Continuous, long-term injection of an environmentally sound colloidal dispersion gel (CDG) provides a solution to in-depth, away from the well bore, channeling and crossflow problems inherent with waterflooding.  In the past two decades, TIORCO has used colloidal dispersion gels in over 50 reservoirs (primarily Minnelusa and Tyler formations) to improve volumetric sweep and oil recovery. 

In 29 successful projects (documented in a 1997 article in the Oil & Gas Journal), the gels increased oil production at lower water/oil ratios.  Incremental oil recoveries ranged from 0.6 to 26.2% OOIP.  At that time, the successful projects had recovered an estimated 12.3 bbl of incremental cumulative oil at an average chemical cost of $1.09/incremental oil bbl.  Estimated ultimate oil recoveries in successful treatments exceeded 40% of original oil-in-place (OOIP), in highly heterogeneous matrix reservoirs with Dykstra-Parsons permeability variations of about 0.8.  Chemical costs ranged from $0.47 to $4.08/bbl of incremental oil recovered.

At the North Rainbow Ranch Unit in Campbell County, Wyoming, primary production is generally less than 20% of OOIP and sweep efficiencies can be poor due to high permeability variation. The unit produces from the Minnelusa “A” sand, an Aeolian sandstone which is unconformably overlaid by the capping and sealing Opeche shale. Several sand fancies are present and separated by thin dolomites.

Two different types of polymer augmented systems have been used successfully on injection wells in the unit. The first was a long-term, in-depth colloidal dispersion gel (CDG). This process used cationic polyacrylamide and anionic polyacrylamide crosslinked with aluminum citrate.  The second system was a short-term bulk gel consisting of an anionic polyacrylamide and chromium acetate combination.

The CDG systems provided in-depth resistance to flow while the bulk gel systems were placed in non-fractured formations to provide in-depth drive fluid diversion. The total ultimate recovery with the polymer augmented processes was estimated at 61% of OOIP.

References:

“Gels Correct In-depth Reservoir Permeability Variation”.  By Julie E. Smith and James C. Mack, TIORCO Inc.  Oil & Gas Journal, January 6, 1997.

SPE/DOE 27773 – “In Depth Drive Fluid Diversion Using Evolution of Colloidal Dispersion Gels and New Bulk Gels: An Operational Case History of North Rainbow Ranch Unit,” by R.C. Fielding, Jr. TIORCO, Inc. and D.H. Gibbons and F.P. Legrand, Apache Corp.

Oil Recovery In Wyoming | Reducing Water Production in Gas Wells | Water Shutoff in Prudhoe Bay | Permian Basin Projects |
IOR In Montana’s Tyler Sandstone | CDG Projects