(236e) Simulation Study on Huff-n-Puff Gas Injection to Enhance Condensate Recovery in Fractured Shale Gas Reservoirs

Nowadays, production of liquid dropout -"condensate" in shale gas reservoirs has attained more and more attention. In shale gas reservoirs, when the pressure decreases below the dew point pressure, the heavy part of gas will be dropped out. This liquid dropout is "condensate". The condensate has a very good economic value since it contains the heavier components of initial gas. A critical issue is that the condensate would accumulate near the wellbore and could reduce the productivity of gas. Thus, enhance condensate recovery in shale gas reservoirs could allow producers to make full use of the economic value of condensate, and also it could improve the gas productivity in shale gas reservoirs.

In this paper, a numerical simulation approach is applied to evaluate the enhanced condensate recovery potential in a fractured shale gas reservoir by Huff-n-Puff gas injection. In the simulation work, different types of gas: N₂, CO₂, and CH₄ were injected into the reservoir through different injection schemes. The injection schemes include different injection pressure, different injection rate, different soaking time, different depletion pressure and depletion rate.

The compositional simulation results indicate that the hydraulic fractures are critical to enhance condensate recovery. Furthermore, by using huff-n-puff gas injection method, the condensate recovery is increased in the range of 15% to 30% in all cases and CO₂ injection is more effective than CH₄ and N₂.