Electromagnetic surveying for resistive or conductive bodies

A computer program product comprising a machine readable medium bearing machine-executable instructions for implementing a method of analyzing results from an electromagnetic survey of an area that is thought or known to contain a subterranean resistive or conductive body, comprising:

• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• and
• combining the horizontal gradients along the first and second directions to generate combined response data.

A computer apparatus loaded with machine executable instructions for implementing the method of analyzing results from an electromagnetic survey of an area that is thought or known to contain a subterranean resistive or conductive body, comprising:

• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• and
• combining the horizontal gradients along the first and second directions to generate combined response data.

A method for obtaining hydrocarbon from an area that contains a subterranean hydrocarbon reservoir, comprising:

• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter during an electromagnetic survey of the area;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• combining the horizontal gradients along the first and second directions to generate combined response data;
• identifying the subterranean hydrocarbon reservoir using the combined response data;
• penetrating the subterranean hydrocarbon reservoir with a hydrocarbon-producing well;
• and
• extracting hydrocarbon from the subterranean hydrocarbon reservoir using the hydrocarbon-producing well.

A volume of hydrocarbon obtained from an area that contains a subterranean hydrocarbon reservoir, the hydrocarbon obtained by:

• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter during an electromagnetic survey of the area;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• combining the horizontal gradients along the first and second directions to generate combined response data;
• identifying the subterranean hydrocarbon reservoir using the combined response data;
• penetrating the subterranean hydrocarbon reservoir with a hydrocarbon-producing well;
• and
• extracting hydrocarbon from the subterranean hydrocarbon reservoir using the hydrocarbon-producing well.

A results data set representing an area that is thought or is known to contain a subterranean hydrocarbon reservoir, the results data set obtained by:

• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter during an electromagnetic survey of the area;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• combining the horizontal gradients along the first and second directions to generate combined response data;
• and
• generating the results data set based on the data obtained.

A method for obtaining hydrocarbon from an area that contains a subterranean hydrocarbon reservoir, comprising:

• extracting hydrocarbon from the subterranean hydrocarbon reservoir, the subterranean hydrocarbon reservoir having been determined to contain hydrocarbon by means of an electromagnetic survey method comprising the steps of:
• providing horizontal electric or magnetic field data obtained by at least one receiver from at least one horizontal electric dipole transmitter during an electromagnetic survey of the area;
• determining a horizontal gradient in a first component of the electric or magnetic field data along a first direction;
• determining a horizontal gradient in a second component of the electric or magnetic field data along a second direction;
• combining the horizontal gradients along the first and second directions to generate combined response data;
• and
• identifying the subterranean hydrocarbon reservoir using the combined response data.