WO2010043881A1

WO2010043881A1 - Improved downhole device

Info

Publication number: WO2010043881A1
Application number: PCT/GB2009/051227
Authority: WO
Inventors: Neil Hall
Original assignee: Wireline Engineering Limited
Priority date: 2008-10-18
Filing date: 2009-09-22
Publication date: 2010-04-22
Also published as: GB2460129B; GB2460129A; GB0819139D0

Abstract

Improved Downhole Device A downhole device for incorporation into a downhole string is described. The downhole device comprises a mandrel defining a throughbore and at least one roller for, in use, engaging the inner surface of a well bore, the at least one roller adapted to rotate around the mandrel.

Description

Improved Downhole Device Field Of The Invention

The present invention relates to a downhole device, and particularly, but not exclusively, to a downhole device adapted for use in well intervention electric wireline or slickline applications.

Background To The Invention

In conventional wireline and slickline operations, a toolstring comprising different tools is lowered into cased, or openhole boreholes from a wire or cable spooled from a drum located at the surface of the wellbore. It is often necessary to perform wireline or slickline operations during, for example, completion, perforating, maintenance and servicing, installation and retrieval of downhole apparatus, intervention and well logging. Toolstrings often comprise one or more devices that collect data from the wellbore such as temperature, pressure, water content, salinity etc of recovered fluids.

In addition to suspending the string of tools, the wire or cable spooled from a drum may also include a power cable required by the tools to carry out their functions in the wellbore, and may include multiple cables for functioning between tools or conveying data gathered by downhole sensors back to the surface.

Toolstrings operate satisfactorily in vertical and near vertical wells, but problems arise when they are used in deviated wells since contact between the outer diameter of the toolstring and the inner diameter of the wellbore casing or other tubular creates a frictional force which acts against the gravitational forces urging the toolstring downhole, and these frictional forces increase with the deviation of the well. In addition, as deviation increases, the string is more likely to snag on the casing connections or profiled surfaces on the inner wall of the casing or other tubular.

Roller Bogies incorporated into the toolstring reduce friction and surface contact to assist the movement of toolstrings within casing or other tubulars in such deviated wells. Roller Bogies can rotate with respect to the toolstring as the toolstring is moved through a deviated well.

Some conventional Roller Bogies incorporate a conduit through which the signal cables can pass from an upper part of the toolstring to a lower part of the toolstring. However, the connection between the toolstring and the rotating Roller Bogey can provide a leakage point through which the fluid in the well can enter the conduit and potentially cause problems with shorting of the power or multi cables during the operation of the downhole tools. Due to the problems of leakage, Roller Bogies have to be inspected regularly to catch problems early. As these inspections can take a significant amount of time, the number of signal cables which pass through the Roller Bogie are kept to a minimum as removal of the cables and before inspection and their reinsertion after inspection is time consuming.

Conventional Roller Bogies are made for a specific diameter of well bore, toolstring and toolstring connection. This means that a supplier has to stock a number of different configurations of bogies to fulfil all the likely requirements that may be made by their customers. Summary Of The Invention

According to a first aspect of the present invention there is provided a downhole device for incorporation into a downhole string, the device comprising: a mandrel defining a throughbore; at least one roller for, in use, engaging the inner surface of a well bore; the at least one roller adapted to rotate around the mandrel.

In one embodiment, providing a mandrel about which the at least one roller rotates permits a continuous conduit for carrying one or more signal cable to be provided through the downhole device reducing the number of connections and interfaces through which well fluid can leak into the conduit. It will be understood that signal cable is used to mean any suitable device for transmitting a signal downhole including but not limited to electric wires, fibre optics etc. Preferably, the mandrel is provided with connectors adapted to be connected at a first end to an upper portion of a toolstring and at a second end to a lower portion of the toolstring.

In one embodiment, the connectors are threaded. Alternatively or additionally, the connectors include multi-pin plug or socket type connectors.

Preferably, in use, the mandrel is fixed relative to a toolstring. Preferably, in use, the mandrel is fixed relative to an upper portion of a toolstring and a lower portion of a toolstring.

Preferably, the mandrel is unitary. A mandrel made from a single piece of material has an advantage over a multi-piece mandrel in that there are no interfaces between component parts through which leakages can occur into the mandrel throughbore.

In one embodiment, the mandrel is machined from a single piece of material. Preferably, the mandrel defines a longitudinal axis.

Most preferably, the at least one roller is adapted to rotate around the mandrel longitudinal axis.

Preferably, each roller is adapted to spin about a roller axis.

Preferably, each roller axis is perpendicular to a plane through the mandrel axis.

Preferably, the device further comprises a roller housing adapted to retain the at least one roller.

