析蜡潜热对架空管道停输介质温度分布影响研究

研究热油管道的停输介质的径向温度场分布,对确定安全停输时间具有重要的指导作用.由于考虑析蜡潜热的影响能更准确的描述热油管道停输介质的温度分布,建立了架空热油管道停输径向传热物理模型和数学模型,并用FLUENT软件模拟了架空管道停输温降过程中径向温度场分布.该方法能够准确模拟原油凝固过程中固液相界面的位置,模拟结果更符合...     

Numerical simulations of temperature field of an oil pipeline when transportation is stopped

对于高凝点原油,管线停输后很容易出现凝管现象,确定安全停输时间是保证安全启动的重要条件.原油的储热能力,管道系统向周围土壤传热能力及土壤的温度场分布决定着管线安全停输时间,研究热油管线停输期间温降规律显得尤为重要.利用CFD软件,在非稳态传热条件下,模拟出不同停输时刻管道温度场分布及温降曲线.结果表明:停输初期管内原油自然对流传热强烈,温度下降较快,后期下降缓慢,这种变化趋势和传热方式的变化相对应.当停输21 h时,原油温度降为38 ℃(高于凝点3 ℃),即安全停输时间为21 h.     

回填土质对埋地热油管道传热影响的研究

针对不同导热系数的土样回填管沟,忽略管道轴向温降建立二维非稳态传热模型,环境温度采用周期性边界条件。利用有限容积法,对方程进行离散,数值模拟了管道投产第一年内正常运行非稳态传热过程,同时应用"焓-多孔度"技术,并考虑原油凝固潜热对温降的影响,数值模拟了管道停输非稳态温降过程。结果表明:采用导热系数相对较小的土质回填管沟,管壁及保温层外壁热流密度明显减小,而且回填区温度较高散热较慢,由计算的安全停输时间可知,回填土质导热系数越小安全停输时间越长,模拟结果符合实际。     

含蜡原油热输管道轴向温降计算在大港石化公司的应用

根据含蜡原油在三个不同温度区域的比热容表达式,从能量平衡关系式出发,推导出了含蜡原油热输管道轴向温降的计算公式,并与苏霍夫温降公式进行了比较。得出了实际运行情况下,原有的外输油起点温度范围已不再是最佳的选择。应用本文提供的计算方法予以调整,可以大大降低不必要的能量消耗。     

埋地原油管道停输期间温降及原油凝固传热模型及数值模拟

假设原油凝固区域为一固相和液相组成的动态多孔介质区域,建立了土壤、管道能量方程与原油质量、动量和能量方程相互耦合的传热模型,并对埋地原油管道停输温降过程进行了数值模拟.数值模拟结果能够合理解释停输期间温度场、凝固界面和自然对流规律.     

加热炉辐射段热负荷的选择

我国“三高”(高粘度、高含蜡、高凝固点)原油在油田集输、储存和管道长距离输运过程中,需要加热,以降低原油的粘度,并使原油温度保持在凝固点以上。因此,在油田集输和长输管道沿线需建设多个加热炉。目前运行中的加热炉多数是70年代末和80年代初设计建造的“方箱式”加热炉,其设计方法是采用Lobo—Evans法。 “方箱式”加热炉把换热区域分为辐射段(即燃烧室或称炉膛)和对流段两部分。     

含蜡原油凝点和倾点的实验研究

凝点、倾点是以温度表征原油低温流动性的条件性指标,是影响管输安全性和经济性的关键因素。中国一直以凝点作为控制原油输送温度的一个重要参数,而国际上普遍采用倾点。着重对含蜡原油凝点和倾点进行对比实验研究。     

油油换热器投运及节能效果的探讨

为实现节能减排,西部原油管道在首站原有加热系统的基础上增加了油油换热器装置,针对投运过程中遇到的问题,如泵不满足启泵条件、部分高凝油进入管道等,提出了相应的解决措施.同时,探讨油油换热器装置投用前后对管道的影响,如停输出站油温下降或启输油温回升速度对外输物性的影响,冬季运行加热炉节能效果等.运行结果表明:较投用前停输温降速度慢,出站油温变化不大,节能效果显著,备用加热炉增加,更有利于管道的冬季运行.     

东海油气资源早期开发中采用海底管道输送天然气的经济性

一、问题的提出海上油气田所产原油的输送,可用船运或海底管道输送,而所产天然气的输送,几乎都用海底管道输送。海底管道输送天然气始于1947年的墨西哥湾,60～70年代盛行于英国北海,技术成熟,运行方便可靠,运行费低,具有管输技术所有的优点。但投资高昂,尤其是海底铺设,更使人望而生畏。因此,在     

原油管输不可逆过程火用的传递和转换规律研究

基于不可逆过程热力学的基本理论,探讨了原油管输过程各不可逆过程的强度量势场梯度驱动力作用下的火用流传递现象,结合原油管道输送过程的基本场平衡方程组和普遍化热力学体系的火用平衡动力学方程,推导了管输过程的热火用和压火用传递和转换方程,进一步建立管输过程的总火用传递方程。以某原油管道为例,对管道输送过程进行数值分析得到管输过程中热火用和压火用的传递和转换火用流分布规律,为将火用的传递转换规律应用到管道节能体系中提供理论基础和合理依据。     

