碳封存项目井喷CO_2扩散危险水平分级方法研究

Classification of hazard levels of carbon dioxide dispersion under a well blowout in a CCS project

针对碳封存（CCS）项目井喷后的二氧化碳（CO_2）气体泄漏扩散对附近居民的影响问题,提出将CO_2井喷速率作为分级指标进行扩散危险水平分级。以内蒙古自治区鄂尔多斯市伊金霍洛旗地形、气候等条件为环境背景,以神华CCS示范项目为参考,运用CALPUFF高斯扩散模型模拟发生井喷事故,计算CO_2气体扩散影响范围。根据扩散范围与井喷速率变化的相关关系,对CO_2扩散危险水平进行分级。根据50 000 ppm浓度的最大扩散范围将CO_2井喷扩散分为3个等级：Level1、Level 2、Level 3,对应的井喷速率范围分别为0-2.5、2.5~10.0、10~20 m/s,对应扩散距离分别为0~130、130~180、180~420 m。通过与模拟场地周围环境条件和人群分布特点的交叉分析,当危险性等级为3级时,会威胁到泄漏井筒附近420 m范围内CCS场地内工作人员、散户居民以及附近公路上的过往行人的安全。该项危险水平分级研究工作有助于健全国家相关部门对CCS的监管,同时有利于推动CCS示范项目的健康发展。

A classification indicator is proposed and the hazard levels are classified for the carbon dioxide （CO_2） dispersion when a well blowout is encountered at a CO_2 capture and storage （CCS） site. Taken the topography and climate conditions of Yijinhuoluo Qi in Erdos city, Inner Mongolia, China, as the environmental background, the CALPUFF model is used to simulate a supposed well blowout with a reference import from the Shenhua CCS demonstration project. The dispersion distance of released gases is calculated, then the relationship between the dispersion distance and the blowout speed is chosen to classify the hazard levels of CO_2 dispersion, and finally its influence is conducted. According to the maximum dispersion distance of the CO_2 concentration in 50 000 ppm, the hazard levels of CO_2 dispersion are classified into three levels by using an indicator of blowout speed. A well blowout with a release rate of CO_2 between 0 and 2.5 m/s is identified as Level 1 corresponding to the dispersion distance of 0-130 m; a release rate of CO_2 between 2.5 and l0 m/s is as Level 2, and the dispersion distance is 130-180 m; a release rate of CO_2 between 10 and 20 m/s is as Level 3 with the dispersion distance of 180-420 m. According to the experimental research, it is shown that the persons around the leakage well within 420 m are affected when the hazard level reaches Level 3, which means the workers in the operational site, the residents around and the pedestrians passing on the nearby county road are all affected. Our research on the classification of hazard levels not only contributes to the supervision of relevant government agencies to the CCS projects but also is beneficial to the promotion of coming CCS demonstration projects in China.