Research On Carbon Storage Monitoring Technology Based On Cross-hole Electrical Resistivity CT

Carbon capture and storage is an effective measure to realize the important strategy of peak carbon dioxide emissions and carbon neutrality in China.However,stored CO₂ has the risk of leakage,and the leakage of high concentrations of CO₂ will cause many hazards.Therefore it is necessary to monitor stored CO₂.Cross-hole resistivity tomography（CHERT）is an excellent detection method with the advantages of low cost,deep detection,and high accuracy.So this study investigated the CHERT detection method and the feasibility and effectiveness of its application in carbon storage monitoring.The main research objectives were as follows:（1）Based on research on the forward and inverse problems of 2D CHERT,the CHERT algorithm was compiled.A set of optimized grids suitable for CHERT is proposed:inverse grid coarse division,and the forward grid subdivides the adjacent cells of the electrode on the basis of the inverse grid.The meshing method not only ensures the accuracy of forward calculation,but also reduces the cost of forward and inversion calculation.Through simulations and experiments,good performance of the 2D CHERT algorithm based on the optimized grids was proved.（2）Based on the research of the 2D CHERT algorithm,3D CHERT was further studied.Firstly,the 3D CHERT algorithm was compiled based on the research of the 3D CHERT forward and inverse problems.Then,an optimized mode of data acquisition-the mode of electrodes moving of equal-depth was proposed to solve the problem that the 3D CHERT detection method takes too long,which reduces the time required by 3D CHERT detection.And the reverse mode of electrodes moving was further increased by analyzing its cumulative sensitivity distribution so that its detection ability had also been improved.Through simulation and experiment,the good performance of the optimized mode of data acquisition was verified.At the same time,the existence and distribution of inevitable artifacts in the inversion images of three kinds of four-electrode observation configurations were qualitatively summarized.（3）Based on the research of 3D CHERT detection method,the dynamic monitoring method of 4D CHERT was further studied.To improve the imaging resolution of carbon storage monitoring by CHERT,the 4D inversion theory was studied,and the CHERT algorithm based on4D-ATC inversion was compiled.Then,based on the geological data of the Ketzin carbon storage test site in Germany,a quasi-dynamic geoelectric model reflecting the migration process of CO₂injected into the reservoir was constructed.Through simulation research,the monitoring effects of the independent inversion,conventional 4D inversion,and 4D-ATC inversion at each time were compared.The results show that the 4D-ATC inversion algorithm has the best effect of monitoring.Its inversion image can reliably explain the diffusion position of CO₂ in the reservoir,which proves that the CHERT dynamic monitoring method based on the 4D-ATC inversion algorithm performs well in carbon storage monitoring.There are 64 figures,5 tables and 72 references in this paper.