Patent Application
20200040683
Embodiments of the present disclosure relate to sidetrack drilling for hydrocarbons. In particular, this disclosure relates to a sidetrack assembly for creating a lateral wellbore from a parent wellbore. More particularly still, this disclosure relates to a sidetrack assembly for supplying cement and forming a lateral wellbore.
In recent years, technology has been developed which allows an operator to drill a primary vertical well, and then continue drilling an angled lateral borehole off of that vertical well at a chosen depth. Generally, the vertical, or “parent” wellbore is first drilled and then supported with strings of casing. The strings of casing are cemented into the formation by the extrusion of cement into the annular regions between the strings of casing and the surrounding formation. The combination of cement and casing strengthens the wellbore and facilitates the isolation of certain areas of the formation behind the casing for the production of hydrocarbons.
A lateral wellbore can also be formed off of an open hole parent wellbore. Forming lateral or “sidetrack” wellbore, a tool known as a whipstock is positioned in the parent wellbore at the depth where deflection is desired, typically at or above one or more producing zones. The whipstock is used to divert milling bits into a side of the parent wellbore to create a pilot borehole in the parent wellbore. Thereafter, a drill bit is run into the parent wellbore. The drill bit is deflected against the whipstock, and urged through the pilot borehole. From there, the drill bit contacts the rock formation in order to form the new lateral hole in a desired direction. This process is sometimes referred to as sidetrack drilling.
When forming the lateral wellbore through the parent wellbore, an anchor is first set in the parent wellbore at a desired depth. The anchor is typically a packer having slips and seals. The anchor tool acts as a fixed body against which tools above, it may be urged to activate different tool functions. The anchor tool typically has a key or other orientation-indicating member.
A whipstock is next run into the wellbore. The whipstock has a body that lands into or onto the anchor. A stinger is located at the bottom of the whipstock which engages the anchor device. At a top end of the body, the whipstock includes a deflection portion having a concave face. The stinger at the bottom of the whipstock body allows the concave face of the whipstock to be properly oriented so as to direct the milling operation. The deflection portion receives the milling bits as they are urged downhole. In this way, the respective milling bits are directed against the surrounding wellbore for forming the pilot borehole.
In order to form the pilot borehole, a milling bit, or “mill,” is placed at the end of a string of drill pipe or other working string. In some milling operations, a series of mills is run into the hole. First, a starting mill is run into the hole. Rotation of the string with the starting mill rotates the mill, causing a portion of the wellbore to be removed. This mill is followed by other mills, which complete the pilot borehole or extend the lateral wellbore.
In some instances, prior to drilling the sidetrack, it may be desirable to isolate the formation below the whipstock. The formation may be isolated by supplying cement below the whipstock. This is generally at least a two trip process. A first trip to supply the cement, and a second trip to mill the sidetrack wellbore.
There is, therefore, a need for a sidetrack assembly that can perform a cementing operation and form at least a portion of a lateral wellbore in a single trip downhole.
An assembly for forming a lateral wellbore includes a mill having a bore and a plurality of blades; a whipstock having an inclined surface for guiding movement of the mill, the mill releasably connected to the whipstock; and a tubing disposed in the bore of the mill and the whipstock. In one example, at least one of the plurality of blades is disposed in a slot formed in the whipstock.
In another embodiment, a method for forming a lateral wellbore in a wellbore includes lowering a work string having a drilling member releasably attached to a whipstock, and a tubing connected between the mill and the whipstock. The drilling member includes a blade disposed in slot of the whipstock. The method also includes supplying cement through the drilling member and the tubing to a location below the whipstock; releasing the drilling member from the whipstock; and moving the drilling member along an inclined surface of the whipstock to form at least a portion of the lateral wellbore.
In another embodiment, an assembly for forming a lateral wellbore includes a mill having a bore and a plurality of blades and a lug; a whipstock having an inclined surface for guiding movement of the mill and a lug, the mill releasably connected to the whipstock; and a tubing disposed in the bore of the mill and the whipstock, wherein the lug of the mill is engageable with the lug of the whipstock and configured to apply a downward force to lug of the whipstock.
So that the manner in which the above recited features of the present disclosure are attained and can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the drawings that follow. The drawings illustrate only selected embodiments of this disclosure, and are not to be considered limiting of its scope.
