STUDYING THE INTERACTIONS BETWEEN AN ARABIAN HEAVY CRUDE OIL AND ALKALINE SOLUTIONS

ABSTRACT

An experimental study to examine the effectiveness of alkaline flooding for the recovery of an Arabian heavy crude oil is presented. The interfacial tension (IFT) behavior of crude oil/alkali systems over a wide range of parameters (pressure, temperature, alkali concentration and time) was studied. These alkaline reagents react with the acidic species in crude oil to form surface-active soaps in-situ. This leads to a lowering of interfacial tension (IFT) and subsequently the mobilization of residual oil. The equilibrium IFTs obtained through alkaline flooding are compared with the IFTs when a synthetic surfactant (dodecyl benzene sulfonic acid sodium salt) is used in EOR recovery. A mathematical model representing the complete chemistry of the transient process is also presented. The model consists of a set of differential equations describing reactions, diffusion, and adsorption at the oil/alkaline solution interface. The kinetic parameters in the model are obtained through a differential algebraic optimization technique. The concentration of the surface active species are related to the measured IFTs through an independent step that is based on isolating the surface active species formed by the reaction between the acids in the crude oil and the alkaline solution. A sensitivity analysis using the model is carried out to study the effect of surface potential and alkaline concentration on the transient interfacial tensions.     

用中和烃氧化产物制备高界面活性的驱油剂

为了用C_(22)和C_(26)直链和环烷烃的石油馏分油作原料制备适用于强化采油的活性剂,先将原料汽相氧化,再用碱液中和氧化产物。用红外光谱研究了氧化产物和中和产物的组成,发现前者含有羧酸,后者含有羧酸盐。得到的羧酸盐活性剂用于模拟油[由38.8%(体积)的异丙苯和61.2%(体积)的正癸烷组成],使油水间达到低于10~(-2)mN/cm的超低界面张力。实验表明,用氢氧化钠进行中和,比用其他的碱性物质(如硅酸钠、三聚磷酸钠、碳酸钠)更易得到界面活性高的活性剂溶液;当硅酸钠或三聚磷酸钠协同氢氧化钠一起与氧化产物反应时,所得活性剂的界面张力对电解质浓度的敏感程度比仅用氢氧化钠作处理剂时低,中和时的碱量会影响所得活性剂体系的界面张力。对于活性剂浓度不同的体系,若pH值相同则最佳含盐量也相同;若pH值高,则最佳含盐量低。当活性剂体系含有1000ppm的氯化钙时,仍具有良好的界面活性。在驱油试验中,浓度为1%的1个孔隙体积的活性剂溶液可采出42%的二次残油。     

Thermophysical interface properties of crude oil and aqueous solution containing sulfate anions: experimental and modeling approaches

Abstract

Sulfate anion is well-known for being one of the most active agents to be injected into the oil reservoirs and being capable of not only altering the interfacial properties of crude oil but also enhancing the water solution properties in oil recovery. In the current study, the effects of temperature and pressure were studied on interfacial tension (IFT) as well as the adsorption behavior of two different solutions containing sulfate anion using experimental measurements and modeling approaches. Although it was expected that IFT values of the studied systems might decrease as temperature increased due to the improvement in the molecule mobility and solubility of crude oil in water, which consequently might lead to the reduction in its free energy, the reverse trend was observed. The measured dynamic IFT values and adsorption behavior revealed that surface excess concentration of natural surfactants (Г_NS) can be considered as the most effective parameter on interpreting IFT behavior as a function of temperature.     

