Study on paraffin wax degrading ability of Pseudomonas nitroreducens isolated from oil wells of Gujarat,India

Microbial remediation is an efficient method of removing paraffin wax from oil wells and pipelines and is found to be environment friendly and economical. In this study, a potential paraffin wax degrading bacterial strain was isolated from oil wells of Gujarat and was identified as Pseudomonas nitroreducens by 16S rRNA sequencing. Pseudomonas nitroreducens showed 100% utilization of heneicosane, 79.74% utilization of pentacosane and 72.50% utilization of triacontane, the major components of paraffin wax in 8 days at 37°C. Pseudomonas nitroreducens degraded 70% of paraffinic crude oil in 10 days at 37°C. The probable end products formed after degradation of eicosane and heneicosane by Pseudomonas nitroreducens were analysed by Mass Spectrum. The above results proving isolate as a potential candidate for degradation of paraffin wax in oil wells.     

微生物对含蜡原油的除蜡降黏效果

为提高含蜡原油的开采与运输效率,挖掘高效嗜蜡菌,笔者以石蜡为唯一碳源,从石油污染土壤中分离出一株嗜蜡菌,对其进行优化培养后,考察了该嗜蜡菌对大庆含蜡原油的除蜡降黏效果,并对其代谢产生的生物表面活性剂性能进行测定。结果表明：该嗜蜡菌能代谢产生脂肽类表面活性剂,具有较强的疏水性及乳化性能;其与含蜡原油作用7 d后,含蜡原油蜡质量分数降低43%、黏度下降18%。该嗜蜡菌对含蜡原油具有一定除蜡降黏作用,可以提高原油流动性能。     

长庆白豹油田固体防蜡技术研究

长庆白豹油田在油田的开发过程中存在着比较严重的结蜡问题,影响原油的正常生产。本文分析了白豹油田结蜡井的原油和蜡样:结蜡井原油中蜡含量高,在15%~20%,胶质和沥青质含量相对较小;蜡样碳数分布主要集中在C26~C39,以微晶蜡为主。应用原油动态结蜡率测试仪和流变仪两种方法测试了MH化学固体防蜡器的性能,它能降低高含蜡原油粘度>80%,降低原油凝点达11℃,防蜡率可达到75%以上。MH化学固体防蜡器在白豹油田现场试验15口油井。现场试验表明,化学固体防蜡器应用后,抽油机载荷明显低于加药前,且能有效地减少常规的清防蜡作业,延长检泵周期。     

Understanding wax appearance temperature in light crude oils by DSC,NMR, and HT-GC

The wax precipitated from oil mixtures primarily consists of C18 to C36 (macro crystalline waxes) or C30 to C60 (micro crystalline waxes), both made of aligned paraffinic and naphthenic molecules. Paraffins have significant impact on wax deposition characteristics as paraffin waxes react and respond easily to temperature changes due to its straight chain structure. In this paper, 12 light crudes of different origin were analyzed by DSC. Method was standardized for the determination of WAT in light crudes and these were found to have WAT ranging from 10 to 30°C. Wax content is proportional to enthalpy of crystallization (ΔH) and the ΔH ranges from 3 to 9 J/g. WAT and wax content do not follow the same trend which is understandable as these parameters depends not only on the concentration and molecular weight of the waxes but also on the chemical nature of both waxy and non waxy part of the crude oil. To understand the trend in WAT, these crudes were also analyzed for paraffinic carbon (Cp), Saturates and CH₂/CH₃ ratio by NMR spectroscopy and carbon number distribution by HT-GC. It was observed that WAT correlates fairly well with CH₂/CH₃ ratio which is in an indicator of normal paraffin content as WAT depends primarily on the nature / type of paraffins. The anomalies can be explained through carbon–wise n-paraffin content by HT-GC.     

Influencing factors governing paraffin wax deposition of heavy oil and research on wellbore paraffin remover

Abstract

Wax deposition is harmful to oil wells, especially for waxy heavy oils at low temperature. The influencing factors on wax deposition of heavy oil were studied and a kind of O/W emulsion type wellbore wax remover was investigated. The results showed that the wax deposition rate of Jinghe heavy oil increased with the increasing wax content and asphaltenes content but decreased with the increasing water content. The oil in water emulsion type paraffin remover was prepared and it showed both good wax dissolution and paraffin prevention ability and can save large quantities of solvent. The results of this study provides a possible way for waxy heavy oils to dissolve wax, to prevent wax deposition and reduce the viscosity of heavy oils by emulsification together, which is helpful to reduce the frequency of hot washing and enhance oil recovery for waxy heavy oils.     

