Patent Application
20140158427
The present invention relates to the field of oil and gas exploration, and in particular downhole drilling activities. More specifically, the present invention is a remotely controlled directional drilling tool for use in downhole drilling.
It is known to utilise a Surface-Adjustable Bent (SAB) housing when drilling a well which has to follow a particular geometric path rather than one which is a “straight-hole”. The SAB housing typically forms part of a downhole drilling motor and is located between the power and bearing sections of the motor. The SAB housing comprises a fixed upper section connected to the power section of the motor, and a lower section which is rotatable relative to the upper section and connected to the bearing section and drill bit. The joint between the upper and lower sections of the SAB housing is angled such that the rotational axis of the lower section is at an angle α relative to the longitudinal axis of the upper section. The angle α is typically in the range of 0-3°, and the angle may be adjusted manually at the surface prior to commencing a drilling operation.
These SAB housings have several drawbacks. Firstly, the maximum bend angle between the longitudinal axes of the upper and lower sections of the housing is 2α, but the maximum angle is limited to a smaller angle downhole due to space constraints within the borehole. Secondly, any adjustment of the housing must be carried out manually at the surface, adding to the time and associated costs of the drilling operation.
A solution to these problems was presented in U.S. Pat. No. 4,836,303, in which the upper section of the housing is radially offset from the longitudinal axis of the motor such that the longitudinal axis of the upper section is at an angle to the longitudinal axis of the motor. In addition, the device can be remotely adjusted downhole, thereby avoiding the need for the drill string to be recovered to the surface for adjustment of the housing. These two features provide a greater range of angle adjustment for the housing. However, the drilling operation has to be halted and the drill string lifted off-bottom in order for the angular displacement of the upper and/or lower sections to be adjusted, thereby still involving a significant amount of non-drilling time (NDT) in any drilling operation.
It is an aim of the present invention to obviate or mitigate one or more of these disadvantages with existing tools.
According to a first aspect of the present invention there is provided a directional drilling tool, comprising:
The first actuator may be housed in the first swivel member. The first actuator may be a first motor drive comprising a first motor having a first rotating drive shaft, wherein the first motor drive transforms an initial rotational motion of the first drive shaft into an intermediate axial motion, and transforms the axial motion into a final rotational motion of the second swivel member.
The first motor drive may further comprise:
The first output shaft may be a follower shaft and the second drive member may include a socket cam in which the first end of the first output shaft is engaged.
The second actuator may be a second motor drive housed in the first bend member, the second motor drive lying along a drive axis which is at the non-zero angle relative to the longitudinal axis of the tool.
The second motor drive may comprise a second motor having a second rotating drive shaft, wherein the second motor drive transforms an initial rotational motion of the second drive shaft into an intermediate axial motion, and transforms the axial motion into a final rotational motion of the second bend member.
The second motor drive may further comprise:
The second output shaft may be a follower shaft and the fourth drive member may include a socket cam in which the first end of the second output shaft is engaged.
The drilling tool may further comprise a remote control system having an operator control interface, the control system adapted to activate the first and second actuators in response to pre-programmed instructions and/or manual inputs at the control interface.
The control interface may include a graphical display means indicating the path of the tool.
According to a second aspect of the invention there is provided a directional drilling system, comprising:
Each of the swivel and adjustable bend sections may further comprise one or more positional sensors adapted to communicate the rotational position of the swivel and adjustable bend sections to the controller.
According to a third aspect of the invention there is provided a control process for a directional drilling tool having a first swivel member non-rotatably attached to a first end of the tool and a second swivel member rotatably coupled to the first swivel member and rotatable relative thereto about a first axis of rotation which is co-axial with a longitudinal axis of the tool; a first actuator adapted to selectively rotate the second swivel member about the first axis of rotation; a first bend member non-rotatably attached to the second swivel member and a second bend member rotatably coupled to the first bend member, wherein the first bend member is co-axial with the longitudinal axis, and the second bend member is rotatable relative to the first bend member about a second axis of rotation which is at a non-zero angle relative to the longitudinal axis; and a second actuator adapted to selectively rotate the second bend member about the second axis of rotation, the process comprising the steps of:
The desired drilling path is selected based upon the pre-programmed instructions and/or manual control inputs. The determining step compares the current orientation and position of the drill bit with the desired drilling path set by the pre-programmed instructions and/or manual control inputs. The step of applying any necessary modifications therefore includes applying corrective feedback from the control system should the determining step have established that the drill bit has diverged from the desired drilling path.
