大庆原油蜡沉积规律研究

在理论分析及室内试验的基础上,系统研究了油温、流速、管壁处温度梯度等参数对大庆原油蜡沉积的影响.在原油与管壁温差相同时,不同温度段蜡沉积速率并不相同,存在蜡沉积高峰区.在壁温相同时,随油温升高,蜡沉积速率逐渐增加.在油温、壁温相同的条件下,随流速增加,蜡沉积速率下降.建立了大庆原油蜡沉积模型,并利用该模型预测了铁岭-秦皇岛输油管线不同季节、不同时间沿线蜡沉积分布.铁-秦线冬季存在蜡沉积高峰区;春、秋季出站时蜡沉积最严重,下一站进站时蜡沉积最轻;夏季蜡沉积速率更小,且沿线变化不大.     

高压含气条件下含蜡原油析蜡点测量方法

针对常规方法只能测量地面脱气油的析蜡点,不能测量高压含气条件(油藏条件)下含蜡原油析蜡点的不足,提出了以Arrhenius方程为理论基础,利用高压毛细管黏度计测量高压含气条件下含蜡原油析蜡点的方法。实验结果表明,实验油样地面脱气后析蜡点为63.74℃,油藏条件下析蜡点为59.73℃,含蜡原油地面脱气后更容易析蜡。建议采用油藏条件下的析蜡点作为注水设计参数。     

Study of wax deposition law by cold finger device

Wax deposits in oil pipelines can reduce the effective inner diameter of such pipelines, which may lead to pipeline blockage accidents. In this study, a cold finger experimental device was constructed, and eight groups of experimental scenarios under cold flow conditions were performed in accordance with field conditions. The effects of deposition time and cold and hot bath temperatures on wax deposition were investigated. Results show that when the cold bath temperature remains unchanged, and only the hot bath temperature increases, the deposition quality and rate of mixed waxy crude oil will initially decrease and then increase. During this period, the temperature that corresponds to the maximum deposition mass is the starting point of the wax precipitation peak.     

Effect of drag reducer and pour point depressant on the wax deposition of crude oil pipeline

In this paper, the data of wax precipitation before and after the addition of the additives showed that the addition of the drag reducing agent (DRA) and the pour point depressant (PPD) cannot change the wax appearance temperature (WAT) of crude oil. When the dosage of DRA is small, the DRA cannot increase, stop, or slow down the precipitation of wax crystals. The addition of PPDs has no influence on the amount of precipitated wax crystals. From the GPC analysis, the molecular weight of the wax deposit samples in Linpu pipeline is from 500 to 76,800, which indicates that there is no enrichment of DRA in wax deposit samples. The results of IR show that the C?O group was not detected in the wax deposit sample of the Wei Jing pipeline, which indicates that there is no enrichment of the PPDs in wax deposit samples. The results showed that the DRA and PPD have no obvious effect on crude oil pipeline wax deposition.     

差示扫描量热法在原油蜡含量测定中的应用

我国原油含蜡量较高,蜡含量的测定为原油管道优化运行提供相关数据,保障原油管道安全运行。本文简单比较了三种原油蜡含量测定方法,重点对差示扫描量热法进行了详细阐述。利用差示扫描量热仪DSC822e进行比对试验,对差示扫描量热法在原油蜡含量测定中的准确性和重复性进行了验证,证明了差示扫描量热法在实际应用中的可靠性。     

高凝原油管道输送蜡沉积规律实验研究

针对高凝原油在管道输送过程中管壁结蜡等问题，通过室内建立的小型管流结蜡环道实验装置，模拟输油管道运行中某一管段的蜡沉积情况，研究了含蜡原油的蜡沉积速度，考察了蜡的沉积规律受温度的影响。通过计算，确定了实验条件下的结蜡量，并利用差热扫描量热仪从微观角度分析测试了蜡沉积物的特性，进而探讨了结蜡机理和影响管壁结蜡的因素。     

