Patent Description:
As a preventative measure or as a remedy, it is thus generally known to deploy lost circulation material (LCM) into a wellbore from the surface, for a purpose inhibiting the loss of drilling fluid (often referred to as "mud") into physically vulnerable parts of a wellbore such as fractures or highly permeable formations. Typically, LCM objects may assume a variety of sizes and shapes (e.g., granular shapes) and are added to the mud at a surface location for circulation downhole, through the piping of a drill string. Then, in the return flow of mud to the surface location from the downhole distal end of the drill string (e.g., from where a drill head is located), typically through an annular volumetric space between the external surfaces of the drill string and the interior surface of the wellbore, the objects effectively "plug" the noted vulnerable portions or inhibit the possibility of mud flow into such portions. Some common examples of LCM objects include tree bark, shredded cane stalks, pieces of plastic or cellophane, or ground material such as ground limestone or marble, wood, corn cobs and cotton hulls.

Conventionally, a variety of LCM types and related loss curing systems have been conceived of, developed and implemented, yet there are often physical limitations presented in their deployment. Particularly, conventional LCM deployment techniques are often not conducive to effectively circulating larger-scale LCM objects (also referred to herein as "large LCM objects"), thus often limiting the size of such objects that may be used. Such larger objects are often employed for "severe" or "total" lost circulation scenarios (e.g., losses greater than <NUM> barrels per hour), where significant wellbore irregularities or vulnerabilities cause a significant loss of drilling fluid if left untreated. As such, large LCM objects (particles or shapes of materials with sizes greater than <NUM> in diameter) cannot typically be passed through standard mud pumps (that pump mud or drilling fluid downhole via the drill string and uphole via the aforementioned annulus), as the pumps might easily destroy or break the particles down. Another concern may be encountered with harder LCM objects, which could cause damage to the pumps themselves.

<CIT> discloses a method of plugging a formation fracture that includes drilling, with a drill string configured to flow drilling fluid, a wellbore, where, at a downhole location, the drilling fluid is lost through a formation fracture. The method also includes deploying, through the drill string, a plugging assembly to the downhole location of the wellbore. The plugging assembly includes a flexible fiber sheet releasably coupled to a pumpable dart such that when the plugging assembly reaches the downhole location, the flexible fiber sheet is released from the dart to flow, with the drilling fluid, to the formation fracture to at least partially overlay the formation fracture. The method also includes adding, to the drilling fluid, lost circulation material configured to accumulate on a portion of the flexible fiber sheet to at least partially fluidically plug the formation fracture.

<CIT> discloses a completion pipe comprising a plug arrangement and a method for arranging a completion pipe in a well. The arrangement includes a disintegratable plug element arranged in a plug housing in a pipe string, a seal element arranged to seal between the plug element and the pipe string. The plug element is movable in the axial direction of the pipe string between a first position and a second position.

<CIT> discloses a drilling system that includes a downhole well control device that can be used to control out-of-norm wellbore conditions. The downhole well control device can control one or more selected fluid parameters. The well control device in cooperation or independent of surface devices exerts control over one or more drilling or formation parameters to manage an out-of-norm wellbore condition. An exemplary well control device hydraulically isolates one or more sections of a wellbore by selectively blocking fluid flow in a pipe bore and an annulus. The control device also selectively flows fluid from the pipe bore to the annulus. A communication device provides on-way or bi¬ directional signal and / or data transfer between the controller(s), surface personnel and the well control device. Exemplary application of the well control device include controlling a well kick, controlling drilling fluid being lost to the formation and controlling a simultaneous kick and loss.

In one aspect, embodiments disclosed herein relate to a method that includes providing one or more drill pipe segments and disposing a quantity of lost circulation material objects within the one or more drill pipe segments. A retention element is provided to retain the lost circulation material objects within the one or more drill pipe segments. The one or more drill pipe segments are connected to a drill string at a wellbore, and drilling fluid is flowed through the drill string. The flowing of drilling fluid through the drill string causes the retention element to release the lost circulation material objects to propagate further.

