Oil-wet Carbonate Surfaces Research Articles

Experimental investigation of wettability alteration of oil-wet carbonate surfaces using engineered polymer solutions: The effect of potential determining ions ([Mg2+/ SO42−], and [Ca2+/ SO42−] ratios)

Engineered water polymer flooding (EWPF) is a promising method to improve oil recovery in carbonate reservoirs holding more than half of the world's oil reserves. It involves combining engineered water (EW) and polymer flooding (PF) to modify rock wettability, reduce mobility ratio, promote polymer stability, and lower required polymer concentration. However, limited studies addressed the simultaneous effect of engineered water compositions (i.e. potential determining ions (PDIs)) on the viscosity of polymer and wettability alteration of various carbonate surfaces. Accordingly, this study aimed to investigate the effect of salinity, PDIs, and polymer functional groups (partially hydrolyzed polyacrylamide (HPAM), and acrylamide tertiary butyl sulfonic acid (ATBs)) on the wetting properties of calcite, chalk, and dolomite surfaces as well as the viscosity of solutions at static conditions. The experimental protocol included viscosity, contact angle (CA), pH, and static adsorption tests. Two combinations of PDIs were considered in the study: [Mg2+/SO42−], and [Ca2+/SO42−]. The results revealed that the polymer becomes more tolerant to the salinity as the sulfonation degree increases, given the same molecular weight. However, at a polymer concentration of 5000 ppm, the HPAM polymer showed higher viscosity than the ATBs-based polymers, as the formation brine (FB) was diluted to 100 folds (100DFB). The tendency of shifting the wettability of carbonate surfaces towards a more water-wet state using EW and EWP treatment solutions decreased in the following order: Chalk ≥ Calcite˃ Dolomite. The study also indicates that, the wettability alteration towards favorable condition is dependent on the initial wettability of the carbonate surface. The higher level of oil-wetness detected in aged dolomite, compared with calcite and chalk, resulted in less effectiveness of EWP for dolomites. However, the low polymer interaction with dolomite surfaces indicates a positive impact on reducing polymer consumption. Moreover, the HPAM polymer was more effective in altering the wettability of dolomite towards a water-wet state compared to the ATBs-based polymer. The overall results indicate that ATBs-based polymer is a potential candidate for optimizing the effectiveness of EWPF in carbonates.

Synergistic study of xanthan-gum based nano-composite on PELS anionic surfactant performance, and mechanism in porous media: Microfluidic & carbonate system

Rising global energy demand and decrease in world fossil fuels reserves draw attention toward production from trapped oil in the reservoirs. CEOR methods are proved and efficient methods which can be applied for increased oil recovery. In this research, the EOR potential of a novel nanocomposite and a developed surfactant was evaluated in the presence of various ions and the production enhancement mechanisms were studied using glass micromodel. Primary, the synergistic effect of the nanocomposite and the natural surfactant on Interfacial tension (IFT) reduction and wettability alteration was studied. After quantitative analysis and investigation of the various mechanisms, it was understood that the presence of the nanocomposite in the surfactant solution alters the wettability of an oil-wet carbonate surface to a water-wet one. Adding nano-composite to surfactant solution can improve the wettability alteration ability of the surfactant up to 60.02%. The adsorption tests revealed that combining the nanocomposite with surfactant solution can reduce surfactant adsorption by 18.99 %. The Zeta potential test was utilized to evaluate the stability of the solution. The zeta potential of the nano/surfactant solution was equal to −28 which illustrated a stable solution. In addition, the zeta potential measurements demonstrated the wettability alteration mechanism. After investigating the properties of the nano-surfactant solutions in the presence of different ions, optimum concentrations were determined and the mechanisms of the nano-chemical EOR method were visually investigated by injecting the desired solutions into the glass micromodel. Eventually, five different injection scenarios were designed for the core flood tests to evaluate the performance of each solution in the porous medium. The achieved final recovery for PELS, PELS/NaCl, and PELS/NaCl/NC solutions were 48.05%, 55.62%, and 60.38%, respectively and the Alternative injection scenario was the best injection plan.

