Patent Application
20090032302
The invention relates generally to a method of determining the direction a tool face points; more particularly, to determining the orientation and/or angular displacement of a tiltable joint of a bottom hole assembly.
Steerable systems for use drilling boreholes in a formation, for example, for subsequent use in the extraction of oil or gas, are well known. One steerable system is a rotary steerable drilling system, which can include substantially continuous rotation of the drill string. Rotary steerable systems can be classified as “point-the-bit” systems, “push-the-bit” systems, or even a hybrid system, such as described in U.S. Pat. No. 7,188,685 entitled Hybrid Rotary Steerable System. Examples of point-the-bit type rotary steerable systems and how they operate are described in U.S. Patent Application Publication Nos. 2002/0011359; 2001/0052428 and U.S. Pat. Nos. 6,394,193; 6,364,034; 6,244,361; 6,158,529; 6,092,610; and 5,113,953, all herein incorporated by reference. Examples of push-the-bit type rotary steerable systems and how they operate are described in U.S. Pat. Nos. 5,265,682, 5,553,678; 5,803,185; 6,089,332; 5,695,015; 5,685,379; 5,706,905; 5,553,679; 5,673,763; 5,520,255; 5,603,385; 5,582,259; 5,778,992; 5,971,085 all herein incorporated by reference.
Regardless of the type of steerable system, a bottom hole assembly of a drilling system can include a tiltable joint. This joint can be used, for example, to aim a tool face in a desired direction which can control the direction in which the borehole propagates. The movement of the joint relative to the bottom hole assembly, e.g., the direction in which the tiltable joint points, is primarily controlled by the force applied by steering actuators, which can be drilling fluid powered. These forces can be referenced with respect to a formation fixed frame work, instead of with respect to the rotating bottom hole assembly, and so the direction in which the actuators apply force to point the tiltable joint can be inertially referenced.
Unknown forces, for example, bottom hole dynamics, bending, frictional contact of the bottom hole assembly with the formation, drill bit reaction forces, joint friction, weight on bit, etc., act to perturb the direction in which the tiltable joint, e.g., the tool face, points. It can be desirable to determine the direction a tool face points, or more particularly, to determine the orientation and/or angular displacement of a tiltable joint of a bottom hole assembly.
The orientation and/or angular displacement of the tiltable joint with respect to the bottom hole assembly can be directly measured by a resolver or angular potentiometer on the tiltable joint and/or gap-sensors measuring relative motions in two non-collinear planes (inductive, capacity, etc.) between tiltable joint and bottom hole assembly. However inclusion of such devices can be impossible or undesirable, e.g., tight tolerances.
In one embodiment, a method of determining an orientation of a tiltable joint connected to a bottom hole assembly can include providing a plurality of radially disposed actuators driven by a fluid to tilt the tiltable joint, correlating a known orientation of the tiltable joint with respect to the bottom hole assembly with a set of known exhaust pressures of the plurality of radially disposed actuators, measuring an exhaust pressure of the fluid from at least one of the plurality of radially disposed actuators to produce a set of exhaust pressures, and comparing the set of exhaust pressures and the correlated set of known exhaust pressures to determine the orientation of the tiltable joint with respect to the bottom hole assembly. The method can include providing an inclination and azimuth of the bottom hole assembly with respect to a formation, and resolving an inclination and azimuth of the tiltable joint with respect to the formation via the orientation of the tiltable joint with respect to the bottom hole assembly and the inclination and azimuth of the bottom hole assembly with respect to the formation.
The method can include supplying the fluid from a bore of the bottom hole assembly. The fluid can be a drilling fluid. The method can include measuring at least one of a fluid supply pressure and a fluid return pressure locally to the plurality of radially disposed actuators, and removing any pressure loss associated with the at least one of the fluid supply pressure and the fluid return pressure from the exhaust pressure to produce the set of exhaust pressures. The set of known exhaust pressures can be a set of known peak exhaust pressures.