In one aspect, embodiments disclosed herein relate to an apparatus for deploying lost circulation material objects into a wellbore. The apparatus includes one or more drill pipe segments, a quantity of lost circulation material objects disposed within the one or more drill pipe segments and a retention element that retains the lost circulation material objects within the one or more drill pipe segments. The retention element is configured to, in response to flowing of drilling fluid through the one or more drill pipe segments, release the lost circulation material objects to propagate further.

Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

Specific embodiments of the disclosed technology will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency.

The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms "before", "after", "single", and other such terminology.

Broadly contemplated herein, in accordance with one or more embodiments, are methods and apparatus for deploying into a wellbore large LCM objects (e.g., greater than <NUM> in diameter, and where a majority of the objects are so sized) that would be difficult to pass through equipment such as a conventional (e.g., centrifugal) charge pump or mud circulation pump (e.g., which may often be a positive displacement pump). Thus, the features broadly contemplated herein may be employed for deploying LCM objects that otherwise may become damaged by mechanisms in pumping systems or valve arrangements, or could potentially cause some damage to such mechanisms.

Turning now to the figures, to facilitate easier reference when describing <FIG>, reference numerals may be advanced by a multiple of <NUM> in indicating a similar or analogous component or element among <FIG>.

<FIG> schematically illustrates, in a general and cross-sectional elevational view, a well environment <NUM> of oil and gas extraction by way of general background and in accordance with one or more embodiments.

As illustrated, formation <NUM> may include a porous or fractured rock formation that resides underground, beneath the surface <NUM> of the Earth. The surface <NUM> may be dry land or ocean bottom. The well system <NUM> may be for a hydrocarbon well, such as an oil well, a gas well, a gas condensate well, or a mixture of hydrocarbon-bearing fluids. The formation <NUM> may include different layers of rock having varying characteristics, such as degrees of density, permeability, porosity, and fluid saturations. The formation <NUM> may include a low-pressure formation (for example, a gas-depleted former hydrocarbon-bearing formation) and a water-bearing formation (for example, fresh water, brine, former waterflood). In the case of the well system <NUM> being operated as a production well, the well system <NUM> may facilitate the extraction of hydrocarbons (or "production") from a hydrocarbon-bearing formation. In the case of the well system <NUM> being operated as an injection well, the well system <NUM> may facilitate the injection of substances, such as gas or water, into a hydrocarbon-bearing formation.

The well system <NUM> may include a wellbore <NUM> and a drilling system <NUM>. "Wellbore" may also be referred to as a "subterranean wellbore". The wellbore <NUM> may include a bored hole that extends from the surface <NUM> into the formation <NUM>. Wellbore <NUM> is defined by wellbore wall <NUM>, generally cylindrical in shape. Although shown as a completely vertical well, the path of wellbore <NUM> may alter to assume a deviated (sloped) or horizontal configuration, starting from a predetermined subsurface location.

The wellbore <NUM> may be created, for example, by the drilling system <NUM> boring through the formation <NUM>. The drilling system <NUM> may include a drilling rig <NUM> and a drill string <NUM>. The drill string <NUM> may include a drill pipe <NUM> and a bottom hole assembly (BHA) <NUM> which may include a drill bit <NUM>. The BHA may also include drill collars, stabilizers and reamers. In accordance with a working example, the drill bit <NUM> includes a cutting drill bit having rotating teeth that can bore through the formation <NUM> to create the wellbore <NUM>.

The wellbore <NUM> may provide for the circulation of "drilling fluids" or "drilling mud" (or simply "mud") <NUM> during drilling operations using a mud circulation system <NUM>. The terms "drilling fluid", "drilling mud" and "mud" refer to fluids, slurries, or muds used in drilling operations downhole, such as during the formation of the wellbore.

Drilling fluid <NUM> flows downhole through the drill string <NUM>, out of the drill bit <NUM> (thus cooling the drill bit <NUM> from the heat of friction generated from cutting action against the face of the wellbore <NUM>), and back uphole through an annular chamber defined between the drill string <NUM> and the wellbore wall <NUM> of the wellbore <NUM>, carrying cuttings and other debris from the bottom of the wellbore <NUM>. Upon reaching the surface <NUM>, the drilling fluid <NUM> may pass through a drilling fluid return line <NUM> into a drilling fluid receiving tank <NUM>, where the cuttings are separated from the drilling fluid <NUM>. In the drilling fluid receiving tank <NUM>, the drilling fluid <NUM> is agitated (e.g., via mud cleaning equipment or a shale shaker such as that indicated at <NUM> in <FIG>), such that it releases any dissolved gases from the drilling fluid <NUM>. The drilling fluid <NUM> is then passed to a drilling fluid storage tank and associated mud pump (jointly indicated at <NUM>); the fluid <NUM> thus is held there until it is pumped back to the drill string <NUM> via a standpipe <NUM> and then back downhole once again.

