Evaluation on the effects of wax inhibitor and optimization of operating parameters for wax deposition in Malaysian crude oil

The complex phenomenon of wax deposition subject to thermal gradient in crude oil is one of the biggest challenges in petroleum industry. In this comparative study, two inhibitors which were poly(ethylene-co-vinyl acetate) (EVA) and xylene were investigated in terms of rate of wax deposition in Malaysian crude oil using one-factor-at-a-time (OFAT) approach and cold finger methods. Stirring rate and cold finger temperature were optimized using response surface methodology (RSM) after being investigated using OFAT. It can be concluded that EVA had higher capability of reducing wax in two different conditions where the minimum point of wax reduction was found at 400 rpm with 63.5% paraffin inhibition efficiency (PIE) and 10°C with 64.7% of PIE. The amount of waxes collected for each parameter were 0.35 and 0.49 g, respectively. To minimize the wax deposit amount, RSM approach was applied using rotatable central composite design (CCD). The result shows that the amount of wax deposit decreased significantly with the increase of temperature and the stirring rate which were set at 400 rpm and 19°C, rescpectively. The amount of wax deposit was successfully reduced to the minimum value of 0.0095 g after the optimization.     

Screening of factor influencing wax deposition using full factorial experimental design

The purpose of this work was to study the rate of wax deposition of Malaysian crude oil using full factorial design. Important parameters affecting wax deposition such as experimental duration, speed of rotation, cold finger temperature, and inhibitor concentration were investigated. The individual effects of variables and its interaction effects towards the dependent variables were studied. Wax deposit is the dependent variable. The results of the study showed that less wax deposit was obtained (0.75 g) with optimal conditions of initial poly(ethylene-co-vinyl acetate) concentration of 5000 ppm, 2 h duration without rotation speed, and 15°C cold finger temperature. These results demonstrate that cold finger temperature and experimental duration could be the main factors affecting wax deposit formation. The minimum amount of wax deposit obtained could reduce the chances of blocked pipelines; however, crude oil production increased. Nevertheless, Design Expert can be a valuable tool to quantify and detect the special relationships of two of more factors known as interactions regarding how they factors could affect a process, especially for screening purpose.     

防蜡剂SZ－3及其性能特点

为了解决胜利桩西油田高含蜡原油开采中的严重结蜡问题，研制了ＳＺ－３防蜡剂。该剂为以ＥＶＡ甲苯溶液为内相，水为外相，含有油溶性和水溶性非离子表面活性剂和低分子醇的Ｏ／Ｗ乳状液，从油套环空投入采油井井底，防蜡效果良好。本文介绍了该剂的研制、配方、室内性能测定和现场试验简况。     

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.     

Pour Point Depressant of Fuel Oil Using Non-ionic Surfactants

Paraffin wax deposition from fuel oil at low temperature is one of the serious and long-standing problems in petroleum industry. The addition of pour point depressants (PPD) has been proved to be an efficient way to inhibit wax deposition. The influence of PPD on wax precipitation at low temperature was investigated. A different ethoxylated nonionic surfactants were prepared by reacting natural fatty acids (myristic acid and palmitic acid) with polyethylene glycol of different molecular weight. The synthesized nonionic surfactants were confirmed by NMR and FTIR spectroscopy. The surface properties of the synthesized surfactants, including the critical micelle concentration, effectiveness (π_CMC), maximum surface excess (Г_max), and minimum surface area (A_min) were determined. The efficiency of ethoxylated nonionic surfactants was evaluated as cloud and pour point depressant for fuel oil was discussed. The results indicate that C₁₆E₇ surfactant posse's good cloud and pour point depressing performance. The effect of additive type and compatibility additive with natural wax dispersant on the wax crystallization behavior at low (0°C) was evaluated. Photomicrographs showed that wax morphology was greatly modified to fine dispersant crystal of compact size. Correlation between wax modification and pour point depression appear to be merely qualitative in such heterogeneous fuel systems.     

