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.     

Investigation of non-Newtonian flow characterization and rheology of heavy crude oil

The heavy crude oil exhibits a non-Newtonian shear thinning behavior over the examined shear rate. The viscosity of the heavy crude oil decreases about 15.6% when the temperature increased from 30 to 60°C. Heavy crude oil was blended with the aqueous solution of surfactant and saline water in different volumetric proportions of NaCl, and Na₂CO₃ solution mixtures. The addition of 50% of the mixture to the heavy crude oil causes a strong reduction in the viscosity, about 67.5% at 60°C. The heavy crude oil fits the Power law model since it has the lowest average absolute percent error of 0.0291. The flow behavior index of the heavy crude oil reaches a value of 0.9305 at a temperature of 30°C and it increases to 0.9373 when the temperature raises 60°C, while the consistence coefficient decreases from 2.8811 to 2.3558.     

Alkaline Surfactant Polymer Formulation for Carbonate Reservoirs

Abstract

This paper presents a systematic study to investigate the applicability of alkaline-surfactant-polymer (ASP) process as an enhanced oil recovery method to Saudi Arabian carbonate reservoirs. Several alkalis were first screened to test their compatibility with the injected sea water that has large quantities of divalent ions. Then surfactant-polymer, alkali-surfactant, and alkali-surfactant-polymer interactions at the reservoir temperature (90^○C) were investigated. Static adsorption of surfactant on reservoir carbonate rocks were also investigated at the same temperature. Interfacial tension (IFT) measurements were made between the slugs formulated and crude oil from the same reservoir. Two surfactants were tested, Triton X-102 and Ethoxylated sulfonate (Dodiflood B1083), and the polymer tested was FLOCON 4800C.

The results of the compatibility tests showed that the ASP slug has to be prepared using softened seawater and be protected by a pre- and after-flush softening seawater slugs. B1083 surfactant was found to be a promising candidate surfactant for the adverse conditions of the Saudi Arabian carbonate reservoir. A combination of NaHCO₃ and Na₂CO₃ was found to significantly reduce the adsorption level of B1083 surfactant on carbonate rock at low surfactant concentrations ( < 1% by wt.). This is very desirable for formulation of a cost-effective ASP slug.     

Experimental investigation of interfacial tension and oil swelling for asphaltenic crude oil/carbonated water system

The phenomenon of oil swelling at the oil-carbonated water (CW) system could be an important mechanism during the water alternating gas (WAG) injection process. Nevertheless, the study of the main mechanisms during water flooding (WF) is a complex topic that has not been well revealed so far, especially for asphaltenic crude oil (ACO) systems. Hence, the main goal of this experimental work is to determine the influence of carbon dioxide (CO₂) within the water phase in the interfacial tension (IFT) between water and crude oil for an extensive range of pressures between 400 psi and 2000 psi (i.e. 2.76–13.79 MPa), under two temperatures of 313.15 and 323.15 K (i.e. 40 and 50 °C) by axisymmetric drop shape analysis (ADSA) method. The experimental results demonstrate that the water/ CW and crude oil IFTs decline with time. The value of dynamic IFT (DIFT) between CW and crude oil decreased about 6 mN/m in comparison with the oil–water DIFT. As a result of the CO₂ solubility, the crude oil droplet swells with increasing pressure. When the temperature rises, the effects of increasing entropy phenomena and decline of liquids density is dominant compared to the solubility of CO₂. Thus, the volume of oil droplet increases with temperature, unexpectedly. In addition, as thetemperature increases the water/CW-Oil IFT is slightly reduced over a wide range of pressure evaluated. Nevertheless, there is a slight increase as the pressure increases for the water–oil system. According to the predicted results, interfacial tension of the CW-oil system declines with increasing pressure until the solubility of CO₂ is reached to a maximum value and then approximately remains changeless.     

Evaluation of a new alkaline/microbe/polymer flooding system for enhancing heavy oil recovery

The new alkaline/microbe/polymer (AMP) flooding system was first constructed and evaluated for enhancing oil recovery. The system is composed of 0.3?wt% Na₂CO₃, 2?wt% microbial cultures and 0.2?wt% polymer. Compared with the conventional alkaline/surfactant/polymer (ASP) system, the AMP system exhibits identical displacement properties. Chromatography analysis reveals crude oil is not negatively affected by the microbes in AMP system. Further comparative core flooding experiments using the AMP and ASP systems demonstrate that the AMP system possesses greater potential for enhancing heavy oil recovery, which shows the characteristic of two-stage additional oil increment with total additional oil recovery of 17.11%–19.91%.     