含蜡原油热处理过程中若干组分的作用

本文研究了大庆、南阳原油中的胶质—沥青质,石蜡—正构烷烃和微晶等组分在含蜡原油热处理过程中的作用,从而指出:(1)只有当原油中含有石蜡和适量的胶质—沥青质时,才具备用热处理方法来改善其低温流动性能的可能性。(2)胶质—沥青质在含蜡原油中具有非常显著的分散作用增粘作用。它们通过吸附、共晶等作用改变原池中石蜡的结晶习性、形态及结构强度,从而取得降凝、降粘等效果。(3)各种原油中胶与正构烷烃之比在0.43～5.2之间,经过最佳条件热处理就可显示出热处理效果。胶—正烷烃比在0.6～3.0之间热处理效果最佳。(4)微晶蜡在含蜡原油热处理过程中,其本身不能显示热处理效果,当加热温度高达微晶蜡能在原油中大量溶解的温度时,在降温重结晶过程中,微晶蜡的析出将恶化热处理效果。     

RHEOLOGICAL PROPERTIES OF BOMBAY HIGH CRUDE OIL IN RELATION TO ITS n-ALKANE COMPONENTS

ABSTRACT

Bombay High crude oil is very waxy in nature and has a high pour point (30^°C), The wax present in it largely consists of solid n-alkanes. Changes in the rheological properties of the crude oil after removal of n-alkanes by urea adduction have been determined. Influence of the concentration of n-alkane components on the rheological properties of non adductable components of crude oil have also been studied.     

An Evaluation of the Performance of Selected Wax Inhibitors on Paraffin Deposition of Nigerian Crude Oils

Paraffin deposition in oil production constitutes a critical and difficult to control problem, in terms of productivity and production operation costs, going from the reservoir to surface facilities. In Nigeria, operators spend millions of dollars each year to control the deposition of paraffin and to deal with other paraffin deposition related problems. Expenditures of this magnitude obviously have a significant impact on profits. The main purpose of this work is to assess the net effect of many commercial wax inhibitors on paraffin deposition from a wide range of waxy crude oil systems in Nigeria for the selection of an efficient additive. Deposition from a wide range of waxy crude oil systems from Nigerian oilfields were examined with and without chemical wax deposition inhibitors. The devices used to produce the deposits investigated were cold spot and dynamic flow wax deposition apparatus capable of producing field-like deposits with relatively small volumes of oil in minutes. Results show that most of the commercial wax inhibitors tested could decrease the deposition of wax, but none has the economical capability to solve the paraffin deposition problem for an extended period of time. One intriguing result was that the addition of xylene improved the performance of three wax inhibitors tested. It was also observed that there are subtle differences in inhibitor performance depending on deposition tendencies of crude oil.     

EFFECT OF ASPHALTENE AND RESINS ON THE STABILITY OF WATER-IN-WAXY OIL EMULSIONS

ABSTRACT

Asphaltene, resins and paraffin waxes, their mutual interactions and their influence on the stability of water-in-oil emulsions have been studied. 20 wt % paraffin wax dissolved in decalin was used to model the waxy crude oil. Asphaltene and resins separated from a crude oil were used to stabilize the water-in-oil emulsions. Synthetic formation water was utilized as the aqueous phase of the emulsion. The emulsion stability increased with increasing the concentration of asphaltene with a subsequent decrease in the average particle size distribution of the emulsion. Resins alone are not capable of stabilizing the emulsion, however, in the presence of asphaltene they form very stable emulsions. Dynamic viscosity and pour point measurements provided evidence for resins-paraffin waxes interactions. Asphaltene in the form of solid aggregates form suitable nuclei for the wax crystallites to build over with a mechanism similar to that of paraffin wax crystal-modifiers. As asphaltene are polar in nature they are derived at the oil/water interface which was proved by the ability of asphaltene to reduce oil/water interfacial tension. Consequently, nucleation of the wax crystallites by asphaltene and resins at the interface will add to the thickness of the oil-water interfacial film and hence increase the stability of the emulsion.     

The action mechanism of wax inhibitors (WI) on pour point and viscosity of mixed waxy oil

Several methods had been used to minimize the problems caused by wax deposition in crude oil pipelines during the production and transportation of waxy crude oil; among them, the continuous addition of wax inhibitor (Abbreviation for WI) is considered as the most efficient one. This study uses two kinds of polymeric compounds as wax inhibitors with different solvents on the pour point and viscosity of mixed waxy oils evaluated. These four wax inhibitors defined as WI-1, WI-2, WI-3, WI-4, respectively. Five types of mixed waxy oil have the same wax content but different resin contents. Meanwhile, different resin contents affect the pour point and viscosity of mixed oils. Under different processing temperature, the viscosity of mixed oil measured when the temperature changes among 20 to 60°С. In this work, the results were that the effect of WI-1 and WI-3 relied on the resin content, processing temperature and dosing concentration. For mixed waxy oils, the pour point reductions contacted with dosing concentration and the resin content. The wax inhibitor shows good efficiency when the resin content was between 1.01 and 4.03 wt %. When the WI-1 added, the pour point of mixed oil-1 reduced 30°С at most and viscosity of mixed waxy oil greatly reduced. In sum, toluene as solvent shows better performance of wax inhibitors.     