Performance improvement of ionic surfactant flooding in carbonate rock samples by use of nanoparticles

Various surfactants have been used in upstream petroleum processes like chemical flooding. Ultimately, the performance of these surfactants depends on their ability to reduce the interfacial tension between oil and water. The surfactant concentration in the aqueous solution decreases owing to the loss of the surfactant on the rock surface in the injection process. The main objective of this paper is to inhibit the surfactant loss by means of adding nanoparticles. Sodium dodecyl sulfate and silica nanoparticles were used as ionic surfactant and nanoparticles in our experiments, respectively. AEROSIL~? 816 and AEROSIL~?200 are hydrophobic and hydrophilic nanoparticles. To determine the adsorption loss of the surfactant onto rock samples, a conductivity approach was used. Real carbonate rock samples were used as the solid phase in adsorption experiments. It should be noted that the rock samples were water wet. This paper describes how equilibrium adsorption was investigated by examining adsorption behavior in a system of carbonate sample(solid phase) and surfactant solution(aqueous phase). The initial surfactant and nanoparticle concentrations were 500–5000 and 500–2000 ppm, respectively. The rate of surfactant losses was extremely dependent on the concentration of the surfactant in the system, and the adsorption of the surfactant decreased with an increase in the nanoparticle concentration. Also, the hydrophilic nanoparticles are more effective than the hydrophobic nanoparticles.     

Evaluations of the effect of selected wax inhibitive chemicals on wax deposition in crude oil flow in sub-sea pipe-lines

Comparative studies were made on the effect of different wax inhibitive chemicals on the wax deposition volume during crude oils flow in pipeline. Two crude oils from Ovhor and Jisike oil fields in the southern part of Nigeria were used in the study. The four identified chemicals: Alkyl sulphonates (wax dispersant), polyethylene (wax inhibitors/crystal modifier), acrylate ester copolymer (pour point depressant, PPD) and xylene (wax solvents) inhibit wax deposition to varying degree of between 14.6–44.9% for crude oil A, and between 21.6–41.4% for crude oil B when 1500 ppm of each chemical was mixed with the crude oil sample. The optimal wax inhibition formulation of polyethylene, xylene, acrylate ester polymer and alkyl sulphonate contains 40.4, 19.2, 27.6, 12.8% and 36.3, 21.5, 25.8, 16.4% for crude oil A and B respectively. Applications of the optimal formulated mixtures of the above chemicals inhibit wax deposition by 58.9% and 62.4% for crude oil A and B respectively.     

Wax deposition during production of waxy crude oil and its remediation

In the current paper, fundamental aspects of wax deposition problems in pipeline are defined, and characterization of paraffin and their solubility tendencies have been discussed. Wax deposition depends on flow rate, the temperature differential between crude and pipe surface, the cooling rate, and surface properties. The physico-chemical characterization of crude oil is determined. The experiments were carried out in “Cold Finger Apparatus.” Best pour point depressant for the selected crude oil has been found out as Lubrizol-6682 among different chemicals available that reduces the pour point from 36° to 12°. The deposition of paraffin wax, its dispersion, and inhibition were studied with available chemicals and by the optimization of suitable additives for particular well. Kinetics of crude oil in terms of time and differential temperature has also been studied and effective dispersion times are observed for particular oil. It is found that dispersion is effective within 30–60 min of starting. Kinetic study of oil with respect to differential temperature is done in two ways either by varying ambient/surface temperature or pumping/reservoir temperature. The tendencies of wax deposition on different sample with neat and treated crude are observed and ideal differential temperature for particular oil to flow is determined.     

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.     

Improvement of heavy oil recovery and role of nanoparticles of clay in the surfactant flooding process

Increasing demand and dwindling supply of crude oil have spurred efforts toward enhancing heavy oil recovery. Recently, applications of nanoparticles (NPs) for heavy oil recovery have been reported. In this study, the use of clay NPs is investigated for enhanced oil recovery. Surfactant solutions and newly developed nanosurfactant solutions with 1600–2000 ppm SDS were tested. The crude oil had a viscosity of 1320 mPa.sec at test conditions. In this study, the role of NPs in the adsorption of surfactant onto solid surfaces of reservoir core is studied. The core flooding experiments showed high potential of using nanoclay for enhancing heavy oil recovery, where 52% of surfactant flooded heavy oil was recovered after injecting the NPs solvent. Moreover, nanoclay has generally better performance in enhancing the oil recovery at surfactant solution, near CMC conditions. The nanoclay surfactant solutions improved oil recovery. The nanoclay, however, showed improved performance in comparison with clay.     

