Determining representative permeability coefficients of original and grouted rock mass for underground water-sealed oil storage: method and application

The permeability coefficient of rock mass is a critical parameter for groundwater flow analysis of underground water-sealed oil storages. Based on the site geological investigation, monitoring information, and data statistics, a method of determining representative permeability coefficients of original and grouted rock mass for underground water-sealed oil storage was proposed. Then, the proposed method was applied to the flow field analysis of an underground water-sealed oil storage under construction. The assessment of containment properties, the prediction of water inflow, and the analysis of grouting effect were carried out. For the similar kind of underground water-sealed oil storages, the geometric mean of the tested permeability coefficients was suggested to be the representative value of original rock mass. The relationship between the permeability reduction factors of grouting and the original permeability coefficients was obtained to predict the grouting zone permeability. Based on the proposed method, the representative original permeability coefficient of the storage zone is determined to be 1.96E-03 m/day, and the permeability coefficient of the grouted zone is conservatively suggested to be reduced to 10% of the original value. The predicted results of water inflow and grouting effect by flow simulation were compared with that by engineering analogy and theoretical analysis, which further verified the rationality of the proposed method and the reliability of the flow field analysis. The method of determining the representative permeability coefficients of rock mass and its application can help improve the accuracy of groundwater flow field analysis and offer guidelines for the construction of underground water-sealed oil storage.