Patent Description:
Moreover, this sequential approach to constructing a well may face additional problems, e.g., in mature fields where formation pressure depletion causes increased challenges such as hole instability, lost circulation zones, salt creeping, and stuck pipe events. Unsurprisingly, mature fields routinely generate the highest amounts of non-productive time (NPT) during the drilling process, in many cases rendering access to the remaining reserves economically infeasible. The sequential approach may also be inadequate to the challenges created by a customer's field development plans having complex well trajectories with narrow mud windows through unstable formations.

<CIT> provides a method of forming a wellbore which includes conveying an inner string and an outer string downhole; attaching the inner string to the outer string at a first location and forming the wellbore; and attaching the inner string to the outer string at a second location uphole of the first location and cementing an annulus between the outer string and the wellbore, without retrieving the inner string from the wellbore.

<CIT> provides a well bore drilling system and method which utilizes independently deployable multiple tubular strings to drill, line and cement multiple hole sections without intervening trips to the surface.

The invention relates to a casing while drilling system as set out in independent claim <NUM> and a casing while drilling method as set out in independent claim <NUM>. Optional features are described in the dependent claims.

Accordingly, there are disclosed herein certain latchable casing while drilling (CWD) systems and methods. In the following detailed description of the various disclosed embodiments, reference will be made to the accompanying drawings in which:.

It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.

Certain terms are used throughout the following description and claims to refer to particular system components and configurations. As one skilled in the art will appreciate, companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms "including" and "comprising" are used in an openended fashion, and thus should be interpreted to mean "including, but not limited to. Also, the term "couple" or "couples" is intended to mean either an indirect or a direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. In addition, the term "attached" is intended to mean either an indirect or a direct physical connection. Thus, if a first device attaches to a second device, that connection may be through a direct physical connection, or through an indirect physical connection via other devices and connections.

The issues identified in the background are at least partly addressed by systems and methods for latchable casing while drilling. The disclosed systems and methods are best understood in the context of the environment in which they operate. Accordingly, <FIG> shows an illustrative drilling environment. A drilling platform <NUM> supports a derrick <NUM> having a traveling block <NUM> for raising and lowering a bottomhole assembly (BHA) <NUM>. The platform <NUM> may also be located offshore for subsea drilling purposes in at least one embodiment. The BHA <NUM> may include one or more of a rotary steerable system, logging while drilling system, and downhole motor <NUM>, and includes a drill bit <NUM> and a reamer <NUM>. A top drive <NUM> supports and rotates the BHA <NUM> as it is lowered through the wellhead <NUM>. The drill bit <NUM> and reamer <NUM> may also be driven by the downhole motor <NUM>. As the drill bit <NUM> and reamer <NUM> rotate, they create a borehole <NUM> that passes through various formations <NUM>. The reamer <NUM> may be an underreamer, a winged reamer, or the like, and the reamer <NUM> has extendable cutters that, when extended, enlarge the borehole to accommodate the casing <NUM>. The cutters can be retracted to enable the drilling assembly to pass through the interior of the casing at a later stage.

A pump <NUM> circulates drilling fluid <NUM> through a feed pipe <NUM>, through the interior of the drill string to the drill bit <NUM>. The fluid exits through orifices in the drill bit <NUM> and flows upward to transport drill cuttings to the surface where the fluid is filtered and recirculated.

<FIG> illustrates a portion of the casing <NUM> including a latch apparatus <NUM> that is used during the drilling operations illustrated in <FIG>. The latch apparatus <NUM> includes a tubular member <NUM> with two ends <NUM>, <NUM> that may be coupled to other portions of the casing <NUM> via the mating of grooves or threads thus making the latch apparatus <NUM> part of the casing string, and the latch apparatus <NUM> may be made of any suitable casing material. The latch apparatus <NUM> also includes latch landings S1, S2, S3.

