GB2281088A - Logging plug for use in oil, gas and other wells - Google Patents

Abstract

A logging plug (10) for use in conjunction with coiled tubing (12) on which a logging tool is deployed down a well, comprises a plug body (34) provided externally with sealing means (22) for a nipple (not shown) installed in the well and provided internally with passage means which allow the passage of the tubing (12) through the plug (10) and form a partial seal thereto. A transport means (16) is detachably connected to the plug body (34) and includes clamping means (14) for clamping around the tubing (12). The transport means (16) is arranged to draw the plug body (34) down the well with the tubing (12) as far as the nipple (26), thereupon to become detached from the plug body (34) to allow the continued passage of the tubing (12) down the well, and subsequently to carry the plug body (34) upwards on withdrawal from the well. <IMAGE>

Description

LOGGING PLUG FOR USE IN OIL, GAS AND OTHER WELLS Thia invention relates to logging plugs for use with coiled tubing in oil, gas and other wells.

To ascertain parameters of well operations auch as temperature1 pressure and flow rates one or more logging tools (gauges) are run down the well, often on a coiled tubing string. Coiled tubing is simply a long length of steel tubing, typically having a wall thickness of 3-4 mm and a diameter of 45 mm, or even more. Coiled tubing is used to transport logging tools into horizontal sections of wells where it is not possible to use wireline; it is also used to inject fluids into both horizontal and vertical wells.

Coiled tubing is ao named because it is supplied coiled onto a massive drum in a single length and is uncoiled at the surface, passed through straightening rolls, and fed directly into the well. The straightening process is somewhat inexact, especially on the larger sizes and this has led to serious problems with tool being bent by the coiled tubing and in some casea it has been impossible to assemble tools onto the coiled tubing.

As many of these operational parameters must be measured while the pressure in the perforation zoo is different from that obtaining in the upper part of the well down which the logging tool is run, it is necessary for the coiled tubing to be passed through a logging plug which maintains a good, but not perfect, seal with the coiled tubing, and which itself ii salable within a nipple incorporated in production tubing, by-pass tubing or the well casing.

In order to ensure that the logging plug is transported to the required position in the well production tubing, by-pass tubing or casing to effect the required seal within the nipple, it is necessary to secure the logging plug to ths coiled tubing until such time as the sealing elements of the logging plug are aeated within the nipple seal bore. The logging plug wuat then be released from the coiled tubing to allow the coiled tubing to be run down the well Where logging operations involve running the coiled tubing up and down the well it is desirable to provide a means for holding the logging plug securely in the nipple. This is necessary due to the natural curvature of the coiled tubing caused by its being unreeled from a drum at the well head.This curvature causes severe forces to be applied to the Logging pLug which would otherwise cause the logging plug to be unseated from the nipple and to be transported with the coiled tubing aa it gloves up the well. The means for holding the logging plug within the nipple is required to be releasable to facilitate removal of the coiled tubing together with the logging plug from the well at the desired time.

The use of increasingly large Biaraeters of coiled tubing has intensiìed the problems of undesirable stresses being applied to the logging plug and the resulting difficulties of attaching the logging plug to the coiled tubing.

St is an aim of the present invention to overcome or mitigate the problem of attaching the logging plug to coiled tubing with variable curvature whilst continuing to effect $ good, but not perfect, seal with the coiled tubing.

According to the prevent invention there is provided a logging plug for use in conjunction with coiled tubing (or other suspension means) on which a logging tool is deployed down a well for monitoring one or nore operational parameters, the plug comprising a plug body provided externally with sealing means for sealing to a nipple installed in the well and provided internally with passage means which allow the passage of tho tubing through the plug and form a partial seal thereto, transport means detachably connected to the plug body and including clamping meana for clamping around the tubing, the transport means being arranged to draw the plug body down the well with the tubing as far a9 the nipple, thereupon to become detached from the plug body to allow the continued passage of the tubing down the well, and to carry the plug body upwards on withdrawal from the well.

Preferably, the upper and lower portions of the plug body are connected through an artlculated joint to allow coiled tubing with considerable residual curvature to be passed through the plug.

