METHOD AND SYSTEM FOR SURPLUS EXPANSION OF A BELL SECTION AT A LOWER END OF AN EXPANDED TUBULAR

Abstract

A method for expanding a lower bell section of an expandable tubular to a larger diameter than upper parts thereof utilizes an expandable bell cone (1) with circumferentially spaced segments (2) that expand in response to axial force and automatically retract in response to removal of the axial force, wherein gaps (A) are present between the expanded segments (2) and the tailends (2A) at the gauge of the segments are slightly skewed to mitigate the effect of the gaps (A) on the flattening of the expanded bell sections between the segments (2).

Description

BACKGROUND OF THE INVENTION

The invention relates to a method and system for surplus expansion of a bell section at a lower end of an expanded tubular.

Such a bell section may serve as a host casing in which an upper end of an additional expandable casing or liner section is positioned and expanded to generate a MOnoDiameter (MOD) wellbore casing or lining system.

It is known to expand a bell section at a lower end of an expandable well tubular to a larger diameter than upper parts of the expandable tubular by:

• • expanding the tubular with a primary expansion cone to a predetermined expanded width; and
  • expanding the bell section of the tubular to a larger width than the predetermined expanded width using an expandable bell cone.

Disadvantages of the known expandable segmented bell cone are that it is a complex device that may be easily locked in an expanded position in which the bell cone cannot be retrieved to the earth surface and that it creates flattened parts of the expanded bell sections between the expanded segments of the cone that do not have 360° circumferential coverage.

Other expandable cones that are subject to the risk of remaining locked in an expanded position are disclosed in US patent applications US2005/194129 and US2008/223568.

There is a need for a less complex expandable segmented bell cone that can be easily retracted after use and that does not create flattened parts of the expanded bell sections between the segments of the cone that do not have 360° circumferential coverage.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a method for expanding a bell section at a lower end of an expandable tubular to a larger diameter than upper parts of the expandable tubular comprising:

• • expanding the tubular with a primary expansion cone to a predetermined expanded width; and
  • expanding the bell section of the tubular to a larger width than the predetermined expanded width using a bell cone with segments circumferentially spaced around on a conical surface such that the segments expand in response to axial pressure and automatically retract in response to removal of the axial pressure,
  • wherein gaps are present between the expanded segments and the tail-ends at the gauge of the segments are slightly skewed to mitigate the effect of the gaps on the flattening of the expanded bell sections between the segments; and
  • the segments of the bell cone are circumferentially spaced in a V-shaped groove between a pair of adjacent conical surfaces having top angles and friction coefficients to allow the segments to retract in the absence of axial pressure directed towards the gauge of the segments.

In accordance with the invention there is furthermore provided a system for expanding a bell section at a lower end of an expandable tubular to a larger diameter than upper parts of the expandable tubular comprises:

• • a primary expansion cone for expanding the tubular to a predetermined expanded width; and
  • a segmented bell cone for expanding the bell section of the tubular to a larger width than the predetermined expanded width using a bell cone with segments circumferentially spaced around on a conical surface such that the segments expand in response to axial pressure and automatically retract in response to removal of the axial force,
  • wherein gaps are present between the expanded segments and the tail-ends at the gauge of the segments are slightly skewed to mitigate the effect of the gaps on the flattening of the expanded bell sections between the segments; and
  • the segments of the bell cone are circumferentially spaced in a V-shaped groove between a pair of adjacent conical surfaces having top angles and friction coefficients to allow the segments to retract in the absence of axial pressure directed towards the gauge of the segments.

These and other features, embodiments and advantages of the method and system according to the invention are described in the accompanying claims, abstract and the following detailed description of non-limiting embodiments depicted in the accompanying drawings, in which description reference numerals are used which refer to corresponding reference numerals that are depicted in the drawings.

