| Summary: | Polymer gels have been designed and successfully applied to improve sweep efficiency and to reduce excessive water production by minimizing reservoir heterogeneity. Based on their compositions and application conditions, polyacrylamide polymer gels can be classified into three types: in-situ monomer-based gel, in-situ polymer-based gels, and preformed particle gels. Initially, in-situ monomer gels which are mainly composed of acrylamide were developed for water shutoff. Conventional in-situ polymer gels include metal-cross linked polyacrylamide gels and organic-cross linked polyacrylamide gels. Preformed gels include preformed particle gels, pH sensitive microgels, and micro- and nano-gels. A few directions are suggested for future research on novel gels, such as gels used for in-depth fluid diversion and gels for severe reservoir environments. Key words: polyacrylamide (PAM), monomer-based gel, polymer gels, preformed particle gels, conformance control, in-depth fluid diversion, enhanced oil recovery
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