基于页岩气返排液中甲烷浓度及排放速率的红外光谱反演研究  

IR Spectral Inversion of Methane Concentration and Emission Rate in Shale Gas Backflow

作　　者：成潇潇 刘建国[1] 徐亮[1] 徐寒杨 金岭[1] 薛明 CHENG Xiao-xiao;LIU Jian-guo;XU Liang;XU Han-yang;JIN Ling;XUE Ming(Key Laboratory of Environmental Optics and Technology,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,China;University of Science and Technology of China,Heifei 230026,China;State Key Laboratory of Petroleum Pollution Control,CNPC Research Institute of Safety and Environmental Technology,Beijing 102206,China)

机构地区：[1]中国科学院合肥物质科学研究院安徽光学精密机械研究所环境光学与技术重点实验室,安徽合肥230031 [2]中国科学技术大学,安徽合肥230026 [3]中国石油集团安全环保技术研究院有限公司石油石化污染物控制与处理国家重点实验室,北京102206

出　　处：《光谱学与光谱分析》2021年第12期3717-3721,共5页Spectroscopy and Spectral Analysis

基　　金：中国科学院前沿科学重点研究项目(QYZDY-SSW-DQC016);国家自然科学基金专项项目(41941011);国家重点研发计划项目(2016YFC0201002,2016YFC0803001-08);安徽省重点研究和开发计划项目(1804d08020300);科技部国家油气重大专项项目(2016ZX05040-004)资助。

摘　　要：随着页岩气的开发,传统的手持式甲烷测量仪无法继续应对复杂的开采工况。针对页岩气开发过程中温室气体甲烷的浓度及排放速率难以实时在线监测的问题,利用自主设计并搭建的开放光程傅里叶变换红外光谱(FTIR)测量系统,对页岩气开采过程中各种工况下返排液进行实时在线测量。其中FTIR分辨率为1 cm^(-1),光程为50 m,红外光源通过返排液正上方被光谱仪接收。对测量所得的红外光谱进行多次平均,提高光谱质量并进行反演计算。从HITRAN数据库中提取甲烷特征吸收截面,考虑环境与仪器等影响,对测量温度进行修正,选取合适的吸收波段,与水汽的吸收截面进行吸收峰叠加,合成标准光谱。使用最小二乘法对实测光谱与标准光谱进行拟合,从而反演出甲烷浓度。并根据返排液排放速率,结合光路通过返排池的距离及红外光谱反演浓度,对页岩气开采过程中甲烷排放速率进行计算。结果表明:不同开采工况下,光谱反演浓度呈明显起伏变化。更换三项分离器时,甲烷浓度有明显上升;在点燃火炬时,甲烷浓度持续低值;其红外光谱反演浓度符合页岩气开采过程中甲烷排放情况。改变测量光谱平均次数,对返排液甲烷进行单位小时和连续80小时测量并分析。在单位小时内,甲烷浓度在100~800μmol·mol^(-1)范围内呈现明显起伏变化;甲烷的排放速率在50~300 m^(3)·h^(-1)内波动。对返排液进行80小时连续测量,甲烷浓度最大值为936.4μmol·mol^(-1),其最大排放速率达到535.1 m^(3)·h^(-1);最低值为36.82μmol·mol^(-1)最小排放速率为18.63 m^(3)·h^(-1)。反演数据结果说明:在页岩气开发过程中,其返排液为一个无组织甲烷排放源,且排放速率在短时间内变化十分明显。红外光谱反演浓度和传统手持式甲烷测量仪测量结果具有较好一致性,相关系数为0.7436。相对于传统手持式甲烷测量仪器,红外光谱�With the development of shale gas,the traditional handheld methane meter cannot cope with the complex shale gas production conditions due to the need for manual contact sampling.In view of the difficulty of real-time online monitoring of the emission concentration and rate of greenhouse gas methane in the process of shale gas development,we use the self-designed and built open Fourier transform infrared(FTIR)measurement system to measure the backflow liquid under various working conditions in the process of shale gas production.The FTIR resolution is 1 cm^(-1) and the optical path is 50 m.The light source passes directly above the backflow liquid and is received by the spectrometer.The measured infrared spectra are averaged several times,the hyperspectral mass is maintained,and the inverse calculation is carried out.The absorption cross-section calculated from the HITRAN database,considering the influence of environment and instruments,the measured temperature was modified,the appropriate methane absorption band was selected,and the absorption peak was superimposed with the absorption cross-section of water vapor to synthesize the standard spectrum.The methane concentration was calculated by fitting the measured spectrum with the standard spectrum using the least square method.The methane emission rate during shale gas exploitation was calculated according to the emission rate of the backflow fluid and combining the distance of the light path through the backflow pool and the infrared spectrum inversion concentration.The results show that spectral inversion concentration fluctuates obviously under different mining conditions.When the three separators were replaced,the methane concentration increased obviously.When the torch was lit,the methane concentration continued to be low,and the results of infrared spectrum inversion concentration were consistent with the methane emission in shale gas development and construction.The spectrum was averaged several times to improve the spectral quality,and methane in the back

关 键 词：页岩气 甲烷 红外反演 浓度 排放速率 

分 类 号：TE991[石油与天然气工程—石油机械设备]