Rheology and Transport of Improved EOR Polymers under Harsh Reservoir Conditions

Abstract

New polymers that are stable in harsh environments (high salinity/hardness and high temperature) are in high demand because of the need for chemical EOR in oil reservoirs with these conditions. Commonly used partially hydrolyzed polyacrylamides (HPAM) have been successfully used in the field for decades, but they hydrolyze at high temperature and eventually precipitate in the presence of high concentrations of divalent cations. This paper mainly focuses on rheology and transport behavior of scleroglucan (non-ionic polysaccharide) and N-vinylpyrrolidone (NVP)-polyacrylamide (AM) co-polymer. The rigid, rod-like, triple helical structure of scleroglucan imparts exceptional stability and its non-ionic functionality makes it insensitivity to salinity and hardness. By a different mechanism, NVP in modified HPAM protects the polymer's amide group against thermal hydrolysis, i.e., by sterically hindering the amide group. This allows maintaining high viscosity even in high salinity brines at high temperature. Both scleroglucan and NVP co- or ter-polymers show good filterability and transport properties in sandstone and carbonate cores at high temperature and in brine with high salinity and hardness. Therefore, both polymers are promising candidates for polymer flooding, surfactant-polymer flooding and alkali-surfactant-polymer flooding in hard brine at high temperature, but must be evaluated under specific reservoir conditions.

Some Key Features to Consider When Studying Acrylamide-Based Polymers for Chemical Enhanced Oil Recovery

“…Thanks to the new developments in chemistry, polymer flooding can be implemented in higher salinity, higher temperature and lower permeability reservoirs. At the laboratory scale, the boundaries that can be achieved with new polymers (Vermolen et al, 2011;Kulawardana et al, 2012) are given in Table 1. The success depends also on the viscosity of the oil in place, as described by the permeability factor in the mobility ratio equation.…”

Rheology of Laponite-scleroglucan hydrogels

“…In the field of enhanced oil recovery (EOR) scleroglucan is assessed as environmentally friendly viscosifying agent in virtue of its no toxicity and biodegradability. Indeed, it is quite suitable for formulating water based drilling muds to be employed in harsh environments owing to its good stability towards high salinities, temperatures and alkaline conditions, moderate interactions with surfactants and its robust shear tolerance (Baba Hamed & Belhadri, 2009;Gallino, Guarneri, Poli, & Xiao, 1996;Kulawardana et al, 2012;Sveistrup, van Mastrigt, Norrman, Picchioni, & Paso, 2016).…”

Artificial Neural Network Model to Estimate the Viscosity of Polymer Solutions for Enhanced Oil Recovery

“…After aging at 90˝C for 16 days, the viscosity of AMPS/AM was almost unchanged [2]. temperatures and high cation concentrations) attract attention because of the need for polymer flooding in oil reservoirs with these conditions [32][33][34][35][36][37]. 2-Acrylamido-2-methylpropane-sulfonate copolymer (AMPS) can be effectively applied to high-temperature or high-cation concentration conditions.…”