Lost circulation, or loss of circulation, is said to have occurred when the drilling fluid <NUM> flows into formation <NUM> through fractures <NUM> (or other structural irregularities or anomalies) instead of returning up the aforementioned annulus. In the present disclosure, "fractures" may refer to as naturally occurring opening or fissure in the formation, fissures created by the drilling activities, or any other features of the formation in the vicinity of the wellbore which allow the migration of the drilling fluid into the formation. The general location where the fluid is being lost into the formation <NUM> may be referred to as a lost circulation zone <NUM>. The lost circulation zone <NUM> of the embodiment illustrated in <FIG> is located in the bottom portion of the wellbore <NUM>. However, lost circulation may occur at any location in the wellbore <NUM> between the surface <NUM> and the bottom of the wellbore <NUM> and thus, any parts of the wellbore <NUM> where lost circulation is occurring may be considered as the lost circulation zone (or zones) <NUM>. Lost circulation may be classified under different categories based on the amount of drilling fluid being lost and may include: "seepage"; "partial lost returns" (or "partial loss", or "partial lost circulation"); "severe lost returns" (or "severe loss", or "severe lost circulation"); and "total lost returns" (or "total loss", or "total lost circulation).

The disclosure now turns to working examples of a system and method in accordance with one or more embodiments, as described and illustrated with respect to <FIG>. It should be understood and appreciated that these merely represent illustrative examples, and that a great variety of possible implementations are conceivable within the scope of embodiments as broadly contemplated herein.

In accordance with one or more embodiments, <FIG> schematically illustrates a conventional system for circulating drilling fluid (or "mud"), in which methods and apparatus for the deployment of large LCM objects as broadly contemplated herein may be employed. As illustrated, the downhole propagation of drilling fluid is indicated with arrows oriented in a general direction between mud pump <NUM> (with an incorporated drilling fluid storage tank) and drill bit <NUM>, and its return flow is indicated with arrows oriented in a general direction between drill bit <NUM> and mud pump <NUM>. As such, while a mud tank or pit <NUM> (or "drilling fluid receiving tank") stores drilling fluid that is initially provided or has been recirculated, mud pump <NUM> (in fluid communication therewith) pumps the drilling fluid onward through a pump discharge line <NUM>, standpipe <NUM> and rotary hose <NUM>.

As generally is known, and in accordance with one or more embodiments, different arrangements may be provided for providing torque to rotationally drive a drill string (and thus drill bit <NUM>); two alternatives are indicated generally at <NUM> in <FIG>. Thus, the rotary hose <NUM> may feed into (or through) a top drive 254a which itself provides torque to the drill string in order to drill a borehole. As also is generally known, a kelly drive 254b may be provided as an alternative to a top drive 254a. Such an arrangement uses a section of pipe with a polygonal or splined outer surface, which passes through a matching bushing and rotary table; the bushing is then rotated via the rotary table to also rotate the drill string.

In accordance with one or more embodiments, the drill string (as generally known) includes segments of drill pipe <NUM> that are axially connected to one another (e.g., via suitable male and female threading at respective axial ends of each segment). Interconnected segments of drill pipe <NUM> are disposed to rotate within wellbore <NUM>, to rotationally drive the drill bit <NUM> via transferring torque thereto. As such, while drilling fluid supplied by pump (and tank) <NUM> propagates through drill pipe <NUM> toward the drill bit <NUM> (generally downwardly) as shown, it returns (generally upwardly) through an annulus <NUM> defined between the drill pipe <NUM> and inner wall of the wellbore <NUM>, also via pumping by the pump <NUM>. In the process, the drilling fluid then returns to receiving tank <NUM> via mud return line <NUM>, and via mud cleaning equipment or shale shaker <NUM>.

