Method and apparatus for controlling downhole rotational rate of a drilling tool

Abstract

A downhole rotational rate control apparatus, adapted for coupling to the lower end of a drill string, includes a progressive cavity pump or motor, a mud flow control valve, and an electronics section. Drilling mud flowing downward through the drill string is partially diverted to flow through the pump or motor, with the mud flow rate and, in turn, the pump or motor speed being controlled by the mud flow control valve. The control valve is actuated by a control motor in response to inputs from a sensor assembly in the electronics section. By varying the rotational rate of the pump or motor relative to the rotational rate of the drill string, the tool face orientation or non-zero rotational speed of the controlled device in either direction can be varied in a controlled manner.

Claims

1. A drilling apparatus for a wellbore comprising: a housing; a progressive cavity pump or motor disposed in the housing and rotationally connectable to a controlled device, the progressive cavity pump or motor comprising a stator supported by the housing and a rotor that rotates within the stator; a flow control valve assembly to meter a flow of drilling fluid through the progressive cavity pump or motor; a control motor to directly control the flow control valve assembly; and an electronics section that rotates relative to the housing by the rotor, the electronics section controls the control motor to vary the metered flow through the progressive cavity pump or motor and thereby orientate the controlled device in the wellbore.

2. The drilling apparatus of claim 1 wherein the progressive cavity motor is coupled to the flow control valve assembly by a drive shaft.

3. The drilling apparatus of claim 1 wherein the rotor is counter-rotatable within the stator to counter-rotate the electronics section relative to the housing.

4. The drilling apparatus of claim 1 wherein the electronics section comprises a sensor to sense wellbore data.

5. The drilling apparatus of claim 4 wherein the electronics section, based on the sensed wellbore data, controls the relative rotational speeds of the housing and the electronics section to orientate the controlled device in the wellbore.

6. A drilling apparatus for a wellbore comprising: a housing; a progressive cavity pump or motor disposed in the housing and rotationally connectable to a controlled device, the progressive cavity pump or motor comprising a stator supported by the housing and a rotor that counter-rotates within the stator; a flow control valve assembly to meter a flow of drilling fluid through the progressive cavity pump or motor; a control motor to directly control the flow control valve assembly; and an electronics section that counter-rotates relative to the housing by the rotor, the electronics section controls the control motor while in the wellbore to vary the metered flow through the progressive cavity pump or motor.

7. The drilling apparatus of claim 6 wherein the electronics section comprises a sensor to sense wellbore data.

8. The drilling apparatus of claim 7 wherein the electronics section, based on the sensed wellbore data, controls the control motor to vary the metered flow through the progressive cavity pump or motor and thereby control the relative rotational speeds of the housing and the counter-rotating electronics section.

9. The drilling apparatus of claim 7 wherein the electronics section, based on the sensed wellbore data, controls the control motor to vary the metered flow through the progressive cavity pump or motor and thereby keep the sensor geo-stationary or rotating at a controlled non-zero rotational rate relative to the housing.

10. The drilling apparatus of claim 7 wherein the electronics section, based on a rotational rate of the sensor, is adapted to control the control motor to change the flow through the flow control valve assembly and the progressive cavity pump or motor to orient the controlled device in a desired direction.

11. A drilling apparatus for a wellbore comprising: a housing; a progressive cavity pump or motor disposed in the housing and rotationally connectable to a controlled device, the progressive cavity pump or motor comprising a stator supported by the housing and a rotor that is counter-rotatable within the stator; a flow control valve assembly to meter a flow of drilling fluid through the progressive cavity pump or motor; a control motor to control the flow control valve assembly; and an electronics section counter-rotatable relative to the housing by the rotor, the electronics section adapted to control the control motor while in the wellbore to vary the metered flow through the progressive cavity pump or motor; wherein the rotor is coupled to the controlled device by a drive shaft to counter-rotate the controlled device relative to the housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:

(2) FIG. 1 is a longitudinal cross-section through a bottomhole assembly incorporating a rotational rate control apparatus in accordance with a first embodiment of the present invention.

(3) FIG. 2 is a cross-sectional detail of the mud flow control valve assembly of the rotational rate control apparatus of FIG. 1, with the mud flow control valve in the closed position.

(4) FIG. 3 is a cross-sectional detail of the mud flow control valve assembly of the rotational rate control apparatus of FIG. 1, with the mud flow control valve in an open position.

