Page 294 - Fundamentals of Enhanced Oil and Gas Recovery

282 Mohammad Ali Ahmadi

The test was conducted in 2014. There were one injection well and several offset
wells. In the first 3 months, the well injection rate was 1700 STB/day and later
reduced to 1000 STB/day because of breakthrough at a close offset well [40]. The
close offset well (about 880 ft away) had a huge increase in water production, but the
oil rate did not increase during this time. The water broke after 1 week.
One water huff-n-puff pilot test was conducted in the North Dakota part of the
Bakken Formation in 2012. The injection time was just over 1 month, the soaking
time was 2 weeks, and the production time was 3 4 months. The injection rate was
1200 bbl/day. No water injectivity problem was observed, but little to no oil rate was
increased [40].
According to the pilot test of produced water re-injection with huff-n-puff setting
that has been done in the Parshall field, there is no significant improvement of the oil
recovery factor after employing such a method. In this scenario that is performed on
spring of 2012, the duration of water injection was about 30 days and 10 days as a
soaking period; after that time the production was open to flow [1].
Table 9.2 presents several field tests that have been performed in shale oil reservoirs
located in China. This table provides general information regarding the type of injec-
tion mode as well as rock and fluid characterization (some of them not reported).
Also, the performance of each field test is reported in Table 9.2 [1].
Huff-n-puff water injection was also performed in the Chang 6 reservoir,
Yanchang oil field near Qieli Village, Ordos Basin, China (huff-n-puff 4 in
Table 9.2) [1].
Huff-n-puff water injection was also successfully tested in Toutai reservoir,
Daqing. The permeability was 1.25 mD, and the huff-n-puff cycle was half to one
year [1]. Huff-n-puff water injection was tested in 2007 in Well Niu 15-5 in
Niuquanhu reservoir, Tuha Field. The permeability in this area was 0.42 7.84 mD.
The soaking time was 108 days. Two cycles were performed with incremental oil of
1816 tons [1]. Huff-n-puff water injection was performed in Duha Field, Xingjiang,
China (huff-n-puff 5 in Table 9.2). Water was injected in Well Ma-55 from July 18,
3
2014 to July 24, 2014. The injection rate was 285 m /day. The total injected water
3
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 injection, the oil rate was 5 tons/day
and the water rate was kept constant until the reporting date (August 2015) [1].

9.4 ENVIRONMENTAL ASPECTS OF SHALE OIL
AND GAS PRODUCTION

Owing to the growing concern regarding climate change and energy demand,
using natural gas as a clean-burning and affordable source of energy has been