By way of further background in accordance with one or more embodiments, LCM objects are normally introduced into the drilling fluid flow so as to propagate downhole through the segments of drill pipe <NUM> and uphole through the annulus <NUM>, to then become lodged into the structural anomalies of one or more lost circulation zones (e.g., as indicated at <NUM> in <FIG>) to prevent or mitigate any further loss of drilling fluid to such anomalies.

As such, by way of additional background in accordance with one or more embodiments, the-grey shaded area in <FIG> represents that greatly restricted portion of the mud (drilling fluid) circulation system where large LCM objects (such as custom "severe" or "total" LCM objects) would need to be introduced in order to avert the risk of their damage by the pump <NUM>, or of damaging the pump <NUM> itself. Thus, the noted area is between the mud pump <NUM> and the beginning of the downhole portion of the drill string. However, the introduction of large LCM objects into the drilling fluid flow within the grey-shaded region presents its own difficulties and challenges. Particularly, as this would represent the "high-pressure" side of the mud pump <NUM>, the inclusion of a suitable pressure-rated vessel and volume transfer system would be needed for safety reasons, adding considerable complexity and cost to the system.

In accordance with one or more embodiments, one or more drill pipe segments may be preconfigured to include a quantity of large LCM objects, to permit the introduction of such objects into the wellbore <NUM> outside of (and downhole from) the grey-shaded area in <FIG>, thus averting and obviating the difficulties and challenges noted above. Accordingly, <FIG> schematically illustrates, in cross-sectional elevational view, a segment <NUM> of drill pipe so configured. Essentially, this may be a conventional segment of drill pipe, with modifications, that can be added to a drill string along with other segments of drill pipe. Thus as shown, a quantity of large LCM objects <NUM> can be disposed in an interior portion defined within the drill pipe segment <NUM>, held therewithin by a plug <NUM> (itself, installed toward a lower or downhole distal end of the segment <NUM>). As discussed in more detail herebelow, the plug <NUM> may be temporary in its nature and implementation, e.g., formed from a dissolvable material.

In accordance with one or more embodiments, the preconfigured drill pipe segment <NUM> may be disposed essentially anywhere along the drill string as may be deemed suitable, including toward a lowermost end of the drill string (e.g., axially adjacent to a bottomhole assembly that includes a drill bit such as that indicated at <NUM> in <FIG>). Additionally, more than one preconfigured drill pipe segment <NUM>, each with its own plug <NUM>, may be included in the drill string.

As such, in accordance with one or more embodiments, one or more preconfigured drill pipe segments <NUM> may be added to the drill string essentially at any time deemed suitable. Thus, as lengths of drill pipe are continually added with deeper drilling of the well, one or more new preconfigured drill pipe segments <NUM> may be added right into the drill string when the circulation of drilling fluid stops, in essentially the same manner that standard drill pipe segments (without LCM objects contained therein) would be added. The one or more preconfigured drill pipe segments <NUM> thus serve as a type of pressure-rated "container" for the LCM objects, until the objects are flushed out from the drill pipe segment(s) <NUM> via the flow of drilling fluid when it restarts (and in a manner as variously described herein). The operators on-site can readily determine when the addition of one or more new preconfigured drill pipe segments <NUM> may be warranted, e.g., in response to detected drilling fluid losses during drilling. As such, the number of preconfigured drill pipe segments <NUM> added at any given time can be governed by a magnitude of detected drilling fluid losses and based on an understanding of a quantity of LCM objects that may need to be introduced in response.

In accordance with one or more embodiments, <FIG> provides essentially the same view as <FIG>, but showing the introduction of drilling fluid <NUM> into the interior of the drill pipe segment <NUM>. In this process, the LCM objects <NUM> are wetted, while the plug <NUM> may include perforations or throughholes, extending from one axial end of the plug <NUM> to the other, to permit the fluid <NUM> to flow therethrough.

As such, <FIG> provides essentially the same view as <FIG>, but showing the throughflow of LCM objects <NUM> through the drill pipe segment after dissolution of the plug <NUM>, in accordance with one or more embodiments. Thus, with the plug (not shown in <FIG>) fully dissolved, the quantity of LCM objects <NUM> now are able to propagate through the drill pipe segment <NUM> uninhibited.

