3D Modeling and Inversion

WesternGeco pioneered 3D inversion of EM data in our Milan office, with activity in this field going back to 1991 and covering both inductive and galvanic source techniques.

In MT, a processed measurement consists of a 5-element complex tensor which relates electric and magnetic components over a broad frequency range. This tensor is usually decomposed to give two apparent resistivity and phase pairs. Until recently, the decomposed data were inverted using 1D and 2D techniques, which carry with them a host of underlying assumptions inappropriate to the majority of 3D exploration plays. These issues are resolved using 3D inversion, with the complete impedance tensor at all sites as the input data.

In CSEM and MT, WesternGeco has developed the only industry benchmarked and fully tested code for 3D inversion. More than 300 datasets have been inverted, including oil exploration, geothermal, and mining targets.