Jitendra Sangwai

Matured reservoirs are being targeted for enhanced oil recovery (EOR) operations in the hope to recover the residual oil that remains trapped within the porous media. Chemical enhanced oil recovery is one of the successful oil recovery methods which is being employed for the recovery of the residual oil. Many of the conventional chemicals fail to perform under high temperature and high saline reservoir conditions. These situations lead to the search for alternate flooding techniques which could efficiently produce the crude oil to the surface. The present work investigates a possible solution for the recovery of trapped crude oil using lactam and imidazolium based ionic liquids (ILs) specifically targeted towards recovery in high saline environment. Initially, the interfacial tension of the crude oil-water system has been investigated using various chemical agents, such as sodium dodecyl sulfate (SDS), and six different ILs at varying high saline concentrations as a function of temperature (283.15–353.15 K). Subsequently, flooding experiments with only polymer, only SDS, only IL, SDS + polymer and IL + polymer at zero and high saline conditions were performed. It was observed that the IL + polymer flood performed very well in both zero and high salinity conditions as compared to all other flooding systems. The present investigation also portrays an intuition on the evaluation of ILs based on their alkyl chain length.

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.

An ultra-low IFT (interfacial tension) is required between the liquid–liquid systems to dislodge the crude oil completely from the pores of the formation. As a huge amount of alkali is used for this purpose, scale formation and formation damage near wellbore region is a common issue. To perform an economically and environmentally viable process, it is obligatory to design the process with low and optimum concentration of alkali. Moreover, if the concentration of alkali is properly designed according to the oil chemistry, the alkali flooding alone could result in a favorable recovery for high acid number crude oil. So, the present study utilized low concentration of NaOH, to understand the behavior of alkali at the IFT of hydrocarbon–water system. Hydrocarbons like heptane and benzene were selected to understand the influence of hydrocarbon type on the IFT reduction. It was found that the IFT between the hydrocarbon–water system continuously decreases with an increase in NaOH concentration; moreover, a minimum concentration of 100 ppm is required to initiate reduction reaction. It is evident to state that IFT is dependent upon type of the hydrocarbon, because the enhanced reduction is observed in aromatics–water system using NaOH due to stronger cation-π interaction.

Nanotechnology is a common word used by academia which is referred to the applied nanoscience conducted at nanoscale (1–100 nm) for variety of industrial applications. Application of nanotechnology in various fields is increasing extensively resulting in an enormous amount of publications in the distinct field. Nanoparticles (NPs) possess unique properties due to their larger surface area which leads to prolong application in multifold. Researchers working in enhanced oil recovery (EOR) areas are trying to get rid of challenges faced by the oil and gas companies for crude oil production. This chapter, therefore, focuses on work carried out by the researchers on chemical and rarely on thermal, gas injection, and biological EOR methods using NPs. Chemical enhanced oil is recovery (CEOR) methods taken into consideration due to their popularity in oilfields than the other existing methods. Viscosity, interfacial tension (IFT), and wettability are the major influencing factors for EOR. The authors intend to make the reader understand the pore-scale mechanism behind the enhanced oil recovery in the presence of NPs. In the early stage of enhanced oil recovery, it is essential to understand the properties of various NPs. Literature review reveals that properties of NPs mostly depend on methods they are prepared. Hence, at the beginning of the chapter, the types of NPs, preparation, and their characterization are explained briefly with the application of various nanoparticles in CEOR. Limitation of NPs application in chemical EOR area is spelled out clearly with the recommendation at the end.

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.

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.

The need for development of better surface active agents for upstream oil and gas industry which can survive harsh condition of salinity are in great demand, particularly for the applications related to improved/enhanced oil recovery, flow assurance and oil and gas production operations keeping in mind the environmental constraints. The technical difficulties which need to be considered are those involving the surface forces such as surface tension (SFT) and interfacial tension (IFT) acting between the formation water and the low waxy crude oil. In this study, we have employed the use of eight aliphatic ionic liquids (ILs), based on di- and tri-alkyl ammonium as cations and with various anions such as [CH3COO]-, [BF4]-, [H2PO4]- and [HSO4]- for the investigation of the surface phenomenon of crude oil-water system. The synergistic effect of NaCl along with the ILs is investigated in detail. It is observed that there is a significant reduction in the surface tension of water and the interfacial tension of crude oil-water system in the presence of salt, particularly at higher concentration of NaCl (200,000ppm). Effect of temperature, time, alkyl chain length of the cationic part of the ILs, nature of anions of ILs and the concentration of ILs is also discussed. The trend in the electrical conductivity of aqueous IL solutions with various concentrations at three different temperatures 298.15-318.15K is also presented along with critical aggregation concentration. The study on the effect of ILs on the SFT/IFT of water and low waxy crude oil-water system reveal that the ILs are successful in minimizing the effect of the surface forces in the presence of salt and thereby, could pave the way for efficient enhanced oil recovery operations.

Interfacial tension between hydrocarbon liquids and salt water is a very important property for many industrial applications, especially in petroleum industry. Interfacial tension, in addition to other factors, has direct impact on displacement process in porous media so thus on oil recovery. Very recently, the salinity of injection brine has been regarded as a key factor in oil recovery using low salinity water flooding process. Decrease in the interfacial tension between crude oil and injection brine at low salinity condition might be a reason behind recovery improvement as suspected by some researchers; but there are also other effects associated with low salinity water flooding like wettability alteration, fine migration, mineral dissolution etc. It is suspected that the interaction of polar components at oil-water interface lead to the reduction of interfacial tension. However, the actual mechanism is not known and still under research. The main objective of this work is to determine the effect of salt concentration and type of ions present in an aqueous phase on the interfacial tension between pure hydrocarbon liquids and water. Different hydrocarbon liquids, such as aliphatic and aromatics, have been tested to understand the interaction of monovalent and divalent salts on the interfacial tension. The study reports the interfacial tension of five pure hydrocarbon liquids against solutions of three different salts (NaCl, MgCl2 and CaCl2) over a wide range of salinities. The interfacial tension measurements were done using Wilhelmy plate method by a dynamic contact angle tensiometer. All the experiments were conducted at room temperature and atmospheric pressure. The results lead us to the view that there is low a salinity concentration where the hydrocarbon/brine interfacial tension shows a minimum value. The type of salt also has a significant effect on interfacial tension of aliphatic and aromatic hydrocarbons. Monovalent salt found to be effective in reducing interfacial tension of aliphatic hydrocarbons while divalent salts were found to be effective for aromatic hydrocarbons. The possible mechanism for the reduction in IFT at low salt concentration has also been explained using Gibb's adsorption isotherm. In addition, the trend in IFT has been explained in the light of well-known Jones-Ray effect.