含蜡原油管道蜡沉积老化规律研究

发布时间：2018-01-20 06:32

本文关键词： 蜡沉积老化含蜡量硬度清管　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：当原油输送管道中发生蜡沉积现象时,管道流通半径减小,输送能力降低,严重时会造成蜡堵事故。研究发现,蜡沉积会发生老化现象,即沉积层中蜡分子的扩散与非蜡分子的反扩散,致使沉积层中蜡含量持续增大,而含油量逐步降低的现象,这会导致沉积层硬度的增大,直接加剧清管的难度。探讨蜡沉积老化规律,有助于了解管道中沉积物含蜡量变化情况。沉积物含蜡量对于沉积蜡抗剪切力的变化有重要影响。目前对单相原油蜡沉积的机理、影响因素与预测模型的研究有了些许进展,而蜡沉积老化及其相关的力学规律相对较少。本文利用改装的冷指结蜡装置进行了模拟油蜡沉积老化影响因素的实验研究,分析了各因素对蜡沉积老化的影响规律并利用自行设计的清管实验装置进行了清管器剥离蜡沉积物所需压差的实验研究。本文主要的研究内容与结论如下:(1)利用柴油和市售不同型号的石蜡制备不同需求的模拟油,测定了各个模拟油的密度、凝点和析蜡点等基础物性参数。为蜡沉积老化实验提供基础数据。(2)对传统冷指实验装置加以改进,改进后的装置耗油量少,操作更加便利。利用实验装置进行蜡沉积老化实验,分别讨论了油温、壁温、温度区间、油品含蜡量及碳数分布五种因素对蜡沉积老化的影响规律,发现油温越高,壁温越高,温度区间越高,沉积速率越小,沉积物"老化"时间越长,沉积物最终的含蜡量越大,且高碳数蜡分子含量变化越明显。其中,壁温对蜡沉积速率的影响较大。油品含蜡量越高,低碳数分子含量越高,所得沉积物中蜡含量反而较大,高碳数蜡分子含量变化越明显。(3)在调研国内外关于沉积蜡抗剪切应力认识的基础上,设计和构造了一种装置进行相关实验研究,探索管道中不同老化程度沉积蜡的抗剪切应力变化规律以及清管器剥离蜡沉积物所需压差的变化规律。老化后沉积蜡抗剪切应力随含蜡量呈幂指数增长趋势,沉积物厚度相同时,管径越小,清管器克服沉积层抗剪阻力所需压差越大。运用此规律结合实例进行了清管器压差计算,提出清管器剥离蜡沉积物所需压差的计算流程。对清管具有一定的指导作用。
[Abstract]:When wax deposition occurs in crude oil transportation pipeline, the circulation radius of pipeline decreases, the transportation capacity decreases, and the wax blocking accident occurs when the pipeline is serious. It is found that wax deposition will occur aging phenomenon. That is, the diffusion of wax molecules and the reverse diffusion of non-wax molecules in the sediment layer, which makes the wax content in the deposit layer continue to increase, while the oil content gradually decreases, which will lead to the increase of the hardness of the deposit layer. The difficulty of pipe cleaning is aggravated directly. The law of wax deposition aging is discussed. It is helpful to understand the variation of wax content of sediment in pipeline. The wax content of sediment has important influence on the change of shear stress of deposit wax. At present, the mechanism of wax deposition in single-phase crude oil is discussed. Some progress has been made in the study of influencing factors and prediction models. However, the aging of wax deposition and its related mechanical laws are relatively few. In this paper, a modified cold-finger dewaxing device is used to simulate the influence factors of oil wax deposition aging. The effects of various factors on wax deposition aging were analyzed, and the pressure difference required for stripping wax deposits from wax deposits was studied by using the self-designed pipe-cleaning experimental device. The main contents and conclusions of this paper are as follows: (1) the main contents and conclusions of this paper are as follows: (1). 1) using diesel oil and different types of paraffin wax on the market to produce simulated oil with different requirements. The basic physical parameters such as density, condensation point and wax precipitation point of each simulated oil were measured. The basic data for wax deposition aging experiment were provided. The traditional cold finger experimental device was improved, and the oil consumption of the improved device was less. The effects of oil temperature, wall temperature, temperature range, oil wax content and carbon number distribution on wax deposition aging were discussed. It is found that the higher the oil temperature, the higher the wall temperature, the higher the temperature range, the smaller the deposition rate, the longer the "aging" time of sediment, the greater the final wax content of sediment, and the more obvious the change of molecular content of wax with high carbon number. The higher the wax content in the oil, the higher the molecular content of low carbon number, and the greater the wax content in the sediment. The more obvious the change of molecular content of high carbon number wax is.) based on the investigation of the understanding of the shear stress of depositional wax at home and abroad, a device is designed and constructed to carry out the related experimental study. The variation of shear stress of wax deposited in pipeline with different aging degrees and the variation of pressure difference required by pipe cleaner to peel wax deposit were investigated. The shear stress of deposited wax increased exponentially with wax content after aging. When the sediment thickness is the same, the smaller the pipe diameter, the greater the pressure difference is required for the pipe cleaner to overcome the shear resistance of sediment layer. The calculation process of pressure difference required for stripping wax deposits from pipe cleaner is presented, which can be used as a guide for pigging.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE832.3

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