Patent ID: 6958703
Filing Date: 2005-10-25
Classification: E21B

Abstract:
1. A drill string fitted with information transmission means, the string comprising: a plurality of hollow rods made of conductive material, the inside faces of said rods being covered in insulating material; a drilling tool secured to the bottom rod of the drill string, said drill string being disposed in part in a borehole filled with an electrically conductive mud, said mud inside the drill string and the conductive mud outside the drill string together with the drill string itself forming an electrically conductive loop; a first electrical unit disposed close to the bottom end of the drill string having at least a first annular electrode secured to the insulating inside face of the drill string, said electrode being electrically in contact with the mud contained inside the drill string, in order at least to create an electrical current in said loop that is representative of information to be transmitted; a second electrical unit disposed in said borehole, close to the top end of the drill string, in order at least to receive the information contained in said electrical current, said second electrical unit having second and third annular electrodes fixed to the insulating inside wall of the drill string and in electrical contact with the mud contained in said drill string, said second and third electrodes being axially offset, and accompanied by means for picking up the potential difference created between said second and third electrodes; and means for applying a voltage to said electrode, which voltage is representative of the information to be transmitted.