含蜡原油管道安全经济输送的基础问题研究

Most oils produced in China are waxy crude oil. The existence of wax in oil leads to a range of issues including poor flow ability at low temperatures, wax deposition with temperature difference between oil and pipe wall, a certain degree of gelation after shutdown and high energy consumption with heated oil transportation, which brings great challenge to the safe and economic operation of waxy crude oil pipeline. Aiming at meeting the urgent need of safety transport assurance, this project plans to finish the tasks as follows. The quantitative characterization of the strain change rule of waxy crude oil gelling system after loading will be proposed, meanwhile the description of viscoelasticity-thixotropy constitutive relation will be given for waxy crude oil gelling system at low temperatures. Based on shear energy analysis of flow field, the wax deposition model can be established, thus the quantitative interpretation of the competition mechanism of dispersion and scaling will be accomplished. The heat-transfer mechanism of wide phase-change interface solidification after shutdown and the hydraulic characteristics mechanism of viscoelasticity-thixotropy oil after restart will both be presented. The research on the irreversible exergy transfer characteristics and mechanism will be made, and then the exergy consumption index system for pipeline transportation process will be established. A compound depressant will be developed to inhibit the anti-depressing effect of resin, and its interaction mechanism with paraffin be explored. This project can merge the related theory of multi-subject and promote the theory of cross subject forward. Simultaneously, these results will provide theory instruction and technical support to develop scientific pipeline plan, increase transportation efficiency and reduce transportation cost.

我国所产原油大多为含蜡原油。蜡的存在导致原油低温流动性差、油壁温差下出现沉积、停输后产生一定强度胶凝及必须加热输送能耗高等问题，给含蜡原油管道的安全经济运行带来较大挑战。本项目针对原油运输安全保障所面临的迫切需要，拟量化表征含蜡原油胶凝体系受载后应变变化规律，给出同时描述低温含蜡原油胶凝体系黏弹—触变特征的本构关系；建立基于流场剪切能分析的管输蜡沉积模型，定量化解释弥散和剥落两种效应的竞争机制；阐明停输过程基于宽相变界面凝固的传热机理，弄清具有黏弹-触变性原油再启动的水力特性及其机理；研究原油管输过程不可逆火用传递特性及机理，构建原油管输过程的火用传递能耗评价指标体系；开发能够抑制胶质抗降凝作用的复合型降凝剂，探求其与石蜡的作用机理。该申请项目具有融合多学科相关理论，推进交叉边缘学科向前发展的作用；研究成果可为石油企业制订科学管输方案、提高输送效率、降低输送成本提供理论技术支持。

我国所产原油大多为含蜡原油。蜡的存在给含蜡原油管道的安全经济运行带来较大挑战。本项目运用流变学、传热学和热力学等的相关理论和方法完成了以下内容：建立了描述低温含蜡原油胶凝体系黏弹—触变特征的力学模型与数学模型，研究了不同剪切时机、强度、热处理温度、降温速率等对凝点等流变特性的影响规律和机理，给出了初次热处理和重复热处理时机的选择原则与方法；研究了剪切效应对蜡晶形态、结构及其聚集行为的影响机理，剖析了含蜡原油管输流场中剪切能的概念及其作用范畴，建立了以剪切能作为函数的原油管输蜡沉积模型，并给出了剪切弥散与剥离效应对蜡沉积作用的定量化描述，提出了能够充分揭示含蜡原油管输剪切流场中蜡沉积过程与机理的方法；开展了含蜡原油微观析蜡特性研究，提出了“聚结点”及“宽相界面分区法”的概念，给出了凝固传热的物理描述，建立了管内原油—管道—环境耦合作用的含蜡原油停输管道热力模型并对其进行了验证及完善，剖析了不同环境参数及停输工况对管道内原油流场、温度场变化规律的作用效果及机制，完善了原油相变传热机理及内涵；推导了含蜡原油热力学㶲函数的普遍化表达式，分析了不可逆输送过程熵产与㶲损机制，并剖析了管输过程不同形式㶲之间相互转换和传递的耦合作用机制，分层次揭示了㶲传递多场耦合的输油机理，确定了有效㶲耗与无效㶲耗的概念与计算方法，筛选并建立了管输原油的㶲传递能耗指标评价体系；合成了一系列脂肪酸酰胺类化合物，与EVA复配后，实验表明脂肪酸三乙烯四酰胺类降凝剂助剂的降凝效果相比脂肪酸多乙烯多酰胺类降凝剂助剂的效果更佳，合成了一系列马来酸对称双链化合物并接枝到EVA化合物上，利用RAFT法，将三硫代碳酸酯链转移剂作为链转移剂，得到了不同分子量的嵌段共聚物，利用十八烷基三甲基氯化铵对纳米蒙脱土进行有机改性，并制备了NEVA。以上成果可为石油企业制订科学管输方案、提高输送效率、降低输送成本，提供理论及技术支持。