A novel polymer gel with high-temperature and high-salinity resistance for conformance control in carbonate reservoirs

Plugging agents have been widely used to enhance oil recovery in fractured-vuggy carbonate reservoirs. However, the harsh conditions of fractured-vuggy carbonate reservoirs yield a significant challenge in maintaining a long-term stabilization of plugging agents. In this work, we developed an anti-high-temperature and high-salinity polymer gel (APG) with excellent resistance to high temperature (140 °C) and ultra-high salinity (240000 mg/L). The rheology and microstructure of APG were characterized before and after gelation. Core plugging tests on fractured cubic cores were conducted to quantify the plugging performance of the gel system. Experimental results showed that the Sclerglucan and Cobalt (II) Chloride Hexahydrate filled the three-dimensional (3-D) network with various morphologies, providing extra protection to the cross-linking points of the 3D network structure of APG and thus, leading to a prolongation of the dehydration time. The dehydration rate of APG was only 5% within 30 days, and the strength of APG could be maintained at a rigid or near-rigid level over 150 days. Moreover, APG exhibited satisfactory shear and scour resistance. Core plugging tests showed that APG could achieve a plugging rate of 90% and demonstrate ignorable minor damage to the substrate. Our results indicate that APG can serve as a great candidate in channel plugging in fractured-vuggy carbonate reservoirs where fractures are fully developed.