Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 "A Circulating Sub Apparatus"
2
3 This invention relates to a circulating sub, and more
4 particularly to a multi-opening circulating sub for use
in energy exploration, milling and drilling.
6
7 Conventional oil and gas drilling techniques utilise
8 drill-bits which are conveyed on individual lengths
9 (usually 30 feet) of drill-pipe and rotated from the
surface of the drilling rig floor to produce the
11 necessary rotary cutting action required to drill well
12 bores. Alternatively, the rotary cutting action can be
13 supplied by using a Positive Displacement Motor (PDM)
14 located above the drill-bit and connected to the
surface by either coil tubing that is provided in one
16 continuous length, or by more conventional drill-pipe.
17 The PDM produces the rotary action when drilling fluid
18 is pumped through it from the surface. The main
19 advantage of using coil tubing in conjunction with a
PDM is that of a decrease in the running-in time of the
21 equipment into the well-bore.
22
23 Debris or cuttings are produced from the cutting
24 action, which are transported to the top of the well
bore by the drilling fluid. In order to clean the well
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1 bore effectively the drilling fluid must be pumped at a
2 high enough flow rate to lift the cuttings to the
3 surface. However, only relatively low volumes of
4 drilling fluid can be pumped through the complete
Bottom Hole Assembly (BHA) without a large pressure
6 drop at the surface.
7
8 This problem can be alleviated by using nitrogen to
9 clean the well-bore which gives increased hole cleaning
capabilities.
11
12 However, the use of nitrogen gives rise to a second
13 problem, in that, nitrogen can only be pumped through a
14 PDM motor for very short periods of time without
damaging the PDM motor. Hence, the benefits of using
16 nitrogen to clean the well-bore with existing
17 technology are limited.
18
19 Traditionally, this first problem is overcome by using
an additional tool in conjunction with the motor and
21 drilling/milling assembly, known as a drop-ball
22 circulating sub. This tool is run above the motor and
23 is operated by dropping a ball, from the surface, down
24 the drill-pipe or coil tubing. The ball seats on top
of a piston within the tool and pressure is applied to
26 the upper end of the piston and ball. The pressure is
27 increased until shear pins, which are located within
28 the main body of the drop-ball circulating sub, break
29 allowing the piston to move axially downwards within
the main body thereby uncovering circulating holes in
31 the main body drilled transverse to the centre-line of
32 the drop-ball circulating sub. These holes allow an
33 increased flow rate to be pumped through the drill-pipe
34 or coil tubing, thus giving a more effective hole
cleaning capability.
36
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However, this tool has the disadvantage that once the ball
has been dropped to the circulating sub, no further milling
or drilling can take place as the fluid path to the PDM has
been blocked by the ball. If further milling or drilling is
required then the tool must be removed from the well-bore so
that the ball can be removed. Also, the length of time that
the ball takes to drop down the drill-pipe or coil tubing can
be considerable.
The second problem of pumping nitrogen is helped, but not
solved, by using a drop-ball circulating sub as the drop-ball
does not effect a complete seal on the piston allowing
nitrogen to flow through the motor.
According to a first aspect of the present invention, there
is provided a circulating sub apparatus having a throughbore
for permitting circulation of fluid from within the
throughbore out into a borehole annulus, the apparatus
comprising, a tubular outer body member and a tubular inner
body member, the outer body member and the inner body member
each having one or more holes, the holes being substantially
transverse to the longitudinal axis of the outer body member
and the inner body member, and a displacement mechanism for
producing relative movement between the outer body member and
the inner body member, such that the inner body member and
the outer body member may be repeatably moved between an
aligned position, in which the one or more holes on the inner
body member are aligned with the one or more holes on the
outer body member such that fluid contained within the
throughbore is permitted to flow from the throughbore,
through the holes and into the borehole annulus, and an
obturated position, in which the one or more holes on the
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inner body member are obturated by the outer body member such
that fluid contained within the throughbore is prevented from
flowing through the holes, and a sealing device which
obturates the throughbore below the holes when the inner and
outer body members are in the aligned position but permits
the fluid to flow from the throughbore passage onwards to
equipment located below the circulating sub when the inner
and outer body members are in the obturated position, wherein
the circulating sub apparatus is capable of permitting fluid
flow in the throughbore irrespective of the position of the
inner and outer body members relative to one another, and
wherein the displacement mechanism is operated by varying the
fluid flow rate from the surface of the borehole through the
throughbore.
