Patent ID: 8538699
Filing Date: 2013-09-17
Classification: G01V

Abstract:
1. A computer implemented method for rapid inversion of electromagnetic data from a controlled source electromagnetic survey of a subterranean region, comprising: (a) summing measured electromagnetic survey data, using a computer, to form one or more composite gathers, each composite gather being formed from at least two selected ordinary gathers, said ordinary gathers being either common-receiver or common-source gathers; wherein loss of sensitivity to a subsurface resistivity anomaly due to data overlap or data cancellation, or both, in the one or more composite gathers is mitigated; wherein said loss of sensitivity is defined relative to sequential inversion, meaning inverting one ordinary gather at a time; wherein data overlap is mitigated by one or more of the following measures when forming the one or more composite gathers: (i) summing only a subset of the ordinary gathers in the survey, depending upon one or more of depth range of interest, earth conductivity, frequency of the data, and other parameters of the survey; (ii) preserving far-offset data by summing only selected components of the electromagnetic field from neighboring receivers; and wherein data cancellation is mitigated by phase encoding the ordinary gathers in forming the one or more composite gathers; and (b) inverting the composite gathers, using a computer, for resistivity or another subsurface electrical-property parameter.