GB2172325A

GB2172325A - Controlling drilling direction

Info

Publication number: GB2172325A
Application number: GB08606519A
Authority: GB
Inventors: Gordon Douglas; Peter Allen
Original assignee: Cambridge Radiation Tech
Current assignee: Cambridge Radiation Tech
Priority date: 1985-03-16
Filing date: 1986-03-17
Publication date: 1986-09-17
Also published as: GB2172325B; GB8606519D0

Abstract

A rotatable drilling tube (10, 110) carries at its extremity a drilling bit (12, 112). The drilling course and direction is controlled by applying to the drilling tube a lateral deflecting force at a location intermediate two spaced support means, so that a curvature is imparted to the tube between the support means. In one embodiment (Figures 1 to 3) the support means are stabilisers (16, 18) which engage the bore hole wall (14), the latter then providing a reactive force countering the deflecting force. in another embodiment (Figures 4 to 10) the support means are bearings (158, 160) by which the drilling tube (110) is rotatably supported in a tubular casing (154) the reaction forces then being resisted internally in the casing (154). <IMAGE>

Description

SPECIFICATION Drilling apparatus Field of the invention This invention relates two drilling apparatus, and in particularto apparatus for deflecting a rotatable drilling tubeto control the drilling course of direction.

Summary ofthe invention According to the invention there is provided appar atus for deflecting a rotatable drilling tube to control the drilling course, comprising actiating means which do not rotate with the drilling tube and which are disposed between two support means, which support the drilling tube in a radial sense at two positions spaced along the length ofthe drilling tube, the actuating means applying to the drilling tube a deflecting force which has a magnitude and direction to impart a required curvature to the drilling tube between the two support means in orderto control the drilling course.

In one embodiment the support means are stabilis ers which engage the bore hole wall which provides a reaction force against the deflecting force applied by the actuating means.

In an alternative embodiment the support means are bearing which rotatably support the drilling tube within a casing disposed within the bore hole, the casing providing a reaction force against the deflecting force applied by the actuating means.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure lisa diagrammatic view of the bottom hole assembly of drilling apparatus forming an embodiment of the invention, Figure 2 is a detailed view, on an enlarged scale, of part of Figure 1, Figure 3 is a sectional view on the line Ill-Ill of Figure 2, Figure 4 is a diagrammatic view ofthe bottom hole assembly of a second embodiment of the invention, Figure 5 is a detailed view of part of Figure 3, FigureS is a sectional view on the lineVI-VI of Figure 5, Figure 7 is a detailed view ofanother partof Figure 3, and Figures 8,9 and 10 are respectively side, end and plan views of a flexible enclosure ofthe drilling apparatus.

Detailed description of the drawings Referrring to Figure 1, the drilling apparatus comprises a rotatable drilling tube 10 carrying at its extremity a drill bit 12. The drilling tube 10 is supported and centred in a bore hole 14 by two spaced stabilisers, namely a near bitstabiliser 16 and afarbit stabiliser 18. Between the stabilisers 16 and 18 is located a control stabiliser 20 which applies to the drilling tube 10 a controlled lateral force and displacement (indicated by arrow 22) in orderto deflectthe tube 10 between the spaced supports constituted by the stabilisers 16 and 18. Figure 1 illustrates the undeflected drilling tube at 24 and the deflected drilling tube at26, the change in drilling direction being indicated by the angle 28.

Figure 2 shows a half section through the control stabiliser20, on an enlarged scale. Referring to Figure 2, the control stabiliser 20 has a housing 31 which contains sensing means, information storage means and comparison means,togetherwith batteries, hydraulic pump, valves and other equipment necessary forthe operation of the actuating means. The batteries are for powering the electronic and other equipment associated with the control means. The hydraulic pump is driven from the rotating drilling tube by virtue of the relative rotation between the rotating drilling tube and the normally stationary housing.The sensing device senses the actual drilling direction and this is compared in the comparison means with the desired drilling direction stored in the information storage means, any difference being used to apply a deflecting force to the drilling tube 10 so that the drilling coursefollowsthedesireddrilling course.

