WO2015117247A1

WO2015117247A1 - Expandable and drillable landing seat

Info

Publication number: WO2015117247A1
Application number: PCT/CA2015/050093
Authority: WO
Inventors: Geir Lunde; Jarle TRONES
Original assignee: Trican Completion Solutions Ltd
Priority date: 2014-02-10
Filing date: 2015-02-10
Publication date: 2015-08-13
Also published as: NO20140164A1; NO340685B1

Abstract

An expandable ball seat (100) comprises a main part (110) made of a first material, and comprising an inner cylindrical surface (111) and a plurality of seat members (120) configured to form a landing seat (121) for a drop ball in an initial position and are radially movable to a final position in which the drop ball can pass between them. Each seat member (120) comprises a drillable part made of a second material that is less hard and less tensile than the first material. Only the drillable part is allowed to extend radially further inward than the cylindrical surface (111) in the final position.

Description

EXPANDABLE AND DRILLABLE LANDING SEAT

BACKGROUND

Field of the invention

[0001] The present invention relates generally to the field of wells extending into subterranean formations, and in particular to an expandable and drillable landing seat for such wells.

Prior and related art

[0002] In the following description, wells relating to the oil and gas industry are used as an example. However, the invention may be used in any well, for example a well for geothermal applications. The well is terminated in a well head, which may be located on dry land or on a seafloor.

[0003] In order to make a well, a large diameter borehole is first drilled some distance into the ground. Then, a steel casing is inserted into the borehole and cemented to the formation. When the cement has set, a smaller diameter borehole is drilled further into the ground, and a new casing is inserted and cemented in place. The procedure is repeated until the well has the desired depth, and may include drilling one or more horizontal branches extending laterally into the formation.

[0004] Completion of the well includes installing plugs to separate different zones, e.g. different layers of a reservoir containing hydrocarbons, a production string to convey oil or gas to the surface and valves to open or close for a flow from the formation to the production string. Valves are also used for cementing and stimulation, for example hydraulic fracturing or inserting surfactants.

[0005] Equipment in the well, e.g. valves or plugs, can be activated by a drop ball. As known in the art, a drop ball is an obstruction member configured to land on a preinstalled seat in the well. The drop ball is dropped or conveyed by a flow within a tubular and lands on the preinstalled seat. Thereby, a pressure can be applied behind the ball, and the resulting force can be used to activate a device.

[0006] A set of drop balls of different sizes can be provided to activate different devices, wherein each device is provided with a smaller diameter seat then the previous device closer to the surface. The sizes of the drop balls in such a set must be sufficiently different so that a ball does not inadvertently land on a seat with slightly smaller diameter than intended due to, for example, grit or scaling. The need for significantly different sizes limits the practical number of drop balls in such a set, for example to about 10 drop balls of different sizes.

[0007] In some applications, it is desirable to activate a number of devices that is substan- tially greater than the available number of drop balls in a set of the kind described above. For these applications, expandable ball sets have been developed. An expandable ball seat receives a drop ball and activates its corresponding device in the manner described above. Once the device is activated, the ball seat, i.e. the landing seat, flares outward to let the ball or obstructing member proceed downstream to the next expandable ball seat.

[0008] A typical example of such an expandable ball comprises a seat made up of seat elements on the distal ends of collet fingers and is connected to a ball activated device, such as a sliding sleeve valve. When the device is inactive, outer surfaces on the collet fingers typically engage an inner surface so that they are prevented from flaring radially outwards. The activation causes an axial displacement away from the supporting inner surface that moves the distal ends to a region with larger diameter. Thus, once the device is activated, the collet fingers flare outwards into the region with larger diameter such that the drop ball can pass.

[0009] More detailed examples of expandable ball seats are found in US 2009/0308588 Al assigned to Halliburton Energy Services, US 20110198100 Al assigned to i-Tec AS and US 2011/0278017 Al assigned to Packers Plus Energy Services, Inc.

