Downhole apparatus and method for expanding a tubing

Downhole apparatus is disclosed for use in expanding liner or tubing. The apparatus comprises a body for connection to a string and an expansion portion on the body. The expansion portion includes a plurality of radially movable parts for defining an outer surface thereof. The parts are initially arranged in an axially and circumferentially offset first configuration in which the parts may assume a smaller diameter first configuration. The apparatus is then run Into a borehole and through a length of expandable tubing. The parts are the moved radially outwardly and axially aligned such that the parts assume a larger diameter second configuration and define a substantially continuous outer circumference. The expansion portion is then pulled through the tubing to expand the tubing.

This invention relates to downhole apparatus and in particular to apparatus 
for use in expanding liner or tubing. The invention also relates to a 
method of expanding tubing. 
WO-A-93/25800 (Shell Internationale Research) describes a method of 
completing an uncased section of a borehole in an underground oil-bearing 
formation. A liner provided with overlapping longitudinal slots is fixed 
at a predetermined position in the borehole. A tapered expansion mandrel 
or cone is then moved through the liner and expands the liner to a 
diameter larger than the cone maximum diameter. Ideally, the liner is 
expanded to such an extent that it contacts the bore wall. In one 
application, the slotted liner supports the borehole wall while permitting 
oil to flow from the formation into the bore. In other applications the 
liner is expanded into soft cement, and after the cement has set the bore 
is drilled out to the diameter of the expanded liner. 
The liner may be run into the borehole with the cone already positioned at 
the liner upper or lower end, or the cone may be run in after the liner is 
fixed in the borehole. The latter operation requires provision of a cone 
with a smaller diameter configuration such that the cone may be passed 
through the bore casing and then expanded to a larger diameter 
configuration before being pulled or pushed through the liner. 
WO-A-93/25800 discloses one form of expandable cone, however the disclosed 
arrangement produces an expanded cone with a non-continuous circumference, 
resulting in non-circular expanded liner. This reduces the effective 
diameter and surface area of the liner, and results in the liner being 
spaced from the bore wall at a number of locations around the liner 
circumference; all of these features of the liner tend to reduce its 
effectiveness in terms of formation control and subsequent management. 
It is among the objects of embodiments of the present invention to provide 
an expansion mandrel or cone which may assume a smaller diameter first 
configuration to allow running in through an unexpanded liner but which, 
in a second configuration, will maintain a larger diameter for expanding 
liner to a substantially circular form. 
According to the present invention there is provided downhole apparatus for 
use in expanding tubing, the apparatus comprising a body for connection to 
a string and an expansion portion on the body which may be arranged to 
define a smaller diameter first configuration for running in and a larger 
diameter second configuration for expanding the tubing, the expansion 
portion including a plurality of radially movable parts for defining an 
outer surface thereof and which parts are axially and circumferentially 
offset for movement between the first and second configurations, and are 
axially alignable in the second configuration to define a substantially 
continuous outer circumference. 
According to another aspect of the present invention there is provided a 
method of expanding tubing, the method comprising the steps of: 
providing apparatus comprising a body for connection to a string and an 
expansion portion on the body, the expansion portion including a plurality 
of radially movable parts for defining an outer surface thereof; 
arranging the parts in an axially offset first configuration in which the 
parts may assume a smaller diameter first configuration; 
mounting the apparatus on a string; 
running the apparatus into a borehole and through a length of expandable 
tubing; 
circumferentially offsetting the parts; 
moving the parts radially outwardly and axially aligning the parts whereby 
the parts assume a larger diameter second configuration to define a 
substantially continuous outer circumference; and then 
pulling the expansion portion through the tubing to expand the tubing. 
The present invention thus avoids the disadvantages of existing proposals, 
in which the expansion mandrel or cone is made up of solely radially 
movable parts, to allow the parts to assume a smaller diameter 
configuration the parts must be circumferentially spaced when in the 
larger diameter configuration. In the present invention the ability to 
axially offset the parts obviates the need for such spacing. 
Preferably, two sets of expansion portion parts are provided, each set 
comprising a plurality of circumferentially aligned parts with spaces 
therebetween to accommodate the other parts when each set is in the larger 
diameter second configuration. The parts may be configured to allow one 
set of parts to be radially extended to the second configuration and the 
sets then axially aligned before the other set is extended. 