The wall contact assembly 33, which is externally similarto a conventional stabiliser, provides the reaction to the radial force applied to the drilling tube by means of the actuator assembly 34. The wall contact assembly may rotate with the drilling tube, in which case the forward joint 35, which is connected to the wall contact assembly by a nose casing 36, is arranged to allow anguiation about axes normal to and passing through the axis of the drilling tube, while preventing rotation aboutthe axis of the drilling tube and minimising radial and axial movement. Bearings 37 connect the rotating wall contact assembly with the non-rotating assembly consisting of an angulation coupling 38, an actuator casing 39 and an anti-rotation device 40.The angulation coupling 38 is similar in performancetotheforward jointandallowsangula- tion about axes normal to and passing through the axis of the drilling tube but prevents relative rotation aboutthe axis ofthe drilling tube and prevents all relative translational movements. The anti-rotation device 40 is designed to apply radial force to the bore hole wall 14 and provide torsional resistance preventing rotation, which having minimal resistance to axial movement.

The housing 31 is connected rigidly to an actuator bridge member41. This assembly is located onto the drilling tube by means of spaced bearings 42. This assembly is also connected to the actuator casing by means of a rear joint43which which has the same properties astheforwardjointandsimilarpropertiestother angulation coupling.

The actuator assembly 34 consists of four individual actuators 44. These actuators 44 lie within the annular space 46 between the actuator casing 39 and the actuator bridge member 41 and each actuator is disposed at equal intervals around the periphery, as best shown in Figure 3. The movement ofthe drilling tube relative to the wall contact assembly is achieved by applying different pressures, in a controlled manner, to each of the four actuators 44.

The form of the actuators could be a flexible enclosure such as a hose ortube 44 or a variation thereof, with one end blanked off and the other end connected to a hydraulic supply and return pipe. The flexible material could be woven polyester or nylon coated with a suitable elastomer such as Viton.

Four ofthesetubes 44 are fitted into the annular space 46 reserved forthe actuators, as shown in Figure 3. In the neutral position the cross section of each tube 44 would be partiallyflattened. As hydraulic fluid is supplied to any one actuator it has the tendency to return to its circular cross section and hence a radial force is applied at the actuator location which is dependent on the hydraulic fluid pressure and the cross sectional geometryoftheactuator.

Provided the actuator diametrically opposite to the actuator being filled is allowed to vent, the actuator bridge member41 and hence the drilling tube 10 will be moved radially with respecttothe actuator housing. The use offour actuators allows the actuator bridge member 41 to be positioned at any location relative to the actuator housing only within the limits of maximum radial movement.

An alternative mode of operation is with the wall contact assembly not rotating with the drilling tube. In this case the forward joint 35 is located on the drilling tube by means of a bearing assembly 45 and the bearings 37 are locked to provide a rigid connection. It may be useful to configurethisform of invention so thatthe modes of operation can be interchanged by means of simple adjustment. With the wall contact assembly not rotating it may bethatthe anti-rotation device is not required, this function being provided by the wall contact assembly itself.

It will be appreciated that in the embodiment of Figures 1 to 3 the control stabiliser 20 applies to the rotating drilling tube 10 a deflecting force which has a magnitude and direction to impart a required curva tureto the drilling tube 10 between the stabilisers 16, 18, in orderto control the drilling course. The reaction againstthe deflecting force is provided by the bore hole wall at the locations ofthe stabilisers 16, 18, as indicated by arrows 21 in Figure 1.

lntheembodimentofFigures4to 10, parts equivalent to those of Figures 1 to 3 have been given the same reference numerals increated by 100. Hence, in Figure 4, the drilling tube 110 extends through a stabiliser 118 and an optional stabiliserll6.An intermediate stabiliser 150 is provided, and instead of the control stabiliser 20, the embodiment of Figures 4 tolOhasacontrol module 152.

