Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.

Abstract: A percussion drill 10 has a tubular fluid transmitting body 14, with a drill bit 16 mounted on a drill bit support 20 itself mounted in body 14 via a spring 22 and salines 24. A mass 28 is spring mounted in the body 14 and is movable to impact on a face 26 of the support 20. Mounted to the mass 28 is a rotating valve 32 comprising two valve plates 34, 36. Each plate 34, 36 defines a slot 38, 40, such that rotation of one of the valve plates 36 relative to the other moves the slots 38, 40 into and out of alignment; the change in alignment of the slots 38, 40 alters the flow of drilling fluid through the valve 32, so altering the drilling fluid pressure force acting on the mass 28, so causing mass 28 to push against the spring 30, and impact on the drill bit support 20 providing a percussive act ion at the drill bit 16.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.