Patent GB-1189644-A (GB)
Title: Improvements relating to Earth Drilling.
Inventor: HOBHOUSE HENRY
IPC: E21B19/08
Filed: 1966-02-28
Abstract: 1,189,644. Automatic control of drilling. H. HOBHOUSE. April 26, 1967 [Feb.28, 1966; April 27, 1966; Aug.18, 1966; Aug.31, 1966], Nos.8725/66, 18513/66, 37119/66 and 38920/66. Heading G3R. [Also in Division E1] An electro-hydraulic system maintaining torque on a drill string constant has a reversible hydraulic motor connected to the string for varying the weight-on-bit, means for generating an electrical signal indicative of change in torque, and means responsive to the signal to vary the weight-on-bit and correct the torque. The reversible, hydraulic motor is a piston and cylinder which may support the crown block or be immediately below the travelling block. Hydraulic fluid is supplied by a hose 7 to the bottom of the cylinder 4 to raise the piston 19 and the string with the bit, a solenoid valve 21 being operated by a pressure switch 22 to prevent outflow of fluid from the cylinder in the advent of the hose failing. The pump and motor supplying the cylinder are immersed in hydraulic fluid pressurized by nitrogen in a tank having a cooling coil, the front of the tank forming the control panel for the rig, and the hydraulic and electrical circuits being duplicated, A transducer on a shaft driving the rotary table Fig. 5 (not shown) generates a signal proportional to the torque on the drill string at the table, and when a switch 42 Fig.7 is on position 42(1) this signal and a signal proportional to the required torque are subtracted in an amplifier 75 and the difference fed to a moving coil relay 78 which if the difference is excessive energizes one or other of the relays 80, 81 which act on a two way solenoid valve to supply, or remove, fluid from the cylinder to adjust the weight-on-bit. A pressure transducer 63 in the cylinder generates a signal proportional to the weight-on-bit and this signal and a signal proportional to the required weight-on-bit are subtracted in an amplifier 82 when the switch is in a position 42(2) to supply or remove fluid from the cylinder. When the switch is in a position 42(3) the gains of the amplifiers are set so that the solenoid valve is only actuated when the torque and the weight-on-bit exceed given limits. A transducer comprising a resistance rod 18 Fig.4 in the cylinder co-operating with brushes 20 on the piston gives a signal dependent on piston position and this signal is compared with a reference signal in the amplifier 82 when the switch is in the position 42(4) to adjust if necessary the position of the piston in the cylinder. When the switch is in a position 42(5) a positive signal in the line 86 fully extends the piston rod from the cylinder and the drill string may then be pulled by depressing a switch. In the down-the-hole turbine arrangement shown in Fig. 8 the pressure of the mud, air or other driving fluid (which is dependent on turbine torque) causes strain gauges 107 to generate signals which are used to supply or remove fluid from the cylinder 99. Signals from a flow sensor 100 connected to a gate 102 may, be combined with the signals from the strain gauges. The penetration rate may be obtained by means of the transducer 20, 18 and be recorded together with the mud pressure and weight-on-bit. The supply of mud may be controlled by the apparatus. The piston and cylinder may be replaced by a hydraulic winch supporting the string.