The Effect of Alkali and Surfactant on Polymer Molecular Structure

Abstract

With the technical development of enhanced oil recovery (EOR), the alkali/surfactant/polymer (ASP) compound flooding technique has been the necessary choice in Daqing oilfield. Compared to average polymer flooding, ASP compound solution decreases the interfacial tension (IFT) between water and crude oil; however, the viscosity and viscoelasticity of ASP solution were performed by surfactant and alkali, both of which could affect the polymer moleculal structure and the oil recovery of ASP flooding. Considering practical requirements in oilfield development, much effort has been focused on the effect of alkali and surfactants on polymer solution by laboratory experiment and theoretical analysis. The results indicate that alkali and surfactants cause the interfacial tension decrease; at the same time, the molecular structure of the polymer is changed and the viscosity and viscoelasticity of polymer solutions are decreased. In addition, alkali neutralizes with negative ion on polymer molecular and causes the polymer molecular chains to curl up, forming a “band” molecular structure. Those actions could make viscoelastic behavior and rheological property of ASP solution weak.     

STUDYING THE INTERACTIONS BETWEEN AN ARABIAN HEAVY CRUDE OIL AND ALKALINE SOLUTIONS

An experimental study to examine the effectiveness of alkaline flooding for the recovery of an Arabian heavy crude oil is presented. The interfacial tension (IFT) behavior of crude oil/alkali systems over a wide range of parameters (pressure, temperature, alkali concentration and time) was studied. These alkaline reagents react with the acidic species in crude oil to form surface-active soaps in-situ. This leads to a lowering of interfacial tension (IFT) and subsequently the mobilization of residual oil. The equilibrium IFTs obtained through alkaline flooding are compared with the IFTs when a synthetic surfactant (dodecyl benzene sulfonic acid sodium salt) is used in EOR recovery. A mathematical model representing the complete chemistry of the transient process is also presented. The model consists of a set of differential equations describing reactions, diffusion, and adsorption at the oil/alkaline solution interface. The kinetic parameters in the model are obtained through a differential algebraic optimization technique. The concentration of the surface active species are related to the measured IFTs through an independent step that is based on isolating the surface active species formed by the reaction between the acids in the crude oil and the alkaline solution. A sensitivity analysis using the model is carried out to study the effect of surface potential and alkaline concentration on the transient interfacial tensions.     

A lysine amino acid-based surfactant: Application in enhanced oil recovery

Surfactants can play major role in increasing oil recovery factor through interfacial tension reduction. In the present study, a new synthetic method was used to prepare (S)-2-amino-6-dodecanamidohexanoic acid, an amino acid–based surfactant then it was applied as an oil recovery agent for the first time. The structure of this surfactant was studied using FTIR and ¹H NMR spectroscopy. The critical micelle concentration was found to be value is 0.4–0.5 wt% using surfactant solution conductivity, pH, and IFT methods. A 56.50% reduction of IFT was recorded using this environmentally friendly surfactant.     

碱／表面活性剂复合驱油体系与胜利孤东原油间协同效应的研究

考察了碱／非离子表面活性剂ＯＰ１０＋石油磺酸盐Ｃｙ体系与胜利孤东原油及萃取其酸性组分后的剩余油间的动态界面张力特性，发现复合驱油体系中的外加表面活性剂、碱与原油原位生成的表面活性物质之间存在明显的协同效应。这种协同效应对低离子强度下短时间内的界面张力影响较大；外加表面活性剂对高离子强度下长时间的界面张力影响较大。动态界面张力的最低值与界面上各表面活性物质的浓度和比值有着十分重要的关系     

Evaluation of interfacial tension between ASP solution and crude oil from B oil field

The interfacial tension (IFT) between alkali-surfactant-polymer (ASP) solution and crude oil is an important parameter for evaluating the feasibility of the ASP flooding for an oil field. The IFT between six series of ASP solution and crude oil from B oil field were measured at 65°C. Each series of ASP solution was composed of NaOH or Na₂CO₃, one of the three kinds of surfactants (S1, S2, and S3), and polymer FT60. The concentration of FT60 and surfactant were 1500 and 2000 mg/L, respectively. The research results show that the IFT between ASP solution and crude oil is ultra-low in the NaOH-FT60-S2 series and NaOH-FT60-S3 series and the best concentration of NaOH is 4000 mg/L and 8000 mg/L, respectively. NaOH-FT60-S2 series is more suitable for B oil field. The IFT between ASP solution and crude oil is ultra-low in the Na₂CO₃-FT60-S2 series and the best concentration of Na₂CO₃ is 4000 mg/L.     

