Abstract: A method and a system for the transmission of information from a well (1; 20) drilled through geological formation layers (3) at least partly cased by metal tubes (4; 23; 24; 31). The method includes the placing in said well of an information transceiver (E) operating by electromagnetic waves created by the injection of an electric signal by a dipole (P1-P2) conductively connected to the metal tubes used for guiding the transmitted waves. In the method, identification takes place of the attenuation of the transmission by certain formation layers (3a, 3b; 25; 30) having a low resistivity and then there is an at least partial electrical insulation of the metal tubes located opposite the low resistivity layers.

Abstract: Seismic waves are recorded twice by a reference sensor (8) above ground and by a sensor (18) located in the drill hole (1). Measurements are synchronized by a clock system, the clock associated with sensor (18) being designed specifically for providing such synchronization in spite of operating conditions prevailing at the bottom of a drill hole (vibrations, shocks, temperature).

Abstract: The present invention relates to a device for connecting two metal parts. The device comprises a first element (1) having a female conical surface and a second element (5) having a male conical surface, at least one of the two surfaces being coated with a thin layer (12) of an electrically insulating material. The two elements (1, 5) are inserted one inside the other so that they are mechanically joined and electrically insulated.

Abstract: Seismic waves are recorded twice by a reference sensor (8) above ground and by a sensor (18) located in the drill hole (1). Measurements are synchronized by a clock system, the clock associated with sensor (18) being designed specifically for providing such synchronization in spite of operating conditions prevailing at the bottom of a drill hole (vibrations, shocks, temperature).

Abstract: A device and method for transmitting information between a well bottom and the surface by means of electromagnetic waves. The device includes transmitting information on either side of a valve (9) placed in a string of pipes (4) in a well by means of two electromagnetic wave transmitter-receiver unit (1, 2) placed on either side of the valve. In the device, unit (2) placed above valve (9) is lowered by means of logging type cable (3) into inner space of pipes (4).

Abstract: Information can be transmitted between equipment at the bottom of a drilling operation and the surface. A transceiver is provided at the surface, and is connected to both the earth, or the bottom of the ocean in an offshore operation, spaced from the drilling operation, and metal pipework used in the drilling operation. A transmitter/receiver is used for applying and receiving electric signals between two points on the metal pipework. The two points are separated at a substantial distance along the metal pipework such that the resistance of the metal pipework connecting the two points is relatively low but greater than zero. No insulating junction is then needed to be interposed between the two points in the metal pipework connecting the two points. Preferably, the transmitter/receiver has upper and lower conductors with first and second polar ends at the two points, thus forming a dipole of substantial length across the metal pipework.