In accordance with one or more embodiments, <FIG> shows the plug <NUM> and a portion of drill pipe segment <NUM> from <FIG> in a cross-sectional, isometric view. As shown, the plug <NUM> may be fixed within the interior of drill pipe segment <NUM> via a dissolvable adhesive <NUM>. <FIG> then shows essentially the same view as <FIG>, but with drilling fluid <NUM> progressing through perforations in the dissolvable plug <NUM> and large LCM objects <NUM> retained above the plug <NUM> (prior to the plug <NUM> dissolving).

In accordance with one or more embodiments, plug <NUM> may be formed from one or more rapidly dissolvable materials. A great variety of materials can be employed here, including several used extensively in the packaging industry. By way of illustrative and non-restrictive example, such materials can include starch, paper, wood pulp and polyvinyl alcohol (PVOH). They typically can be formed into solid objects, foamed objects, single strand fibers, woven cloth and other forms, and thus can readily be formed into a suitable shape for a dissolvable plug <NUM> as broadly contemplated herein. Further, while such a dissolvable plug <NUM> could be formed completely from one or more dissolvable materials, in accordance with at least one variant it could be formed from a dissolvable binder and small-particle powder, such that the overall structure collapses as soon as the binder dissolves.

In accordance with one or more embodiments, and as noted previously, the dissolvable plug <NUM> may be perforated with a plurality of throughholes or flow channels extending from one axial end of the plug <NUM> to the other; entry portions of such holes/channels are indicated generally at <NUM> in <FIG>, at an upper axial end of plug <NUM>. The holes or channels <NUM> may be suitably sized to permit at least some degree of throughflow of drilling fluid <NUM> while preventing the throughflow of LCM objects. Thus, and as appreciated further from <FIG>, the holes/channels <NUM> may be sized such that they are generally smaller than the smallest LCM objects being used, to permit at least some throughflow of drilling fluid <NUM> while the LCM objects <NUM> are retained axially above the plug <NUM> and are wetted by the drilling fluid <NUM>. By way of illustrative example, the flow channels could have any of a variety of geometric cross-sectional shapes, such as circular, triangular or rectangular. In accordance with one or more variant embodiments, a plug <NUM> may be formed without throughholes or channels (such as those indicated at <NUM>) and instead may be configured simply to break or fail mechanically, whereupon the plug (or fragments thereof) then dissolve as the plug (or its fragments) continue to flow downhole.

In accordance with one or more embodiments, a dissolvable plug may be installed within a drill string without an adhesive, e.g., via an interference fit or form fit. Accordingly, <FIG> illustrates a plug 564a, in isometric view, with a tapered external surface (from top to bottom in the drawing) and a pair of generally triangular flat indentations <NUM> recessed therein (one of which is visible in <FIG>). Also shown are entry portions of throughholes/channels 567a, at an upper axial end of plug 564a. By way of illustrative example, plug 564a may be positioned at an internal portion of a drill pipe segment, such as a drill pipe upset portion.

As an alternative, in accordance with one or more embodiments, <FIG> illustrates a plug 564b, in isometric view, that is generally cylindrical in shape. Here, plug 564b may include a number of slot-shaped channels 567b, extending from an upper axial end to a lower axial end of plug 564b. As shown, entry portions of such channels 567a may extend across the generally circular upper axial surface of plug 564b in the manner of a secant. In the present working example, some such channels 567a (here, alternate ones of them) extend only incompletely across the full lateral extent of the plug 564b, while a subset <NUM> of the channels 567a extend completely across the full lateral extent of the plug 564b. Plug 564b can be positioned, e.g., to sit on an internal taper of a drill pipe segment and can be sufficiently elastic in its formulation as to be fixed thereby as an interference fit.

As another alternative, in accordance with one or more embodiments, <FIG> jointly illustrate a plug 564c (in isometric view and cross-sectional isometric view, respectively), that is also generally cylindrical in shape. Here, plug 564c may include an upper disc-shaped cap portion <NUM>, and a lower generally cylindrical portion <NUM>. Upper portion <NUM> may include a latticework of structural portions which intersect and define therebetween triangular-shaped indentations 567c; these may be entry points to throughholes or channels as discussed herein or, in a variant embodiment, may be fully closed (and still subject to dissolution upon the introduction of drilling fluid). Lower portion <NUM>, for its part, may be structured with support elements as shown, which would be configured to break mechanically and then dissolve along with the rest of the plug 564c.

