Jitendra Sangwai

Pickering emulsion offers potential applications in several fields including oil and gas industry due to their enhanced stability. Oil-in-water (o/w) emulsions are usually stabilized by surfactant or nanoparticle or by both but show poor thermal stability which limits their use for high-temperature applications. In this work, a novel formulation of o/w emulsion stabilized using nanoparticle-surfactant-polymer system is investigated for the formulation of thermally stable Pickering emulsion. The conventional oilfield polymer polyacrylamide (PAM), surfactant, sodium dodecylsulfate (SDS), and nanoparticles such as, SiO2, clay, and CuO in varying concentration are used. It is observed that the nanoparticle in the presence of surfactant and polymer synergistically interacted at the oil-water interface. The effect of temperature, pH, and salinity on the interfacial tension is investigated to understand the thermal stability. The emulsion system with partially hydrophobic clay nanoparticles in the presence of PAM and SDS shows higher thermal stability as compared to fully hydrophilic SiO2 nanoparticles. In the presence of salt, NaCl (1.0wt%), the thermal stability of clay and SiO2 stabilized emulsions is observed to be further promoted at higher temperatures. Scanning electron microscopy (SEM) images confirm the existence of a structured and rigid layer of nanoparticle at the oil-water interface.

The reduction in interfacial tension (IFT) of paraffin crude oil is of key importance, particularly for oilfield applications such as enhanced oil recovery (EOR). Nanoparticle laden suspension such as nanofluid is gaining widespread interest and their use to achieve moderate IFT reduction in paraffin crude oil. In this work, stable nanofluids of an oilfield polymer (polyacrylamide, PAM) with and without surfactant (sodium dodecyl sulfate, SDS) have been formulated and examined for IFT reduction of paraffin oils such as n-decane, n-hexane, n-pentane, and n-heptane. Nanofluids were also investigated for various studies such as dispersion stability, viscosity, rate of sedimentation (ROS), and DLS based measurements (size and zeta-potential). Other studies involving investigations on surface tension (SFT), IFT reduction, effect of SDS and varying SiO2concentration on IFT reduction, and their efficacy for IFT reduction under high temperature environment have also been reported. The performance of nanofluids for IFT reduction has been compared with IFT results of conventional polymer (P) and surfactant-polymer (SP) methods, which are typically used for chemical-EOR practices. As compared to P and SP methods, IFT value of nanoparticle-polymer (NP) and nanoparticle-surfactant-polymer (NSP) fluids were found to be significantly lower suitable for enhanced oil recovery. In addition, NSP nanofluids provided superior reduction in IFT values mainly due to the presence of SDS. Thus, we conclude that SiO2nanofluid, as compared to P/SP EOR methods, can be a potential alternative to reduce the IFT of paraffin crude oil.

Nanotechnology offers potential benefits for improving the next-generation enhanced oil recovery (EOR) process from Brownfield reservoirs. In our recent study (Sharma et al., 2014a), we formulated novel Pickering emulsion stabilized using conventional oilfield polymer polyacrylamide (PAM) and nanoparticles (SiO2 and clay) in the presence of surfactant, which is thermally stable at elevated temperature and suitable for EOR application. In this study, the use of these Pickering emulsion is investigated for enhanced oil recovery. Two types of flood systems, viz., surfactant-polymer (SP) and o/w Pickering emulsion flood, are prepared and used for 12 core flooding experiments to study the additional oil recovery at reservoir pressure of 13.6MPa and temperature ranges from 313 to 363K. These reservoir conditions of pressure and temperature are representative to one of the mature reservoirs in India. The incorporation of nanoparticle was observed to provide relatively lower and stable interfacial tension (IFT) for the Pickering emulsion. The viscosity of SP system was observed to decrease with temperature (313-363K), while that of Pickering emulsion was observed to remain stable and thereby indicating a possible stable mobility ratio downhole during EOR. Nanoparticle stabilized Pickering emulsion observed to give enhanced oil recovery by about 80% more at elevated temperatures as compared to conventional SP flood, showing promising advantages of employment of nanoparticles in oilfield industry. The investigation on the permeability reduction indicated a relatively larger retention of SiO2 nanoparticle than its counterpart clay, which is attributed to its larger size in the system.

Efficient flooding agents are required to produce additional oil from mature reservoir. In this work, oil-in-water Pickering emulsion systems stabilized using nanoparticles, surfactant, and polymer have been developed and tested for enhanced oil recovery with and without a conventional polymer flood. Stability of nanoparticles in the dispersion of surfactant-polymer solution was tested using zeta-potential before use. Several flooding experiments have been conducted using Berea core samples at 13.6 MPa and temperatures of 313 and 353 K. It has been observed that a combination of 0.5 PV polymer flood with 0.5 PV Pickering emulsion was efficient and have resulted in 1-6% additional oil recovery as compared to 0.5 PV Pickering emulsion flooding alone. The injection of polymer flood have shown to enhance the pressure drop in the core sample after emulsion flooding and considered as an important factor for an additional recovery of oil. The effect of temperature on the viscosity of flooding agents in relation to pressure drop and oil recovery have also been investigated. Viscosity and pressure drop of emulsion flood systems have shown to marginally decrease with increase in temperature. Studies on nanoparticle retention using SEM have shown that nanoparticles were retained in the core sample during emulsion flooding which may be detrimental for permeability of core sample. It is observed that Pickering emulsion flood with polymer flood would be effective for the enhanced oil recovery suitable for matured reservoirs.