Patent Grant
10508538
This disclosure relates generally to a fluid pressure pulse generator for a downhole telemetry tool, such as a mud pulse telemetry measurement-while-drilling (“MWD”) tool.
The recovery of hydrocarbons from subterranean zones relies on the process of drilling wellbores. The process includes drilling equipment situated at surface, and a drill string extending from the surface equipment to a below-surface formation or subterranean zone of interest. The terminal end of the drill string includes a drill bit for drilling (or extending) the wellbore. The process also involves a drilling fluid system, which in most cases uses a drilling “mud” that is pumped through the inside of piping of the drill string to cool and lubricate the drill bit. The mud exits the drill string via the drill bit and returns to surface carrying rock cuttings produced by the drilling operation. The mud also helps control bottom hole pressure and prevent hydrocarbon influx from the formation into the wellbore, which can potentially cause a blow out at surface.
Directional drilling is the process of steering a well from vertical to intersect a target endpoint or follow a prescribed path. At the terminal end of the drill string is a bottom-hole-assembly (“BHA”) which comprises 1) the drill bit; 2) a steerable downhole mud motor of a rotary steerable system; 3) sensors of survey equipment used in logging-while-drilling (“LWD”) and/or measurement-while-drilling (“MWD”) to evaluate downhole conditions as drilling progresses; 4) means for telemetering data to surface; and 5) other control equipment such as stabilizers or heavy weight subs. The BHA is conveyed into the wellbore by a string of metallic tubulars (i.e. drill pipe).
MWD equipment is used while drilling to provide downhole sensor and status information to surface in a near real-time mode. This information is used by a rig operator to make decisions about controlling and steering the well to optimize the drilling speed and trajectory based on numerous factors, including lease boundaries, existing wells, formation properties, and hydrocarbon size and location. The rig operator can make intentional deviations from the planned wellbore path as necessary based on the information gathered from the downhole sensors during the drilling process. The ability to obtain near real-time MWD data allows for a relatively more economical and more efficient drilling operation.
One type of downhole MWD telemetry known as mud pulse telemetry involves creating pressure waves (“pulses”) in the drill mud circulating through the drill string. Mud is circulated from surface to downhole using positive displacement pumps. The resulting flow rate of mud is typically constant. The pressure pulses are achieved by changing the flow area and/or path of the drilling fluid in a timed, coded sequence as it passes the MWD tool, thereby creating pressure differentials in the drilling fluid. The pressure differentials or pulses may be either negative pulses or positive pulses. Valves that open and close a bypass stream from inside the drill pipe to the wellbore annulus create a negative pressure pulse. All negative pulsing valves need a high differential pressure below the valve to create a sufficient pressure drop when the valve is open, but this results in the negative valves being more prone to washing. With each actuation, the valve hits against the valve seat and needs to ensure it completely closes the bypass; the impact can lead to mechanical and abrasive wear and failure. Valves that use a controlled restriction within the circulating mud stream create a positive pressure pulse. Pulse frequency is typically governed by pulse generator motor speed changes. The pulse generator motor requires electrical connectivity with the other elements of the MWD probe.
One type of valve mechanism used to create mud pulses is a rotor and stator combination where a rotor can be rotated relative to the fixed stator between an opened position where there is no restriction of mud flowing through the valve and no pulse is generated, and a restricted flow position where there is restriction of mud flowing through the valve and a pressure pulse is generated.
According to a first aspect there is provided a fluid pressure pulse generator for a downhole telemetry tool comprising a stator and a rotor. The stator comprises a stator flow diverter radially extending across a flow path for fluid flowing through the fluid pressure pulse generator and having one or more than one stator flow channel therethrough through which the fluid flows. The rotor comprises: a rotor flow diverter radially extending across the flow path for fluid flowing through the fluid pressure pulse generator and having one or more than one rotor flow channel therethrough through which the fluid flows; and one of a rotor male shaft or a rotor female receiver configured to respectively releasably mate with a driveshaft female receiver or a driveshaft male shaft of a driveshaft of a probe of the downhole telemetry tool to releasably couple the driveshaft with the rotor. The rotor flow diverter is axially adjacent the stator flow diverter and the rotor flow diverter is rotatable relative to the stator flow diverter to move the one or more than one rotor flow channel in and out of fluid communication with the one or more than one stator flow channel to create fluid pressure pulses in the fluid flowing through the fluid pressure pulse generator.
