of well location, source gas reservoir size, and gas injection rate were investigated. If 0.5 PV (small) source gas reservoir is available, conventional gas injection is the most appropriate technique to recover condensate. If 1 PV (medium) source gas reservoir is available, combined gas dumpflood with 10 MMscf/d gas injection rate is more attractive. If 2 PV (large) source gas reservoir is available, gas dumpflood should be considered. If of all 0.5, 1, and 2 PV source gas reservoirs are present, gas dumpflood from 2 PV is the most attractive.