Preferably, the roller housing is adapted to rotate around the mandrel.

Preferably, the mandrel defines a portion of reduced external diameter. Preferably, the mandrel reduced diameter portion is adapted to receive the roller housing.

Preferably, the roller housing is adapted to rotate within the reduced diameter portion.

Preferably, the roller housing is adapted to rotate around the mandrel longitudinal axis.

Preferably, the roller housing wraps around the mandrel.

Preferably, the roller housing defines an egg shaped cross-section. An egg shaped cross-section facilitates rotation of the roller housing, upon engagement with a surface, to a position in which the rollers are engaged with the surface. Preferably, the roller housing is removably associated with the mandrel. Such an arrangement permits a single mandrel to be used with a number of different sizes of roller housings and rollers, increasing the utility of design and allowing a stockist to keep a reduced stock. Preferably, the roller housing comprises a first portion and a second portion.

Preferably, the first and second portions are adapted to be releasably secured to each other.

Preferably, each of the first and second portions houses at least one roller.

Preferably, the roller housing is a sleeve.

Preferably, the at least one roller is adapted to spin with respect to the roller housing.

Preferably, there are six rollers. Preferably, the mandrel throughbore is adapted to receive at least one conductor therethrough.

Preferably, the throughbore is adapted to receive multiple signal cables therethrough. Providing a mandrel with a continuous throughbore reduces, and in some cases eliminates, the need to strip down the downhole device to inspect for leaks and water damage. Reduced inspection time allows for more signal cables to be passed through the device on assembly, as it is the time consuming removal and replacement of these signal cables during inspection which is a factor in deciding how many cables to use.

In one embodiment the mandrel is adapted to receive 31 signal cables. In an alternative embodiment the mandrel is adapted to receive 22 signal cables. 31 and 22 signal cables are standard for 31 pin and 22 pin connectors which are used in the oil and gas industry.

Preferably, in use, the mandrel remains stationary with respect to at least one conductor passing therethrough.

A Brief Description of the Drawings

An embodiment of the present invention will now be described with reference to the accompanying drawings in which

Figure 1 is a perspective view of a downhole device for incorporation into a downhole string;

Figure 2 is a section view through the device of Figure 1 shown connected to a toolstring;

Figure 3 is an exploded view of the device of Figure 1 ;

Figure 4 is a section view through the mandrel of the device of Figure 1 ;

Figure 5 is a partial longitudinal section view through the roller housing of Figure 1 ; and

Figure 6 is a cross-section view through the roller housing of Figure 5.

Detailed Description of the Drawings

Reference is firstly made to Figures 1 and 2, perspective and section views of a downhole device, generally indicated by reference numeral 10, according to an embodiment of the present invention.

The device 10 comprises a mandrel 12, defining a throughbore 14 (Figure 2), six rollers 16 for engaging the inner surface of a wellbore and a roller housing 18. The rollers 16 and the roller housing 18 adapted to rotate around the mandrel 12. The mandrel 12 has a first connector 26 and a second connector 28. Referring to figure 2, the first connector 26 is threadedly connected to an upper toolstring 22 and the second connector 28 is threadedly connected to a lower toolstring 24. Signal cables 30 are run from surface through the upper toolstring 22 and passed through the mandrel throughbore 14 to the lower toolstring 24, the signal cables 30 carrying signals from the surface (not shown) to downhole tools (not shown).

As the rollers 16 and the roller housing 18 can rotate about the mandrel 12, the mandrel 12 can be fixed relative to the upper and lower toolstrings 22, providing a continuous stationary throughbore 14 through which the signal cables 30 can pass. Unlike conventional Roller Bogies, the device 10 of Figure 1 and 2 there is no path defined from the device external surface 50, between the rotating portion (roller housing 18) and the stationary portion (mandrel 12), through which fluid can leak into the wire-carrying throughbore 14. Such an arrangement can lead to improved performance and reduce the risk of a short circuiting of the downhole tools due to the presence of water which may have leaked through such a path. As there is reduced risk of short circuiting and improved performance, inspections can be reduced and their associated downtime is reduced. Reduced inspections allows a great number of signal cables 30 to be passed through the throughbore 14 because it is the removal and replacement of these signal cables 30 during inspection which leads to significant downtime. Providing a greater number of signal cables 30 provides flexibility to the operator and back-up cables 30 which are useful in the event of a cable 30 failing. Referring to Figures 3 and 4, the mandrel 12 comprises a reduced diameter portion 20. The roller housing 18 is adapted to rotate within this reduced diameter portion 20 and is prevented from axial movement along the mandrel by first and second shoulders 32, 34 defined by the mandrel 12. Referring to Figure 3, the roller housing 18 is a sleeve having a first half 36 and a second half 38. The first and second halves, 36, 38 are releasably connected together by cap screws 40. Referring briefly to Figure 6, the cap screws 40, once in place, are retained by roll pins 42. Such an arrangement permits the roller housing 18 of Figure 3 to be removed and, if required, a roller housing of a larger diameter, incorporating larger diameter rollers 16 to be used if required. This increases the utility of the mandrel 12 as a single mandrel 12 can be used with a variety of roller sizes for different applications.

