Applications of Surfactants and Nanoparticles in Enhanced Oil Recovery Processes

The surfactant injection is considered as the EOR (Enhanced Oil Recovery) with the highest potential to recover oil from reservoirs due to its ability to reduce interfacial forces into the porous medium. However, the adsorption of this type of chemical on the surface of rocks is the main problem when a surfactant injection project is applied since the surfactant molecules would rather be placed on rock minerals instead of being the oil–water interface. Based on this fact, this chapter would be discussed the significance of surfactant injection as an EOR method, the types of surfactants used, the main mechanism and parameters involved in the surfactant adsorption on the rock, and its consequences in oil recovery. Likewise, the addition of nanoparticles to inhibit the adsorption of surfactants is another topic that will be covered as a novel technology to improve the efficiency of the EOR process.

Formation of a surfactant adsorption layer on microroughnesses of friction surfaces

Formation of an adsorption surface layer on microneralities of friction surfaces. The model of interaction of the molecule of surface-active substance with the microasperity of friction surface has been given. It has been found that the distance of interaction and the thickness of an adsorbed layer of surface-active substances depend on value of a field of an adsorbing surface and energy of thermal oscillations of molecules of surface-active. It has been shown that the distance of interaction and the thickness of an adsorbed layer of surface-active substances decrease at magnification of temperature of working liquid.

New Insights into Surfactant Adsorption Estimation During ASP Flooding in Carbonates Under Harsh Conditions Using Surface Complexation Modeling

Several laboratory experiments demonstrated that the use of sodium hydroxide could increase the solution pH and reduce the adsorption of anionic surfactants. However, a better understanding of rock-oil-brine interactions and their effect on surfactant adsorption during alkaline-surfactant-polymer (ASP) flooding is needed for realistic and representative estimations of surfactant adsorption levels. Therefore, this study presents a novel approach to capture these interactions and better predict their effect on surfactant adsorption as well as effluent concentrations of surfactant and various aqueous species. Currently, surface complexation models (SCM) consider rock-brine, oil-brine, and surfactant-brine reactions. In this work, four new surface complexation reactions with intrinsic stability constants that honor oil-surfactant interactions have been proposed for the first time and then validated against experimental data reported in the literature. In addition, we analyzed the effect of various parameters on surface adsorption under harsh conditions of high-temperature and high-salinity using the proposed surface complexation model (SCM). The results showed that the developed surfactant-based SCM is robust and accurate for estimating surfactant adsorption and its concentration in the effluent during chemical floods. The model was validated against two sets of ASP corefloods from the literature including single-phase and two-phase dynamic surfactant adsorption studies. The findings highlighted that oil-surfactant surface complexation reactions are important and should be captured for more representative and accurate estimation of surfactant adsorption during chemical flooding. Moreover, the detail and comprehensive analysis showed that surfactant adsorption increases and its concentration in the effluent decreases with the increase in temperature of the chemical flood, which could be due to the increase in kinetic energy of the species. It was also showed that a decrease in water total salinity decreases the surfactant adsorption on the rock surface, which is related to the increase in the repulsive forces between the adsorbed species. Additionally, with the increase in surfactant concentration in the chemical flood, the effluent surfactant concertation increases, with a slight increase in surfactant adsorption. This slight increase in adsorption can be neglected compared to the injected and produced masses of the surfactant that are proportional. Moreover, the effect of sulfate spiking is significant where the increase in sulfate concentration reduces the surfactant adsorption. Furthermore, it is worth highlighting that the lowest surfactant adsorption levels were achieved through injected water dilution; less than 0.1 mg/g of rock. This is the first study to test a novel formulation of surface complexation modeling considering oil-surfactant effect on surfactant adsorption properties. The proposed framework to estimate surfactant adsorption is conducted for high-temperature and high-salinity reservoir condition. Thus, it could be used in numerical reservoir simulators to estimate oil recovery due to wettability alteration by chemical flooding in carbonates, which will be investigated in our future work. The surfactant adsorption mechanisms during chemical flooding is very case-dependent and hence, the findings of this study cannot be generalized.

Adsorption Inhibitor Role in a Constant Salinity Surfactant-Polymer CSSP Flooding Design for an Offshore Field Application

A base chemical flooding formulation using alkaline-surfactant-polymer (ASP) has been developed for application in offshore environments. The formulation uses combination of conventional alkali (sodium carbonate) with amphoteric surfactant. The field is currently under waterflooding using sea water as injection water. However, since alkali is incompatible with divalent ions in sea water, an alternative formulation using seawater with no additional water treatment is also being developed and considered for application. The alternative formulation uses combination of alkyl propoxy sulfate (APS) and alkyl ethoxy sulfate (AES). Coreflood recovery performance of both formulations is similar. Without alkali, high surfactant adsorption becomes major concern for the alternative formulation. Thus, an adsorption inhibitor (AI) agent – polyacrylic acid type, is being considered as an additive to address this concern. While AI showed potential in reducing surfactant adsorption and improving oil recovery efficiency, it can also increase overall cost for the surfactant in sea water chemical formulation. Hence, the merit to apply AI was not clearly observed.

Electrochemically Assisted Deposition of Calcium Carbonate Surfaces for Anionic Surfactant Adsorption: Implications for Enhanced Oil Recovery

Surface roughness of rocks had a significant influence on surfactant adsorption in enhanced oil recovery (EOR), both in terms of the total amount adsorbed as well as of the kinetics of adsorption. Combining electrochemical techniques and quartz crystal microbalance with dissipation monitoring (QCM) into one analysis setup opens up new avenues for depositing model rock surfaces and investigating the adsorption behavior. Using electrochemically assisted deposition, uniform and well-covered metal-CaCO3 sensors were obtained to simulate rough carbonate rocks and characterized by scanning electron microscope with energy dispersive X-ray analysis (SEM-EDX). The deposition process was controlled by the nitrate and oxygen electroreduction reactions in the presence of bicarbonate and calcium ions. The deposited mass of CaCO3 was calculated and the coverages for Au-CaCO3 and Pt-CaCO3 sensors were between 20 - 60%. It is observed that mostly cubic-like CaCO3 crystals were formed with crystal sizes around 20 to 50 µm from the SEM micrographs. The bigger crystals were surrounded by bare regions of Pt surface, suggesting the existence of Ostwald ripening process. Prior to the investigation of the deposited CaCO3 surfaces, the adsorption of anionic surfactant alcohol alkoxy sulfate (AAS) was studied on a smooth commercial CaCO3 surface with varying pH and CaCl2concentrations using QCM. Subsequently, surfactant adsorption was performed on the rough deposited CaCO3 surfaces and their adsorption behavior were compared. On a smooth CaCO3 surface, a fast adsorption of AAS surfactant was observed, whereas the desorption process was characterized as a two-step process. Compared to the smooth CaCO3surface, an increase of the frequency shift of about 5 times was observed on the deposited CaCO3 surfaces. This observation was mainly ascribed to the rougher surfaces, having more adsorption sites for AAS binding, and also the liquid trapping effect, resulting in more frequency shifts. It is suggested that a rough model mineral surface could be a better representation of a rock surface, presenting the implications of the new understanding for surfactant adsorption on different rock surfaces in EOR.