Patent Description:
During the drilling of subterranean wells, such as subterranean wells used in hydrocarbon development operations, drilling mud and other fluids can be pumped into the well. In certain drilling operations, the wellbore of the subterranean well can pass through a zone that has induced or natural fractures, are cavernous, or otherwise have an increased permeability, which is known as a lost circulation zone. In such a case, the drilling mud and other fluids that are pumped into the well can flow into the lost circulation zone and become irretrievable.

Lost circulation can be encountered during any stage of hydrocarbon development operations. Lost circulation can be identified when drilling fluid that is pumped into the subterranean well returns partially or does not return to the surface. While some fluid loss is expected, excessive fluid loss is not desirable from a safety, an economical, or an environmental point of view. Lost circulation can result in difficulties with well control, borehole instability, pipe sticking, unsuccessful production tests, poor hydrocarbon production after well completion, and formation damage due to plugging of pores and pore throats by mud particles. In extreme cases, lost circulation problems may force abandonment of a well. <CIT> describes solids for use in borehole fluids. An additive manufacturing process can be used to produce solid objects for suspension in borehole fluids. The process can include solidifying a liquid composition at a succession of selected locations within a work space, in accordance with a digital design, which allows a variety of shapes to be made. The solids may be used, possibly in conjunction with other solids, to block loss of fluid into fractures in the formation around a borehole. <CIT> describes a method for strengthening a wellbore of a well. The method includes selecting a fracture sealing width of a fracture defined by a portion of a wellbore wall of the formation, and formulating a fracture sealing composition at least based on the fracture sealing width. <CIT> describes a well cement composition including multi-component fibres and a method of cementing using the same. The composition includes a hydraulic well cement and multi-component fibres having at least a first polymeric composition and a second polymeric composition. At least a portion of the external surfaces of the multi-component fibres include an ethylene-methacrylic acid or ethylene-acrylic acid co-polymer. A method of cementing a subterranean well includes introducing the well cement composition into a wellbore, together with water, and forming a cured cement in the wellbore. <CIT> describes a method and material for isolating a severe lost zone. A drilling fluid additive to reduce severe fluid losses in a well comprises a combination of granular scrap tire particles and polymer adhesive molded into a spherical shape. <CIT> describes a well drilling system with closed circulation of gas drilling fluid and fire suppression apparatus. The system includes an enclosure mounted on a wellhead between a wellbore and a rotary control head. The enclosure redirects the flow of cuttings laden gaseous drilling fluid being circulated out of the well and includes a plurality of fire extinguishing fluid injection nozzles arranged to inhibit or extinguish fire within the enclosure and the rotary control head.

When unacceptable drilling fluid losses are encountered, conventional lost circulation materials are deployed with the drilling fluid from the surface. The revised fluid that includes the conventional lost circulation materials is pumped downhole as part of the standard well circulation system. The revised fluid passes through a circulation port to plug and pressure seal the exposed formation at the point where losses are occurring. Once sealing has occurred and acceptable fluid loss control is established, drilling operations can resume. Conventional currently available lost circulation material is most effective at sealing regularly shaped formation cavities with widths up to approximately <NUM>-<NUM> millimeters (mm). In cavities with larger widths, effective sealing is often both challenging and costly.

Embodiments of this disclosure provide systems and methods of ensuring an optimized combination of lost circulation shape shapes, sizes and volume are deployed in an optimized sequence. The deployment mix of lost circulation shape is dependent on the type loss formation being treated, lost circulation material used and drilling fluid used. The composition and the delivery sequence of the lost circulation shape and the lost circulation material can be determined from fixed data, such as geophysical data relating to the lost circulation zone, the available lost circulation shapes, and the available lost circulation material. A batch disposal system can be used to prepare the deployment mix and to fill the lost circulation shapes with wetting fluid.

The lost circulation shape can be deployed with the conventional lost circulation material. The lost circulation shape is a hollow perforated geometric shape that can fill with wetting fluid and have a generally neutral buoyancy in the drilling fluid. Due to this generally neutral buoyancy the lost circulation shape can move downhole freely with the drilling fluid and exit the drill string through the circulation port with the conventional lost circulation material. The lost circulation shape would be drawn into thief zone cavities or vugulars. The lost circulation shape can act as a trap for the conventional lost circulation material and allow for accumulation and bridging of the lost circulation material onto the lost circulation shape. This will result in eventual plugging of the formation.

In an embodiment of this disclosure, a method for sealing a lost circulation zone associated with a subterranean well includes determining geophysical data of the lost circulation zone. An available range of lost circulation shape data is provided. An available range of lost circulation material data is provided. The geophysical data, the available range of lost circulation shape data, and the available range of lost circulation material data are part of a fixed data set. An initial lost circulation mix is determined from the fixed data set. An initial drill string downhole flow rate and an initial annulus uphole flow rate are determined and an initial loss volume is calculated. The initial lost circulation mix is delivered into the subterranean well. A revised drill string downhole flow rate and a revised annulus uphole flow rate are determined and a revised loss volume is calculated.

