WO1985002674A1

WO1985002674A1 - Device for measuring internal dimensions of tubes

Info

Publication number: WO1985002674A1
Application number: PCT/GB1984/000426
Authority: WO
Inventors: Eric John Atherton
Original assignee: Hanson Research Limited
Priority date: 1983-12-13
Filing date: 1984-12-10
Publication date: 1985-06-20
Also published as: GB8333190D0; EP0177505A1; GB8519983D0; GB2161272A

Abstract

A measuring apparatus for measuring the internal dimensions of a tube such as a pipe in an oil well includes a central body (1) and number of lateral extending measuring arms comprising pivoted links (31, 32). The links are mounted on the body via slider mechanisms (8, 9, 13, 22) so that the displacement of the inner link end provides a measurement of arm extension. The displacement is measured by a variable inductance device (21, 47), the electrical components of which are shielded from external pressure.

Description

DEVICE FOR MEASURING INTERNAL DIMENSIONS OF TUBES DESCRIPTION

This invention relates to measuring apparatus for measuring the internal dimensions and surface variations of tubular structures such as pipes and cylindrical casings. It is likely that the main application of this invention will he for use in measuring the internal dimensions of pipes and casings of oil wells.

It will he understood that due to corrosion or ahrasion the physical strength of the walls of pipes in oil wells can he reduced to dangerous levels.

Casing calipers can he used to investigate the integrity of oil well casings hy introducing the caliper tool into the pipe or casing in situ. An accurate caliper survey can provide indications of future problems, and is a non-destructive test. Other techniques such as pressure testing are destructive when a fault is present. Known multifinger caliper tools invariably use radially projecting fingers to contact the interior surface of a pipe or casing into which the tool is introduced. The fingers are such that when extended the tool can only be moved one way through the pipe. It is necessary therefore to use a latch mechanism to hold the feelers in a retracted state while the tool is introduced down the well. At the deepest point of descent the latch is released, the feelers spring open, and the tool is then moved upwardly to measure the diameter and surface configuration by the caliper action of the extending feelers, Various latch mechanisms have been suggested, for example, the use of a drive wheel against the inner surface of the tube being measured. Such an arrangement is described in U.S. patent specification 2908085 at page 16, line 28. An alternative proposal is a mechanical release dog/arm mechanism such as that described in G.B. 2066470. All these mechanisms suffer from great m mechanical complexity. As a further alternative, solenoid type latches have been proposed. These need to be fed with high power and require connectors enabling the electrical conductors or mechanical linkage to pass from high pressure to normal pressure regions within the tool. Such connectors are preferably avoided as they are a common source of equipment failure.

A major problem with all types of caliper tools with latches arises from the fact that to verify the data obtained from a down hole tool it is highly desirable to run over the same section of the pipe again, and hence that it is necessary to have a second descent phase. It is not possible to do this with a latching type caliper arrangement without withdrawing the tool and resetting the latch. It will be appreciated that irregularities in the interior surface of the pipe may not be smooth, so that to attempt to descend such a caliper tool with its feelers extended may result in the feelers snagging on a jutting irregularity.

It has been proposed to overcome this problem by opening and closing the caliper mechanism using an electric motor. This however entails a high degree of complexity to achieve reliability in the high pressure and generally hostile environment that is encountered down the well. Another reason for mechanical complexity in known caliper tools is the need for a relatively linear relationship between the radial movement of the feelers and the ultimate movement of the transducer.

The present invention seeks to provide an improved measuring device for measuring the internal surface of the tubular structure.

In a first aspect, the present invention provides, measuring apparatus for measuring the internal dimensions of a tubular structure comprising a central body and a plurality of arms adapted for movement outwardly of the central body, thus to contact the interior of a tubular structure when the apparatus is placed therein, characterised in that each of the arms comprises two parts or portions extending outwardly from the body from longitudinal spaced locations and being pivotally joined at their outward ends, each of the parts or portions being pivotable with respect to the body at its inner end and being mounted at its inner end for displacement movement relative to the body; the apparatus including means for limiting the displacement movement of each inner end in a respective direction corresponding to the outward extension of the arm; and wherein the mounting of the inner end of at least one of the parts or portions comprises a mounting providing for translational movement of that end relative to the body, and wherein the apparatus includes means for measuring translational movement of the inner end of said one part or portion and hence the outward extension of the arm.

