酸性天然气管道量化风险评价方法研究

【作者】 杨洋；

【导师】 李长俊； 郭艳林；

【作者基本信息】 西南石油大学 ， 石油与天然气工程（专业学位）， 2013， 硕士

【摘要】 伴随着国家对天然气资源需求的扩大,酸性气田开发己成为我国重要的能源战略。管道运输是天然气运输的主要方式。酸性天然气因含有H2S、CO2等物质而具有强腐蚀性,恶劣的腐蚀环境使酸性天然气管道更容易发生腐蚀穿孔和破裂,不仅会造成巨大的经济损失和污染环境；还可能危及周围人员的人身安全,严重影响管道的正常生产。风险评价技术是识别和降低风险的一种有效方式,目前已经广泛应用于油气输送管道系统。酸性天然气管道与净化天然气管道不同：一方面酸性天然气管道由于腐蚀环境恶劣而具有更高的失效概率；另一方面,由于酸性天然气中含有的H2S具有毒性,因此酸性天然气管道的失效后果除了燃烧和爆炸以外,还要考虑毒性影响。基于以上分析,本文展开以下研究：(1)基于国内外净化气管道和酸性天然气管道失效数据的统计,分析了酸性天然气管道的失效模式和失效频率。采用通用的失效频率表示方法对川内酸性天然气管道失效频率进行了计算,并与国外同类数据进行比较分析。(2)基于气体扩散影响因素分析了酸性天然气的扩散过程。通过比较常用气体扩散模型的优缺点和适用范围,选择高斯模型进行扩散计算和后果面积计算。结合酸性天然气的定义和特点,分析了酸性天然气管道泄漏失效后果,确定酸性天然气管道的失效危害为燃烧热辐射损伤,爆炸损伤和中毒损伤。(3)利用喷射火火灾模型和高斯模型,对不同热辐射强度阈值和H2S浓度阈值下的影响面积进行了计算应用,并在相同热辐射阂值和H2S浓度阈值和大气环境下与API581推荐的面积计算方法进行了对比,验证了模型的可靠性。在喷射火模型中做出了火焰垂直燃烧的假设,并考虑了喷射火焰的高度的影响。在高斯模型中,采用API 581推荐的方法,将泄漏扩散面积视为椭圆形,毒性影响面积采用椭圆面积公式进行计算。(4)通过对酸性天然气的特点进行分析,得到酸性天然气管道量化风险评价方法,并以龙岗001-6井至001-7集气站管道为例进行了应用,并将计算结果与同等条件下的净化天然气管道进行了对比。对比发现,酸性天然气管道的失效概率、失效后果成本和风险均高于净化天然气管道。(5)利用高斯模型,对H2S浓度阈值15ppm和100ppm情况下的风险进行了计算。结果发现：安全阈值不同,得到的影响面积和后果成本也会不同。在15ppm的浓度阈值下,毒性影响面积大于燃烧影响面积,使得中毒经济损失在后果总成本中的比例增加。因而反映为随着天然气中H2S含量的增加,管道的风险升高。但是当浓度阈值为100ppm时,后果影响面积以燃烧影响面积为主,因而表现为随着天然气中H2S浓度的增加(烃类组分减少),燃烧影响面积减少,引起管道的风险降低。(6)对一类10户、二类20户和二类100户不同人口密度下的酸性天然气管道进行风险评价,结果发现：随着人口密度的增加,管道的风险随着增加。且H2S含量越高,风险增加的比例越大。在计算的H2S浓度(5%-20%)内,人口密度的增加并没有增加管道的风险等级。更多还原

【Abstract】 Along with the national increasing demand for natural gas resources, the development of sour gas field has become an important energy strategy. Pipeline transport is the main form of natural gas transportation. Soul gas is the gas which contains substances such as H2S, CO2 and others.The strong corrosion environment makes the transpotion pipeline more prone to corrosion perforation and rupture which not only causing huge economic losses and environmental pollution, but also may endanger the personal safety of staff and affect the normal production of the gas field. Risk assessment technique is an effective way both to reduce risk and to identify risk and now is widely used in oil and gas pipeline system.The soul gas pipeline and purified natural gas pipeline are quite different. On one hand the soul gas pipeline has a higher probability of failure due to the harsh corrosive environment, on the other hand, the soul gas contains H2S which is toxic.So in addition to the thermal radiation and explosion overpressure, the consequences of failure of soul gas pipeline also need to consider the impact of poisoning. Based on the above analysis, this paper mainly studies on the following aspects:(1)Based on the analysis of failure datas of the domestic and foreign purified gas pipelines and sour gas pipelines, the cause of failure and failure of probability of the soul gas pipeline are analyzed. The general failure frequency representation method is used to calculate the failure of probability of soul gas pipelines in Sichuan province and compared it with foreign data.(2) Based on the diffusion influence factors the soul gas diffusion process is analyze. Compared the advantages and disadvantages of commonly used gas diffusion models and Gaussian diffusion model is selected. Analyze the the consequences of failure and determine the the failure hazards of soul gas pipeline are thermal radiation injury, explosion injury and poisoning injury.(3)Jet fire model and Gaussian diffusion model are applied to calculate the affected area at different thermal radiation threshold and H2S concentration threshold. Comparison to verify the reliability of the models is made with the API 581 recommended calculation method at the same thermal radiation threshold and H2S concentration threshold. The jet fire model made the assumption that the flame is vertical and the height of the jet fire is took into account. The Gaussian diffusion model considers the leak diffusion area as ellipse which is recommended in API 581 and ellipse area formula is adupted.(4)By analyzing the characteristics of soul gas, the soul gas pipeline quantitative risk assessment model is obtained. Take Longgang 001-6 to 001-7 pipeline for example, the improved quantitative risk assessment model is applied. The result is compared with purified natural gas pipeline in the same condition. Comparison found that the probability of failure, finance loss and risk of the soul gas pipeline are higher than the purified natural gas pipeline.(5)Risk is calculated by using the Gaussian diffusion model at the H2S concentration threshold of 15ppm and 100ppm. It was found that the consequence area and the finance loss changes with the safety threshold. The poisoning area is greater than the thermal affecting area at the H2S concentration threshold of 15ppm, which making the proportion of poisoning finance losses increase in the total losses of the consequences. For this reason, the pipeline risk increases with the increase of the content of H2S. However, when using the H2S concentration threshold of 100ppm, the thermal injury area is the main consequence area. So with the increase of the H2S or reduces of the hydrocarbon components, the thermal injury area and the pipeline risk reduces.(6)Pipeline risk assessment are implemented for Calss 1 region with a pupolation of 10 families, Calss 2 region with a pupolation of 20 families and Calss 2 region with a pupolation of 100 families and find that the the pipeline risk increases with increasing population density. The higher the H2S content, the greater the increased rate of the risk. In the content range of 5% to 20%, the increase of population density does not increase the risk level of the pipeline and all are in grade "low".更多还原