ARRANGEMENT FOR REMOTE TRANSMISSION OF DATA FROM BOREHOLE IN OPERATION OF DRILLING RIG HAVING DRILLING BIT AND DRILL STRING FILLED WITH FLUSHING FLUID

摘要

A choker valve assembly for a drill string is provided for transmitting information measured in an underground bore hole by sensing devices, to the surface by modulating the pressure of the flushing fluid. The valve assembly includes a housing that is non-rotatably connected within the flushing fluid flow passage by cross-pieces extending between the housing and a portion of the inner pipe wall. A drag body valve element is mounted by the housing and is axially displaceable with respect to a tapered restriction portion of the inner pipe. Drive means for displacing the valve element is located outside the housing and extends between the valve element and the pipe wall through the cross-pieces. A cap is provided on each end of the valve element. The cap facing the direction of flushing fluid flow extends beyond the perimeter of the housing and the cap facing away from the direction of flushing fluid flow is entirely within the perimeter of the housing to provide a hydrodynamically pressure-compensated choker valve assembly.