The process may further comprise the step of displaying the current drilling path on an operator control interface of the remote control system.
According to a fourth aspect of the invention there is provided a motor drive for rotating a first body relative to a second body, the motor drive comprising a motor having a rotating drive shaft, wherein the motor drive transforms an initial rotational motion of the drive shaft into an intermediate axial motion, and transforms the axial motion into a final rotational motion of the second body.
The motor drive may further comprise:
The helical output shaft may be a follower shaft and the second drive member may include a socket cam in which the first end of the helical output shaft is engaged.
A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which:
a) and 2(b) are vertical section and side views, respectively, of a motorised swivel forming part of the drilling tool of
a) and 5(b) are vertical section and side views, respectively, of an adjustable bent sub forming part of the drilling tool of
a) and 6(b) are vertical section and side views, respectively, of the adjustable bent sub of
a) and 7(b) are vertical section and side views, respectively, of the adjustable bent sub of
Below the swivel 6, the tool 1 further comprises a dump valve section 8 and a power section 10, both of which are of a type known in the art. Below the power section 10 is an adjustable bend section, also known as a bent sub, 12 having a first bend member attached to the power section 10 and a second bend member attached to the remaining downstream components of the tool 1. The first and second bend members may be selectively rotated relative to one another so as to rotate an attached drill bit (not shown) relative to the swivel 6, dump valve 8 and power sections 10 of the tool 1. Completing the downstream elements of the tool 1 are a transmission assembly 14 and a bearing section 16, which are again both of a type known in the art.
FIGS. 2,3 and 4 show the components of the swivel 6 in more detail. The swivel comprises a first tubular member 18 and a second tubular member 20. The free end of the first member 18 is attached to a drill string by way of a threaded connection (not shown). The free end of the second member 20 is non-rotatably attached, either directly or indirectly, to the power section 10 by a threaded connection (not shown). A bore 22 extends longitudinally through the swivel so as to permit drilling mud to pass into the power section 10 from the drill string above.
The swivel 6 includes an actuator adapted to selectively rotate the second member 20 relative to the first member 18. In this preferred embodiment, the actuator is a motor drive housed in the first member 18. The motor drive includes a motor compartment 24 located between the outer wall of the first member 18 and the bore 22. Located within the motor compartment 24 is a high voltage (400-600V) electric motor 26, which has a thermally insulated coil and is adapted so as to be highly resistant to corrosion and abrasion. The motor 26 has a drive shaft 28 which is supported by a bearing 30 on a support plate 32 having a niche 34 in which the bearing 30 is located.
The drive shaft 28 is engaged with an annular gear 40 which is co-axial with the bore 22. The gear 40 is integrally formed with, or non-rotatably attached to, an upper end of a first drive member in the form of a power screw 42. The screw 42 is located within a second drive member, or socket, 44 which has an internal thread which engages with an external thread on the screw 42. The socket 44 has a plurality of external splines 46 which engage with corresponding splines 47 on the internal surface of the first tubular member 18. The splines 46,47 prevent relative rotation between the socket 44 and first tubular member 18, but permit relative movement between the two in the axial direction. Thus, rotation of the gear 40 and power screw 42 by the motor 26 effects an axial movement of the socket 44 relative to the screw 42 and first tubular member 18.
An output shaft 48 is connected to the socket 44 via a spiral socket cam 50, as best seen in
The socket 44 cannot move axially unless the power screw 42 is rotated. Consequently, the socket 44 isolates the motor 26 from any reaction moments from the second tubular member 20. In the same way, the socket 44 provides a locking mechanism to the swivel 6 and tool 1 that locks the first and second tubular members 18,20 at the chosen rotational angle relative to one another. This arrangement adds to the overall reduction ratio of the drive and increases the accuracy and sensitivity of the output.
The axial motion of the power screw 42 is limited in the downward direction (when viewed in
The swivel 6 is preferably filled with oil to reduce friction and to avoid sticking of the moving components. Accordingly, a number of seals are provided to prohibit mud flowing through the bore 22 from contaminating the oil. A first oil seal 56 is provided between the first tubular member 18 and the output shaft 48 where the output shaft 48 exits the lower end of the tubular member 18. A second oil seal 58 is provided between the lower end of the power screw 42 and the output shaft 48, whilst a third oil seal 60 is provided between the annular gear 40 and the sealing sleeve 38. A sealing gasket 62 is deployed between the adjacent ends of the first and second tubular members 18,20 to prevent any contamination or leakage between the mud flowing through the bore 22 and the oil inside the swivel 6.
