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When properly applied in appropriate reservoir conditions, polymer gel treatments are effective for reducing high water production and improving oil recovery. The gels move into highly permeable, water-saturated zones and severely reduce permeability to water so that oil can be produced from tighter rock. In May 1994, a waterflood was started in the Breed Creek Unit in Northeast Montana. Oil response, which began after six months of injection, was combined with connate water so that the WOR averaged about 0.4. Eight months later, water began to increase rapidly, indicating injection water breakthrough to the producing wells.
In May 1996, TIORCO placed an injection well treatment at the Breed Creek Unit, using a medium molecular weight, water-soluble, partially hydrolyzed polyacrylamide and chromium acetate crosslinker, based on MARCIT technology.
Six months after treatment, a response was seen at the offset producing wells, and was sustained for the next 26 months. Considering WOR trends through September 1998, incremental oil recovery was 80,000 bbl., amounting to 1% of OOIP field-wide, or 2% - 4% of OOIP in the southern area of the field affected by the gel.
Timely placement of the gel resulted in a stronger, more defined treatment response. With less water-saturated rock between the injector and offset wells, more incremental oil was recovered when gel was placed earlier in the life of the waterflood. Generally, successful injection well treatments occur when:
- Channeling from the injector to one or more producing wells exists.
- Producing WORs are high or increasing, with production still economic and significant quantities of recoverable oil in the pattern area.
- The injection well has the capacity to accept a gel treatment, build pressure and maintain a desired injection rate following the treatment.
- The gel volume is large relative to the estimated volume of the channel, or to the permeability of the rock conducting the water.
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