Receivers and methods for electromagnetic measurements
A receiver for electromagnetic measurements includes a polyhedron structure having m faces, where m≧4 and m≠6: n electrodes each disposed on one face of the polyhedron structure, wherein 3≦n≦m; and at least one circuitry connected to the n electrodes for signal measurement. A method for electromagnetic measurements includes obtaining a plurality of electric current measurements using a plurality of electrodes each disposed on a surface of a polyhedron receiver, wherein the plurality of electric current measurements comprise at least three different measurements; and determining electric field components in a three dimensional space from the plurality of electric current measurements by using a number of matrices that correlate orientations of surfaces of the polyhedron receiver to a coordinate system in the three dimensional space.
1. A receiver for electromagnetic measurements, comprising:
a polyhedron structure having m faces, wherein m≧5 and m≠6;
n electrodes each disposed on a corresponding one face of the polyhedron structure, wherein 4≦n≦m wherein each of the n electrodes is to measure an electrical current affected by a geological structure; and
at least one circuitry connected to the n electrodes for signal measurement.
2. The receiver of claim 1 , wherein the polyhedron structure is a regular polyhedron having a same length on all sides.
3. The receiver of claim 1 , wherein the polyhedron structure is an irregular polyhedron with one side having a length different from a length of another side.
4. The receiver of claim 1 , further comprising at least one sensor selected from a magnetometer, a resistivity sensor, a thermometer, an impedance sensor, a gravitometer, an accelerometer, an acoustic sensor, and combinations thereof.
5. The receiver of claim 1 , wherein the at least one circuitry has an adjustable impedance.
6. The receiver of claim 1 , wherein an impedance of the receiver is substantially the same as an impedance of seawater displaced by the receiver.
7. The receiver of claim 1 , wherein m=5.
8. The receiver of claim 7 , wherein n=4.
9. The receiver of claim 8 , wherein the polyhedron structure is a regular tetrahedron having a same length on all sides.
10. A system comprising:
the receiver of claim 1 ; and
a mechanism to transform the measured electrical current from orientations of the m surfaces of each of the polyhedron receivers into a predefined coordinate system.
11. The system of claim 10 , wherein the transforming is performed by using matrices that correlate orientations of the m surfaces of each of the polyhedron receivers to the predefined coordinate system.
12. The system of claim 11 , wherein the predefined coordinate system is a Cartesian coordinate system.
13. A method, comprising:
deploying a plurality of polyhedron receivers from a surface vessel;
towing a source over an area where the polyhedron receivers are located;
generating a plurality of electromagnetic signals from the source;
retrieving the plurality of polyhedron receivers;
downloading electromagnetic sensor data from the plurality of polyhedron receivers, wherein each of the polyhedron receivers have m faces and m≧5 and m≠6, and wherein each of the plurality of polyhedron receivers includes n electrodes each disposed on a corresponding one face of the corresponding polyhedron receiver, wherein 4≦n≦m, and wherein each of the n electrodes is to measure an electrical current affected by a geological structure; and
transforming the electromagnetic sensor data from orientations of the m faces of each of the polyhedron receivers into a predefined coordinate system.
14. The method of claim 13 , wherein at least a portion of the electromagnetic sensor data comprises current density measurements.
15. The method of claim 13 , wherein the transforming is performed by using matrices that correlate orientations of the m surfaces of each of the polyhedron receivers to the predefined coordinate system.
16. The method of claim 15 , wherein the predefined coordinate system is a Cartesian coordinate system.