Flow operated orienter

Some embodiments of the present invention generally provide an apparatus that may be used in a coiled tubing drillstring and that can switch between effectively straight drilling and curved drilling without halting drilling. Methods for steering a coiled tubing drillstring are also provided. In one embodiment, an apparatus for use in drilling a wellbore is provided. The apparatus includes a mud motor; a housing; an output shaft; and a clutch actuatable between two positions. The clutch is configured to rotationally couple the mud motor to the output shaft when the clutch is in a first position as a result of fluid being injected through the clutch at a first flow rate, and rotationally couple the output shaft to the housing when the clutch is in a second position as a result of fluid being injected through the clutch at a second flow rate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to directional drilling in a wellbore.

2. Description of the Related Art

Conventional directional drilling with jointed pipe is accomplished through use of a Bottom Hole Assembly (BHA) consisting of a bent housing directional drilling motor and directional Measurement While Drilling (MWD) tool in the following fashion.

To drill a curved wellbore section, the drillstring is held rotationally fixed at the surface and the drilling motor will drill a curved wellbore in the direction of the bend in its outer housing. This is termed “slide” drilling because the entire drillstring slides along the wellbore as drilling progresses. The wellbore trajectory is controlled by orienting the BHA in the desired direction by rotating the drillstring the appropriate amount at the surface.

To drill a straight wellbore section, the drillstring is rotated at the surface with the rotary table or top-drive mechanism at some nominal rate, typically 60 to 90 rpm. This is termed “rotating” drilling. In so doing, the tendency of the bent housing motor to drill in a particular direction is overridden by the superimposed drillstring rotation causing the drilling assembly to effectively drill straight ahead.

When drilling with coiled tubing neither “rotating” drilling nor rotational orientation of the BHA can be accomplished without the addition to the BHA of a special rotating device to orient the BHA since coiled tubing cannot be rotated at the surface in the wellbore. One such rotational device, or orienter, operates by rotating in even angular increments, for example 30°, each time the surface pumps are stopped and then re-started. After each pump cycle, the orienter locks into and maintains its rotational position. This “ratcheting” device allows the directional driller to position the directional assembly closely enough to the desired toolface orientation to allow the wellbore to be drilled in a particular direction.

One significant drawback to directional drilling with the ratcheting orienter described above is the fact that drilling must be stopped each time the orienter is actuated. For example, if a rotational change of 210° is needed, drilling is stopped, the BHA is lifted off-bottom, and the pumps must be cycled 7 times to rotate the BHA by the required amount. This non-productive time is significant and has an adverse affect on the average drilling rate. In the case in many Canadian wells, an entire well is drilled in a matter of 6 to 8 hours. The time spent orienting can become a significant portion of the total drilling time.

A second drawback to directional drilling with the ratcheting orienter relates to its inability to drill an effective straight wellbore section. As described above, in conventional directional drilling, continuous drillstring rotation is used to wash-out the directional tendency of a bent-housing motor. This produces a very straight trajectory. When drilling with coiled tubing and a ratcheting orienter, continuous rotation is not possible. Thus the driller is forced to orient slightly left of the desired path and drill some distance ahead. Then after stopping to re-orient right of the desired path, the driller drills ahead again. This process is repeated until the “straight” section is completed. The resulting left-right-left or “wig-wag” wellbore trajectory roughly approximates the desired straight path.

Therefore, there exists a need in the art for an orienter that may be used in a coiled tubing drillstring and that can switch between effectively straight drilling and curved drilling without halting drilling.

SUMMARY OF THE INVENTION

Some embodiments of the present invention generally provide an apparatus that may be used in a coiled tubing drillstring and that can switch between effectively straight drilling and curved drilling without halting drilling. Methods for steering a coiled tubing drillstring are also provided.

In one embodiment, an apparatus for use in drilling a wellbore is provided. The apparatus includes a mud motor; a housing; an output shaft; and a clutch. The clutch is operable to rotationally couple the output shaft to the housing when the clutch is in a first position, rotationally couple the motor to the output shaft when the clutch is in a second position, and actuate from one of the positions to the other of the positions as a result of fluid being injected through the clutch at a flow rate which is greater than or equal to a predetermined threshold flow rate.

