Water injection test about water curtain borehole for underground water-sealed cavern and analysis of rock equivalent permeability parameter

Analysis of seepage field and prediction of the quantity of inflow towards hydrocarbon storage caverns are the core issues associated with evaluations of water-sealed effects of a water curtain. Nowadays, equivalent continuum models are predominately used in analyzing this kind of large-scale seepage field; and the reliability of analysis results depends on whether or not the equivalent permeability of rock masses can be reasonably and reliably obtained. A great number of in-situ hydraulic tests concerning water curtain boreholes are conducted during the construction stage. Based on these tests, the equivalent permeability of rock masses can be analyzed and determined. However, the issues of theoretical background of test, the rationality of experiment procedure and the analysis of experiment data need to be studied in depth. Firstly, the procedures and features of four kinds of in-situ hydraulic tests about water curtain boreholes are presented, which are conducted in the Huangdao water-sealed oil storage cavern project in China. Secondly, the impacts of drainage of water curtain galleries on the seepage fields during construction are investigated by using a three-dimensional seepage numerical analysis method. Based on the water injection tests of water curtain borehole during construction, an empirical relation between the equivalent permeability of rock mass surrounding the water curtain boreholes and water injection rate is established under the Darcy flow postulation. According to the relation, the permeability of rock mass can be inverse calculated, the influences of various fracture formations on both the injection rate and the rock permeability are also analyzed by using a fractured porous flow model. At last, the practical test data is analyzed and the partition map of the permeability of rock masses is accomplished. The research results are of reference values for both the theoretical analysis of hydraulic tests regarding water curtain boreholes and parameterization of permeability of rock masses.