(1. State Key laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. Daqing Oilfield Engineering Co.，Ltd.，Daqing，Heilongjiang 163712，China)
Abstract：The initial seepage field analysis is prerequisite and important content for the water-tight underground oil cavern design. Although the field water pressure test can provide a more accurate isotropic permeability coefficient，which does not reflect the anisotropy permeability of jointed rock mass. In initial seepage field analysis of Dalian underground oil storage cavern，based on joins network simulation technique，a new method for calculating the anisotropy permeability is proposed. Firstly，different sizes of three-dimensional random joint networks are generated with the programming language Fish embedded within 3DEC. The values of joint geometric characters and number of random joints in each group are decided through the derivable formulas. Different sizes of rock permeability tensor are calculated based on fractured rock permeability tensor theory；meantime，with the size of three-dimensional random joint networks increasing，representative elementary volume is also determined until rock permeability tensor is not changed obviously. As the difficulty of fracture width measurement，some fracture fillings and the presence of non-connected，as well as the impact of fracture roughness，the calculated permeability tensor have a certain degree of error in value. It is necessary to amend according to field water pressure test. Principal value and characteristic vector of permeability tensor are easily calculated with Matlab software. Finally，considering the space orthotropic permeability coefficient，the initial seepage inversion is completed with the fl_anisotropic model within FLAC3D，the Fl_anisotropic model parameters are obtained from principal value and characteristic vector of permeability tensor. The inversion analysis provides initial seepage field for water-tight underground oil cavern water curtain design and stability analysis.
