WO1990005237A1

WO1990005237A1 - Coring apparatus

Info

Publication number: WO1990005237A1
Application number: PCT/GB1989/001322
Authority: WO
Inventors: Per Arno
Original assignee: Corpro Systems Limited
Priority date: 1988-11-05
Filing date: 1989-11-06
Publication date: 1990-05-17
Also published as: AU4501089A; GB8825941D0

Abstract

Coring apparatus (1) for the recovery of a solid bar of rock formation being drilled comprises concentric inner and outer barrels (2, 3) arranged so that the outer barrel (3) can be rotatably driven relative to the inner barrel (2). The outer barrel (3) carries a core head (11) and bearing means are provided for the barrels (2, 3) comprising a first bearing (13A/B) supported in said core head (11) and a second bearing (14A/B) spaced from the first in a top head part (15, 18) of the apparatus, the arrangement being such that the inner barrel (2) can be located simply in the outer barrel (3) by landing the foot of the inner barrel (2) on said first bearing (13A/B). Adjustment means (14) in the top head part (15, 18) caters for axial irregularities between the barrels. The outer barrel tubing (6) has a minimum inside diameter of about 7 ins. (17.78 cm) and EI value in the range 5.94 x 109 lb. in.2 to 9.77 x 109 lb. in.2 (17.383 x 1011 to 28.59 x 10?11 Kg. mm2¿) where E is Young Modulus and I is the moment of inertia about a transverse axis of the cross-section.

Description

"CORING APPARATUS"

DESCRIPTION;

The present invention to coring apparatus for the recovery of a body or core, particularly in the form of a solid bar, of rock formation and possibly also of soil formation, especially in beds where drilling takes place in the production of oil.

Coring apparatus as above is used to give geologists information on the formation being drilled and such apparatus is known in the form of a tubular (barrel) device having an annular type bit at its lower extremity. The device comprises concentric inner and outer barrels spaced so as to define an annular space, with the outer barrel rotatable about the inner (fixed) barrel, and the outer has its lower end in the form of a core head on which is fitted the cutting bit. The cutting bit can be of natural diamond but recently the use of polycrystalline diamonds (PCD) has come into greater vogue. The inner barrel includes an upper head by means of which the inner barrel is hung in. the outer barrel, and this upper head carries a journal/thrust bearing to facilitate the rotary section of the outer barrel and the rotational independence of the two barrels. The outer barrel has a head adapted for the fitting thereto of a drill collar for the provision of rotary motion to the device, while a core catcher is provided at the lower end of the inner barrel for the retention of the solid core in the inner barrel. The annulus between the barrels serves for the supply of cooling/cleaning fluid to the core head and to the bed hole.

It is customary in the art core a 12 ins (31.12 cm) diameter hole with the device, and the well established core barrel sizing used is an outer barrel of 8 ins (20.32 cm) O/D to 6 5/8 in. (16.83 cm) 1/D with an inner barrel of 6k ins (15.88 cm) O/D to 5\ ins (13.97 cm) 1/D. A significant requirement is that the inner barrel should be hung such that a suitable clearance exists between the bottom (or bottom shoe) of the inner barrel and the core head - if this clearance is not present then inevitably the performance of the core barrel device will be unsatisfactory with the decided risk of mechanical damage. A disadvantage of the known device is that the provision of this clearance is operationally awkward and frequently there is even uncertainty concerning the existence of an adequate clearance. Adjusting means are provided for relative axial positioning of the barrels to give the desired clearance and these means can include for example shims. Checking of the clearance can involve the awkward step of raising the full corebarrel into such a position that the clearance can be visually checked and confirmed. Alternatively, and particularly where the barrel assembly is of considerable length, the adjustment can be created by raising the inner barrel by a predetermined amount (representing the desired clearance) from a position where the inner barrel rests on the corehead. However, if initially the inner barrel does not rest properly on the outer barrel or is slightly (elastically) buckled or the materials of the inner and outer barrels have different coefficients of thermal expansion then it is difficult to set and maintain the desired, clearance throughout the coring operation.

Existing coring devices have the further disadvantage that where high torque and compressive loadings are applied to the barrel assembly, as will be the case for example when the bit comprises PDC, the outer barrel is incapable of handling satisfactorily the loading. Therefore with the known coring devices the possibility arises of substantial mechanical damage due to excessive bending of the outer barrel.

Additionally, current designs of coring devices have restricted flow capacities which result in:

(a) Insufficient fluid velocity in the barrel annulus to clean and cool the cutting head (bit) .

(b) Insufficient fluid velocity to clean the annular space between the outer barrel and the hole.

In particular, mechanical coupling of the inner and outer barrels is possible due to frictional engagement of the barrels on excessive bending of the outer barrel, inadequate clearance between the barrels, or stretching of the inner barrel due to high pressure loading caused by fluid friction.

It is an object of the present invention to obviate or mitigate the above disadvantages.

According to one aspect of the present invention coring apparatus comprises concentric inner and outer barrels or tubes, and mounting means permitting rotation of the outer barrel relative to the inner barrel, said outer barrel carrying a core head, said mounting means comprising spaced bearing means.