In alternate embodiments, the method can further include determining an initial lost circulation mix delivery sequence from the fixed data set. Delivering the initial lost circulation mix into the subterranean well can include delivering the initial lost circulation mix in the initial lost circulation mix delivery sequence. A revised lost circulation mix can be determined from the revised loss volume. The revised lost circulation mix can be delivered into the subterranean well. A revised lost circulation mix delivery sequence can be determined from the revised loss volume. Delivering the revised lost circulation mix into the subterranean well can include delivering the revised lost circulation mix in the revised lost circulation mix delivery sequence.

In other alternate embodiments, the geophysical data can include a cavity surface area. Providing the available range of lost circulation shape data can include providing the available range of lost circulation shape data for a lost circulation shape that is a hollow body having an outer skin and an open interior chamber. The outer skin can include a plurality of perforations that extend through the outer skin, providing fluid communication between an exterior of the lost circulation shape and the open interior chamber. The plurality of perforations can be sized to prohibit a passage of lost circulation material between the exterior of the lost circulation shape and the open interior chamber.

In yet other alternate embodiments, delivering the initial lost circulation mix into the subterranean well can include filling an open interior chamber of a lost circulation shape with a wetting fluid. The lost circulation shape can have an average lost circulation shape density. A difference between the average lost circulation shape density and a drilling fluid density can be <NUM>% or less of the drilling fluid density. The lost circulation shape can include a filling hole extending through an outer skin and having a diameter in a range of <NUM> to <NUM>. Filling the open interior chamber of the lost circulation shape can include delivering the wetting fluid into the open interior chamber through the filling hole.

In still other alternate embodiments, a lost circulation shape can be sized to be introduced into cavities of the lost circulation zone, forming a wedged lost circulation shape. The method can further include trapping lost circulation material with the wedged lost circulation shape to seal the lost circulation zone. An annular space can be defined between an outer diameter surface of a drill string and an inner diameter surface of a wellbore of the subterranean well. Delivering the initial lost circulation mix into the subterranean well can include circulating the initial lost circulation mix through the drill string within a drilling fluid traveling downhole within the drill string, through a circulating port, and into the annular space.

In an alternate embodiment of this disclosure, a method for sealing a lost circulation zone associated with a subterranean well includes determining geophysical data of the lost circulation zone. An available range of lost circulation shape data is provided and an available range of lost circulation material data is provided. The geophysical data, the available range of lost circulation shape data, and the available range of lost circulation material data are part of a fixed data set. An initial lost circulation mix is determined from the fixed data set. The initial lost circulation mix includes a lost circulation shape, a lost circulation material, and a wetting fluid. A batch disposal system is instructed to prepare the lost circulation shape. The initial lost circulation mix is delivered into the subterranean well.

In alternate embodiments, the batch disposal system can include a plurality of supply hoppers. Each of the plurality of supply hoppers can contain lost circulation shapes of the available range of lost circulation shapes. The batch disposal system can include a control unit and the method can further include controlling an amount of the lost circulation shapes delivered from each of the plurality of supply hoppers with the control unit.

In other alternate embodiments, the batch disposal system can include a wetting unit and the method can further include mixing the lost circulation shape and the wetting fluid within the wetting unit. The method can further include filling an open interior chamber of the lost circulation shape with the wetting fluid within the wetting unit. Alternately, the batch disposal system can include an additive manufacturing unit, and the method can include directing the additive manufacturing unit to form the lost circulation shape.

In yet another alternate embodiment of this disclosure, a system for sealing a lost circulation zone associated with a subterranean well includes an initial lost circulation mix. A composition of the initial lost circulation mix is derived from geophysical data of the lost circulation zone, an available range of lost circulation shape data, and an available range of lost circulation material data. The initial lost circulation mix includes a lost circulation shape, a lost circulation material, and a wetting fluid. A batch disposal system is operable to deliver the lost circulation shape. A drill string is operable to deliver the initial lost circulation mix into the subterranean well.

In alternate embodiments, the lost circulation shape can be a hollow body having an outer skin and an open interior chamber. The outer skin can include a plurality of perforations that extend through the outer skin, providing fluid communication between an exterior of the lost circulation shape and the open interior chamber. The plurality of perforations can be sized to prohibit a passage of the lost circulation material between the exterior of the lost circulation shape and the open interior chamber. The open interior chamber of the lost circulation shape can include the wetting fluid having a wetting fluid density. The lost circulation shape can have an average lost circulation shape density. A difference between the average lost circulation shape density and a drilling fluid density can be <NUM>% or less of the drilling fluid density. The lost circulation shape can include a filling hole extending through the outer skin and having a diameter in a range of <NUM> to <NUM>.