In another embodiment, an apparatus for use in drilling a wellbore is provided. The apparatus includes a housing having a splined portion for mating with a second splined portion of a locking sleeve; an input shaft having a splined portion for mating with a first splined portion of the locking sleeve; the locking sleeve having a flow bore therethrough, and a third splined portion rotationally coupling the locking sleeve to a splined portion of an output shaft. The locking sleeve is actuatable between a first axial position and a second axial position by choking of fluid through the flow bore. The locking sleeve mates with the splined portion of the housing in the first axial position and the splined portion of the input shaft in the second axial position. The apparatus further includes the output shaft; and a spring disposed between the output shaft and the locking sleeve, the spring biasing the locking sleeve towards one of the axial positions.

In another embodiment, a method for drilling a wellbore is provided. The method includes drilling in a first direction while injecting fluid through a drilistring at a first flow rate; and changing the flow rate to a second flow rate, wherein an orienter changes the direction of drilling to a second direction, and drilling remains continuous while changing the flow rate. In one aspect, the first direction is a substantially straight direction and the second direction is a curved direction. In another aspect, the first direction is a curved direction and the second direction is a substantially straight direction.

In another embodiment, a method for drilling a wellbore is provided. The method includes providing a drillstring. The drillstring includes a run-in string and an orienter. The orienter includes a motor; a housing coupled to the run-in string; an output shaft; and a clutch, the clutch operable to rotationally couple the output shaft to the housing when the clutch is in a first position, rotationally couple the motor to the output shaft when the clutch is in a second position, and actuate from one of the positions to the other of the positions as a result of fluid being injected through the clutch at a flow rate which is greater than or equal to a predetermined threshold flow rate. The drill string further includes a bent sub rotationally coupled to the output shaft; and a drill bit coupled to the bent sub. The method further includes drilling in a first curved direction, due to the bent sub being at a first orientation, while injecting fluid through the drillstring at a first flow rate; injecting the fluid through the drillstring at a second flow rate, wherein the orienter will rotate the bent sub from the first orientation to a second orientation; and drilling in a second curved direction due to the bent sub being at the second orientation, while injecting fluid through the drillstring at the first flow rate.

In another embodiment, a method for forming a window in a wellbore is provided. The method includes assembling a drillstring. The drillstring includes a run-in string and an orienter. The orienter includes a motor; a housing coupled to the run-in string; an output shaft; and a clutch, the clutch operable to rotationally couple the output shaft to the housing when the clutch is in a first position, rotationally couple the motor to the output shaft when the clutch is in a second position, and actuate from one of the positions to the other of the positions as a result of fluid being injected through the clutch at a flow rate which is greater than or equal to a predetermined threshold flow rate. The drillstring further includes a cutting tool rotationally coupled to the output shaft; a whipstock; and an anchor coupled to the whipstock. The method further includes orienting the whipstock while the clutch is in the first position; and setting the anchor while the clutch is in the first position; actuating the clutch to the second position, wherein the motor rotates the cutting tool; and forming the window.

DETAILED DESCRIPTION

The term “coupled” as used herein includes at least two components directly coupled together or indirectly coupled together with intervening components coupled therebetween.

FIG. 1is a diagram of a coiled tubing Bottom Hole Assembly (BHA)100, according to one embodiment of the present invention. The coiled tubing BHA100includes: a drill bit5, a bent-housing drilling motor10, Measurement While Drilling (MWD) module15, orienter200, and connector25. As discussed above, bent-housing drilling motor10will cause drilling in a curved direction provided that the drillstring is rotationally fixed. Alternatively, a bent sub and a straight-housing motor could be used instead of the bent-housing motor10. The bent-housing motor10is a mud motor, which harnesses energy from drilling fluid by channeling it between a profiled rotor and stator, thereby imparting the energy into rotational motion of the rotor. The drill bit5is coupled to the rotor of the motor10.