Synthesis,interface activity and oil flooding experiment with an authentic sandstone microscopic model of cationic gemini surfactant

In this work, a series of cationic gemini surfactants with different hydrophobic tails were prepared and characterized by element analysis, IR spectra, and ¹H NMR spectra. The influencing factors of physic-chemical properties of these surfactants were carefully studied. The critical micelle concentration (CMC) of all the surfactants ranged from 3.87 × 10^?4 mol L^?1 to 8.97 × 10^?4 mol L^?1 and the values (γ_cmc) also ranged from 28.62 mN m^?1 to 34.07 mN m^?1 at CMC level by surface tension experiments. The consequences of the oil/water interface tension experiments indicated that all these prepared surfactants could lower oil/water interface tension to ultra-low with the combination of Na₂CO₃. C₁₂-2-C₁₂, and C₁₄-2-C₁₄ were chosen as the representative to evaluate the displacement efficiency in the oil flooding experiments using authentic sandstone microscopic model. The results showed that these surfactants could effectively improve the displacement efficiency by 10–20%.     

Na+质量浓度对三元复合体系的影响

 阳离子对三元复合体系(表面活性剂+聚合物+NaOH,alkaline/surfactant/polymer,简称ASP)的性能影响较大。在纯水配制的三元复合体系中,利用NaOH和NaCl的质量分数来调节其中Na⁺的质量浓度,考察三元复合体系中Na⁺质量浓度对体系黏度及其与原油之间油-水界面张力的影响。结果表明,三元复合体系中Na⁺质量浓度达到较高值时,三元复合体系黏度就不再变化。在三元复合体系中,无论是NaOH质量分数高而NaCl质量分数低,还是NaCl质量分数高而NaOH质量分数低,只要体系中Na⁺质量浓度在5200~7700 mg/L,就能与原油形成超低油 水界面张力,这是三元复合体系Na⁺质量浓度的变化导致表面活性剂分子在油-水界面上的吸附发生变化的结果。     

复合体系超低界面张力和碱在驱油过程中的实际作用

以物理模拟实验结果为依据并结合理论分析发现,在实际油藏的驱油过程中,础活性剂／聚合物（ASP）复合体系与原油的超低界面张力对于启动残余油滴和降低毛管阻力的作用均比以往所推断的要小;为使油／水界面张力达到超低而加入的大量强碱,将导致储层矿物的溶蚀、地层和井筒的严重结垢以及产出液的深度乳化,这对于复合驱的总体效果和效益都是不利的。因此,对于复合体系超低界面张力和碱在驱油过程中的实际作用研究应予以客观的评价,对于非超低界面张力体系驱油实际效果的研究应引起足够的重视.     

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.     

An Environment-Friendly Alkaline Solution for Enhanced Oil Recovery

Abstract

The injection of alkali and alkali/polymer solutions is a well-known enhanced oil recovery technique. This article demonstrates how wood ash can be used as a source of low cost alkali instead of synthetic alkali that is also environmentally friendly. From the experimental studies, it is found that the pH value of 6% wood ash extracted solution is very close to the pH value of 0.5% synthetic NaOH or of 0.75% Na₂SiO₃ solution. A preliminary microscopic study of oil/oil droplets interaction in natural alkaline solution was carried out in order to understand the oil/water interface changes with time and its effect on oil/oil droplet coalescence. Also, interfacial tension (IFT) was measured for both synthetic and natural alkaline solutions. The IFT values in the presence of acidic crude oil show comparable results.     

Modeling crude oil gasification

Abstract

The characteristics of CO₂-gasification of crude oil under steady-state condition were studied using a simulator. The model was developed using the minimization Gibbs free energy minimization. The effects of reactor temperature and CO₂/crude oil ratio on gas composition and lower heating value (LHV) of the produced syngas were investigated. As a result, the maximum LHV was obtained at a CO₂/crude oil ratio of 0.1 and gasification temperature of 800?°C.     

Study on emulsification of crude oil in water using emulsan biosurfactant for pipeline transportation

In this work, an experimental investigation on removing crude oil from a stainless steel tube using a biosurfactant such as emulsan was studied. The emulsan used in this study was produced by Acinetobacter calcoaceticus PTCC1318. The produced emulsan was able to reduce the surface and interfacial tension of water to 24 mN/m and 3 mN/m, respectively. Also influence of water- oil ratio on emulsifying property was studied. The results showed at CMC concentration, emulsification index (E₂₄) of emulsions decreased with increasing water- oil ratio. At 25°C, 30 mg/L, with a water–oil ratio of 1:2, produced emulsan formed an excellent emulsification of crude oil about 98%. Cleaning parameters tested included washing time and flow rate. It also demonstrated that the emulsan is useful for the tube cleaning with removal percentages of 100% at the room temperature, depending on the washing conditions.     