An Electrokinetic Study of Amino Acid and Potential-Determining Ions for Enhanced Waterflooding in Carbonate Reservoirs

Summary Reservoir rock wettability plays an important role in waterflooding especially in fractured carbonate reservoirs because oil recovery tends to be inefficient from the mixed-wet or oil-wet rock matrix. Improved oil recovery has been observed by adjusting the concentrations of potential-determining ions (PDIs) to alter the wettability of carbonate rocks. Our previous study showed that the oil recovery from carbonate reservoirs by waterflooding can be enhanced by the addition of glycine, the simplest amino acid. The interaction of glycine anion and oil-wet carbonate surfaces was confirmed in contact angle measurements and yielded the incremental oil recovery in imbibition experiments. This paper presents a surface complexation model (SCM) for the interaction between glycine and oil-wet carbonate surfaces that considers the impact of temperature, pH, salinity, and the concentrations of PDIs. The proposed SCM was tuned based on the zeta potential (ZP) data reported for synthetic calcite in glycine solutions. The tuned model predicts that the strong affinity of glycine for the oil-wet carbonate surface causes the carboxylic acids to desorb from the surface. The concentration of adsorbed carboxylic acids was in qualitative agreement with the water-wetting state of carbonate rocks inferred from the reported contact angle and spontaneous imbibition experiments. Moreover, the model indicates that glycine’s performance as a wettability alteration agent improves significantly at high temperatures. It also suggests that enhanced oil recovery (EOR) by formation brine (FB) with 1 to 3 wt% glycine at high temperatures should be similar to the injection of low-salinity seawater (LSW). The proposed SCM supports glycine’s potential to change the wettability of oil-wet carbonates at high salinity, high hardness, and high temperature.

Investigation of anionic in place of cationic surfactants onto oil wet carbonate surfaces for improving recovery

This paper depicts the utilization of sodium dodecyl sulphate (SDS) that replaces and enhances traditional use of cationic surfactant that is acetylene tri alkyl bromide (CTAB) for improving oil recovery. The SDS was assessed in Alkaline Surfactant Polymer (ASP) slugs containing regularly utilized surfactants with polymers. The impact of SDS on interfacial tension (IFT), adsorption and recovery was contrasted with that of a CTAB in these applications. The SDS was seen as good with saline solutions containing high total dissolved salt and greater volumes of double cations. They can be utilized in saline solutions without the requirement for softening and they give preferable outcomes over traditional CTAB in frameworks where either can be utilized. The SDS has the favourable position of improved recovery with unsoftened saline solution. Their non-reactive properties make them especially appropriate for ecologically delicate applications at on land and offshore oil fields.

Toward mechanistic understanding of wettability alteration in calcite and dolomite rocks: The effects of resin, asphaltene, anionic surfactant, and hydrophilic nano particles

Wettability as related to an oil reservoir represents a fluid ‘s propensity to adsorb or stick to a solid surface in the presence of another immiscible liquid. Therefore, wettability is a key aspect in assessing the degree of recovery of oil from the reservoir. This paper aims at the investigation of the effect of resin, asphaltene, anionic surfactant, and hydrophilic nanoparticles on the wettability alteration of calcite and dolomite rocks. In order to provide a better insight into wettability alteration, several laboratory tests were carried out including energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM). The contact angles measured on the calcite and dolomite rock surfaces for resin (1000 ppm in toluene) after three weeks were 88° and 93°, respectively. The results of contact angle analyses as a screen for two rocks (calcite and dolomite) wettability showed that resin altered the wettability of rock samples to oil-wet. Also, asphaltene as a heavy and polar component has more influence than resin on the wettability alteration towards oil-wet state. The polarization interaction mechanism is the principle method for altering the wettability of samples by asphaltene and resin. EDX analysis illustrated that the amount of carbon and oxygen after aging rocks in oil, asphaltene, and resin increased, and the heteroatoms N and S were appeared on the calcite and dolomite surfaces. Afterwards, the combination of silica (SiO2) nanofluid and anionic surfactant (sodium dodecyl sulfate (SDS)) for modification of wettability of oil-wet carbonate surface was investigated. The most significant changes were observed after 24 h of contacts of rocks with a mixture of nanofluid and anionic surfactant. The contact angle decreased from about 88° to 16° for calcite and from 93° to 15° in the case of dolomite. The main mechanisms responsible for wettability modification by SiO2-SDS surfactant are: first) hydrogen bonding between the hydroxyl groups of silica nanoparticles and the tail of the anionic surfactant, second) the adsorption of SiO2-nanoparticles to the carbonate rock substrate due to a high degree of negative charges.

