Page 188 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Water injection 171

Huff-n-puff water injection was also successfully tested in Toutai reser-
voir, Daqing. The permeability was 1.25 mD, and the huff-n-puff cycle was
half to 1 year (Tian et al., 2003). Huff-n-puff water injection was tested in
2007 in Well Niu 15e5 in Niuquanhu reservoir, Tuha Field. The perme-
ability in this area was 0.42e7.84 mD. The soaking time was 108 days. Two
cycles were performed with incremental oil of 1816 tons (Yang et al., 2006;
Tang and Li, 2010).
Huff-n-puff water injection was performed in Duha Field, Xingjiang,
China (Huff-n-puff 5 in Table 7.4). Duha Field was an igneous reservoir.
The porosity was 8.4%e19.1%, and the permeability was 0.1e1 mD. The
initial reservoir pressure was 20.4 MPa (2958 psi) and the reservoir temper-

ature was 60.9e70.7 C. Water was injected in Well Ma-55 from July 18 to
July 24, 2014. The well was fractured. The injection pressure was
3
30e38 MPa (4350e5510 psi). The injection rate was 285 m /day. The total
3
injected water volume was 2000 m . The oil rate before water injection was
0.9 tons/day and the water cut was 16%. After the huff-n-puff water injec-
tion, the oil rate was 5 tons/day and the water rate was kept constant until
the reporting date (August 2015). The incremental oil was 155 tons
(Li, 2015).
The above field cases show that huff-n-puff water injection generally
worked. The injection, soaking, and production times were quite different
from case to case. Huff-n-puff water injection was even practiced in con-
ventional reservoirs, for example, in the Machang field where the perme-
ability is 90 mD (Li et al., 2001). Some experimental work in high
permeability cores (110e180 mD) was also carried out (Huang Xiang,
2004).