Effect of active species in crude oil on the interfacial tension behavior of alkali/synthetic surfactants/crude oil systems

The effect of active species present in crude oil on the interfacial tension （IFT） behavior of alkali/synthetic surfactants/crude oil systems was studied. The system consisted of heavy alkyl benzene sulfonate, sodium chloride, sodium hydrate and Daqing crude oil. Experimental results indicated that active species would diffuse from oil/aqueous interface to aqueous phase and finally an equilibrium could be reached in the system with increasing contact time. Moreover, the minimum IFT and equilibrium IFT values increased with increasing contact time and a linear relationship existed between dynamic IFT and f^-1/2 when IFT value approaching the minimum and after the minimum IFT was reached. This indicated that the dynamic IFT-time behavior was diffusion controlled. The oil and aqueous phases were analyzed by infrared （IR） spectroscopy. IR spectra of oil and aqueous phases illustrated that the content of active species in the oil phase decreased, but the content of active species in the aqueous phase increased after alkali reacted with crude oil. This indicated that the active species present in oil played an important role in reducing IFT.     

利用微生物大幅度改善化学驱效果

针对大庆油田原油酸值低、应用三元复合驱难度大等特点,筛选了两株具有良好的产酸、产表面活性剂和改善原油物性的菌种,经鉴定分别为短短芽孢杆菌和蜡状芽孢杆菌。这两株菌可以降解原油中重质成分,尤其是高碳链(C₂₀以上)饱和烃,产生大量的胞外有机酸,可使原油酸值平均升高10倍以上。在发酵液中代谢产生混合酯类生物表面活性剂和低分子量有机酸、醇。微生物作用原油后,产生的有机酸在碱性条件下能与合成表面活性剂产生很好的协同作用,使微生物作用后原油与现有三元复合体系形成更低的界面张力,平均比未作用原油体系界面张力降低一个数量级,达到10^-4mN/m数量级。室内天然岩心驱油实验评价结果表明,微生物-三元复合驱结合可比单独三元复合驱驱油效率增加近10% OOIP。     

碱水驱油过程中界面张力变化规律

通过一系列试验，深入研究了碱驱过程中界面张力的变化规律。在碱／原油萃取实验中发现，原油被碱萃取后仍存在界面活性，萃取对界面张力最低值影响不大，使界面张力平衡值升高；低酸值原油被萃取后所受影响要大于高酸值的原油；已萃取原油后的碱液与新原油之间的界面张力将大幅度降低，可以使其最低值和平衡值都达到超低。此研究工作对碱驱的动态驱油机理有了更进一步的认识，所获得的结果对化学驱配方的筛选及机理研究具有指导意义     

Wettability Modification of Fractured Carbonates Using Sodium Metaborate Part II: History Match Results and Sensitivity Simulations

Abstract

Chemical-based wettability modification has become important for the worldwide abundance of fractured carbonates with the potential to enhance water imbibition to expel more oil from a matrix to the fractures. A systematic experimental and modeling approach on the combined benefit of wettability alteration for enhanced water imbibition and interfacial tension reduction is presented. Brine, alkali, and alkali–surfactant solutions are injected sequentially to improve oil recovery from a fractured mixed-wet carbonate core. The experiment was successfully modeled with a 3D chemical flooding reservoir simulator with wettability alteration capability. Part I discussed the laboratory results and presented the modeling approach and the waterflood history match results. The history match procedure and results for wettability modification using an alkali agent and interfacial tension (IFT) reduction with surfactant are discussed in this article. Sensitivity simulations to some key parameters are also presented.     

