CA2715867A1

CA2715867A1 - Method and apparatus for earth drilling at an angle

Info

Publication number: CA2715867A1
Application number: CA2715867A
Authority: CA
Inventors: David Kutinsky
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-09-28
Filing date: 2010-09-28
Publication date: 2012-03-28

Abstract

A method and apparatus for earth drilling at an angle includes a tubular outer housing and a tubular inner mandrel. The outer housing has a concentric longitudinal axis and an interior surface defining an interior bore. The interior bore has an offset axis that is offset from the concentric longitudinal axis. The inner mandrel is positioned within the interior bore and has an exterior surface. Bearings positioned between the interior surface of the outer housing and the exterior surface of the inner mandrel support the inner mandrel for concentric rotation about the offset axis of the interior bore. In accordance with the method, a drill bit is coupled to the apparatus resulting in the drill bit drilling at an angle to the drill string defined by the offset axis.

Description

TITLE
[0001] Method and apparatus for earth drilling at an angle FIELD

[0002] There is described a method and associated apparatus for earth drilling at an angle with particular application for drilling horizontal well bores for hydrocarbon producing wells.
BACKGROUND

[0003] A typical drilling motor assembly used in earth drilling has a power section that uses a moineau motor with a rotor and stator. In operation, drilling fluid is pumped down a drill string to the power section and, as the drilling fluid passes the rotor, the rotor rotates in an eccentric manner. A universal joint coupling is used to translate the eccentric output from the moineau motor into a concentric output that is used to rotate a drill bit.

[0004] In order to drill at an angle, an apparatus referred to as a "bent sub"
is placed above the power section. The bent sub has an angular offset, which creates a drilling angle for the drilling motor assembly. This angular offset may be as little as a fraction of a degree to as much as three or even four degrees. In order to drill a straight hole, the bent sub is removed.

[0005] There will hereinafter be described an alternative method and apparatus for creating that offset angle that provides advantages over what is presently being used, as will hereinafter be further described.

SUMMARY

[0006] According to one aspect there is provided an apparatus for earth drilling at an angle which includes a tubular outer housing and a tubular inner mandrel. The outer housing has a concentric longitudinal axis and an interior surface defining an interior bore. The interior bore has an offset axis that is offset from the concentric longitudinal axis. The inner mandrel is positioned within the interior bore and has an exterior surface.
Bearings positioned between the interior surface of the outer housing and the exterior surface of the inner mandrel support the inner mandrel for concentric rotation about the offset axis of the interior bore.

[0007] According to another aspect there is provided a method for earth drilling at an angle. The method involves coupling a drill bit to a coupling apparatus having a housing with a concentric longitudinal axis that is co-axial with a drill string and a concentrically rotating output that rotates about an offset axis that is offset from the concentric longitudinal axis of the housing. With this type of coupling, the drill bit drills at an angle to the drill string defined by the offset axis.

[0008] The above described method and apparatus places the "bend" right at the drill bit, rather than above the power section. This positioning allows for the drilling motor to potentially drill a hole that deviates from vertical to horizontal within a shorter radius.

[0009] The above described method and apparatus allows for more flexibility when drilling. If a relatively small angular offset is used, such as three quarters of one degree, the drill string will deviate when left in one rotational position and will drill straight when rotated.

[0010] When being used with a power section having a moineau motor it is preferred that a universal joint coupling be provided within the outer housing to convert eccentric rotation of the moineau motor power section into concentric rotation of the inner mandrel.
It must be remembered that there are other types of power sections that can be used, such as turbines. A
turbine has a concentric output and does not need a universal joint coupling to convert eccentric rotation to concentric rotation. However, a turbine power section may need a speed reduction gear assembly to slow down the output of the turbine to a rotational output better suited for the drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

[0012] FIG. 1 is a side elevation view, in section, of an apparatus for earth drilling at an angle.

[0013] FIG. 2 is a detailed side elevation view, in section, of the tubular outer housing from the apparatus illustrated in FIG. 1.

[0014] FIG. 3 is a simplified side elevation view, in section, of the apparatus of FIG. 1 attached as part of a drill string which includes a drill bit and a moineau motor power section.
DETAILED DESCRIPTION

[0015] A apparatus for earth drilling generally identified by reference numeral 10, will now be described with reference to FIG. 1 through FIG. 3.
Structure and Relationship of Parts:

[0016] Referring to FIG. 1, apparatus 10 includes a tubular outer housing 12 and a tubular inner mandrel 14. For ease of assembly outer housing 12 is shown as having several components 12a, 12b, and 12c that are connected by pin and box threaded connections 16a and 16b. Referring to FIG. 2, outer housing 12 has a concentric longitudinal axis shown by broken line 18. Outer housing 12 also has an interior surface 20 defining an interior bore 22.
Interior bore 22 has an offset axis shown by broken line 24 that is offset from concentric longitudinal axis 18. Referring to FIG. 1, inner mandrel 14 is positioned within interior bore 22 and has an exterior surface 26. For ease of assembly, inner mandrel 14 is shown as having several components 14a and 14b that are connected by pin and box threaded connections 28a and 28b. Radial Bearings 30 and thrust bearings 32 are positioned between interior surface 20 of outer housing 12 and exterior surface 26 of inner mandrel 14. Both radial bearings 30 and thrust bearings 32 support inner mandrel 14 for concentric rotation about offset axis 24 of interior bore 22. Radial bearings 30 are primarily intended to bear radial loads. Radial bearings 30 are illustrated as being a bushings. Thrust bearings 32 are primarily intended to bear axial loads. Two types of thrust bearings are provided 32a and 32b.
Thrust bearing 32a bears an axial load when weight is being placed on drill bit 200, as shown in FIG. 3, and thrust bearing 32b bears off-bottom load when drill bit 200 is lifted off bottom and suspended by drill string 300. Belville springs 34 are used to place a preload upon thrust bearings 32.

