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.     

An Experimental Study on Wax Deposition of Water in Waxy Crude Oil Emulsions

Abstract

The key factors affecting wax deposition of water-in-oil emulsion were studied experimentally using a cold finger device. Wax deposition characteristics of emulsions were obtained. The results showed that the wax deposition profile of emulsions as a function of temperature parameters was similar to that of single oil. However, the effect of the extent of water cut on wax deposition was obviously different at different temperatures. Furthermore, the relative mass of deposit was proposed and found independent of water cut, from which wax deposition rate at different water cuts could be predicted and the predicted values were in good agreement with experimental data.     

Studies of Wax Deposition Onset in the Case of Indian Crude Oil

Abstract

Before taking any decision regarding strategies for prevention and remediation of wax deposition problems in the production tubing, pipeline, and process equipment, it is essential to identify the conditions of wax deposition and to predict wax deposition rates. In this article a study on the prediction of wax deposition, different factors affecting the deposition, and the practical applications of laboratory results obtained for characterization of the Indian crude oils have been presented. The waxy crude characterization study was performed on both stock tank crude oil and recombined integrated crude oil. The results of it exemplify the influence of composition, temperature, and pressure on the solid behavior of Indian paraffinic crudes.     

热处理对添加防蜡剂长庆原油流动性及蜡沉积特性的影响研究

基于流变性测试和蜡沉积实验研究了热处理温度对添加EVA/PAMSQ复合防蜡剂的长庆原油的流动性和蜡沉积特性的影响。研究发现加剂原油依然具有热处理效果,50℃热处理条件下加剂原油的流动性改进效果较差,随着热处理温度升高至60、70和80℃,加剂原油的流动特性(如凝点、黏度、小振幅振荡剪切特性)显著改善。80℃热处理条件下,加剂原油的凝点已低于0℃,表明热处理与EVA/PAMSQ复合防蜡剂具有良好的协同效果。同时,随着热处理温度的升高,加剂原油的蜡沉积速率逐渐降低,但蜡沉积物的含蜡量逐渐升高,这可能不利于蜡沉积物的剥离。蜡沉积物呈现出非均质结构,表层蜡沉积物为凝油状,底层蜡沉积物具有比表层蜡沉积物更高的析蜡点和屈服强度。     

集输油管道中的结蜡与防蜡

文章阐述了集输油管道中的结蜡问题,分析了原油中蜡沉积物的基本组成、集输油管道结．蜡机理,总结了影响结蜡的因素,并概述了目前主要的防蜡技术。同时还介绍了防蜡剂的防蜡机理、类型以及油田集输油管道中常用的防蜡剂产品。     

Studies on the Influence of Cationic Surfactant Chemical Additives on Wax Deposition

Wax deposition studies were carried out to investigate the modification of wax crystals when gas oil was doped with some polymeric surfactant chemical additives. These additives were synthesized via esterification of chloroacetic acid and different alcohols to corresponding esters that were quaternized with polytriethanol amine and polyvinylpyridine to give polycationic surfactants. The surface activities of these polymers were evaluated using standard methods. Properties such as pour point depression data and average carbon number were studied. The behavior of the mixtures of the prepared surfactants on the depression of pour point was determined. The results given indicated that these additives are good surfactants and low temperature improvers for gas oil.     

Paraffin Deposition Mechanism and Paraffin Inhibition Technology for High-carbon Paraffin Crude Oil From the Kazakhstan PK Oilfield

The compositions and structure of the Kazakhstan PK crude oil is analyzed in the methods of GC, ¹H-NMR, and DSC. It was found that the main reasons for paraffin seriously depositing on the well wall were the higher carbon numbers in the paraffin molecule, lower branched-chain degree in the paraffin molecule, the lower content ratio of asphaltene and resin to paraffin, wellhead temperature being lower than paraffin-appearing temperature, the higher gas-oil ratio, and lower water cut in the produced liquid. A new paraffin inhibitor whose paraffin inhibition rate is above 60% for the Kazakhstan PK crude oil was developed. Its paraffin inhibition mechanism is researched by using microscope and contact angle instrument. The paraffin inhibition mechanism is mainly to prevent formation of paraffin crystal with network structure by modifying paraffin crystals structure and to form the surface against paraffin deposition by changing the wettability of the paraffin deposition surface.     