PrefeuhbLy again, the logging plug further comprises locking means arranged to lock the plug body in the nipple on detachment of the transport means and to release the plug body from the nipple when the transport means are drawn upwardly against the plug body. The locking means may take the form of a series of axially-patallel spring finger. arranged around the plug body and to be held in an operative position in which they engage in an annular recess in the nipple bore by a apring-loaded locking sleeve which is moved to an operative position on detachment of the transport means from the plug body1 and which is returned to a non-operative position r which allows retraction of the fingers, by engagement of the transport means with the plug body.

In order to aid in underJtanding of the invention first and second embodimenta thereof will now be described with reference to the accompanying drawings, in which Figure 1 ia an elevation of a logging plug according to a first embodiment of the present invention attached to coiled tubing: Figure 2 is an axial section through the plug of Fig. 1: Figure 3 is a partial axial section through a nipple installed in a well; Figure 4 is an axial half section through a logging plug according to a second embodiment of the invention attached to coiled tubing; and, Figure 5 is a sequence of axial half section views of a variant of Figure 4 being installed in a nipple in a well.

With respect to the drawings the expressions "upper" and "above" are intended to refer to the well head direction, whilst the expressions "lower" and "below" refer to the down well direction.

Referring to Figures ] to X, the logging plog 10 is attached to the coiled tubing 12 by compressing a toothed ring 14 between the coiled tubing 12 and a shear-out sub 16 by screwing a sleeve 18 into the shear-out sub 16.

causing the teeth 20 on the internal fec. of the toothed ring 14 to bite into the external surface of the coiled tubing 12. It will be apparent that the design of the shear-out sub 16 enables it to be fitted to any type of coiled tubing system. Other method. of attachment may of course be employed.

The effective grip provided is sufficient to ensure that the logging plug 10 is transported down the well to the point where the- sealing elements 22 of the logging plug 10 are seated within the bore 24 of a nipple 26 at which time a shoulder 28 immediately above the sealing elements 22 locates on a corresponding Shoulder 30 at the top of the nipple seal bore 24, thus preventing the logging plug 10 from further travel down the well.

Spring fingers 32 located within the body 34 of the logging plug 10 are located ao as to coincide with an annular recess 36 below the nipple seal bore 24 when the logging plug 10 is satisfactorily seated within the nipple 26.

Downward force exerted due to the weight of the coiled tubing 12 causes shear pins 38, located so as to secure the shear-out sub element 16 to a ring 40 screwed into the body 34 of the logging plug 10 to shear through, thus separating a sub-assembly comprising the toothed ring 14, shear-out sub 16 and sleeve 18 from the upper part of the logging plug 10 allowing the coiled tubing to continue down into the well.

The shear-out of this lower sub-assembly permits a locking sleeve 41 to slide beneath the spring fingers 32 effectively holding the spring fingers 32 within the annular recess 36, thus preventing the upper section of the logging plug 10 from being removed from the nipple i6. A spring 42 provides sufficient force to ensure that the locking sleeve 41 is so positioned in relation to the spring fingers 32 as to cause an effective lock.

A sleeve 44 being a close, but not an exact, fit on the coiled tubing provides a good, but not perfect seal, prcventing substantial flow from above to below the logging plug 10.

When it is desirable to remove the coiled tubing from the well1 the coiled tubing is withdrawn until the shear-out element 16 coincides with the locking sleeve 41, compressing the spring 42 and thus allowing the spring fingers 32 to be deflected sufficiently to allow the logging plug 10 to be unseated from the nipple 26 and returned to surface.

In order to permit coiled tubing with considerable curvature to be passed through the sleeve 44 and the toothed ring 14 an articulated joint 46 is provided half-way down the logging plug 10, so as to permit its upper portion 34a to be inclined with respect to the lower portion 34b and thus enable the logging plug 10 to effectively correspond to the curvature of the coiled tubing 12; the maximum angle of inclination of the upper portion 34 is shown in chain dot in Fig. 1, The internal profiles of the coirponents of the logging plug 10 between the sleeve 44 and the toothed ring 14 are so shaped as to avid interference with the surface of the coiled tubing 12.

Referring now to Figure 4, which shows a second embodiment of the invention, parts corresponding to those of the first embodiment are identified by the sane numeral prefixed by the digit one.