[0017] Referring to FIG. 1, this particular embodiment of apparatus 10 was constructed for use with a power section having a moineau motor 400, as illustrated in FIG. 3. For that reason, a universal joint coupling, generally indicated by reference numeral 100, was included within outer housing 12 to convert eccentric rotation of the moineau motor power section into concentric rotation of the inner mandrel 14. It will be appreciated that if apparatus 10 had been constructed for use with a power section having a turbine, universal joint coupling 100 would not be necessary. It will also be appreciate, that apparatus 10 could be coupled to an existing coupling apparatus that already has incorporated within it a universal joint coupling.
An eccentric rotor adaptor 102 is provided through which eccentric rotational input is received from the moineau motor power section 400, as shown in FIG. 3, into universal joint coupling 100. A concentric rotor adaptor 104 is provided through which concentric rotational output is transmitted from universal joint coupling 100 to mandrel 14. The illustrated universal joint coupling 100 is of conventional construction including a shaft 106 with bulbous ends 108 and 110. Bulbous end 108 is received in a socket 112 positioned within eccentric rotor adaptor 102. Bulbous end 110 is received in a socket 114 positioned within concentric rotor adaptor 104. Drive balls 116 are positioned in bulbous ends 108 and 110.
Drive balls 116 are received in pockets 118 in sockets 112 and 114. Rotational force is transmitted from eccentric rotor adaptor 102 to shaft 106 by the engagement between drive balls 116 and pockets 118 in socket 112. Similarly, rotational force is transmitted from shaft 106 to concentric rotor adaptor 104 by the engagement between drive balls 116 and pockets 118 in socket 114. Omni-directional movement required to translate eccentric input into a concentric output is accommodated by movement of bulbous end 108 within socket 112 and bulbous end 110 within socket 114. Sealing boots 120 are clamped in position to create lubrication chambers 122 to hold lubrications to facilitate movement of bulbous ends 108 and 110 within sockets 112 and 114, respectively. Lubrication is pumped into lubrication chambers 122 through grease passages 124.

Operation:

[0018] The use and operation of apparatus 10 will now be described. Referring to FIG 3, apparatus 10 is incorporated as part of a drill string 300 with moineau power section 400 attached to housing 12 and drill bit 200 attached to mandrel 14. When attached to moineau power section 400, concentric longitudinal axis 18 of outer housing 12 is co-axial with drill string 300. Drilling fluid is pumped down drill string 300 and serves to cause eccentric rotation of moineau motor power section 400. Referring to FIG. 1, this eccentric rotational input is input into universal joint coupling 100 through eccentric rotor adaptor 102. A
concentric output is then output from universal joint coupling 100 into mandrel 14 though 5 concentric rotor adaptor 104. Mandrel 14 rotates with a concentric rotation.
Referring to FIG. 2, this concentric rotation is about offset axis 24 that is offset from concentric longitudinal axis 18 of outer housing 12. Referring to FIG. 3, this rotational input from apparatus 10 results in drill bit 200 drilling at an angle to drill string 300, as defined by offset axis 24.
Advantages:

[0019] The above described method and apparatus places the "bend" right at the drill bit, rather than above the power section. If the offset axis 24 is offset by three degrees, this positioning allows for the moineau motor power section 400 to drill a hole that deviates from vertical to horizontal within a shorter radius.

[0020] The above described method and apparatus also allows for more flexibility when drilling. If a relatively small angular offset is used, such as three quarters of one degree, the drill string will deviate when left in one rotational position and will drill straight when rotated.
This allows for steering of the drill bit using measuring while drilling tools. It also avoid having to trip out of the hole when shifting to straight drilling as one now does with bent housings.

[0021] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0022] The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.

Claims

1. An apparatus for earth drilling at an angle, comprising:
a tubular outer housing having an interior surface defining an interior bore, the outer housing having a concentric longitudinal axis and the interior bore having an offset axis that is offset from the concentric longitudinal axis;
a tubular inner mandrel having an exterior surface, the inner mandrel being positioned within the interior bore;
bearings positioned between the interior surface of the outer housing and the exterior surface of the inner mandrel, the bearings supporting the inner mandrel for concentric rotation about the offset axis of the interior bore.

2. The apparatus of Claim 1, wherein a universal joint coupling is provided within the outer housing to convert eccentric rotation of a moineau motor power section into concentric rotation of the inner mandrel.

3. A method for earth drilling at an angle, comprising:
coupling a drill bit to a coupling apparatus having a housing with a concentric longitudinal axis that is co-axial with a drill string and a concentrically rotating output that rotates about an offset axis that is offset from the concentric longitudinal axis of the housing, such that the drill bit drills at an angle to the drill string defined by the offset axis.