A Reliable Model for Estimating the Wax Deposition Rate During Crude Oil Production and Processing

Deposition of wax in surface and subsurface pipes and even perforations can lead to serious problems including pore spaces blockage, plugging of pipelines, and minimum profitability. Therefore, understanding wax deposition and wax related-properties improves the oil recovery and processing operations in petroleum industry. In this research work, the rate of wax deposition is correlated to a number of main parameters such as the dynamic viscosity of crude oil, shear stress, gradient of wax molecular concentration and temperature difference in pipeline system through implementation of a newly developed model, known as least squares support vector machine (LSSVM) along with the coupled simulated annealing (CSA) optimization strategy. The possible outliers are detected through employing the Leverage technique which involves residual errors plots, Williams' plot, and Hat matrix. The results imply that whole collected real data are in applicability domain of the proposed model. Using a comprehensive statistical investigation, a very good agreement between the predicted LSSVM-CSA outputs and real wax deposition rate is found such that the average relative error percentage and determination coefficient (R2) are 0.048% and 0.999, respectively. Such a study can assist to provide better designs (technically and economically) for underground and surface facilities while dealing with wax deposition cases.     

Artificial Neural Network's Prediction of Wax Deposition Potential of Nigerian Crude Oil for Pipeline Safety

Abstract

Paraffin wax deposition from crude oil along pipeline is a global problem, making preventive methods preferred to removal methods. In this work, a neural network model based on mathematical modeling technique using regression analysis as the statistical tool was developed to predict the wax deposition potential of 11 reservoirs in Nigeria. Using the viscosity-pressure-temperature data obtained from these fields to supervise the model, the model accurately predicted the present real-life situation in each field. Conclusively, the model could be used to predict wax deposition potential of any reservoir that is yet to be explored provided the temperature used during prediction is close to the actual reservoir temperature.     

输油管道蜡沉积试验新技术及装备

介绍了输油管道蜡沉积试验的一些新技术和装备。在析蜡点测量方面,主要介绍了旋转黏度计法、偏光显微镜法和差示扫描量热法;在蜡沉积量测定方面,主要介绍了清管法、拆管法、压降法、传热法、液体置换与检测法、超声波法和激光测厚法;在蜡沉积物组分测定方面,主要介绍了气相色谱法和气相色谱-质谱联用技术。这些新技术和装备为解决蜡沉积试验和工程中的问题提供有效手段。     

The Influence of Operating Temperatures on Wax Deposition During Cold Flow and Hot Flow of Crude Oil

The authors examined the effect of operating temperatures on the wax deposition by using the cold finger device and high-temperature gas chromatography. The decreases in coolant temperature have been observed to result in increases in the amount of total deposit, but decreases in the amount of high carbon number components in deposit. When the bulk oil temperature increases from the gelling, cold flow, and hot flow conditions, the deposition rate decreases first, then increases, and then finally decreases while the wax content and the percentage of high carbon number component increase all the way.     

石油管线蜡沉积试验研究进展

含蜡原油在开采和管输过程中由于环境温度的降低会沉积在井壁和管壁上,减小了管道的有效流通截面,降低管道的输送能力,甚至会造成管道堵塞事故。综述了国内外学者对于石油管线蜡沉积的试验研究进展,分析了不同蜡沉积装置的工作原理、特点和适用范围,并提出了一些研究建议。     

络合-分光光度法测定食品级石蜡中的痕量铅

食品级石蜡中的铅与双硫腙能够生成红色络合物,采用分光光度法测定络合溶液的吸光度,建立溶液的吸光度与铅含量回归方程。实验证明,络合溶液在波长510nm处有最大吸收峰,当溶液中铅质量分数在0～10 0mg/kg内,铅含量与吸光度成良好的线性关系,检出限为0 1mg/kg。该方法适用于食品级石蜡、微晶蜡中铅的测定。     