Similar reference numerals in different figures denote the same or similar objects. Objects and other features depicted in the figures and/or described in this specification, abstract and/or claims may be combined in different ways by a person skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a longitudinal sectional view of a segmented bell expansion cone according to the invention taken along section A-A shown in FIG. 1B;

FIG. 1B is a side view of the segmented bell expansion cone shown in FIG. 1A;

FIG. 2A is a isometric view of an alternative embodiment of the cone in an expanded mode;

FIG. 2B is a longitudinal sectional view of the cone of FIG. 2A in a collapsed configuration; and

FIG. 2C is a longitudinal sectional view of the cone of FIG. 2A in an expanded configuration.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS

An objective of the segmented expandable bell cone 1 according to the invention is to expand the bottom part of an expandable liner to a diameter which is slightly larger than that of the upper part of the liner to provide a bell in which the next expanded liner can be cladded.

The bell cone 1 shown in FIGS. 1A and 1B is an expandable cone 1 which is run below the main solid or optionally segmented cone (not shown) in the expansion tool string 2. In collapsed mode (not shown) the largest outer width of the bell cone 1 is slightly smaller than that of the main cone (not shown). When expanded the bell cone 1 shown in FIGS. 1A and 1B does not provide a full 360° coverage in circumferential direction. The bell cone 1 typically expands the liner already expanded by the main cone by about two times the wall thickness of the expanded liner. Once the bell section has been completed the bell cone is collapsed and the remainder of the liner is expanded with the main cone.

The bell cone 1 may be part of Top Anchor and Pull (TAaP) or a Jack and Pull(JaP) Mono Diameter (MOD) well system wherein adjacent liner sections are expanded to substantially the same diameter and wherein an upper end of the lower liner is radially expanded within a lower end of a previously installed expanded liner of which the lower end is expanded to larger width than other parts of the expanded liner to form the large diameter bell section.

The bell cone 1 comprises a number of circumferentially spaced segments 2 which can slide over a tapered sleeve 3. The tapered sleeve 3 is locked to the mandrel 4 of the tool string sub 2 by a collet arrangement 13. The segmented bell cone 1 is hydraulically activated by pushing the segments 2 over the tapered sleeve 3 with a hydraulic cylinder assembly 20 to the expanded size of the bell cone illustrated in FIGS. 1A and 1B. At this position the segments 2 are locked. When the expansion of the large diameter bell section is completed the collet arrangement 13 is released from the tool string sub 2 by hydraulic pressure exerted in a piston an cylinder assembly 20, which pulls the sleeve around the collet down so that the collet segments can snap out of the grooves in the tool string sub and then sleeves 3 and 4 can also move down by applying axial expansion force to the bell cone segments. This causes the segments 2 to move back to the collapsed diameter again. When the expansion tool string 2 is subsequently mechanically pulled or hydraulically pushed up again the expansion of the liner is then completed with the main cone (not shown).

The sections of the expanded liner not supported by the segments 2 tend to flatten slightly.

However a minimum number of segments 2 ensures that the size of the gap A between adjacent pairs of segments 2 relative to the wall thickness of the liner can be controlled such that this flattening does not jeopardize the performance of the de MOD overlap seal.

The gap A between two adjacent segments 2 in expanded configuration of the cone may be expressed as:

A=(π.(D_bc−D_mc))/N≤a.t

wherein

• • A=gap between two segments for expanded cone shape
  • D_bc=diameter bell cone
  • D_mc=diameter main cone
  • N=number of segments
  • A=maximum allowable ratio between gap and pipe wall thickness
  • T=wall thickness of liner

With substitution of D_bc=D_mc+2.t in the above equation the minimum value for N is expressed as:

N(2.π)/a

Experiments revealed that a value for a of about 0.75 (i.e.: 8 segments) provides a sufficiently smooth ID of the bell for the MOD overlap seal sub to perform a liquid tight seal.

When the tail-ends 2A at the gauge of the segments 2 are slightly skewed the effect of the gaps A on the flattening of the expanded liner sections between the segments can be further mitigated.

The segmented bell cone 1 shown in FIGS. 1A and 1B is substantially simpler than an expandable 360° coverage cone.

Furthermore the top angle of the conical surface 2 and friction factor between said surface 2 and the segments 2 are configured such that the segmented bell cone 1 is self-releasing when expansion force is applied again after a pressure pulse has released the collet. Set down weight is not required.

It will be understood that the expansion ratio of the self-releasing segmented bell cone 1 is limited, which is not a problem for minor surplus expansion of the bell section between overlapping ends of a pair of nested expandable well tubulars in a MOD well section.

