A New Organic Gel System for Water Control: a Computed Tomography Study

Abstract

Summary Because of their thermal stability, organically cross-linked gels have been used in conformance treatments for high-temperature applications. Most of these gels consist of a polyacrylamide-based polymer and an organic cross-linker. Polyethyleneimine (PEI) has been used as an organic cross-linker for polyacrylamide-based copolymers. Allison and Purkaple (1988) reported that PEI can form aqueous gels with simple polyacrylamide (PAM) at room temperature. In a previous study (Al-Muntasheri et al. 2008), we have shown that PEI can form ringing gels with polyacrylamide homopolymers at temperatures up to 130°C (266°F). In addition, the gelation kinetics of this system was reported up to 140°C (285°F). However, the placement of this system in porous media was not examined. In this study, the displacement of this gel system was visualized with computed tomography (CT) in sandstone cores. A permeability reduction of more than 94% was realized at 23°C for cores shut in at 50°C and 45°C. In addition to CT visualization, this study reports on the bulk testing of this system over a wide range of concentrations of PAM and PEI. Visual observation revealed the formation of stable gels for 3 weeks at 100°C (212°F). These gels were rigid and nonflowing at PAM concentrations of 5, 7, and 9 wt% cross-linked with PEI at concentrations from 0.5 to 3 wt%.