Rheological behavior of Algerian crude oil: effect of temperature and refined product

Abstract

The rheological behavior and its variation with temperature and refined product concentration of a crude oil sample coming from a quagmire of the separation station of Tin Fouye Tabankort oilfield/southern Algeria were investigated experimentally. The experiments were carried out at various temperatures (20, 30 and 50?°C) over the shear rate range of 0 to 700?s^?1 by using a controlled stress rheometer (AR 2000, TA Instrument). The results showed that the crude oil exhibit non-Newtonian of shear thinning behavior at low shear rate and Newtonian behavior at high shear rate and was adequately described by Casson and Herschel–Bulkley models. The rheological measurements through the steady flow test and viscoelastic behavior, including the storage modulus (G′), loss modulus (G″), and complex modulus (G*), has indicated that the rheological properties of the crude oil were greatly influenced by the temperature and the additive concentration.     

Rheological and physicochemical characterization of UAE crude oil

This study focuses on the rheological and physiochemical characterization of three samples of light crude oil and fuel oil from the United Arab Emirates. The dependence of density on temperature ranging from 20 to 200°C was determined. Also, the impact of temperature was investigated on viscosity, shear stress τ, shear rate, yield stress, and thixotropic behavior, and characterized by the Haake RheoStress. The exponential decrease of viscosity over temperature range was modeled using Arrhenius equation. The shear stress–viscosity data revealed that crude oil A solely exhibited Newtonian behavior while crude oils B and C and fuel oil followed the Herschel-Bulkley model.     

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.     

Rheological behaviour of crude oil: Effect of temperature and seawater

The effect of temperature and seawater on rheological behavior was investigated in this work for four samples of crude oil from Algerian Sahara. The Newtonian model was used to fit the shear stress dependence on the shear rate for temperature range between 20 and 100°C. The temperature increase leads to a decrease in the dynamic viscosity of crude oil. The temperature dependence of dynamic viscosity was fitted by the Walther equation. For crude oil emulsion, the Herschel-Bulkley model was used to fit the shear stress dependence on the shear rate for volume fraction of seawater between 30 and 70%. The increase in the volume fraction of seawater induces not only an increase in the yield stress and the consistency index of crude oil emulsions but also a decrease in the flow index of crude oil emulsions.     

Experimental investigation of the rheological behavior of algerian crude oils from the quagmires

In this work, the rheological behavior for three types of crude oil coming from different quagmires namely Amassak, Tamendjelt and Tin Fouye of the TFT sector (Tin Fouye Tabankort/South Algeria) has been experimentally investigated. A controlled stress rheometer (AR 2000, TA Instrument) was used throughout this investigation. The experimental measurements in terms of flow and dynamic tests were carried out at different temperatures during the shear rate over the range of 0–700?s^?1 and frequency range of 0.1–10?rad/s. The obtained results show that the viscosity and shear stress of the crude oils decreases about 53.30%, 58.80%, and 59% respectively, when the temperature increased from 10 to 20?°C. The yield stress required to flow of crude oils also decreased to 37.06%, 89.78%, and 77.53% respectively. The dynamic analysis of the crude oils by identifying of the storage modulus (G′) and the loss modulus (G″) has indicated that the rheological properties of crude oils were significantly temperature-dependent.     

Investigating the rheological behavior of Algerian crude oil stemming from station of separation (quagmire)

An experimental study was conducted to investigate the rheological behavior of Algerian crude oil stemming from station of separation (quagmire) of the Tin Fouye Tabankort sector (southern Algeria). The rheological measurements at different temperatures (20°C, 30°C and 50°C) were performed employing AR 2000 rheometer of TA-Instruments. Several parameters such as shear rate, the temperature and the presence of crude oil from another quagmire on the rheological properties have been studied. The experimental results show that the studied crude oil displays non-Newtonian shear thinning behavior at low values of shear rate and a Newtonian behavior at high values of shear rate, which can be best presented by the Casson model. The rheological examination tests (flow and dynamic mode (oscillation)) have shown that the rheological properties of the crude oil were significantly influenced by the temperature and the crude oil addition.     

