Valve for drilling fluid telemetry systems

A downhole valve apparatus for use in a drilling fluid telemetry system during a borehole drilling operation wherein high pressure drilling fluid which is circulated down the central bore in the tubular drill string, through ports in the drilling bit and back up the annular space between the drilling string and the borehole wall is periodically vented from the central bore in the drill string to the annular space to generate a pressure pulse in the drilling fluid for detection at the surface, comprising;

• a tubular member connectable as part of the drill string;
• an elongate housing mounted within the central opening of said tubular member;
• a valve chamber formed within said housing;
• an inlet opening for high pressure drilling fluid connecting the outside of said housing and said valve chamber;
• an outlet opening for drilling fluid formed through the wall of said housing between the outside of said tubular member and said valve chamber;
• a valve seat rigidly mounted within and extending across said outlet opening, said seat having a flow opening therein with a front seating face surrounding the flow opening and being positioned within said valve chamber;
• a shear valve gate having a pair of planar faces and a flow opening extending therebetween mounted for reciprocating movement within said valve chamber, one of said planar faces being positioned in sliding engagement with the sealing face of the valve seat and the other of said faces extending across the inlet opening;
• means accessible from the exterior of said tubular member for rigidly clamping said valve seat within said outlet opening when in position and for providing an access opening for removing said valve gate from said valve apparatus when removed from position;
• and
• means for reciprocating said gate between a valve closed position where the gate face blocks the flow of fluid through the seat opening and a valve open position where the gate flow opening is in alignment with the seat opening to vent high pressure drilling fluid from the inside of the tubular member to the annular space and generate a negative pressure pulse in the fluid.

A downhole valve apparatus for use in a drilling fluid telemetry system during a borehole drilling operation wherein an erosive drilling fluid is circulated at high pressure and high flow rates down the central opening in a tubular drill string, through ports in the drilling bit and back up the annular space between the drill string and the borehole wall and wherein the erosive fluid is periodically vented from the central opening in the drill string to the annular space through the valve apparatus which comprises:

• a tubular member connectable as part of the drill string;
• passage means connecting the interior and the exterior of said tubular member;
• shear valve means positioned within said tubular member for selectively opening and closing said passage means, said shear valve means including:
• a valve seat rigidly mounted to said tubular member and having a sealing face surrounding a flow aperture through the seat;
• and
• a transversely movably mounted valve gate positioned against the sealing face of the valve seat and having a flow aperture therethrough, the size and shape of said gate flow aperture being arranged so that the gate surface substantially covers the sealing face of the valve seat and protects it from exposure to the erosive flow of drilling fluids when the gate and seat aperture are in alignment to permit flow through the valve;
• means accessible from the exterior of said tubular member for rigidly clamping said seat to said tubular member when in position and for providing an opening for removing said gate and seat from said valve means when removed;
• means for moving said valve gate between a closed valve position where the gate surface engages the sealing face of the valve seat to close the flow aperture and an open valve position where the flow apertures in the seat and gate are aligned to permit flow therethrough;
• and
• floating connection means between said valve gate and said means for moving said valve gate.