<FIG> illustrates, in a partly cross-sectional, isometric view, a first variant configuration of a drill pipe segment <NUM> and LCM object retention element <NUM> in accordance with one or more embodiments. Here, instead of a dissolvable plug, a LCM object retention element <NUM> may be embodied by an inflatable capsule (or "balloon" or "bag") <NUM> formed from a dissolvable material. Thus, capsule <NUM> may be generally pill-shaped as shown in <FIG>, sufficiently large to span the full inner diameter of the interior of drill pipe segment <NUM>, and formed from a thin, dissolvable material such as PVA (polyvinyl alcohol) film. Accordingly, in the configuration of <FIG>, drilling fluid propagating axially downwardly will wet the large LCM objects <NUM> and also push the same toward capsule <NUM> in a manner to rupture and disintegrate the capsule <NUM>, thus then permitting the free and uninhibited flow of LCM objects <NUM> through drill pipe segment <NUM>. By way of initial implementation, the capsule <NUM> may be inflated and then disposed within the drill pipe segment <NUM>.

<FIG> illustrates, in a partly cross-sectional, isometric view, a second variant configuration of a drill pipe segment <NUM> and LCM object retention elements in accordance with one or more embodiments. Here, drill pipe segment <NUM> may contain two quantities (762a and 762b) of large LCM objects that are disposed axially adjacent to one another and are each contained within sacks or membranes formed from a dissolvable material (772a and 772b, respectively). When drilling fluid then propagates into the drill pipe segment <NUM>, the containing sacks 772a/b then will dissolve and release the large LCM objects 762a/b to proceed (in a downward direction with respect to the drawing) freely and uninhibitedly through the drill pipe segment <NUM>. A non-restrictive example of a possible material for the sacks 772a/b is soluble yarn as commonly used in the textile industry, formed (for instance) as PVA fibers held together with soluble resins. By way of initial implementation, at least a portion of the large LCM objects being used (e.g., such as the quantities indicated at 772a and 772b) may be disposed within a sack (such as 772a and 772b), and the sack (such as 772a and 772b) may be disposed within the drill pipe segment <NUM>.

<FIG> schematically illustrates, in a cross-sectional elevational view, a configuration including a drill pipe segment <NUM> and a pup joint <NUM>, in accordance with one or more embodiments. (A "pup joint" may be understood to be a drill pipe segment of shorter or non-standard axial length that is used to help adjust the overall length of an assembled drill string to a precise, predetermined requirement. ) Here, the pup joint <NUM> is assembled end-to-end with the drill pipe segment <NUM>. A dissolvable plug <NUM> is installed in the pup joint <NUM> substantially as described elsewhere herein, and a quantity of large LCM objects <NUM> is then disposed behind the plug <NUM>, occupying an interior volumetric space defined jointly by the pup joint <NUM> and the drill pipe segment <NUM>.

<FIG> schematically illustrates, in a cross-sectional elevational view, a configuration including a drill pipe segment <NUM> that includes an intermediate axial portion of larger diameter, in accordance with one or more embodiments. As shown, drill pipe segment <NUM> may include upper and lower axial end portions (975a and 975b, respectively) that are configured and dimensioned similarly to a standard drill pipe segment. Between the upper and lower axial end portions 975a and 975b, progressing axially downwardly with respect to the drawing, the drill pipe segment <NUM> may then be embodied in three distinct portions: a first generally transition portion 976a, an intermediate portion 976b and a second transition portion 976c. The intermediate portion 976b may be generally cylindrical in shape but of a larger diameter than the upper and lower axial end portions (975a/b) of the drill pipe segment <NUM>. Thus, the transition portions 976a/c may be generally tapered (or frustoconical) in their external shape, to effectively transition between the larger diameter of the intermediate portion 976b and the smaller diameter of each of the axial end portions (975a/b), respectively.

