Abstract: An electromagnetic probe 1 measures the electromagnetic properties of a sub surface formation GF in a limited zone surrounding a well-bore hole WBH. The well-bore hole is filled with a well-bore fluid DM. The probe comprises a pad 2 having a first face defining a first area arranged to be positioned in contact with a well-bore wall WBW. The probe 1 further comprises: at least two transmitting antennas 4A, 4B defining a central point CP between them, each antenna being spaced from a distance do from the central point, and at least a first 5A, 5B and a second set 5C, 5D of receiving antennas, each set comprising a first receiving antenna 5A; 5C and a second receiving antenna 5B; 5D, the first receiving antenna being positioned on one side of the transmitting antennas and the second receiving antenna being positioned on other side of the transmitting antennas so that each set encompass the transmitting antennas 4A, 4B.

Abstract: A probe 1 for measuring the electromagnetic properties of a down-hole material MC, GF, DM of a well-bore WB comprises a metallic pad 2 in contact with the down-hole material. The pad 2 further comprises an open-ended coaxial wire 4 coupled to an electronic circuit 3. The open-ended coaxial wire 4 comprises an inner conductor 4A sunk in an insulator 4B and is positioned sensibly perpendicularly to the well-bore wall. The electronic circuit 3 is able to send a high-frequency input signal into the open-ended coaxial wire 4 and to determine a reflection coefficient based on a high-frequency output signal reflected by the open-ended coaxial wire 4.

Abstract: A probe 1 for measuring the electromagnetic properties of a down-hole material MC, GF, DM of a well-bore WB comprises a metallic pad 2 in contact with the down-hole material. The pad 2 further comprises an open-ended coaxial wire 4 coupled to an electronic circuit 3. The open-ended coaxial wire 4 comprises an inner conductor 4A sunk in an insulator 4B and is positioned sensibly perpendicularly to the well-bore wall. The electronic circuit 3 is able to send a high-frequency input signal into the open-ended coaxial wire 4 and to determine a reflection coefficient based on a high-frequency output signal reflected by the open-ended coaxial wire 4.