【作者】 章博；

【导师】 陈国明；

【作者基本信息】 中国石油大学 ， 安全技术及工程， 2010， 博士

【摘要】 本文结合“大型油气田及煤层气开发”国家科技重大专项“高含硫气藏安全高效开发技术研究”项目(2008ZX05017)所属课题“高含硫气田集输工艺与安全控制技术”,系统开展高含硫天然气集输管道腐蚀与泄漏定量风险研究,通过理论研究、数值计算和计算机仿真,在高含硫天然气集输管道腐蚀因素分析、腐蚀泄漏风险定量预测、腐蚀泄漏预警研究、腐蚀泄漏风险评价指标体系及方法、腐蚀泄漏检测优化等方面取得较大的研究进展。主要研究成果总结如下:1高含硫天然气集输管道腐蚀因素分析高含硫天然气集输管道腐蚀影响因素主要为内腐蚀、埋地金属腐蚀和大气腐蚀。内腐蚀影响因素包括产品腐蚀和管道内防护;埋地金属腐蚀包括地下环境、阴极保护和包覆层;大气腐蚀包括大气暴露、大气类型和包裹层等因素。分析流速、压力、温度等管道运行参数对内腐蚀的影响,用灰色关联度方法辨识内腐蚀的主要影响因素为硫化氢含量。并用事故树方法对高含硫天然气集输管道腐蚀因素进行系统分析,得出各因素的结构重要度及导致腐蚀失效发生的最小割集。2高含硫集输管道腐蚀泄漏风险定量预测应用CFD(Computational Fluid Dynamics)方法定量预测高含硫天然气集输管道泄漏后果,构建集气站高含硫天然气泄漏CFD模型,并探讨网格依赖性、风场一致性和模型有效性对CFD模拟的影响。实现对多种工况高含硫天然气泄漏后果的预测。预测结果表明,各种工况下人员中毒风险较大,且明显高于可燃气体燃爆风险。提出复杂山区地形CFD网格生成技术。通过处理待建模地区的GIS数据,获取分别对应于经度、纬度和海拔高度的坐标,确定参考点并转换为平面直角xyz坐标并以此为基础,构建真实地形CFD网格。实现对高含硫天然气复杂山区地形扩散后果的真实预测,并以某泄漏工况为例,预测山区地形高含硫天然气泄漏后30 min内的扩散后果。提出CFD与中毒剂量反应模型结合的人员急性中毒定量评估技术,通过CFD计算泄漏毒气的实时浓度场,根据浓度场和暴露时间确定人员暴露剂量,由剂量反应模型确定人员死亡百分比。对高含硫天然气集气站人员中毒风险进行定量分析,以某泄漏工况为例,评估人员静止不动和在应急撤退过程中的中毒死亡百分比。3高含硫集输管道腐蚀泄漏预警方法提出高含硫天然气集输管道腐蚀穿孔预警技术方案,包括集输管道腐蚀风险辨识、腐蚀风险预测预警及腐蚀穿孔应急控制三个阶段,并对各阶段适用的技术方案进行详细分析,可为相关预警及应急提供可靠的决策依据。建立可用于预警系统的多种腐蚀速率预测数学模型,包括灰色模型、BP神经网络模型、Monte-Carlo模型、灰色神经网络模型,并对各种预测模型的预测精度进行对比,可为腐蚀泄漏预警提供决策参考。提出基于剩余强度评估的腐蚀降低管道输送能力预警方法,明确腐蚀管道预警事件分级标准及相应预警阈值。4高含硫集输管道腐蚀泄漏风险评估指标体系构建高含硫天然气集输管道腐蚀风险评估指标体系,由腐蚀指数评估管道腐蚀相对风险。腐蚀指数包括大气腐蚀指数、内腐蚀指数和埋地金属腐蚀指数三部分,每部分又包括若干二级指标和三级指标。给出各指标的详细评分标准,各项指数累计评分之和即为管道腐蚀相对风险,范围0~100分,分值越高腐蚀风险越小。为减小评分法的主观不确定因素,引入层次分析法根据各评分专家的知识背景、工作经历、专业特长等因素来确定评分专家对内腐蚀指数、大气腐蚀指数和埋地金属腐蚀指数的评分权重。通过权重与各专家评分值相乘并累计相加得出最后的腐蚀指数评分结果,增加了腐蚀指数评分法的客观性。探讨管道腐蚀相对风险和绝对风险的关系,建立腐蚀指数相对风险值与腐蚀速率及可能导致腐蚀穿孔失效时间的对应关系,使得腐蚀指数风险评估结果的直观性得以增加。5高含硫集输管道腐蚀泄漏检测优化提出基于CFD的高含硫天然气泄漏检测优化方法。以高含硫天然气集气站为例,研究气体检测报警仪的布置优化,构建集气站CFD模型,并将站内气体检测报警仪设置为模型中的监测点,通过对天然气泄漏及扩散过程的数值模拟获得各监测点的甲烷和硫化氢浓度。据此对可燃气体检测报警仪布置高度、可燃及有毒气体检测报警仪探测有效性及反应时间进行了分析,提出了高含硫气田集气站气体检测报警仪布置优化的建议。更多还原

