GB1329072A - Drilling of underground boreholes - Google Patents

Abstract

1329072 Boring earth and rock CHEVRON RESEARCH CO 21 April 1971 [17 July 1970] 10607/71 Heading E1F [Also in Divisions C1 and G1] An indication of excessive wear in a drill bit 13 is provided when krypton 85, stored in non-gaseous form at one or more locations in the bit, is released into the mud stream and detected by means at the surface which separate the gas from the mud before taking a radiation count. The gas is stored in a form such as a hydroquinone clathrate or a kryptonated water soluble solid in cavities such as 86, 88 in a roller cone 89, Fig. 2 or in cavities in a shirt tail of a drill bit. When exposed by wear &c. the host solid dissolves in the mud and releases the krypton in gaseous form. The clathrate or kryptonated solid may be dispersed in or stored as pellets 75, 74 in a grease reservoir 70 of the bit which is pressurised by drilling mud via a diaphragm 76, and passes out of the bit with the grease when the bearings become worn. The released krypton passes with the mud through a pipe 18, Fig. 1, to a trough 20. The krypton is separated by a stirrer 23 and passes to an evacuated chamber 21, while the mud flows to a tank 29 for recirculation. The krypton is drawn by a vacuum pump 31 through a conduit 30, to beta and gamma ray counting means 36 and is expelled to the atmosphere. The counting means may comprise a counting element 35 in the form of a geiger tube, scintillation counter, ionization chamber or proportional counting means. The output from the element 35 is shown as an instantaneous reading on a dial 7 and as a function of time on a chart 39. The dial 7 may be connected to a visual or audible alarm.