Referring to Figure 5 each of the rollers 16 is adapted to spin with respect to the roller housing 18 around a roller shaft 44 which is threadedly connected to a shaft rotating head 46. Once assembled, the shaft 44 and the rotating head 46 are pinned with respect to the roller housing by roll pins 48. These parts can also be seen on Figure 3.

Referring to Figure 6, the housing 18 defines an egg shape. This shape encourages the roller housing 18, if, in use, a non-roller edge 60, 62 engages a conduit wall, to rotate to a position in which the rollers 16 engage the conduit wall (not shown).

Various modifications and improvements can be made to the above described embodiment without departing from the scope of the invention. For example, although six rollers are shown, any number of rollers but particularly four or eight could be used for this application.

Claims

1. A downhole device for incorporation into a downhole string, the device comprising: a mandrel defining a throughbore; and at least one roller for, in use, engaging the inner surface of a wellbore, the at least one roller adapted to rotate around the mandrel.

2. The downhole device of claim 1 , wherein the mandrel is provided with connectors adapted to be connected at a first end to an upper portion of a toolstring and at a second end to a lower portion of the toolstring.

3. The downhole device of either of claims 1 or 2, wherein the connectors are threaded.

4. The downhole device of any preceding claim, wherein the connectors include multi-pin plug or socket type connectors.

5. The downhole device of any preceding claim, wherein in use, the mandrel is fixed relative to a toolstring.

6. The downhole device of claim 5, wherein in use, the mandrel is fixed relative to an upper portion of a toolstring and a lower portion of a toolstring.

7. The downhole device of any preceding claim, wherein the mandrel is unitary.

8. The downhole device of any preceding claim, wherein the mandrel is machined from a single piece of material.

9. The downhole device of any preceding claim, wherein the mandrel defines a longitudinal axis.

10. The downhole device of claim 9, wherein the at least one roller is adapted to rotate around the mandrel longitudinal axis.

1 1. The downhole device of either of claims 9 or 10, wherein each roller is adapted to spin about a roller axis.

12. The downhole device of claim 1 1 , wherein each roller axis is perpendicular to a plane through the mandrel axis.

13. The downhole device of any preceding claim, wherein the device further comprises a roller housing adapted to retain the at least one roller.

14. The downhole device of claim 13, wherein the roller housing is adapted to rotate around the mandrel.

15. The downhole device of either of claims 13 or 14, wherein the mandrel defines a portion of reduced external diameter.

16. The downhole device of claim 15, wherein the mandrel reduced diameter portion is adapted to receive the roller housing.

17. The downhole device of claim 16, wherein the roller housing is adapted to rotate within the reduced diameter portion.

18. The downhole device of any of claims 13 to 17 when dependant on claim 9, wherein the roller housing is adapted to rotate around the mandrel longitudinal axis.

19. The downhole device of any of claims 13 to 18, wherein the roller housing wraps around the mandrel.

20. The downhole device of any of claims 13 to 19, wherein the roller housing defines an egg shaped cross-section.

21. The downhole device of any of claims 13 to 20, wherein the roller housing is removably associated with the mandrel.

22. The downhole device of any of claims 13 to 21 , wherein the roller housing comprises a first portion and a second portion.

23. The downhole device of claim 22, wherein the first and second portions are adapted to be releasably secured to each other.

24. The downhole device of either of claims 22 or 23, wherein each of the first and second portions houses at least one roller.

25. The downhole device of any of claims 13 to 24, wherein the roller housing is a sleeve.

26. The downhole device of any of claims 13 to 25, wherein the at least one roller is adapted to spin with respect to the roller housing.

27. The downhole device of any preceding claim, wherein there are six rollers.

28. The downhole device of any preceding claim, wherein the mandrel throughbore is adapted to receive at least one conductor therethrough.

29. The downhole device of claim 28, wherein the throughbore is adapted to receive multiple signal cables therethrough.

30. The downhole device of claim 29, wherein the mandrel is adapted to receive 31 signal cables.

31. The downhole device of claim 29, wherein the mandrel is adapted receive 22 signal cables.

32. The downhole device of any of claims 28 to 31 , wherein in use, the mandrel remains stationary with respect to at least one conductor passing therethrough.