In another embodiment, a method of determining an angular displacement of a tiltable joint connected to a bottom hole assembly can include providing a plurality of radially disposed actuators driven by a fluid to tilt the tiltable joint, correlating a known angular displacement of the tiltable joint with respect to the bottom hole assembly with a set of known exhaust pressures of the plurality of radially disposed actuators, measuring an exhaust pressure of the fluid from at least one of the plurality of radially disposed actuators to produce a set of exhaust pressures, and comparing the set of exhaust pressures and the correlated set of known exhaust pressures to determine the angular displacement of the tiltable joint with respect to the bottom hole assembly.
The method can include providing an inclination and azimuth of the bottom hole assembly with respect to a formation, and resolving an inclination and azimuth of the tiltable joint with respect to the formation via the angular displacement of the tiltable joint with respect to the bottom hole assembly and the inclination and azimuth of the bottom hole assembly with respect to the formation. The method can include supplying the fluid from a bore of the bottom hole assembly. The fluid can be a drilling fluid. The method can include measuring at least one of a fluid supply pressure and a fluid return pressure locally to the plurality of radially disposed actuators, and removing any pressure loss associated with the at least one of the fluid supply pressure and the fluid return pressure from the exhaust pressure to produce the set of exhaust pressures. The set of known exhaust pressures can be a set of known peak exhaust pressures.
In yet another embodiment, a method of determining an angular displacement of a tiltable joint connected to a bottom hole assembly can include providing a plurality of radially disposed actuators driven by a fluid to tilt the tiltable joint, measuring an exhaust pressure of the fluid from at least one of the plurality of radially disposed actuators to produce a set of exhaust pressures, deriving a set of exhaust flow rates from the set of exhaust pressures, calculating a state of actuation data set for the plurality of radially disposed actuators from the set of exhaust flow rates, and determining the angular displacement of the tiltable joint with respect to the bottom hole assembly from the state of actuation data set of the plurality of radially disposed actuators.
The step of calculating the state of actuation data set can include integrating the set of exhaust flow rates over a time interval. The step of calculating the state of actuation data set can include integrating the set of exhaust flow rates over a time interval to create a set of volumetric data, correlating a known volume of discharged fluid with a known actuator displacement, and generating the state of actuation data set via the set of volumetric data and the known volume of discharged fluid correlated with the known actuator displacement. The method can include calculating a rate of angular displacement change from the angular displacement.
The method can include providing an inclination and azimuth of the bottom hole assembly with respect to a formation, and resolving an inclination and azimuth of the tiltable joint with respect to the formation via the angular displacement of the tiltable joint with respect to the bottom hole assembly and the inclination and azimuth of the bottom hole assembly with respect to the formation. The method can include supplying the fluid from a bore of the bottom hole assembly, wherein the fluid is a drilling fluid. The method can include measuring at least one of a fluid supply pressure and a fluid return pressure locally to the plurality of radially disposed actuators, and removing any pressure loss associated with the at least one of the fluid supply pressure and the fluid return pressure from the exhaust pressure to produce the set of exhaust pressures. The set of known exhaust pressures can be a set of known peak exhaust pressures.
The invention relates generally to a method of determining the direction a tool face points; or more particularly, of determining the orientation and/or angular displacement of a tiltable joint of a bottom hole assembly. As used herein, the term orientation refers to the position in relation to a specific place or object, for example, the direction an object is skewed with respect to a place or another object. The term angular displacement refers to the position in relation to a specific place or object (i.e., orientation) and the magnitude of skew therebetween, for example, the numerical degree an object is skewed with respect to another object.
Tiltable joint 6 of bottom hole assembly 4 shown in
Tiltable joint 6 of bottom hole assembly 4 in this embodiment in
Force to tilt the tiltable joint 6 with respect to the bottom hole assembly 4 can be provided by one or more actuators (34,36), as are known in the art. An actuator (34,36) can be motively driven by a fluid, for example, drilling fluid 16. A hydraulic actuator can include a dump valve actuator, for example, the bi-stable actuator and drilling system including same as described in U.S. patent application Ser. No. 11/609,996 incorporated by reference herein. An actuator (34,36) can include a cylinder and piston driven by a motive fluid.
