WO1992002707A2

WO1992002707A2 - A core sampling device with indicator for jammed core

Info

Publication number: WO1992002707A2
Application number: PCT/GB1991/001254
Authority: WO
Inventors: Per Erik Bjørn ARNØ
Original assignee: Corpro Systems Limited
Priority date: 1990-07-28
Filing date: 1991-07-25
Publication date: 1992-02-20
Also published as: AU8236091A; WO1992002707A3; GB9016624D0

Abstract

There is described core sampling apparatus including means for sensing pressure changes within the apparatus to alert when a core sample has become jammed within the device. Sample-taking adjustment means is also provided in the device.

Description

A CORE SAMPLING DEVICE WITH INDICATOR FOR JAMMED CORE

The invention relates to a sampling device and in particular, a sampling device for obtaining a core sample from a bore hole.

Conventional devices for obtaining core samples from a bore hole, such as an oil well comprise a main tubular housing which is attached at one end to a drill bit and which is attached to a drill string at its other end. Within the tubular housing is a tubular inner member which is hollow and is coaxial with the housing. During normal drilling mud is pumped through the housing and the inner member to exit through an aperture in the centre of the drill bit. When an operator wishes to obtain a core sample the hollow inner member is blocked and this diverts the mud through an annular space between the inner member and the housing so that the mud exits through apertures in the sides of the drill bit. Hence, as no fluid then flows through the inner member a core sample is formed in the inner member as the drill bit drills deeper into the geological formation.

However, one of the disadvantages of these conventional core sampling devices is that they are prone to jamming as the core sample is being obtained. This causes all the weight of the drill string to be loaded onto the core instead of the drill bit and so the drill bit does not drill any deeper. However, it may take up to an hour and a half before a drill operator notices that the core has jammed and this results in wasted drilling time.

In accordance with a first aspect of the present invention a core sampling device comprises a housing, an inner member for receiving a core sample and means to cause an increase of pressure in fluid within a drill string attached to the device in use when a core sample becomes jammed in the inner member during use.

In accordance with a second aspect of the present invention, a sampling device for obtaining a core sample from a bore hole comprises a housing, a hollow inner member for receiving the core sample, and means to mount the inner member substantially coaxially within the housing so that the inner member is axially movable relative to the housing between a first position, in which a fluid may pass between the housing and the inner member from one end of the housing to the other end, and a second position in which fluid is substantially prevented from passing between the housing and the inner member from the one end to the other end.

This aspect of the invention mitigates the problems of conventional core sampling devices by preventing fluid flow between the inner member and the housing when the core sample being obtained has jammed and has caused the inner member to move from the second position. This causes the fluid pressure to increase as fluid is prevented from passing through the device and this causes an increase in pressure in the fluid being pumped down the tool string which can be detected relatively easily by an operator.

Preferably, the fluid is prevented from flowing between the inner member and the housing by cooperating seating surfaces on the mounting means and the inner member contacting each other when the inner member is in the second position. Typically, the space between the housing and the inner member is annular.

Typically, the mounting means comprises biasing means which biases the inner member to the first position, and the weight of a drill string attached to the sampling device, in use, being supported or partially supported by the inner member is sufficient to move the inner member to the second position against the action of the biasing means.

Typically, the mounting means is fixed relative to the housing and the inner member may move relative to the mounting means. Preferably, the biasing means acts between the inner member and the mounting means.

In accordance with a third aspect of the present invention, a sampling device for obtaining a core sample from a bore hole comprises a housing, a hollow inner member and a means to mount the hollow inner member within a housing so that the hollow inner member is substantially coaxial with the housing, and wherein the mounting means is adjustable to pre-set the axial position of the inner member relative to the housing. Typically, the adjustment means adjusts the position of the mounting means relative to the housing in order to adjust the first position of the inner member within the housing.

Preferably, the adjustment means comprises a number of inserts having apertures in different positions which may be aligned with a corresponding aperture in the main housing to enable the insertion of a retaining pin through the aperture in the main housing and into the aperture in the appropriate insert in order to fix the mounting means to the housing in a predetermined position.

Typically, the fluid which is passed through the device is drilling mud.

An example of a sampling device in accordance with the invention will now be described with reference to the accompanying drawings, in which:-

Fig. 1 shows a sampling device connected to a drill bit for obtaining a core sample from a bore hole; and, Fig. 2 shows a number of different retainer shoes for use in the device shown in Fig. 1.