A latch landing, e.g. S1, may include one or more specially configured recesses formed along the interior surface of the latch apparatus <NUM> that are designed to align with and receive movable, spring loaded, latches extending radially from one or more downhole tools such as the BHA <NUM> and cement valves. For example, as illustrated, latch landing S1 includes two vertically-spaced recesses. The vertical spacing between recesses may be unique to prevent latches designed for other latch landings, e.g. latches designed for S2, from engaging with a particular latch landing, e.g. S1. In at least one embodiment, a unique horizontal spacing may be used for similar reasons. When the latches are properly aligned with the appropriate latch landing in the latch apparatus <NUM>, the spring loading on the latches forces the latches to move radially outwardly into the recesses. When successfully engaged, the latches and latch landings anchor the downhole tool (e.g. BHA <NUM> or cement valves) to the casing <NUM>.

The latch apparatus <NUM> may include more than one latch landing, e.g. S1, S2, S3. Each latch landing S1, S2, S3 may have a unique position and spacing between recesses relative to any other latch landing S1, S2, S3. As such, each latch landing S1, S2, S3 may be unique to a particular downhole tool or set of downhole tools with corresponding latches.

A downhole tool such as a BHA <NUM> may be moved past any set of latch landings S1, S2, S3 without engaging the latch landings S1, S2, S3 by rotating the downhole tool so that the latches are not aligned with corresponding latch landings S1, S2, S3 as they traverse the latch apparatus <NUM>. Similarly, the casing <NUM> including the latch landings S1, S2, S3 may be prevented from engaging any downhole tool by rotating the casing so that the latch landings S1, S2, S3 are not aligned with corresponding latches as they traverse the downhole tool.

When the BHA <NUM> has been engaged with the latch apparatus <NUM>, a non-rotational upward force on the BHA <NUM> (or converse downward force on the casing <NUM>) causes release of the BHA <NUM> from the latch apparatus <NUM>. The upward movement of the BHA <NUM> may be permitted by tapered upper shoulders between latches on the BHA <NUM> and the latch landings S1, S2, S3. While engaged, downward movement of the BHA <NUM> (or upward movement of the casing <NUM>) may be prevented by square lower shoulders between latches on the BHA <NUM> and the latch landings S1, S2, S3. The amount of force required to release the BHA <NUM> may be altered as desired by adjusting the spring tension acting to extend the latches outward or by altering the surface contact areas between the latches and latch landings S1, S2, S3. For clarity, further embodiments will be described with two latch apparatuses <NUM>. However, any number of axially-separated latch apparatuses <NUM> may be included in the casing <NUM> for greater flexibility in positioning the casing <NUM> and downhole tool to decrease the number of trips.

<FIG> illustrate a method <NUM> of casing while drilling using two latch apparatuses. <FIG> is a flowchart beginning at <NUM> and ending at <NUM>, and <FIG> are cross-sectional views of the borehole <NUM>, which will be discussed in parallel with <FIG>. At <NUM> and <FIG>, a borehole <NUM> is extended past casing <NUM> that has been previously cemented. The borehole <NUM> is extended by using the drill bit <NUM> to drill through the formation <NUM> below the cemented casing <NUM> as described above.

At <NUM> and <FIG>, the drillstring and BHA are removed from the borehole <NUM>, and a section of casing <NUM> including an upper latch apparatus <NUM> and a lower latch apparatus <NUM> is inserted into the borehole <NUM>. The casing <NUM> may include any number of latch apparatuses in various embodiments. The casing <NUM> may be assembled before insertion by coupling the lower latch apparatus <NUM> to one or more sections of casing at both ends. Next, the upper latch apparatus <NUM> may be coupled to the casing string. The distance between the upper <NUM> and lower <NUM> latch apparatus may be approximately the length of the BHA. The distance may also be such that the drill bit and reamer stick out past the bottom of the casing <NUM> when the BHA is engaged with the upper <NUM> or lower <NUM> latch apparatus in various embodiments.

