Page 503 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Other enhanced oil recovery methods 467

14.11 Microbial EOR
Microbial EOR is to inject microbial reaction products in the reser-
voir or inject microbes and nutrients in the reservoir so that microbial prod-
ucts are generated (Sheng, 2013b). These products could be acids, gases,
solvents, biosurfactants, and biopolymers. Their EOR mechanisms are
similar to those for gas injection and chemical injection. Microbial EOR

is generally applied to formations of low temperature (<98 C) and high
permeability (>50 mD) (Sheng, 2013c). However, one application in a
low-permeability reservoir is reported (Liu et al., 2010), as briefed below.
In the MEOR pilot test zone, Wangyao, in Ansai Field, China, the
porosity was 14%, the permeability was 5.22 mD, and the reservoir temper-
ature was 45 C. The water cut reached 66.1%, and the average well oil rate

was 1.48 tons/d before the test. One injector, Wang 15e5, was chosen with
3
7 producers around it. Total 1150 m of solution was injected. The solution
consisted of two slugs, the first slug being microbes and nutrients, and the
second slug being microbial reaction products. The injection was operated
from June 28 to August 21, 2009. The response time was 40 days. The in-
jection might be effective within 300 days. By the end of 2009, the cumu-
lative oil increased was 297.65 tons, and the estimated ultimate incremental
oil was 550 tons.