(5) FIG. 4 is a longitudinal cross-section of the bottomhole assembly of FIG. 1, schematically illustrating flow paths of drilling fluid circulating through the assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The Figures illustrate a rotational rate control system 50 in accordance with an embodiment of the present invention, installed within a conventional cylindrical tool housing 10 in conjunction with a deviation assembly 100. Upper end 12 of tool housing 10 is adapted for connection to the lower end of a drill string (not shown), and is open to permit the flow of drilling mud from the drill string into tool housing 10 as conceptually indicated by arrows M in FIG. 1. Lower end 110 of deviation assembly 100 is adapted for connection to a drilling tool such as a drill bit (not shown).

(7) As illustrated in FIG. 1, rotational rate control system 50 comprises a progressive cavity (PC) motor 200 of known type, an upper drive shaft 240 disposed within a drive shaft housing 242 having a drive shaft bore 244, a mud flow control valve assembly 300, and a motor control assembly (or electronics section) 400. In the illustrated embodiment, electrical power required for rotational rate control apparatus 50 is provided by a battery pack 500 attached to the upper end of electronics section 400. The disposition of rotational rate control system 50 within tool housing 10 creates a longitudinally continuous inner annulus 20 surrounding PC motor 200, drive shaft housing 242, mud flow control valve assembly 300, electronics section 400, and battery pack 500, such that drilling mud can be pumped downward through inner annulus 20.

(8) In accordance with well-known technology, PC motor 200 has an elongate rotor 210 disposed within the central bore 201 of an elongate stator 220, with the upper end of rotor 210 being connected to upper drive shaft 240, and with the lower end of rotor 210 being connected to a lower drive shaft 230. Rotor 210 is radially eccentrically supported within stator 220, and stator 220 is radially and axially supported within tool housing 10. Rotor 210 is connected to upper end 120 of deviation assembly 100 via lower drive shaft 230, allowing deviation assembly 100 to be rotationally driven by rotor 210. In the illustrated embodiment, PC motor 200 is configured such that rotor 210 will rotate clockwise (as viewed from above) in response to a downward flow of drilling mud through central bore 201.

(9) A lower ported motor housing 250 having one or more inlet ports 251 (sized and positioned to suit specific requirements) is attached to the lower end of stator 220 and allows lower drive shaft 230 to pass through for operative engagement with deviation assembly 100. By virtue of inlet ports 251, central bore 201 of stator 220 is in fluid communication with inner annulus 20 of tool housing 10 such that a flow of drilling mud through inner annulus 20 may be partially diverted into and upward within central bore 201, thereby rotating rotor 210 counterclockwise (as viewed from above).

(10) Upper drive shaft 240 converts eccentric rotation of the rotor 210 within the PC motor 200 to concentric rotation of mud flow control valve assembly 300. Mud flow control valve assembly 300 includes a lower sleeve 310, an upper sleeve 320, at least one exit port sleeve 330 extending generally radially through the wall of tool housing 10, an inner valve housing 340, and an outer valve housing 350, with outer valve housing 350 being connected to or formed into the upper end of drive shaft housing 242. Upper sleeve 320 is sealingly attached to inner valve housing 340 while lower sleeve 310 is non-movingly secured to outer valve housing 350. Upper sleeve 320 is axially movable relative to lower sleeve 310, by means of a control motor 360 forming part of mud flow control valve assembly 300 and controlled by electronics section 400.

(11) As best understood from FIGS. 2 and 3, lower sleeve 310 and upper sleeve 320 are of complementary configuration such that upper sleeve 320 is movable between a closed position in which at least a portion of the outer surface 322 of upper sleeve 320 is in sealing perimeter contact with at least a portion of the inner surface 312 of lower sleeve 310, and an open position which creates a gap 370 between inner surface 312 of lower sleeve 310 and outer surface 322 of upper sleeve 320, in turn creating a flow passage 375 through which drilling mud flowing upward within drive shaft bore 244 passes through flow passage 375 and exits through exit port sleeve 330. The flow rate of drilling mud through flow passage 375 will be governed by the breadth of gap 370, which is in turn governed by the position of upper sleeve 320 relative to lower sleeve 310. In preferred embodiments, the position of upper sleeve 320 relative to lower sleeve 310 can be adjusted incrementally, thus varying the breadth of gap 370 and the drilling mud flow rate. Accordingly, a reference herein to the valve assembly being in an open position is not to be understood or interpreted as referring to any specific setting or as being correlative to any specific position of upper sleeve 320 relative to lower sleeve 310.

(12) In preferred embodiments, inner surface 312 of lower sleeve 310 and outer surface 322 of upper sleeve 320 are in the form of mating tapered surfaces (specifically, frustoconical surfaces in the illustrated embodiments). However, persons of ordinary skill in the art will readily appreciate that lower sleeve 310 and upper sleeve 320 could be provide in other geometric configurations (including, without limitation, non-cylindrical and non-tapered sleeves) without departing from the scope and basic functionality of the present invention.

