Development of associative polymer technology for acid diversion in sandstone and carbonate lithology

This article describes the use of associative polymer technology (APT) to achieve fluid diversion during an acid stimulation treatment. APT involves the use of a very-low-viscosity aqueous-polymer solution. It reacts immediately with the formation surface to significantly reduce the ability of subsequent aqueous fluids to flow into high-permeability portions of the rock. The first stage containing the APT predominately will enter the most permeable area, diverting the following acid stage(s) to less-permeable sections of the rock. APT has little or no effect on the flow of subsequent hydrocarbon production. Furthermore, in rock containing significant proportions of sandstone-type lithology, the water permeability of the treated zone is decreased permanently, resulting in post-treatment reduced water production from the treated zone. A general description of associating polymers and their properties, as well as a detailed description of the laboratory development of the current system, are both discussed. Laboratory data will show the effectiveness of APT in reducing the ability of aqueous fluids to flow through porous media. Parallel flow studies using water-saturated and oil-saturated cores are presented that show the ability of APT to divert acid in both sandstone and carbonate cores. These tests also show the ability of APT to decrease water permeability in the water-saturated core while the diverted acid increases the oil permeability of the oil-saturated core.