Evaluation of the inhibitor selection on wax deposition for Malaysian crude oil

Wax precipitates from crude oil when a fluid is cooled down below its wax appearance temperature (WAT). This particularly happens during the transportation of crude oil in the pipeline system. In this study, chemical inhibitors were chosen to prevent and reduce wax formation using seven different types of inhibitors, which are poly (ethylene-co-vinyl acetate) (EVA), poly (maleic anhydride-alt-1-octadecene) (MA), diethanolamine (DEA), cocamide diethanolamine (C–DEA), toluene, acetone, and cyclohexane. The total waxes deposited from the cold finger test are subjected to the type of inhibitor, rotation speed of impeller, and inhibitor concentration. EVA is suggested as the most effective inhibitor based on the amount of wax deposit weight and the value of viscosity. Therefore, this result might be useful for further research work related to wax deposition in the area of crude oil production.     

高凝原油析蜡点的不同确定方法与应用

高凝原油析蜡点不仅是地面工程设计中的重要参数,也是油藏工程应用中确定合理注水温度的关键指标.文中列举了国内外8种析蜡点测试方法在海外某高凝油田A中的应用,分别筛选出满足地面管输工程和油藏工程应用的析蜡点.结果表明,显微观测法的测试结果最高,在地面管输工程应用中最为保守;地层条件下含气原油析蜡点明显低于地面原油析蜡点,应作为合理注水温度的确定标准.     

高含蜡原油生产中析蜡和熔蜡规律实验研究

运用激光测试高压原油析蜡点的最新方法,对井筒中原油的析蜡规律和地层中原油的熔蜡规律进行了研究。研究结果表明：含气原油比脱气原油的析蜡点温度低;井筒中压力高于泡点压力时,原油析蜡点随压力下降而下降;压力低于泡点压力时,原油析蜡点随压力下降而升高;地层条件下熔蜡温度比析蜡温度高。     

Determination of wax content in crude oil

Wax deposition is one of the chronic problems in the petroleum industry. The various crude oils present in the world contain wax contents of up to 32.5%. Paraffin waxes consist of straight chain saturated hydrocarbons with carbons atoms ranging from C18 to C36. Paraffin wax consists mostly with normal paraffin content (80–90%), while, the rest consists of branched paraffins (iso-paraffins) and cycloparaffins. The sources of higher molecular weight waxes in oils have not yet been proven and are under exploration. Waxes may precipitate as the temperature decreases and a solid phase may arise due to their low solubility. For instance, paraffinic waxes can precipitate out when temperature decreases during oil production, transportation through pipelines, and oil storage. The process of solvent dewaxing is used to remove wax from either distillate or residual feedstocks at any stage in the refining process. The solvents used, methyl-ethyl ketone and toluene, can then be separated from dewaxed oil filtrate stream by membrane process and recycled back to be used again in solvent dewaxing process.     

Prediction the variation range of wax deposition with temperature of crude oil in a flow loop

Wax deposition under different temperature conditions was investigated in a flow loop, using a local crude oil with a wax content of 22.5%. The results revealed that the wax deposition increases with increasing coolant temperature. However, the amount of deposit increased initially with increasing oil temperature and then decreased. Based on these results, the corresponding temperature ranges were divided into three ranges: hot flow, sensitive precipitation of wax crystal, and cold flow. Based on diffusion mass, a method and steps for determining the temperature dependence of wax deposition were proposed.     

Transportation technology with pour point depressant and wax deposition in a crude oil pipeline

The authors systematically studied transportation technology with pour point depressant and wax deposition in an industrial crude oil pipeline. Experiment results manifest that beneficiated oil acquires obvious modification effect and the reheating temperature of intermediate heat stations should be above 55°C to avoid effect deterioration. Heating schemes are made with lower heating temperature and wider output range. Moreover, an applicable wax deposition model is established to predict wax deposition distribution along the pipeline under various operating conditions. Wax deposition rate varies severely along the pipeline and it is necessary to consider its non-uniformity in production.     

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.     

