Laboratory Study of a New EOR-Grade Scleroglucan

摘要

Scleroglucan is a non-ionic exopolysaccharide produced by a specific fungi, called Sclerotium glucanicum. Due to its high viscosifying power and its good stability towards temperature and salinity, scleroglucan has been at the heart of several studies aiming at evaluating its potential for Enhanced Oil Recovery (EOR). As a biopolymer, scleroglucan is environmentally-friendly with no limitation of use in sensitive area such as offshore North Sea. Despite these promising features, the main pitfall of scleroglucan for EOR purposes has been its poor filterability, which is mainly explained by fermentation broth residues and polymer aggregates. This issue led researchers to use tedious filtration methods prior to experiments, which are not applicable in the field. To overcome this limitation, a new process was developed to obtain an EOR-grade scleroglucan which has been submitted to laboratory tests. The first part of this paper presents bulk experiments with this new EOR-grade scleroglucan. Filtration tests enabled to assess the efficiency of the dissolution process and the homogeneity of the solution. The dissolution method was optimized to obtain a proper solubilization of the polymer. Rheological behavior was also investigated, showing the high viscosifying power of the product, much higher than conventional EOR products like hydrolyzed polyacrylamide. In a second part, coreflood experiments were performed in high-permeability (Kw(Sw=1)=1.5 D) Bentheimer sandstone and medium-permeability (Kw(Sw=1-So,r)=120 mD) Estaillade limestone. The main highlight is that no particular pre-filtration process was needed prior to injection in the core. Indeed, very good injectivities were obtained in both rock types. Dynamic adsorption was low in Bentheimer sandstone, and in Estaillade limestone in the presence of a residual oil saturation. This study qualifies this new EOR-grade scleroglucan for EOR applications. With a good injectivity, low adsorption levels, high resistance to temperature and salinity, and low environmental footprint, this polymer could advantageously replace hydrolyzed polyacrylamide, and its derivatives, in hightemperature and high- salinity reservoirs, and in sensitive offshore areas.