In the view of the embodiment in
Ascertaining the orientation and/or angular displacement of the tool face 28 with respect to the bottom hole assembly 4 and/or formation 14 can be desired. For example, it may be desired to actively maintain tool face 28 in a geostationary orientation. In the embodiment in
In a rotary steerable system 2, the drill string 8 can be constantly rotated, and thus steering the creation of the borehole 12 in the formation 14 can create a need to reference the orientation and/or angular displacement of the tool face 28 or other device attached to the tiltable joint 6 with respect to a formation 14 fixed framework, as opposed to with a bottom hole assembly 4 fixed framework. In the illustrated embodiment, a formation fixed framework can allow the direction in which the sleeve 38 is pushed, and therefore points, to be inertially referenced. Orientation can be referenced relative to the bottom hole assembly 4, for example, with respect to a fixed point on the bottom hole assembly 4. The distal end of the bottom hole assembly 4 can define a coordinate system with 0-360 degrees representing the orientation of skew with respect to a fixed point of the bottom hole assembly 4. Angular displacement can include the orientation (e.g., radial displacement) as well as the magnitude of axial skew in that orientation, for example, the axial skew between the tiltable joint 6 axis 26 and the central axis 30 of bottom hole assembly 4 shown in
Rotary steerable drilling can include selective activation of appropriate actuator(s) during rotation of the bottom hole assembly 4 to achieve a desired movement of bit 24 with respect to the formation 14, e.g., to form a curve or dog leg in borehole 12 or reach a desired location in the formation 14. A sensor method to determine orientation and/or angular displacement of a tiltable joint 6, with respect to a bottom hole assembly 4 that said tiltable joint 6 is attached to and/or with respect to a formation 14, is disclosed herein.
An actuator (34,36) can include, but is not limited to, a fluid pressure system, a bellows, or a cylinder having a moveable piston to provide the force to tilt the tiltable joint 6. An actuator can include any means for converting hydraulic force into mechanical movement. A fluid, e.g., drilling fluid, can provide the force to drive the fluid pressure system of the actuator, e.g., bellows, piston, etc., said driving force tilting the tiltable joint 6.
In the embodiment in
Dump valve 42 in the embodiment in
Dump valve 42 can switch the mechanical actuator means (e.g., piston, bellows, etc.) between a high pressure fluid source (e.g., in the “drive” state) and to a low pressure sink (e.g., in the “dump” state). Dump valve 42 can be used in a closed loop system, or an open loop system, for example, using the drilling fluid 16 as the motive fluid to drive the actuator. In the dump state, fluid can be forced to move out of the piston, bellows, etc. of the actuator (34,36) according to the movement (e.g., retraction) of the piston, bellows, etc.
Actuators (34,36) can be selectively activated to steer the tool in a desired direction, typically referenced relative to the formation 14. In the current embodiment, as the direction 26 of tool face 28 generally determines the direction of borehole 12 propagation, it can be desirable to determine the direction 26 of tool face 28, or other device attached via a tiltable joint 6. For example, a monitoring or control system governing the activation of the actuators (34,36) can utilize the direction 26 of tool face 28 relative to the bottom hole assembly 4 and/or formation 14.
Specifically, determining the orientation and/or angular displacement can be desired. For example, the orientation of the tiltable joint 6 with respect to the bottom hole assembly 4 can be determined. Additionally or alternatively, the angular displacement, which includes the orientation and the magnitude of skew, can be determined. For example, the angular displacement of the tiltable joint 6 with respect to the bottom hole assembly 4 can be determined.
