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Huff-n-puff injection in shale gas condensate reservoirs 105
Earlier, huff-n-puff methane and methanol injection in shale gas-
condensate cores are compared. Because of the ease of methane injection
and flowback compared with methanol, methane injection is preferred to
methanol injection. This surfactant is solubilized in the solution which
consists of 94% methanol. Obviously, this surfactant cannot be more
economic than methane injection.
4.9 Factors that affect huff-n-puff gas injection
performance
To better understand the mechanisms and optimization of huff-n-puff
gas injection, several relevant factors that affect the performance are discussed
in this section. These factors include initial reservoir pressure, huff pressure,
puff pressure, cycle time, soaking time, and CO 2 gas component.
4.9.1 Effect of huff pressure
From Fig. 4.7, it can be seen that the first cycle produced the highest
condensate recovery. Meng et al. (2015a) found that higher injection
(huff) pressure resulted in higher condensate recovery; with the pressure
higher than the dew point, the effect of pressure became less significant,
as shown in Fig. 4.25. A gas condensate mixture of 85% methane and
15% butane was used in the experiment.
Figure 4.25 Effect of injection pressure on condensate recovery.
