Page 67 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Huff-n-puff gas injection in oil reservoirs 55

120

100
Penetration depth, ft 80

60

40

20
0
0 20 40 60 80 100 120
Huff time, days
Figure 2.46 CO 2 penetration depth at different injection time in the first huff-n-puff
cycle.

data are discussed. A performance summary is provided at the end of this
section.

2.15.1 CO 2 huff-n-puff in Bakken formation, Elm Coulee field
Early in 2008 before the shale boom, a CO 2 huff-n-puff injection pilot was
conducted in the Elm Coulee field in the Bakken formation in the North
Dakota part (Hoffman and Evans, 2016). No injectivity problem was
observed, with injection rate being 1 MMSCF/day at the injection pressure
of 2000e3000 psi. Having 30 days of injection, the pilot showed little to no
rate increase.

2.15.2 CO 2 huff-n-puff in Burning Tree-State No. 36-2H well
in the Montana part of Bakken formation

Continental Resources, Enerplus, and XTO Energy jointly carried out CO 2
huff-n-puff injection in the Burning Tree-State No. 36-2H well in Rich-
land County in the Montana part of the Bakken formation in early 2009.
The horizontal well was completed in the Middle Bakken and was stimu-
lated using single-stage hydraulic fracturing. During 45 days of injection
from January to February 2009, approximately 45 million cubic feet
(2570 tons) of CO 2 were injected. The injection rate was 1.5e2
MMSCF/d at 2000e3000 psi. After that the well was soaked for 64 days
before production (Hoffman and Evans, 2016).