Comparative studies of the rheological behavior and microstructural properties of emulsions (oil/distilled water phase) and (oil/Lias water phase)

Abstract

The rheological behavior of crude oil and their emulsions were investigated as a function of two water types (distilled water and the LIAS water). The focus of this work is to obtain more knowledge about the effect of LIAS water concentration, which used to maintain pressure and produced from production of crude oil in the oil fields Tin Fouye Tabankort-south Algeria, on the rheological properties of crude oil. The rheological parameters were measured by using AR-2000 rheometer at 15?°C under dynamic and shear testing conditions. The measured data were first classified into two groups for Newtonian and non-Newtonian fluids. Depends on the type and concentration of water, the non-Newtonian behavior was described in better way by the Casson, Power law and the Herschel–Bulkley models. The results indicated that the viscosity, the yield stress, the elastic modulus, (G′), the loss modulus, (G″), and the microstructure of the prepared emulsions not only varied with water concentration but also by water types.     

孤岛油田东区原油流变性研究

重质高粘原油在地层条件下表现为非线性渗流,其流变性测试结果对于指导其油藏的开发具有重要意义。对孤岛油田东区重质高粘原油渗流流变性进行了研究。结果表明,该区含气原油为假塑性流体,地层条件下非线性渗流显著;脱气原油粘弹性较弱;注水开发时,油水井间的水驱速度应控制在0．885m/d以内。     

An Experimental Study of Rheological Properties of Nigerian Waxy Crude Oil

Abstract

Nigerian crude oils are known for their good quality (low sulfur, high American Petroleum Institute gravity). However, similar to any other paraffinic-based crudes, most Nigerian crudes contain moderate to high contents of paraffinic waxes. These waxy crudes exhibit non-Newtonian flow behavior at temperatures below the cloud point because of wax crystallization. In order to accurately predict flowing and static temperature profiles, design waxy crude oil pipelines, evaluate flow interruption scenarios, and start up requirements in the handling of waxy crude oils, the effect of temperature and shear rate on the rheology of crude oils must be determined. This work presented some experimental results on the rheology of two waxy crude oils produced from different Nigerian oil fields. A Brookfield DV-III ultraprogrammable rheometer (Brookfield Engineering Laboratories, Middleboro, MA) was utilized. The temperature dependence of rheological properties and thixotropy of these crudes were investigated. The influence of some petroleum-based diluents to depress the wax appearance temperature (WAT), their effect on the thixotropic/yield pseudoplastic behavior of two Nigerian crudes were studied and it was observed that lower wax content crude has higher tendency to regain its cohesive lattice bonding (yield strength) when left undisturbed for some days at its gel point after agitation. The experimental results showed that the addition of petroleum-based diluents to the lower wax content crude oil leads to its lost some of its yield strength regaining capacity.     

绥中36-1原油性质及其生产的沥青的性能

中海绥中36—1原油为低硫环烷基原油，该原油具有密度大、粘度大、凝点低、酸值高、胶质含量高等特点，是生产优质道路沥青的适宜原料。利用该原油生产的道路沥青具有较大的延度，低温抗变形能力强，路面不易开裂，并且具有理想的流变性能，高温不易流淌，抗车辙能力强，抗老化性能好，按美国SHRP计划Superpave沥青胶结料试验规范评定其AH-70、AH-90道路沥青等级可分别达到PG64—22和PG64—28。     

Effect of ultrasonic irradiation on rheological properties of asphaltenic crude oils

In this work, the rheological changes of several crude oil samples exposed to ultrasonic waves for different time intervals in addition to the effect of temperature on viscosity behavior of heavy crude oils were investigated using a series of steady shear flow and oscillatory tests. The colloidal structural evolutions of flocs in oil samples were illustrated by analysis of the size distribution of flocculated asphaltene particles (confocal microscopy tests). The rheological investigations indicate that the ultrasonic irradiation dissolved heavy components in crude oil. After ultrasonic treatment, the Kouh-e-Mond crude oil was found to be pseudoplastic. In addition, confocal microscopy confirms that there was an optimum duration for ultrasonic irradiation, at which the viscosity and flocculation rate of asphaltenic crude oils reduced to the minimum values. The optimum was found to be approximately 40 min for the Kouh-e-Mond crude oil. Experimental results illustrate that the ultrasonic irradiation could disaggregate heavy colloid components in crude oil, and breakdown of asphaltene molecules would only occur in a specific time interval of irradiation. Also according to the temperature sweep test, the oil temperature rise caused by ultrasonic irradiation was not the main reason for rheological changes of the crude oil and this alteration may be due to physical and chemical phenomena induced by sonication in crude oil.     