The rotor may comprise the rotor female receiver having an internal profile which corresponds to an external profile of the driveshaft male shaft.
The rotor may further comprise a rotor body and the rotor flow diverter may comprise a plurality of radially extending rotor projections spaced around the rotor body, whereby adjacently spaced rotor projections define the rotor flow channels therebetween.
The rotor flow diverter may comprise a rotor disc with the one or more than one rotor flow channel extending therethrough.
The rotor flow diverter may further comprise one or more than one turbine flow channel therethrough, wherein the one or more than one turbine flow channel is angled relative to the axis of rotation of the rotor such that fluid flowing through the one or more than one turbine flow channel causes the rotor to rotate. The rotor flow diverter may comprise a rotor disc with the one or more than one rotor flow channel extending therethrough and a plurality of turbine projections spaced around a circumference of the rotor disc, whereby adjacently spaced turbine projections define the turbine flow channels therebetween.
One or more of the one or more than one rotor flow channel may be angled relative to the axis of rotation of the rotor such that fluid flowing through the one or more than one rotor flow channel causes the rotor to rotate.
The rotor may further comprise a longitudinally extending rotor shaft which is received in a bore extending through the stator. The fluid pressure pulse generator may further comprise a fastener configured to fasten to the rotor shaft to retain the rotor shaft in the bore while allowing rotation of the rotor shaft within the bore. The fastener may be configured to releasably fasten to the rotor shaft. The fastener may be a threaded nut and the rotor shaft may be threaded to receive the threaded nut.
The stator may further comprise a stator body and the stator flow diverter may comprise a plurality of radially extending stator projections spaced around the stator body, whereby adjacently spaced stator projections define the stator flow channels therebetween. The fluid pressure pulse generator may further comprise a spider configured to extend between the stator body and a sub when the downhole telemetry tool is downhole, the spider comprising a plurality of apertures for flow of fluid therethrough. The fluid pressure pulse generator may further comprise a castle nut for releasably securing the spider to the sub.
The stator flow diverter may comprise a stator disc with the one or more than one stator flow channel extending therethrough. The fluid pressure pulse generator may further comprise a castle nut for releasably securing the stator disc to a sub when the downhole telemetry tool is downhole.
According to another aspect, there is provided a downhole telemetry tool comprising a probe and a fluid pressure pulse generator. The probe comprises: a housing enclosing a motor and gearbox subassembly; and a driveshaft having a first end coupled with the motor and gearbox subassembly and an opposed second end extending out of the housing and comprising a driveshaft female receiver or a driveshaft male shaft. The fluid pressure pulse generator comprises a stator and a rotor. The stator comprises a stator flow diverter radially extending across a flow path for fluid flowing through the fluid pressure pulse generator and having one or more than one stator flow channel therethrough through which the fluid flows. The rotor comprises: a rotor flow diverter radially extending across the flow path for fluid flowing through the fluid pressure pulse generator and having one or more than one rotor flow channel therethrough through which the fluid flows; and a rotor male shaft or a rotor female receiver. The rotor flow diverter is axially adjacent the stator flow diverter and the rotor flow diverter is rotatable relative to the stator flow diverter to move the one or more than one rotor flow channel in and out of fluid communication with the one or more than one stator flow channel to create fluid pressure pulses in the fluid flowing through the fluid pressure pulse generator. The probe comprises the driveshaft male shaft and the rotor comprises the rotor female receiver, or the probe comprises the driveshaft female receiver and the rotor comprises the rotor male shaft, whereby the driveshaft male shaft and the rotor female receiver or the driveshaft female receiver and the rotor male shaft releasably mate to releasably couple the driveshaft with the rotor.
The probe may comprise the driveshaft male shaft and the rotor may comprise the rotor female receiver and the rotor female receiver may have an internal profile which corresponds to an external profile of the driveshaft male shaft.
The rotor may further comprise a rotor body and the rotor flow diverter comprises a plurality of radially extending rotor projections spaced around the rotor body, whereby adjacently spaced rotor projections define the rotor flow channels therebetween.
The rotor flow diverter may comprise a rotor disc with the one or more than one rotor flow channel extending therethrough.