It can thus be appreciated that, in accordance with one or more variant embodiments, drill pipe segment <NUM> can hold a larger quantity of large LCM objects <NUM> than a standard drill pipe segment, while a dissolvable plug <NUM> can be used of essentially the same size as in embodiments involving a standard drill pipe segment. It also may be advantageous to install the drill pipe segment <NUM> at a position in the wellbore that is closer to the surface location than other drill pipe segments, as the larger overall diameter of segment <NUM> will lend itself better to the likelihood of greater available clearance at such a position in the wellbore.

Additionally, in accordance with one or more embodiments, it should be understood that drill pipe segment <NUM> need not necessarily be included as a constituent portion of the actual drill string used for performing a drilling operation and thus may serve temporarily as a discharge vessel for large LCM objects <NUM>. In other words, it can be connected temporarily to the drill string at the surface, circulation of drilling fluid may then continue in order to flush out the large LCM objects <NUM>, and the segment <NUM> can then be disconnected. The segment <NUM> can still be as long as a standard drill pipe segment, but its diameter at intermediate portion 976b may then be considerably large, such that a significantly increased volume of LCM objects <NUM> (e.g., up to <NUM> times greater) can be held and then deployed into the drill string.

<FIG> schematically illustrates, in a partly cross-sectional elevational view, a configuration including a drill pipe segment with a safety cap, in accordance with one or more embodiments. Additionally, <FIG> schematically illustrates, in isometric view, the safety cap from <FIG>, in accordance with one or more embodiments. Reference may continue to be made to both <FIG> jointly.

As shown, a drill pipe segment <NUM> may include, at an axial end thereof, a safety cap <NUM>. As discussed elsewhere herein, the drill pipe segment <NUM> may be "pre-charged" and thus include therewithin a quantity of large LCM objects <NUM> and a dissolvable plug or analogous component. (The thicker vertical line segments indicated at <NUM> may be considered to represent the original location of a dissolvable plug that fails, which would then propagate downwardly toward safety cap <NUM>. The downward arrow indicating the presence of LCM objects <NUM> can likewise be understood to represent the downward propagation of such objects <NUM> subsequent to plug failure. ) The safety cap <NUM> may generally be in the form of a thread protector, that is, providing a known function of protecting internal or external threads of the pipe segment <NUM> during transportation and storage. The cap <NUM> may be formed from a lightweight load-bearing material such as aluminum or a metal composite. The cap <NUM> may also be color-coded for ready identification as a "pre-charged" drill pipe segment.

As such, in accordance with one or more embodiments, in the event of premature structural failure of the dissolvable plug (or other analogous component) inside, the plug (or other component) or the LCM objects <NUM> would move into an interior portion of the safety cap <NUM>, which then prevents the LCM objects <NUM> from discharging from the drill pipe segment <NUM> during handling. Additionally, one or more small windows <NUM> can be provided to permit a degree of observation (or permit viewing) into the interior of the safety cap <NUM>, to verify visually whether any LCM objects <NUM> or material from the plug (or other component) are disposed within the safety cap <NUM>. By way of example, two such windows <NUM> may recessed into the outer surface of safety cap <NUM> and disposed at diametrically opposite sides thereof. Each such window <NUM> may also be of any suitable shape (e.g., as a "plus sign" as shown) and include a transparent or translucent material to permit some degree of observation into the interior of safety cap <NUM>. If indeed it is verified that the plug or other component has structurally failed, the entire drill pipe segment <NUM>, with the safety cap <NUM> still on, can be laid aside for as long as may be desired.

In accordance with one or more embodiments, there are potentially a great variety of ways to implement the use of "pre-charged" drill pipe segments as broadly contemplated herein. By way of an illustrative example, two to four interconnected drill pipe segments may initially be so configured (i.e., "pre-charged"), and initially stored vertically in a rig derrick or mast; e.g., they may be interconnected wherein an axially lowermost drill pipe segment includes a dissolvable plug (or analogous component) as described and illustrated herein, and large LCM objects can be then occupy volumetric space above the plug (or other analogous component). Further, the LCM objects so disposed may extend into the interior volumetric space of more than one drill pipe segment. Accordingly, when the deployment of a volume of large LCM objects is warranted or desired, the interconnected drill pipe segments can be picked up, added to a running drill string, and run downhole as part of the overall drill string.