Fig. 1 shows a sampling device 3 which comprises an outer barrel head 1 which is attached to an upper end of an outer barrel sleeve 12 which has a number of stabilisers 14 on its external surface. At the lower end of the outer barrel sleeve 12 a drill bit 5 is attached which has central aperture 6 and a number of side apertures 4. 1 Within the outer barrel sleeve 12 is an inner barrel 13

2 having an inner chamber 43 and which is slidably

3 mounted within the outer barrel sleeve 12 by a number

4 of connectors 11 which also help to maintain an annular

5 space 8 between the outer barrel sleeve 12 and the

6 inner barrel 13. At the lower end of the inner barrel

7 13 is an upper shoe 15 which is connected to a lower

8 shoe 16. The lower shoe 16 may rotate relative to the

9 drill bit 5 by means of a lower bearing assembly 35 10 which comprises a thrust bearing an axial bearing. 11

12 At the upper end of the inner barrel 13 is an inner

13 tube head 28 which is connected to a bearing retainer

14 31 which is located within a bearing cartridge 30. The

15 bearing cartridge 30 also contains a lower disc spring

16 33 which is separated from the bearing retainer 31 by

17 an upper bearing assembly 34 which comprises a thrust

18 bearing and an axial bearing. A bearing assembly 36

19 couples the bearing retainer 31 to a ball seat 10 and a

20 flow piston 29 which are connected to each other. An 21. upper disc spring 7 biases the flow piston 29 downwards

22 and this in turn biases the bearing retainer 31, the

23 inner tube 28, the inner barrel 13, the upper shoe 15

24 and the lower shoe 16 downwards to the position shown

25 in Fig. l so that the lower shoe 16 is urged against

26 the bearing assembly 35 which separates the lower shoe

27 16 from the drill bit 5. 28

29 The flow piston 29 is retained within the bearing

30 cartridge 30 by two hex set screws 32 mounted in the

31 flow ube 2 and which cooperate with slots 37 in the

32 flow piston 29. The flow tube 2 is mounted within the

33 outer barrel head 1 by means of two retaining pins 20

34 which cooperate with an aperture 39 (See Fig. 2) in

35 retainer shows 38 which are mounted in recesses in the flow tube 2.

A number of pairs of retainer shoes 38 are provided and each pair of retainer shoes 38 has the aperture 39 which received the retaining pin 20 in an unique position. Three different retainer shoes 38A, 38B, 38C are shown Fig. 2. Typically, the separation x between the apertures of successive retainer shoes is about 1/32 inch. By selecting the appropriate pair of retainer shoes 38 the position of the flow tube 2 can be pre-set within the outer barrel head 1. For example, by choosing the pair of retainer shoes 38A position of the flow tube 2 will be relatively low and when it is in this position the position of the lower shoe 16 will be relatively how which will increase the force exerted by the lower shoe 16 on the lower bearing assembly. Alternatively, by selecting the pair of retainer shoes 38C the position of the flow tube 2 within the outer barrel head 1 will be raised which in turn will raise the position of the lower shoe 16 so decreasing the pressure exerted by the lower shoe 16 on the bearing assembly 35. The retainer shoes 38B provide an intermediate position between the positions provided by the retainer shoes 38A, 38B.

This adjustment feature enables the position of the lower shoe 16 relative to the drill bit 5 to be pre-set so that the correct amount of force is exerted by the lower shoe 16 on the bearing assembly 35. This enables the position of the lower shoe 16 and hence the upper shoe 15 and the inner barrel 13 to be pre-set so that they freely rotate within the outer barrel sleeve 12 but are not so loose that there is excessive movement of these components within the outer barrel sleeve 12. In use, the appropriate retainer shoes 38 are selected and inserted into the flow tube 2. The flow tube 2 with the attached bearing cartridge 30, the springs 33, 7, the bearing retainer 31, the bearing assemblies 36, 34, the inner tube head 28, the inner barrel 13, the upper shoe 15 and the lower shoe 16 are inserted into the outer barrel sleeve 12 and the retaining pins 20 inserted through the apertures 39 in the outer barrel head 1 and into the apertures 39 in the retainer shoes 38. The drill bit 5 with the lower bearing assembly 35 is then attached to the lower end of the outer barrel sleeve 12 so that the lower bearing assembly 35 is located between the lower shoe 16 and the drill bit 5. If the inner barrel 13, upper shoe 15 and lower shoe 16 do not rotate freely or there is excessive movement of them within the outer barrel sleeve 12 then the drill bit 5 and the flow tube 2 and the components connected to the flow tube 2 may be removed from the outer barrel head 1 and the outer barrel sleeve 12 and the retaining shoes 38 replaced with a different pair of retaining shoes 38.

Once the retaining shoes 38 which provide the correct amount of pressure between the lower shoe 16 and the lower bearing assembly 35 are in place, the outer barrel head 1 is connected to a drill string (not shown) and the drill bit 5, the sampling device 3 and the drill string are inserted into a bore hole. As the bore hole is drilled the drill bit 5, the outer barrel sleeve 12, the outer barrel head 1 and the drill string rotate and the drilling mud is pumped through the drill string into a fluid passage 40 in the outer barrel head 1. The mud then passes through a fluid passage 41 in the flow piston 29, a fluid passage 42 in the inner tube head 28, the inner chamber 43 of the inner barrel 13 and exits through the aperture 6 and the drill bit 5.

