ROTARY STEERABLE SYSTEM FOR VERTICAL DRILLING
A rotary steerable drilling system that is operable to drill vertical wellbores and automatically maintain a vertical wellbore drilling path. The system includes a control module for operating solenoid valves that control an amount of fluid pressure applied to bias pad piston/cylinders. The control module is operable to determine when the system is deviating from vertical, in what direction the system is deviating, and where the bias pads are in relation to the direction of deviation. Based on these determinations, the control module actuates the requisite bias pads by controlling the amount of fluid pressure applied to the bias pad piston/cylinders to direct the system back to the vertical drilling path.
1. Field of the Invention
Embodiments of the invention generally relate to steerable drilling systems for drilling vertical wellbores.
2. Description of the Related Art
Directional drilling involves varying or controlling the direction of a wellbore as it is being drilled. Usually the goal of directional drilling is to reach or maintain a position within a target subterranean destination or formation with the drilling string. For instance, the drilling direction may be controlled to direct the wellbore towards a desired target destination, to control the wellbore horizontally to maintain it within a desired payzone, or to correct for unwanted or undesired deviations from a desired or predetermined path.
Thus, directional drilling may include deflection or deviation of a wellbore along a predetermined or desired path in order to reach or intersect with, or to maintain a position within, a specific subterranean formation or target. The predetermined path typically includes a depth where initial deflection or deviation occurs and a schedule of desired deviation angles and directions over the remainder of the wellbore. Thus, deflection or deviation is a change in the direction of the wellbore from the current wellbore path.
It is often necessary to adjust the direction of the wellbore frequently while directional drilling, either to accommodate a planned change in direction or to compensate for unintended or unwanted deflection or deviation of the wellbore. Unwanted deflection or deviation may result from a variety of factors, including the characteristics of the formation being drilled, the makeup of the bottomhole drilling assembly, and the manner in which the wellbore is being drilled.
Current steerable drilling systems have expensive steerable equipment and are not cost effective when drilling generally vertical wellbores that do not require the steerable capabilities. It is costly for operators to have both conventional drilling systems for drilling generally vertical wells and steerable drilling systems for drilling deviated wellbores, and switching between the two drilling systems as necessary. Most operators simply use steerable drilling systems for drilling both vertical and deviated wellbores.
There is a need, therefore, for steerable drilling systems that are cost effective and efficient for drilling vertical wellbores.
SUMMARY OF THE INVENTIONA rotary steerable drilling system for drilling vertical wellbores.
So that the manner in which the above recited features of the invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Embodiments of the invention relate to a rotary steerable drilling system for drilling wellbores. The system is operable to maintain a substantially vertical wellbore drilling path. If the system begins to deviate from the vertical drilling path (due to the wellbore formation characteristics for example), then the system is operable to automatically self correct and force the system back toward the vertical drilling path trajectory.
The system may be a self contained, electronically controlled, push bit system. The system may be rotated from the surface and/or may include conventional mud motors for providing additional rotational drill bit speed. The system may include one or more individually controllable and replaceable bias pads operable to force or push the drill bit in a desired direction. The bias pads may allow direction control of up to 5 percent over-gauge of the wellbore diameter. In the event of a failure, the system is designed to have a natural drop tendency to drill vertically.
The system 100 further includes a barrel collar, referred to herein as a control collar 40, for supporting control modules, power supplies, mud pulsers, valves, measurement/logging while drilling components, and/or various other components and electronic packages known in the art. The control collar 40 may include one or more micro-processors, memories, mass storage devices, and well known support circuits such as power supplies, clocks, cache, input/output circuits, and the like. The control collar 40 may include a control module 41, a power supply 44 (such as a battery), a pulser driver 45, and a pulser 46. The control collar 40 may be operable to communicate information to the surface and to one or more components of the system 100 as further described herein. In one embodiment, the control collar 40 is operable to transmit data to the surface via mud pulse telemetry. In one embodiment, the data may include the inclination and/or the rotational speed of the system 100.
The system 100 further includes a self-contained, steerable assembly 50 having rotating sections 51, 53 and a non-rotating section 52 disposed between the rotating sections 51, 53. The rotating section 53 may include a tubular member coupled to the drill bit 60. The rotating section 51 may include a tubular member forming a drive shaft 55 that is disposed through the non-rotating section 52 and that is coupled to the tubular member of the rotating section 53 for transmitting rotation to the drill bit 60. An internal bore 110 may be disposed through the system 100 from the drill string 10 to the drill bit 60.
The steerable assembly 50 may further include a slip ring assembly 70, a control valve assembly 80, and a pump assembly 90. The slip ring assembly 70 is operable to communicate between the control module 41 (illustrated in
If no current is applied to the coil 81, then the plunger 82 may be moved to a position that permits uninhibited fluid flow from the inlet flow passage 83 to the outlet flow passage 84, thereby minimizing the amount of pressure applied to the pistons 59 and thus applying a minimal, if any, amount of force to the bias pads 54. If a maximum amount of current is applied to the coil 81, then the plunger 82 may be moved to a position that closes or substantially restricts fluid flow from the inlet flow passage 83 to the outlet flow passage 84, thereby maximizing the amount of pressure applied to the pistons 59 and thus applying a maximum amount of force to the bias pads 54 radially outward into engagement with the surrounding wellbore. The control module 41 in the control collar 40 may control the amount of current supplied to the coil 81 of each individual solenoid valve via the slip ring assembly 70, thereby controlling the amount of piston force applied by each bias pad 54 to steer the drill bit 60 in the desired direction when drilling a wellbore. Any type of solenoid valves or other similar control valves known in the art may be used for controlling fluid flow in the steerable assembly 50.