Correlations Between the Pour Point/Gel Point and the Amount of Precipitated Wax for Waxy Crudes

Abstract:

The amount of precipitated wax is one of the key factors that governs the flow properties of waxy crudes. Experimental results of 24 crudes have shown that approximately 2 wt% precipitated wax is sufficient to cause a virgin waxy crude gelling. Accordingly, a correlation between the pour point and the temperature at which 2 wt% of wax has precipitated out from a crude oil; i.e., T _c (2 wt%), and a correlation between the gel point and T _c (2 wt%) have been developed. The proposed correlation of the pour point is in accordance with the correlation developed by Letoffe et al. (1995) Letoffe, J. M., Claudy, P., Kok, M. V., Garcin, M. and Vollet, J. L. 1995. Fuel, 74(6): 810–817. [CSA][CROSSREF][Crossref] , [Google Scholar] on the basis of 14 crudes from eight countries. The development of the gel point correlation and further verification of the pour point correlation indicate that there is a relationship between the gelling of virgin waxy crudes and the amount of precipitated wax. According to these correlations and the amount of precipitated wax, which can be determined only with a little sample by thermodynamic models or Differential Scanning Calorimetry (DSC) experiment, the gel point and pour point of virgin waxy crude can be predicted even if the oil sample is very limited. Heat treatment and chemical treatment can greatly improve flow behavior of waxy crudes, and more precipitated wax is present when the beneficiated (thermally beneficiated or PPD-beneficiated) crude oils gel. Experimental results showed that approximately two or three times the amount of precipitated wax presents at the gelling temperature when the oils were in their beneficiated (thermally beneficiated or PPD-beneficiated) conditions.     

宁东油田清蜡、防蜡技术分析

在原油开采过程中,随着温度、压力的降低和气体的析出,溶解的石蜡便以结晶体析出、逐渐长大聚集最终沉积在管壁等固相表面上,即出现所谓的结蜡现象.结蜡会堵塞产油层,降低油井产量,同时也会增大油井负荷,造成生产事故.油井结蜡是影响油井高产、稳产的主要因素之一,清蜡和防蜡是高含蜡油井常规管理的重要内容.通过收集整理现场资料、分析原油性质和综合评价不同清防蜡技术的经济效果,确定宁东油田采用热力清蜡和化学防蜡技术较为合适.     

A new experimental investigation on upgrading of waxy crude oils by methacrylate polymers

Several methods have been used to reduce problems caused by wax precipitation during the production and/or transportation of waxy crude oil. Polymers are used to improve pour point and rheological behavior of waxy crude oils. In this work, the influence of the polymer inhibitors such as methacrylate polymers, as wax inhibitor, with different range of molecular weight and alkyl side chain carbons on the rheological behavior and pour point of two Iranian waxy crude oils were evaluated. Two Iranian waxy crude oils were selected on the basis of wax and asphaltene contents. The rheological behavior of these crude oils in absence and in presence of methacrylate polymer was studied. The rheological data cover the temperature range of–1 to 12°C. The results indicated that the performance of methacrylate polymer was dependent on the molecular weight, alkyl side chain carbons and the asphaltene content of crude oil. Methacrylate polymers with longer alkyl side chains than 18 carbons would perform best as wax inhibitors in two cases. Also, for crude oil with low asphaltene, higher molecular weight methacrylate polymer is the best flow improver and lower molecular weight methacrylate polymer showed good efficiency for crude oil with high asphaltene content.     

顺北原油防蜡剂的研制及防蜡机理*

为防止顺北原油管道集输中结蜡,根据顺北原油析出蜡的碳链分布设计合成了以甲基丙烯酸十八酯、醋酸乙烯酯、对苯二乙烯为单体的超支化聚合物防蜡剂,考察了合成条件对防蜡剂防蜡性能的影响,采用冷指法评价了该防蜡剂的防蜡效果并分析了该防蜡剂的防蜡机理。研究结果表明,顺北原油的含蜡量为6.57%,析蜡点为23℃,在环境温度下极易结蜡。优化得到防蜡剂最佳合成条件为:甲基丙烯酸十八酯和醋酸乙烯酯摩尔比为5∶1,对苯二乙烯加量为单体总质量的0.02%,引发剂加量为单体总量的0.7%,聚合温度70℃,聚合时间为6 h。当防蜡剂加量为500 mg/L时防蜡率达到70%以上,表现出良好的防蜡效果。当加入防蜡剂600 mg/L后,原油凝点降低8℃,析蜡点降低13.4℃,防蜡剂与石蜡形成了共晶,破坏了石蜡的晶体结构,抑制了石蜡的继续增长,从而达到防蜡的效果。图19表1参10。     

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.     

