Method for spatially interpreting electromagnetic data using multiple frequencies
AssigneeExxonMobil Upstream Research Company
InventorsOlivier Burtz, James Carazzone, Dmitriy Pavlov
Life of this patent
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Abstract
Method for removing effects of shallow resistivity structures in electromagnetic survey data to produce a low frequency resistivity anomaly map, or alternatively imaging resistivity structures at their correct depth levels. The method involves solving Maxwell's electromagnetic field equations by either forward modeling or inversion, and requires at least two survey data sets, one taken at the source frequency selected to penetrate to a target depth, the other a higher frequency able to penetrate only shallow depths.
Claims13
A data-processing method for reducing masking effects of shallow resistivity structures on an electromagnetic survey of a subsurface region, comprising:
- (a) selecting a first survey data set generated at a first source frequency, said first source frequency having been selected to penetrate only said shallow resistivity structures;
- (b) selecting a second survey data set corresponding to a second source frequency lower than said first source frequency, thereby revealing deeper lying resistivity structures of the subsurface region as well as said shallow resistivity structures;
- (c) calculating the shallow resistivity structure by solving electromagnetic field equations using the survey data set generated at the first source frequency;
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- (d) using the calculated shallow resistivity structure and the electromagnetic data from the second survey to distinguish shallow response from deeper response.
Dependencies are inferred from the claim text.