Experimental and numerical study of enhanced condensate recovery by gas injection in shale gas-condensate reservoirs

This paper examines the potential of huff 'n' puff gas-injection method to recover condensate in shale gas-condensate reservoirs by conducting experiments on a shale core. Numerical models were developed to verify experiment results. Our laboratory study shows that condensate recovery was increased to 25% by applying huff 'n' puff gas injection on a shale core. Also, we compared the efficiency of huff 'n' puff gas injection with that of gasflooding. At the end of same flooding with time that is the same as the time for five huff 'n' puff cycles, the condensate recovery is 19%. From the experimental results, we found that huff 'n' puff was more effective than gasflooding. During the experiment, condensate accumulated near the production-end region. In the huff 'n' puff process, because the location for injection in the core was the same as that for production, the pressure in the condensate region built up faster than pressure in the flooding experiment. Also, because of the ultralow permeability, the pressure propagation was much slower in the shale core than in a conventional reservoir core, and the efficiency of gasflooding is much lower than that of the huff 'n' puff. This study indicates that huff 'n' puff has the potential to effectively enhance condensate recovery in shale gas--condensate reservoirs.