模拟延长油田CO_2驱油过程原油结蜡特性研究

通过对某CO2驱油区块的不同CO2分压条件下原油结蜡倾向和原油结蜡特性评价,计算出原油的结蜡速率、结蜡率及蜡含量,分析了原油的析蜡曲线特性。结果表明,CO2分压增大时原油的结蜡速率和结蜡率提高,蜡含量降低,蜡析出更明显;经CO2处理作用后原油析蜡点向低温方向移动,其蜡含量也相应地比未处理油样的蜡含量降低。     

STUDY OF THE TEMPERATURE AND ENTHALPY OF WAX CRYSTALLIZATION FROM MIDDLE DISTILLATE BY DSC

ABSTRACT

The temperature and enthalpy of the wax crystallization as well as of melting have been studied in the middle distillate (boiling range: 250–375°C) obtained from the indigenous Bombay-High (Off-Shore) crude oil by using a differential scanning calorimeter (DSC). In order to have better understanding of the gel formation processes the broad distillate fraction was fractionated into five narrow fractions of 25°C interval each. From these narrow subfractions the saturates were separated from aromatics by column chromatography, and from saturates the n-paraffins were separated from iso-and cyclo-paraffins by urea adduction, to obtain the n-paraffins concentrates (urea adductables)–-the wax- and the saturated solvent portion–-the UNA. The thermal behaviour of narrow subfractions alongwith their urea adductables and the solvent portions have been studied and the wax appearance temperature (WAT) thus measured has been compared with those obtained by optical microscopy and with the ASTM cloud point, wherever possible. To obtain a clearer picture of the solidification process, further study has been done by preparing synthetic blends of urea adductables in different concentrations in the respective aromatic and iso- and cyclo-paraffinic solvents (UNA) and studying the thermal behaviour of each blend. It is found that the variation in WAT with wax concentration as measured by DSC is identical with that measured by optical microscopy and the ASTM cloud point. However, DSC values are lower than microscopic values and higher than ASTM cloud point. The enthalpy of the blends with the same amount of wax in the aromatic and iso- and cyclo-parffinic solvents indicated that it is higher in the saturated solvent in comparison to aromatic solvent. This confirms the fact that in an aromatic solvent the solubility of the wax is greater, and hence a comparatively lower WAT. The results are further discussed.     

Poly(ethylene-co-vinyl acetate) (EVA) as wax inhibitor of a Brazilian crude oil: oil viscosity, pour point and phase behavior of organic solutions

Several techniques have been used to minimize the problems caused by the wax deposition, and the continuous addition of polymeric inhibitors is considered an attractive technological alternative. The addition of copolymers like polyacrylates, polymethacrylates or poly(ethylene-co-vinyl acetate) (EVA) permit to inhibit the deposition phenomenon; nonetheless, this effect is specific, i.e. similar copolymers present different performance depending on their physical–chemical properties in solution. In this work, the influence of the EVA vinyl acetate content on the viscosity and the pour point of a Brazilian crude oil were evaluated. A correlation between both results was also obtained. The phase behavior and the solubility parameter of EVA copolymers, with different vinyl acetate contents, were investigated in various solvents together with an evaluation of the efficiency of these copolymers as pour point depressants for two different samples of crude oil. EVA copolymers containing 20, 30, 40 and 80 wt.% of vinyl acetate were used and tests with the crude oil were carried out using 50, 500, 1000 and 5000 ppm of EVA as additive. The results obtained from viscosity measurements showed that only below the temperature at which wax crystals start forming did the copolymer exhibit a strong influence in the reduction of oil viscosity, at an optimum concentration. The pour point results revealed EVA 30 to be the most efficient. The results obtained from both experiments showed that the viscosity and the pour point behaviors do not show good correlation. Not only the solubility parameter and the vinyl acetate content, but also the molecular weight and polydispersity have an important influence on both phase behavior and pour point depression. Furthermore, it was confirmed that the additive must present a reduced solubility at a temperature close to the crude oil cloud point. This, however, is not the only factor that determines the efficiency of the additive as paraffin/wax deposition inhibitor.     

Effect of Natural and Synthetic Surfactant on the Rheology of Light Crude Oil

Comparative effectiveness of natural surfactant extracted from Sapindus mukorossi in laboratory and commercial surfactant Brij 30 was determined. Light crude oil was collected from ONGC, Gujarat, India. Its pour point and viscosity decreased significantly after adding surfactants. Wax crystal structure and crystal size distribution was analyzed using cross polarized light microscope and dynamic light scattering techniques. There was remarkable reduction in radius of wax crystals after addition of both the surfactants. Microscopic studies showed significant change in size and structure of wax crystals favoring reduction in viscosity. The possible mechanism behind improvement of flow properties was also analyzed through FTIR studies.     