CFD investigation on characteristics of heavy crude oil flow through a horizontal pipe

Transportation of heavy crude oil via pipelines possesses many technological issues that are inherently flow related. Accurate prediction of flow characteristics is an essential step for a reliable piping design of transporting the crude oil. A rheology-based Computational Fluid Dynamics (CFD) model of the Iraqi heavy crude oil flow through a horizontal pipe (1 m length of 3/4 in. inside diameter) was developed using the commercial software Ansys 15 Fluent. By using power law rheological model, the Iraqi heavy crude oil exhibits a non-Newtonian dilatant behavior over the examined shear rate range of 1–40 s⁻¹. The proposed axi-symmetric CFD model identifies velocity profile and generates values of friction factor, which are validated with experimental measurements. Additionally, wall shear stress and entrance length were numerically predicted and compared with well-established correlations from the literature for Non-Newtonian flow. Detailed results of the CFD model exhibited a reliable prediction of the characteristics of heavy crude oil flow.     

Modeling the viscoelasto-plastic behavior of waxy crude

Waxy crude oil exhibits complex rheological behavior below the pour point temperature, such as viscoelasticity, yield stress, and thixotropy, owing to the formation of a three-dimensional spongelike interlock network structure. This viscoelasto-thixotropic behavior is an important rheological behavior of waxy crude oils, determining the flow recovery and safe restart of crude oil pipelines. Up to now, the thixotropic models for waxy crude have been all viscoplastic models, without considering the viscoelastic part before the yield point. In this work, based on analyzing the variation of the elastic stress and viscous stress in the Mujumbar model, a new viscoelasto-plastic model is proposed, whose shear stress is separated into an elastic component and a viscous component. The elastic stress is the product of the shear modulus and elastic strain; the shear modulus is proportional to the structural parameter. For the elastic strain, we followed the line of Zhu and his coauthors and assumed that it may be expressed by an algebraic equation. The model is validated by stepwise shear rate tests and hysteresis loop tests on Daqing and Zhongyuan waxy crude. The results show that the model’s fitting and predictive capability is satisfactory.     

潍北高凝点原油降凝降黏剂的研制

实验室自制的三元共聚物AMV-22与EVA复配,添加SLA-107作助剂,制备适用于胜利油田潍北区块高凝点原油的降凝剂AMVES。实验考察了该降凝剂对原油的降凝降黏效果。DSC热分析结果表明,AMVES加量为1000 mg/L时,可使原油凝点从48℃降低到37℃,析蜡点降低2℃。流变性曲线表明原油的剪切稀释作用随温度升高显著增强,当剪切速率大于100 s^-1后黏度基本不变,降凝剂可以大幅降低启动原油的屈服应力。偏光显微镜图显示原油温度越低,蜡晶网状结构越致密,交联度强,黏度大,流动性差;加AMVES之后原油中蜡晶变为团簇状颗粒,原油的流动性增强。由此可见降凝剂AMVES作用于蜡晶使其三维网状结构破坏,从而有效降低原油凝点和黏度。     

Shear strengthening viscosity and shear-rate-dependent modulus model for a Shengli crude oil

The steady shear viscosity of a Shengli waxy crude oil at the temperature of 3°C to 4°C, higher than its gel point, was measured by using a parallel-plate rheometer, which shows a shear thickening behavior in the shear rate range of 10^?2–10^?1 s^?1. A spectrum model proposed in our previous work was modified here by considering the modulus change in the spectra, which could be caused by a shear-induced varying internal structure in the crude oil. The shear strengthening viscosity of the Shengli crude oil can be described well by the changing-spectrum viscosity model.     

Effective flow improving agents for waxy crude oil

The comb-like copolymer-polyhedral oligomeric silsesquioxane (POSS) nano-composite PPDs, including POA-POSS, POA-VA-POSS, POA-MA-POSS and POA-St-POSS, were first synthesized via in-situ reversible addition-fragmentation chain transfer (RAFT) polymerization and characterized by FT-IR, NMR and TGA methods. Subsequently, the effects of the nanocomposite PPDs on rheology of a waxy crude oil were studied. Results showed that POA-VA-POSS is the most efficient PPD among the nanocomposite PPDs, which can depress the pour point, gelation point, apparent viscosity and yield stress of the crude oil to the lowest. Associated with the microstructure of crude oil, the rheo-logical improving mechanisms of the copolymer-POSS nanocomposite PPDs are discussed.     

