Bulk rheology characterization of biopolymer solutions and discussions of their potential for enhanced oil recovery applications

Enhanced oil recovery (EOR) techniques are essential to improve oil production, and polymer flooding has become one of the promising technologies for the Brazilian Pre-Salt scenario. Biopolymers offer a range of advantages considering the Pre-Salt conditions compared to synthetic polymers, such as resistance to high salinity, high temperature, and mechanical degradation. In that sense, bulk rheology is the first step in a workflow for performance analysis.This paper presents a rheological analysis of four biopolymers (Schizophyllan, Scleroglucan, Guar Gum, and Xanthan Gum) in concentrations from 10 to 2,300 ppm, generally suitable for EOR applications, in temperature levels of 25, 40, 50, 60 and 70 Celsius degrade and two brines of 30,100 ppm and 69,100 ppm total dissolved solids, which aim to model seawater and the mixture between injected seawater and reservoir water typical in Pre-Salt conditions. The pseudoplastic behavior, the overlap concentration, and the activation energy were determined for each polymer solution. The structural differences in the polymers resulted in different rheological behaviors. Schizophyllan is the most promising, as its viscosifying power is higher than synthetic polymers comparable to Xanthan Gum. Its resistance at high temperatures is higher than that of synthetic polymers. Scleroglucan behaved similarly to Xanthan Gum, with the added advantage of being nonionic. Guar Gum had the lowest viscosities, highest overlap concentrations, and most pronounced viscosity decay among the tested polymers.To the author's knowledge, rheological studies of the biopolymers presented here, considering the viscosities and the overlap concentration and activation energy, in the Pre-salt conditions, are not available in the literature and this will benefit future works that depend on this information.