The logging plug 110 has a body 134 encopassing a roll-on connector which is attached directly to the coiled tubing 112, this being a standard method of attaching logging tools to the end of a coiled tubing string. A collet 150 is housed within an outer housing 152 of the body 1a4 and extending from the upper end of the collet are set of upper collet fingers 154, each of which carries a portion of encircling inner and outer spring rings lSe̲,156b. Each upper collet finger 154 is supported on a shoulder 158 in the outer housing 152.A corresponding set of lower collet fingers 160 extend from the lower end of the collet 150 and are captured between a support sleeve 162 connected within the lower portion of the body 134b by shear pins 138 and an annular recess 1S4 formed in the upper end 165 of a release sub 170.

The release sub 170 is threadingly connected 172 at its down well end to a connector 180 which is equipped at its lower end 182 with a thread 184 for connection to a logging string (not shown).

Two sets of, respectively, upper and lower spring fingers 292a1132b are Located within the body 134 of the logging plug 110, Each spring finger 132a of the upper set is connected to the body 134 by a living hinge upwardly of a bulbous free end 135a lying adjacent the upper collet fingers 154. Whereas, each lower spring finger 132b is connected to the body 134 by a living hinge at each end thereof, whereby depression of a bulbous centre portion 135b of each lower spring finger 132b brings it into contact with a shoulder 141 on the collet 150. The lower spring finger set 132b is positioned on the body 134 so as to coincide with an annular recess located below a nipple seal bore when the logging plug is satisfactorily seated within the nipple.

Turning now to the sequence (a,b,c,d,e) shown in Figure 5, this illustrates a variant of the second embodiment in which corresponding parts are prefixed with the digit two and the down-hole direction is indicated by an arrow head marked D on the Figure.

In the variant, the release sub 270 is connected to the coil tubing 212 in a manner similar to that shown in the first embodiment whilst the lower set of spring fingers 232b are attached via living hinge at their upper ends only, so that depression of the free end brinas the bulbous portion 23Sb of each spring finger 232b into contact with the first shoulder 241 on the collet 250.

Figure 5o shots the logging plug 210 prior to entry into a the bore 224 of a nipple 226. The outer surfaces 237a,237b of the bulbous portions 23Sa,23Sb of the upper and lower sets of spring fingers 232a,232b stand proud of the surrounding external surface of the body 234, whilst their respective inner surfaces 239a,239b contact the outer spring ring 256a, and the first shoulder 241 of collet 250 respectively.

Figure 5 > shows tbe logging plug 210 partially inserted in to the nipple 226, The bulbous portion 235b of each lower spring finger 232b is depressed by the narrow bore 224 thereby urging its inner surface 239b into abutment with the first shoulder 241 provided on the collet 250.

Figure 5c shows the logging plug 210 with both upper and lower sets of spring fingers 232a,232b displaced inwardly by the narrow bore 224, The upper set of spring fingers 232a contact the outer spring ring 256a thereby accommodating any miss-alignment to ensure that all the upper collet fingers 254 are depressed evenly. The upper collet fingers 254 are depressed sufficiently to allow them to pass beneath the shoulder 258 in the housing 252 and are prevented fron doing so by the abutment between the first collet shoulder 241 and the bulbous ends 235b of the lower spring fingers 232b.

Figure 55l shows the logging plug 210 in position within the nipple 226 having an upper abutment portion (not shown) received in a seat 230 formed by the entrance to the bore 224. With the lower portion 234b of the body partially emerged from the narrow bore 224, the lower spring fingers 262b are free to expand into the annular space 236 thereby releasing the first collet shoulder 241. Continued downward movement of the coiled tubing 212 through the body 234 combined with the axial force provided by the spring 242 acting in an axial direction on the collet 250 causes the collect 250 to elide downwardly within the housing 252 until a second collet shoulder 251 abuts a corresponding stop on the inner surface of the housing.At this position the lower collet finger ends 261 have moved radially outwardly into an annular recess 263 provided in the support sleeve 262, thereby releasing the upper end 265 of the release sub 270 to continue down into the well with the tubing 212 as shown in Figure , The collet shoulder 241 prevents radially inward displacement of the bulbous ends Z3Sb of the lower spring fingers 232b to prevent the logging plug 210 from becomìno unseated during upward movement of the coiled tubing 212.

