Patent Application
20130306376
Not applicable.
Not applicable.
U.S. Pat. No. 8,074,742 issued to Scott et al. discloses a reaming tool for use during emplacement of tubular strings such as casing or liner in wellbores drilled through subsurface formations.
A rotary power section described in the above referenced patent may include a turbine section operated by flow of drilling or other fluid through an interior of the wellbore tubular being emplaced so that a reaming head can rotate without rotation of the wellbore tubular. It has been observed that fluid pressure used to operate the rotary power section may place large axial loading on bearings included in the power section to support such loading. It is desirable to have a reaming tool power section for use in emplacement of wellbore tubular that has more balanced axial loading resulting from fluid pressure.
An apparatus for cutting a wellbore according to one aspect includes the apparatus a motor having a stator and a rotor. The rotor has an output shaft connected to a cutting structure so as to drive the cutting structure. The stator and rotor are spaced radially outwardly of the axis of rotation of the rotor such that at least one of the stator and the rotor is formed with an access bore that extends through the motor to a position adjacent the cutting structure. A further object can pass therethrough, without obstruction from the stator and rotor. The further object comprises a further cutting structure of the apparatus. A flow diverter is disposed in the motor proximate a connection between the motor and the wellbore tubular, the flow diverter having a first fluid outlet in fluid communication with a power section of the motor, the flow diverter having a second fluid outlet in fluid communication with the access bore. The flow diverter is coupled to the stator such that axial loading created by fluid pressure is substantially transferred to the stator.
Other aspects and advantages will be apparent from the description and claims which follow.
Most of the details of operating a fluid powered reaming tool for use with inserting a casing or liner into a wellbore drilled through subsurface formations are set forth in U.S. Pat. No. 8,074,742 issued to Scott et al. and incorporated herein by reference. Relevant portions of the foregoing patent will be set forth below to explain operation of a pressure balanced rotary power unit for a reaming tool used with inserting casing or liner into a wellbore.
A reaming tool 5 comprises a cutting structure which, in this example, may be a reamer shoe 7 connected to an output shaft 9. Rotation of the output shaft 9 rotates the reamer shoe 7. In this example the reamer show 7 can be sacrificed by drilling or reaming after the casing 3 (or liner) is moved to its intended depth in the wellbore 1.
The output shaft 9 comprises a rotor of a motor generally indicated at 11. The rotor 11 in this example may be radially inward of a radially outward stator 13 fixedly connected to the lowermost end 4 of the casing 3.
The stator 13 may be concentric with and extends around the periphery of the output shaft 9 and may thus be of hollow tubular form when viewed from the side or in transverse cross section. The stator 13 is therefore radially spaced from the rotational axis 10 of the output shaft 9 such that it does not, when viewed in cross section from the side, extend across the output shaft 9. The output shaft 9 may be formed with an access bore 15 that extends along the length of the motor 11 from the reamer shoe 7 to the opposite, distal longitudinal end of the output shaft 9, that is, the longitudinal end adjacent the lowermost end 4 of the casing 3. The access bore 15 in this example may be co-axial with the axis of rotation 10 of the output shaft 9. The access bore 15 may also extend in a direction aligned with but not co-axial with, the axis of rotation 10.
The access bore 15 may have an internal diameter selected to receive and enable free passage therethrough of a further object and may arranged such that the further object can be located directly adjacent the reamer shoe 7. The further object could comprise any desired device which may include, for example, a sensing device to transmit a signal indicative of physical parameters relevant to the cutting process. In the example, the further object may comprise a further cutting structure comprising a drill bit 17 connected to a drill pipe, pipe string or coiled tubing, shown generally at 19.
In using the apparatus 5, the casing 3 is moved through the wellbore 1, which has already been drilled to a selected depth in the subsurface. The motor 11 may be activated to drive the output shaft 9 to rotate the reamer shoe 7 by pumping fluid through an interior of the casing 3 or liner. Rotating the reamer shoe 7 aids movement (“running”) of the casing 3 into the wellbore 1 to the selected depth.
