NanoSurfactant: A Novel Nanoparticle-Based EOR Approach

Abstract

This paper describes a nanoparticle-based approach for stabilizing the low-cost petroleum sulfonate surfactants in high salinity and temperature water to enable their utility in EOR applications in typical carbonate reservoirs. The paper presents and discusses experimental results on the phase behavior of three of such NanoSurfactant formulations and their interfacial tensions (IFT) with crude oil, in order to evaluate their ability to mobilize oil during EOR operations. The three NanoSurfactant formulations were prepared through a one-step nano-emulsification process involving high salinity water, 5 wt% petroleum sulfonate solution and a low-dose of three different 4 wt% co-surfactant solutions. The resulting formulations had a 0.2 wt% of total active ingredients. One of the three formulations was persistently stable, colloidally and chemically, in high salinity water (~ 56,000 ppm) at high temperature (100 °C) for more than six months, while the other two showed signs of instability after about four months. Interfacial tensions between crude oil and NanoSurfactant solutions, measured using a spinning drop interfacial tensiometer at 90 °C, was in the 10−2 to 10−3 mN/m range and substantially lower than that with high salinity water alone or solutions of corresponding co-surfactants of similar concentrations. Phase behavior, investigated by monitoring the clarity and UV absorbance changes in a system of crude oil atop of the NanoSurfactant formulation at 100 °C without mechanical mixing, showed enhanced formation of homogeneous oil-in-water emulsions at 100 °C without the aid of any mixing. Our results demonstrate the ability of NanoSurfactants to mobilize oil under typical carbonate reservoir conditions. Their colloidal nature gives them advantages over conventional micellar surfactants by allowing them to migrate deeper in the reservoir due to size exclusion and chromatographic effects. The simple method utilized in making NanoSurfactants opens the door for better utilization of numerous low-cost, yet salinity- and temperature-intolerant chemicals in typical carbonate oil reservoir applications.

Molecular Assembly of Surfactant Mixtures in Oil-Swollen Micelles: Implications for High Salinity Colloidal Stability

“…We first investigated the colloidal stability of Pure Sulf and Sulf+Coca formulations in deionized water and high salinity water (see the Experimental Section in Materials and Methods for the notations of the formulations). As has been identified, Pure Sulf solutions were unstable in high salinity water and precipitated immediately after preparation. − Figure shows the DLS measurements of Pure Sulf oil-swollen micelles in deionized water, Sulf+Coca oil-swollen micelles in deionized water, and Sulf+Coca oil-swollen micelles in high salinity water. As shown, Pure Sulf solution has the highest polydispersity with their measured hydrodynamic diameters ranged from 10 to 400 nm.…”

“…Two surfactant formulations were prepared: (i) “Pure Sulf” oil-swollen micelles with 0.1 wt % chemicals (95 wt % Sulf and 5 wt % Deca within the chemicals) and (ii) “Sulf+Coca” oil-swollen micelles with 0.2 wt % chemicals (43.2 wt % Sulf, 54.5 wt % Coca, and 2.3 wt % Deca within the chemicals). The particular compositions were chosen based on prior studies optimized for enhanced oil recovery operations. − Both formulations were prepared in deionized water or high salinity water for consecutive characterization experiments. Note for the formulations in high salinity water surfactants were first mixed in deionized water at higher concentration and then the high salinity water was added to reach the desired concentrations.…”

“…Alkylbenzene sulfonates are one of the most important synthetic surfactants considering their wide applicability, cost-effectiveness, and overall consumption levels, which accounts for roughly 75% of synthetic detergents and 25% of the total surfactant consumption in the major industrialized countries . Nevertheless, pure alkylbenzene sulfonates have low salt tolerance and may precipitate immediately in high salinity water, which limited their applications in many scenarios such as enhanced oil recovery in high salinity oil reservoirs. , Recently, new experiment results have suggested that adding zwitterionic cocamidopropyl hydroxysultaine cosurfactants and mineral oils (decane) may dramatically increase the high salinity tolerance of the alkylbenzene sulfonates. − In this work, we try to provide mechanistic understanding for the enhanced high salinity colloidal stability of these surfactant mixtures using dynamic light scattering (DLS) and nuclear magnetic resonance (NMR) experiments, and molecular dynamics (MD) simulations. We believe the molecular insights put forward in this study not only inform better designs of the high salt tolerance surfactant formulations but also further our understanding for the rich molecular assembly characteristics of surfactant mixtures in complex fluids.…”

Toward Reservoir-on-a-Chip: Rapid Performance Evaluation of Enhanced Oil Recovery Surfactants for Carbonate Reservoirs Using a Calcite-Coated Micromodel

“…Solutions of 0.2 wt% EOR surfactant, labeled as Sample A and Sample B, were prepared. Sample A was a mixture of alkylbenzene sulfonate and cocamidopropyl hydroxysultaine as described previously 44,45 . Sample B is a commercially available surfactant, cocamidopropyl hydroxysultaine (Petrostep -SB, 43 wt% active, Stepan Company, Northfield, IL) and was prepared by diluting the stock solution with seawater to achieve 0.2 wt%.…”

Laboratory Testing of Novel Polyfraction Nanoemulsion for EOR Processes in Carbonate Formations

“…The entry of engineering into the nanoscale has opened up many new areas previously inaccessible without the use of nanotechnology, as well as the possibility of modifying existing technological solutions (e.g., EOR processes). Examples of research projects or nanotechnology-based solutions have been cited repeatedly [8,14,16,[20][21][22][23][24][25][26]. These studies have shown that during EOR processes, rock wettability is particularly important in carbonate rocks.…”