Page 72 - Formation Damage during Improved Oil Recovery Fundamentals and Applications

54 David A. Wood and Bin Yuan

(salinity B1000 ppm), the injection water coming from the Madison
limestone and Fox Hills sandstone. Three Minnelusa oil fields (Moran,
North Semlek, and West Semlek) provided sufficient variation in forma-
tion and injection water salinities to compare the LSWF outcomes in
terms of salinity of the formation and injection water and the reservoir
characteristics. The analysis of production performance of those fields
(Fig. 2.16) indicated that oil recovery with LSWF flooding was greater
than for other fields in the same reservoir using higher-salinity injection
water. Also, field recovery trends for the fields matched the predictions of
core experiments and single-well tests.
Vledder et al. (2010) reported the results of a 10-year field-wide
LSWF secondary recovery project for the Omar Field (Syria), which
were supported by experiments on sandstone cores from the reservoir.
The project resulted in 10 15% of incremental oil recovery. A change in
wettability from an oil-wet system to a water-wet system over the field
production life, results in a step change in water-cut consistent with the
change in wettability.

Figure 2.16 Relationship between oil recovery and salinity ratio for Minnelusa sand-
stone LSWF in three oil fields in the Powder River Basin, Wyoming (USA). Modified
after Robertson (2007).