Experimental study on the regulation of wax deposition

Abstract

Based on the theory of wax deposition dynamics, and the wax deposition rate model of a Tieling–Jinxi insulated crude oil pipeline was established for Daqing–Jilin mixed oil. Based on their physical properties, the sediments removed from the pipeline were mixed into the original oil sample at different proportions. The sediment volume measured by three physical methods in different seasons was compared. The results showed that the error between the value measured by the wax content method and the predicted value by the model was the smallest, which was -5% in winter and -3.9% in summer. Therefore, the wax content method can be used to estimate the sediment in the pipeline and determine the prediction accuracy of the model.     

大庆原油管输结蜡规律与清管周期的确定

在确定不同流态区管壁处剪切应力、蜡晶溶解度系数、径向温度梯度及管道沿线温降分布的基础上,回归建立了适用于描述大庆油田某两联合站间输油管道蜡沉积的结蜡模型。根据差压法原理,建立了研究原油管输结蜡过程室内模拟试验装置,并覆盖该输油管道的典型工况条件开展了管输原油结蜡模拟试验。相对偏差分析表明,结蜡模型预测结果与试验值的适配性良好。进而在预测运行时间对该输油管道结蜡影响的基础上,结合结蜡层厚度对管道轴向温降及压降的作用,确定了年季节最高与最低土壤温度期的清管作业周期分别为4个月和3个月。     

An experimental design approach for investigating and modeling wax deposition based on a new cylindrical Couette apparatus

The authors report an experimental study carried out through a newly developed Couette apparatus on evaluating the influence of important operating factors such as wall oil temperature, temperature difference (△T) and flow rate. It is found that wax crystal solubility coefficient, temperature gradient, and sheer stress at the wall play leading roles on the internal mechanism. CFD software is adopted for numerical calculation and the result agrees well with the distribution of the flow and temperature field in actual pipelines so that precise parameter values under related experimental conditions are obtained. An improved dynamic wax deposition model considering the enhance effect of resin and asphaltene as well as static deposition condition is established with an average error of 5.6%. Thus the feasibility of the method based on the new apparatus for further research is implied.     

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.     

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.     

The Limitations of the Cloud Point Measurement Techniques and the Influence of the Oil Composition on Its Detection

In the petroleum industry, cloud points are one of the main guides to evaluate the wax precipitation potential of a fluid. The planning of the exploration of a reservoir or the design of its pipelines are based on the measured cloud points for the reservoir oil. It is known that each measuring technique will provide a different cloud point temperature, yet although some of these techniques seem to be more accurate than others, no definite conclusion was established on how cloud points should be measured.

On this work, several cloud point measurement techniques are discussed and compared. It will be shown that some of these techniques, such as viscosity, filter plugging, and differential scanning calorimetry (DSC) can only be used under very favorable circumstances, but it will be argued that because every technique requires some finite, often large, amount of solid to detect the presence of a new phase, the cloud point, defined as the temperature for which the first solid appears in the oil, is not accessible experimentally, and unless a very detailed compositional analysis is available, it is also impossible to predict it accurately with a thermodynamic model. The effect of the paraffin distribution in the oils on the cloud point detection will be discussed, and it will be shown how the compositional information can be used to assess the uncertainty of the measured cloud points.     

Modeling of wax deposition produced in the pipelines using PSO-ANFIS approach

Wax deposition in petroleum industry is one of the major problems requiring accurate predictive procedures to reduce the deficiencies and effective designing of the process. An adaptive neuro fuzzy inference system (ANFIS) model is proposed to predict the wax deposition in oily systems. Parameters of the ANFIS model are optimized using the particle swarm optimization (PSO) method. Results are then compared to those previously reported by Kamari et al., demonstrating better performance of the proposed ANFIS model. Statistical and graphical approaches are employed to investigate the reliability of the proposed model, illustrating the model's capability of precise estimation of the wax deposition. Coefficient of determination (R²) and mean squared error (MSE) values of 0.994 and 0.053 are obtained for the proposed ANFIS model, revealing the reliable prediction of wax deposition by the proposed ANFIS model.