The arms may, for example, comprise a unitary arcuate spring contacting the interior of a tube intermediate its ends. The two portions of the spring on each side of this point of contact constitute the two outwardly extending portions as aforesaid.

In a preferred embodiment however the parts of each of the arms comprises a pair of substantially rigid link elements. The mounting of the inner end of said link elements for translational movement relative to the body may comprise a slider to which the link element is pivotally mounted, which slider is slidably mounted on the body and biased toward a position at which the pivoted link elements are outwardly extended. Said means for limiting the displacement movement may comprise a stop abutting part of the slider at the limiting position.

The means for measuring the translational movement of said link element may comprise a coil located to receive a rod attached to said slider; the rod being of a material such that the inductance of the coil is modified by the degree of insertion of the rod; and means for measuring the inductance of the coil.

Preferably, the coil is located in region of the apparatus protected from the pressure in the tubular structure, the coil having a tube running through it; the interior of which is at external pressure and within which the rod is situated.

In preferred embodiments both link elements are mounted at their inner ends on respective sliders for translational movement relative to the body, both sliders being biased towards a position at

which the pivoted links are outwardly extended, the bias on one slider being greater than that of the other such that during measurement movement of the tool one remains stationary in response to inward movement of the arms until the other reaches a limit to its travel.

The arms may include rollers at their outward extremities which rollers provide the contact surface of the arms with the internal surface of the tubular structure. The rollers may be pivoted coaxially with pivotal axis of the first ends of the links.

In a second aspect, the present invention provides apparatus for use with, or substantially comprising, a tool to be inserted within a tubular structure, comprising a central body and at least one arm adapted for movement outwardly of the central body, thus to contact the interior of the tubular structure when the apparatus is placed therein, characterised by the inclusion of a latch mechanism operative to hold the arm in a retracted position, the latch being released by heating.

The latch mechanism may comprise a heat-activated release member holding the arm retracted.

The release member may be located at external pressure within a pressure barrier comprising a tube, adjacent which heating means, shielded from external pressure, is located.

In each of the aforementioned aspects the apparatus may be a tool adapted for use in logging tubes and casings, in situ, in a well.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings. In the drawings:-

Figure 1 is an axial section through one half of a measuring tool in accordance with the invention, and

Figure 2 is a simplified axial section through one half of the measuring tool, illustrating a measuring arm in an extended position. This embodiment of the invention is for measuring the internal diameter of a tube and in particular the casing or tubing of an oil well. The apparatus comprises a tubular cylindrical body member 1, on whose exterior surface other parts of the apparatus are secured. The body member 1 is made from stainless steel and comprises parts 1a and 1b spaced apart in an axial direction. A sensor support body 2 comprises a cylindrical outer portion with two inwardly directed annular flanges 2a and 2b one at the top and one at the bottom of the outer portion. The sensor support body 2 bridges the gap between the parts 1a and 1b of the tubular body member 1, and the inner circumferential surfaces of the flange portions 2a and 2b abut, and are sealed against, the outer surface of respective parts 1a and 1b of the tubular body member. In this manner a cylindrical cavity is defined between the bores of the parts 1a and 1b of the tubular body member. The tubular body member and the sensor support body 2 act as a pressure housing such that the internal bores of the parts 1a and 1b and the cavity 3 are protected from the pressure external to the apparatus and may be maintained at normal atmospheric pressure. Upper

and lower locking rings 4a, 4b align and secure the sensor support body 2 with the parts of the tubular body member 1.

Upper and lower cylindrical outer shells 5a and 5b are located around respective parts of the tubular body member 1a and 1b. Each cylindrical outer shell has an external diameter equal to the external diameter of the sensor support body 2 and the lower and upper ends respectively of the shells 5a and 5b are seated on the chamfered exterior edge portion of the sensor support body 2. Angled screws 6 fit through the parts of the shells 5 and secure the parts of the outer shells to the sensor support body 2. The upper shell 5a comprises two semi-cylindrical parts joined longitudinally, and each part has 16 vertical slots 7 circumferentially disposed at equal spacings. The slots enable 32 caliper arms to be extended and retracted into the space outside the outer shell 5a as is described below.

