Page 144 - Enhanced Oil Recovery in Shale and Tight Reservoirs

128 Enhanced Oil Recovery in Shale and Tight Reservoirs

10,000

Pressure: PRES Block 2,16,1 (psi) 6,000
8,000

4,000

2,000

0
2015 2020 2025 2030 2035 2040
Time (Date)
Pressure: PRES Block 2,16,1
Figure 5.9 Near-wellbore block pressure in Case H100P100trans0.33 with its transmis-
sibility reduced 3 times from Case H100P100.

Fragoso et al. (2018b) found that longer cycle time (longer huff and puff
time) performs better than the shorter time, as more gas is injected, and
long production time is allowed. Their result is consistent with the above
discussion. They further found that the optimal schedule is such that the
cycle time increases with cycle, as more gas is produced so that more gas
is needed to supplement the voidage and a long time is needed to produce
the oil deep in the reservoir. They also proposed that refracturing and
huff-n-puff are combined to improve oil recovery.
Kong et al. (2016) found from simulation that the optimum huff-n-puff
CO 2 injection for the Cardium tight oil reservoir (0.2 mD) is 1 month of
huff time, 3 months of puff time, and selected 10 days of soaking time.
They found 0.7% more oil is produced in 5 years, if the huff time and the
puff time are increased by 5 days for each consecutive cycle.
Kong et al. (2016) also studied the interwell interference during
huff-n-puff CO 2 injection by comparing an asynchronous huff-n-puff
injection with the counterpart synchronous injection. In the synchronous in-
jection, all the wells perform huff, soak, and puff operations at the same pace,
while in the asynchronous injection, when a group of wells are in the huff
mode, the rest of the wells are in the puff mode. They tested a three-well
sector. When the middle well is in the huff mode, the two side wells are