Evaluation of Enhanced Condensate Recovery Potential in Shale Plays by Huff-n-Puff Gas Injection

Abstract

AbstractIn gas condensate reservoirs, production performance is compromised by the liquid dropout due to reservoir pressure depletion below the dew point pressure. In the shale gas-condensate plays, the condensate banking caused by a high pressure drop further reduce the productivity of the well. Evaluation of the condensate banking effect in shale reservoirs is critical to developing this type of shale condensate plays. Improving condensate recovery has a great economic potential to the oil industry. Condensate has a very good economic value because it contains heavier components in the reservoir. Also the reduction of condensate could increase the relative permeability of gas, the gas production could be improved. Published research shows that condensate banking problem is more significant for low permeability condensate systems. Therefore, this study to focus on this important issue: enhancing gas-condensate recovery in shale gas reservoirs.In this paper, huff-n-puff gas injection in a shale gas reservoir is simulated to enhance gas-condensate recovery. The model used in the simulation work is calibrated with our enhanced condensate recovery experimental data which shows that huff-n-puff can effectively improve condensate recovery.Based on the calibrated work, simulation study is performed to investigate the potential of huff-n-puff gas injection to enhance condensate recovery in shale plays. Different parameters are investigated in this simulation work: 1) different gas injection pressure, 2) different numbers of huff-n-puff cycles, 3) different soaking time.The results of both the experimental and simulation work show that huff-n-puff method can effectively improve condensate recovery. During the huff period of cyclic gas injection, the pressure is increased, and the liquid dropout will be re-vaporized and then recovered during the puff period. We used 5 cycles of gas injection to improve condensate recovery and found that the first cycle recovered most of the condensate in the laboratory. The recovery efficiency of subsequent cycles was declined. The simulation work shows the similar recovery profile as observed in the laboratory.Very limited research has been conducted to enhance condensate recovery in shale reservoirs. This paper focuses on examining the efficiency of huff-n-puff method to improve condensate recovery. Results indicate the applicability of huff-n-puff gas injection.