GB575685A - Improvements in or relating to well drilling - Google Patents

Abstract

575,685. Well - drilling. ZUBLIN, J. A. Nov. 11, 1943, No. 18748. [Class 85] [Also in Group XXVIII] In drilling a well bore deviating from an existing well bore, and particularly for drilling deviating bores within oil sands so as to tap parts of such oil sands remote from the existing well bore, an elongated resilient drill guide is employed of a form corresponding to the desired form of the deviating bore, such guide being stressed so that it may be inserted into the existing bore and the stress causing a bit at one end of the guide to press against a side wall of said existing bore, the bit then being rotated relatively to the guide while the bit and guide are advanced. The resilient guide also permits taking of side wall samples from a well bore, while by simultaneously rotating the guide at a speed slower than that of the bit, enlarging of a bore may be effected. In Fig. 2, a normally curved guide comprises one or more lengths of tube 1, each length having a helical slot 2 with its pitch increasing from the ends to the centre and preferably at all points greater than the external diameter of the guide so as to retain uniform curvature when stressed, the guide when stressed being inserted in a bore 6, whereupon, on rotating the bit 3, a curved deviating bore is formed ; the guide may then be replaced by a normally straight guide which is stressed to allow its insertion into the curved deviating bore, and on rotating the bit, a straight extension of said bore, or a straight bore deviating therefrom, is produced. In Figs. 7 and 8, the resilient, helically-slotted guide 12 has within it an imperforate flexible hose 13 with a helical flange 15 extending into the slot in the guide; the bit 19 is rotatably supported on the end of the guide and is driven by an axial flow turbine 22, 23, actuated by drilling fluid supplied through the hose 13. In Fig. 10, resilient guide sections 24, 30 are connected by a coupling 29, and the rotary drill 25 is driven by an inner hose 28, sections of which are connected by couplings 31 ; ball bearings 34, 37 are provided, the balls being inserted through holes 35 afterwards plugged. In Fig. 12, the resilient guide tube 38 is provided with staggered transverse slots 39 spaced further apart towards the centre of the tube ; the hose 40 may be free, or connected to the tube 38 by couplings 41. In Fig. 14, a normally curved guide tube 110 is held straight by a rigid inner member 115 which, after insertion of the tube into a well, may be removed by lowering an overshot 118 into engagement with. a head 123; the rigid member 115 may be replaced by a resilient member curved oppositely to the tube 110 and held during lowering as by a pin and slot. A curved rigid member 115 may be used to initially flex a normally straight guide tube. The member 115 may be hollow for the passage of drilling fluid.