Page 217 - Enhanced Oil Recovery in Shale and Tight Reservoirs

200 Enhanced Oil Recovery in Shale and Tight Reservoirs

Table 8.2 Pump schedule in a Woodford shale frac. job (Grieser et al., 2007).dcont'd
Conc., Ibm/
Stage Vol., gal Fluid gal Proppant
22 Sand slug 14,240 Treated water 0.64 Premium
Brown-30/70
23 Sand slug 14,240 Treated water 0.73 Premium
Brown-30/70
24 Sand slug 14,240 Treated water 0.82 Premium
Brown-30/70
25 Sand slug 14,240 Treated water 0.9 Premium
Brown-30/70
26 Flush 3,655 Pad and flush

shale frac job. About 3% HCl was used in the acid pad. The total acid pad
volume was about one-third of the total fracturing fluid volume.
Carbon dioxide (CO 2 ) EOR is a popular EOR method. CO 2 injection
results in carbonate water because there is generally water in reservoirs.
Carbonated water is a low-pH solution. Takahashi and Kovscek’s (2009)
experiments showed that the oil recovery factors of spontaneous countercur-
rent imbibition from carbonated water and HCl (low-pH) are similar
(Fig. 8.23). The oil recovery factors from neutral pH brine and a high-pH

0.5
Brine
0.45 Carbonated water, No.1
Carbonated water, No.2
0.4 HCI brine (pH3), No.1
HCI brine (pH3), No.2
0.35 NaOH brine (pH12)
OlP recovered 0.25
0.3

0.2
0.15
0.1
0.05
0
10 1 10 2 10 3 10 4
Time, min
Figure 8.23 Oil recovery of spontaneous countercurrent imbibition of different pH
brines (Takahashi and Kovscek, 2009).