Experimental study and a proposed new approach for thermodynamic modeling of wax precipitation in crude oil using a PC-SAFT model

A powerful method is necessary for thermodynamic modeling of wax phase behavior in crude oils,such as the perturbed-chain statistical associating fluid theory(PC-SAFT).In this work,a new approach based on the wax appearance temperature of crude oil was proposed to estimate PC-SAFT parameters in thermodynamic modeling of wax precipitation from crude oil.The proposed approach was verified using experimental data obtained in this work and also with those reported in the literature.In order to compare the performance of the PC-SAFT model with previous models,the wax precipitation experimental data were correlated using previous models such as the solid solution model and multi-solid phase model.The results showed that the PC-SAFT model can correlate more accurately the wax precipitation experimental data of crude oil than the previous models,with an absolute average deviation less than 0.4 %.Also,a series of dynamic experiments were carried out to determine the rheological behavior of waxy crude oil in the absence and presence of a flow improver such as ethylene–vinyl acetate copolymer.It was found that the apparent viscosity of waxy crude oil decreased with increasing shear rate.Also,the results showed that the performance of flow improver was dependent on its molecular weight.     

Comparative Studies on Synthetic and Naturally Extracted Surfactant for Improving Rheology of Heavy Crude Oil

Effect of surfactants on rheological properties of heavy crude oil obtained from Mehsana Asset, Gujarat, India, were studied. Studies on effectiveness towards flow behavior were made using a surfactant extracted from a tropical Indian plant Madhuca longifolia (Mahua) and nonionic surfactant Brij-30 considering various contributing parameters such as temperature, concentration, and shear rate. Tests were performed at controlled shear rate. At 25°C, 2000 ppm Mahua and Brij-30 addition reduced viscosity of crude oil by 48% and 52%, respectively. Complex and viscous modulus of crude oil decreased significantly due to addition of both the surfactants. FTIR studies of crude-surfactant mixture showed remarkable decrease in concentration of viscosity enhancing groups such as alkanes, alcoholic, and acidic groups indicating the effectiveness of both the surfactants. Naturally extracted surfactant may be used as flow improver for transporting heavy crude oil.     

牙哈原油综合评价

介绍了对牙哈原油进行的综合评价。结果表明:该原油的特点是密度小(849.9 kg/m3),轻质油收率高,且质量好,初馏点～145℃馏分是理想的重整原料,初馏点～180℃是较理想的汽油调合组分,也是优良的乙烯裂解原料,初馏点～350℃收率72.17%,加工时应严格控制比例,比例过高,常压塔的汽相负荷大,会影响常减压装置的稳定操作和安全生产。牙哈原油重整原料的收率较高,砷、氯,硫含量低,腐蚀合格。牙哈原油芳烃潜含量较高,重整加工时芳烃收率指数高达73.51%,是较理想的重整原料。牙哈原油喷气燃料组分加工前应针对碱性氮小的情况采取白土精制,保证航空煤油颜色的稳定性。240～300℃,300～350℃两段组分是较理想的柴油馏分,但必须经过加氢或碱洗精制,240～300℃是调合低凝柴油的优质组分。其减压蜡油作为润滑油馏分粘度指数大,黏温性能好,酸值小,芳烃含量较低,适合作生产高黏度指数润滑油的基础油,也是较好的催化裂解原料,大于520℃的减压渣油收率低,应与其他渣油掺炼,没有单独深加工的必要。     

Viscosity Behavior of Foamy Oil: Experimental Study and Modeling

Abstract

Heavy oil cold production is faced with the foamy oil phenomenon: while extracted, a heavy crude oil is submitted to a depletion that can induce the formation of dispersed gas bubbles and makes it appear as a foam. This situation results in a change of the flow properties of the live oil that is still debated: correlations predict a decrease or an increase in the gas bubble-dispersed oil viscosity with the gas volume fraction. We attempted to improve the understanding of the foamy oil behavior through rheological measurements. A live oil was depleted inside the pressure cell of a controlled stress rheometer. The occurrence of bubbles was checked and visualized with x-ray scanning experiments. Viscosity was continuously measured using oscillatory and continuous tests. This particular experimental approach allowed us to successfully study the rheological behavior of a foamy oil in relationship with the two main parameters, which are the composition and the viscosity of the crude oils. A theoretical model describing the viscosity of a foamy oil has been established. It takes into account both first-order kinetics of appearance and release of bubbles in oil and a basic suspension model. Results from this model are in agreement with experimental data obtained from different heavy crude oils.