In yet other alternate embodiments, the batch disposal system can include a plurality of supply hoppers. Each of the plurality of supply hoppers can containing lost circulation shapes of the available range of lost circulation shapes. The batch disposal system can include a control unit operable to control an amount of the lost circulation shapes delivered from each of the plurality of supply hoppers. The batch disposal system can include a wetting unit, operable for mixing the lost circulation shape and the wetting fluid within the wetting unit. Alternately, the batch disposal system can includes an additive manufacturing unit operable to form the lost circulation shape.

So that the manner in which the features, aspects and advantages of the embodiments of this disclosure, as well as others that will become apparent, are attained and can be understood in detail, a more particular description of the disclosure may be had by reference to the embodiments that are illustrated in the drawings that form a part of this specification. It is to be noted, however, that the appended drawings illustrate only certain embodiments of the disclosure and are not to be considered limiting of the disclosure's scope, for the disclosure may admit to other equally effective embodiments.

The disclosure refers to particular features, including process or method steps. Those of skill in the art understand that the disclosure is not limited to or by the description of embodiments given in the specification.

Those of skill in the art also understand that the terminology used for describing particular embodiments does not limit the scope or breadth of the embodiments of the disclosure. In interpreting the specification and appended Claims, all terms should be interpreted in the broadest possible manner consistent with the context of each term. All technical and scientific terms used in the specification and appended Claims have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs unless defined otherwise.

As used in the Specification and appended Claims, the singular forms "a", "an", and "the" include plural references unless the context clearly indicates otherwise.

As used, the words "comprise," "has," "includes", and all other grammatical variations are each intended to have an open, non-limiting meaning that does not exclude additional elements, components or steps. Embodiments of the present disclosure may suitably "comprise", "consist" or "consist essentially of" the limiting features disclosed, and may be practiced in the absence of a limiting feature not disclosed. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

Where a range of values is provided in the Specification or in the appended Claims, it is understood that the interval encompasses each intervening value between the upper limit and the lower limit as well as the upper limit and the lower limit. The disclosure encompasses and bounds smaller ranges of the interval subject to any specific exclusion provided.

Where reference is made in the specification and appended Claims to a method comprising two or more defined steps, the defined steps can be carried out in any order or simultaneously except where the context excludes that possibility.

Looking at <FIG>, subterranean well <NUM> can have wellbore <NUM> that extends to an earth's surface <NUM>. Subterranean well <NUM> can be an offshore well or a land based well, and can be used for producing hydrocarbons from subterranean hydrocarbon reservoirs. Drill string <NUM> can be delivered into and located within wellbore <NUM>. Drill string <NUM> can include tubular member <NUM> and bottom hole assembly <NUM>. Tubular member <NUM> can extend from surface <NUM> into subterranean well <NUM>. Bottom hole assembly <NUM> can include, for example, drill collars, stabilizers, reamers, shocks, a bit sub and the drill bit. Drill string <NUM> can be used to drill wellbore <NUM>. In certain embodiments, tubular member <NUM> is rotated to rotate the bit to drill wellbore <NUM>.

Wellbore <NUM> can be drilled through lost circulation zone <NUM>. In embodiments lost circulation zone <NUM> is a layer of a subterranean formation that is located uphole of a hydrocarbon formation, downhole of a hydrocarbon formation, or between separate hydrocarbon formations. In certain embodiments, drill string <NUM> can pass through a cased section of wellbore <NUM> of subterranean well <NUM> in order to reach uncased open hole portion of wellbore <NUM>.

A system for sealing lost circulation zone <NUM> associated with subterranean well <NUM> includes a circulating port to provide downhole fluid circulation. The circulating port provides fluid communication between an inner bore of drill string <NUM> and annular space <NUM>. In commonly available systems a circulation flow path for drill string <NUM> can include flow of fluid in a downhole direction through the internal bore of drill string <NUM>. The fluid can flow out of the drill bit and flow in an uphole direction through annular space <NUM>. The exit of the flow of fluid through the drill bit is through a circulating port that is a drill bit nozzle. Drill bit nozzles can be intentionally small and specifically sized to create a backpressure in the drill string.

Annular space <NUM> is the elongated annular shaped space that extends a length of drill string <NUM> and is defined between an outer diameter surface of drill string <NUM> and an inner diameter surface wellbore <NUM>. During downhole fluid circulation, fluids can flow downhole through the inner bore of drill string <NUM> and uphole through annular space <NUM>. In reverse circulation, fluids can flow downhole through annular space <NUM> and uphole through the inner bore of drill string <NUM>.

In the example embodiment, drill string <NUM> can include circulating sub <NUM>. Circulating sub <NUM> can be a circulating sub known and commonly available in the industry for circulating fluids downhole. Circulating sub <NUM> can include circulating sub port <NUM>, which is a circulating port. Circulating sub port <NUM> extends through a sidewall of circulating sub <NUM> and provides fluid communication between the inner bore of drill string <NUM> and annular space <NUM>. In alternate embodiments, bottom hole assembly <NUM> can include the circulating port. Circulating sub <NUM> provides an alternative circulation flow path to using drill bit nozzles. Circulating sub <NUM> provides for a circulation port that is located uphole of the drill bit and can have ports that are larger than common drill bit nozzles.