As opposed to mechanically measuring the direction 26 a tiltable joint 6 points, a feature of the actuators (34,36) can be utilized to function as a directional sensor. For example, the pressure of the actuation fluid during the dump state, i.e., the exhaust pressure, can be useful in determining the direction 26 a tiltable joint 6 points. A pressure sensor 60, for example, as shown in
Exhaust pressure of the dumped actuation fluid can be employed in a number of embodiments to determine the direction a tiltable joint 6 points. The relationship between exhaust pressure and the movement of the actuator (34, 36) can be ascertained. More particularly, in one embodiment, the exhaust pressure from an actuator(s) (34, 36) can be used to derive a flow rate of fluid from the actuator (34,36). Bernoulli's equation, for compressible and/or incompressible flow, can be used to derive flow rate from the exhaust pressure, as known to one of ordinary skill in the art. That is, in this embodiment it is possible to measure the pressure, already knowing what the density is to determine the volume flow rate. Measuring the inlet pressure pressure could be another variant of this as the pressure variation appears on the inlet flowrate as well as the out let flow. The inlet flow could be a single sensor for all pads which is correlated to the pad opening sequence to determine which piston is being opened. For example, the flow of fluid into an actuator can be caused by a pressure differential, e.g., between an annulus of the borehole 12 and an actuator (34,36). Pressure differential, fluid density, and/or discharge coefficients can be known and thus flow rate can be derived. Flow rate can be equal to the area multiplied by the velocity of the fluid. Flow rate can be integrated over a time interval to provide a time history of the motion of the actuator, e.g., a piston moving in a cylinder. The integral of the flow rate is the volume of fluid exhausted from the actuator (34,36) over that interval. As the volume of exhausted fluid corresponding to a level of actuation can be known (e.g., total volume of the actuator), the movement of an actuator can be calculated from this set of volumetric data. For example, a known volume of fluid discharged from an actuator can correlate to a known actuator displacement. Correlating can include disposing the tiltable joint 6, or more particularly, the actuator(s) thereof, into a desired orientation and/or angular displacement and measuring the corresponding exhaust pressure or volume of discharged fluid created by the disposing step. The movement of the actuators can be combined to form a state of actuation data set.
With the state of actuation (e.g., movement of the actuators) known, the corresponding movement of the tiltable joint 6 can be calculated, for example, as the mechanical relationship of actuator(s) and tiltable joint 6 can be known. Movement of the tiltable joint 6, or more particularly the deflectable portion thereof, can be referenced as the orientation and/or angular displacement relative to the bottom hole assembly 4 and/or formation 14. Orientation can be desired, for example, when the actuators are not variable, e.g., only achieving a maximum or minimum deflection of the tiltable joint 6. In one embodiment, the orientation can be in the form of a radial direction in which the tiltable joint 6 is skewed relative to the bottom hole assembly 4. The use of orientation can be desirable when determining the magnitude of skew is not desired. For example, when the tiltable joint 6 is capable of always forcing the joint into its maximum level of deflection, we know skew angle A and with the orientation can resolve the direction the tool face 28 points (e.g., inclination and azimuth) with respect to the formation 14.
Pressure sensor(s) 60 can also be utilized to determine the orientation and/or angular displacement of a tiltable joint 6 without integrating a set of exhaust flow rates. In one embodiment, a known orientation and/or angular displacement of the tiltable joint 6 can be correlated to a set of known exhaust pressures. The known exhaust pressure can be the peak exhaust pressure of fluid discharged from an actuator, e.g., in the dump state. A set of known exhaust pressures corresponding to a known orientation and/or angular displacement can be ascertained before using the tiltable joint within a formation 14. A measured exhaust pressure(s) can then be compared to the set of known exhaust pressure(s) to provide a corresponding orientation for that measured exhaust pressure. In such an embodiment, the corresponding orientation is the orientation at the measured exhaust pressure.