MWD module15may incorporate, for example, magnetometers and accelerometers to measure and transmit to the surface data indicative of borehole inclination and direction. The connector25couples the BHA100to a string of coiled tubing30. The connector25is also coupled to the orienter200. Discussed in more detail below, the orienter200contains a device which converts fluid energy into rotational energy, such as a mud motor, which is selectively rotationally coupled to the MWD module15, the bent-housing drilling motor10, and the drill bit5. When rotationally coupled, the orienter200effects drilling in an overall straight direction (analogous to a corkscrew) and, when not, allows drilling in a curved direction.

FIG. 2is a more detailed schematic of the orienter200ofFIG. 1. The orienter200includes a housing270. Disposed in the housing270is stator265. The stator265corresponds with a rotor260. The rotor260and stator265transform fluid energy into mechanical energy, resulting in the rotation of the rotor. The rotor260is rotationally coupled through a transmission255and a speed reducer250to an input shaft320(seeFIG. 3) of a clutch300. The clutch300selectively rotationally couples the input shaft320to an output shaft235. The output shaft235is supported for rotation relative to the housing270by two sets240a,bof bearings

FIGS. 3A and 3Bare sectional views of the clutch300ofFIG. 2in an engaged and disengaged position, respectively. The clutch300has an axial flow bore therethrough. The clutch includes the input shaft320which has radial fluid channels therethrough (two shown). Flow of fluid through the clutch is denoted by arrows325. The input shaft320is supported for rotation relative to the housing270by a bearing330. The input shaft320is selectively rotationally coupled to a locking sleeve305. This coupling is achieved by a splined portion320aof the input shaft320which corresponds with a splined portion305aof the locking sleeve305, thereby rotationally coupling the two portions together when the locking sleeve305is moved axially into engagement with the input shaft320.

The locking sleeve305is selectively rotationally coupled to the housing270. This coupling is achieved by a second splined portion305bof the locking sleeve305which corresponds with a splined portion270aof the housing270, thereby rotationally coupling the two portions together when the locking sleeve305is moved axially into engagement with the housing270. The locking sleeve305is rotationally coupled to the output shaft235but is free to move axially relative to the output shaft. This coupling is achieved by a third splined portion305cof the locking sleeve305which corresponds with a splined portion235aof the output shaft which extends axially along a travel path of the locking sleeve305, thereby rotationally coupling the two portions together regardless of the axial position of the locking sleeve305relative to the output shaft235.

The locking sleeve305is axially biased away from the output shaft235by biasing member, such as spring315, which is disposed between two facing shoulders of the two parts. A nozzle310is received in a recess formed in the locking sleeve305and is exposed to the fluid path325. The nozzle310is disposed between a first portion306aof a flow bore306of the locking sleeve305and a second portion306bof the bore306. The nozzle310enables the locking sleeve305to act as a dynamic flow piston. Flow is choked through the nozzle310, resulting in a pressure drop across the nozzle and creating an actuation force which counters the biasing force acting on the locking sleeve305provided by the spring315. In this manner, the axial position of the locking sleeve305may be controlled by the injection rate of fluid through the clutch300. Optionally, a first sealing element335ais disposed between the locking sleeve305and the housing270and a second sealing element335bis disposed between the locking sleeve and the output shaft235. The optional sealing elements335a,bprevent excess leakage from the flow path325.

Operation of the orienter200is as follows. Rotation of the orienter200is powered by the flow of drilling fluid provided by the surface pumps (not shown). In the engaged operating mode (FIG. 3A), the orienter200rotates the bent-housing motor10and MWD module15at a slow, but continuous speed, for example between about 2 and about 5 rpm, thus facilitating the “straight” drilling capability similar to that accomplished by the rotational technique employed when drilling with jointed pipe, discussed above. In this mode, the surface pumps are injecting fluid through the orienter200at a flow rate greater than or equal to a predetermined threshold flow rate so the actuation force from the pressure acting on the locking sleeve305is sufficient to compress the spring315, thereby holding the locking sleeve305in a position to engage the splined portions305a,320a.Engagement of the splined portions means that the input shaft325is rotationally coupled to the locking sleeve305which is rotationally coupled to the output shaft235. Alternatively, the clutch300could be configured so that the locking sleeve305is rotationally coupled to the housing270in the engaged position and rotationally coupled to the input shaft320in the disengaged position.