At <NUM> and <FIG>, the inserted casing <NUM> may be secured within casing slips <NUM>. Next, the BHA <NUM> is assembled, inserted into the borehole <NUM>, moved past the upper latch apparatus <NUM>, and latched to the lower latch apparatus <NUM> as described above. Next as shown in <FIG>, with the BHA <NUM> secured and supported by the casing <NUM>, the drillstring or wireline used to lower the BHA <NUM> into the borehole <NUM> is uncoupled from the BHA <NUM> and removed from the borehole <NUM>. If desired, more sections of casing may be added to the top of the casing string.

At <NUM> and <FIG>, the borehole <NUM> is extended using the casing-supported BHA <NUM>. If desired, the reamer <NUM> is extended and activated when clear of the previously cemented casing. The borehole <NUM> may be extended until total depth (TD) is reached, or the BHA <NUM> may be serviced or replaced before TD is reached if necessary.

At <NUM> and <FIG>, the BHA <NUM> may be serviced or replaced in at least one example. Turning to <FIG>, a drillstring or wireline may be coupled to the BHA <NUM> and used to unlatch the BHA <NUM> from the casing <NUM>, specifically the lower latch apparatus <NUM>, as described above. Next, the BHA <NUM> may be removed from the borehole <NUM> for servicing or replacement. Turning to <FIG>, the serviced or replacement BHA <NUM> is inserted into the borehole <NUM> via drillstring or wireline, moved past the upper latch apparatus <NUM>, and latched to the lower latch apparatus <NUM>.

A sealing assembly may also be implemented. For example, packer cups may circulate down throughout the bore of the BHA <NUM> and drill bit. When the BHA <NUM> is retrieved with drillpipe, the drillstring may include a packer, in case of a well kick, able to close the annulus between the retrieval string and the casing. The packer may be a full-opening, hookwall packer used for testing, treating, and squeeze cementing operations. The packer body may include a J-slot mechanism, mechanical slips, packer elements, and hydraulic slips. Large, heavy-duty slips in the hydraulic hold-down mechanism help prevent the packer from being pumped up the hole.

At <NUM> and <FIG>, the drillstring or wireline may be uncoupled from the BHA <NUM>, and the borehole <NUM> may be extended until TD is reached by the casing-supported BHA <NUM>. At <NUM>, the rat hole is enlarged as explained with reference to <FIG>, and at <NUM>, cementing is performed as explained with reference to <FIG>.

Turning to <FIG>, a system <NUM> and method for enlarging a rat hole <NUM> using latching with casing and resting within the borehole are disclosed. First, the borehole <NUM> is drilled to the desired final depth, or total depth (TD). The rat hole <NUM> is the hole below the TD that has a smaller diameter than the casing <NUM>. Next, the BHA <NUM> is repositioned such that the BHA reamer arms rest within the large-diameter portion of the borehole <NUM>. As illustrated, resting the BHA <NUM> includes resting an extended reamer <NUM> of the BHA <NUM> on a top edge of the rat hole <NUM>. Next, the casing <NUM> is moved relative to the resting BHA <NUM>. When the casing is engaged with the BHA at the lower latch apparatus <NUM>, moving the casing downward disengages the BHA <NUM>. Further downward movement of the casing <NUM>, and rotation of the casing <NUM> if necessary, causes the casing <NUM> to engage with the BHA <NUM> at the upper latch apparatus <NUM>.

Next, turning to <FIG>, the rat hole <NUM> is enlarged at the depth drilling and reaming such that an area <NUM> underneath the TD is the close to the circumference of the borehole <NUM> rather than the circumference of the un-enlarged rat hole <NUM>. The enlargement of the rat hole <NUM> is performed while the BHA <NUM> is engaged with the upper latch apparatus <NUM>. By enlarging the rat hole <NUM>, the casing <NUM> may be positioned below the TD during the cementing process rather than as much as <NUM> feet above the TD. As such, the integrity of the surrounding earth formation may be increased.