Universal scaling of adsorption of nonionic surfactants on carbonates using cloud point temperatures

HypothesisNonionic surfactants alter the wettability of oil-wet carbonate surfaces to a water-wet state. The degree of surfactant adsorption is expected to determine the extent of the wettability alteration. Furthermore, the structure of the hydrophobic and hydrophilic units of the surfactant should affect the degree of adsorption and correlate with the wettability alteration. ExperimentsThe adsorption on Indiana limestone was measured for nonionic surfactants with two different types of hydrophobic units and hydrophilic polyethoxylate units ranging from 15 to 40 mers. Measurements were conducted for several surfactant concentrations and temperatures. FindingsAdsorption increased with temperature and for surfactants with fewer hydrophilic groups. The adsorption occurs as micelles rather than individual surfactant molecules. An increase in adsorption is observed for the more hydrophobic surfactants at higher temperature and is attributed to the increase in micelle sizes. Adsorption collapses onto a universal curve as a function of the difference between cloud point of the surfactant and system temperature. At the same time wettability alteration was found to have a direct correlation with surfactant adsorption. These findings are critical for judicious selection of nonionic surfactants for analysis and design of wettability alteration for oil reservoirs.

Interaction of Stabilized Alkylbenzene Sulfonate Surfactants on the Nanoscale with Water-Wet and Oil-Wet Carbonate Surfaces under High-Salinity and High-Temperature Conditions: A QCM-D Study.

Understanding the interactions of surfactants and wettability alteration of surfaces is important for many fields, including oil and gas recovery. This work utilizes the quartz crystal microbalance with dissipation to study the interaction of stabilized linear and branched alkylbenzene sulfonates (ABSs), among the most cost-efficient industrial surfactants, with water- and oil-wet calcite surfaces under high-salinity and high-temperature conditions. Confocal laser scanning microscopy is also used to study the effect of the type of ABS on their interaction with oil-wet calcite surfaces. Experiments demonstrate that vesicles made of linear and branched ABSs interact differently with both water- and oil-wet surfaces. Therefore, surfactant formulations made of ABSs for high-salinity applications can further be improved for advantageous wettability properties by varying the hydrophobic chain of the surfactants. When interacting with a water-wet surface, both types of vesicles adsorb onto the surface as is. Upon dilution, however, vesicles made of linear ABS stay adsorbed as is, and vesicles made of branched ABSs disassemble and produce a layered structure with altered wettability. Linear ABSs show greater efficiency in desorbing oil from the oil-wet calcite. The results of this study demonstrate an improved method for studying and understanding the interaction of surfactant formulations with water- and oil-wet surfaces. This approach could significantly benefit applications in which wettability alteration of surfaces is of great interest and facilitate the implementation of low-cost surfactants based on petroleum sulfonates.

Wettability alteration of oil-wet carbonate surface induced by self-dispersing silica nanoparticles: Mechanism and monovalent metal ion's effect

Various analysis methods including IR, SEM, contact angle determination and spontaneous imbibition experiments were used to investigate the mechanism of wettability alteration of oil-wet carbonate surface by silica nanoparticles (NPs) in the present study. Stable silica nanofluids were first studied through zeta potential measurement. Results show that there is an optimal sonication time interval (5 h) for the preparation of SiO2 nanofluid after the magnetic stirring treatment in this work. The addition of NaCl can decrease the dispersion stability of SiO2 nanofluids. Both IR and SEM results show that the originally water-wet silica NPs are adsorbed on the calcite surface, making the surface water-wet. The role of sodium ions is to compress the electric double layer, giving the nanoparticle (NP) an opportunity to access the palmitic acid molecules. The palmitic acid molecules are replaced by the NPs through competitive adsorption. The longer the contact time, the better the performance of wettability alteration of oil-wet carbonate rock by the nanofluid. The contact angle decreases as the NPs concentration increases. Among the metal ions in the formation water, Na+ ion is closest to the solid surface, making Na+ ion have a great influence on wettability change of oil-wet carbonate surface by silica NP. Na+ ions in the solution can neutralize some negatively charged portion of the carbonate surface, making the adsorption amount of silica NPs on the solid surface increase. Thus, wettability alteration of oil-wet carbonate surface by SiO2 NPs is improved in the presence of Na+ ions. During the spontaneous imbibition experiments, silica NPs are adsorbed on rock surface and gradually form a wedge film in the contact area of the three-phase (oil-water-solid). In this case, structural disjoining pressure is generated due to the presence of electrostatic repulsion and Brownian motion of silica NPs. When the structural disjoining pressure is stronger than the oil droplet adhesion, the contact area of oil droplet on the solid surface gradually decreases, making the oil droplet eventually peel off from the rock surface.

