| abstract |
Improved sweep efficiency in oil-bearing reservoirs having high permeability streaks therein can be effected by first injecting a gel-forming solution consisting essentially of a dichromate activator in a lignosulfonate solution, modified by the presence of an alkali metal halide or an alkaline earth metal halide, such as, for example, sodium chloride or calcium chloride. This system has the advantage of high temperature tolerance and the gelforming characteristics thereof are not appreciably affected either by formation brine or CO2. Gel-forming solutions can be designed requiring from 10 to 2,000 hours to form a gel. |