Once the casing 3 has reached the selected depth, the motor 11 may be deactivated. The drill bit 17 and drill string 19 may then run be into the casing 3. When the drill bit 17 reaches the lowermost end 4 of the casing 3, the drill bit 17 may be moved into the access bore 15 of the output shaft 9 so as to effectively pass through the interior of the motor 11, i.e., the functional parts of the motor are radially outward of the output shaft 9 and drill bit 17 and do not obstruct passage of the drill bit 17 toward the reamer shoe 7. The motor workings do not therefore require drilling out or removal to allow the drill bit 17 access to the reamer shoe 7.
When the drill bit 17 reaches the reamer shoe 7, rotation of the drill bit 17 allows the drill bit 17 to cut through the sacrificial reamer shoe 7 so as to project beyond the reamer shoe 7 so as to move into contact with material to be drilled through to form a subsequent section of wellbore.
Referring to
Referring to
The radially inward output shaft rotor 9 may be rotatably mounted on the stator 13 using a suitable combination of rotational bearings 27. Additionally a plurality of axial thrust bearings 29 may provided to limit axial movement between the rotor 9 and the stator 13 while still allowing relative rotation of these components. The thrust bearings 29 can be arranged to allow limited axial movement if desirable.
Any desired type, number and position of bearings may be used as required to deal with the loads generated. The motor rotor 9 and stator 13 can comprise any desired structure and components to generate power to rotationally drive the rotor 9. In this example, the rotor 9 and stator 13 together comprise a turbine arrangement wherein the rotor 9 comprises turbine blades 30 arranged to deflect fluid pumped between the rotor 9 and stator 13 so as to convert some of the energy of the fluid into rotation of the rotor 9 and hence the reamer shoe 7.
The stator 13 comprises a fluid inlet 31 between the stator 13 and the internal rotor 9, at the lowermost end 4 of the casing 3, the fluid inlet 31 being radially outwardly spaced from the axis 10.
A flow diverter 32 (shown in phantom) is provided adjacent the fluid inlet 31 and serves to divert fluid pumped down the casing 3 radially outwardly so as to flow into the fluid inlet 31.
The fluid flow path is indicated by arrows ‘A’. Having been diverted by the flow diverter, the fluid enters the inlet 31 adjacent the lowermost casing end 4. The fluid is pumped in a direction generally parallel to the axis of rotation 10 of the rotor 9 in the void defined between the concentric rotor 9 and stator 13, and subsequently exits the void and the turbine arrangement radially inwardly through the outlet 33 into the access bore 15. The fluid then travels along the access bore 15 and subsequently generally radially outwardly and/or downwardly through jetting apertures (not shown) formed in the reamer shoe 7. The fluid thus functions as a lubricant for the reamer shoe 7 before being forced up the annular space 6 between the casing 3 and the wellbore 1.
Referring additionally to
The bearings, turbine arrangement and fluid flow path are otherwise similar to those described above with reference to
As explained in the Background section herein, the axial thrust bearings (e.g., 29 in
In the drilling or reaming of a wellbore with a motor which uses fluid flow as a power source there is a pressure drop through the motor. This pressure drop acts against the top most end of the rotary power output shaft in the manner of acting against a piston.
The cross sectional area of the equivalent piston is generally considered to be a function of the inside diameter of the body of the tool. This cross sectional area multiplied by the pressure drop through the motor is translated into an axial load through the motor which acts against any bearing system in the motor for carrying axial load. The pressure drop caused axial loading may be substantial.
The motor section shown in
It can be understood that as the annular motor has a relatively small cross section as contrasted with the output shaft there will be a resultant reduction in hydraulic load imparted to the axial thrust bearings while still maintaining a desired relatively high pressure without detriment to produced power and hole cleaning efficiency when the drilling fluid is ported to the wellbore annulus (6 in
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
