Evaluation of novel organically crosslinked polymer gel for water shut-off purposes

Abstract

One common issue faced in the lifespan of oil or gas wells is water-cut, which leads to economic challenges due to water handling and operational costs, as well as reduced oil productivity. In this study, an organically cross-linked system consisting of HQ/HMTA is used for experimental work, as a substitute for the phenol/formaldehyde system with lower toxicity levels. The present study focuses on bulk gelation studies using the bottle testing method with polymer gelant prepared from PAM and HQ/HMTA. Determining the gelation time at different temperatures is important to understand the depth up to which the gel can be placed in the formation at reservoir temperature. The study revealed that gelation time can be controlled by adjusting gel composition and environmental conditions, ranging from a few hours to several days; higher polymer and crosslinker concentration in the gelant solution results in decreased gelation time, but excessive cross-linking leads to syneresis beyond a certain range; Gelation occurs more rapidly in the presence of low concentration salt compared to distilled water, but when brine concentration is increased, the gelation time increases due to the screening effect and reduced availability of cross-linking agents; Divalent ions tend to promote faster gelation compared to monovalent ions, likely due to their higher charge density. Overall, presented gel system is highly efficient in shutting off water in reservoirs. Keywords: water shut-off; organically crosslinked gel; gelation time; resistance factor; residual resistance factor; divalent ions.