Method for electromagnetic survey design

摘要

A method for designing a controlled-source electromagnetic survey that willdiscriminate between a defined deep marginal-interest reservoir (2) and specifiedfalse positive resistivity structures of concern (3, 4, 5). A reservoir modeland a false positive model are constructed for each false positive scenario.The resistivity of the false positive model may be tuned to give electromagneticdata similar enough to the reservoir model when forward modeled that any differencesfall in the model null space. A null-space discriminating ratio ("NSDR")is defined, for example as the peak normalized difference of the two related modeledelectromagnetic field data sets. An area coverage display of NSDR values (6)allows determination of such additional data as may be needed to distinguishthe false positive body, and a survey design is developed accordingly (7). Reductionof the number of variables affecting the area coverage displays is a key featureof the method.