(13) In an embodiment particularly suited for drilling directional wellbores, electronics section 400 comprises a computational electronic control assembly 420 and a sensor assembly 430 disposed within an electronics housing 410. Computational electronic control assembly 420 includes a microprocessor and associated memory, for receiving and processing data obtained by sensor assembly 430, as will be described. Sensor assembly 430 comprises one or more inclination sensors and/or one or more azimuth sensors (suitable types of which devices are known in the art). Electronics section 400, with the information gathered by sensor assembly 430, operates control motor 360 to regulate or stop the flow of drilling fluid through PC motor 200 and thence through drive shaft bore 244 and flow passage 375, as may be required to produce desired changes in rotational rate of the deviation assembly 100 to maintain or correct the path of a directional wellbore.

(14) An alternative embodiment particularly suited for drilling vertical wellbores is largely similar to the embodiment described above for drilling directional wellbores, with the exception that sensor assembly 430 may but will not necessarily comprise one or more inclination sensors and/or one or more azimuth sensors. The system otherwise functions in a substantially analogous fashion to produce desired changes in rotational rate of the deviation assembly 100 to maintain or return the wellbore path to vertical.

(15) The practical operation of the apparatus of the present invention may be readily understood with reference to the foregoing descriptions and to the Figures (particularly FIG. 4, in which arrows M indicate drilling mud flows). During well-drilling operations, drilling mud is pumped from ground surface through the drill pipe assembly and flows downhole through inner annulus 20 of tool housing 10. As the drilling mud approaches PC motor 200 (and as may be particularly well understood with reference to FIG. 4), some of the drilling mud will be diverted into central bore 201 of stator 220 through inlet ports 251 in motor housing 250 (provided that flow passage 375 within mud flow control valve assembly 300 is open to permit mud to exit central bore 201), with the non-diverted portion of the drilling mud continuing downhole through inner annulus 20 toward and into deviation assembly 100. More specifically, a pressure drop created at or below deviation assembly 100 redirects the drilling mud flow and results in approximately between 1% and 10% of the drilling mud used by the tool being diverted into and upward through central bore 201 of PC motor 200. Drilling mud circulating upward through PC motor 200 carries on upward through drive shaft bore 244, passes through flow passage 375 of mud flow control valve assembly 300, and exits through exit port sleeve 330 into the wellbore annulus 620 between the tool casing 10 and the wellbore WB being drilled.

(16) Rotor 210 of PC motor 200 is powered by the uphole-flowing drilling mud within central bore 201 that flows at a higher pressure than the drilling mud in wellbore annulus due to the pressure drops caused by the downhole restrictions such as bit nozzles, and mud flow control valve assembly 300. The effect of drilling mud flowing through PC motor 200 in an uphole direction is to create a counterclockwise rotation of rotor 210 (as viewed from above). In typical downhole motor applications, the rotation of the drill string for purposes of drilling is clockwise. Similarly, in drilling operations using apparatus in accordance with the present invention, tool housing 10 rotates with the drill string in a clockwise direction, which is opposite to the rotation of rotor 210. The counterclockwise rotation of rotor 210 is transferred to lower drive shaft 230 and deviation assembly 100, and results in a counterclockwise rotation supplied to the upper end of the deviation control device 100 relative to the drill string.

(17) Mud flow control valve assembly 300 is located uphole from PC motor 200 so that drilling mud exiting PC motor 200 enters into mud flow control valve assembly 300. Mud flow control valve assembly 300 is actuated by control motor 360, in response to control inputs from electronics section 400, to control the flow rate of drilling mud through PC motor 200 as required to rotate rotor 210 at an operationally appropriate rate.

(18) Electronics housing 410 rotates at the same speed as rotor 210 in PC motor 200 due to the connection of rotor 210 and electronics housing 410 via upper drive shaft 240 and mud flow control valve assembly 300. Because of the clockwise rotation of tool housing 10 and the counterclockwise rotatability of electronics housing 410, sensor assembly 430 can be kept close to geo-stationary so that it does not rotate at a significant speed or is kept at a non-zero controlled rotational rate relative to tool housing 10. The ability to maintain sensor assembly 430 close to geo-stationary or at a non-zero controlled rotational rate is controlled by the operation of mud flow control valve assembly 300. As tool housing 10 rotates with the rest of the drill string, upper sleeve 320 is adjusted in response to inputs from sensor assembly 430 to meter the flow of drilling mud upward through PC motor 200, thereby controlling the rotational rate of rotor 210 and electronics housing 410 with respect to tool housing 10 in order to keep sensor assembly 430 as close to geo-stationary as possible or rotating at a desired non-zero controlled rotational rate. The rotational rate of 430 is measured by sensors within electronics section 400, and the speed of rotation of electronics housing 410 is controlled with respect to tool housing 10 by controlling the rotational rate of rotor 210 until sensor assembly 430 is geo-stationary or rotating at a desired non-zero controlled rotational rate.

