含蜡原油屈服特性的试验研究

使用高精度的控制应力流变仪,采用多种控制应力试验,探索了大庆原油屈服特性随加载条件变化的规律.通过蠕变和应力匀速增加两种试验,发现胶凝原油屈服应力对测量条件如应力加载时间和应力加载速率等具有依赖性,但胶凝原油的屈服应变不随测量条件变化,从而进一步验证屈服应变的客观存在性,认为屈服应变可作为胶凝原油结构屈服的判据.通过蠕变、应力匀速增加、振荡剪切应力增加和恒剪切率等试验,对胶凝原油的屈服应变展开了研究.结果表明,胶凝原油的屈服应变随胶凝强度增加而减小.通过应力匀速增加试验对胶凝原油的屈服特性进行研究,发现对较低胶凝强度的原油存在应变软化现象.     

大型浮顶油罐温度场数值模拟

大型浮顶油罐温度场的准确预测对于原油的战略和商业储备均有着重要的意义。油罐中温度场受大气温度、罐壁保温层厚度与热导率、太阳辐射强度、罐底土壤物性、油品物性等因素的影响。本文考虑以上众多因素的影响，建立了二维大型浮顶油罐温度场预测模型，开发了将浮舱区、油品区、土壤区及罐壁和保温层耦合求解的SIMPLE算法程序。研究了太阳辐射、保温层厚度等因素对油品温度的影响，并将计算结果与现场测试数据进行了对比，发现本模型的预测结果与实验结果吻合良好。     

管输过程中加剂原油流动参数的预测

管输过程中加剂原油的流动性受剪切和热力条件影响,对其进行准确的模拟与预测有重要的理论意义和应用价值。本文结合流体力学能量方程,运用能量耗散理论,在室内模拟试验与现场测试的基础上,建立了原油加剂并在65℃处理后凝点、粘度与管输过程中的定性温度、能量耗散关系的数学模型。通过预测结果与现场实际运行结果的对比,证明此数学模型是可靠的,能够模拟现场实际运行工况。     

长距离管输添加降凝剂含蜡原油模拟试验

通过在试验环道及仪器上进行的长距离管输添加降凝剂含蜡原油模拟试验，研究多次过泵剪切及管流剪切对加剂原油低温流动性的影响，分析环道试验所测管流粘度与旋转粘度计测量结果的对比关系。     

幂律流体在圆管内湍流流动剪切率的近似计算

根据剪切率和能量耗散率的定义，建立了幂律流体湍流剪切率与能量耗散率的关系式。参照文献上对不可压缩牛顿流体湍流能量耗散率的近似算法，提出了一种幂律流体管内湍流能量耗散率的近似算法，从而得到了幂律流体管内湍流剪切率的实用近似算式，再利用湍流剪切率与脉动流剪切率的关系即可得到脉动流剪切率。计算得到的湍流剪切率分布及其随流动特性指数变化的特征与已知规律相符。     

天然气管网韧性保供问题及其研究展望

天然气的供应保障对经济发展与社会稳定至关重要。天然气保供是资源、管网、需求上、中、下游一体化的复杂系统工程。国内外对天然气管网可靠性已开展了系列研究。但是,对于大规模复杂系统,基于概率安全思想的可靠性评价方法存在容易稀释小概率、高后果极端风险的本质缺陷。借鉴电网、供应链、交通运输等复杂系统的研究和实践,提出了天然气管网韧性保供的概念,即在可靠性基础上,增加管网系统脆弱性和系统经受干扰后恢复至既定功能的能力（恢复力）评价;总结了天然气管网和电网等复杂系统可靠性、脆弱性和恢复力研究的现状、存在问题和发展方向;同时指出,大数据、人工智能技术将助推天然气管网韧性保供理论的发展,使其成为智能化与市场化变革大背景下智慧管网技术的重要理论基础。     

胶凝含蜡原油屈服时间研究

针对胶凝含蜡原油的屈服规律问题,定量描述了应力加载速率与屈服时间之间的关系.在控制应力模式下,使用RS150流变仪对胶凝大庆原油、北疆原油和吐哈原油等3种含蜡原油进行了应力阶跃式加载和应力匀速加载两种作用方式下的屈服特性实验.发现对于胶凝含蜡原油,随应力加载速率的减小屈服时间单调增加,数据回归分析表明二者之间存在相关性很好的幂函数关系.在此基础上提出了描述胶凝含蜡原油应力加载速率与屈服时间之间的关系式,结合量纲分析对该式的物理意义进行了分析.利用国内外文献中的不同胶凝含蜡原油的实验数据对该式进行了验证,结果表明该式具有通用性.     

Simulation of pipelining pours point depressant beneficiated waxy crude oil through China West Crude Oil Pipeline

Flow properties of waxy crude oils,particularly the beneficiated waxy crude oils,are sensitive to shear history that the crude oil experienced,called the shear history effect.To simulate this shear history effect accurately is vital to pipeline design and operation.It has been demonstrated by our previous that the energy dissipation or entropy generation due to viscous flow in the shear process is a suitable parameter for simulating the shear history effect.In order to further verify the reliability of this approach,experimental simulations were conducted for three PPD-beneficiated waxy crude oils transported through the China West Crude Oil Pipeline,a most complicated long-distance-crude-oil-pipeline technically and operationally so far in China.The simulations were made by using a stirred vessel and with the energy dissipation of viscous flow as the shear simulation parameter.Comparison between the flow properties of crude oils obtained from field test and experimental simulations,it is found that the gel points and viscosities from experimental simulations are in good agreement with the field data.     

Some advances in crude oil rheology and its application

Waxy crude oil exhibits complex shear-and-thermal-history-dependent non-Newtonian behaviors.In the past 10 years,driven by the petroleum industry,crude oil rheology has been an active field.Studies on crude oil rheology have been passing a way from simply relying on rheological measurements,through quantitative experimental simulation of shear and thermal history effects in pipelining,to recent development of correlation between flow properties and shear and thermal history.Currently,the study is toward quantitative inquiry of relations between the rheological behaviors and micro-structures of wax crystals as well as oil compositions.Advances achieved by the author’ team are summarized,including simulation of the thermal and shear history effects,correlations and computation of flow properties,fractal characterization of morphology and structure of wax crystals,relations of rheological behaviors to fractal dimension and oil compositions,and the most successful example of the application of rheology in crude oil pipelining.Future studies are prospected.     

基于滞回环的含蜡原油触变模型评价

触变性是含蜡原油的一个重要流变特性,对输油管道停输再启动过程的水力特性及安全性至关重要。通过实验,研究了4种含蜡原油在剪切速率先呈线性增大后呈线性减小这一循环加载条件下的滞回环特性。利用最小二乘原理,分别对剪切速率循环一次得到的单一滞回环和剪切速率变化率不同的多个循环得到的多个滞回环进行了拟合。用平均偏差作为统计指标,对8个触变模型进行了评价。结果表明,基于Cheng的含蜡油品中存在完全可逆和完全不可逆两类结构,在Houska模型的基础上建立的模型最适合于描述含蜡原油的滞回环特性。