Preferably, when the outer body member and the inner body
member are positioned relative to one another in the
obturated position, fluid can pass from the inner bore of the
outer body member to the inner bore of the
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1 inner body member and out of the bottom end of the
2 inner body member.
3
4 Preferably, when the outer body member and the inner
body member are positioned relative to one another in
6 the aligned position, a bypass passage is formed that
7 allows fluid to flow from the internal bore of the
8 circulating sub apparatus to the annulus between the
9 outside diameter of the tool and the inside diameter of
the well bore, in use.
11
12 Preferably, the displacement mechanism is controlled by
13 fluid pressure. Preferably, the displacement mechanism
14 comprises a piston assembly and a restrictor nozzle in
the fluid path.
16
17 The displacement mechanism typically includes a
18 restraining device.
19
Preferably the restrictor nozzle is located on the
21 uppermost portion of the inner body member such that
22 fluid passing through the inner bore of the circulating
23 sub apparatus passes through the restrictor nozzle.
24
Typically, the piston assembly is coupled to the inner
26 body member.
27
28 Typically, an increase in the fluid pressure displaces
29 the inner body member in a downwards direction.
31 Typically, there is provided a return spring, one end
32 of which butts against the outer body member and the
33 other end butts against the inner body member.
34
Typically, the restraining device comprises at least
36 one restraining member mounted on each of the inner and
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1 outer body members, the restraining member(s) mounted
2 on the inner body member being selectively co-operable
3 with the corresponding restraining member(s) mounted on
4 the outer body member.
5
6 Preferably, there are two restraining members mounted
7 on each of the inner and outer body members.
8
9 Preferably, the two restraining members mounted on one
of the body members are spaced further apart than the
11 two restraining members mounted on the other of the
12 body members. More preferably, it is the two
13 restraining members mounted on the inner body member
14 that are spaced further apart than the two restraining
members mounted on the outer body member.
16
17 Typically, the two restraining members mounted on the
18 inner body member are mounted on the piston assembly.
19
Typically, longitudinal movement of the inner body
21 member with respect to the outer body member moves one
22 of the restraining members mounted on the inner body
23 member into contact with the corresponding restraining
24 member mounted on the outer body member.
26 Preferably, one of the restraining members mounted on
27 the inner body member and the corresponding restraining
28 member mounted on the outer body member are adapted to
29 rotate the inner body member with respect to the outer
body member, following continued longitudinal movement
31 of the inner body member with respect to the outer body
32 member.
33
34 Preferably, after a predetermined longitudinal movement
of the inner body member, the restraining members in
36 contact on the inner and outer body members are adapted
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1 to restrain the inner body member in a first position
2 from further rotation.
3
4 Preferably, longitudinal movement in the opposite
direction moves the other of the restraining members
6 mounted on the inner body member into contact with the
7 corresponding restraining member mounted in the outer
8 body member.
9
Typically, the other of the restraining members mounted
11 on the inner body member and the corresponding
12 restraining member mounted on the outer body member are
13 adapted to rotate the inner body member with respect to
14 the outer body member, following continued longitudinal
movement of the inner body member in the opposite
16 direction with respect to the outer body member.
17
18 Typically, a second restrained position is reached upon
19 longitudinal movement in the opposite direction to the
direction of longitudinal movement for which the first
21 restrained position was reached.
22
23 Typically, the direction of rotation of the inner body
24 member with respect to the outer body member for which
the first restrained position is reached is the same
26 direction of rotation for which the second restrained
27 position is reached.
28
29 Preferably, the first position is the aligned position
and the second position is the obturated position.
31
32 Alternatively, the first position is the obturated
33 position and the second position is the aligned
34 position.
36 Preferably, when the circulating sub is in the aligned
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1 position, a sealing device deters the flow of fluid
2 through the bottom end of the circulating sub, and more
3 preferably deters the flow of fluid through the bottom
4 end of the inner body member.
6 Typically, when the circulating sub is in the aligned
7 position, the sealing device seals the bottom end of
8 the inner body member.
9
The invention has the advantage that nitrogen gas may
11 be pumped through the circulating sub and through the
12 circulating holes, when the circulating sub is in the
13 aligned position, to clean the well bore without
14 damaging any tools located below the circulating sub.
16 According to a second aspect of the present invention
17 there is provided a method of drilling or milling in a
18 borehole, the method comprising (a) inserting in the
19 borehole a drill string which includes a drill or mill
and a circulating sub according to the first aspect,
21 (b) altering the flow rate of fluid to move the body
22 members to the obtuated position to permit drilling or
23 milling, (c) altering the flow rate of fluid to move
24 the body members to the aligned position to permit
circulation, and (d) repeating steps (b) and (c) as
26 required.