As the actuators can be disposed radially, e.g., disposed circumferentially about the axis 30 of the bottom hole assembly 4, the exhaust pressure from the actuators can be utilized for determining the orientation and/or angular displacement of the tiltable joint 6 with respect to the bottom hole assembly 4. In one embodiment, the peak exhaust pressure is caused by the pressure required to overcome the flow restriction when the fluid is exhausted as the actuator, e.g., a piston in cylinder, bellows, etc., is retracted. By measuring this peak exhaust pressure and comparing it to a known peak exhaust pressure corresponding to a known orientation and/or angular displacement of the tiltable joint 6, the orientation and/or angular displacement of the tiltable joint 6 corresponding to the measured peak exhaust pressure can be determined.
In one embodiment, the peak exhaust pressure can be referenced to the actuation signal of the dump valve 42 to determine the position (e.g., orientation and/or angular displacement) of the tiltable joint 4. If the tiltable joint 6 is exactly at the firing angle requested, then the tiltable joint 6 and the peak in exhaust pressure during the dump state are 180 degrees out of phase in that embodiment. If the tiltable joint 6 is at a different position, the peak exhaust pressure would be at a different position with respect to the firing angle. Angular displacement can further be used to determine a rate of angular displacement over a time interval.
Regardless of the method, exhaust pressure measurements can be further manipulated for accuracy. Referring again to the embodiment in
After determining the direction (e.g., orientation and/or angular displacement) the tiltable joint 6 is pointing relative to the bottom hole assembly 4, the direction relative to the formation 14 can be determined, or more specifically, the inclination and azimuth of the tiltable joint 6 relative to the formation. This can be desirable when the bottom hole assembly 4 is rotated, for example, as in rotary steerable drilling. Tiltable joint 6 can be nutating with respect to the axis 30 of the bottom hole assembly 4 during use as the bottom hole assembly 2 is also rotating.
The inclination and azimuth of the tiltable joint 6, for example, that of the tool face 28, can be determined by providing an inclination and azimuth of the bottom hole assembly 4. One non-limiting way of providing inclination and azimuth data is to place the appropriate measuring devices in the bottom hole assembly 4, as known in the art. The orientation and/or angular displacement of the tiltable joint 6 with respect to the bottom hole assembly 4 can be used to resolve the inclination and azimuth of the tiltable joint 6 with respect to the formation 14. In one embodiment, the sleeve can extend between zero deflection (e.g., coaxial with the axis 30 of the bottom hole assembly 4, to a maximum deflection A, as is shown in
The amplitude of the pressure signal can be dependent on fluid, properties, i.e., the drilling fluid; fortunately in an embodiment when all actuators (34,36) receive the same fluid, the orientation can be determined even if the magnitude of tilt is unknown by suitable ratio metric methods.
Angular displacement includes both the orientation and the degree of skew and can be used with the inclination and azimuth of the bottom hole assembly 4 relative to the formation 14 to resolve the inclination and azimuth of the tiltable joint 6 with respect to the formation 14. Inclination and azimuth of the tiltable joint 6 (e.g., bit axis direction 26 of tool face 28 of drill bit 24) can thus be determined without directly measuring the angular displacement between the tiltable joint 6 and bottom hole assembly 4.
Any combination or all of the above steps can be accomplished with a computer. Data on the actuator state (e.g., pressure) obtained through any method outlined above may prove to be noisy. It is appreciated that filtering or other signal conditioning methods can be utilized as desired. Another approach to controlling the signal quality, for example, of the exhaust pressure data, is to develop a signal quality measure. Such a scheme can use measures such as signal—noise ratio, or comparing the magnitude of the signal measured versus a moving average of the signal to determine whether some rapid transient has caused the current sample to be invalid. Logic can be derived (using e.g., fuzzy logic) that will apply weights to the signal based on the quality of the signal such that inaccurate signal data can be ignored and the system reverts to outer loop control.
Numerous embodiments and alternatives thereof have been disclosed. While the above disclosure includes the best mode belief in carrying out the invention as contemplated by the named inventors, not all possible alternatives have been disclosed. For that reason, the scope and limitation of the present invention is not to be restricted to the above disclosure, but is instead to be defined and construed by the appended claims.