To recover the release sub the coiled tubing 212 is hauled upwardly bringing the release sub 270 into engagement with the support sleeve 262 and the lower collet fingers zaol Continued upward movement of the tubing 212 causes the above steps to occur in reverse thereby causing the logging plug 210 to be released from the nipple 226.

Should, for any reason, one or more lower collet fingers 260 become jammed within the recess 263 formed in the support sleeve 262, then continued upward hauling of the coiled tube 212 will cause the shear pins 238 to break allowing both sleeve 262 and collet fingers 260 to move upwardly within the housing 252 to allow recovery of the logging plug 210 in the normal manner.

Claims (16)

1. A logging plug for use in conjunction with coiled tubing or other suspension means an which a lagging tool is deployed down a well for monitoring one or more operation parameters, the plug comprising a plug body provided externally with sealing means for a nipple installed in the well and provided internally with passage means which allow the passage of the tubing through the plug and form a partial seal thereto, transport rneans detachably connected to the plug body and including clamping means for clamping around the tubing, the transport means being arranged to draw the plug body down the well with the tubing as far as the nipple. thereupon to become detached from the plug body to allow the continued passage of the tubing down the well, and subsequently to carry the plug body upwards on withdrawal from the well.

2. A logging plug as claimed in Clam 1, wherein the body includes lower and upper portions connected by an articulated joint in order that coiled tubing having residual curvature may be passed through the plug.

3. A logging plug as claimed in Claim 1 or Claim 2, wherein the body includes locking means arranged to lock the body in the nipple and effect detachment of the transport means and subsequently to release the body from the nipple when the transport means are drawn upwardly against the plug body.

4. A logging plug as claimed in any preceding Claim, wherein the locking means comprises a series of axiallyparallel spring fingers arranged around the plug body and to be held in an operative position in which they engage in an annular recess in the nipple bore by a spring loaded locking sleeve which is moveable to the operative position on detachment of the transport means from the body, and which is returned to a non-operative position, which allows retraction of the fingers, by engagement of the transport means with body.

5. A logging plug as claimed in Claim 4, wherein the plug body is provided with frangible connection means for securing the transport means thereto until such time as the transport is detached therefrom.

6. A logging plug as claimed in Claim 5, wherein the frangible connection weans includes at least one shear pin.

7. A logging plug as claimed in any one of Claims 1 to 3, wherein the locking means comprises first and second sets of axially parallel spring fingers arranged around the plug body with the first set held in an operative position in which they engage in an annular recess in the nipple bore by a spring loaded collet which is movable to the operative position on detachment of the transport means from the body, and which is subsequently returned to a non-operative position, which allows retraction of the first set of fingers, by engagement of the transport means with body, the arrangement being such that the second set of fingers are movable to a release position in which they are displaced by the nipple bore to allow the collet to move to the operative position.

8. A logging plug as claimed in Clam 7, wherein the plug body is provided with a sleeve for securing the transport means thereto in cooperation with said collet being in said non-operative position.

9. A logging plug as claimed in Claim 8, wherein the sleeve is connected to the plug body by frangible connection means, the arrangement being such as to allow engagement of the transport means with body when the collet is jammed in the operative position.

10. A logging plug as claimed in any one of Claims 7 to 9, wherein the collet includes axially parallel collet wingers extending from opposite ends thereof.

1l. A logging plug as claimed in Claim 10, wherein the seccind.eet of spring fingers are movable to displace the axially parallel collet fingers extending from one end of the collet.

12. A logging plug as claimed in Claim 10 or Claim 11, wherein the collet fingers extending from Said one end carry an annular spring.

13. A logging plug as claimed in any one of Claims 16 to 12, wherein the collet fingers extending from the other end of the collet are releasably engageable with said transport means.

14. A logging plug as claimed in Claim 1 and substantially as herein described.

15. A logging plug substantially as described herein, with reference to Figures 1 to 3, 4, or 5, of the accompanying drawings.

16. The featutes herein described, or their equivalents, in any patentable novel selection.