| 摘要 |
<p>1,258,890. Boring earth &c. R. F. VARLEY CO. Inc. 14 Dec., 1970 [15 Dec., 1969], No. 59348/70. Heading E1F. In a method of deflecting a borehole by a jet or jets of drilling fluid, the velocity of the fluid used for jetting is greater than the velocity used for drilling. A slip joint 26 is mounted in the drill string 22 above drill collars 27 carrying a deflection bit 30 having at least one deflection nozzle 32 of greater diameter than other nozzles 33. The nozzle or nozzles 32 is or are directed in the direction it is desired that the hole will take and drilling mud is pumped by a pump 46 to the string whilst its upper part is raised so that the joint is fully extended. Rapid lowering of the upper part causes a valve 28 to close so that mud in the string below the valve is subjected to the weight of the upper part and mud issues through the nozzles 32 at increased velocity. The raising and lowering of the upper part of the string is repeated, the increased jetting velocity eroding the earth and the bit cutting the hole. (For Figures see next page)</p> |
