Pgs Geophysical As

Allan McKay

Tashi Tshering

Maiza Bekara

Johan Mattsson

Eivind Rödnes Vesterås

Eivind Rødnes Vesterås

Kathrin Flisnes Bergh

Zhijun Du

Md Anwar Hossain Bhuiyan

Inversion of enhanced-sensitivity controlled source electromagnetic data can include approximating a background response from measured controlled source electromagnetic (CSEM) response data. The approximation can include performing a first inversion of the CSEM response data using a largest singular value in a diagonal of a matrix associated with the CSEM response data to create a first resistivity model of a subsurface of a subterranean formation and iteratively performing subsequent inversions while increasing an amount of singular values in the diagonal to obtain modeled CSEM response data to create a second resistivity model of the subsurface of the subterranean formation. Inversion of enhanced-sensitivity controlled source electromagnetic data can further include storing results of the first inversion and the iterative subsequent inversions producing a resistivity map based on the first and the second resistivity models.

Electromagnetic response data inversion using singular value decomposition

Techniques are disclosed for generating a time series representation of passive electromagnetic (EM) fields via towed streamer measurements without dependence on water-bottom measurement equipment. Such techniques may include storing records of respective time series measurements of passive EM fields measured by individual receivers as the individual receivers pass over a first measurement point, where the respective time series measurements correspond to respective measurement intervals, and where the respective time series measurements are synchronized with respect to a reference clock. The records of the respective time series measurements may be combined to generate a time series representation of passive EM fields observed at the first measurement point over a combination of the respective measurement intervals. The time series representation of passive EM fields observed at the first measurement point may, in turn, be used to identify one or more characteristics of subsurface structure.

Obtaining long-period magnetotelluric marine survey data using a towed streamer system

Methods of geophysical prospecting are described herein. In the described methods, a data set of electromagnetic readings from a marine geophysical survey is obtained and loaded into a computer processing system. Using the computer processing system, a high-frequency subset of the data is selected based on a frequency threshold, and a seawater resistivity map is resolved from the subset for a seawater portion of the survey by inversion. The seawater resistivity map can subsequently be used to resolve a resistivity map of the seabed from the data set by inversion.

Determining sea water resistivity

Methods of forming a geologic map usable for identifying prospective resource accumulations beneath the earth-surface are disclosed herein. The methods include obtaining a seismic stratigraphic structure of a subsurface region of the earth, determining a plurality of potential resistivity boundaries from the seismic stratigraphic structure, obtaining an electromagnetic data set resulting from an electromagnetic data acquisition of the subsurface region, recovering a resistivity map of the subsurface region by performing an inversion process guided by the seismic information, and resolving a geologic map from the resistivity map.

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Oslo, Norway

Allan McKay