Westerngeco L.l.p.

Schlumberger Technology Corporation

Geco Technology B.v.

Nestor Cuevas

Edward Nichols

David Lee Alumbaugh

H Frank Morrison

Ping Zhang

Leendert Combee

Jiuping Chen

Michael Wilt

Martin N Howlid

James P Brady

Andrea Zerilli

An electromagnetic (EM) data acquisition method for a geological formation may include operating EM measurement devices to determine phase and amplitude data from the geological formation. The EM measurement devices may include at least one first EM measurement device within a borehole in the geological formation, and at least one second EM measurement device at a surface of the geological formation. The method may further include processing the phase data independent from the amplitude data to generate a geological constituent map of the geological formation, and identifying different geological constituents in the geological constituent map based upon the measured amplitude data.

Phase-based electromagnetic surveys for geological formations

A method analyzes a subterranean formation. At least one property of a well casing in the subterranean formation is determined and a plurality of current source vectors at respective positions along a trajectory of the well casing are determined. The effect of the well casing is determined based upon the plurality of current source vectors and the at least one property of the well casing.

Analyzing subterranean formation with current source vectors

Methods and related systems are described for measuring naturally occurring electromagnetic fields both at the earth's surface as well as downhole. These fields originate from currents in the ionosphere above the earth, and are the same fields as employed by known magnetotelluric geophysical methods based on surface measurements. Some embodiments are especially useful in horizontal wells that are uncased at depth, although some embodiments are also useful in normal vertical wells that are both uncased or cased with a conductive liner. The method includes receiving downhole electromagnetic survey data of the naturally occurring electromagnetic fields obtained using a downhole receiver deployed at a first location in a borehole. A second set of electromagnetic survey data of the naturally occurring electromagnetic fields is also received that has been obtained using a receiver deployed at a second location. A transfer function is estimated between the first and second locations for portions of the electromagnetic fields based on the two sets of electromagnetic survey data.

Electromagnetic survey using naturally occurring electromagnetic fields as a source

To perform a marine survey of a subterranean structure, a vertically oriented electromagnetic (EM) source is positioned in a body of water, where the EM source is coincident with an EM receiver. The EM source is activated to cause transmission of EM energy into the subterranean structure. After deactivation of the EM source, an EM field affected by the subterranean structure is measured by the EM receiver. In an alternative implementation, a survey system is provided that has a continuous wave EM source, a main EM receiver, and an auxiliary EM receiver.

Surveying a subterranean structure using a vertically oriented electromagnetic source

A survey module includes at least one sensing element to measure a first electromagnetic (EM) field along a first direction, and circuitry to derive a second EM field along a second, different direction based on the first EM field.

Deriving an electromagnetic field in one direction based on measurement data of one or more sensing elements for measuring an electromagnetic field in another direction

A system to perform a marine subterranean survey includes at least one vertical electromagnetic (EM) source and at least one EM receiver to measure a response of a subterranean structure that is responsive to EM signals produced by the vertical EM source. At least one tow cable is used to tow the EM source and EM receiver through a body of water.

Surveying using vertical electromagnetic sources that are towed along with survey receivers

A method of determining an orientation of a data acquisition system deployed on a seafloor includes measuring horizontal magnetic fields using detectors on the data acquisition system while the data acquisition rotates and descends to the seafloor or rises from the seafloor. Resting horizontal magnetic fields are measured after the data acquisition system is on the seafloor. A heading of the data acquisition system on the seafloor may be determined based on maximum and minimum horizontal magnetic fields measured during the descent and the resting horizontal magnetic fields.

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Albany, CA, United States of America

Nestor Cuevas