The need for efficient demulsification process to treat emulsions in the petroleum industry is well acknowledged. For decades, numerous researches have been conducted to examine mechanisms of emulsification and demulsification. Untreated emulsion has both technical and commercial implications in the industry, especially in terms of treatment facilities, refining and transportation. Effective treatment is needed to ensure optimum production of hydrocarbons. The present paper is to review reported works on the formation of petroleum emulsions, demulsification treatments, characteristics of fit-for-purpose demulsifiers as well as research trends in emulsion treatment. Crude oils are naturally combined with natural surfactants having high tendency to form stable emulsion. The stable emulsion must be treated well to meet industrial requirements since crudes with a high volume of stable emulsion have a less value. Therefore, fundamental studies on natural surfactants, which contribute to the emulsion stability, are analyzed for the effective separation of emulsions into oil and water. This would involve the assessment of various reported mechanisms for the emulsification and right formulation for effective demulsification.

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A new cost-effective in-depth fluid diversion has been developed and reported. In this paper, the diverting agent is prepared successfully from natural bentonite particles that were modified with N-isopropylacrylamide (NIPAM) and acrylic acid (AA) copolymers. First, bentonite particles were intercalated with small precursor molecules that contained functional groups. These precursors were used to reduce the bentonite particle size and introduce a vinyl group for subsequent polymerization. Then, poly(NIPAM-co-AA) was grafted onto hydrophilic bentonite through a free radical polymerization process. The grafted bentonite morphology, microstructure, and thermal stability were investigated using FTIR spectroscopy, dynamic light scattering, XRD, and TGA measurements. The particle dispersion stability and rheological properties have been investigated by using a turbidimeter and rheometer. Sand packs and core flooding tests were conducted to investigate the injectivity and determine permeability reductions. Experimental results obtained revealed that the grafted bentonite was easily injected and gradually built flow resistance by particle straining and physical-chemical attachment. A significant permeability reduction fraction was observed when the diverting agent was injected into a brine saturated sand pack column. Increasing flow rate resulted in increasing pressure drop across the sand pack and a decrease in permeability reduction fraction. The results indicate that attached grafted bentonite particles deform by shear. Two-phase core flooding results show rock permeability reduced by 80% with an oil recovery increment of 12% after injecting grafted bentonite. These significant results highlighted new insights for successful applications of modified bentonite to improve reservoir conformance problems.

Recently, nanoparticles have proven to enhance oil recovery on the core-flood scale in challenging high-pressure high-temperature reservoirs. Nanomaterials generally appear to improve oil production through wettability alteration and reduction in interfacial tension between oil and water phases. Besides, they are environmentally friendly and cost-effective enhanced oil recovery techniques. Studying the rheological properties of nanoparticles is critical for field applications. The instability of nanoparticle dispersion due to aggregation is considered as an unfavorable phenomenon in nanofluid flooding while conducting an EOR process. In this study, wettability behavior and rheological properties of surface-treated silica nanoparticles using internal olefins sulfonates (IOS 20-24 and IOS 19-23), anionic surfactants were investigated. Surface modification effect on the stability of the colloidal solution in porous media and oil recovery was inspected. The rheology of pure and surfacetreated silica nanoparticles was investigated using a HPHT rheometer. Morphology and particle size distributions of pure and coated silica nanoparticles were studied using a field emission scanning electron microscope. A series of core-flood runs was conducted to evaluate the oil recovery factor. The coated silica nanoparticles were found to alter rheological properties and exhibited a shear-thinning behavior as the stability of the coated silica nanoparticles could be improved considerably. At low shear rates, the viscosity slightly increases, and the opposite happens at higher shear rates. Furthermore, the surfacemodified silica nanoparticles were found to alter the wettability of the aqueous phase into strongly water-wet by changing the contact angle from 80° to 3° measured against glass slides representing sandstone rocks. Oil-water IFT results showed that the surface treatment by surfactant lowered the oil-water IFT by 30%. Also, the viscosity of brine increased from 0.001 to 0.008 Pa s by introducing SiO 2 nanoparticles to the aqueous phase for better displacement efficiency during chemicalassisted EOR. The core-flood experiments revealed that the ultimate oil recovery is increased by approximately 13% with a surfactant-coated silica nanofluid flood after the conventional waterflooding that proves the potential of smart nanofluids for enhancing oil recovery. The experimental results imply that the use of surfactant-coated nanoparticles in tertiary oil recovery could facilitate the displacement efficiency, alter the wettability toward more water-wet and avoid viscous fingering for stable flood front and additional oil recovery.

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One of the major challenges in the upstream oil and gas industry is to control and reduce high water production from a large number of oil wells. A relative permeability modifier (RPM) has been proven to offer a potential solution for excessive water production at core and field scales. A good RPM must be of a cost-effective and simple agent that could easily be prepared in the field to control water production without requiring major workover equipment. This paper discusses the performance of a newly formulated grafted nanoclay (GN) for conformance control at high-temperature conditions and application as a permeability modifier. The interfacial tension (IFT) reduction and wettability change were quantified via pendant drop and contact angle measurements, respectively. Laboratory studies were performed using Berea and native sandstone cores to determine the effect GN on effective water and oil permeability. Experimental results obtained revealed that upon injection GN can immediately create a high flow resistance to the injected water. The regained water and oil permeability were 16% and 89%, respectively, after GN injection when the Berea core was used. A similar high resistance factor to water was obtained when a native core was used. Adsorption of GN on the substrate reduced the contact angle toward water-wetting combined with a reduction in IFT from 20.78 ± 1.48 mN/m between an oil–brine system to 8.67 ± 1.01 mN/m for an oil–GN system. These new results highlighted new insights for successful applications of GN to improve reservoir conformance in oil production wells.

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