Gel composition and brine concentration effect on hydrogel dehydration subjected to uniaxial compression

Abstract

Gel treatment is a process that injects the gel into a reservoir to control the conformance and improve the sweep efficiency of injection fluids. At a certain pressure gradient, the gel dehydrates in a reservoir due to mechanical forces. This work evaluates the effects of the gel composition and brine concentration on gel dehydration under uniaxial compression. A sodium acrylate-co-acrylamide based gel cross-linked with N, N′-Methylenebisacrylamide (MBAA) was used for the study. The compression test is performed with a rheometer with a plate-plate geometry. The gel dehydration under pressure was measured to see how gel dehydration would be impacted by the brine concentration or the change in gel compositions including monomer and crosslinker concentration. Then, the elastic modulus (G′) and the loss modulus (G″) of the gels before and after the compression were measured. This process aimed to assess the variations of the gel mechanical properties caused by compression-induced dehydration. The result shows the gel composition has a great impact on the gel dehydration under uni-axial compression. The amount of gel dehydration increases when gel swelling degree increases for all experimental factors. The gel after compression has a lower G′ and a higher G″ compared with the gel before compression, indicating damage on gel networks. This work is of significance on optimizing gel treatments for conformance control.