Disposed about the tubular body member 1 between the body member and the outer shell 5a are 32 pairs of slider mechanisms each corresponding in position to one of the vertical slots 7. The pairs of slider mechanisms each comprise an upper slider 8 and a lower slider 9, each slider being mounted for sliding movement parallel to the longitudinal axis of the apparatus. The upper slider comprises an elongate main portion 10, and an annular lateral flange 11 at its lower end. Intermediate the ends of the elongate main portion 10 the upper slider has a boss portion 12 extending Laterally towards the outer shell 5. The boss portion acts as both an abutment and as a pivotal mounting, and is described further below. The upper slider is mounted on one of two semi-cylindrical slider carriers 13 fixed to the tubular body member 1. Each slider carrier mounts 16 of the sliders. The carrier 13 comprises a vertical portion fixed to the outer surface of the body member 1 by screws 14, and has upper and lower transverse projecting portions 15 and 16, these being semi-circular in outline. The transverse portions 15 and 16 of the slider

carrier each have 16 co-axial bores with "Teflon" sleeve bearings 17. A slider is located through one of the bearings 17 such that in its normal position, the boss 12 rests on the lower projecting portion 16 of the carrier and the portion of the slider between the boss and the annular flange 11 extends downwardly from the slider carrier 13 towards the lower slider 9.

The lower slider 9 has a main portion 18 and a boss portion 19 analogous to the upper slider 8. It also has an annular flange 20 located at its upper end. At its lower end the slider 9 has fixed thereto a measuring rod 21 extending downwardly from the lower slider co-axial therewith. The lower slider 9 is mounted on one of two semi-cylindrical slider carriers 22. The lower slider carrier 22 includes upper and lower projecting portions 23 and 24 to which the lower sliders 9 are mounted via sleeve bearings 25 in a similar manner to the mounting of the upper sliders on the upper slider carrier 13. The two lower slider carriers 22 mounted around the tubular body member are secured by screws 26 to a release sleeve 27. The release sleeve 27 is located closely around the tubular body member 1 but enabled to slide longitudinally with respect thereto. The upper limit of travel of the release sleeve 27 is determined by a stop 28 which engages against an abutment surface at the end of a slot in the wall of the tubular body member 1. The normal position of the release sleeve 27 is its uppermost position with the stop 8 abutting the end of the slot. The release sleeve 27 is biassed to this position by a coil spring 29 fixed between the upper surface of the sleeve 27 and a fixing bolt 30. A measuring arm is associated with each of the pairs of sliders and may be extended and retracted through the slots 7 of the outer sleeve 5. Each measuring arm comprises a pair of pivoted link arms each of which is pivoted at its free end to a respective boss portion 12, 19 of the upper or lower slider 9. At their mutual pivotal connection, the link arms 31 and 32 are fitted with a measuring wheel 33, mounted on the same pivot pin as links the two arms 31 and 32.

Each of the sliders has an associated compression coil spring 34, 35 located between the underside of the flange on the slider 11, 20 and the facing surface of the nearest lateral projection 16, 23 of the respective slider carrier. The springs 34 and 35 bias the sliders to the positions shown in Figure 2 such that the two link arms 31 and 32 are at an angle of approximately 90° and the pivotal joints between each pair of link arms and their measuring wheels 33 are extended through the corresponding vertical slots 7 into the region outside the apparatus. Further extension of the arms diametrically of the apparatus is prevented by the boss portions 12, 19 of the upper and lower sliders which bear on the surface of the projections 16 and 23 of the respective slider carriers. The upper slider spring 34 is constructed to apply considerably more force to the upper slider than is the lower slider spring 35 to a lower slider. Therefore any inward displacement of the measuring wheel 33 diametrically

of the tool causes downward movement of the lower slider 9 in preference to upward movement of the upper slider 8.