(19) Sensor assembly 430 may comprise an inertial grade, three-axis accelerometer of a type commonly used in “measuring while drilling” (or “MWD”) operations, and functions to determine the direction, angular orientation, and speed at which to control the deviation assembly 100. In alternative embodiments, sensor assembly 430 may comprise two or three single-axis accelerometers. Sensor assembly 430 may also comprise one or more of any one or more of the following: inertial-grade azimuth sensors, rotational-rate sensors, temperature sensors, pressure sensors, gamma radiation sensors, and other sensors which would be familiar to persons skilled in the art.

(20) Sensor assembly 430, in cooperation with other components of electronics section 400, helps to control the orientation and/or the rotational speed of deviation assembly 100 by sensing and determining the position and rotational rate, relative to the earth, of sensor assembly 430, which is coupled to deviation assembly 100. When upper sleeve 320 of flow control valve assembly 300 is in an open position, thus allowing fluid flow through PC motor 200, electronics section 400, upper sleeve 320, inner valve 340, control motor 360, and rotor 210 of PC motor 200 all rotate counterclockwise relative to tool housing 10. Sensor assembly 430 takes readings to determine the rotational rate of sensor assembly 430 with respect to the immediate wellbore axis. The rotational rate sensed by sensor assembly 430 is conveyed to control motor 360, which correspondingly adjusts the axial position of upper sleeve 320 to change the speed of PC motor 200 as appropriate (e.g., such that the drilling tool is stationary and oriented in a desired direction, or such that the tool is rotating at a desired non-zero controlled rotational rate).

(21) In one embodiment, the desired rotational rate is zero or geostationary, and accelerometers and/or magnetometers within sensor assembly 430 and electronics assembly 400 control the control motor 360 to orient sensor assembly 430 (which is coupled to deviation assembly 100) to a desired orientation with respect to the earth's gravitational field and/or the earth's magnetic field. Sensor assembly 430 periodically senses the orientation of the tool with respect to Earth to ensure that the tool is pointed in the desired direction and/or rotating at the desired rotational rate and to correct any deviations. When sensor assembly 430 senses that adjustment is needed, the rotational rate of rotor 210 of PC motor 200 is changed by moving upper sleeve 320, thus controlling the relative rotational speeds of rotor 210 of PC motor 200 and electronics housing 410 as appropriate to achieve a desired orientation of the tool. Once the tool is positioned as desired, the rotational rate of rotor 210 of PC motor 200 is controlled such that electronics section 400 and sensor assembly 430 remain geo-stationary.

(22) While preferred embodiments have been shown and described herein, modifications thereof can be made by one skilled in the art without departing from the scope and teaching of the present invention, including modifications which may use equivalent structures or materials hereafter conceived or developed. The described and illustrated embodiments are exemplary only and are not limiting. It is to be especially understood that the substitution of a variant of a claimed element or feature, without any substantial resultant change in the working of the invention, will not constitute a departure from the scope of the invention. It is to also be fully appreciated that the different teachings of the embodiments described and discussed herein may be employed separately or in any suitable combination to produce desired results.

(23) It should be noted in particular that the Figures depict a normally clockwise-rotating PC motor 200 configured within rotational rate control system 50 such that the rotational output to deviation assembly 100 is counterclockwise, with mud flow control valve assembly 300 positioned above drive shaft 240 and PC motor 200. However, persons skilled in the art will appreciate from the present teachings that the various components of rotational rate control system 50 can be readily adapted and arranged in alternative configurations to provide different operational characteristics (for example, downward mud flow through PC motor 200 to produce clockwise rotation of rotor 210) without departing from the principles and scope of the present invention.

(24) Persons skilled in the art will also appreciate that alternative embodiments of the apparatus of the invention could incorporate known types of valves, adapted as appropriate, in lieu of a dual-sleeve mud flow valve assembly of the type illustrated in the Figures. To provide specific non-limiting examples, known types of ball valve, gate valve, globe valve, plug valve, needle valve, diaphragm valve, and/or butterfly valve could be adapted for use in lieu of a dual-sleeve valve assembly, without departing from the scope of the present invention.

(25) In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following that 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 such element. Any use of any form of the terms “connect”, “engage”, “couple”, “attach”, or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described.