Camco Drilling Group Limited

Camco Drilling Group Limited of Hycalog

Camco Drilling Group Ltd. of Hycalog

Richard Edward Thorp

John D Barr

Douglas Bruce Caraway

Graham R Watson

Robert A Russell

A choke device for controlling fluid flow, particularly in a modulated bias unit, drill bit or other item downhole drilling component, comprises a passage for the flow of fluid, a choke aperture separating an upstream portion of the passage from a downstream portion thereof, and an impingement surface located in the downstream portion of the passage opposite and spaced from the choke aperture, so that fluid flowing through the choke aperture impinges on the impingement surface. The impingement surface is formed from superhard material, such as polycrystalline diamond, and may comprise the front facing table of a two-layer polycrystalline diamond compact of the kind used as cutting elements in drag-type drill bits.

Choke device

A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit. Each actuator comprises a movable thrust member which is hydraulically displaceable outwardly and a pivotally mounted formation-engaging pad which overlies the thrust member. An inlet passage supplies fluid under pressure to the chamber, and an outlet passage delivers fluid from the chamber to a lower pressure zone. A selector control valve modulates the fluid pressure supplied to each actuator in synchronism with rotation of the drill bit so that, as the drill bit rotates, each pad is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling. The outlet passage from the chamber passes through the thrust member so as to wash the region where the formation-engaging pad overlies the thrust member as the fluid flows to the annulus between the unit and the borehole.

Modulated bias unit for rotary drilling

A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled. A selector control valve modulates the fluid pressure supplied to each actuator in synchronism with rotation of the drill bit so that, as the drill bit rotates, each movable thrust member is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling. The control valve is a disc valve comprising two relatively rotating elements having contiguous surfaces formed of polycrystalline diamond. The elements are maintained in coaxial relation by a polycrystalline diamond bearing pin which extends axially from one element and engages in a central axial bearing aperture in the other element.

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Frampton-Cotterell, United Kingdom

Richard Edward Thorp