In axial alignment with each pair of sliders is a narrow pressure tube 35 extending through bores in the circular flanges 2a and 2b of the sensor support body 2, such that the middle portion of the tube extends through the cylindrical cavity 3 parallel to its axis. The pressure tube 35 has a length longer than the overall length of the sensor support body 2 such that the end regions of the pressure tube 35 project from the surface of the support body 2. The ends of the pressure tube 35 are both open. In association with one or more of the slider mechanisms a further pressure tube 36 is provided, spaced between the pressure tube 35 and the tubular body member 1. The further pressure tube 36 is of the same dimensions as the tube 35. Upper and lower oil bath assemblies 37 and

38 are disposed respectively on the upper and lower surfaces of the sensor support body 2 and locate against the outer cylindrical wall of the tubular body member 1. The upper oil bath assembly 37 is located and aligned with respect to the sensor support body 2 by means of screws 39. Corresponding screws secure the lower oil bath assembly 38 to the underside of the support body 2. The oil baths may be drained and filled via plugs 40 in their circumferential surfaces. The lower wall of the lower oil bath assembly 38 has an orifice 41 communicating with an annular bellows 42 sealed to the undersurface of the oil bath.

The measuring rod 21, fixed to the end of the lower slider 9, extends into the pressure tube 35 through an aperture in the upper surface of the upper oil bath assembly 37. A wiper 43 extends as a sleeved insert within this aperture and provides a fluid seal for movement of the measuring rod 21 into and out of the pressure tube 35.

A release pin 44 is fixed to the underside of the release sleeve 27 in axial alignment with the further pressure tube 36 by way of a further aperture in the upper oil bath assembly and an associated additional wiper. A release pin sleeve 45 is fixed in position within the lower part of the pressure tube 36 and is dimensioned to receive the lower end of the release pin 44. In the initial position of the release sleeve 27

(not shown in the drawings) it is located downwards of its position shown in the drawings such that the spring 29 is extended and under tension and the link arms 31 and 32 are co-linear and thus fully retracted. The release pin 44 is held by solder in the release pin sleeve 43. An electric heating coil 47 is located within the cylindrical cavity 3 around that portion of the pressure tube 36 extending through the cavity. The passage of current through the heating coil 46 melts the solder and enables the release sleeve 27 to be pulled to its upper position by the spring 29.

Surrounding the portion of the pressure tube 35 within the cylindrical cavity 3 is a linear transformer 47. The measuring rod 21 is made from soft iron and its longitudinal movement into and out of the portion of the pressure tube surrounded by the transformer 47 changes the mutual inductance of the transformer.

This inductance is measured electrically to give an indication of the longitudinal position to the lower slider 9. The position of the lower slider 9 is determined by the extension and retraction of the links 31 and 32 of the measuring arm. Thus by moving the apparatus through a pipe whose diameter is to be measured the wheel 33 rideson the inner surface of the pipe and changes in diameter are sensed by retractions and extensions of the wheel 33 in radial directions. As has been mentioned these movements are accommodated in normal circumstances by movement of the lower slider 9; the upper slider remaining fixed because of the greater spring bias upon it. Thus the movement of the measuring rod 21 is sensed by the linear transformer 47 provides a measurement of the lateral measuring arm. All 32 circumferentially disposed measuring arms are sensed by a respective linear transformer and the results are transmitted by a wireline cable to the surface where a processor analyses these signals and is able then to compute the diameter and the shape of the pipe along its length.

The bellows 42 function to equalise the pressure across the wiper seal 43 and also to provide means for variable displacement of the lower surface of the lower oil bath thereby preventing pumping forces, which might otherwise restrict movement of the measuring rod 31 within the pressure tube 35.

It should be appreciated that the apparatus may be used both while it ascends and descends to take measurements of theinternal surface of a pipe. It is unnecessary to provide motorised extension of the measuring arms or to withdraw the apparatus for relatching.