Preferably one of said bearing means is located at the lower end of the inner barrel, while second bearing means are positioned in a supporting head part of the inner barrel.

Preferably said one bearing means is supported on the core head and defines a landing for the outer end of the inner barrel.

Preferably adjustment means are provided to cater for axial irregularities between the inner and outer barrels.

According to a second aspect of the present invention coring apparatus comprises comcentric inner and outer barrels of tubing, the barrels being mounted for rotation of the outer barrel relative to the inner, an annular space provided between the barrels defining a fluid flow passage, the outer barrel tubing having a minimum inside diameter of about 7 ins. (17.78 cm) and an El value in the range 5.94 x 10⁹ lb in². to 9.77 X 10⁹ lb. in.² (17.383 X 10¹¹ - 28.59 x 10¹¹ Kg. mm²) where E is Youngs Modulus and I is the moment of inertia about a transverse axis of the cross- section.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings which show coring apparatus in accordance with the present invention in part cross-section Fig 1A showing the top end, Fig IB the middle portion and Fig 1C the bottom or head part of the apparatus. Referring to the drawings, coring apparatus 1 for the recovery of a solid bar of rock formation being drilled comprises an inner barrel 2 and an outer barrel 3 concentric with barrel 2 such that an annular space 4 is present between the barrels 2 , 3. Each barrel 2 , 3 comprises a series of tubular sections 5, 6 respectively, the sections of each barrel being secured together by fastening means 7, 8 known in the art, whereby the length of the apparatus 1 can have wide variations. The apparatus runs in a hole shown schematically by lines 9, and to facilitate this action each tubular section 6 carries a stabilizer 10 in the form of an annular series of helical ribs.

A core head 11 (Fig 1C) is supported by the outer barrel 3 via connection 8A while a cutting bit is carried by the head 11, the head 11 having an outside diameter Dl corresponding to the size of the hole 9 and an inside diameter D2 corresponding to the diameter of the cut core bar. The annular space 4 defines a flow passage for cooling/cleaning fluid to the head 11, and the head 11 includes flow channels 12 for the passage of the fluid around the head 11 and into the hole 9.

The outer barrel 3 rotates relative to the inner barrel 2 and to this end a spaced pair of bearing means 13, 14 are provided, the lower bearing means 13 facilitating the fitment of the inner barrel 2 within the outer barrel 3 such that the aforesaid barrel clearance provision problem is avoided, as will be explained later. Each bearing means 13, 14 comprises a side-by-side ball race pair 13A/13B, 14A/14B each defining a combined journal/thrust type bearing arrangement. The outer barrel 3 includes a top head 18 (Fig 1A) adapted for the fitment thereto of a threaded connection piece 19 or joint tool whereby a drill collar (not shown) can be fitted to the apparatus for rotary driving of the barrel 3. The bearing means 14 is sandwiched between shoulders 16, 17 on an inner-barrel head 15 and the top head 18 respectively via the intermediary of a disc spring mechanism 24 which for example can be of adjusting cell type. The spring mechanism 24 caters automatically for axial irregularities between the barrels 2, 3 especially length variations between the barrels 2, 3 such as for example could occur due to differential thermal expansion between the barrels when the inner barrel 2 has a different thermal expansion from the outer barrel 3. The arrangement enables the top of neck portion 15A of the inner-barrel head 15 to be appropriately positioned relative to the tool 19. To facilitate making up the tool, two retaining pins 18A (only one shown) pass through the outer barrel head 18 and protrude into a recess 15C in the neck portion 15A so as to be capable of catching under the inner barrel head 15 whereby the inner barrel head 15 can be retained.

A shoe arrangement is provided at the bottom of the inner barrel tubulars 5 and comprises upper and lower shoes 20, 21, the lower shoe 21 carrying a core catcher 22 and having its lower end of shoulder form whereby the lower end of the barrel 2 can be landed on the bearing means 13. The core catcher 22 may be of spring ring form for example. The head 15 includes a central bore 15B to permit the flow of a fluid to the inside of the barrel 2, this bore 15B being closed at 'the appropriate time by dropping a ball 23 onto a seating on a seating ring 23A carried by the head 15, at the mouth of the bore 15B. The head 15 further includes transverse conduits 4A for fluid flow to the annular space 4.

The inner barrel 2 can be of a fairly conventional size, for example 6 1/4 in. (15.88 cm) outside diameter and 5 1/2 ins. (13.97 cm) inside diameter. However to provide a better coring performance, the outer barrel tubing 6 is arranged to have a minimum inside diameter of 7 ins. (17.78 cm) and an El in the range 5.94 x 10⁹ lb in² (17.383 x 10" Kg mm²) to 9.77 x 10⁹ lb in² (28.59 x 10" Kg mm²) where E is Youngs Modulus and I the moment of inertia about a transverse axis of the tubing cross section. This outer barrel form improves the flow regimes within the annular space 4 while providing satisfactory dynamic mechanical response. Further there is an improvement in the polar inertia giving satisfactory torsional strength to resist failure, particularly where high torque loading is applied as will be the case where a PCD cutting bit is used. By way of example the tubing 6 could have an outside diameter in the range 9 1/4 ins. (23.5 cm) to 9 3/4 (24.76 cm) while the E of the steel material used will have a value of about 30 x 10 PSI (206.85 KN/m ).

