CA2196857C

CA2196857C - A circulating sub apparatus

Info

Publication number: CA2196857C
Application number: CA002196857A
Authority: CA
Inventors: Andrew Mcdonald
Original assignee: National Oilwell UK Ltd
Current assignee: National Oilwell UK Ltd
Priority date: 1997-02-05
Filing date: 1997-02-05
Publication date: 2007-05-08
Anticipated expiration: 2017-02-05
Also published as: CA2196857A1

Abstract

There is provided a circulating sub apparatus (50) having a tubular outer body member (51, 53, 54, 55, 56, 57) and a tubular inner body member (52, 65). The outer body member (51, 53, 54, 55, 56, 57) and the inner body member (52, 65) each have one or more holes (66, 68) substantially transverse to the longitudinal axis of the outer (51, 53, 54, 55, 56, 57) and inner (52, 65) body members. A displacement mechanism produces relative movement between the outer (51, 53, 54, 55, 56, 57) and inner (52, 65) body members such that the outer (51, 53, 54, 55, 56, 57) and inner (52, 65) body members may be repeatably moved between an aligned position, in which the one or more holes (66, 68) on the inner body member (52, 65) are aligned with the one or more holes (66, 68) on the outer body member (51, 53, 54, 55, 56, 57), and an obturated position, in which the one or more holes (66, 68) on the inner body member (52, 65) are obturated by the outer body member (51, 53, 54, 55, 56, 57).

Description

~ 196857 ~

1 "A Circulating Sub Apparatus"

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.

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.

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 "'196857 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.

8 This problem can be alleviated by using nitrogen to 9 clean the well-bore which gives increased hole cleaning capabilities.

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.

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.

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 - 3a -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 1 inner body member and out of the bottom end of the 2 inner body member.

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.

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.

17 The displacement mechanism typically includes a 18 restraining device.

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.

Typically, the piston assembly is coupled to the inner 26 body member.

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.

Typically, the restraining device comprises at least 36 one restraining member mounted on each of the inner and 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.

6 Preferably, there are two restraining members mounted 7 on each of the inner and outer body members.

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.

17 Typically, the two restraining members mounted on the 18 inner body member are mounted on the piston assembly.

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.

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 ~196857 1 to restrain the inner body member in a first position 2 from further rotation.

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.

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.

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.

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.

29 Preferably, the first position is the aligned position and the second position is the obturated position.

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 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.

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.

28 Preferably, the drill string also includes a fluid 29 operated motor, such as a positive displacement motor, and/or a reamer.

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, 1 by way of example, with reference to the accompanying 2 drawings wherein:-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.

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.

For a milling or drilling operation, drilling fluid 36 flows from a coiled tubing that is connected to an 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.

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.

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.

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.

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 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.

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.

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.

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.

Figs. 2 (a) and (b), 3 (a) and (b), 4 (a) and (b) and 5 36 (a) and (b) shows the positional relationship between ~ I 96857 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.

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 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.

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.

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 2 i 9 6 8 5 7 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.

7 Modifications and improvements can be made to the 8 embodiments, without departing from the scope of the 9 invention.

Claims

1. 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 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.

2. A circulating sub apparatus according to claim 1, wherein 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 inner body member and out of the bottom end of the inner body member.

3. A circulating sub apparatus according to claim 1 or claim 2, wherein when the outer body member and the inner body member are positioned relative to one another in the aligned position, a bypass passage is formed that allows fluid to flow from the internal bore of the circulating sub apparatus to the annulus between the outside diameter of the circulating sub apparatus and the inside diameter of the well bore, in use.

4. A circulating sub apparatus according to any of claims 1, 2 or 3, wherein the displacement mechanism is controlled by changes in fluid pressure created by varying said fluid flow rate.

5. A circulating sub apparatus according to any of claims 1, 2, 3 or 4, wherein the displacement mechanism comprises a piston assembly and a restrictor nozzle in the fluid path.

6. A circulating sub apparatus according to claim 5, wherein the displacement mechanism further comprises a restraining device.

7. A circulating sub apparatus according to claim 6, wherein the restraining device comprises at least one restraining member mounted on each of the inner and outer body members, the restraining member(s) mounted on the inner body member being selectively co-operable with the corresponding restraining member(s) mounted on the outer body member.

8. A circulating sub apparatus according to claim 7, wherein there are two restraining members mounted on each of the inner and outer body members.

9. A circulating sub apparatus according to claim 8, wherein the two restraining members mounted on the inner body member are spaced further apart than the two restraining members mounted on the outer body member.

10. A circulating sub apparatus according to claim 9, wherein one of the restraining members mounted on the inner body member and the corresponding restraining member mounted on the outer body member are adapted to rotate the inner body member with respect to the outer body member, following continued longitudinal movement of the inner body member with respect to the outer body member.