The apparatus will however principally be used for measuring when ascending through the pipe. When moving in this direction the wireline cable is taut and the position of the tool is therefore more accurately known. Nevertheless the tool may be descended with the arms extended. If during descent the lower link arm encounters a snag, the upper slider 10 moves upwardly allowing the arm to be retracted and the snag bypassed. The latching mechanism provided by the movable release sleeve 27 and the soldered connection of the release pin 44 in the sleeve 45 is an optional feature which is useful to assist the descent of the apparatus through a high deviated oil well. Such a well usually returns vertical at the bottom of the well so that several repeat ascends and descends of the apparatus, to increase the number of readings, may still be made in such a well after the tool is unlatched. This particular latch mechanism has great mechanical simplicity and reliability but requires little power and can unlatch a high mechanical force.

The electrical connections both to the heater coil 46 and from the linear transformer 47 are all at normal pressures and there is no requirement for a feed-through, electrical

connectors into a high pressure zone.

The problems of linearity in the response of the movement of the measuring rod within the linear transformer are not corrected mechanically but rather an overall systems correction of linearity is applied to each of the measurement signals using look-up tables in the central processor prepared for each of the arms.

The measuring arms mounted on the semi-cylindrical removable slider carriers 13, 22 may be removed by removing the parts of the casing 7 and unscrewing carriers 13, 22 so that the change to a different arm size is a quick and simple procedure involving merely the changing, as units, of the carriers with the measuring arms on them.

Claims

1. Measuring apparatus for measuring the internal dimensions of a tubular structure comprising a central body and a plurality of arms adapted for movement outwardly of the central body, thus to contact the interior of a tubular structure when the apparatus is placed therein, characterised in that each of the arms comprises two parts or portions extending outwardly from the body at longitudinally spaced locations and being pivotally joined at their outward ends, each of the parts or portions at its inner end being pivotable with respect to the body and being mounted at its inner end for displacement movement relative to the body; the apparatus including means for limiting the displacement movement of each inner end in a respective direction corresponding to the outward extension of the arm, and means for measuring the displacement movement of the inner end of at least one of the parts or portions of each arm and hence the outward extension of the arm.

2. Measuring apparatus as claimed in claim 1 characterised in that the parts of each arm comprise a pair of substantially rigid link elements.

3. Measuring apparatus as claimed in claim 1 characterised in that the arms each comprise a single arcuate spring contacting the interior of the tube intermediate its ends.

4. Measuring apparatus as claimed in claim 2 characterised in that the mounting of the inner of a link element for displacement movement relative to the body comprises a slider to which the link element is pivotally mounted, which slider is slidably mounted on the body and biased toward a position at which the pivoted link elements are outwardly extended.

5. Measuring apparatus as claimed in claim 4 characterised in that said means for limiting the displacement movement comprises a stop abutting part of the slider at the limiting position.

6. Measuring apparatus as claimed in claim 4 or claim 5 characterised in that said means for measuring the displacement movement of said link element comprises a coil located to receive a rod attached to said slider, the rod being of a material such that the inductance of the coil is modified by the degree of insertion of the rod, and means for measuring the inductance of the coil.

7. Measuring apparatus as claimed in claim 6 wherein the coil has a tube running through it within which the rod is situated, the coil being located in a region of the apparatus not subject to the external pressure in said tubular structure, whereas the interior of said tube is at said external pressure.

8. Measuring apparatus as claimed in claim 4 wherein both link elements of each arm are mounted at their inner ends on respective sliders, both sliders being biased towards a position at which the pivoted links are outwardly extended, the bias of one slider being greater than that of the other such that during measurement movement of the tool one remains stationary in response to inward movement of the arms until the other reaches a limit to its travel.

9. Measuring apparatus as claimed in claim 8 wherein the arms include rollers at their outward extremities, which rollers provide the contact surface of the arms with the internal surface of the tubular structure.

10. Apparatus for insertion within a tubular structure, comprising a central body and at least one arm adapted for movement outwardly of the central body thus to contact the interior of the tubular structure when the apparatus is placed therein, characterised by the inclusion of a latch mechanism operative to hold the arm in a retracted position, the latch being released by heating.

11. Apparatus as claimed in claim 11 wherein the latch mechanism comprises a heat-actuated release member holding the arm retracted, the release member being located so that in use it is at the pressure inside the tubular structure with a tube providing a pressure barrier and adjacent which heating means, thereby shielded from external pressure, is located.