In this embodiment, the sidetrack assembly 100 includes a drilling assembly releasably attached to a whipstock 120. The drilling assembly may be a mill 150 or a drill bit. The mill 150 is attached to the upper end of the whipstock 120. The lower end of the whipstock 120 is attached to an adapter 180 for connection to a downhole tool, such as a packer, a fishing tool, and a cement basket. In another embodiment, the adapter 180 is integrated with the whipstock 120. In another embodiment, the adapter 180 is integrated with the downhole tool 195.
The whipstock 120 includes a concave, inclined surface 125 for guiding the path of the mill 150. In one embodiment, the concave surface 125 at the upper portion of the whipstock 120 is an inclined cut out, as shown in
During run-in, the mill 150 is attached to the upper end of the whipstock 120 using a shearable member 128 such as a shear screw, as shown in
As shown in the perspective view of
The mill 150 is equipped with two or more blades 170, such as two, four, five, six, and eight blades. As shown in
In one embodiment, the sidetrack assembly 100 includes a flow path for supplying cement from the mill 150 to the wellbore below the whipstock 120. Referring to
The upper end of the tubing 190 extends out of the whipstock 120 and is connectable with the offset passage 155C of the mill 150. During installation, the upper end of the tubing 190 is inserted into the offset passage 155C. The sealing members 157 engage the tubing 190 to prevent leakage. In one embodiment, the section of the tubing 190 inserted into the offset passage 155C is from 2 in. to 36 in., from about 3 in. to 24 in., or from about 6 in. to 18 in.
During assembly, the mill 150 is releasably attached to the whipstock 120. The tubing 190 is inserted into the offset passage 155C, and the blades 171, 172 are positioned in slots 131, 132, respectively, of the attachment section 130. The shearable screw 128 is inserted through the hole 138 of the attachment section 130 and the slot 158 of the mill 150 to releasably attach the mill 150 to the whipstock 120. In this example, the lug 163 of the mill 150 is engaged with the lug 133 of the attachment section 130. In this respect, axial force may be transmitted from the mill 150 to the whipstock 120.
In operation, a downhole tool 195, such as a packer, is attached to the whipstock 120. The mill 150 and the whipstock 120 are lowered into the wellbore using a workstring. In this example, the wellbore is an open hole wellbore. However, this operation may be performed in a cased wellbore. While being lowered, the mill 150 can apply a downward force on whipstock 120 via the lugs 133, 163. After reaching the location of the pilot borehole to be formed, the packer is set below the pilot borehole. In one embodiment, the inclined surface 125 of whipstock 120 is oriented to the appropriate azimuth in the borehole to guide the path of the mill 150. The wellbore below the packer is isolated from the whipstock 120. Cement is supplied through the workstring, the bore 155 of the mill 150, the tubing 190, and the passage of the adapter 180. The cement exits below the packer and into the wellbore. In another embodiment, cement is supplied below the packer before setting the packer. In yet another embodiment, the cement is located above and below the packer. In one embodiment, the cement is used to inflate the packer. For example, an actuating device, such as a ball or a dart, is dropped into the workstring. The actuating device travels through the bore 155 of the mill 150, the tubing 190, and lands in a downhole tool, such as a packer or an anchor, attached to the whipstock 120. Pressure is increased to cause the ball to shift a sleeve in the downhole tool, thereby opening a port in the downhole tool. Fluid can be supplied through the port to actuate the downhole tool. Exemplary fluids include cement, drilling fluid such as a drilling mud, and completion fluid such as brine. In some embodiments, the downhole tool includes a one way valve such as a check valve that prevents the fluid from flowing out of the downhole tool. If the downhole tool is a packer, the fluid can be used to inflate the packer. In some embodiments, fluid flow through the downhole tool is re-established by increasing pressure to release the ball from the sleeve.
To release the mill 150, a tension force is applied to the mill 150 by pulling up on the mill 150. A sufficient force is applied to break the shear screw 128. After release, the mill 150 is pulled away from the whipstock 120 to separate the tubing 190 from the mill 150. The mill 150 is then urged along the whipstock 120, which deflects the mill 150 outward into engagement with the wellbore. The tubing 190 will be milled as the mill 150 travels along the whipstock 120. The mill 150 is operated to form at least a portion of the lateral wellbore. Thereafter, the mill 150 is retrieved. In this manner, a supplying cement through the whipstock and forming at least a portion of the lateral wellbore can be achieved in a single trip. In some instances, a drill bit is lowered into the wellbore in a second trip and operated to extend the lateral wellbore.
