Patent Application
20140060936
The present invention relates generally to downhole motors and, more particularly but without limitation, to methods and devices for preventing loss of broken motor parts downhole.
Mud motors are one of the most commonly used downhole tools. Typically, the mud motor is a Moineau type positive displacement type composed of an inner elongate member that rotates, namely, the rotor. The rotor is supported inside an outer tubular housing or stator equipped with a rubber liner. The upper end of the stator is connected to the drill string or coiled tubing (not shown), and the lower end of the rotor is attached to the tool or other device below that is to be driven. Rotation of the rotor is driven by fluid pumped through the drill string.
Occasionally, the stator or other parts of the motor will break as a result of excessive wear, especially in horizontal wells where the motor is subjected to more stress as it passes bends in the well bore. This breakage can result in parts of the motor being left downhole, and a fishing operation is required to recover the pieces. This is expensive and time-consuming.
The present invention provides a mud motor and rotor catch assembly that provides many advantages. A rotor bolt attached to the rotor will hold the rotor in the event of a breakage and prevent the rotor and connected tools from detaching and dropping into the well. When the rotor bolt is deployed, flow through the motor housing is substantially reduced to retard or stop rotation of the rotor. At the same time, the rotor catch assembly vents flow directly to the annulus, which will alert the operator of the rotor failure and allow continued removal of cuttings and debris from the well. These and other features of the present invention will be apparent from the following description.
Turning now to the drawings in general and to
The motor 12 may be a conventional Moineau type positive displacement type composed of an inner elongate member that rotates, namely, the rotor 16. The rotor 16 is supported inside an outer tubular stator housing 18 equipped with a rubber liner 20. Rotation of the rotor 16 is driven by fluid flow through the stator housing. The downhole end 22 of the rotor 16 is connectable to another tool or device in a known manner.
The rotor catch 14 comprises a tubular rotor bolt housing 24. The downhole end 26 of the rotor bolt housing 24 is connected to the uphole end 28 of the stator housing 18. The rotor catch 14 further comprises a rotor bolt 30. The downhole end 32 of the rotor bolt 30 is non-rotatably connected to the uphole end 34 of the rotor 16. The uphole end 38 of the rotor bolt housing 24 is connectable to the tubing string (not shown).
The rotor bolt 30 is supported for axial movement in the rotor bolt housing 24 from a neutral or running position to a deployed position, as best seen in
Disposed on the body 40 is an annular wider diameter portion 44 defining a downwardly facing shoulder 46. The downhole end 26 of the rotor bolt housing 24 comprises narrowed outlet 48 through which the lower section of the rotor bolt 30 extends. The narrowed outlet 48 defines an upwardly facing shoulder 50. The upwardly facing shoulder 50 on the rotor housing 24 and the downwardly facing shoulder 46 on the rotor bolt 30 are cooperatively configured to allow an operating fluid to flow therethrough when the rotor bolt is in the running position, shown in
The inner diameter of the narrowed outlet 48 is sized larger than the diameter or the rotor bolt body 40 so that the operating fluid can flow easily around the bolt body into the stator housing 18 to drive the rotor 16. In the event of a breakage, the rotor bolt 30 will be pulled downwardly to the deployed position in which the downwardly facing shoulder 46 on the rotor bolt 30 engages the upwardly facing shoulder 50 on the rotor housing 24, as shown in
In the most preferred practice of the invention, flow to the motor 12 is substantially reduced when the rotor bolt 30 shifts to the deployed position. To that end, as seen in
It will be appreciated that when the rotor bolt 30 shifts to the deployed position (
A valve is provided for controlling the flow through the bypass ports 60 so that flow through the ports is permitted only when the rotor bolt 30 is in the deployed position. As used herein, “valve” means any mechanism for controlling flow through the bypass ports and is limited to the preferred embodiments shown and described herein.