The rotor flow diverter may further comprise one or more than one turbine flow channel therethrough, wherein the one or more than one turbine flow channel is angled relative to the axis of rotation of the rotor such that fluid flowing through the one or more than one turbine flow channel causes the rotor to rotate. The rotor flow diverter may comprise a rotor disc with the one or more than one rotor flow channel extending therethrough and a plurality of turbine projections spaced around a circumference of the rotor disc, whereby adjacently spaced turbine projections define the turbine flow channels therebetween.
One or more of the one or more than one rotor flow channel may be angled relative to the axis of rotation of the rotor such that fluid flowing through the one or more than one rotor flow channel causes the rotor to rotate.
The rotor may further comprise a longitudinally extending rotor shaft which is received in a bore extending through the stator. The downhole telemetry tool may further comprise a fastener configured to fasten to the rotor shaft to retain the rotor shaft in the bore while allowing rotation of the rotor shaft within the bore. The fastener may be configured to releasably fasten to the rotor shaft. The fastener may be a threaded nut and the rotor shaft may be threaded to receive the threaded nut.
The stator may further comprise a stator body and the stator flow diverter may comprise a plurality of radially extending stator projections spaced around the stator body, whereby adjacently spaced stator projections define the stator flow channels therebetween. The downhole telemetry tool may further comprise a stator spider configured to extend between the stator body and a sub when the downhole telemetry tool is downhole, the stator spider comprising a plurality of apertures for flow of fluid therethrough. The downhole telemetry tool may further comprise a stator castle nut for releasably securing the stator spider to the sub.
The stator flow diverter may comprise a stator disc with the one or more than one stator flow channel extending therethrough. The downhole telemetry tool may further comprise a stator castle nut for releasably securing the stator disc to a sub when the downhole telemetry tool is downhole.
The downhole telemetry tool may further comprise a probe spider configured to releasably receive and radially lock the probe, the probe spider comprising a plurality of apertures for flow of fluid therethrough. The downhole telemetry tool may further comprise a probe castle nut for releasably securing the probe spider downhole.
This summary does not necessarily describe the entire scope of all aspects. Other aspects, features and advantages will be apparent to those of ordinary skill in the art upon review of the following description of specific embodiments.
Directional terms such as “uphole” and “downhole” are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any apparatus is to be positioned during use, or to be mounted in an assembly or relative to an environment.
The embodiments described herein generally relate to a fluid pressure pulse generator of a measurement while drilling (“MWD”) tool that can generate pressure pulses. The fluid pressure pulse generator may be used for mud pulse (“MP”) telemetry used in downhole drilling, wherein a drilling fluid (herein referred to as “mud”) is used to transmit telemetry pulses to surface. The fluid pressure pulse generator may alternatively be used in other methods where it is necessary to generate a fluid pressure pulse. The fluid pressure pulse generator comprises a fixed stator and a rotor which rotates relative to the fixed stator to generate pressure pulses in mud flowing through the fluid pressure pulse generator.
Referring to the drawings and specifically to
Referring now to
The rotor 60 comprises a generally frusto-conical rotor body 61 that tapers in the downhole direction, a rotor flow diverter comprising a rotor disc 62 extending radially around the downhole end of the rotor body 61, and a rotor shaft 64 extending longitudinally from the downhole end of the rotor body 61. The rotor body 61 includes a bore or female receiver 65 at is uphole end which receives a male shaft 24 at the downhole end of a driveshaft of the probe 26 to releasably couple the driveshaft and the rotor 60 as described in more detail below. The rotor disc 62 comprises a plurality of wedge shaped apertures (rotor flow channels 63) extending therethrough which are equidistantly spaced around the rotor disc 62 and a plurality of radially extending turbine projections 66 equally spaced around the circumference of the rotor disc 62. Each turbine projection 66 comprises an uphole surface and a downhole surface with two side walls extending therebetween. The side walls are each angled or sloped relative to the axis of rotation of the rotor 60 and define turbine flow channels 67 therebetween.
