M油田群含蜡原油管道低输量下的流动保障研究

发布时间：2019-05-29 11:49

【摘要】：近年来M油田群产量衰减迅速,目前油田外输管线输量低于设计输量,并有一直向下衰减的趋势,管道热力条件变差,有可能出现凝管、管道特性进入不稳定工作区的风险。本文针对M油田群中心处理平台至陆上输油终端外输管线面临的低输量工况进行流动保障研究,分析管内原油在低输量下的水力热力特性、结蜡规律,制定合理的安全运行方案,研究停输再启动过程,为实现外输管道在低输量工况下安全平稳运行和科学管理,提供重要理论支撑和技术指导。主要研究内容如下:(1)选取中心平台输出的原油为实验油样,通过室内实验对所选油样进行物性测定。考虑到含蜡原油在加热输送过程中流型流态、物性参数变化以及摩擦热和析蜡潜热的影响,分析了含蜡原油加热输送管道的流动特性,建立了含蜡热油管道水力热力计算模型和临界安全输量计算模型。(2)利用普适性结蜡模型的方法回归出M油田群外输原油蜡沉积速率公式,对不同运行条件下管道沿线蜡沉积层厚度进行了预测,分析了不同工况下管线内蜡沉积规律,得出输量和温度对沿线蜡沉积厚度的影响较大,并且管内蜡沉积并不是均匀分布的,主要集中在陆管段呈现不均匀分布状态。(3)为了避免逐渐变差的热力条件导致管内结蜡层过厚造成卡堵,针对M油田群含蜡原油外输管线进行了清管方案比选。通过对经济清管模型的计算,得出经济清管模型并不适用于M油田外输管道。由于M油田田田外输管道结蜡主要集中在局部管道并且呈不均匀分布,通过对管道运行期间沿线压降变化率的模拟,发现管道结蜡段压降变化率比较明显,而入口压降变化率很小。以管道局部压降变化率作为清管周期的判别条件,制定了不同运行工况下的清管方案。(4)为了避免低输量管道进入不稳定工作区,重点分析了掺水输送工艺和掺降凝剂输送工艺。针对掺水输送工艺建立了 M油田外输管道掺水输送模型,以管道最低出口温度和入口压力满足管道最大承压为条件,通过掺水原油水力热力计算得出了不同工况下M油田外输管道最小掺水量。针对掺降凝剂输送工艺,通过实验从可供选择的降凝剂中筛选出效果最好的试剂。基于安全经济输送的原则,通过实验得到了M油田外输原油不同加剂量的改性效果,制定了不同输量、季节添加不同剂量降凝剂的运行方案。(5)建立M油田外输管道停输再启动数学模型,用有限容积法和热力特征线法对数学方程进行了离散,并编制了计算软件。通过软件对管线在不同条件下的停输和再启动过程进行了模拟分析,并计算了不同工况下的安全停输时间;根据规定的事故抢修时间确定了不同工况下的最低入口温度。
[Abstract]:In recent years, the production of M oil field group has decayed rapidly. At present, the pipeline transportation volume outside the oil field is lower than the designed transportation volume, and there is a tendency to decline all the time. The thermodynamic conditions of the pipeline become worse, and there may be the risk of condensate pipe and pipeline characteristics entering the unstable working area. In this paper, the flow guarantee of the external pipeline from the central treatment platform of M oil field group to the onshore oil terminal is studied, and the hydraulic and thermodynamic characteristics and waxing law of the crude oil in the pipeline under the condition of low transportation capacity are analyzed. The reasonable safe operation scheme is worked out, and the shutdown and restart process is studied, which provides important theoretical support and technical guidance for the safe and stable operation and scientific management of the external pipeline under the condition of low transportation volume. The main research contents are as follows: (1) the crude oil exported from the central platform is selected as the experimental oil sample, and the physical properties of the selected oil sample are measured by laboratory experiments. Considering the flow pattern and physical parameters of waxy crude oil in the process of heating transportation, as well as the effects of friction heat and wax precipitation latent heat, the flow characteristics of waxy crude oil heating pipeline are analyzed. The hydraulic thermodynamic calculation model and critical safe transportation model of waxy hot oil pipeline are established. (2) the formula of wax deposition rate of external transportation crude oil in M oil field group is regained by using the method of universal waxing model. The wax deposition layer thickness along the pipeline is predicted under different operating conditions, and the wax deposition law in the pipeline under different working conditions is analyzed. It is concluded that the transportation volume and temperature have a great influence on the wax deposition thickness along the pipeline. And the wax deposition in the tube is not uniform distribution, mainly concentrated in the land pipe section showing an uneven distribution state. (3) in order to avoid the gradual deterioration of thermal conditions resulting in excessive thickness of waxing layer in the tube resulting in blockage, The cleaning scheme of waxy crude oil pipeline in M oil field group is compared and selected. Through the calculation of the economic cleaning model, it is concluded that the economic cleaning model is not suitable for the external pipeline of M oil field. Because the wax deposition of the external pipeline in M oil field is mainly concentrated in the local pipeline and shows uneven distribution, through the simulation of the change rate of pressure drop along the pipeline during the operation of the pipeline, it is found that the change rate of pressure drop in the waxing section of the pipeline is obvious. However, the change rate of inlet pressure drop is very small. Taking the change rate of local pressure drop of pipeline as the criterion of pigging cycle, the cleaning scheme under different operating conditions is worked out. (4) in order to prevent the pipeline from entering unstable working area, The water mixing transportation process and pour point depressant transportation process are analyzed in detail. According to the mixed water transportation process, the mixed water transportation model of M oil field external pipeline is established, and the minimum outlet temperature and inlet pressure of the pipeline meet the maximum pressure of the pipeline. The minimum water content of M oil field pipeline under different working conditions is obtained by hydraulic and thermodynamic calculation of mixed crude oil. According to the transportation process of adding pour point depressant, the best reagent was screened out from the optional pour point depressant through experiments. Based on the principle of safe and economic transportation, the modification effect of different dosage of external crude oil in M oil field is obtained by experiment, and different transportation volume is worked out. The operation scheme of adding different doses of pour point depressant in season is added. (5) the mathematical model of shutdown and restart of external pipeline in M oil field is established, the mathematical equation is discretized by finite volume method and thermodynamic characteristic line method, and the calculation software is compiled. The shutdown and restart process of pipeline under different conditions is simulated and analyzed by software, and the safe shutdown time under different working conditions is calculated, and the minimum inlet temperature under different working conditions is determined according to the specified accident emergency repair time.
【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

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