The system for sealing lost circulation zone <NUM> can be used to seal the entry of cavity <NUM> of lost circulation zone <NUM> that has a cross sectional dimension X up to <NUM>. In certain embodiments, lost circulation zone <NUM> cannot be sealed with some currently available lost circulation material due to the large cross sectional dimension X of cavity <NUM>, or the resulting surface area of cavity <NUM>. The cavity surface area is the open area of cavity <NUM> measured along the inner diameter surface of wellbore <NUM>. Cavity <NUM> can be, for example, vugular or cavernous faults.

Looking at <FIG>, after bottom hole assembly <NUM> has reached or passed through lost circulation zone <NUM>, a combination of lost circulation shape <NUM> and lost circulation material <NUM> can be used to seal cavities <NUM> of lost circulation zone <NUM>.

In the example embodiment of <FIG>, lost circulation shape <NUM> and lost circulation material <NUM> are pumped in a direction downhole through drill string <NUM>, and exit circulating sub port <NUM> to reach annular space <NUM> for delivery to lost circulation zone <NUM>.

Looking at <FIG>, lost circulation shape <NUM> is a hollow body having an outer skin <NUM> that defines the shape of lost circulation shape <NUM> and an open interior chamber. Outer skin <NUM> can have a thickness in a range of <NUM> to <NUM>. In alternate embodiments, such as when a metallic material is used to form lost circulation shape <NUM>, outer skin <NUM> can have a thickness as small as <NUM>. Lost circulation shape <NUM> can have a variety of diameters. In general, a smaller diameter lost circulation shape <NUM> can have a smaller thickness of outer skin <NUM> and a larger diameter lost circulation shape <NUM> can have a larger thickness of outer skin <NUM>. In certain embodiments, the thickness of outer skin <NUM> can be directly proportional to the diameter of lost circulation shape <NUM>. In alternate embodiments, when lost circulation shape <NUM> has a larger diameter, lost circulation shape <NUM> can include an internal support structure, such as a web type structure, to provide internal support to outer skin <NUM>.

In example embodiments shown, lost circulation shape <NUM> is a sphere, a shape that includes both square and triangular shaped surfaces, or a cube. In alternate embodiments, lost circulation shape <NUM> can have other three dimensional geometric shapes. As an example, lost circulation shape <NUM> can generally have the shape of a cube, ovoid, egg, hyper rectangle, triangular prism, pyramid, cone, or cylinder.

Lost circulation shape <NUM> can have a sufficient size to seal lost circulation zone <NUM>, without being so large in size that lost circulation shape <NUM> cannot fit through the circulation port. Lost circulation shape <NUM> is sized to flow through the circulation port with a drilling fluid in an unrestricted manner. In certain embodiments, a mix of various sizes and shapes of lost circulation shapes <NUM> can be used for sealing cavities <NUM> of various sizes.

In certain embodiments, lost circulation shape <NUM> can be formed in a variety of sizes. In certain embodiments, the smallest of lost circulation shape <NUM> has a minimum size. The minimum size of lost circulation shape <NUM> is such that the smallest minimum hypothetical sphere in which lost circulation shape <NUM> having the minimum size could fit has a diameter of <NUM>, regardless of the geometric shape of lost circulation shape <NUM>. The largest of lost circulation shape <NUM> has a maximum size. The maximum size of lost circulation shape <NUM> is such that a smallest maximum hypothetical sphere in which lost circulation shape <NUM> having the maximum size could fit has a diameter of <NUM> regardless of the geometric shape of lost circulation shape <NUM>. In alternate embodiments, the maximum size of lost circulation shape <NUM> is such that a smallest maximum hypothetical sphere in which lost circulation shape <NUM> having the maximum size could fit has a diameter of <NUM> regardless of the geometric shape of lost circulation shape <NUM>.

Lost circulation shape <NUM> can be formed of a metal, ceramic, or polymeric material. As an example, lost circulation shape <NUM> could be formed of any of a variety of suitable metallic materials, such as, for example, aluminum, titanium, copper, or nickel. Alternately, lost circulation shape <NUM> could be formed of any of a variety of suitable ceramic materials, such as, for example, gypsum, alumina, zircon, silicon nitride, glass, or silicate. Alternately, lost circulation shape <NUM> could be formed of any of a variety of suitable polymeric materials including plastic, thermoplastic and elastomers, such as, for example, acrylonitrile butadiene styrene (ABS), high-impact polystyrene (HIPS), polypropylene, polyethylene, nylon, acrylic, polyethylene terephthalate (PET), poly carbonate, or polyurethane.

