Patent Document ID: 20090096457
Application ID: 11920676
Patent Flag: 0

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 at a plurality of online and offline receiver locations from the survey's results, said data comprising a field component sensitive at least predominantly to vertical resistivity and a field component sensitive at least predominantly to horizontal resistivity, wherein “online” and “offline” are defined with respect to a survey line (“source line”) of electromagnetic source positions; (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 measured electromagnetic field data; and (c) obtaining a measure of vertical electrical anisotropy at location (x,y,z) from the calculated horizontal and vertical resistivities.