GB1195862A - Well Drilling Methods and Apparatus Employing Pressure Variations in a Drilling Fluid. - Google Patents

Abstract

1,195,862. Boring earth &c. HUGHES TOOL CO. 30 May, 1967, No. 24932/67 Heading E1F. In a method of rotary drilling the pressure of the drilling fluid surrounding the bit is subjected to cyclic fluctuations. The apparatus shown in Fig. 6 is located immediately above the bit and when in use the vibration generator A is touching the coupling device B. Part of the fluid passing to the bit nozzles is diverted through a port 163, a nozzle 167 and alternately into channels 185, 187. Part of the fluid entering the channel 187 enters a channel 195 to be discharged through a control nozzle 173 to divert the flow from the nozzle 167 into the channel 185. Some of the flow through the channel 185 passes through a channel 193 to be discharged through a control nozzle 171 to divert the flow from the nozzle 167 into the channel 187. The flow through the nozzle 167 therefore alternately passes through channels 191, 189. The flow from the channel 191 passes through a tube 217 and an aperture 219 to the cavity surrounding the 'bit, and the flow from the channel 189 passes through a tube 223 into an annular cavity 209 and through an aperture 225 to the cavity surround the, bit. Helmholtz resonators immediately above the generator prevent vibration in the fluid in the annulus about the drill string and in the fluid in the bore of the string to prevent loss of power. A shock absorber is embodied in the drill string above the apparatus. In a modified coupling device the tube 217 is replaced by a helically coiled tube discharging into the annular cavity which has a great number of outlets to the cavity surrounding the bit. In the modified apparatus shown in Fig. 10 a series of tubes 383 is mounted in the bore 381 leading fluid to the bit, each tube having an inlet 397 and diverting part of the fluid to discharge through holes 363 into the upwardly flowing fluid stream in the borehole. The diverted fluid spins and longitudinally vibrates a valve 359 to cause elastic vibrations in the spaces 357, 353 and the vibrations in the space 353 vibrate a member 367 which causes the cyclic fluctuations in the fluid surrounding the bit. In a further modified apparatus (Fig. 14 not shown) the bore leading fluid to the bit has a nozzle connected to feed-back channels, the arrangement being that cyclic pressure variations are given to fluid in an annular chamber surrounding the bore and these variations vibrate a ring (similar to the member 367 but mounted on the external wall of the chamber) which in turn causes the cyclic pressure variations in the fluid surrounding the bit.