In accordance with one or more embodiments, as a possible refinement, a second dissolvable plug, configured similarly to the dissolvable plugs described and illustrated herein, may be placed at an upper axial end of a drill pipe segment, or of an interconnected series of drill pipe segments. This can help retain the large LCM objects within the drill pipe segment(s) even more readily, and thus can also dissolve when drilling fluid propagates through the drill string.

In accordance with one or more embodiments, depending on the operating context at hand, large LCM objects and dissolvable plugs (or analogous components) may be installed into drill pipe segments as they are laid out horizontally and individually on a pipe deck, below the rig floor level. In this scenario, any and all "pre-charged" drill pipe segments (or interconnected series of drill pipe segments) may be picked up to the rig floor level and either made up into longer stands (series of drill pipe segments) and set back in the derrick for possible later use (e.g., as a contingency in the event of severe lost circulation) or added directly to a drill string for immediate use (e.g., when lost circulation may already be evident and problematic).

In accordance with one or more embodiments, "pre-charging" of one or more drill pipe segments (individually or connected in series) may be gravity-fed, making use of a rig hoist or crane to lift one end of the drill pipe segment(s), or by the use of a plunger or "rabbit", e.g., of a type that may already be in use to check and clean potential debris from the inside of the drill pipe segment(s), to push or pull the large LCM objects into position.

In accordance with one or more variant embodiments, the large LCM objects may be added to one or more drill pipe segments when manipulating the segment(s) from the rig floor level, by making use of a mouse-hole and single joint clamp and tugger hoist to facilitate pouring the large LCM objects into the drill pipe segment(s). Once "pre-charged", as noted above, the drill pipe segment(s) can be interconnected with one or more other segments to create to other joints to create a stand, and can then be set back in the derrick for future use, or could immediately be added to the drill string currently running-in-hole.

<FIG> illustrates a flowchart of a method in accordance with one or more embodiments, as a general overview of steps which may be carried out in accordance with one or more embodiments described or contemplated herein.

As such, in accordance with one or more embodiments, one or more drill pipe segments are provided (<NUM>). By way of illustrative example, this could involve a single drill pipe segment as variously described and illustrated herein, or two or more interconnected drill pipe segments (one of which could be a pup j oint, as described and illustrated with respect to <FIG>). A quantity of LCM objects are disposed within the one or more drill pipe segments (<NUM>), and a retention element is provided that retains the LCM objects within the one or more drill pipe segments (<NUM>). By way of illustrative example, the retention element could be embodied by a dissolvable plug as described and illustrated herein (e.g., with respect to <FIG>, indicated at <NUM> or 564a/b), or by a capsule (e.g., as described and illustrated with respect to <FIG>, indicated at <NUM>) or sack (e.g., as described and illustrated with respect to <FIG>, indicated at 772a/b).

In accordance with one or more embodiments, the one or more drill pipe segments are connected to a drill string at a wellbore (<NUM>). Accordingly, as described herein, one or more drill pipe segments may be added or incorporated into a drill string such as that indicated at <NUM> in <FIG>. Additionally, drilling fluid is flowed through the drill string (<NUM>), e.g., as described and illustrated with respect to <FIG>, wherein this causes the retention element to release the LCM objects to propagate further (<NUM>). To the latter point, as described and illustrated herein, and merely by way of illustrative example, the drilling fluid may sufficiently saturate a retention element such as a dissolvable plug, capsule or sack such that LCM objects are able to then flow freely and uninhibitedly further into the drill string and/or into the wellbore.

Claim 1:
A method comprising:
providing one or more drill pipe segments (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
disposing a quantity of lost circulation material objects (<NUM>, <NUM>, 762a, 762b, <NUM>, <NUM>, <NUM>) within the one or more drill pipe segments;
providing a retention element that retains the lost circulation material objects within the one or more drill pipe segments;
connecting the one or more drill pipe segments to a drill string (<NUM>) at a wellbore (<NUM>, <NUM>); and
flowing drilling fluid (<NUM>, <NUM>) through the drill string (<NUM>),
wherein the flowing of drilling fluid (<NUM>, <NUM>) through the drill string (<NUM>) causes the retention element to release the lost circulation material objects (<NUM>, <NUM>, 762a, 762b, <NUM>, <NUM>, <NUM>) to propagate further.