普适性结蜡模型研究

根据原油在管道内流动特性及析蜡规律,提出了有效析蜡量的计算方法.利用F检验法筛选了原油结蜡的主要影响因素,包括原油黏度、管壁处剪切应力、温度梯度及管壁处蜡晶溶解度系数.利用9种原油室内环道结蜡实验数据,按照逐步线性回归的方法,得到了含蜡原油的普适性结蜡模型.该模型不需进行结蜡模拟实验,只需根据原油的黏度、析蜡特性及密度等物性参数就可预测原油的结蜡规律.在未进行室内结蜡模拟实验的情况下,利用普适性结蜡模型预测了中宁-银川输油管道不同工况下沿线结蜡分布,并和现场运行参数进行了对比,平均误差为6.32%,最大误差为20%,预测结果为现场清管作业提供了依据.     

长输管线析蜡特点分析及应用

根据目前原油长输管线实际工作参数,运用流体热力学原理,从理论上对原油长输管线的温度场、析蜡特点及其影响因素进行了分析。轴向温降是影响管壁结蜡强度的主要因素。在此基础上,对轴向温降计算公式进行了推导,并运用实际资料进行运算,得出了不同自然地温条件下输油管道起点温度的优化方案,为今后的生产管理提供了理论依据。     

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。     

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。     

石蜡沉积动力学的测量和预测

讨论了在模拟运行流动条件下测量蜡沉积速度的试验技术，介绍了改进后的试验室试验方法和计算模型，以此来预测管道中的蜡沉积速度和长期积蜡对管道压降与温度分布的影响。该计算模型除了适用于计算沿管道的瞬时沉积速度外，还能模拟管道运行中结蜡的长期影响。计算结果表明，结蜡厚度和温度是位置、沉积量和压降的函数，而这些又都是时间的函数。文章还对海洋管道的蜡沉积进行了实例研究。研究结果表明，以该计算模型预计的大部分蜡     

中洛原油管道结蜡规律

通过建立濮阳原油蜡沉积模型,预测不同运行工况下中洛管道沿线的结蜡厚度分布。同一运行条件下,沿着管道输送方向,管壁结蜡厚度逐渐增大,到达结蜡高峰区后逐渐减小;随着运行时间的延长,结蜡最严重处略向后方偏移。随着出站温度的降低,中洛管线内出现蜡沉积的管段逐渐增长;结蜡最严重处逐渐向出站处推移,且蜡层厚度基本相同。     

含蜡原油输送管道清管周期预测模型研究

含蜡原油温度低于其析蜡点时,蜡分子会沉积在管壁上,降低管输效率。定期清管可以清除管道结蜡,提高管输效率。为了确定安全、经济的清管周期,从含蜡原油输送管道管输效率的定义出发,结合蜡沉积速率预测方法,提出了描述管道清管周期与管输效率、结蜡速率之间关系的数学模型,确定了应当进行清管时的管输效率阈值。以塔里木油田英买力-牙哈含蜡原油输送管道为例,计算管道清管周期为110 d,验证了该方法的有效性。该预测模型为合理决策含蜡原油输送管道的清管周期提供了依据。     

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。     

基于有限元法的含蜡原油管道停输过程温降数值模拟

含蜡原油在管输过程中不可避免地会发生停输情况,随着管内原油温度降低至凝点以下,会出现凝油层导致凝管现象,严重影响管道安全经济运行,因此有必要研究含蜡原油管道停输过程的温降问题。在原油管道正常运行工况的基础上,考虑蜡沉积现象,建立了含蜡原油管道停输传热模型。采用温度场三角形单元格划分→离散→合成有限元这一有限元法求解思路对模型进行数值求解,讨论了在不同停输时间管道温降的变化规律。通过对管道温度场计算结果进行分析可知,管道对周围环境温度场的影响随着离管道距离的增大而逐渐减小;在不受热影响的外部区域,温度场等温线近似为一组波动的平行线。该研究成果提供了一种简单易行、准确可靠的温降模拟计算模型,为蜡质原油停输后再启动过程的方案制定提供了关键数据的采集方法。     

考虑剪切弥散效应的结蜡厚度

在分析热原油管道结蜡机理的基础上，给出了考虑分子扩散与剪切散共同作用下的结蜡厚度公式，可计算给定时间内热油管道的结蜡厚度及形成某一结蜡厚度的时间。     

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.     

Prediction of Wax Deposition in an Insulation Crude Oil Pipeline

This study establishes an insulation crude oil pipeline wax deposition experimental device and describes the experimental method for insulation crude oil pipeline wax deposition. The experimental program is based on the operational plan of Tieling–Huludao insulation crude oil pipeline. The data are analyzed according to the effect of varying oil temperature, insulation thickness, and flow on wax deposition. Using SPSS software, a Daqing crude oil wax deposition rate model is derived from the linear regression. The use of the wax deposition rate model forecasts the wax deposition of the Tieling–Huludao insulation crude oil pipeline during different seasons.     

Wax Deposition in Flow Lines Under Dynamic Conditions

The wax deposition in the tubing, pipeline, and surface flow line is the major problem in the oil fields. It generates additional pressure drop and causes fauling and ultimately increases the operating cost during production, transportation, and handling of waxy crude oil. In this work, attempts were made to study the wax deposition in the flow lines due to Indian crude oil under dynamic condition. The experimental work was carried out for neat crude oil and pour point depressants treated crude oil at different ambient/surface temperature and pumping/reservoir temperature. It was observed that temperature has significant effect on the wax deposition of the crude oils. From these studies, ideal temperature of crude oil to pump in the pipeline or flow line was determined. The present investigations also furnishes that the selected pour point depressant in this work decreases the wax deposition significantly and may be used for controlling the wax deposition problems in case of Indian crude oil.     

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。     

Physical properties of wax deposits on the walls of crude pipelines

Wax deposits on the wall of a crude oil pipeline are a solid wax network of fine crystals, filled with oil, resin, asphaltene and other impurities. In this paper, a series of experiments on wax deposition in a laboratory flow loop were performed under different conditions （flow rate, temperature differential between crude oil and pipeline wall, and dissolved wax concentration gradient）, and the wax deposits were analyzed, so quantitative relationships among wax content, wax appearance temperature （WAT）, shear stress, and radial concentration gradient of dissolved wax at the solid/liquid interface were obtained. Finally, a model was established to predict WAT and the wax content of the deposit.     

管输温度对EVA型防蜡剂防蜡效果的影响

采用Couette蜡沉积实验装置研究了聚乙烯醋酸乙烯酯(EVA)型防蜡剂对长庆原油蜡沉积特性的影响,分析了不同管输温度条件下EVA型防蜡剂的防蜡效果。研究发现,与空白原油相比,加剂原油的蜡沉积速率大幅降低,同时蜡沉积物的老化速率升高。无论是在恒定油壁温差还是在恒定壁温条件下,EVA型防蜡剂的防蜡效率均随油温的升高而不断降低,EVA对蜡沉积物老化速率的提升幅度均随油温的升高而不断增大。通过分析EVA型防蜡剂对长庆原油流动特性、低温胶凝结构特性及微观蜡晶形貌的影响,阐明了EVA型防蜡剂对长庆原油蜡沉积特性的影响机理,并从蜡沉积物初始凝油层抗剪切强度及蜡分子扩散速率2个角度揭示了管输温度对EVA型防蜡剂防蜡效果的影响。     

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.     

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.