Alternately, lost circulation shape <NUM> can be formed of other materials that are suitable for additive manufacturing, such as vat photopolymerisation, material extrusion, material jetting, binder jetting, powder bed fusion, direct energy deposition, and sheet lamination fabrication techniques.

The material used to form lost circulation shape <NUM> can be determined by the drilling application, the selected drilling fluid, and the lost circulation material <NUM> that is to be used for a particular application. In embodiments of this disclosure, lost circulation material <NUM> and lost circulation shape <NUM> can be used to solve a total loss situation where there is no need for removal of lost circulation material <NUM> and lost circulation shape <NUM>. In other embodiments, lost circulation material <NUM> and lost circulation shape <NUM> could be formed of a removable material. As an example, lost circulation material <NUM> and lost circulation shape <NUM> could be formed of aluminum that could be dissolved and removed with an acid treatment.

Outer skin <NUM> of lost circulation shape <NUM> includes a plurality of perforations <NUM> that extend through outer skin <NUM>. Perforations <NUM> provide fluid communication between an exterior of lost circulation shape <NUM> and the open interior chamber of lost circulation shape <NUM>. Perforations <NUM> allow for drilling fluid to enter the open interior chamber of lost circulation shape <NUM>. Because the drilling fluid can pass into and through lost circulation shape <NUM>, minimal hydrostatic forces are applied to lost circulation shape <NUM> downhole. Larger perforations <NUM> will minimize the hydrostatic forces. However, if perforations <NUM> are too large, then lost circulation shape <NUM> will not trap lost circulation material <NUM>. The size, shape, and number of perforations <NUM> can be optimized for each individual application. Alternately, a generic layout of perforations <NUM> can be developed with the size, shape, and number of perforations selected to function in a variety of subterranean wells <NUM>.

Perforations <NUM> are sized to minimize or prohibit the passage of lost circulation material <NUM> between the exterior of lost circulation shape <NUM> and the open interior chamber of lost circulation shape <NUM>. Perforations <NUM> are sized to trap lost circulation material <NUM> within lost circulation zone <NUM>, forming a seal within lost circulation zone <NUM>. As an example, perforations <NUM> can have dimensions that are smaller in size than lost circulation material <NUM> (<FIG>). Alternately some commonly available lost circulation material <NUM> is capable of sealing cavities <NUM> that have a dimension larger than the size of lost circulation material <NUM>. In certain embodiments the maximum size of perforations <NUM> will be smaller than the maximum bridging limitation of lost circulation material <NUM>. In such embodiments the maximum size of perforations <NUM> can be larger than the size of lost circulation material <NUM> so that some lost circulation material <NUM> pass through perforations <NUM> before lost circulation material <NUM> bridges across lost circulation shape <NUM>. Performance data can be obtained relating to the capabilities of currently available lost circulation material <NUM>. Such performance data can include the size of cavities that can be sealed with such lost circulation material. The performance data for a selected lost circulation material can be referenced for determining a suitable size of perforations <NUM>.

In the example of <FIG> perforations <NUM> through outer skin <NUM> of lost circulation shape <NUM> are diamond shaped. In the Example of <FIG> and <FIG>, perforations <NUM> through outer skin <NUM> of lost circulation shape <NUM> are circular. In the example of <FIG> perforations <NUM> through outer skin <NUM> of lost circulation shape <NUM> are four sided. Such perforations <NUM> can be generally rectangles, or frusto-conical shaped. In the example of <FIG> perforations <NUM> through outer skin <NUM> of lost circulation shape <NUM> can include both four sided shapes and circular shapes.

When perforations <NUM> are circular perforations <NUM> can have, for example, a size in a range of <NUM> to <NUM> in diameter. In alternate embodiments perforations <NUM> can have other shapes. For example purposes only, perforations <NUM> can be shaped as squares, hexagons, pentagons, triangles, rectangles, diamonds, circles or combinations of any of these shapes. The size, shape, and spacing of perforations <NUM> can be selected for optimized performance with a selected lost circulation material <NUM> (<FIG>). If the number of perforations <NUM> is large enough that the structural integrity of lost circulation shape <NUM> is compromised, then structural members may be added within the open interior chamber of lost circulation shape <NUM>.

Looking at <FIG>, lost circulation shape <NUM> can further include filling hole <NUM>. Filling hole <NUM> extends through outer skin <NUM>. In certain embodiments, filling hole <NUM> can have a diameter in a range of <NUM> to <NUM>. Filling hole <NUM> facilitates the filling of the open interior chamber with a wetting fluid. The wetting fluid can be, for example, a drilling fluid. In certain embodiments, the filling of lost circulation shape <NUM> could be assisted by holding the lost circulation shape under vacuum and then introducing wetting fluid. Alternately, a pressure can be applied instead of a vacuum for filling the open interior chamber with wetting fluid. Using a vacuum or pressure would be most useful when perforations <NUM> are sufficiently small that wetting fluid does not travel easily into the open interior chamber. Using a vacuum or pressure can overcome surface tension that could prevent the open interior chamber from filling with wetting fluid before lost circulation shape <NUM> is circulated downhole through drill string <NUM>. Filling hole <NUM> may or may not be a requirement depending on the size and arrangement of perforations <NUM> and the resulting buoyancy of lost circulation shape <NUM> in the drilling fluid.