27
28 Preferably, the drill string also includes a fluid
29 operated motor, such as a positive displacement motor,
and/or a reamer.
31
32 The fluid may be a liquid or a gas and is preferably a
33 drilling fluid. Alternatively, or in addition the
34 fluid may be nitrogen gas.
36 An embodiment of the invention will now be described,
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1 by way of example, with reference to the accompanying
2 drawings wherein:-
3
4 Fig. 1 is a split sectional view of a circulating
sub during a milling/drilling operation;
6 Figs. 2 (a) and (b) are schematic drawings of the
7 positional relationship between restraint devices
8 mounted on the circulating sub of Fig. 1;
9 Figs. 3 (a) and (b) show the restraint devices of
Figs. 2 (a) and (b) during a milling/drilling
11 operation;
12 Figs. 4 (a) and (b) show the restraint devices of
13 Figs. 2 (a) and (b) whilst initiating a
14 circulating operation;
Figs. 5 (a) and (b) show the restraint devices of
16 Figs. 2 (a) and (b) during a circulating
17 operation;
18 Fig. 6 is a detailed split sectional view of the
19 lower portion of the circulating sub of Fig. 1
during a milling/drilling operation; and
21 Fig. 7 is a detailed split sectional view of the
22 lower portion of the circulating sub of Fig. 1
23 during a circulating operation.
24
Fig. 1 shows an example of a multi-opening circulating
26 sub 50 in accordance with the present invention,
27 consisting of an outer tubular body formed by a number
28 of outer body sections 51, 53, 54, 55, 56 and 57, and
29 an inner tubular body comprising an upper piston 52 and
a lower piston 65. The upper piston 52 is coupled at
31 its lower end to the lower piston 65. The upper end of
32 the upper piston 52 is coupled to a restrictor nozzle
33 60.
34
For a milling or drilling operation, drilling fluid
36 flows from a coiled tubing that is connected to an
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1 upper outer body section 53, through the restrictor
2 nozzle 60, through a bore 70 of the circulating sub 50,
3 out of the lower outer body section 57 and subsequently
4 onwards to equipment located below the circulating sub
50, such as a PDM.
6
7 To obtain a circulating operation, the fluid flow rate
8 through the circulation sub 50 is increased. This
9 increased fluid flow rate through the restrictor nozzle
60 creates a back pressure of drilling fluid across the
11 restrictor nozzle 60, which forces the piston assembly
12 52, 65 longitudinally downwards within the outer body
13 sections 51, 53, 54, 55, 56.
14
As the piston assembly 52, 65 moves longitudinally
16 downwards, mating angles 61 mounted on the upper piston
17 52 contact an upper clutch 58 which is mounted to an
18 outer body section 54, the contact rotating the piston
19 assembly 52, 65 within the outer body sections 51, 53,
54, 55, 56.
21
22 The upper clutch 58 is formed to have two restraint
23 positions. The first restraint position allows the
24 piston assembly 52, 65 to only travel a short distance,
so that the drilling fluid continues to flow through
26 the circulating sub 50 and onto equipment located
27 below.
28
29 The second restraint position allows the piston
assembly 52, 65 to travel a greater distance, so that
31 bypass ports 66 located on the lower piston 65 move
32 into alignment with circulating holes 68 located on an
33 outer body section 56. Drilling fluid will now flow
34 down the bore 70 of the circulating sub 50 and out of
the circulating holes 68 via the bypass ports 66. A
36 pack-off sealing element 69 prevents any drilling fluid
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1 from flowing through the lowest outer body section 57
2 and on towards equipment located below. The operation
3 of the pack-off sealing element 69 will be described
4 subsequently.
5
6 Once the circulating sub 50 has been operated for the
7 required period in one of the restrained positions,
8 that is either in the drilling mode or the circulating
9 mode, to change to the other operating mode, the
10 drilling fluid flow rate is reduced. This action
11 reduces the drilling fluid back pressure across the
12 restrictor nozzle 60. A return spring 63 which acts
13 between a shoulder 72 mounted on the outer body section
14 54 and a thrust bearing 62 mounted on the upper piston
52, biasses the upper piston 52 upwards, and when the
16 drilling fluid flow rate is reduced the piston assembly
17 52 moves upward.