Turning to <FIG>, an alternative system <NUM> and method, not falling within the scope of the claimed invention, for enlarging a rat hole <NUM> using latching with casing and the lower latch apparatus are disclosed. First, the BHA <NUM> remains engaged with the lower latch apparatus <NUM>. Next, the reamer <NUM> is activated to enlarge the rat hole <NUM> such that the circumference of the rat hole <NUM> at a particular depth is close to the circumference of the borehole <NUM> at that depth. Next, the casing <NUM> is secured within a slip. Next, the BHA <NUM> is disengaged from the lower latch apparatus <NUM>, and removed from the borehole <NUM> via wireline or drillstring. Finally, the casing <NUM> is moved downwards such that the casing <NUM> surrounds the borehole <NUM> at the depth of the enlarged rat hole. As such, the integrity of the surrounding earth formation may be increased during the cementing process.

Turning to <FIG>, another alternative system <NUM> and method, not falling within the scope of the claimed invention, for enlarging a rat hole <NUM> using latching with casing and the casing bit are disclosed. First, the BHA <NUM> is repositioned within the casing <NUM> to the upper latch apparatus <NUM>. Next, a casing bit <NUM> is used to enlarge the rat hole <NUM>. The casing bit <NUM> is a special reamer located at the end of the casing <NUM>. In at least one embodiment, the casing bit <NUM> includes mating threads on the bottom section of casing. By pushing the casing <NUM> downwards, and rotating if necessary, the casing bit <NUM> enlarges the rat hole <NUM>. Such an embodiment is useful if a conventional reamer fails, is not available, or is too expensive to deploy. By repositioning the BHA <NUM> within the borehole <NUM>, instead of removing the BHA <NUM> from the borehole <NUM>, multiple trips may be avoided. Also, by enlarging the rat hole <NUM>, the integrity of the surrounding earth formation may be increased during the cementing process.

Turning to <FIG>, a system <NUM> and method for enlarging a rat hole using latching with casing and a wireline are disclosed. First, the casing <NUM> is secured in a slip <NUM>. Next, a wireline <NUM>, or similar running tool, is inserted into the borehole <NUM> to engage with the BHA <NUM>. Next, the wireline <NUM> is used to reposition the BHA <NUM> from the lower latch apparatus <NUM> to the upper latch apparatus <NUM>. Next, turning to <FIG>, with the BHA <NUM> engaged with the upper latch apparatus <NUM>, the reamer <NUM> (not extended) is lowered toward the rat hole <NUM>. Next, the reamer <NUM> is extended, and the rat hole <NUM> is enlarged by the reamer <NUM>. After, the rat hole <NUM> has been enlarged, the BHA <NUM> may be removed from the borehole <NUM> and the cementing process may be performed, e.g. as illustrated in <FIG>, with the casing <NUM> at the depth of the previously un-enlarged rat hole. As such, the integrity of the surrounding earth formation may be increased during the cementing process.

Turning to <FIG>, a system <NUM> includes a lower latch apparatus <NUM> that includes a BHA latch landing (e.g. S1) and cement valve latch landing (e.g. S2). The system <NUM> also includes an upper latch apparatus <NUM> that includes a BHA latch landing (e.g. S1) and cement valve latch landing as well. In at least one embodiment, the cement valve latch landing in the upper apparatus <NUM> is different (e.g. S3) from the cement valve latch landing in the lower apparatus <NUM> (e.g. S2). In an alternative embodiment, both cement valve latch landings are the same (e.g. both are in the position of S2 on their respective latch apparatus). The borehole <NUM> includes a short section not enlarged, which is a hole <NUM> smaller in diameter than the borehole <NUM> located at the end of the borehole <NUM>.