Change of Yield Stress of Daqing Crude Oil With Thermal and Shear History

Abstract

Daqing crude oil is a typical waxy crude oil with a wax content of 26.6 wt.% and a gel point of 32°C. The yield stress of waxy crude oils is an important property in the process calculation and flow safety analysis for heated oil pipeline. The Daqing crude oil was studied and the yield stress change with shear history was explored through simulation experiment of pipelining. It was found that the change of throughput variation or shear rate showed little effect on yield stress. There existed a peak yield stress on the relation curve of yield stress with final dynamic cooling temperature. The prediction model of yield stress for waxy crude oil under the condition of shutdown was developed and can be used to predict the yield stress of Daqing crude oil at certain heating temperature, final dynamic cooling temperature, and measurement temperature. For the 139 groups of yield stress data of Daqing crude oil from the simulation experiment of pipelining, the result of prediction with this model showed that the average relative deviation between the yield stress measured and predicted is 30.27%, and the coefficient of correlation is 0.9623.     

EFFECT OF ASPHALTENE AND RESINS ON THE STABILITY OF WATER-IN-WAXY OIL EMULSIONS

Asphaltene, resins and paraffin waxes, their mutual interactions and their influence on the stability of water-in-oil emulsions have been studied. 20 wt % paraffin wax dissolved in decalin was used to model the waxy crude oil. Asphaltene and resins separated from a crude oil were used to stabilize the water-in-oil emulsions. Synthetic formation water was utilized as the aqueous phase of the emulsion. The emulsion stability increased with increasing the concentration of asphaltene with a subsequent decrease in the average particle size distribution of the emulsion. Resins alone are not capable of stabilizing the emulsion, however, in the presence of asphaltene they form very stable emulsions. Dynamic viscosity and pour point measurements provided evidence for resins-paraffin waxes interactions. Asphaltene in the form of solid aggregates form suitable nuclei for the wax crystallites to build over with a mechanism similar to that of paraffin wax crystal-modifiers. As asphaltene are polar in nature they are derived at the oil/water interface which was proved by the ability of asphaltene to reduce oil/water interfacial tension. Consequently, nucleation of the wax crystallites by asphaltene and resins at the interface will add to the thickness of the oil-water interfacial film and hence increase the stability of the emulsion.     

热处理温度对长庆原油蜡沉积特性的影响

通过Couette蜡沉积装置及DSC热分析探究了热处理温度对长庆原油蜡沉积特性的影响,发现随着热处理温度的升高,长庆原油蜡沉积速率减缓,蜡沉积层老化速率加快;经50 ℃和60 ℃热处理的长庆原油,蜡沉积层出现了分层现象,其表层为流动性较强的凝油状蜡沉积层,底层为结构较为致密的类固态蜡沉积层;经70 ℃热处理的长庆原油,蜡沉积层极薄且致密,无分层现象,其表面无凝油状蜡沉积层。采用沥青质分散程度分析、DSC热分析及蜡晶形貌显微观察探究了其影响机理,发现随着热处理温度的升高,长庆原油沥青质分散程度增大,从而使其析蜡点降低,蜡晶团聚性增强,原油低温流动性得以改善,进而对其蜡沉积特性产生了显著影响。     

Production of High-Grade Asphalt from Liaoshu Crude Oil

Abstract

The high viscous crude oil for Shuguang No. 1 zone of Liaohe oilfield has the characteristics of high density (ρ₂₀ = 0.9977 g.cm^?3), high viscidity (ν₁₀₀ = 1,223.9 mm².s^?1), and high solidifying point (SP = 48°C), which belongs to low sulfur naphthene-base crude oil. The comprehensive evaluations indicate that this oil has no gasoline fraction and the diesel oil is only 7.19%. In addition, the lubricating oil distillate is not suited to produce lubricating oil and heavy oil is not good feedstock for catalytic cracking. However, the low wax and high resin, as well as asphaltene content, make it an ideal raw material for producing paving asphalt. The vacuum residue of this crude acted as base oil and three kinds of waste oil with high aromatics and low wax content were selected as blenders. Various brands of high-grade paving asphalts meeting GB/T15180-94 (China) specification were produced by blending method. The blending effects were investigated and corresponding mathematics models were set up.     

降凝剂对管输原油含蜡的处理作用

本文介绍了含蜡原油在管道输油过程中的结蜡过程,以及利用降凝剂降低含蜡原油析蜡点的机理,通过控制管道中原油的粘度达到有效地利用降凝剂的目的。