In the present embodiment, the valve comprises ported shear plugs 62 in the bypass ports 60 and an enlarged collar 64 at or near the uphole end 42 of the rotor bolt 30. The collar 64 and shear plugs 62 are cooperatively configured so that, when the rotor bolt 30 shifts downward into the deployed position, the collar 64 shears the shear plugs opening the ports 60, as indicated in
Turning now to
The rotor catch 114 comprises a tubular rotor bolt housing 124. The downhole end 126 of the rotor bolt housing 124 is connected to the uphole end 128 of the stator housing 118. The rotor catch 114 further comprises a rotor bolt 130. The downhole end 132 of the rotor bolt 130 is non-rotatably connected to the uphole end 134 of the rotor 116. The uphole end 138 of the rotor bolt housing 124 is connectable to the tubing string (not shown).
The rotor bolt 130 is supported for axial movement in the rotor bolt housing 124 from a neutral or running position to a deployed position, as best seen in
Disposed between the rotor bolt 130 and rotor bolt housing 124 is a sleeve 150 through which the rotor bolt is axially movable. The sleeve 150 has an inner diameter 152 larger than the outer diameter 156 of the rotor bolt body 140 so that in the running position operating fluid can flow easily through the sleeve into the stator housing 118 below.
At or near the uphole end 142 of the rotor bolt 130 is an annular head 158 defining a downwardly facing annular shoulder 160 configured to engage the upper end face 162 of the sleeve 150 when the rotor bolt shifts to the deployed position, as seen in
This embodiment is also provided with a bypass flow into the annulus. As in the previous embodiment, the sidewall of the rotor bolt housing 124 has one or more bypass ports 180. However, in this embodiment, the sleeve 150 serves as the valve for controlling flow through the ports 180. The sleeve 150 is mounted inside the rotor bolt housing 124 for axial movement between a closed position and an open position. The sleeve 150 and the bypass ports 180 are cooperatively configured so that the sleeve obstructs flow through the bypass ports when the sleeve is in the running or closed position (
The sleeve 150 is mounted in the closed position using one or more shear pins 182. Once the rotor bolt 130 shifts downward, closing off flow through the sleeve 150, as seen in
Now it will be appreciated that the present invention provides a downhole motor with a rotor catch that offers many advantages. In the typical well operation employing a motor, such as drilling with a bit, fluid pressure will increase sharply as downward pressure is exerted on the drill string. When a motor fails, as in the case of a stator breakage, for example, the operator usually will notice a loss of power, that is, advancement of the drill string will no longer cause a pressure rise. However, continued fluid flow through the drill string may cause the rotor to continue to rotate. This rotation without an intact stator may cause damage to other structures in the well.
A motor equipped with the rotor catch of the present invention will alert the operator to a motor failure by exhibit symptoms of pressure loss because the flow will be diverted to the annulus. However, because flow through the stator housing is substantially reduced, rotation of the rotor is slowed or stopped entirely, which prevents an exposed, spinning rotor from “chewing up” surrounding structures in the well. Thus, as used herein, “substantially reduced,” when used to describe the effect of the flow diversion structures of the this invention, does not require a complete blockage of flow but rather a reduction in flow that is sufficient to prevent the rotor from achieving enough torque to damage surrounding structures.
As used herein, phrases such as forwards, backwards, above, below, higher, lower, uphole and downhole are relative to the direction of advancement of the tool string in the well and are not limited to precisely vertical or horizontal directions.
The embodiments shown and described above are exemplary. Many details are often found in the art and, therefore, many such details are neither shown nor described. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present inventions have been described in the drawings and accompanying text, the description is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of the parts within the principles of the inventions to the full extent indicated by the broad meaning of the terms of the attached claims. The description and drawings of the specific embodiments herein do not point out what an infringement of this patent would be, but rather provide an example of how to use and make the invention. Likewise, the abstract is neither intended to define the invention, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. Rather, the limits of the invention and the bounds of the patent protection are measured by and defined in the following claims.