FIGS. 2A-2C show an alternative configuration wherein the bell cone comprises segments 22 that are squeezed between a pair of tapered shoulders 20,34 in a manner substantially similar as the compliant cone known from U.S. Pat. No. 7,681,636.

The objective of the segmented bell cone 20 shown in FIGS. 2A-2C is to provide a bell expansion feature that allows the expanded liner or bell shoe to be set closer to the bottom of the open hole. The bell expansion feature of the bell cone 20 is self-releasing.

The compliant cone shown in FIGS. 2A-2C is based on the compliant cone disclosed in U.S. Pat. No. 7,681,636. This known compliant cone enables a well liner to be expanded to a minimum diameter with a solid cone. The compliant expansion feature is provided by a set of segments, which are radially pushed outwards by the axial frictional force exerted between the solid cone 18 and the expanding liner. In case of an external restriction the compliant segments collapse to allow the expansion tool to pass this restriction. Once the restriction is passed, the segments are pushed out to their maximum diameter again.

The taper 30 of the cone and the taper 34 of the sleeve 6 can be to form taper angles that generate a self-releasing V-shaped groove such that the radially pointing outward force on the segments 10 resulting from the expansion force on the solid cone section 18 is larger than the radially pointing inward force on the segments 10 required to expand the liner from a solid cone width (ID) to an increased surplus bell width (ID+). In this case the segments 10 will stay in their expanded configuration during the expansion of the bell section.

When at the start of the expansion of the liner an expansion force is applied to the solid cone section 18 via the mandrel 22 of the tool, the segments 10 expand to their maximum diameter as shown in FIG. 2C. The surplus bell diameter is created by pulling the expanded bell cone through the bell section of the liner.

When the bell section is completed the axial movement of the solid unsegmented cone 18 over the mandrel 22 is locked in the collapsed position of the segments 10. Then the segments 10 are no longer activated during the expansion of the upper part of the liner.

The compliant cone modified into a bell cone provide a simple and compact expansion tool for expanding the bell section with an expansion cone having segments with less than 360° coverage.

When the tail-ends 10A at the gauge of the segments 10 are slightly skewed as illustrated in FIG. 2A the effect of the gaps A between the expanded segments 10 on the flattening of the expanded liner sections between the segments can be adequately mitigated.

It will be understood that the segmented bell expansion cone according to the invention shown in FIGS. 1 and 2 requires minimal length below the bottom of the liner which enables the liner shoe to be set close to the bottom of the hole.

Therefore, the method, system and/or any products according to present invention are well adapted to attain the ends and advantages mentioned as well as those that are inherent therein.

The particular embodiments disclosed above are illustrative only, as the present invention may be modified, combined and/or practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein.

Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below.

It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined and/or modified and all such variations are considered within the scope of the present invention as defined in the accompanying claims.

While any methods, systems and/or products embodying the invention are described in terms of “comprising,” “containing,” or “including” various described features and/or steps, they can also “consist essentially of” or “consist of” the various described features and steps.

All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values.

Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.

Moreover, the indefinite articles “a” or “an”, as used in the claims, are defined herein to mean one or more than one of the element that it introduces.

If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be cited herein by reference, the definitions that are consistent with this specification should be adopted.

Claims

1. A method for expanding a bell section at a lower end of an expandable tubular to a larger diameter than upper parts of the expandable tubular, the method comprising: expanding the tubular with a primary expansion cone to a predetermined expanded width; andexpanding the bell section of the tubular to a larger width than the predetermined expanded width using a bell cone with segments circumferentially spaced around on a conical surface such that the segments expand in response to axial force and automatically retract in response to removal of the axial force,

2. A system for expanding a bell section at a lower end of an expandable tubular to a larger diameter than upper parts of the expandable tubular comprises: a primary expansion cone for expanding the tubular to a predetermined expanded width; anda segmented bell cone for expanding the bell section of the tubular to a larger width than the predetermined expanded width using a bell cone with segments circumferentially spaced around on a conical surface such that the segments expand in response to axial pressure and automatically retract in response to removal of the axial pressure,