An additional straight sleeve 119 is fitted to the upper end of the first member 118 to ensure a straight connection with the power section 10 above. The output shaft 123 passes through the bore 122 with enough space to accommodate the eccentricity in the shaft motion, which is shown in
The relative angular displacement θ between the longitudinal axes L1,L2 of the first and second members 118,120 will follow an elliptical path with a maximum bend angle between them of 2a, where α is the angle of the rotational axis R relative to the longitudinal axis L1 of the first member 118, as shown in
Rotation of the swivel 6 then rotates the bend sub 12 to adjust the drilling direction. Tests have been carried out to show the correlation between the rotation of the second member 120 relative to the first member 118 and the resulting bend angle between the axes L1 and L2 in addition to the corresponding direction of the tool face. The study was made for a bent sub where the angle is a. The results indicated that as the second member 120 rotates 180° relative to the first member 118, the bend angle between the longitudinal axes L1,L2 of the first and second members 118,120 reaches 2α and then decreases as the second member 120 rotates through 360°.
Closed form expressions have been developed for calculating the bend angle and direction based on simple trigonometry rules. The closed form expressions for the bend and direction are as follows:
where θ is the relative angular displacement between the longitudinal axes L1 and L2, and α is the angle of the rotational axis R relative to the longitudinal axis L1.
The controller 74 can operate in automatic mode, where it will send control signals to the motors of the swivel 6 and/or bent sub 12 based on data received from the MWD tool 72 in order to keep the drill bit 70 on a preset path, or else in manual mode where it will send signals to the motors in response to manual inputs by the operator on the RSS unit 76. One or more sensors may be provided in each of the swivel 6 and bent sub 12 to send positional data back to the controller 74 so that the controller has real time positional information on the operational positioning of the swivel 6 and bent sub 12.
The flow diagram of
Referring back to
Once modification process step 210 has been completed, an optional display step 212 may display the current drilling data on the RSS unit for the operator. If the decision step 208 determines that the drilling procedure is still within the desired limits, the process will skip the process step 210 and proceed straight to display step 212. Following the display step 212, the decision step 214 will determine whether a system stop has been initiated, either manually by the operator or automatically due to a malfunction detected by the controller 74. If no stop is initiated, the process will continue to input step 216 where the real-time data being received from the MWD tool is received. The process will then begin a further loop through the steps at processing step 204. If a system stop is determined at decision step 214, the process will pass to stop step 218 and shut down.
The present invention provides a directional drilling tool whose drilling angle and direction can be remotely adjusted simultaneously without interrupting the drilling operation. As the tool can be steered whilst drilling is ongoing, drilling process efficiency is maximised with minimal NDT.
The motor drive arrangements employed in both the swivel and bent sub provide high accuracy rotational movements, as well as locking the rotating second portions at the desired angle relative to the fixed first portions. The drive arrangements also isolate the motors from any reactive loads from the drill bit.
The tool, system and method of the present invention are particularly suited to coiled tubing drilling operations. However, they may also be employed in other direction drilling operations if desired.
Whilst the preferred embodiment of the directional drilling tool includes dump valve as a top sub, it should be appreciated that in certain applications the dump valve is not necessary. In such instances, the dump valve may be replaced by an alternative top sub such as, for example, a crossover sub, float sub or flex sub.
Furthermore, although the preferred actuators for the swivel and bent sub within the tool are motor drives other actuator arrangements may be used instead. For example, the actuators may be hydraulically-operated clutches utilising the reactive torque coming from the power section of the tool. In this instance, the second members of the swivel and bent sub would only rotate in one (anticlockwise) direction. The clutches may be engaged and disengaged by adjusting the hydraulic pressure on a conical part male against a cooperating female part. This engagement and disengagement would be carried out by the remote control system on the surface.
The motor drive of the present invention is not limited to use in directional drilling tools and systems. The motor drive can be used in other applications, downhole or otherwise, where a first body is to be rotated relative to a second body. For example, the motor drive could be employed in a swivel sub for use where rotation of the lower part of a work string relative to an upper part of the string is desired.
These and other modifications and improvements may be incorporated without departing from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1112104.3 | Jul 2011 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EG2012/000026 | 7/15/2012 | WO | 00 | 1/10/2014 |
