Page 114 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Huff-n-puff injection in shale gas condensate reservoirs 101

Figure 4.23 Total individual hydrocarbon recovery factors from different operation
schemes.

injection recovers more methane than the solvents and butane similar to the
solvents.
To include the effect of total injection volume and its cost, the recovery
factors are corrected (called corrected recovery factor, RF c ). It is defined as:

RF %
RF c ¼
ðUnit volume cost of fluid*Total volume of fluid injectedÞ $MM
The unit volume costs of the injection fluids are listed in the preceding
section. This defined RF is only used to compare the relative economic
performance. The corrected recovery factors for different gases and solvents
are shown in Fig. 4.24. Gases outperform solvents. Although the corrected
recovery factors for the two gases decrease with time, the corrected recovery
factors for solvents stay relatively flat.

4.7 A field case of methanol injection
Hatter’sPondgas field had permeability of 2e6 mD, and porosity of
12%e15%. The dew point pressure was 3030 psi which was higher than
the initial reservoir pressure of 2700 psi and the well flowing pressure of
2000 psi. The liquid dropout at 2000 psi was 33%. Such rich gas made a
studied well production rate gradually decrease from 2.7 MMscf/d gas and