Novel Environmentally Benign Hydrogel: Nano-Silica Hybrid Hydrolyzed Polyacrylamide/ Polyethyleneimine Gel System for Conformance Improvement in High Temperature High Salinity Reservoir

Abstract

Abstract In order to address the conformance problem in high temperature and high salinity/hardness reservoir, an environmentally benign in-situ gel was developed based on hydrolyzed polyacrylamide (HPAM) and polyethyleneimine (PEI). Moreover, silica nanoparticle (SNP) was embedded to improve the performance of HPAM/PEI gel. To achieve the optimum formulation of HPAM/PEI-SNP gel, a comprehensive investigation was first conducted with the respect of gelation time, gel strength, and thermal stability. In addition, the particle size of SNP was determined by Dynamic Light Scatter (DLS) and the microstructure of HPAM/PEI-SNP gel was characterized via Scanning Electron Microscopy (SEM). The optimum formulation, containing the polymer/crosslinker ratio of 10,000-2,000 using high molecular weight HPAM (10-15 million Dalton) with a low hydrolysis degree of 3-7%, was obtained. Given the compatibility of comparability of SNP and formation water, LS nano silica with an SNP concentration of 30 wt% was selected as hybrid resource. The results indicated that the gelation time of novel gel system was prolonged to 132 hours attributed to the introducing of nanomaterial. Taking advantage of nano-composite, the strength of HPAM/PEI-SNP gel maintained as Grade G for 312 h. Furthermore, the HPAM/PEI-SNP gel exhibited an excellent thermal stability at 85 °C for 660 hours without syneresis. Subsequently, SEM images confirmed the successful incorporation of SNP in the 3-dimentional network of hydrogel, supporting an effective surface modification. This work demonstrated that the novel environmentally benign HPAM/PEI-SNP gel system can be used as a potential plugging agent for the conformance improvement in high temperature high salinity reservoirs.