Nanoenergetic Composite of Mesoporous Iron Oxide and Aluminum Nanoparticles

Ordered mesoporous Fe₂O₃ was synthesized using cetyltrimethylammonium chloride (CTAC) and polyethylene glycol octadecyl ether (Brij 76) surfactant templates. The gel time was monitored as a function of the concentration ratio of precursor to the surfactant. As-prepared FeOOH gels were extracted in ethanol to remove the surfactant and calcined at 200–400°C for 6 h so that α-Fe₂O₃ is produced. The FTIR spectra of these gels reveal complete removal of surfactant and water impurities and the presence of Fe-O vibrations. TEM images show ordering of mesopores in the gels prepared using surfactant templating and no ordering of the pores in the gels prepared without surfactant. The gels after calcinations were mixed with aluminum nanoparticles to prepare nanoenergetic composites. The burn rate of the nanocomposites containing ordered mesoporous Fe₂O₃ mixed with Al nanoparticles was compared with the one containing Fe₂O₃ with no ordering of mesopores and Al nanoparticles.     

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.     

The effects of additives on the reduction of the pour point of diesel fuel and fuel oil

One important industrial problem is the wax precipitation of oil fractions. Factors such as oil composition, temperature, and pressure are effective in causing wax precipitation. One way to prevent wax precipitation is using of chemical inhibitors to reduce pour point. Studying the effects of additives on specific oil samples could help solve wax precipitation problems at various oil processing stages. Despite previous studies that have been done at this aim, finding materials that could decrease the pour point and be economically acceptable, environmentally well optimized, and reasonable is still an unsolved problem. So, it is important to make use of effective materials that could be influential in preventing of wax precipitation or reduction of the amount of precipitation and thus decrease the pour point temperature. In this study, the effects of industrial polymer additives and surfactants that are economically acceptable on decrement of pour point temperature were studied by using three oil product samples, namely light diesel, heavy diesel, and fuel oil (Purification Company of Esfahan). Furthermore, optimized type and concentration of the additives were studied. Results showed that copolymer ethylene-vinyl acetate 28% at a concentration of 500 ppm reduced pour point temperature by 12°C for diesel and that copolymer ethylene-vinyl acetate 19% at a concentration of 300 ppm reduced pour point temperature by 9°C for fuel oil.     

STUDY ON THE MICROEMULSION BEHAVIOR OF THE OXIDIZED PARAFFIN WAX

ABSTRACT

The interfacial tension between paraffin wax and water, as well as oxidized paraffin wax and water has been studied and the results showed that the interfacial tension between oxidized paraffin wax and water decreased obviously after paraffin wax was oxidized to proper degree. Meanwhile the pseudo-ternary phase diagram of the oxidized paraffin wax/surfactants/water system has been determined. It was confirmed that using a single surfactant A or cosurfactant B couldn't prepare oxidized paraffin wax microemulsion and the cosurfactant A/surfactant B mass ratio k _m has a proper range and an optimized value to produce the oxidized paraffin wax microemulsion, moreover, the microemulsion particle distribution was analyzed.     

Experimental Investigations of the Mitigation of Paraffin Wax Deposition in Crude Oil Using Chemical Additives

Abstract

Wax deposition from crude oil is a very expensive problem for oil producers around the world. The objective of this study is to understand the characteristics of paraffin wax deposition and to test the effectiveness of solvents in the inhibition of the crystallization and subsequent precipitation of the paraffin wax and to test the most effective concentration of the solvent used. The oil used here is from the Dakota formation from the Fourteen Mile Field in the Big Horn Basin of Wyoming. Two paraffin inhibitors were tested for this crude oil on a horizontal flow system. The inhibitors are mixtures of solvents, pour point depressants, and wax crystal modifiers. These inhibitors were tested at different concentrations and temperatures and the deposition rates were obtained for each. One inhibitor especially designed for this crude oil was relatively successful, reducing the deposition by up to 59% depending on the temperature.     

高含水油井新型防蜡降粘剂HW—01

本文介绍了根据高含水油井采出液特点研制的高含水油井新型防蜡降粘剂ＨＷ０１，给出了ＨＷ０１的乳化降粘性能、对水包油型原油乳状液油珠聚结温度的降低作用、防蜡效果以及以ＨＷ０１为乳化剂配制的水包油型原油乳状液的热沉降脱水性能，并与ＡＥ１９１０进行了比较。本文还探讨了高含水油井防蜡降粘剂的作用机理，提出了高含水油井防蜡降粘剂研制开发的新思路。