Further study on the thermal characteristic of a buried waxy crude oil pipeline during its cooling process after a shutdown

Since the temperature drop of waxy crude oil after a shutdown determines whether the pipeline is able to restart successfully or not, it is necessary to calculate the temperature drop and clarify the characteristic of the thermal process of waxy crude oil pipeline after the shutdown. However, the relevant techniques proposed in the previous researches for this calculation are not accurate enough, due to the complex phase change, non-Newtonian behavior of the fluid, and the transition of different heat transfer mechanisms involved within the physical problem. Therefore, in a companion piece to this paper, a general and accurate mathematical model was proposed for the phase-change heat transfer of waxy crude oil. In this paper, the mathematical model of the waxy crude oil pipeline system after its shutdown is established, based on the phase-change heat transfer model proposed in the companion piece, and the numerical procedure is established for the calculation of the model. With the proposed techniques, the thermal process of the shutdown of waxy crude oil is investigated in detail, and the temperature drop characteristic is clarified on the level of heat transfer mechanism. The research will provide theoretical support for the establishment of shutdown scheme and thermal preservation method for waxy crude pipeline.     

A new general model for phase-change heat transfer of waxy crude oil during the ambient-induced cooling process

The thermal process during shutdown (a stoppage state of the pipeline), of which the essence is an irregular phase-change process accompanied by natural convection, non-Newtonian behavior, and sometimes turbulence, is a critical problem in crude oil transportation engineering. An accurate calculation of the thermal process during shutdown is more than necessary for the safety of crude oil pipeline; however, it faces some challenges due to the complexity of the phase change. In this study, the phase change of waxy crude oil during the cooling process is divided into four stages, which includes a pure liquid natural convection, solid/liquid dispersion natural convection, coexistence of dispersion system natural convection and porous media natural convection, and pure porous media convection, according to different heat transfer mechanisms on different stages. Based on this division, a general phase-change heat transfer model is proposed for the thermal calculation of waxy crude oil during shutdown. Compared with the previous research, this model appropriately includes the influences of non-Newtonian behavior, phase evolution as well as turbulence. With the proposed model, the temperature drop characteristic of a sample pipeline is analyzed and the influencing factors are investigated.     

Pipeline Heating Method Based on Optimal Control and State Estimation

In the production of oil and gas in deep waters, the flow of the produced hydrocarbon through pipelines is a challenging problem. High hydrostatic pressures and low seabed temperatures may result in the formation of solid deposits, which in critical operating conditions like unplanned shutdowns can cause pipeline blockages. One of the possible methods for flow assurance, which can be jointly used with other approaches, is to heat the pipeline. This design concept aims at heating the produced fluid, if needed, to above a safe reference temperature in order to avoid the formation of solid deposits. The objective of this article is to utilize the particle filter method for the solution of a state estimation problem, in which the state variables are considered as the transient temperatures within a pipeline cross section. In addition, the minimum temperature in the region, predicted with the particle filter method, is used in the optimal control theory as a design tool for a typical heating system, during simulated shutdown conditions. An application example is presented to illustrate the control of the minimum temperature in the region, from an observer based on the particle filter method, where temperature measurements are assumed to be available on the external surface of the pipeline.     

The Stability Criterion Model and Stability Analysis of Waxy Crude Oil Pipeline Transportation System Based on Excess Entropy Production

Based on the theory of non-equilibrium thermodynamics, considering the dynamic effect of molecular diffusion and the change in thermodynamic parameters caused by wax precipitation, the phenomenological relations of different thermodynamic “force” and “flow” interactions were derived. The corresponding thermodynamic model of a waxy crude oil pipeline transportation system was built, and then, the excess entropy production expression was proposed. Furthermore, the stability criterion model of the pipeline transportation system was established on the basis of Lyapounov stability theory. Taking the oil pipeline in Daqing oilfield as an example, based on the four parameters of out-station temperature, out-station pressure, flow rate and water content, the stable and unstable regions of the system were divided, and the formation mechanisms of the two different regions were analyzed. The experimental loop device of wax deposition rate was designed, and then, the wax deposition rate under the four parameters was measured. The results showed that the stable region of the wax deposition rate fluctuation was basically in accordance with the stability region analyzed by the criterion model established in this paper, which proved that the stability criterion model was feasible for analyzing the stability of the waxy crude oil pipeline transportation process.     

废弃钻井液不落地处理冬季低温生产保障方案设计

针对废弃钻井液不落地处理冬季施工过程中存在钻井液冻凝,设备停机后启动困难,压滤机液压系统油管线温度低、流动性差导致的控制动作缓慢或失灵,钻井液罐与地面冻结无法搬运,钻井设备卫生清洁困难等难题,从废弃钻井液处理方式、油田所在区域、钻井周期等实际情况出发,设计切实可行的冬防保温方案,确保冬季施工设备灵活好用、管线畅通、废弃钻井液无冻凝,保证废弃钻井液不落地处理有序进行。该方案在大庆油田、冀东油田等多口井应用,实践效果良好,解决了因废弃钻井液不落地处理冬季施工过程中钻井液冻凝、设备故障而造成的钻井延误问题。