In one embodiment, an assembly for forming a lateral wellbore includes a mill having a bore and a plurality of blades; a whipstock having an inclined surface for guiding movement of the mill, the mill releasably connected to the whipstock; and a tubing disposed in the bore of the mill and the whipstock. In one example, at least one of the plurality of blades is disposed in a slot formed in the whipstock.
In another embodiment, an assembly for forming a lateral wellbore includes a mill having a bore and a plurality of blades and a lug; a whipstock having an inclined surface for guiding movement of the mill and a lug, the mill releasably connected to the whipstock; and a tubing disposed in the bore of the mill and the whipstock, wherein the lug of the mill is engageable with the lug of the whipstock and configured to apply a downward force to lug of the whipstock.
In one or more of the embodiments described herein, the at least one blade is configured to transfer torque to the whipstock when the at least one blade is disposed in the slot.
In one or more of the embodiments described herein, two blades are in disposed in a respective slot formed in the whipstock for each blade.
In one or more of the embodiments described herein, a clearance between a first blade in a first slot is smaller than a clearance between a second blade and a second slot.
In one or more of the embodiments described herein, the mill includes a lug engaged with a lug of the whipstock for transfer of an axial force.
In one or more of the embodiments described herein, a sealing member disposed between the tubing and the bore of the mill.
In one or more of the embodiments described herein, the slot is formed in an attachment section having a flat upper surface.
In one or more of the embodiments described herein, the bore includes an inlet, an angled passage and an offset passage.
In one or more of the embodiments described herein, the tubing is disposed in the offset passage.
In one or more of the embodiments described herein, a central axis of the offset passage is located above a central axis of the inlet when the mill 150 is attached to the whipstock.
In one or more of the embodiments described herein, the tubing is configured to supply fluid to a location below the whipstock.
In one or more of the embodiments described herein, a shearable member releasably connecting the mill and the whipstock.
In one or more of the embodiments described herein, the whipstock includes an opening for receiving the shearable member, and a clearance exists between the shearable member and a wall of the opening.
In one or more of the embodiments described herein, the mill is movable relative to the tubing upon release of the mill from the whipstock.
In another embodiment, a method for forming a lateral wellbore in a wellbore includes lowering a work string having a drilling member releasably attached to a whipstock, and a tubing connected between the mill and the whipstock. The drilling member includes a blade disposed in slot of the whipstock. The method also includes supplying a fluid through the drilling member and the tubing to a location below the whipstock; releasing the drilling member from the whipstock; and moving the drilling member along an inclined surface of the whipstock to form at least a portion of the lateral wellbore.
In one or more of the embodiments described herein, the method includes rotating the mill and transferring torque from the mill to the whipstock via the blade and the slot.
In one or more of the embodiments described herein, the mill includes a first lug and the whipstock includes a second lug, and the method further comprises transferring axial force from the first lug of the mill to the second lug of the whipstock.
In one or more of the embodiments described herein, releasing the drilling member comprises applying a tension force on the drilling member to break a shearable member.
In one or more of the embodiments described herein, supplying cement comprises supplying cement through an angled bore of the mill.
In one or more of the embodiments described herein, moving the drilling member along an inclined surface comprises milling the tubing.
In one or more of the embodiments described herein, the method includes lowering a second drilling member to extend the lateral wellbore.
In one or more of the embodiments described herein, the method includes supplying cement to inflate a packer attached to the whipstock
In one or more of the embodiments described herein, the assembly includes a sealing member disposed between the tubing and the bore of the mill.
In one or more of the embodiments described herein, at least two blades are disposed in a respective slot formed in the whipstock for each blade.
In one or more of the embodiments described herein, the at least two blades are configured to transfer torque to the whipstock when the at least two blades are disposed in the slots.
In one or more of the embodiments described herein, a clearance between a first blade in a first slot is smaller than a clearance between a second blade and a second slot.
In one or more of the embodiments described herein, wherein the location is in a downhole tool.
In one or more of the embodiments described herein, the method includes moving an actuating device through the mill and the tubing.
In one or more of the embodiments described herein, the method includes shifting a sleeve to open a port in the downhole tool.
In one or more of the embodiments described herein, wherein the fluid is selected from the group consisting of cement, drilling fluid, and completion fluid.
In one or more of the embodiments described herein, wherein the downhole tool comprises a packer, and the method includes inflating the packer.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
