Jitendra Sangwai

Production of crude oil from a matured oil reservoir is challenging due to the low recovery factor. Hybrid methods have demonstrated potential in oil recovery from the matured crude oil reservoir. In recent years, the low salinity water with chemicals (viz., surfactant, polymer) and nanoparticles have brought the attention of the researchers due to their ability in altering the interfacial properties of the rock-oil-water systems favorable for crude oil recovery. The current interest by industries in injection fluid (i.e., low salinity water injection) has prompted the invention of a hybrid oil recovery agent for matured crude oil reservoirs. In the current study, a novel silica-based hybrid nanofluids (NFs) of variable silica nanoparticles (NPs) concentration in low salinity seawater with anionic surfactant (AOT: dioctyl sodium sulfosuccinate) and polymer (PVP–K30: polyvinylpyrrolidone) (sometimes referred to as SMART LowSal) are used as an injection fluid in a sand-pack reactor. Oil recovery from oil saturated sand-pack reactor is observed to enhance due to NFs (hybrid) injection after secondary recovery. The characteristic study of relative permeability curves discloses that sand surface was initially water-wet and converted to strongly water-wet in the presence of NFs. A nuclear magnetic resonance (1H NMR) study reveals that adsorption of the chemical appeared on the sand surfaces, which could be the reason for wettability alteration, and thereby enhanced oil recovery. Similarly, the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) of the sand samples before and after injection disclosed desorption of hydrocarbon from the sand surfaces after NFs injection. An additional 5–10% oil recovery is achieved after chemical flooding due to the injection of NFs. Adsorption isotherm study well agreed with the monolayer adsorption of surfactant on the sand surface.

Although various efficient enhanced oil recovery (EOR) techniques have been proposed, the use of chemicals such as alkali, surfactants, and polymer in the field of EOR makes chemical EOR a promising method. The residual oil left behind after the secondary recovery process can be successfully displaced by decreasing the interfacial tension (IFT) between the liquid-liquid systems. Moreover, understanding the IFT between the liquid-liquid systems are essential in formulating and controlling the multiphase and multicomponent processes. As crude oil is a complex mixture of organic, inorganic compounds and heteroatoms, understanding the IFT of the pure hydrocarbon-water system is vital to develop robust models. In this study, the IFT between pure hydrocarbon-water systems in the presence of alkali has been explored. The IFT measurements were performed using a dynamic contact angle tensiometer using a Wilhelmy plate. Different hydrocarbon liquids such as hexane, heptane, decane and aromatics such as benzene and toluene were used. The monovalent NaOH and divalent alkali Ca(OH)2 in the concentration range of 0–37.5 mM are used to understand the effect of alkali on the IFT of the oil-water system. This paper also elaborates on the effect of temperature at 298.15 K, 323.15 K and 348.15 K on the IFT of hydrocarbon-water systems. The experimental results show that the increase in the concentration of alkali continuously decreased the IFT of hydrocarbon-water systems. Moreover, it has been found that the type of alkali also has a reasonable impact on the IFT of the hydrocarbon-water system. The divalent alkali [Ca(OH)2] is found to be more efficient in reducing the IFT of both alkane-water and aromatic-water systems than the moderately performed monovalent alkali (NaOH). The possible mechanism for the continuous reduction in IFT has been proposed using surface adsorption of hydroxide ions at the interface of the oil-water system.

The purpose of the present work is to evaluate applicability of ionanofluids for enhanced oil recovery (EOR) applications. Two different ionanofluids have been prepared for this study by adding silica nanoparticles into two different ionic liquids (tripropyl ammonium sulphate and triethyl ammonium sulphate) solutions. The effects of nanoparticle and ionic liquid on the interfacial tension of crude oil-nanofluid and their enhanced oil recovery performances have been evaluated. Ionanofluids are found to have the ability to reduce the interfacial tension to a significantly low value. The results of this study also indicate that ionanofluids has much higher enhanced oil recovery efficiencies in comparison to nanofluid and ionic liquid alone. Therefore, ionanofluids have the potential to be used as an excellent future EOR agent.

Spontaneous imbibition is a common phenomenon noticed in low permeability reservoirs during oil recovery. A considerably good amount of oil can be recovered by imbibition of efficient injection fluid for a prolonged time. Recent interest on the low salinity water injection (LSWI/LowSal) has prompted the development of SMART LowSal injection fluid for enhanced oil recovery (EOR). In this work, novel hybrid silica-based nanofluids (NFs) of varying concentrations of silica nanoparticles (SiO2 NPs) in diluted seawater with anionic surfactant (AOT) and polymer (PVP-K30) (referred to as SMART LowSal) were used as an imbibition agent. Interfacial tension (IFT) and contact angle measurements were carried to understand the impact of novel hybrid NFs on the IFT of oil-NFs system and wettability of rock. Berea sandstone cores were used to understand the efficacy of novel SMART LowSal injection fluid for EOR through spontaneous imbibition. The aged oil saturated cores were analyzed with X-ray computed tomography (CT) and energy dispersive X-ray (EDAX). Amott cell was used for imbibition test to evaluate the efficiency of the novel hybrid NFs for EOR. The oil recovery due novel hybrid NFs is found to be significantly higher than that of LSW and deionized water. The oil saturated core surfaces were analyzed with scanning electron microscopy (SEM) and EDAX before and after oil recovery to understand the surface properties of the cores. The novel hybrid NFs showed excellent potential for enhanced oil recovery (EOR). This is one of the first study of its kind using surfactant, polymer and nanoparticles in diluted seawater to prepare NFs and its use for enhanced oil recovery. This study provides vital information about the hybrid NFs as an alternative injection fluid for EOR applications.

Controlled salinity water flooding also known as engineered water flood has been tested as a potential enhanced oil recovery (EOR) method in laboratory as well as at pilot/field scale. However, there are cases seen where the method has failed to show its potential for EOR. Scientists believe that the lack of understanding of case specific underlying mechanism is the primary reason. Many of the literatures claims reduction of interfacial tension as the primary oil recovery mechanism; but recent findings highlighted that modification of electrical charges on rock surface with response to injection brine salinity has greater effect. In order to investigate the same and in search of more insightful mechanism, in this study we have designed and performed experiments with selected chemicals which can modify surface properties of sandstone and also the oil water interfacial tension. The electrical charge of the rock surface and oil–brine​ interfacial tension were modified by tuning salinity of injection water and adding surfactants (sodium dodecyl benzene sulfonate, SDBS and cetyltrimethylammonium bromide, CTAB). The electrical charge of the sandstone surfaces was quantified with zeta potential measurement. The oil recovery potential of the injection fluids was tested through laboratory core flooding experiments at controlled near reservoir conditions. Superposition of all the obtained results revealed that low salinity injection brine modifies the sandstone surface to higher negatively charged state than high salinity water. Therefore, with a negatively charged oil–brine interface it causes strong repulsive forces promoting detachment of residual oil and subsequent mobilization. The hypothesis is also proved by the fact that SDBS in spite of resulting in a lower interfacial tension reduction than CTAB yielded higher oil recovery. This is because of the negative zeta potential caused by SDBS to sandstone surface in comparison to the positive zeta potential observed in the case of CTAB.