Ohm, Inc.

Rock Solid Images, Inc.

Repsol Exploración, S.a

Lucy MacGregor

Martin C Sinha

David Andreis

Peter Harris

Michael E Tompkins

Pedro Alvarez

Neville Barker

Marco Zanzi

David Charles Newall Pratt

Dario Grana

Jonathan Harvey Nicholls

Carlos Cobos

Francisco Bolivar

Nikolay Golubev

Richard Weaver

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 analyzing controlled source electromagnetic (CSEM) survey data to determine probability density functions (PDFs) for values of an electromagnetic parameter at locations in a subterranean region of interest is provided. Structural features in the subterranean strata are identified, e.g. from seismic survey data. An initial PDF for values of the electromagnetic parameter is then assigned to each feature. Models specifying values for the parameter in each structural feature are generated by sampling the PDFs. A subset of the models are deemed acceptable based on an acceptance criterion. The PDF for each feature is modified based on values for the parameter in the subset of accepted models to generate replacement PDFs for each feature. The process may be iterated a number of times to generate final PDFs for values of the electromagnetic parameter in the structural features identified in the subterranean region of interest.

Geophysical surveying

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 for mapping a property of a subsurface reservoir includes determining a value of at least one reservoir property from measurements obtained from a well drilled through the reservoir. A relationship is determined between the at least one property of the reservoir and at least one seismic attribute and at least one electromagnetic survey attribute at a geodetic position of the well. A value of the at least one reservoir property is determined at at least one other geodetic position from a value of the at least one seismic attribute, a value of the at least one electromagnetic survey attribute at the at least one other geodetic position, and from the determined relationship.

Method for interpreting seismic data and controlled source electromagnetic data to estimate subsurface reservoir properties

A method of electromagnetic surveying of an area of seafloor that is thought or known to contain a subterranean hydrocarbon reservoir is described. The method includes broadcasting an EM signal from a horizontal electric dipole (HED) transmitter and obtaining vertical electric dipole (VED) response data at a remote receiver in response thereto. Survey data are analyzed by comparing the VED response data with background data which are not sensitive to the postulated hydrocarbon reservoir. Accordingly, differences between the VED response data and the background data allow for the identification of buried hydrocarbon reservoirs. The background data may be provided by magneto-telluric surveying, controlled source electromagnetic surveying or from direct geophysical measurement. By employing VED response data in this way, surveys may be performed in shallower water than has previously been possible since the VED detector is not sensitive to air-wave components of the EM field induced by the HED transmitter at the VED detector.

Electromagnetic surveying for hydrocarbon reservoirs

A detector for underwater electromagnetic surveying is described. The detector comprises first, second, third and fourth electrodes which are arranged to define first, second and third electric dipole antennae extending between pairs of the electrodes. Each dipole antennae extends between a pair of the electrodes and the fourth electrode is common to all three dipole antennae. Thus the first electrode is separated from the fourth electrode along a first direction to provide the first dipole antenna, the second electrode is separated from the fourth electrode along a second direction to provide the second dipole antenna, and the third electrode is separated from the fourth electrode along a third direction to provide the third dipole antenna. The electrodes are arranged so that the first, second and third directions are inclined at an angle of between 20 and 70 degrees to a surface on which the detector rests when in normal use.

Electromagnetic detector for marine surveying

A method of electromagnetic surveying of an area of seafloor that is thought or known to contain a subterranean hydrocarbon reservoir is described. The method includes broadcasting an EM signal from a horizontal electric dipole (HED) transmitter and obtaining vertical electric dipole (VED) response data at a remote receiver in response thereto. Survey data are analysed by comparing the VED response data with background data which are not sensitive to the postulated hydrocarbon reservoir. Accordingly, differences between the VED response data and the background data allow for the identification of buried hydrocarbon reservoirs. The background data may be provided by magneto-telluric surveying, controlled source electromagnetic surveying or from direct geophysical measurement. By employing VED response data in this way, surveys may be performed in shallower water than has previously been possible since the VED detector is not sensitive to air-wave components of the EM field induced by the HED transmitter at the VED detector.

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.

An electromagnetic survey method for surveying an area that potentially contains a subterranean hydrocarbon reservoir. The method comprises detecting a detector signal in response to a source electromagnetic signal, resolving the detector signal along at least two orthogonal directions, and comparing phase measurements of the detector signal resolved along these directions to look for a phase separation anomaly indicative of the presence of a buried hydrocarbon layer. The invention also relates to planning a survey using this method, and to analysis of survey data taken using this survey method. The first and second data sets may be obtained concurrently with a single horizontal electric dipole source antenna. The method is also largely independent of a source-detector pair's relative orientation and so provides for good spatial coverage and easy-to-perform surveying.

Growing community of inventors

Edinburgh, United Kingdom

Lucy MacGregor