The density of lost circulation shape <NUM> together with the presence of wetting fluid within the open interior chamber of lost circulation shape <NUM> allow lost circulation shape <NUM> to have generally neutral buoyancy within the drilling fluid. As used in this disclosure, a generally neutral buoyancy means that the lost circulation shapes will flow with the drilling fluid and will not tend to sink or rise relative to the movement of the drilling fluid.

Because of the wetting fluid located within the open interior chamber of lost circulation shape <NUM>, the average lost circulation shape density does not need to be absolutely equal to the drilling fluid density that is carrying lost circulation shape <NUM>. The lost circulation shape <NUM> can be carried by the drilling fluid free of excessive sinking or rising of lost circulation shape <NUM> relative to the movement of the drilling fluid if an average lost circulation shape density is near to the density of the drilling fluid. As an example, in certain embodiments the difference between the average lost circulation shape density and the drilling fluid density is <NUM>% or less of the drilling fluid density. In alternate example embodiments, the difference between the average lost circulation shape density and the drilling fluid density is <NUM>% or less of the drilling fluid density.

For the sake of clarity, as an example, a drilling fluid density of some currently available drilling fluid can range from <NUM>,<NUM> to <NUM>,<NUM>/cc( <NUM> pounds per gallon (ppg) to <NUM> ppg). If a drilling fluid with a density of <NUM>,<NUM>/cc (<NUM> ppg) is used, then <NUM>% of <NUM>,<NUM>/cc (<NUM> ppg) is <NUM>,<NUM>/cc (<NUM> ppg). In this example embodiment, if the difference between the average lost circulation shape density and the drilling fluid density is <NUM>% or less of the drilling fluid density, then the average lost circulation shape density can be in a range of <NUM>,<NUM> to <NUM>,<NUM>/cc (<NUM> ppg to <NUM> ppg). For the avoidance of doubt, the average lost circulation shape density is the density of lost circulation shape <NUM> calculated without the wetting fluid being locate within the open interior chamber.

In embodiments of this disclosure, a mixture of both lost circulation shape <NUM> and lost circulation material <NUM> is used to seal lost circulation zone <NUM>. If some currently available lost circulation material only was used (with no lost circulation shape <NUM>), the lost circulation material could flow into and out of cavities <NUM> without forming a seal. Some commonly used currently available lost circulation material would be too small relative to the cross sectional dimension X of cavity <NUM> for such lost circulation material to effectively and dependably seal lost circulation zone <NUM>. If lost circulations shapes <NUM> were used alone, it is possible that with a sufficient number of lost circulations shapes <NUM> that eventually lost circulation zone <NUM> could be sealed. However, because perforations <NUM> through outer skin <NUM> could continue to allow for the flow of fluids into and out of the open interior chamber of lost circulation shapes <NUM>, lost circulation would therefore only be somewhat restricted.

Looking at <FIG>, lost circulation material <NUM>, and lost circulation shape <NUM> can be used together and pumped into cavity <NUM>. Looking at <FIG>, by using both lost circulation shape <NUM> and lost circulation material <NUM>, lost circulation shape <NUM> can be sized to be wedged into cavities <NUM> of lost circulation zone <NUM>, forming a wedged lost circulation shape. With lost circulation shape <NUM> constrained within lost circulation zone, loss flow will continue through perforations <NUM>. Due to the small size of perforations <NUM>, lost circulation material <NUM> will collect and within and on the outer surfaces of lost circulation shape <NUM>. Lost circulation material <NUM> can be trapped by the wedged lost circulation shape to seal lost circulation zone <NUM>. Looking a <FIG>, lost circulation material <NUM> will collect and bridge and cause a total plug and consequent pressure seal. During such process, lost circulation shape <NUM> may be deformed, collapse, or be crushed due to well bore pressure acting on the formation. Such pressure will force lost circulation shape <NUM> and lost circulation material <NUM> further into cavities <NUM>, thereby giving a fully anchored seal. In alternate embodiments, lost circulation shape <NUM> may not be deformed, collapse or be crushed, but maintain its original <NUM>-dimensional structure.

