GB776132A - Improvements relating to feed control in the drilling of wells - Google Patents

Abstract

776,132. Automatic borehole drilling. NATIONAL SUPPLY CO., and OIL WELL ENGINEERING CO., Ltd. Nov. 4, 1955 [Dec. 20, 1954], No. 31553/55. Class 85 [Also in Group XXIX] An automatic feed for a rotary drill string comprises a spooling drum 10 on which is wound a cable 11 feeding a travelling block 20 which supports the drill string, a brake 14 being forced into the drum 10 by a spring 23 and released by a piston 24 subject to fluid pressure which is controlled by the tension in the cable 11. In one embodiment, Fig. 1, fluid is drawn from a reservoir 47 through a conduit 48 to a pump 46 and then passes through a conduit 49, including valves 51, 50, to operate a motor 38, the discharged fluid passing through a conduit 103 and a conduit 28 to a stuffing box 29 and then out through ports 39 in arms 32, which are rotated by the drum shaft 43, of a follow-up valve 33, the fluid then passing through conduit 107 back to the reservoir 47. The motor 38 rotates a follow-up member 31 of the valve 33. The valve 50 is actuated automatically in dependence upon the tension in the cable 11 through a fluid capsule 22, a Bourdon tube operated valve 54 and a compressed air circuit 64,. 52 acting on a diaphragm 68 so that the valve 50 throttles the fluid flow through the conduit 49 on a decrease in the tension in the cable 11 when the valve 51, maintaining a constant pressure drop across the valve 50, will by-pass some of the fluid flowing through conduit 49 to a conduit 101 which communicates at one end with the conduit 28 and at the other, through a relief valve 102, with the reservoir 47. When the tension in the cable 11 increases the valve 50 tends to open giving an increased supply to the motor 38 increasing the speed of rotation of the member 31 which tends to close the ports 30 in the member 32. This causes an increase of pressure in the conduit 28, a branch of which communicates with a piston 24 which acts against the spring 23 and tends to release the brake 14 with a consequential increase in the speed of rotation of the drum 10. In one modification the rotary follow-up valve 33 is replaced by a needle valve operated by changes in the relative speed of rotation between the motor 38 and the drum shaft 43. A separate pump may be used to supply fluid to the valve 33 and the piston 24. The follow-up valve 33 may be replaced by a differential gear assembly. Specifications 600,294, 720,445 [Group XXIX] and U.S.A. Specification 2,650,796 are referred to.