In the embodiment of the fluid pressure pulse generator 30 shown in
To assemble the fluid pressure pulse generator 30, the rotor shaft 64 is received in the stator bore 45 and a threaded nut 25 threads onto a threaded downhole end 64a of the rotor shaft 64 to rotatably couple the rotor 60 to the stator 40 with the rotor flow diverter (rotor disc 62) axially adjacent the stator flow diverter (stator projections 42 or stator disc 49). The nut 25 is releasably coupled to the rotor shaft 64 and can be removed allowing disassembly of the fluid pressure pulse generator 30 for repair or replacement of the rotor 60 or stator 40 if they become damaged or worn. An alternative fastener may be used which is releasably or fixedly secured to the end of the rotor shaft 64 such that the rotor shaft 64 can rotate in the stator bore 45, for example, the nut 25 may be replaced by a clip, bolt or other fastener. In an alternative embodiment (not shown) the stator 40 may include a longitudinally extending stator shaft which is received in an aperture (bore) extending through the rotor 60 and a fastener (for example threaded nut 25) may be positioned in the rotor female receiver 65 and fastened to the stator shaft to couple the rotor 60 and the stator 40 such that the rotor 60 can rotate relative to the stator 40.
The assembled fluid pressure pulse generator 30 is inserted into the downhole end of the sub 27 and the spider 28b or the stator disc 49 abuts a downhole annular shoulder 22 on the internal surface of the sub 27. A castle nut 29b threads into the sub 27 and secures the spider 28b or stator disc 49 in position in the sub 27. Alternative means of fixing the stator 40 to the sub 27 may be used, for example the spider 28b or stator disc 49 may be press fitted to the sub 27.
Spider 28a comprises an inner circular wall 70 with a bore therethrough and an outer circular wall 71. Projections 72 extend radially between the inner wall 70 and the outer wall 71 and define a plurality of apertures which allow mud to flow between the probe 26 and the sub 27 when the probe 26 is positioned in the sub 27. The spider 28a is inserted into the uphole end of the sub 27 and abuts an uphole annular shoulder 23 on the internal surface of the sub 27. A castle nut 29a threads into the sub 27 and secures the spider 28a in position in the sub 27. Alternative means of fixing the spider 28a to the sub 27 may be used, for example the spider 28a may be press fitted to the sub 27.
The probe 26 is received in the bore of the spider 28a. The male shaft 24 at the downhole end of the driveshaft of the probe 26 releasably mates with the female receiver 65 in the rotor body 61 as described in more detail below. A key 21 (shown in
As shown in
In downhole operation, mud pumped from the surface by pump 2 flows between the probe 26 and the sub 27 and along the outer surface of the rotor body 61. When the mud hits the rotor disc 62 it passes through the rotor flow channels 63 and turbine flow channels 67. As the turbine flow channels 67 are angled or sloped relative to the direction of mud flow, mud flowing through the turbine flow channels 67 causes the rotor 60 to rotate continuously in one direction. In the embodiments of the fluid pressure pulse generator 30 shown in
When the rotor flow channels 63 and the stator flow channels 43 align (as shown in
The probe 26 generally houses a motor subassembly (not shown) in electrical communication with an electronics subassembly (not shown). The motor subassembly comprises a motor and gearbox subassembly coupled with the driveshaft. The electronics subassembly includes downhole sensors, control electronics, and other components required by the MWD tool 20 to determine direction and inclination information and to take measurements of drilling conditions, to encode this telemetry data using one or more known modulation techniques into a carrier wave. A controller in the electronics subassembly controls timing of rotation of the rotor 60 so that the pressure pulses 6 transmitted to the surface represent the carrier wave and can be decoded to provide an indication of downhole conditions while drilling. Rotational timing of the rotor 60 may be controlled by any means known in the art, for example, by changing the motor speed or braking.
The angled turbine flow channels 67 cause the rotor 60 to rotate when mud flows through the turbine flow channels 67, thereby conserving battery power. Rotation of the rotor 60 as a result of mud flowing through the turbine flow channels 67 may also generate power for the MWD tool 20. The rotor 60 is coupled to the motor and gearbox subassembly through the driveshaft by the rotor/driveshaft coupling and any generated power can be stored in a capacitor bank or battery or diverted to another power draining component within the MWD tool 20. The turbine flow channels 67 also provide a bypass flow area and mud flows through the turbine flow channels 67 regardless of alignment or non-alignment of the rotor flow channels 63 with the stator flow channels 43. This bypass flow area may reduce pressure build up at the fluid pressure pulse generator 30, especially in high mud flow conditions downhole, which may beneficially reduce damage to the fluid pressure pulse generator 30 that could result from mud pressure build up.
