Abstract
There is increasing concern among domestic operators for reducing water production as fields mature. A new polymer gel, with several unique advantages over conventional gelling systems, has been developed which could serve as a water shut-off agent. The gel forms in place when a freshwater solution of a water-soluble polymer (hydroxypropylcellulose, HPC) and a surfactant (sodium dodecyl sulfate, SDS) mixes with brine. While conventional gels use a chemical initiator or activator, often a heavy metal like chromium, to form the gel, the new HPC/SDS gel uses the salinity of the connate brine to initiate immediate gel formation.
The low-viscosity freshwater HPC/SDS solution injects easily into core material. Upon mixing with the connate brine, a stable high-viscosity gel forms that effectively reduces brine permeability by over 95% in both linear and radial sandstone corefloods. The gel viscosity was measured at about 70,000 centipoise. Permeability reduction is maintained, both in the forward and reverse flow direction, even after several pore volumes of brine flow. In a parallel coreflood test, the gel diverted 90% of the fractional flow of brine.