柱头进样气相色谱法测定石蜡、微晶蜡的组成

采用柱头进样的高温气相色谱技术，建立了测定石蜡和微晶蜡中正、异构烷烃含量及相应的碳数分布的方法。首先采用当前基线积分得到正、异构烷烃的总量，再从中扣除由谷谷积分所得正构烷烃部分而得到异构烷烃含量的方法进行各碳数正、异构烷烃含量的计算。石蜡组成测定的相对标准偏差在±３％以内，微晶蜡测定的相对标准偏差±６％以内。并与分子筛吸附法的测定结果进行了对比，两者有很好的一致性。本方法适用范围广，信息量大，同时具有分析速度快，准确度、精密度高等特点，有实用价值。     

分子筛吸附法测定石蜡中正异构烃

采用两步分子筛吸附的方法测定石蜡的正异构烃类含量，所用仪器简单，操作简便，数据重复性好，相对标准偏差小于±１％，与气相色谱法的结果对比较好，并进行了实际蜡样的测定，证明本方法实用性较强，具有推广价值。     

Laser Based Detection of Paraffin in Crude Oil Samples: Numerical and Experimental Study

A laser spectroscope was used to detect paraffin in paraffin contaminated oil samples. After passing through the oil sample, the laser light was detected by using a semi-conductor photodiode, which in turn converts the light signal into electric voltage. The samples studied have paraffin concentrations ranging from 20-60% wt and a thickness of 1-10 mm. The results showed a good agreement with Beer Lambert's Law for the attenuation of light. A 1-D mathematical model based on energy balance and describing the process of laser radiation attenuation within the oil sample was developed and numerically solved. The model was used to predict the net laser light and the amount of light absorbed per unit volume at any point within the oil sample. The results of the numerical model were found to be in correlation with those obtained from the experiments. The mathematical model presented was then used for different types of oil products to determine the local rate of absorption in an oil layer under different working conditions. Most of the factors affecting the light absorption were considered. The effects of the angle of incidence, bottom reflectivity, and layer depth are presented and discussed.     

任京线正反输运行长期不清管条件下的结蜡规律

针对任京输油管道正反输运行长期不清管的情况,通过比较现有结蜡模型的优缺点．建立了适用于大庆冀东混合原油的结蜡模型;考虑结蜡过程的周期性和时效性,研究了任京线的结蜡规律;利用两次任京线改线工程的现场实测结蜡厚度进行了验证,实测值与预测值的最大相对误差为15．8％;分析了任京线管壁蜡沉积物的基本物性和结构强度。研究成果为任京线安全清管提供了理论依据。     

海底混输管道蜡沉积研究与发展

在综述国内外学者取得的蜡沉积研究成果的基础上,着重分析了目前对多相流动蜡沉积机理、沉积层厚度测量方法、多相流蜡沉积试验和多相流动蜡沉积动力学模型的研究,提出了该研究领域存在的问题,明确了今后的研究方向和技术路线。     

The Hardening Process and Morphology of a Wax Deposit in a Pipe Flow

Abstract

Paraffins crystallize out from waxy oil solution as temperature is lowered and form a deposit on transportation pipelines. The deposit becomes hard with an increase in its solid content, making cleaning difficult. A good knowledge of the crystal morphology is essential to understand the hardness of the deposit. The morphology of the deposit on a cold pipe was studied with scanning electron microscopy. The crystal morphology changed gradually from a round, plate-like crystal to mal-crystals and spherulites as the deposit grew. The deposit became harder with a decrease in its oil cavities created by lateral growing of macroplate crystals and formation of mal-crystals. The morphology change gradually occurs at temperatures between the cloud point and wax dissolution temperature depends on cooling rates. The results revealed another aging mechanism is the change in crystals morphology.     

英东油田油井加注清蜡剂维护试验及效益评价

英东油田原油黏度9.33 mPa·s,析蜡点38℃,含蜡11.96％,含蜡较高,在原油开采工程中容易出现结蜡,造成油管及抽油泵内部结蜡现象,严重的会造成泵卡、油管堵死的现象,影响油井的正常生产.针对这种现象,开展了清蜡剂清防蜡试验,对清蜡剂的性能进行试验评价,选取部分井进行现场应用试验,现场应用发现清蜡剂有助于缓解原油结蜡的速度,从而延长了油井的洗井周期和检泵周期,提高了油井的开采效率,降低了油井的维护成本.建议继续扩大范围使用,并进行下一步工艺优化研究.