| 摘要 |
<p>A pressure pulse generator for use in MWD operations in a drilling installation (10) having a drillstring (11), a drilling bit (19), means (13, 14) for supplying drilling fluid via the interior of the drillstring (11) and to the drilling bit (19), and an annulus (16) between the drillstring (11) and the wall (12) of the borehole which is being formed, said pressure generator being operative to generate a pressure pulse signal in the drilling fluid, and to transmit such signal to pressure monitoring equipment (20, 21) at the surface, and in which the pressure pulse generator comprises: an outer housing (30) which can be mounted in a drillstring component, and in which the operating components of the pulse generator are housed; a main valve (256, 257) having a valve operating chamber which, when the valve is opened, allows drilling fluid to pass from the interior of the drillstring to the exterior, and thereby to generate a pressure pulse signal that will travel to surface; a first pilot valve (116, 120) which is normally open, to allow fluid in the operating chamber of the main valve to communicate with the drilling fluid in the annular; and, a second pilot valve (88, 89, 90) which is normally closed, to control flow of drilling fluid between the inside of the drillstring and the operating chamber of the main valve.</p> |