18
19 The thrust bearing 62 ensures that any residual torque
retained in the return spring 63 is dissipated, and
21 hence does not interfere with the rotation of the
22 piston assembly 52, 65.
23
24 As the piston assembly 52, 65 moves upward, an indexer
64 mounted on the lower piston 65 contacts a lower
26 clutch 59 which is mounted to the outer body section
27 54. The contact between the indexer 64 and the lower
28 clutch rotates the piston assembly 52, 65 in the same
29 direction as the rotation produced by the upper clutch
58 and the mating angles 61 on a downward movement.
31 Through this rotation as the piston assembly travels
32 upwards, it will have moved onto it's next restrained
33 position and hence it's next mode of operation.
34
Figs. 2 (a) and (b), 3 (a) and (b), 4 (a) and (b) and 5
36 (a) and (b) shows the positional relationship between
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1 firstly the lower clutch 59 and the indexer 64, and
2 secondly the upper clutch 58 and the mating angles 61,
3 for a complete cycle of the circulating sub 50, with
4 the components being shown laid out flat for clarity.
6 Fig. 2 (a) shows the indexer 64 and the lower clutch 59
7 in an engaged position, and Fig. 2 (a) shows the mating
8 angles 61 longitudinally displaced from the upper
9 clutch 58. Figs. 2 (a) and (b) show the piston
assembly 52, 65 in the position as shown in Fig. 1.
11
12 Fig. 3 (b) shows that the indexer 64 and the lower
13 clutch 59 have been longitudinally and rotationally
14 displaced, due to downward movement of the piston
assembly 52, 65. It can be seen in Fig. 3 (a) that the
16 mating angles 61 are in contact with the upper clutch
17 58, and are restrained in the second, or furthest
18 position possible by the upper clutch 58. This
19 position corresponds to the drilling fluid circulation
mode. It can also be seen that the piston assembly
21 rotates in only one direction due to the combination of
22 the profiles of firstly the upper clutch 58 and the
23 mating angles, and secondly the lower clutch 59 and the
24 indexer 64.
26 Figs. 4 (a) and (b) show that as the back pressure
27 across the restrictor nozzle 60 is reduced, the indexer
28 64 and the lower clutch 59 come into contact and the
29 piston assembly 52, 65 is further rotated in the same
direction as previously. The upper clutch 58 and the
31 mating angles 61 are longitudinally and rotationally
32 spaced once again, and await an increase in the
33 drilling fluid flow rate to enter a drilling fluid flow
34 through cycle.
36 Fig. 5 (b) shows that the lower clutch 59 and the
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1 indexer 64 are once again longitudinally and
2 rotationally further displaced, although the
3 longitudinal displacement is not as great as shown in
4 Fig. 3 (b). This is due to the mating angles 61 being
restrained in the first and least travel position by
6 the upper clutch 58, as shown in Fig 5 (a). This is
7 the drilling fluid flow through mode of operation of
8 the circulating sub 50.
9
As has previously been described, the circulating sub
11 50 has two modes of operation, drilling fluid flow
12 through and circulation, for when the piston assembly
13 52, 65 is restrained in a first and a second position
14 respectively.
16 The lower portion of the circulating sub 50 in the
17 first restrained position is shown in detail in Fig. 6.
18 A seal 67 prevents any leakage of drilling fluid
19 between the bypass port 66 and the circulating hole 68,
whilst the circulating sub 50 is in the first position,
21 and hence in drilling fluid flow through mode of
22 operation.
23
24 The lower portion of the circulating sub 50 in the
second restrained position is shown in detail in Fig.
26 7. The lower piston 65 has moved downwards so that
27 bypass ports 66 are now aligned with the circulating
28 holes 68, thus allowing drilling fluid to exit from the
29 bore 70 of the circulating sub 50 out through the
circulating holes 68. When the bypass ports 66 are
31 aligned with the circulating holes 68, the bottom end
32 of the lower piston 65 engages with the pack off
33 sealing element 69 such that no drilling fluid can pass
34 through an aperture 71 in a bottom plug 72 at the
bottom end of the circulating sub 50 to the equipment
36 below. Further if nitrogen gas is being circulated
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1 through the bore 70 of the circulating sub 50 and out
2 through the circulating holes 68, the seal between the
3 pack off sealing element 69 and the lower piston 65
4 ensures that no nitrogen gas can pass through any of
the tools below the circulating sub 50.
6
7 Modifications and improvements can be made to the
8 embodiments, without departing from the scope of the
9 invention.