有机碱三元复合驱体系与正构烷烃间的界面张力

为明确有机碱、表面活性剂、聚合物三者之间的协同效应,采用旋转滴法研究了有机碱三元复合驱体系与正构烷烃间的界面张力。研究结果表明,非离子表面活性剂烷醇酰胺6501能够有效降低正癸烷油水间的界面张力,浓度为2.0 g/L时6501溶液与正癸烷间的界面张力稳态值为10-1m N/m;有机碱乙醇胺或二乙醇胺的加入可以进一步将体系与正癸烷间的界面张力降至10-2m N/m,这主要是由于有机碱能够影响烷醇酰胺的溶解性及其在界面上的分子排列,乙醇胺降低界面张力的能力大于二乙醇胺;聚合物类型对有机碱三元复合体系与正癸烷间的界面张力有较大影响,加入水溶性聚合物后的有机碱三元体系与正癸烷间的界面张力可降至10-3m N/m,而加入疏水缔合聚合物后的有机碱三元体系与正癸烷间界面张力瞬时值升高,稳态值变化不大,保持在10-1m N/m数量级。     

Interfacial Interactions Between Crude Oil and CO2 Under Reservoir Conditions

Abstract

In this paper, an experimental technique was developed to study the interfacial interactions between crude oil and CO₂ under reservoir conditions. By using the axisymmetric drop shape analysis (ADSA) for the pendant drop case, this new technique makes it possible to measure the interfacial tensions (IFTs) between crude oil and solvents, such as CO₂, at high pressures and elevated temperatures. The major component of this experimental setup is a see-through windowed high-pressure cell. In this study, the IFT of the crude-oil–CO₂ system was measured as a function of pressure at two fixed temperatures. It was found that, due to mutual interfacial interactions between crude oil and CO₂, their dynamic IFT gradually reduces to a constant value, i.e., the equilibrium IFT. The major interfacial interactions observed in this study include light-ends extraction and initial turbulent mixing. At T = 58°C, the equilibrium IFT reaches 1–2 dyne/cm when P ≥ 13.362 MPa, and only partial miscibility is achieved even up to P = 28.310 MPa. Thus, this experimental study shows that only partial miscibility can be obtained in most CO₂ flooding reservoirs. In addition, it is expected that the observed light-ends extraction and initial turbulent mixing phenomena may have significant effects on ultimate oil recovery and long-term CO₂ sequestration.     

Detection and Reuse of the Produced Chemicals in Chemical Enhanced Oil Recovery Operations

Abstract

The alkaline-surfactant-polymer (ASP) floods have been increasingly applied in the oil fields because of their high ultimate oil recovery. However, a major technical challenge is how to reduce the amount and the cost of chemicals used so that ASP floods can become cost-effective as well. On the other hand, field applications show that the chemical concentrations remain relatively high in the produced liquids of ASP floods. Therefore, successful detection and reuse of these produced chemicals can substantially reduce their capital cost and environmental impact. In this article, several experimental methods are developed to detect each chemical and quantify its concentration in the produced liquids. Also re-injection of the produced chemicals is conducted to further enhance oil recovery. First, the respective interactions of alkali, surfactant, and polymer with the oil-brine-sand system are studied. Second, the interfacial tension (IFT) is measured as a function of alkaline concentration by using the axisymmetric drop shape analysis technique for the pendant drop case. In addition, the synergistic effects of alkali and surfactant on reducing the IFT are studied. Third, coreflood tests are performed for alkaline, surfactant, alkaline-surfactant, polymer, and ASP floods to determine their respective tertiary oil recovery. Hence, how each chemical contributes to enhanced oil recovery is better understood. Fourth, the produced chemical concentrations are measured and compared with their injected concentrations to determine the potential of reusing these chemicals in practice. Finally, the follow-up coreflood tests are conducted by re-injecting the produced liquids into a new sand pack or Berea core. The re-injection coreflood test results show that the produced chemicals can be reused to effectively enhance oil recovery.     

