Transmitter loops in series for electromagnetic geophysical surveys

A butterfly transmitter loop, adapted to be connected to a source of current and used for electromagnetic geophysical surveys,

• the butterfly transmitter loop being configured to form four subset loops in series, wherein the series configuration enables, when said current is provided, the current to be the same in the four subset loops, and
• wherein said subset loops are substantially in a same plane and are adjacently placed to be side-by-side to form a butterfly configuration, such that
• a transversal segment of the first subset loop is facing a transversal segment of the second subset loop, in a manner where both segments are substantially parallel to define a first loop region where said current, when provided, flows in both segments in the same direction, and
• a transversal segment of third subset loop is facing a transversal segment of the fourth subset loop, so that they are substantially parallel to define a second loop region where said current, when provided, flows in both segments in the same direction, and
• a longitudinal segment of the second subset loop is facing a longitudinal segment of the fourth subset loop, so that they are substantially parallel to define a third loop region where said current, when provided, flows in both segments in the same direction, and
• a longitudinal segment of the first subset loop is facing a longitudinal segment of the third subset loop, so that they are substantially parallel to define a fourth loop region where said current, when provided, flows in both segments in the same direction.

A method of electromagnetic geophysical survey using a transmitter loop, the method comprising:

• configuring, in a vicinity of a region to be surveyed, said transmitter loop in order to form at least two subset loops in series, wherein said subset loops are substantially in the same plane and are adjacently placed to be side-by-side, such that at least one segment of each subset loop is facing at least one segment of another subset loop and is substantially parallel to said at least one segment of another subset loop such that said facing segments are defining at least one loop region where a current can flow in facing segments in the same direction, and wherein the series configuration enables said current to be the same in all subset loops,
• providing a primary magnetic field in said region to be surveyed by having a current circulating in said transmitter loop, wherein said primary magnetic flux comprises a portion, in the vicinity of said loop regions, which is substantially parallel to said plane;
• and
• measuring along survey lines a secondary magnetic field, wherein said second magnetic field is generated by said region in response to changes in the primary magnetic field.