Fluid flowing through the self contained steerable assembly 50 is driven by one or more pump assemblies 90 for each bias pad 54. The pump assembly 90 may include swash plate pump as known in the art. The pump assembly 90 may include a plate member 91 supported by a body 93 that is rotationally coupled to the drive shaft 55. The plate member 91 is arranged at an eccentric position or angle relative to the longitudinal axis of the steerable assembly 50. One or more piston/cylinders 92 positioned parallel to the longitudinal axis of the steerable assembly 50 are stroked in and out by rotation of the plate member 91 via the drive shaft 55. In this manner, the pump assembly 90 continuously pumps fluid through the self contained steerable assembly 50 during operation of the system 100. As stated above, the fluid flow driven by the pump assembly 90 is controlled by the control valve assemblies 80 to selectively actuate the bias pads 54 as desired.
Further illustrated in
To maintain the system 100 on a vertical drilling path, the control module 41 includes at least two accelerometers mounted about 180 degrees apart within the control collar 40, which are configured to identify the “highside” of the wellbore when deviated from vertical. The highside of the wellbore is the side of the wellbore circumference at a specific point along the wellbore that is closest to the surface when the wellbore deviates from vertical. When the highside of the wellbore is determined, the system 100 is forced via the bias pads 54 toward the opposite, lowside of the wellbore to push the system 100 back to the vertical drilling path. In one embodiment, the sinusoidal outputs of the accelerometers may be communicated to the control module 41, which may use the outputs to calculate and determine where the wellbore is relative to gravity.
In addition to determining where the highside of the wellbore is, the control module 41 determines where each bias pad 54 is located relative to the highside of the wellbore. To determine the position of each bias pad 54, the control module 41 receives a signal from a sensor 42 (illustrated in
Based on the determinations of the highside of the wellbore and the position of each bias pad 54, the control module 41 can determine which solenoid valves of the control valve system 80 to activate to force or push the system 100 back to vertical. The control module 41 controls the force applied to each specific bias pad 54 by controlling the actuation of the solenoid valves of the control valve assembly 80 for each bias pad 54 to direct the system 100 toward the opposite, lowside of the wellbore and back to the vertical drilling path. The control module 41 can vary the amount of force applied by each bias pad 54 by controlling the amount of current supplied to the solenoid valves of the control valve assembly 80 for each individual bias pad 54.
In operation, the drill bit 60 of the rotary steerable drilling system 100 may be rotated from the surface via the drill string 10 and/or downhole by the hydraulically actuated motor 20 to drill a vertical wellbore. Rotation is transmitted to the control collar 40, the steerable assembly 50, and the drill bit 60. The drive shaft 55 extends through the non-rotating outer housing 58 and rotates the drill bit 60. The control module 41 in the control collar 40 continuously monitors and measures the vertical trajectory of the wellbore using one or more sensors, such as accelerometers. In the event that the system 100 begins to deviate from vertical, the control module 41 determines the direction of deviation by measuring the highside of the wellbore. The one or more sensors 42 continuously monitor and measure the locations of each bias pad 54 and transmit the information to the control module 41 via the slip ring assembly 70. Based on the locations of the bias pads 54 relative to the highside of the wellbore, the control module 41 actuates one or more of the solenoid valves of the control valve assembly 80 to control the amount of fluid pressure applied to the pistons 59 of each bias pad 54.
The piston/cylinders 92 of the pump assembly 90 are continuously stroked by rotation of the drive shaft 55 to drive pressurized fluid to the pistons 59 of each bias pad 54. The amount of fluid pressure applied to each bias pad 54 is controlled by the solenoid valves of the control valve assembly 80. Depending on the amount of current supplied to the solenoid valves by the control module 41, the control valve assembly 80 either allows fluid flow, prevents fluid flow, or at least partially inhibits fluid flow through the inlet and outlet flow passages 83, 84. Inhibiting or preventing fluid flow through the inlet flow passage 83 controls and increases the amount of fluid pressure applied to the pistons 59 of each bias pad 54.
The control module 41 will control the actuation of each solenoid valve to obtain the requisite amount of bias force from each bias pad 54 to force or push the drill bit 60 back to the vertical drilling path trajectory. In this manner, the system 100 is operable to continuously monitor the vertical drilling path trajectory and the position of each bias pad 54 relative to the wellbore. The system 100 is further operable to self adjust its trajectory when deviated from vertical. The system 100 may communicate its operational characteristics (rotational speed, inclination, etc.) to the surface via hydraulic (mud pulse) telemetry or other communication mechanisms known in the art.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims
1. A drilling system, comprising:
- a control valve;
- a control module configured to actuate the control valve;
- a slip ring configured to transmit an electronic signal from the control module to the control valve, while the control module rotates relative to the control valve;
- a bias pad having a piston that is in fluid communication with the control valve, wherein actuation of the control valve controls an amount of fluid pressure applied to the piston.
2. A method of forming a wellbore, comprising:
- drilling a wellbore along a vertical trajectory using a drilling system;
- monitoring any deviation from the vertical trajectory of the wellbore;
- determining that the drilling system has deviated from the vertical trajectory;
- determining a highside of the wellbore;
- determining a position of bias pads of the drilling system; and
- actuating at least one of the bias pads to force the drilling system toward the vertical trajectory.
Type: Application
Filed: Mar 12, 2013
Publication Date: Sep 18, 2014
Inventors: Daniel Andrew Marson (Sherwood Park), Daniel Mark Sullivan (Cheltenham), John Mackinley Pagett (Birmingham)
Application Number: 13/797,875
International Classification: E21B 7/10 (20060101); E21B 17/10 (20060101);