Ohm, Inc.

Rock Solid Images, Inc.

Repsol ExploraciÓn, S.a

David Andreis

Lucy MacGregor

Michael E Tompkins

Nikolay Golubev

Marco Zanzi

Pedro Alvarez

Francisco Bolivar

Carlos Cobos

Dario Grana

Neville Barker

A computer implemented method is provided for generating a subsurface rock and/or fluid model on a determined domain. The subsurface rock and/or fluid model generated by the invention combines acoustic data and data obtained by an electromagnetic survey in such a way that the resulting model avoids the need of generating an image of the resistivity with the low resolution imposed by the known techniques inverting EM electromagnetic survey data.

Computer implemented method for generating a subsurface rock and/or fluid model of a determined domain

A method of analysing results from a controlled source electromagnetic survey of a region of interest containing a previously identified geological structure suitable for bearing hydrocarbons is described. The method comprises providing a first survey data set obtained outside the region of interest, i.e. off-target, for a range of source-receiver orientations and offsets, and providing a second survey data set obtained inside the region of interest, i.e. on target, for a range of source-receiver offsets. The method further comprises performing a mathematical inversion of the first survey data set to provide a model of the subterranean strata outside the region of interest, and processing the second survey data set to provide a model of the subterranean strata inside the region of interest, wherein the processing of the second survey data set takes account of the results of the inversion of the first survey data set.

Electromagnetic surveying

A method of analyzing electromagnetic survey data from an area of seafloor () that is thought or known to contain a conductive or resistive body, such as a subterranean hydrocarbon reservoir (), is described. The method includes providing electric field data and magnetic field data, for example magnetic flux density, obtained by at least one receiver () from a horizontal electric dipole (HED) transmitter () and determining a vertical gradient in the electric field data. The vertical gradient in the electric field data and the magnetic field data are then combined to generate combined response data. The combined response data is compared with background data specific to the area being surveyed to obtain difference data sensitive to the presence of a subterranean hydrocarbon reservoir. Because the combined response data are relatively insensitive to the transverse electric (TE) mode component of the transmitted signal, the method allows hydrocarbon reservoirs to be detected in shallow water where the TE mode component interacting with the air would otherwise dominate. Furthermore, because there is no mixing between the TE and transverse magnetic (TM) modes in the combined response data, data from all possible transmitter and receiver orientations may be used. The background data may be provided by magneto-telluric surveying, controlled source electromagnetic surveying or from direct geophysical measurement.

Electromagnetic surveying for resistive or conductive bodies

A method of analyzing electromagnetic survey data from an area of seafloorthat is thought or known to contain a resistive or conductive body, for example a subterranean hydrocarbon reservoir, is described. The method includes providing horizontal electromagnetic field data obtained by at least one receiverfrom at least one horizontal electric dipole transmitter. Horizontal gradients in the electromagnetic field data are determined for a first component of the electromagnetic field data along a first direction and for a second component of the electromagnetic field data along a second direction. The first and second components can be the electric field along the first and second directions, or the magnetic field perpendicular to the first direction and second directions. The gradients are then combined to provide combined response data. Because the combined response data are relatively insensitive to the transverse electric (TE) mode component of the transmitted signal, the method allows hydrocarbon reservoirs to be detected in shallow water where the TE mode component interacting with the air would otherwise dominate.

Method for monitoring an area containing a subterranean resistive or conductive body, and for obtaining a volume of hydrocarbon therefrom

A method of analysing results from an electromagnetic survey of an area that is thought or known to contain a subterranean resistive or conductive body within a background strata configuration is described. The method comprises providing a set of electromagnetic field data obtained using at least one electromagnetic receiver and at least one electromagnetic source for a range of source-receiver separations, e.g. providing conventional controlled-source electromagnetic survey data. A subset of the electromagnetic field data is identified that comprises data obtained for source-receiver separations greater than a selected threshold offset. The threshold offset is chosen so that data beyond this offset are characteristic of magnetotelluric data. Thus the subset of data is then processed in accordance with a first technique to obtain information on the background strata configuration. Other electromagnetic field data obtained for source-receiver separations less than the threshold offset may then be processed in accordance with a second technique to obtain information on any subterranean resistive or conductive body within the background strata configuration.

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Aberdeen, United Kingdom

David Andreis