As disclosed in further detail, the mix of shapes and sizes of lost circulation shapes <NUM> can be tailored for a particular lost circulation zone <NUM> through the use of fixed data input, variable data input, or both fixed and variable data input. The formation plugging ability of lost circulation shape <NUM> and lost circulation material <NUM> will be dependent on the sizes of lost circulation shape <NUM> deployed, the combination of sizes of lost circulation shape <NUM> deployed, such as the ratio of the small to large sizes of the deployed mix of lost circulation shape <NUM>, and the volume of lost circulation shapes <NUM> deployed. The sequence in which the shapes and sizes of lost circulation material <NUM> is delivered into wellbore <NUM> can further affect the plugging ability of lost circulation shape <NUM>. As an example, a lost circulation mix delivery sequence can include delivering smaller sized lost circulation shapes <NUM> first, followed by larger sized lost circulation shapes <NUM>, or a mix of small and large sized lost circulation shapes <NUM> delivered together, or larger sized lost circulation shapes <NUM> first, followed by smaller sized lost circulation shapes <NUM>.

A packing density prediction model can be used in the process of selecting the lost circulation shapes <NUM> to be utilized. A packing density model would ensure that for a given cavity surface area, an optimized packing density of the lost circulation shape would be obtained to provide a net in which the lost circulation material <NUM> can accumulate to plug the cavity <NUM>.

Additional factors such as the shape of lost circulation shape <NUM>, the material used to form lost circulation shape <NUM>, and the size, shape, number, and spacing of perforations <NUM> will also affect the plugging ability of lost circulation shape <NUM>.

An optimum mix of lost circulation shape <NUM> and lost circulation material <NUM> that can be used to seal lost circulation zone <NUM>, as well as the optimum sequence for delivering the lost circulation shape <NUM> and lost circulation material <NUM> can be determined. A fixed data set can be determined and evaluated in order to determine the lost circulation mix and delivery sequence. The fixed data set can include, for example, geophysical data of lost circulation zone <NUM>, an available range of lost circulation shape data, and an available range of lost circulation material data.

Geophysical data of lost circulation zone <NUM> can include, for example, information relating to the formation and to cavity <NUM>. Geophysical data can include the type of formation, the cavity surface area, and dispersion. The available range of lost circulation shape data can include the combination of size and shape of lost circulation shapes <NUM> that are available to be delivered into wellbore <NUM>. The available range of lost circulation shape data can further include the range of possible size, shape, number, and orientation of perforations <NUM> that can be part of lost circulation shape <NUM>. The lost circulation shapes <NUM> will be selected to ensure maximum plugging and flow with respect to the lost circulation material <NUM>.

The available range of lost circulation material data can include details relating to possible lost circulation material <NUM> that can be delivered into wellbore <NUM>. As an example, the range of lost circulation material data can include the type, size, shape, and other specifics relating to a lost circulation material can be delivered into wellbore <NUM>.

An initial lost circulation mix can be determined using the fixed data set. The initial lost circulation mix is the selected combination of lost circulation shapes <NUM> and lost circulation material <NUM> that can be initially delivered into wellbore <NUM>. In certain embodiments, the initial lost circulation mix can include a wetting fluid. The wetting fluid can be located within the open interior chamber of lost circulation shape <NUM>, and can be used as a fluid stream for the delivery of the lost circulation mix into wellbore <NUM>.

In embodiments, the delivery sequence for both the lost circulation shapes <NUM> and the lost circulation material <NUM> of the lost circulation mix can also be determined by the using the fixed data set. As an example, the initial lost circulation mix delivery sequence can be calculated from the fixed data set, for delivering the initial lost circulation mix into subterranean well <NUM>.

In embodiments, the initial lost circulation mix and the initial lost circulation mix delivery sequence can alternately be determined by assessing variable data. The variable data can include data regarding the flow in and the flow out of subterranean well <NUM>. The volume loss rate of fluids flowing out of subterranean well <NUM> compared to fluids that are flowing into subterranean well <NUM> can be included as input data for the initial calculation of the initial lost circulation mix.

As an example, the variable data can include a drill string downhole flow rate, and an annulus uphole flow rate. Before, during, and after delivery of the initial lost circulation mix the drill string downhole flow rate can be determined. The drill string downhole flow rate is the volumetric flow rate of the flow of drilling fluid and lost circulation mix that is being delivered in a downhole direction through drill string <NUM>.

Before, during, and after delivery of the initial lost circulation mix the annulus uphole flow rate can also be determined. The annulus uphole flow rate is the volumetric flow rate of the flow of drilling fluid that is being returned to the surface in an uphole direction through annular space <NUM>. By calculating the difference between the annulus uphole flow rate and the drill string downhole flow rate, the amount of fluids being lost can be determined. In a total loss situation, all of the drilling fluid would be lost into the lost circulation zone <NUM> and there would be no annulus uphole flow rate.

The calculated difference between the annulus uphole flow rate and the drill string downhole flow rate can be evaluated before the delivery of the initial lost circulation mix to arrive at an initial loss volume. In certain embodiments, this initial loss volume can be used to determine the composition of the initial lost circulation mix and the initial lost circulation mix delivery sequence.