The module 152 has a cylindrical casing 154 having end seals 156 and enclosing bearings 158, 160 and actuating means 162 for deflecting the drilling tube 110. Referring to Figures 5 and 6, the actuating means 162 comprisefourflexible enclosures in the form of bags 164 located in the annular space between the casing 154 and a bearing sleeve 166. The bearing sleeve 166 does not rotate with the drilling tube 110 but is mounted on the latter by bearings 161. Fluid is fed to the bags 164through hydraulic pipes 168 which communicate with a pump (170, Figure 7)through a valve block and reservoirs unit 172.

The pump 170 is located in the annularspace between the casing 154 and a bearing sleeve 174 which is non-rotatably mounted on the rotatable drilling tube 110 by a bearing 776. Between the drilling tube 110 and the inner race ofthe bearing 176 is located an eccentric sleeve 178' vv h .ch rotates with the drillingtube110andcausesthebearingsleeve174to oscillate in the radial direction of arrow in Figure 7, therebyto apply a pumping action to flexible enclosure or bag 178 of the pump. The flexible bag 178 is similar in construction to one of the flexible bags 164. An anti-rotation pin 180 interconnecting the casing 154 and the bearing sleeve 174 prevents rotation ofthesetwo components.

Figures 8,9 and 10 show the construction of a representative bag 164 or the bag 178. The bag 164 or 178 has a fabric bodyformed intoatubularconfigura- tion, opposite edges being sealed by metallic clamping strips 182, from one of which extends a hydraulic supply or return pipe forming the hydraulic pipe 168.

The magnitude and direction ofthe deflecting force applied bythe bags 1 64to the drilling tube are controlled by appropriate control of the application of hydraulic pressurefrom the pump bag 178 to the actuator bags 164. In orderto achieve the required deflecting force, two adjacent bags 164 are individually pressurised to the required extent, and the two remaining bags 164 are completely depressurised, this being achieved by appropriate energisation ofthe valves in the valve block and reservoirs unit 172.

In the embodiment of Figures 4 to 10, the deflecting force is applied to the drilling tube, in the desired magnitude and direction, to impart a curvaturetothe tube, as indicated at 124 in Figure 4. This controlled curvature controls the drilling direction. The reaction to the deflecting force is borne within the casing 154, the bearings 160,158 providing reactiveforces on the tube. It will be notedthatthe bore hole wall provides no reactive forces to the tube 110 through the intermediaryofthecasing 154.

Claims

1. Apparatusfordeflecting a rotatable drilling tube to control the drilling course, comprising actuating means which do not rotate with the drilling tube and which are disposed between two support means which supportthe drilling tube in a radial sense attwo positions spaced along the length ofthedrillingtube, the actuating means applying to the drilling tube a deflecting force which has a magnitude and direction to impart required curvaturetothe drilling tube between the two support means in orderto control the drilling course.

2. Apparatus according to claim 1 wherein the support means are stabilisers which engage the bore hole wall which provides a reaction force against the deflecting force applied by the actuating means.

3. Apparatus according to claim 1, wherein the support means are bearings which rotatably support the drilling tube within a casing disposed within the bore hole, the casing providing a reaction force against the deflecting force applied by the actuating means.

4. Apparatus according to any ofthe preceding claims, whereiti the actuating means are hydraulic pistons for applying the deflecting force with a controlled magnitude and radial direction.

5. Apparatus according to any of claims 1 to 3, wherein the actuating means comprise a plurality of flexible enclosures which are capabie of being pressurised by the fluid to impartthe deflecting force to the drilling tube.

6. Apparatus according to claim 5, wherein there are four similarflexible enclosures, symmetrically arranged at equi-angularly spaced positions around the drilling tube.

7. Apparatus according to claims 3 and 6, wherein the flexible enclosures are located in an annular space defined at its radially outer extent by the casing and at its radially inner extent by a bearing sleeve within which the drilling tube is rotatably mounted.

8. Apparatus for deflecting a rotatable drilling tube, constructed and arranged substantially as herein particularly described with reference to the accompanying drawings.