When a drill operator wishes to take a core sample from the geological formation which the drill bit 5 is drilling through a drop ball 9 is dropped into the device 3 so that it blocks the fluid passageway 41 in the flow piston 29 by abutting against the ball seat 10. When the drop ball 9 is in position on the ball seat 10 the mud pumped through the drill string can no longer pass through the central fluid passageways 42, 43 and is forced to pass into the fluid passageway 45 in the flow tube 2 which directs the mud into the annular space 8 between the outer barrel sleeve 12 and the inner barrel sleeve 13 and the inner tube head 28. The mud then passes down through the annular space 8 and exits through the apertures 4 in the drill bit. This results in a core of the geological formation being drilled through being forced into the aperture 6 in the drill bit 5 and as the drill bit 5 drills deeper into the geological formation the core gradually forms up the inner chamber 43 of the inner barrel 13.

However, in certain situations it is possible for the core to become jammed in the inner barrel 13 while it is being formed so that the core will not move further into the inner barrel 13. When this happens the weight of the drill string is supported by the core and so the weight is removed from the drill bit 5 and the drill bit 5 stops drilling through the formation. However, with the invention when the weight of drill string is transferred through the core onto the inner barrel 13 the weight of the drill string causes the outer barrel head l to exert a downwards force on the flow tube 2 which in turn acts to compress the upper disc spring 7 against the flow piston 29 so that the outer barrel head l, the flow tube tube 2 and the outer barrel sleeve 12 move downwards relative to the flow piston 29, the bearing retainer 31 the inner tube head 28 and the inner barrel 13. This causes the top end of the flow piston 29 to move upwards and abut against the surfaces 50 formed on the inside of the flow tube 2. When this occurs the fluid passageways 45 in the flow tube 2 are sealed by the flow piston 29 and so the mud is prevented from flowing through the annular space 8 in the device 3. As the central passage 41 is still blocked by the drop ball 9, this causes a build up in pressure of mud being pumped through the drill string and an operator at the surface can relatively easily detect this increase in the mud pressure and so the operator can tell that the core is jammed in the inner barrel 13.

Hence, the invention mitigates the problem of conventional core sampling devices by causing an increase in mud pressure in the drill string when a core becomes jammed to enable an operator to quickly identify the problem and to rectify the problem.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims

C AIMS

1- A core sampling device comprising a housing, an inner member for receiving a core sample and means to cause an increase of pressure in fluid within a drill string attached to the device in use when a core sample becomes jammed in the inner member during use.

2. A sampling device for obtaining a core sample from a bore hole comprising a housing, a hollow inner member for receiving the core sample, and means to mount the inner member substantially coaxially within the housing so that the inner member is axially movable relative to the housing between a first position, in which a fluid may pass between the housing and the inner member from one end of the housing to the other end, and a second position in which fluid is substantially prevented from passing between the housing and the inner member to the one end to the other end.

3. A sampling device as claimed in Claim 2 wherein the fluid is prevented from flowing between the inner member and the housing by cooperating seating surfaces on the mounting means and the inner member contacting each other when the inner member is in the second position.

4. A sampling device as claimed in either of Claims 2 or 3 wherein the space between the housing and the inner member is annular.

5. A sampling device as claimed in any one of Claims 2 to 4 wherein the mounting means comprises biasing means which biases the inner member to the first position, and the weight of a drill string attached to the sampling device, in use, being supported or partially supported by the inner member is sufficient to move the inner member to the second position against the action of the biasing means.

6. A sampling device as claimed in any one of Claims 2 to 5 above the mounting means is fixed relative to the housing and the inner member may move relative to the mounting means.

7. A sampling device as claimed in any one of Claims 2 to 6 above the biasing means acts between the inner member and the mounting means.

8. A sampling device for obtaining a core sample from a bore hole comprising a housing, a hollow inner member and a means to mount the hollow inner member within a housing so that the hollow inner member is substantially coaxial with the housing, and wherein the mounting means is adjustable to pre-set the axial position of the inner member relative to the housing.

9. A sampling device as shown in Claim 8 when the adjustment means adjusts the position of the mounting means relative to the housing in order to adjust the first position of the inner member within the housing.

10. A sampling device as claimed in either Claim 8 or 9 wherein the adjustment means comprises a number of inserts having apertures in different positions which may be aligned with a corresponding aperture in the main housing to enable the insertion of a retaining pin through the aperture in the main housing and into the aperture in the appropriate insert in order to fix the mounting means to the housing in a predetermined position.

11. A sampling device as claimed in any preceding claim the fluid which is passed through the device is drilling mud.

12. A sampling device substantially as hereinbefore described with reference to the accompanying drawings.