Page 289 - Fundamentals of Enhanced Oil and Gas Recovery

Enhanced Oil Recovery (EOR) in Shale Oil Reservoirs 277

injection. In the huff-n-puff scenario he considered 60 days for injection, 10 days as a
soaking time, and 120 days for production time in each cycle; he repeated this sce-
nario for 6 cycles. According to his simulation outputs, the oil recovery factor
improved significantly in a case of continuous carbon dioxide flooding; in both huff-
n-puff and continuous CO 2 injection the oil production enhanced. One of the rea-
sons come to mind for such a result is that in her simulation model the advantage of
huff-n-puff was ignored because of using the central well as an injector; however, in a
case of huff-n-puff model the injector and producer is exactly the same. Moreover,
she did not incorporate the effect of molecular diffusion in the reservoir simulation.
Considering the points discussed above, in a case of CO 2 huff-n-puff injection
scenario various factors should be taken into account. Also, all the main parameters of
such a method should be optimized; these parameters are the number of cycles, injec-
tion time, soaking period, production time, and well configurations.

9.3.1.4 Field Test of Gas Injection
One of the field test of carbon dioxide injection in shale formation is immiscible CO 2
flooding in Bakken formation in Saskatchewan [38]. The top view of the Bakken field
located in Saskatchewan is depicted in Fig. 9.7. The pilot project covered 1280 ac and
was developed on a combination of 80 and 160-ac spacing. The length of the hori-
zontal well was 1 mi; all the horizontal wells were stimulated using hydraulic

Figure 9.7 Top view of the Saskatchewan Viewfield Bakken [38,39].