When it is desired to change from straight ahead drilling to oriented directional drilling, the flow rate of the surface pumps is decreased by a pre-selected amount to a flow rate that is less than the predetermined threshold flow rate, thereby decreasing the pressure acting on the locking sleeve305. The spring315will then move the locking sleeve305out of engagement with the input shaft320and into a position where the splined portions270a,305bare engaged (FIG. 3B). The locking sleeve305, which is rotationally coupled to the output shaft235, is now rotationally coupled to the housing270, which is stationary. In this mode, drilling will proceed in the direction determined by the rotational orientation of the bent-housing motor10. It is not necessary to stop drilling ahead to change from straight-ahead directional drilling to oriented drilling. When it is desired to change from oriented drilling to straight ahead drilling, the flow rate of the pumps is increased to a flow rate which is greater than or equal to the predetermined flow rate, thereby moving the locking sleeve305into engagement with the input shaft320and rotationally coupling the input shaft320to the output shaft235.

In addition to changing between straight ahead and directional drilling, the orienter200may be used to adjust an orientation of the directional drilling. In order to accomplish this, the clutch300is engaged for a relatively short time to rotate the bent sub10from a first orientation to a desired second orientation.

Some advantages of the orienter200over the prior art are as follows. No electric line is required in the coiled tubing30to provide power to the orienting device. This means that the system can be used with any coiled tubing drilling rig. A second difference from most prior art systems is that the orienter200, when engaged, provides continuous rotation of the bit5, motor10, and MWD module15. A third difference is that unlike some prior art systems, drilling need not stop to adjust BHA orientation. Finally, unlike any of the electrically powered systems which are very complex electro-hydraulic systems, the orienter200is a purely mechanical tool much less susceptible to failure in a wellbore.

FIG. 4Ais a cross sectional view of a drillstring415inserted into a wellbore410, according to another embodiment of the present invention. The wellbore410is drilled from a surface411, which may be either a surface of land or sea. Typically, the wellbore410is cased with a casing414. An annulus412between the drilled wellbore and the casing414is sealed with a solidifying aggregate such as concrete. The drillstring415includes a run-in string416, such as coiled tubing or a string of drill pipe. Various components can be assembled as part of the drillstring415. For example, beginning at the lower end of the arrangement, an anchor438, such as a bridge plug, packer, or other setting device, is releasably coupled to the drillstring415generally on a lower end of the arrangement. Preferably, the anchor438is hydraulically set so that the anchor438can be actuated remotely and thus does not require a separate trip. The hydraulic anchor438may be set with a hydraulic fluid flowing through a tube (not shown). The drillstring415shown inFIGS. 4A-4Ccan be used to set the anchor438and the whipstock420and begin cutting a window436(seeFIG. 4C) in the wellbore410in a single trip.

A whipstock420is attached to the anchor418and includes an elongated tapered surface that guides a cutting tool, such as a mill422, outwardly toward casing414. The mill422is releasably coupled to the whipstock420with a connection member424, for example a shear pin, that may be later sheared downhole by an actuation force, such as by rotation of mill422, by pulling on the run-in string416, or otherwise. A spacer or watermelon mill426may also be coupled to the mill422. The spacer mill426typically is a mill used to further define the hole or window created by the mill422. In other embodiments, other types of cutting tools may be employed, such as hybrid bits that are capable of milling a window and continuing to drill into the formation. An exemplary hybrid bit is disclosed in U.S. Pat. No. 5,887,668 and is incorporated by reference herein.