[0010] Bulges in the outer surface of a tubular are likely to cause trouble when the tubular is inserted into a borehole, a casing or a liner. Thus, the tubular wherein the drop ball passes to activate a series of expandable ball seat s preferably has an outer surface with substantially one diameter along its entire length. An even outer surface and a limited wall thickness of the tubular typically implies that part of the seats protrude into the tubular when a series of , expandable ball seat s have expanded. The protruding seats may cause problems later, such as preventing free passage of tools and/or coiled tubing.

[0011] The main objective of the present invention is to provide an expandable ball seat that enables an even inner surface of a tubular wall after expanding radially outwards into the tubular wall.

SUMMARY OF THE INVENTION

[0012] The objective is attained by an expandable ball seat according to claim 1. [0013] More particularly, the invention concerns an expandable ball seat comprising a main part made of a first material and comprising an inner cylindrical surface and a plurality of seat members. The seat members are configured to form a landing seat for a drop ball in an initial position and are radially movable to a final position in which the drop ball can pass between them. Each seat member comprise a drillable part made of a second material that is less hard and less tensile than the first material. Only the drillable part is allowed to extend radially further inward than the cylindrical surface in the final position.

[0014] As the second material is relatively soft and has a relatively low ability to merely deform during drilling, the second material is easier to drill away than the other parts of the expandable ball seat, which are made of a harder and more ductile first material. Thus, the drillable parts can be drilled away in a separate operation after activation of the devices controlled by the expandable ball seats, whereby the tubular is left with an inner surface without protrusions. The less hard and tensile drillable parts reduce wear on the drill bit.

[0015] In a preferred embodiment, the second material is also less hard and less tensile than the material of a tubular into which the expandable ball seat is incorporated. Thereby, the drill bit can be made of material that is harder than the drillable parts, and less hard than the tubular and main part to reduce the risk for damage to the inner, permanent surfaces caused by drilling.

[0016] In some embodiments, the main part comprises a plurality of collet fingers and each collet finger has a distal end to which a seat member is affixed. However, other embodiments with seat members slidably attached to radial guides are anticipated.

[0017] In some embodiments, the entire seat member is made of the second material. This feature simplifies manufacture of the seat members.

[0018] In some embodiments, the seat member is disposed axially between the main part and a clamping device. These embodiments comprise embodiments with collet fingers as well as embodiments with slidably attached seat members.

[0019] In embodiments with collet fingers and clamping devices, each collet finger is preferably clamped radially between the seat member and the clamping device.

[0020] In a preferred embodiment, the second material is cast iron. There are numerous qualities that are sufficiently hard and ductile to withstand the forces applied during activation, and yet easier to drill than the steel qualities used for tubulars and the main part of the expandable ball seat.

[0021] Other features and benefits appear in the dependent claims and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be explained in greater detail by way of an exemplary embodiment and with reference to the accompanying drawings, in which: Fig. 1 is a schematic longitudinal section through a preferred embodiment taken along plane I-I on Figs. 2 and 4,

Fig. 2 is a schematic cross-section through a preferred embodiment taken along plane II-II on Fig. 1 ; Fig. 1 is a schematic, longitudinal section through a preferred embodiment taken along plane I-I on Figs. 1 and 3; and

Fig. 3 is a side view of the embodiment in the previous figures.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0023] The drawings are schematic, and not necessarily to scale. Numerous details known to one skilled in the art are omitted for clarity.

[0024] Fig 1 is a schematic longitudinal section through a preferred embodiment of an expandable ball seat 100 taken along plane I-I on Figs. 2 and 4. In use, the expandable ball seat forms part of an activation mechanism coupled into a tubular in order to activate a ball activated device by a drop ball as briefly discussed in the introduction. In the drawings, the expandable ball seat 100 is shown in an initial state wherein the associated ball activated device is still inactive and the expandable ball seat provide a landing seat for the drop ball. However, it is understood that the expandable ball seat has an expanded final state in which the associated ball activated device is activated and the drop ball is allowed to pass through the expandable ball seat 100.

