Performance Evaluation of CO2 Huff-n-Puff Gas Injection in Shale Gas Condensate Reservoirs

Abstract

When the reservoir pressure is decreased lower than the dew point pressure in shale gas condensate reservoirs, condensate would be formed in the formation. Condensate accumulation severely reduces the commercial production of shale gas condensate reservoirs. Seeking ways to mitigate condensate in the formation and enhance both condensate and gas recovery in shale reservoirs has important significance. Very few related studies have been done. In this paper, both experimental and numerical studies were conducted to evaluate the performance of CO2 huff-n-puff to enhance the condensate recovery in shale reservoirs. Experimentally, CO2 huff-n-puff tests on shale core were conducted. A theoretical field scale simulation model was constructed. The effects of injection pressure, injection time, and soaking time on the efficiency of CO2 huff-n-puff were examined. Experimental results indicate that condensate recovery was enhanced to 30.36% after 5 cycles of CO2 huff-n-puff. In addition, simulation results indicate that the injection period and injection pressure should be optimized to ensure that the pressure of the main condensate region remains higher than the dew point pressure. The soaking process should be determined based on the injection pressure. This work may shed light on a better understanding of the CO2 huff-n-puff- enhanced oil recovery (EOR) strategy in shale gas condensate reservoirs.

Effects of Moisture Contents on Shale Gas Recovery and CO2 Sequestration

“…The dynamics and transport processes are not considered . This process achieves one cycle of CO 2 huff-n-puff in enhanced gas recovery. , Consequently, a second CO 2 huff-n-puff process is operated.…”

“…65 This process achieves one cycle of CO 2 huff-n-puff in enhanced gas recovery. 6,66 Consequently, a second CO 2 huffn-puff process is operated. Evolution in the composition of fluids in the kerogen slit pores during the shale gas recovery process is shown in Figure 11.…”

Influence of CO2 retention mechanism storage in Alberta tight oil and gas reservoirs at Western Canadian Sedimentary Basin, Canada: hysteresis modeling and appraisal

“…Besides, the rate of CO 2 molecular diffusion is also higher in this case. Meng et al (2018) conducted a performance evaluation of carbon dioxide huff-n-puff gas injection in shale gas condensate reservoirs. Initially, the authors studied the phase behaviour of shale gas condensate reservoirs and found that when the reservoir pressure falls below the dew point the condensate occurs and this is the major problem in this type reservoir.…”

Insights into recovery of multi-component shale gas by CO2 injection: A molecular perspective

“…After the primary pressure drawdown stage, the reservoir pressure is reduced to 25 MPa and then two successive CO2 huff-n-puff cycles are performed as in our recent work [18]. One CO2 huff-n-puff cycle is achieved by first injecting CO2 into the shale gas reservoirs and then applying a pressure drawdown process after the system has reached equilibrium [50,51]. Here GCMC simulations instead of MD simulations are conducted to obtain the equilibrium properties of hydrocarbon mixtures and CO2 in kerogen nanopores.…”