Preferably also, the apparatus includes means for moving the parts between 
the first and second configurations. The moving means may utilize 
mechanical forces transferred through the string but preferably utilise 
fluid pressure forces created by fluid pumped into or through the string 
and body. Thus, the body preferably defines a bore including a restriction 
to permit creation of a pressure force which may be utilised to drive a 
piston arrangement linked to the parts. 
Preferably also, the apparatus includes means for retracting the parts from 
the second configuration to the first configuration. Most preferably, the 
retracting means is in the form of a biassing arrangement, conveniently a 
spring. Alternatively, the retracting means may be fluid pressure actuated 
and in such an apparatus fluid pressure may also be utilised to actuate 
means for moving the parts from the first to the second configuration. In 
one such apparatus valve means is provided to allow a fluid pressure force 
to move the parts in one direction from the first to the second 
configuration and then in the opposite direction from the second to the 
first configuration. The valve means may be actuated by, for example, 
application of an over-pressure to move a valve member from a first 
configuration to a second configuration. Such a valve means may be 
provided in conjunction with retracting means including a biassing 
arrangement, for use in the event of failure of the biassing arrangement. 
The parts may take various forms including; pivotally mounted or flexible 
fingers, the free ends of which may be extended by axial movement of the 
fingers relative to appropriate cam surfaces; or radially moveable keys, 
which may be extended by axial movement of the keys relative to 
appropriate cam surfaces. Where the parts are in the form of flexible 
fingers, the parts may normally define a larger diameter in the first 
configuration, but be inwardly deflectable to the smaller diameter; in the 
second configuration the fingers are supported such that they are not 
deflectable. 
According to a further aspect of the present invention there is provided 
downhole apparatus comprising a body for connection to a supporting string 
and a portion on the body which may be arranged to define a smaller 
diameter first configuration and a larger diameter second configuration, 
said portion including a plurality of radially movable parts which are 
axially and circumferentially offset in the first configuration, and are 
axially aligned in the second configuration. 
According to a still further aspect of the present invention there is 
provided fluid pressure actuated downhole apparatus including: a body 
defining a bore; an annular actuating piston movable in the bore; and a 
valve piston movable relative to the actuating piston by application of 
bore fluid pressure, in a first position the valve piston permitting fluid 
pressure in the bore to be communicated to one side of the actuating 
piston and in a second position the valve piston permitting fluid pressure 
in the bore to be communicated to the other side of the actuating piston.

Reference is first made to FIG. 1 of the drawings, which illustrates 
downhole apparatus 10 for use in expanding slotted tubing in accordance 
with a first embodiment of the present invention. The apparatus comprises 
a tubular body 12 which is connected to the lower end of a drillstring 14 
and carries an expansion portion including first and second sets 16, 17 of 
pivoting cone-forming fingers. In a first configuration, as illustrated in 
FIG. 1, the fingers 16, 17 define a diameter smaller than that of the 
slotted tubing 18 which the apparatus will be used to expand, such that 
the apparatus 10 may be run in through the tubing 18. As will be 
described, the fingers 16, 17 may thereafter be moved to a larger diameter 
second configuration (FIG. 2) such that the apparatus 10 may be pulled 
upwardly through the tubing 18 to expand the tubing into contact with the 
bore wall. 
Each set of fingers 16, 17 is mounted on a respective trolley or carriage 
20, 21 which is axially movable relative to the body 12, each carriage 
including load transfer keys 22, 23 extending through respective slots 24 
in the body 12 and engaging a respective part of an actuating arrangement 
26, further details of which will be described. In this example, each set 
16, 17 includes three fingers, and each set is offset 60.degree. from the 
other. FIGS. 1a and 1b of the drawings illustrate the finger free ends 28, 
29 in the smaller diameter first configuration. 
The upper face of each second carriage 21 defines a cam surface in the form 
of a ramp 30 such that when the first set of fingers 16 is moved 
downwardly relative to the carriage 21, the free ends of the fingers 28 
ride up the ramp 30 to assume the larger diameter configuration. A similar 
effect is achieved for the second set of fingers 17 by a cam surface in 
the form of a ramp 31 defined by an enlarged lower body end portion 32. 
The upper end of the body 12 defines a spring chamber 34 accommodating a 
coil spring 36 which normally biases the actuating arrangement 26 to a 
position in which the fingers 16, 17 are in the first configuration. The 
actuating arrangement 26 includes an inner sleeve 38, the upper end of 
which carries a collar 40 extending into the spring chamber 34, and which 
carries on its inner surface a sleeve 42 defining a restriction 44. The 
lower end of the inner sleeve 38 is connected to the carriage 20 via the 
load transfer keys 22 and also provides mounting for spring fingers 46 
which protect a sleeve 48 linked to the second carriage 21 by the keys 23. 