The stator 40 is fixed to the sub 27 by castle nut 29b and the rotor 60 is releasably coupled to the stator 40 via nut 25 and is able to rotate relative to the fixed stator 40. The probe 26 and fluid pressure pulse generator 30 are releasably mated through the rotor/driveshaft coupling. The probe 26 may need to be removed from the sub 27 for various purposes, for example uploading of data, programming and calibration of electrical components, repair and the like. As shown in
Referring now to
The female receiver 65 in the rotor body 61 varies in shape in the embodiments of the rotor 60 shown in
In alternative embodiments (not shown) the rotor/driveshaft coupling may be provided by a male shaft which is fixed to, or part of, the rotor 60 and a female receiver which is fixed to, or part of, the driveshaft of the probe 26. The innovative aspects apply equally in embodiments such as these.
In the embodiments of the rotor 60 shown in
In the embodiment of the rotor 60 shown in
In the embodiments of the rotor 60 shown in
The turbine flow channels 67 of the embodiments of the rotor 60 shown in
It will be evident from the foregoing that provision of more stator flow channels 43 and rotor flow channels 63 will reduce the amount of rotation required to move the rotor flow channels 63 in and out of fluid communication with the stator flow channels 43, thereby increasing the speed of data transmission. In order to accommodate more stator flow channels 43 and rotor flow channels 63 if data transmission speed is an important factor, the width of the stator flow channels 43 and rotor flow channels 63 can be decreased to allow for more stator flow channels 43 and rotor flow channels 63 to be present; however this may make the stator flow diverter and/or rotor flow diverter more fragile and prone to wear. Furthermore, provision of larger flow channels 43, 63 may allow debris in the mud to pass through the flow channels 43, 63 without the channels becoming blocked.
Provision of multiple stator flow channels 43 and rotor flow channels 63 provides redundancy and allows the fluid pressure pulse generator 30 to continue working when there is damage in the area of or blockage of one of the stator flow channels 43 and/or rotor flow channels 63. Cumulative flow of mud through the remaining undamaged or unblocked stator flow channels 43 and rotor flow channels 63 may still result in generation of detectable pressure pulses 6, even though the pulse heights may not be the same as when there is no damage or blockage. In an alternative embodiment (not shown), the rotor flow channels 63 may be narrower or wider than the stator flow channels 43 and the flow channels 63, 43 need not be of corresponding number, size or shape. In a further alternative embodiment (not shown), the rotor flow diverter may include only a single rotor flow channel 63 which rotates in and out of fluid communication with one or more stator flow channels 43 to generate fluid pressure pulses 6.
The rotor/driveshaft coupling releasably couples the driveshaft and rotor such that the probe 26 can be easily decoupled from the rotor 60 and removed from the sub 27 without the need for any special tools or access to the rotor 60 or driveshaft. In known rotor/stator designs, the stator and the rotor are generally attached to the probe via the driveshaft. By coupling the rotor 60 to the stator 40 and releasably coupling the rotor 60 with the driveshaft of the probe 26, the fluid pressure pulse generator 30 can remain within the sub 27 when the probe 26 is removed as shown in
In alternative embodiments (not shown), the stator 40 may be positioned between the rotor 60 and the probe 26 with the stator flow diverter axially adjacent the rotor flow diverter. The rotor body 61 may extend through an aperture in the stator 40 and the male shaft 24 of the driveshaft may be releasably received in the female receiver 65 in the rotor body 61. Alternatively, the rotor 60 may comprise a male shaft (not shown) which extends through an aperture in the stator 40 and is received in a female receiver on or attached to the driveshaft of the probe 26. In each of these alternative embodiments the stator 40 and the rotor 60 are coupled such that the rotor flow diverter can rotate relative to the stator flow diverter and the rotor/driveshaft coupling releasably couples the driveshaft to the rotor 60 allowing transfer of torque so that rotation of the driveshaft rotates the rotor 60 and vise versa.
While particular embodiments have been described in the foregoing, it is to be understood that other embodiments are possible and are intended to be included herein. It will be clear to any person skilled in the art that modifications of and adjustments to the foregoing embodiments, not shown, are possible. For example, in alternative embodiments (not shown), the fluid pressure pulse generator 30 may be positioned at the uphole end of the MWD tool 20.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2015/051251 | 12/1/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2016/086298 | 6/9/2016 | WO | A |
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