濮阳原油蜡沉积特性实验

利用旋转式动态结蜡装置,对濮阳原油进行不同油温、不同温差、不同转速等条件下的蜡沉积实验。濮阳原油高含蜡量、双析蜡峰的特性使其蜡沉积规律具有较大的变化性,在管输濮阳原油的过程中要尤其注意输送温度,尽量避开原油的最大析蜡高峰区。其他条件不变时,随油温升高,蜡沉积速率与蜡晶溶解度系数的变化趋势相同;随油壁温差增大,蜡沉积速率逐渐增大;随转速增大,蜡沉积速率逐渐减小。     

含蜡原油管道蜡沉积速率的计算

影响含蜡原油管壁蜡沉积的因素主要有黏度、管壁剪切应力、蜡分子浓度梯度和管壁处温度梯度等,在分析它们对蜡沉积的影响时,需综合考虑。根据测试结果,由压差法计算蜡沉积;由黏温测试结果,拟合原油黏温曲线;根据蜡沉积的热力学模型,计算管壁蜡分子浓度梯度;由热平衡计算管壁径向温度梯度,将所得数据作为基础数据,对蜡沉积系数进行非线性拟合。管道在起始阶段,蜡沉积速率较小;随油流向前,油温降低,原油中的蜡逐渐结晶析出,蜡沉积速率逐渐增大;油流继续前进,与管壁的温差减小,蜡沉积速率逐渐减小。     

流花16-2油田海底管道原油蜡沉积规律实验研究北大核心CSCD

针对流花16-2油田海底管道原油蜡沉积严重的问题,利用环道蜡沉积实验,研究了不同原油温度、流速、油流与管壁温度区间及长时间老化作用影响下的蜡沉积规律和蜡沉积物性质。实验结果表明,在溶解度、剪切剥离、老化等不同的机理和作用下,原油温度、流速、油流与管壁温度区间及长沉积时间老化作用等因素不同程度地影响了蜡沉积物质量、沉积速率、含蜡量和实际沉积蜡质量。尽管流花16-2原油为低凝、低黏、低含蜡原油,但其所在海域较低的水温仍可使管道发生严重的蜡沉积,因此建议在制定清蜡方案时考虑更短的清管周期,确保油田海底管道的安全运行。     

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。     

流花16-2油田海底管道原油蜡沉积规律模拟分析北大核心CSCD

流花16-2油田海底管道原油在深水不保温输送过程中,管壁结蜡对管道全线总传热系数的变化影响很大。本文通过室内环道蜡沉积实验建立流花16-2油田管道蜡沉积预测模型,模拟研究了不同沉积时间条件下管道沿线结蜡速率及结蜡厚度的变化,并引入单位时间管道全线总结蜡量概念对管道全线结蜡速率进行了描述。结果表明,在管壁结蜡层的保温作用下,管道沿线最大蜡层厚度位置处的总传热系数迅速降低导致后管段油流温度升高,管道沿线蜡沉积速率峰值向管段末端移动;随着沉积时间的增长,管道全线结蜡区域逐渐扩大,导致单位时间管道全线总结蜡量增大;根据管道沿线最大蜡层厚度2 mm或管道全线总结蜡量10 m^3的沉积时间,推荐流花16-2海底管道清管周期为3~5 d,以保障海底管道的安全运行。     

凝析油管道蜡沉积特性及蜡沉积模型研究

目前,诸多学者认为凝析油管道无需进行清管作业,但现场却时常发生堵管现象。基于此,利用环道实验装置确定不同油温、壁温及油流流速对凝析油析蜡特性的影响,通过相关系数矩阵和方差膨胀因子验证了动力学蜡沉积速率模型中参数选取的准确性,并通过全局优化求解方法对无量纲参数进行求解,最后结合现场清管作业验证模型准确性。结果表明,油壁温差越大,温度区间越小,沉积物质量和蜡沉积速率越大,油流流速对蜡沉积的影响存在临界状态;沥青质的含量对于蜡沉积速率和沉积物中的蜡含量影响较大;全局优化算法中Levenberg-Marquardt算法的误差最小,模型精度最高,模型决定系数0.901 7;预测结果中当量蜡沉积厚度和模型蜡沉积厚度的相对误差范围在[-18.63%,27.35%],平均相对误差绝对值为6.12%,证明了动力学蜡沉积模型预测结果的准确性。     

降凝剂对南阳原油管壁蜡沉积特性的影响

以魏荆线管道所输送的南阳原油为研究对象,利用旋转式动态结蜡装置,考察了添加降凝剂对原油蜡沉积规律的影响。实验结果表明,添加降凝剂改变了蜡晶的生长历程,增大蜡晶体积并阻碍三维网状结构的形成,弱化了管壁沉积蜡晶的结构强度,减小了胶凝原油的屈服强度;在保持壁面温差、油品温度、旋转筒转速相同的情况下,在低流速区间,添加降凝剂会增大南阳原油的蜡沉积速率,在高流速区间则对管壁结蜡具有一定的抑制作用;降凝剂的添加使壁面剪切应力成为影响加剂南阳原油蜡沉积速率的主要因素。     

含蜡原油石蜡沉积模拟方法研究

对从苏丹Unity油田现场取得有代表性的原油样品进行了原油组分分析和析蜡点测试。并针对油田的生产状况,利用与美国德士古石油公司合作建立的自动化高压石蜡沉积循环管道模拟系统,采用冷却实验步骤测试了苏丹原油从高于原油析蜡点温度到较低环境温度范围内在现场流速、油温和环境温度下的石蜡沉积速率,定量研究了流速和油温对石蜡沉积速率的影响,并采用分子扩散和剪切效应的总效应来描述石蜡沉积机理。利用临界蜡张力作为模拟放大因子,采用半经验的石蜡沉积数学模型,预测了Unity油田21井的生产井筒在现场生产条件下的石蜡沉积情况,模拟了不同产量和不同时间的蜡沉积剖面。结果表明,该油井在目前高产条件下,未发生石蜡沉积问题;在低产时,须考虑清蜡和防蜡措施。     

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.     

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。     

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。     

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.     

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.     

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.     

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。     

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.     

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.