In setting up the present apparatus 1, there is no problem of maintaining a proper clearance between the inner barrel lower shoe 21 and the outer barrel 3: the inner barrel 2 is simply run into the outer barrel 3 until the shoe 21 is arrested and supported by the lower bearing means 13 - no adjustment is necessary. With the inner barrel 2 installed and retained by the pins 18A, the joint tool 19 can be connected for fitment of the drill collar.

In the core (rock bar) cutting operation, the core enters the inner barrel 2, and when the cutting operation is complete the core must be retrieved from the barrel 2. This is simply achieved by backing out the tool joint, releasing holding pins 18A, then lifting out the inner barrel 2, or alternatively each section 5 of the barrel 2 can be lifted out with the core held in place. The latter operation is done by repeating a clamping, unscrewing and lifting procedure at each section connection 7.

The above coring apparatus 1 according to the present invention gives the following benefits:

Improved stiffness, similar to that of 8 ins. (20.32 cm) drill collars.

Improved torsional resistance in connections, eliminating equipment damage charges.

Increased tensile strength. There is also less risk of equipment loss.

Fewer connections in the core barrel assembly.

Improved internal flow areas; This would permit higher flow rates improving cleaning and cooling of the corehead without damage to the inner tube or outer tube, OR lower pressure drop inside the corebarrel at the same flow rate.

Better bearing capacity; This would reduce the incidence of bearing failure, resultant jamming and loss of core.

Positive inner barrel centralisation.

Reduced inner to outer torsional coupling, this will reduce the tendency to jam and also allow improved results for oriented coring.

Increase in the annular flow rate promoting better cleaning of the area around the corebarrel reducing the likelihood of the barrel becoming stuck.

Easier wellsite core recovery due to the reduction in connections to extract the inner tube and subsequent improvement in the amount of rig time needed to recover core.

Speeding up of the equipment servicing time because of the elimination of barrel spacing adjustment.

The net of these features will be to reduce costs and improve coring performance by enhancing recovery due to less jamming and by improving cutting performance by promoting uni-axial loading of the cutting head.

Whereas the above coring apparatus 1 is described for the recovery of rock cores, the apparatus would be suitable for recovering cores found in other types of geological formations.

Modifications are of course possible. For example, other means for permitting relative displacements between parts of the device can be provided at suitable locations in the apparatus if so desired.

Claims

%CLAIMS

1. Coring apparatus comprising concentric inner and outer barrels or tubes (2, 3) and mounting means (13, 14) permitting rotation of the outer barrel (3) relative^" to the inner barrel (2) , said outer barrel (3) carrying a core head (11) , characterised in that said mounting means comprises spaced bearing means (13A/B, 14A/B) .

2. Coring apparatus as claimed in claim 1, characterised in that one of said bearing means (13 /B) is located at the lower end of the inner barrel (2) , while the second bearing means (14A/B) is positioned at a supporting head part (15) of the inner barrel (2) .

3. Coring apparatus as claimed in claim 2, characterised in that said one bearing means (13A, 13B) is supported on the core head (11) and define a landing for the outer end of the inner barrel (2) .

4. Coring apparatus as claimed in any one of the preceding claims characterised in that at least one of the bearing means (13 /B, 14A/B) defines a combined journal/thrust bearing arrangement.

5. Coring apparatus as claimed in claim 3, characterised in that the outer end of the inner barrel (2) is of stepped/shoulder form to facilitate landing on said one bearing means (13A/B) .

6. Coring apparatus as claimed in claim 2, characterised in that said second bearing means (14A/14B) is located between shoulder formations (16, 17) on inner head part (15) and on the outer barrel (3) respectively.

7. Coring apparatus as claimed in any one of the preceding claim, characterised in that adjustment means (24) are provided to cater for axial irregularities between the inner and outer barrels (2, 3) .

8. Coring apparatus as claimed in claim 7, characterised in that said adjustment means (24) comprise a spring mechanism located in a head part (15, 18) of the apparatus.

9. Coring apparatus as claimed in any one of preceding claims, characterised that means (18A) are provided to retain a head part (15) of the inner barrel (2) relative to a head part (18) of the outer barrel (3) to facilitate tool make-up.

10. Coring apparatus comprising concentric inner and outer and outer barrels (2, 3) of tubing (5, 6), the barrels (2,

3) being mounted for rotation of the outer barrel (3) relative to the inner barrel (2) an annular space (4) provided between the barrels defining a fluid flow passage

(4) characterised in that the outer barrel tubing (6) has a minimum inside diameter of about 7 ins. (17.78 cm) and an El value in the range 5.94 x 10⁹ lb. in.² to 9.77 x 10⁹ lb. in.² (17.383 x 10¹¹ to 28.59 x 19¹¹ Kg. mm² where E is

Youngs Modulus and I is the moment of inertia about a transverse axis of the cross-section.