초록

A downhole drilling method comprises producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus (18) and allowing the pressure pulses to act upon a pressure responsive device (16) to create an impulse force on a portion of the drill string.

대표청구항 ▼

1. A downhole drilling method comprising: producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus in a drill string having a drill bit; and allowing the pressure pulses to act upon a pressure responsive device to create an impulse force on a portion of the dr

1. A downhole drilling method comprising: producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus in a drill string having a drill bit; and allowing the pressure pulses to act upon a pressure responsive device to create an impulse force on a portion of the drill string, wherein the impulse force is utilized to provide a hammer drilling effect at the drill bit. 2. The method of claim 1, wherein the impulse force is utilised to vibrate a bottomhole assembly (BHA) to reduce friction between the BHA and a bore wall. 3. The method of claim 1 wherein the pulses have an amplitude of up to around 500 psi. 4. The method of claim 1 wherein the pulses have an amplitude of between 700 and 1000 psi. 5. Downhole drilling apparatus for mounting on a drill string having a drill bit, the apparatus comprising: measurement-while-drilling (MWD) apparatus; and a pressure responsive device operatively associated with the MWD apparatus and responsive to pressure pulses produced by the MWD apparatus to create an impulse force on a portion of the drill string, wherein the impulse force is utilized to provide a hammer drilling effect at the drill bit. 6. The apparatus of claim 5, wherein the pressure responsive device is in the form of a shock tool. 7. The apparatus of claim 6, wherein the shock tool forms part of the drill string and axially extends and retracts in response to changes in internal fluid pressure. 8. The apparatus of claim 7, wherein the shock tool is tubular and comprises of two telescoping parts, with a spring located therebetween. 9. The apparatus of claim 8, wherein one of said parts defines a piston, such that a rise in drilling fluid pressure within the tool tends to separate the parts and thus axially extend the tool. 10. The apparatus of claim 5, wherein the pressure responsive device is located above the MWD apparatus. 11. The apparatus of claim 5, wherein the pressure responsive device is located below the MWD apparatus.