In some arrangements, a stabilizer sub428is assembled as part of the drillstring415. The stabilizer sub428has extensions protruding from the exterior surface to assist in concentrically retaining the drillstring415in the wellbore410. A clutched mud motor400can be assembled with the drillstring415above the mills422,426. The clutched mud motor400may be similar to the orienter200except that the rotor260, stator265, speed reducer250, and transmission255may be replaced by a mud motor. When the clutch300is engaged, the mud motor400rotates the mills422,426while the drillstring415remains rotationally stationary (if the run-in string416is drill pipe, the drill pipe may be rotated in tandem with the mills422,426or held rotationally stationary). A position measuring member, such as an MWD tool432, is coupled above the motor400. The MWD tool432may require a certain level of flow Fm to activate and provide feedback to equipment located at the surface411.

When the run-in string416is coiled tubing, an orienter434(see alsoFIG. 5) is assembled as part of the drillstring415above the MWD tool432. When the run-in string416is drill pipe, the whipstock420may be oriented by turning the drill pipe from the surface411and the orienter434is not needed. The orienter434includes housing elements502-505connected to one another, has a passage for, fluid such as drilling fluid, and may be activated for rotation of the whipstock420, so that the whipstock420may be properly oriented. Referring toFIG. 5, the orienter434includes an actuator valve521arranged to choke the passage, so that the orienter434can be activated for the rotation, a piston518adapted for providing the rotation after the through passage has been choked, and sets of co-operating guides, preferably twisted splines526,527, adapted for causing the piston518to rotate relative to the housing502-505. The splines526,527are formed in an inner surface of the housing element503and an outer surface of the piston518. Thus, the orienter434can rotate the whipstock420to a desired orientation within the wellbore410, while the MWD tool432provides feedback to determine the orientation. A more detailed discussion of the principles and operation of the orienter434may be found in U.S. Pat. No. 6,955,231, entitled “Tool for Changing the Drilling Direction while Drilling,” which is hereby incorporated by reference in its entirety.

The flow rate Fo required to actuate the orienter434may be set above the flow rate required to activate the MWD tool432, below the flow rate Fa required to set the anchor438, and below the flow rate required to engage the clutch300of the clutched motor400Fc. The flow rate Fa required to set the anchor may be set below the flow rate Fc required to engage the clutch300of the clutched motor400. To summarize, preferably, Fc>Fa>Fo>Fm. In the case that the run-in string416is drill pipe, a similar relation may be used with the exception that Fo would be omitted. In light of this relation, it may be observed that when setting the anchor, some unintended actuation of the orienter434may occur. To reduce this, the orienter is equipped with a choke valve541which controls the speed of the orienter434. The choke valve541may be configured to slow the orienter sufficiently such that the unintended actuation is negligible. Further, the orienter434may be configured with a relatively short stroke and/or a gradual twist in the splines to further reduce the unintended actuation. Alternatively, or in addition to, the unintended actuation may be measured or estimated and the MWD tool configured with an offset to compensate for the unintended actuation. Alternatively, the offset may be manually performed at the surface.

FIG. 4Bis a sectional view of the drillstring415with an anchor438set in position. The whipstock420is oriented using the orienter434to a desired position indicated by the MWD tool432, while the clutch300allows flow through the motor400without engagement of the motor. The hydraulic anchor438is set to fix the whipstock420at the desired orientation.

FIG. 4Cis a cross sectional view of the whipstock420set in position and the mill422cutting a window436through the casing414at an angle to the wellbore410. In one aspect, the connection member is sheared by pulling on the run-in string416. As the flow rate and/or pressure of fluid within the drillstring415increases, the clutch300engages the motor400which turns the mill422. In another aspect, sufficient torque created by the motor400shears the connection member424between the whipstock420and the cutting tool422. The mill422begins to turn and is guided at an angle to the wellbore410by the whipstock420. As the drillstring415is further lowered downhole, the mill422cuts at an angle through the casing414and creates an angled window436therethrough. In some embodiments, the casing414may not be placed in a wellbore410. It is to be understood that the arrangements described herein for cutting an angled window apply regardless of whether the casing414is placed in the wellbore. Actuation of the orienter434during this process does not affect the ability of the motor400to operate the mill422nor the direction of the mill422because the mill is guided by the whipstock420.