Ion type adjustment with emphasize on the presence of NaCl existence; measuring interfacial tension, wettability and spreading of crude oil in the carbonate reservoir

Finding the high-performance anions and cations in the aqueous solutions are crucially required during the smart water injection make it the main core of many enhanced oil recovery (EOR) studies. Nevertheless the previously published literature revealed a lack of understanding about the synergistic or antagonistic effect of NaCl (as the most abundant salt in the sea water) and other salts with the same ionic strength on the interfacial tension (IFT), wettability alteration and spreading coefficient. Therefore, the main purpose of this study is aimed on this concern. To reach this goal, the dynamic IFT values of crude oil/different aqueous solutions with ionic strength of 0.7 M and contact angle values between these phases on the oil wet carbonate surface soaked under different times in the prepared aqueous solutions are measured. After that, the measured values are used to calculate the spreading coefficient and distribution capability of oil and water phases on the carbonate rock surface. The obtained results revealed that to change the wetting state of carbonate rock toward a more water wet state, a synergistic effect was observed between NaCl and salts containing sulfate anion, i.e. Na2SO4 and MgSO4.

Role of Brine Composition and Water-Soluble Components of Crude Oil on the Wettability Alteration of a Carbonate Surface

In this study, the effects of amphiphilic water-soluble components of crude oil and ionic composition of water were investigated on the wettability alteration of a carbonate surface. Four different types of saltwater, which are made up of NaCl, MgCl2, CaCl2, and Na2SO4, with 0.5 M ionic strength, besides distilled water, were contacted with crude oil to be saturated with water-soluble components. The post-contact (after contact with crude oil) water properties were characterized by Fourier transform infrared spectroscopy, total organic carbon, and pH analyses. The results showed that some polar compounds of crude oil with basic and mostly acidic functional groups were transferred to saltwater and distilled water. Afterward, the oil-wet carbonate surface was soaked in both freshwater (not contacted with crude oil) and post-contact water, and their effects on the wettability of the surface were investigated through contact angle and scanning electron microscopy experiments. The results of the contact angle ...

Interfacial Interaction of Cationic Surfactants and Its Effect on Wettability Alteration of Oil-Wet Carbonate Rock

Oil recovery by water flooding from carbonate reservoirs is considered ineffective because of the capillary forces in naturally fractured oil-wet carbonate formations. Surfactant solutions are often recommended to enhance the oil recovery by both wettability alteration and reduction of interfacial tension (IFT). In this study, the effects of cationic surfactants from the trimethylammonium bromide (CnTAB) family, viz., C10TAB (BTAB), C15TAB (DTAB), C16TAB (TBAB), and C19TAB (CTAB), on the surface tension, IFT, and wettability alteration of a carbonate rock along with adsorption of the surfactant on the carbonate rock were investigated. Different analyses, including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), and Fourier transform infrared spectroscopy (FTIR), were conducted to study the mechanism for wettability alteration of the oil-wet carbonate surface. Results demonstrated that, among the four surfactants used, C15TAB and C19TAB presented a ...

Mechanistic study of wettability alteration of oil-wet calcite: The effect of magnesium ions in the presence and absence of cationic surfactant

Abstract Over 60% of the world’s discovered oil reserves are held in carbonate reservoirs, which are mostly naturally fractured. Conventional water flooding results in low oil recovery efficiency in these reservoirs as most of them are oil-wet. On account of negative capillary forces, injected brine cannot penetrate simply into an oil-wet matrix of fractured formations to force the oil out. Wettability alteration of the rock surface to preferentially more water-wet state has been extensively studied using both smart water and surfactants separately. This study aims to study the effects of Mg2+ as one of the most important wettability influencing ions on the wetting properties of oil-wet carbonate surfaces in the presence and absence of cationic surfactant. Different analytical tools were utilized to examine the interactions between calcite surface, Mg2+ and surfactant. Results show that, magnesium ions are able to remove the strongly adsorbed carboxylate group from the surface and change the wettability of calcite surface to more water wet status. However, the presence of surfactant improves this process and enhances the wettability alteration toward more water wet. It has been demonstrated that the interaction of magnesium ions with adsorbed carboxylate on the surface hence forming a complex with carboxylate group as well as ion–pair formation between cationic surfactant and adsorbed carboxylate are the main mechanisms of wettability alteration which has resulted in removing the carboxylate from the calcite surface.