Complete fluid shutoff using crosslinked polymer gels represents an effective means of water control in reservoirs producing uneconomical volumes of water. To achieve this goal, a new organic crosslinker was developed for complete matrix shut-off in lower temperature reservoirs (80 to 140°F). The system uses a low molecular weight, crosslinked polymer that is injected directly into the target zone, reducing the permeability in the matrix.
The crosslinker represents a significant improvement over traditional organic crosslinkers like polyethyleneimine (PEI) and chromium-based metallic systems. The new product has very similar gelation time (<12hr) profiles to the chromium systems, but requires shorter times than PEI, which could have gel times to ~24hr at 80°F. Additionally, the system has a much smaller environmental footprint, easing operator's concern over the sustainability of their chemical shutoff system. Results indicate that the new crosslinker yields ringing gels at lower dosages than traditional organic crosslinkers like PEI. (Sydansk gel code J).
This product enables easy generation of ringing, rigid gels for low-temperature reservoirs within a reasonable gelation time (<12hr), making it ideal for applications including water shut-off, casing leak repairs, cement squeeze alternatives, zone abandonments, etc. It represents a cost-effective, environmentally friendly alternative to heavy-metal containing chromium systems where current available organic systems require longer shut-in times and increased concentrations to achieve similar gel strengths. A series of performance tests including laboratory core analysis was conducted to determine it's operating effectiveness. The product was successfully field tested in the Spraberry formation in the Permian basin.