Patent Document ID: 7894989
Application ID: 11920676
Patent Flag: 1

Claim One:
1. A computer-implemented method for determining earth vertical electrical anisotropy from an electromagnetic survey of a subsurface region located below the water bottom in an offshore environment, said survey using an electromagnetic source and a plurality of electromagnetic receivers, said method comprising: (a) obtaining electromagnetic field data from the survey's results at a plurality of online and offline receiver locations and corresponding to selected ones, but fewer than all, of the six electromagnetic field components E X , E Y , E Z , H X , H Y , and H Z , said selected components comprising a field component selected because it is sensitive at least predominantly to vertical resistivity and a field component selected because it is sensitive at least predominantly to horizontal resistivity, wherein the terms online and offline are defined with respect to a survey line, called a source line, of electromagnetic source positions, and wherein determination of predominantly sensitive depends upon source type and upon receiver location relative to the source line; (b) solving Maxwell's electromagnetic field equations for horizontal resistivity and vertical resistivity at an (x,y,z) position in the subsurface region, using survey acquisition parameters and the selected components of measured electromagnetic field data, said solving being performed on a computer by either inversion or forward modeling techniques; and (c) obtaining a measure of vertical electrical anisotropy at location (x,y,z) from the calculated horizontal and vertical resistivities.