油水乳化能力对油膜驱替的影响

为深化油膜驱替机理认识,开展油膜驱替实验。以综合反映乳化速度和乳化量的乳化系数量化表征油水乳化能力。针对实验用低黏和中黏原油,筛选出具有强乳化能力-超低界面张力、强乳化能力-低界面张力和弱乳化能力-超低界面张力3种不同性质的驱油剂,并进行玻璃棒束油膜驱替实验。实验结果表明,对于低黏原油,乳化系数分别为0.667和0.706的强乳化能力驱油剂,不论其界面张力是否达到超低,其驱替效率都约为90%,而乳化系数为0.244的弱乳化能力-超低界面张力驱油剂的驱替效率不足70%;对于中黏原油,乳化系数分别为0.534和0.602的强乳化能力驱油剂,不论其界面张力是否达到超低,其驱替效率都约为83%,而乳化系数为0.258的弱乳化能力-超低界面张力驱油剂的驱替效率不足65%。研究结果表明,油水乳化能力是对油膜驱替起决定作用的性能指标。     

Use of oil-soluble surfactant to reduce minimum miscibility pressure

In some low-permeable reservoirs, the miscibility pressure is far higher than the formation pressure, which makes it not feasible to have a CO₂ miscible displacement. In this study, an oil-soluble surfactant, CAE, was designed and synthesized to reduce interfacial tension (IFT) and CO₂-oil minimum miscible pressure (MMP), making it possible to release miscible displacement increasing oil recover. Experiment results showed that oil soluble surfactant can be dissolved in supercritical CO₂ but not soluble in water. It is also found that the CAE preslug displacement has the higher displacement efficiency than displacement with the CAE dissolved in CO₂. Based on a series of CAE preslug displacement experiments with varying CAE concentrations, the optimal injection concentration of CAE is 0.2%. Moreover the MMP determined under the CAE concentration of 0.2% is 6.1 MPa lower than that of pure CO₂ displacement. It reduces the MMP more than liquid gas preslug displacement (3.2 MPa) when the same volume of liquid gas is used with the CAE used in CAE preslug displacement test.     

枯草芽孢杆菌提高原油采收率的物模驱油实验

针对目前常规采油开采技术的限制和原油采收率较低等问题,本研究采用单因素法对一株从油污中分离的枯草芽孢杆菌(Bacillus subtilis 32811)代谢产生物表面活性剂的发酵条件进行优化并进行微生物驱油实验。优化条件实验确定了以葡萄糖为唯一碳源,最佳的无机培养基配方(g/L):ρ(C_6H_(12)O_6)30.0,ρ(NH_4NO_3)1.0,ρ(KH_2PO_4)4.1,ρ(Na_2HPO_4·12H_2O)14.3,ρ(MgSO_4)0.096,ρ(CaCl_2)0.0008,ρ(FeSO_4)0.0011,ρ(C_(10)H_(16)N_2Na_2O_8)0.0015。发酵液表面张力从65mN/m降至25mN/m。通过微生物对原油降解的物模驱油实验,得出原油出现乳化及原油重质组分含量明显降低的结果。物模驱油实验中分别注入发酵液及先注入微生物再注入无机培养液能提高原油采收率26.1%和31.4%。说明枯草芽孢杆菌有利于提高剩余油的采收率,具有良好的应用前景。     

Physical Chemical Properties of Leachate in the Process of Improving Vanadium Leaching From Petroleum Coke: Part II

The effects of NaOH concentration, leaching time, temperature, Na molar ratio of NaOH and Na₂CO₃ and liquid to solid mass ratio on vanadium removal, and physical chemical properties of leachate were investigated. The optimum conditions were 10 g of petroleum coke, 20 mL of oxidation, 6:1 liquid to solid ratio, 150 g/L of NaOH concentration, 62 g/L of Na₂CO₃ concentration, and 95°C temperature. Physical chemical properties of leachate changed along with the parameters. The microstructures of petroleum coke before and after leaching were also analyzed by scanning electron microscope.     

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.     