[0025] The expandable ball seat comprises a main part 110 with an inner cylindrical surface 111. Several collet fingers 115 extend axially from the main part 110.

[0026] The collet fingers 115 are disposed adjacent to each other and form a substantially cylindrical and fluid tight wall. A small leakage of the pressurized fluid between the collet fingers is acceptable as long as it does not prevent building up the pressure required to shift the ball seat 100 axially and activate the associated ball activated device. In the initial state shown in the figures, at least part of the collet fingers 115 would be supported radially by a surface disposed around the expandable ball seat such that the collet fingers 115 cannot flare radially outwards. An axial shift to a region with a larger inner diameter should cause the collet fingers 115 to expand radially and stay expanded. Thus, in the final state, the collet fingers 115 should preferably deform into the region with larger region without breaking and without returning elastically to the position shown in the drawings.

[0027] The distal ends 116 of the collet fingers are the ends pointing away from the main part 110, i.e. the lowermost ends in Fig. 1. In the embodiment on Fig. 1, a distal end comprises a seat member 120 clamped to a finger extending from the main body 110 by a clamping device 130.

[0028] The seat members 120 extend radially inward and collectively form a landing seat 121 having a smaller diameter than the inner diameter of the tubular and the inner surface 111 of the main part.

[0029] Each seat member 120 is clamped axially to the finger by an associated clamping device 130. In addition, the finger of the main part 110 is clamped radially between the seat member 120 and the clamping device 130 by means of a screw 140 extending from the clamping device 130 through the finger into the seat member 120.

[0030] As the seat member 120 is axially clamped between the finger and the clamping device 130, only part of the seat 120 extent into the interior of the expandable ball seat 100. Strictly, only part of the seat member 120 needs to be drillable to achieve the desired effect. However, the part being clamped is small compared to the drillable part, so it is obviously practical to manufacture the entire seat member 120 as one piece, i.e. from one drillable material.

[0031] While an embodiment with collet fingers are shown in the drawings, alternative embodiments with seat members slidably mounted on radially extending guides are anticipated. Adapting the principles of the present invention to such an embodiment is considered obvious to the skilled person.

[0032] Fig. 2 is a cross-section through the distal end of the embodiment in Fig. 1, showing 8 sectional collet fingers viewed along the rotational axis of the main part 110 and tubular.

The expandable ball seat may comprise less than or more than 8 segments.

[0033] Fig. 3 is a side view of the embodiment described above. The internal surface 111, seat members 120 and landing seat 121 do not appear in Fig. 3. Otherwise, the reference numerals are as described above.

[0034] The invention is described by way of example, and numerous alternatives will be obvious to one skilled in the art. Thus, the invention is defined by the subject matter set forth in the attached claims.

Claims

An expandable ball seat (100) comprising a main part (1 10) made of a first material and comprising an inner cylindrical surface (111) and a plurality of seat members (120), wherein the seat members (120) are configured to form a landing seat (121) for a drop ball in an initial position and are radially movable to a final position in which the drop ball can pass between them, characterized in that each seat member (120) comprise a drillable part made of a second material that is less hard and less tensile than the first material, and wherein only the drillable part is allowed to extend radially further inward than the cylindrical surface (1 11) in the final position.

The expandable ball seat according to claim 1, wherein the second material is less hard and less tensile than the material of a tubular into which the expandable ball seat (100) is incorporated.

The expandable ball seat according to claim 1 or 2, wherein the main part (110) comprises a plurality of collet fingers and each collet finger (115) has a distal end (116) to which a seat member (120) is affixed.

The expandable ball seat according to any preceding claim, wherein the entire seat member (120) is made of the less hard and less tensile material.

The expandable ball seat according to claim 4, wherein the seat member (120) is disposed axially between the main part (1 10) and a clamping device (130).

The expandable ball seat according to claim 3 and 5, wherein the collet finger (1 15) is clamped radially between the seat member (120) and the clamping device (130).

The expandable ball seat according to any preceding claim, wherein the second material is cast iron