To move the fingers 16, 17 from the first configuration to the second 
configuration, a ball 50 is pumped down the drill string 14 from the 
surface and engages the restriction 44 effectively sealing the lower end 
of the string. Pumping down on the ball 50, in this example to a pressure 
of 77.3 kg/cm.sup.2 (1100 psi), creates a pressure force which drives the 
actuating arrangement 26 downwardly. As the actuating arrangement begins 
to move the first carriage 20 is moved downwardly on the body 12, however 
the second carriage 21 does not move immediately. Thus, the first set of 
fingers 16 ride up onto the carriage 21 to assume the larger diameter 
second configuration. Continued movement of the actuating arrangement 26 
brings the lower end of the first carriage 20 into contact with the upper 
end of the second carriage 21, and thus pushes the second carriage 21 
downwardly such that the second set of fingers 17 ride up onto the body 
end portion 32. As will be noted from FIGS. 1a, 1b and 2a, the edges of 
the sets of fingers 16, 17 are configured such that the second set of 
fingers 17 may be expanded radially outwardly between the previously 
expanded first set of fingers 16. 
With the fingers 16, 17 in the larger diameter second configuration, the 
apparatus 10 is lifted on the drill string through the tubing 18, forcing 
the tubing 18 to expand into contact with the bore wall. As is evident 
from FIG. 2a, the configuration of the free ends of the fingers is such 
that the expanded fingers define a substantially continuous circumference, 
such that the expanded tubing has a circular form. 
In normal operation, following the expansion of the tubing 18, bleeding-off 
of pressure above the ball 50 will allow the spring 36 to lift the 
actuating arrangement 26 to retract the fingers 16, 17 to the smaller 
diameter first configuration, such that the apparatus 10 may be retrieved 
from the bore hole. However, if the spring 36 should fail, or a part of 
the apparatus 10 has been damaged or jams such that the spring 36 does not 
produce sufficient force to return the fingers 16, 17 to the first 
configuration, fluid pressure may be utilised to lift the fingers, as will 
now be described. As noted above, the restriction 44 which engages the 
ball 50 is defined by a sleeve 42 mounted on the inner sleeve 38. The 
sleeve 42 is held in place by shear pins 52 such that by application of an 
overpressure, in this example around 280 kg/cm.sup.2 (4000 psi), the pins 
52 will shear allowing the ball 50 and sleeve 42 to move downwardly to 
abut a shoulder 54 on the inner surface of the sleeve 38, as shown in FIG. 
3. This movement brings a shear pin port 56 on the sleeve 42 into 
alignment with a shear pin port 58 in the sleeve 38. Thus, the fluid 
pressure from the string and apparatus bore can now be communicated into 
the spring chamber 34, below the collar 40. This drives the collar 40, and 
the rest of the actuating arrangement 26, upwardly such that the fingers 
16, 17 are returned to the smaller diameter first configuration. To 
accommodate the displacement of fluid from the portion of the spring 
chamber 34 upwardly of the collar 40 a burst disc 60 is ruptured to allow 
fluid to flow from the chamber 34 into the bore hole annulus. 
Reference is now made to FIGS. 5 and 6 of the drawings, which illustrate 
downhole apparatus 70 for use in expanding slotted tubing in accordance 
with a second embodiment of the present invention. It should be noted that 
in these drawings the "upper" end of the apparatus 70 is located to the 
left hand side of the drawings. The apparatus 70 comprises a tubular body 
72 for connection to the lower end of a drill string (not shown) and 
defining two sets of windows 74, 75 accommodating respective sets of keys 
76, 77. An axially movable sleeve 78 is mounted within the body 72 and is 
biassed towards a first position by a coil spring 80 which acts between 
the sleeve 78 and the body 72. The sleeve 78 defines an annular surface 82 
and with the sleeve in its first position the surface 82 supports the keys 
76, 77 in a smaller diameter first configuration, in which the apparatus 
70 may be run through a length of slotted tubing 84. The sleeve 78 also 
defines a second surface 86 on which the keys 76, 77 may be supported in a 
larger diameter second configuration, as shown in FIG. 6 of the drawings. 
