Heavy Oil and High-Temperature Polymer EOR Applications

Abstract

Polymer flooding represents the most common chemical enhanced oil recovery (CEOR) method used at commercial scale. In this process, the polymeric solutions (generally hydrolyzed polyacrylamide - HPAM) are injected to improve the oil/water mobility ratio (M). However, due to mechanical, chemical, bio, and thermal degradation, polymer viscosity losses can occur, causing a negative impact on oil sweep efficiency. In this case, biopolymers seem to be promising candidates in EOR applications with special structural characteristics, which result in excellent stability in harsh environments with high temperatures, ionic forces, and shear stresses. This paper presents the laboratory evaluation of Scleroglucan (SG) and a commercial sulfonated polyacrylamide (ATBS) in synthetic brine, representative of a Colombian heavy-oil field. The effects of ionic strength, pH, temperature, and shear degradation effects on polymer viscosity were also evaluated. For SG, the results reflect its tolerance to high salinities (0-5%wt), ionic strengths (Na+, K+, Ca2+, and Mg2+), shear rates (0-300,000 s-1), temperatures (30, 50, 80 and 100 °C), and pH variations (3-10). The biopolymer was capable of preserving its viscous properties and stability after of the effect of these variables. Finally, the target viscosity (set as 17 cp) was achieved with a lower concentration (2.7 times) than the ATBS polymer tested.

Mixture design of experiments for the behavior analysis of sulfonated polyacrylamide solutions (ATBS) with salinity, hardness, and concentration changes.

“…Water hardness is defined as the content of divalent metal cations. Dissolved calcium (Ca +2 ) and magnesium (Mg +2 ) are two divalent cations found at appreciable levels in most waters [17]. In this research, hardness was considered as CaCl2 content in the brine.…”

“…Castro et al [17] evaluate the effects of divalent cations (Ca 2+ and Mg 2+ ) on Scleroglucan (SG) and (ATBS) polymer viscosities. The Scleroglucan viscosity is stable, with the calcium concentration increasing in the solution; conversely, the sulfonated polyacrylamide solution showed decrease in viscosity, increasing calcium concentration.…”

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

“…Biopolymers are promising alternatives to synthetic polymers because they have great resistance against mechanical degradation, high temperatures, high salt content, wide pH ranges, and are ecofriendly [17], [18]. Additionally, they are extracted from renewable materials like plants or microorganisms.…”

“…Xanthan Gum, Schizophyllan, Scleroglucan, and Guar Gum were chosen as the test polymers. Previous works have studied Xanthan Gum [16], [25], [35], [42], [43], Guar Gum [43], Scleroglucan/Schizophyllan [16], [18], [42]- [45], focusing on EOR or pore medium flow behavior. This paper studied the bulk rheology of those biopolymers under different conditions.…”

“…Regarding their properties for EOR, Scleroglucan/Schizophyllan have a much less marked interaction with carbonates [68]- [70] and suffer less influence by ionic strength or temperature than Xanthan Gum [15], [58], [71]. They are resistant to pH values from 2 to 12 [18], [48], but the triple rods can be melted at higher pH values [48], [53]. An extensive comparative study of several polymers, including Xanthan Gum, Scleroglucan, and Guar Gum, found that Scleroglucan has the most potential for North Sea use [43].…”