Evaluation of Interfacial Tension Between Zahra Oil and ASP Solution

Alkaline-surfactant-polymer (ASP) flooding has been proved to be an effective enhanced oil recovery (EOR) method. Reduction of interfacial tension (IFT) between crude oil and ASP solution is the main mechanism in ASP flooding. Evaluating IFT between crude oil and ASP solution is a key parameter for ASP flooding in laboratory experiments or field projects. In order to obtain good result of ASP flooding in the reservoir in Zahra field, the influence of the concentration of Na₂CO₃ on IFT between Zahra crude oil and ASP solution with three different surfactants, BHJC, SS-231, and SS-233, was researched. IFT was measured with surface tension meter SVT20N, Dataphysics Co. Germany, at 72°C. For the view of IFT result anionic surfactant BHJC is more suitable for the Zahra oil field. This research is helpful for practical application of ASP flooding in Zahra oil field.     

欢喜岭油田欢50块高温油藏提高采收率方法研究

欢喜岭油田欢５０块高温油藏室内提高原油采收率实验结果证明，欢５０块原油／（碱＋表面活性剂）体系的界面张力随温度的升高而降低。可利用界面张力与温度关系曲线外推，获得不易测定的较高温度下界面张力值，由于欢５０块油藏温度很高，表面活性剂的热稳定性成为化学驱成功与否的关键，试验证明，含盐度是影响表面活性剂热稳定性的主要因素之一，配方１．５％Ｎａ２ＣＯ３＋０．４％ＬＨ可满足高温条件下欢５０块油藏原油低张力驱     

STABILITY AND RHEOLOGY OF HEAVY CRUDE OIL-IN-WATER EMULSION STABILIZED BY AN ANIONIC- NONIONIC SURFACTANT MIXTURE

ABSTRACT

The stability and rheology of an Egyptian Heavy crude oil-in-water emulsions stabilized by an anionic (TDS) and a nonionic (NPE) surfactants individually or in a mixture have been studied. The study reveals that, the viscosity of the crude oil decreases when it is emulsified with water in the form of an oil-in-water type of emulsion. The stability of the oil-in-water emulsion increases as the surfactant concentration and speed of mixing of the emulsion increases. Fresh water and synthetic formation water have been used to study the effect of aqueous phase salinity on the stability and viscosity of the emulsion. Surfactant dissolved in synthetic formation water has been utilized to find out the possibility of injecting the surfactant into a well bore to effect emulsification in the pump or tubing for enhancing the production of heavy crude oils as oil-in-water emulsion. The study revealed that, the viscosity of the emulsion containing fresh water is always less than that containing formation water, these findings have been correlated with the crude oil/water interracial tension (IFT) measurements The decreased IFT value results in a decrease in the average particle size of the dispersed crude oil leading     

复合驱油体系与孤东油田馆5^2^＋^3层原油间的界面张力

本文报导了用于孤东油田馆5~(2+3)层复合驱油试验的ASP体系与原油间界面张力的研究结果。在ASP复合驱油体系中,碱A和表面活性剂S在降低界面张力上有协同效应,聚合物P的影响很小。在单一A和A+S体系中最佳碱浓度为0.2％和1.5％(Na_2CO_3)。1.5％Na_2CO_3+0.4％OP-10体系有最佳界面特性。     

PRODUCING ULTRALOW INTERFACIAL TENSION AT THE OIL/WATER INTERFACE

ABSTRACT

In view of the world-wide shortage of petroleum and the fact that a large amount of residual oil will remain in the reservoir after the primary recovery and water flooding stages, the use of Enhanced Oil Recovery (EOR) methods to recover as much as possible of this residual oil has become increasingly important worldwide. The predominant and most promising EOR technique is the micellar-polymer flooding process which uses a surface active agent (a surfactant) to decrease interfacial tension and hence allows oil to freely move from its original location through the porous media. The purpose of this paper is to present an experimental study of the factors affecting the equilibrium interfacial tension (IFT) at the oil/water interface. A large number of experiments was conducted to study the variations of IFT as a function of many parameters including reservoir temperature, pressure, surfactant concentration, and salinity. An Arabian heavy crude oil was used in the analysis along with three different synthetic surfactants and two formation waters. The pendent drop technique enhanced by video imaging was employed for measuring IFT. It was found that for the ranges of variables considered in this study, IFT decreases with temperature and salinity, increases with pressure, and decreases exponentially with surfactant concentration.