The lower end of the body 72 includes a collar 88 defining a bore 
restriction which restricts downward movement of a ball 90 located within 
the bore. Thus, while running in, the ball 90 may be lifted from the 
collar 88 allowing well fluid to flow into the apparatus 70 and drill 
string. However, on pumping down through the drill string and apparatus 
70, the ball 90 is pushed against the collar 88 to seal the bore such that 
the pressure within the bore rises. The sleeve 78 is configured such that 
a positive pressure differential between the body bore and the borehole 
annulus will tend to drive the sleeve 78 upwardly and thus move the keys 
76, 77 from the first configuration to the second configuration, as will 
be described. 
Each set of keys consists of three keys, and each set is circumferentially 
offset relative to the other by 60.degree.. In the first configuration the 
keys 76, 77 are also axially offset, as may be seen in FIG. 5a. 
Accordingly, the windows 74, 75 are also circumferentially and axially 
offset, as may be seen in FIG. 5a of the drawings 
Upward movement of the sleeve 88 relative to the body 72 first lifts the 
first set of keys 76 radially outwardly as a ramp portion 92 between the 
surfaces 82, 86 engages the inner lower face of the keys 76. Initially, 
axial movement of the keys 76 is prevented by the window upper walls 94. 
However, as the keys 76 are moved outwardly each window wall 94 is brought 
into alignment with an axial slot 96 in the respective key, which allows 
the keys 76 to be moved into axial alignment with the second keys 77 on 
the ramp 98 at the lower end of the second surface 86 engaging the inner 
lower face of the keys 76. The second set of keys 77 is moved outwardly by 
the ramp 92 coming into contact with the inner lower face of the keys 77. 
Thus, at the end of the stroke of the sleeve 78, the keys 76, 77 are 
axially and circumferentially aligned, as illustrated in FIG. 6a, to 
define the larger second diameter, ready to be pulled through the tubing. 
The keys 76, 77 are returned to the smaller diameter second configuration 
by bleeding off pressure from the bore, such that the spring 80 returns 
the sleeve 78 to its initial position, Attempting to pull through a 
restriction after pressure is bled off will cause the keys to collapse 
inwardly should the spring fail. 
Reference is now made to FIGS. 7 and 8 of the drawings, which illustrate 
downhole apparatus 150 for use in expanding tubing in accordance with a 
third embodiment of the present invention. The apparatus 150 includes a 
tubular body 152 for connection to a drill string 154. Mounted to the 
lower end of the body 152 is a spring finger mounting assembly 156 from 
which three spring fingers 158 with enlarged free ends 160 extend axially 
downwards. The assembly 156 also defines an outer face of a spring and 
piston chamber 162, the inner face of the chamber 162 being defined by a 
piston and cam assembly 164 which is axially movable relative the spring 
finger mounting assembly 156. The assembly 164 includes a sleeve 166 
carrying a piston 168 extending into the chamber 162, with a spring 170 
abutting an upper face of the piston 168 and tending to move the assembly 
164 downwardly relative to the assembly 156. Fluid ports 172 extend 
through the sleeve 166 to provide fluid communication between the 
apparatus bore 174 and the chamber 162, on the opposite side of the piston 
168 from the spring 170. 
The assembly 164 also defines a cam portion 176 which, with the apparatus 
150 in a first configuration, is spaced downwardly from the finger free 
ends 160, such that the ends 160 may be deflected inwardly as the 
apparatus 150 is run into a bore hole (see FIG. 7b). 
The lower portion of the apparatus 150 is a mirror image of the upper 
portion, though the lower set of spring fingers 178 are offset by 
60.degree. to the upper fingers 158. Further, a lower body portion 180 
mounted on the lower end of the piston and cam assembly 164 defines a 
restriction 184 in the bore 174. 
For running in, the springs 170 tend to extend the apparatus 150 axially 
such that the spring finger free ends 160 are spaced from the cam portion 
176, allowing the fingers to be deflected inwardly as the apparatus 150 is 
run in and is run through borehole restrictions such as the length of 
slotted tubing 186 which is to be expanded. After passing through the 
tubing 186, fluid is pumped through the string and the apparatus bore 174, 
and the restriction 184, to create a pressure differential across the 
sleeve 166. This results in the pistons 168 being moved in the spring and 
piston chambers 162 to compress the springs 170 and to move the spring 
finger free ends 160 onto the cam portion 176 (FIG. 8). With the fingers 
in this second configuration, the apparatus 150 may be lifted through the 
tubing 186 to expand the tubing, as illustrated in FIG. 8. 
