Page 103 - Enhanced Oil Recovery in Shale and Tight Reservoirs

90 Enhanced Oil Recovery in Shale and Tight Reservoirs

0.60
8,000
Oil Saturation: SO Block 10,28,4 0.40 6,000 Pressure: PRES Block 10,28,4 (psi)
0.50

0.30
4,000

0.20

0.10 2,000

0.00 0
2015 2016 2017 2018 2019 2020
Time (Date)
Oil Saturation: SO Block 10,28,4
Pressure: PRES Block 10,28,4
Figure 4.12 Pressure and oil saturation at Block (10,28,4) near the producing fracture in
the gas huff-n-puff mode.

producing fracture. In the gas huff-n-puff mode, the oil saturation at Block
(10,28,4) shoots up at the first huff because oil in the producing fracture
block (11,28,4) is displaced to this block.
Fig. 4.12 shows the pressure and oil saturation at Block (10,28,4) near the
producing fracture in the huff-n-puff mode. It shows that when the pressure
increases during the huff period, the oil saturation decreases almost to zero,
as oil is vaporized and flows with the gas stream, or some oil is displaced to
the producing fracture; when the pressure is decreased during the puff
period, the oil saturation is increased because of condensation or some oil
from the deep matrix flows into the block.
In conventional reservoirs, generally gas is flooded to maintain a high
reservoir pressure so that less condensate will occur (Thomas et al., 1995).
In shale or tight gas condensate reservoirs, for example, when the matrix
permeability of 100 nD in this studied model, higher liquid saturation occurs
at the producing fracture, because the pressure there is low (about 500 psi),
although the pressure in the injection fracture is 9500 psi, as shown in the
left-hand side of Fig. 4.13. The pressure near the injection side cannot prop-
agate to the production side in the low matrix permeability reservoir. For the