Natural Polymer-Based Compositions Designed for Use in Conformance Gel Systems

摘要

This article describes a crosslinking material derived from natural sources that can be used with a variety of polymers over a broad temperature range to produce gels for conformance applications. Delayed crosslinked polymer systems have been used for many years in conformance applications. For the past decade, the most widely used system has been based on chromium (+3) crosslinked polyacrylamide. Organic crosslinkers, such as phenol/formaldehyde and polyethyleneimine (PEI), have also been used with a variety of polymers. However, these systems are being scrutinized by regulatory agencies and have now been scheduled for phase-out in some countries. Because of these issues, a single, environmentally friendly crosslinker that could be used with a variety of polymers over a broad temperature range was selected for study. This article details the laboratory development of an environmentally friendly, natural polyamine crosslinker system, namely chitosan. This crosslinker can be used with a variety of polymers, such as polyacrylamide, AMPS/acrylamide (AMPS/AA), or alkylacrylate polymers. Gels ranging from stiff and "ringing" type to "lipping" have been obtained. Additionally, this article summarizes results from recent efforts targeted toward designing chito-san-based gel compositions with improved environmental rating for potential field use. These efforts included using chitosan as the base polymer in combination with a synthetic polymeric crosslinker, as well as developing gels derived completely from natural polymers.