Once the tubing 186 has been extended, pressure is bled off from the bore 
174 such that the springs 170 return the fingers 158 to the first 
configuration. 
Reference is now made to FIGS. 9, 10 and 11 of the drawings, which 
illustrate details of an actuating arrangement 190 suitable for use with 
apparatus as described above. In particular, the actuating arrangement 190 
is primarily intended for use with a modified form of the apparatus 10. 
The arrangement is provided within a tubular body 192 and includes an 
annular actuating piston 194, comprising a number of parts 194a-d, linked 
to an actuating rod 196 which transfers movement of the piston to the 
trolleys (not shown) on which the cone-forming fingers are mounted. A 
valve piston 198 is mounted within the actuating piston 194 and controls 
the movement of the actuating piston 194, and thus the formation of the 
expanding cone, as will be described. The valve piston 198 comprises a 
piston reverse sleeve 200 and a pressure retention sleeve 202, the sleeves 
200, 202 being linked by a shear pin 204. The pressure retention sleeve 
202 is linked to the actuating piston part 194b by a further shear pin 
206, and a ratchet 208 is provided between the sleeve 202 and part 194c, 
the purpose of which will be described. 
Seals are provided between the piston 194 and the body 192 at two locations 
210, 211. With the valve piston 198 in a first configuration, as 
illustrated in FIG. 1, pressure from the surface (from the left hand side 
in the Figures) acts downwardly and creates a differential pressure acting 
over the area between the seals 210, 211, to move the piston 194 
downwardly to form the expanding cone. The fluid pressure is communicated 
from the body bore to the piston 194 via ports 212, 213, 214 in the piston 
reverse sleeve 200, the pressure retention sleeve 202 and the actuating 
piston part 194c, respectively. 
Once the cone has been formed, application of a first overpressure, for 
example 10.times.10.sup.6 Pa (1500 psi), shears the pin 206 and permits 
movement of the valve piston 198, relative to the actuating piston 194, to 
an intermediate position (FIG. 10) in which the port 214 is closed by the 
pressure retention sleeve 202. If the pump at the surface providing the 
actuating pressure is then shut off, the piston 194 will remain in its 
downward position, and the cone remain formed, as the sleeve 202 is held 
in the intermediate position by the ratchet 208 and traps the pressurised 
fluid behind the piston 194. The sleeve 202 thus acts as a means for 
retaining pressurized fluid and locks the cone forming parts in the second 
configuration. 
To retract the piston, and retract the cone-forming fingers to allow 
removal of the apparatus from the borehole, a further overpressure, for 
example 33.times.10.sup.6 Pa (5000 psi) is applied, which shears the pin 
204, allowing separation of the sleeves 200, 202 and opening another port 
216 in the actuating piston part 194c. This permits the high pressure bore 
fluid to act on the reverse area or underside of the piston 194 and push 
the piston upwards. The fluid trapped between the seals 210, 211 escapes 
into the borehole annulus via a 33.times.10.sup.6 Pa (5000 psi) burst disc 
218, which defines a small area port 220 to provide controlled movement of 
the piston 194. The sleeves 200, 202 and the part 194c in conjunction with 
the ports 212, 213, 214, 216 thus collectively provide a valve means 
configurable for providing fluid communication with the piston 194 for 
moving the trolleys on which the cone forming fingers are mounted in one 
direction from the first to the second configuration and further being 
configurable for providing fluid communication with the opposite side of 
the piston 194 for moving the trolleys in the opposite direction from the 
second to the first configuration. 
It will be apparent to those of skill in the art that the above-described 
embodiments are merely exemplary of the present invention, and that 
various modifications and improvements may be made thereto, without 
departing from the scope of the invention, for example the number of 
cone-forming fingers may be varied. The above embodiments are described as 
being mounted on drill pipe, though of course the apparatus may be mounted 
on any suitable supporting member or string, including coil tubing. It 
will also be clear that where terms such as "upper", "lower" and the like 
have been used, this has merely been to facilitate understanding, and the 
apparatus may of course be utilised in horizontal and inclined bore holes 
and in different orientations. Further, although the illustrated 
embodiments are described for use with slotted tubing, it will be clear 
that the apparatus of the invention may be utilised to expand other tubing 
forms and configurations, including sandscreens. Also, the actuating 
arrangement 190, although described with reference to a tubing expanding 
apparatus, may be utilised in any suitable fluid actuated downhole 
apparatus.