【Abstract】 Quantitative risk research on corrosion and leakage of high sulfide natural gas gathering pipeline was systemically conducted in this dissertation, which is a part of the sub-topics‘gathering process and safety control techniques in high sulfide gas field’of national science and technology special project“Large-scale oil & gas fields and coal bed gas Exploitation”(No. 2008ZX05017).Through theoretical research, numerical calculation and computer simulation, progress were made in these aspects including the corrosion factors of high sulfide natural gas gathering pipeline, quantitative risk prediction on corrosion and leakage, pre-warning technique on corrosion and leakage, risk evaluation index system and measures of corrosion and leakage, inspection method optimization on corrosion and leakage and so on. The main works are summarized as follows:1 Analysis on Corrosion Factors of High Sulfide Natural Gas Gathering PipelineThere are three types of corrosion factors in high sulfide natural gas pipeline including internal corrosion, buried metal corrosion and atmospheric corrosion. The internal corrosion mainly includes products corrosion and inside corrosion protection of the pipe; the buried metal corrosion mainly includes underground environment factors, cathodic protection and coating; atmospheric corrosion mainly includes atmospheric exposure, atmospheric type and wrapped layer and so on. The influence of pipeline operation parameters such as flow rate, pressure and temperature to the internal corrosion was analyzed. Hydrogen sulfide concertration, the main influence factor leading to internal corrosion was identified based on grey relevance method. Detailed analysis on corrosion factors of the high sulfide gas pipeline was conducted by means of Fault Tree Analysis, the structure importance degree of each factor and the minimal cut sets causing corrosion failure were figured out.2 Quantitative Risk Prediction on Corrosion and Leakage of High Sulfide Natural Gas Gathering PipelineQuantitative risk prediction for the consequence caused by leakage of high sulfide gathering pipeline was systematically conducted using Computational Fluid Dynamics(CFD) method. The CFD model of high sulfide natural gas leakage in gas station was established. Also the influence of grid dependency, horizontal homogeneity of Atmospheric Boundary Layer, and validity of model were take into consideration. The prediction of the consequences as result of leakage of high sulfide natural gas under a variety of working conditions was achieved. The prediction results show that the risk of individual poisoning was obviously higher than the risk of explosion of inflammable gas.The technic of computation grid generation over complex mountainous terrain was presented. First, GIS data of pre-modelling terrain was dealed to get the coordinate of the longitude, the latitude and the altitude. Then the reference point was fixed meanwhile the coordinates were transformed to planimetric rectangular coordinates with a XYZ format. Finally the CFD mesh of real terrain was established to make realistic prediction of dispersion consequence in result from the high sulfide natural gas leakage over complex mountainous terrain. A case study under some working condition has been carried out to making prediction for the dispersion rules of high sulfide natural gas accidental leakage over complex mountainous terrain in 30 min.A CFD numerical simulation and dose–response model combined approach has been proposed for quantitative analysis of acute toxic gas exposure threats. First the toxic gas concentration distribution in time and space was got by CFD simulation, then toxic dose according to gas concentration and exposure time was calculated. Evaluating exposure personnel death percentage according to dose reaction model is the last step. Quantitative risk analysis of individual poisoning in high sulfide natural gas station was conducted. An example of leakage under a certain working condition was studied to evaluate the personnel poisoning death percentage assuming workers stay at original exposure location without moving or make emergency evacuation.3 Pre-Warning Research on Corrosion and Leakage of High Sulfide Natural Gas Gathering PipelineThe technical flowchart of pre-warning system on corrosion and perforation of high sulfide natural gas gathering pipeline has been presented. The pre-warning contains three stages including gathering pipeline corrosion risks identification, corrosion risks prediction and pre-warning, corrosion and perforation emergency response and control. Detailed technical analysis of every stage has been conducted. This work could provide dependable references for the decision making of pre-warning and emergency responses in related areas.The prediction mathematical models under multiplicate corrosion rates for pre-warning system were set up including the grey model, BP neural network model, Monte-Carlo model and grey neural network model, which could provide dependable references for the decision making of pre-warning on corrosion and leakage.A remaining strength assessment based pre-warning method of corroded pipelines transmission capacity decrease was proposed. The classification standards and the corresponding thresholds of pre-warning incidents were established.4 Risk Assessment Index System on Corrosion and Leakage of High Sulfide Natural Gas Gathering PipelineThe relative risk of pipeline corrosion was assessed by corrosion index which includes atmospheric corrosion index, internal corrosion index and buried metal corrosion index. Each index contains some 2nd indicators and 3rd indicators. Detailed index scoring standards were given. Cumulative score of each index was the relative risk of pipeline corrosion, range from 0 to 100. The higher the score, the lower the risk of corrosion.To avoid the subjective uncertain factors in the scoring process, Analytic Hierarchy Process was introduced according to the factors such as the expert’s knowledge background, work experience and expertise to identify each expert’s scoring weight of internal corrosion index, atmospheric corrosion index and buried metal corrosion index. The weight multiplied the score and then was accumulated to get the final score of corrosion index in a more objective way.The relationship of pipeline relative and absolute risk was investigated. The correspondence of corrosion index relative risk, corrosion speed and the possible failure time of corrosion perforation was set up to increase the intuition on the risk evaluation result of corrosion index.5 Detection Optimization Research on Corrosion and Leakage of High Sulfide Natural Gas Gathering PipelineThe method of detection optimization on leakage of high sulfide natural gas was presented based on CFD. The layout of the gas detection and alarm instruments in a high sulfide natural gas station has been optimized by means of setting up a series of monitor points in CFD model. The methane and hydrogen sulfide volume fractions of monitor points were recorded by the simulation of natural gas release and dispersion process. The sensitivity to combustible gas detectors high and low level placement, validity and response time of both combustible and toxic gas detectors in large and small release rates were investigated. Then some advices about optimization of gas detection and alarm networks on high sulfide gas gathering station were provided.更多还原