Numerical calculation of elastic constants for sedimentary strata in triclinic approximation based on vertical seismic profiling data
© G.T. Prodayvoda, P.M. Kuzmenko, A.S. Vyzhva, 2015
It is firstly defined the symmetry and complete component set of tensor matrix elastic constants and elastic compliances by inversion of radial
velocity indicatrices for quasi-longitudinal, "quick" and "slow" quasi-transverse waves that are obtained according to the VSP method in the
standard acoustic coordinate system. It was established that the elastic constants of clay strata have planar triclinic symmetry and carbonate
strata have axial rhombic symmetry. The value of the elastic anisotropy integral coefficient is nearly 22%. Longitudinal axis and acoustic normal
of sedimentary strata were firstly determined according to field seismic survey. The estimation errors of elastic symmetry approximation for
sedimentary strata by models with transversely isotropic and orthorhombic symmetry were calculated. It is proved that such approximation
significantly changes the nature of the seismic wave azimuthal anisotropy and causes high error, which can significantly reduce the 3D seismic
efficiency to the oil and gas exploration in the complex geological conditions.
Key words: azimuthal anisotropy, elastic constants, symmetry, seismic waves.