NanoSurfactant for EOR in Carbonate Reservoirs

Abstract

A new class of surfactants for enhanced oil recovery (EOR) applications has been developed in the form of petroleum sulfonate salt nanoparticle dispersions in seawater. These NanoSuractants (NS) are 10- to 60-nm particles of the seawater-insoluble petroleum sulfonate salts, one of the most abundant and inexpensive industrial surfactants, that are resiliently stable in seawater at elevated temperatures via a special class of co-surfactants. They can be easily prepared in the field by mixing with seawater at ambient temperature and injected into the reservoir with seawater without any additional infrastructure. The colloidal nature and extremely small size of the NanoSurfactans particles allow them to migrate and deliver petroleum sulfonates to remaining and residual oil deep in the reservoir without the need of large quantities in order to compensate for losses by adsorption onto the rock surfaces and diffusion into water-filled small pores. This paper reports on the results of few tests conducted to evaluate the performance of NanoSurfactant formulations under reservoir conditions. Results showed consistent colloidal and chemical stability of the NanoSurfactant formulations for over six months at 100°C. They reduced the seawater-crude oil interfacial tension (IFT) by two to three orders of magnitude or formed oil-in-water emulsions at 100 °C without any mechanical mixing. Transmission electron miscroscopy (TEM) images revealed mostly round particle in the submicron range (10- to 60-nm). Finally, core-flood test at reservoir conditions using bottom-hole live oil samples indicated an additional oil recovery of about 7% of OOIP beyond several pore-volumes flooding with seawater by injecting 0.4 pore-volume of the NanoSurfactant at 0.2 wt% concentration.

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.…”

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

“…Regardless of the adopted classification and division of secondary methods to support oil production, each case should be considered individually. Many examples can be found in the literature from laboratory tests through to computer simulations and test pilots, ending with the analysis of completed projects in specific fields [13][14][15][16][17][18][19]. The full cycle of preparation and implementation of an EOR project, from laboratory research to its implementation in an oil field and confirming its effectiveness, is typically complex, long-lasting and, thus, expensive.…”

“…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.…”