First, a cement valve <NUM> is inserted into the borehole <NUM>. The cement valve bypasses the upper latch apparatus <NUM> by either not being rotated to engage the upper latch apparatus <NUM> or by not having any latches that are configured to engage the upper latch apparatus <NUM>. Next, the cement valve <NUM> engages the lower latch apparatus <NUM>. Next, another cement valve <NUM> is inserted into the borehole <NUM>. Turning to <FIG>, the second cement valve <NUM> engages the upper latch apparatus <NUM>. With both cement valves <NUM>, <NUM> in place, cement <NUM> is inserted into the borehole <NUM>. The valves allow the cement to flow only downhole through the valves. Next, drilling fluid <NUM> and a displacement plug <NUM> are inserted into the borehole <NUM>. Turning to <FIG>, the displacement plug <NUM> lands on the upper cement valve <NUM>. Should any cement <NUM> be contaminated, the contaminated cement will be contained inside the casing <NUM> where it will be eliminated during drilling. No contaminated cement will enter the annulus between the casing <NUM> and borehole <NUM>.

A casing while drilling system includes a casing string including an upper latch apparatus and a lower latch apparatus. The system also includes a bottom hole assembly (BHA) latched into the lower latch apparatus for steerable drilling, the BHA configured to latch into the upper latch apparatus for enlarging a rat hole.

A majority of the BHA, when latched into the upper latch apparatus, may be surrounded by the casing string. The BHA may be repositioned either from the upper latch apparatus to the lower latch apparatus or from the lower latch apparatus to the upper latch apparatus both without exiting a borehole. The distance between the lower latch apparatus and the upper latch apparatus is not greater than the length of the BHA. The lower latch apparatus may include a lower BHA latch landing, and the upper latch apparatus may include an upper BHA latch landing. The lower latch apparatus may also include a lower cement valve latch landing, and the upper latch apparatus may also include an upper cement valve latch landing. A cement valve capable of latching into the lower latch apparatus is not capable of latching into the upper latch apparatus. A cement valve capable of latching into the upper latch apparatus is not capable of latching into the lower latch apparatus. In another embodiment, a cement valve capable of latching into the lower latch apparatus may be capable of latching into the upper latch apparatus.

A casing while drilling method includes assembling a casing string including an upper latch apparatus and a lower latch apparatus. The method also includes latching a steerable BHA into the lower latch apparatus. The method also includes steering the casing string along a trajectory to a total depth. The method also includes repositioning the BHA to latch into the upper latch apparatus. The method also includes enlarging a rat hole at or under the total depth.

Enlarging the rat hole may include using a casing bit coupled to the casing to enlarge the rat hole. Repositioning the BHA may include using a wireline to reposition the BHA from the lower latch apparatus to the upper latch apparatus. Repositioning the BHA may include resting the BHA within a borehole and moving the casing string relative to the resting BHA. Resting the BHA may include resting a reamer of the BHA on a top edge of the rat hole. Enlarging the rat hole includes using a reamer to enlarge the rat hole. The method may also include removing the BHA from a borehole and cementing the casing at the total depth.

A cementing method may include assembling a casing string including an upper latch apparatus and a lower latch apparatus. The method also includes positioning the casing string within a borehole. The method also includes latching a cement valve into the lower latch apparatus. The method also includes latching a second cement valve into the upper latch apparatus. The method also includes injecting cement through the casing string into an annulus.

The method may also include inserting a displacement plug, or cement float, into the borehole, the displacement plug configured to displace cement through the second cement valve.

A well prepared for cementing includes a casing string including an upper latch apparatus and a lower latch apparatus. The well also includes a cement valve latched into the lower latch apparatus. The well also includes a second cement valve latched into the upper latch apparatus.

Claim 1:
A casing while drilling system (<NUM>), comprising:
a casing string (<NUM>) comprising:
an upper latch apparatus (<NUM>); and
a lower latch apparatus (<NUM>); and
a bottom hole assembly (BHA) (<NUM>), wherein the BHA (<NUM>) comprises a drill bit (<NUM>) and a reamer (<NUM>), wherein the reamer (<NUM>) has extendable cutters, and wherein the BHA (<NUM>) is latched into the lower latch apparatus (<NUM>) for steerable drilling, characterised in that the BHA (<NUM>) is configured to latch into the upper latch apparatus (<NUM>) for enlarging a rat hole (<NUM>) using the reamer (<NUM>).