Emulsification of Indian heavy crude oil using a novel surfactant for pipeline transportation

The most economical way to overcome flow assurance problems associated with transportation of heavy crude oil through offshore pipelines is by emulsifying it with water in the presence of a suitable surfactant.In this research,a novel surfactant,tri-triethanolamine monosunflower ester,was synthesized in the laboratory by extracting fatty acids present in sunflower(Helianthus annuus)oil.Synthesized surfactant was used to prepare oil-in-water emulsions of a heavy crude oil from the western oil field of India.After emulsification,a dramatic decrease in pour point as well as viscosity was observed.All the prepared emulsions were found to be flowing even at 1°C.The emulsion developed with 60%oil content and 2wt%surfactant showed a decrease in viscosity of 96%.The stability of the emulsion was investigated at different temperatures,and it was found to be highly stable.The effectiveness of surfactant in emulsifying the heavy oil in water was investigated by measuring the equilibrium interfacial tension(IFT)between the crude oil(diluted)and the aqueous phase along with zeta potential of emulsions.2wt%surfactant decreased IFT by almost nine times that of no surfactant.These results suggested that the synthesized surfactant may be used to prepare a stable oil-in-water emulsion for its transportation through offshore pipelines efficiently.     

Evaluation of Trace Metals and Physical Properties of Nigerian Crude Oil Saturate Fraction

Analyses of trace elements and physical properties of the saturate fraction of Nigerian crude oil were done in order to establish the characteristics that may aid the developmental processes of the natural resources. Crude oil samples were collected from three different oil fields in Niger-Delta area of Nigeria. The saturate fractions were eluted by column chromatography using n-hexane. The saturate fractions were investigated for functional groups using Fourier transform infrared spectrometry (FT–IR); the elemental concentrations were determined using Atomic absorption spectrometry, while the physical properties (flash point, ash content, refractive index, and color) were determined using standard analytical methods. The results revealed that the infrared spectra of the saturate fraction of the Nigerian crude oil showed mainly the presence of C-H(CH₃) and C-H(CH₂) functional groups, indicating high purity of the samples. The concentrations of the analyzed elements (Mn, Cu, Co, Zn, Fe, V, Cr, and Ni) in the saturate fraction were generally low compared to other fractions of Nigerian crude oil. This study revealed that Co has the highest mean concentration of 1.81 ± 0.36 mg/L, while Mn has the lowest mean concentration of 0.04 ± 0.02 mg/L. The t test values for the comparison of the elemental concentrations of Nigerian crude oil /saturate fraction and crude oil asphaltene/saturate fraction showed significant difference (except Mn) with respect to Nigerian crude oil /saturate fraction. The cluster analysis for the elements showed two groups, which are fairly well correlated indicating similar source and similar chemical affinity. The cross-plot analysis of the Nigerian crude oil and its saturate using elemental concentrations as the variables showed a strong positive inter element correlation since (R² = 0.71), establishing a relationship between the Nigerian crude oil and the saturate fraction. The color of the saturate fraction ranged from off-white to colorless. The results of analysis provide useful information on its conversion mechanism and environmental implications of the development of the fossil fuel deposit.     

Exploitation of fractured shale oil resources by cyclic CO2 injection

With shale oil reservoir pressure depletion and recovery of hydrocarbons from formations, the fracture apertures and conductivity are subject to reduction due to the interaction between stress effects and proppants. Suppose most of the proppants were concentrated in dominant fractures rather than sparsely allocated in the fracture network, the fracture conductivity would be less influenced by the induced stress effect. However, the merit of uniformly distributed proppants in the fracture network is that it increases the contact area for the injection gas with the shale matrix. In this paper, we address the question whether we should exploit or confine the fracture complexity for CO₂-EOR in shale oil reservoirs. Two proppant transport scenarios were simulated in this paper: Case 1—the proppant is uniformly distributed in the complex fracture system, propagating a partially propped or un-propped fracture network; Case 2—the proppant primarily settles in simple planar fractures. A series of sensitivity studies of the fracture conductivity were performed to investigate the conductivity requirements in order to more efficiently produce from the shale reservoirs. Our simulation results in this paper show the potential of CO₂ huff-n-puff to improve oil recovery in shale oil reservoirs. Simulation results indicate that the ultra-low permeability shales require an interconnected fracture network to maximize shale oil recovery in a reasonable time period. The well productivity of a fracture network with a conductivity of 4 mD ft achieves a better performance than that of planar fractures with an infinite conductivity. However, when the conductivity of fracture networks is inadequate, the planar fracture treatment design maybe a favorable choice. The available literature provides limited information on the relationship between fracture treatment design and the applicability of CO₂ huff-n-puff in very low permeability shale formations. Very limited field test or laboratory data are available on the investigation of conductivity requirements for cyclic CO₂ injection in shale oil reservoirs. In the context of CO₂ huff-n-puff EOR, the effect of fracture complexity on well productivity was examined by simulation approaches.