胶凝原油粘弹性研究及其蠕变模型的建立

发布时间：2019-05-28 08:20

【摘要】：本文通过流变测量、DSC方法研究了两种长庆含蜡原油基本物性和流变特性,对含蜡原油粘弹性结构的形成及屈服破坏过程特性进行了详细的分析和探讨,并基于损伤变量理论,建立了能够描述恒定应力和连续增加应力条件下粘弹性结构屈服破坏全过程的蠕变模型。本文主要研究内容如下:(1)两种长庆油样均为典型含蜡原油,胶质、沥青质含量不高(分别小于1.3%和0.027%),密度较小(均小于0.84g/cm3),蜡含量高(均大于11%),凝点较高(50℃热处理温度下分别为24℃和17℃),且凝点随热处理温度升高而显著降低,常温下流动性较好。(2)研究了降温速率、剪切应力和重复加热对降温过程中长庆含蜡原油粘弹性结构形成过程的影响,发现降温速率越小、剪切应力越小、重复加热温度越高,原油开始胶凝的温度越高,同时相同温度下形成的结构越强。利用流变学原理分析计算验证了原油中蜡晶溶剂化层的存在,并结合结晶学原理,蜡晶溶剂化层的存在使得原油中的内相浓度增大,更多液态油包裹其中,导致体系粘度增大。(3)研究了不同的应力加载方式对长庆含蜡原油粘弹性结构屈服破坏过程的影响,发现胶凝含蜡原油在恒应力下的屈服是一个蠕变过程,应力越大,屈服时间越短,当应力小于临界屈服应力时,结构不会屈服。在连续增加剪切应力条件下,加载速率越大,屈服时间越短,屈服时应力越大。剪切应力和作用时间是导致粘弹性结构屈服的两个关键因素,较大应力在较短时间使结构屈服,较小应力则需要较长的时间使结构屈服。(4)针对胶凝含蜡原油蠕变的阶段性特征,引入损伤变量,将时间和应力作为应变的变量,建立了含蜡原油粘弹性蠕变模型,即建立?(t,?)函数,结果表明预测值和实验值相吻合,该模型可以准确描述含蜡原油屈服破坏过程。在已建立的胶凝含蜡原油非线性蠕变模型的基础上建立了剪切应力连续增加条件下的应变-时间-应力变化速率模型,即建立?(t,?)函数,结果表明该模型误差小,可以较好描述应力连续增加条件下粘弹性结构的屈服过程。该模型在含蜡原油领域有较好的应用前景。
[Abstract]:In this paper, the basic physical properties and Rheological properties of two kinds of waxy crude oil in Changqing have been studied by means of Rheological measurement and DSC method. The formation of Viscoelastic structure and the characteristics of yield failure process of waxy crude oil have been analyzed and discussed in detail, and based on the damage variable theory, A creep model which can describe the whole process of yield failure of Viscoelastic structures under the condition of constant stress and continuous increasing stress is established. The main contents of this paper are as follows: (1) the two kinds of Changqing oil samples are typical waxy crude oil, colloid, asphaltene content is not high (less than 1.3% and 0.027%, respectively), the density is small (both less than 0.84g/cm3), The wax content is high (all > 11%), the freezing point is higher (24 鈩，

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