The initial lost circulation mix can be delivered into subterranean well <NUM><NUM> in the initial lost circulation mix delivery sequence. In order to make adjustments to the lost circulation mix being delivered into wellbore <NUM> of subterranean well <NUM>, the variable data can be measured and evaluated during and after delivery of the initial lost circulation mix can be delivered into subterranean well <NUM>. As an example, during the delivery of the lost circulation mix into wellbore <NUM>, a revised drill string downhole flow rate and a revised annulus uphole flow rate can be measured and a revised loss volume can be calculated. This revised loss volume can be evaluated as an indication of the success of the initial lost circulation mix in plugging cavities <NUM>.

The feedback data obtained from determining the revised loss volume can be used to determine if alterations to the characteristics of the lost circulation shape <NUM>, the lost circulation material <NUM>, or the wetting fluid is required. If the loss volume has not be sufficiently reduced by the initial lost circulation mix, a revised lost circulation mix can be developed from the revised loss volume information and the revised lost circulation mix can be delivered into subterranean well <NUM>. The variable data can also be used to determine a revised lost circulation mix delivery sequence. The revised lost circulation mix can be delivered into subterranean well <NUM> in the revised lost circulation mix delivery sequence.

Looking at <FIG>, batch disposal system <NUM> can be used to prepare the mix of lost circulation shape <NUM> to be delivered into wellbore <NUM> of subterranean well <NUM>. In the example embodiment of <FIG>, batch disposal system <NUM> can include multiple supply hoppers <NUM>. Each supply hopper <NUM> can contain a lost circulation shape <NUM> of the available range of lost circulation shapes <NUM>. Lost circulation shapes <NUM> contained within supply hoppers <NUM> can be premanufactured so that supply hoppers <NUM> have stock product.

Batch disposal system <NUM> can also include wetting fluid tank <NUM>. Wetting fluid tank <NUM> can contain wetting fluid <NUM>. Wetting fluid <NUM> can be, for example, the drilling fluid used during drilling operations in wellbore <NUM>. In alternate embodiments, wetting fluid <NUM> can be another drilling fluid.

Each supply hopper <NUM> and wetting fluid tank <NUM> are in fluid communication with wetting unit <NUM>. Lost circulation shapes <NUM> and wetting fluid <NUM> can both be delivered into wetting unit <NUM> for mixing lost circulation shapes <NUM> with wetting fluid <NUM>. Wetting unit <NUM> can also facilitate the filling of the open interior chamber of lost circulation shapes <NUM> with wetting fluid <NUM>. As an example, wetting unit <NUM> can provide a vacuum and as wetting fluid <NUM> is delivered to wetting unit <NUM> the vacuum can cause wetting fluid <NUM> to enter the open interior chamber of lost circulation shape <NUM> by way of filling hole <NUM> (<FIG>). Alternately, wetting unit <NUM> can provide a pressure instead of a vacuum for filling the open interior chamber of lost circulation shape <NUM> with wetting fluid <NUM>.

Wetting unit <NUM> can provide sufficient vacuum or pressure such that the open interior space of lost circulation shapes <NUM> are completely full and wetted with wetting fluid <NUM> to ensure that no air is trapped within lost circulation shape <NUM>, which would affect the neutral buoyancy of lost circulation shape <NUM> within the drilling fluid. The introduction of wetting fluid into wetting unit <NUM> also acts as the lost circulation shape transport medium to carry lost circulation shapes <NUM> within wellbore <NUM>. Wetting unit <NUM> can include sensor <NUM> that can signal control unit <NUM> when a batch of lost circulation shape <NUM> has been fully combined and wetted. Sensor <NUM> can be, for example, a pressure sensor, a mass sensor, an optical sensor, or a combination of these and other sensors.

Control unit <NUM> of batch disposal system <NUM> can be used to control the amount of lost circulation shapes <NUM> being delivered into wetting unit <NUM> from supply hoppers <NUM>. Control unit <NUM> can move hopper control valve <NUM> between an open position and a closed position. Each supply hopper <NUM> can be associated with a separate hopper control valve <NUM>. When hopper control valve <NUM> is in the closed position, lost circulation shapes <NUM> located within the supply hopper <NUM> associated with that hopper control valve <NUM> is blocked from traveling from supply hopper <NUM> to wetting unit <NUM>.

When hopper control valve <NUM> is in the open position, lost circulation shapes <NUM> located within the supply hopper <NUM> associated with that hopper control valve <NUM> can travel from supply hopper <NUM> to wetting unit <NUM>. A hopper sensor can be used to measure or count the amount of lost circulation shapes <NUM> that is delivered from supply hopper <NUM> to wetting unit <NUM> while the hopper control valve <NUM> is in the open position.

Control unit <NUM> can further be used to control the amount of wetting fluid <NUM> being delivered into wetting unit <NUM> from wetting fluid tank <NUM>. Control unit <NUM> can move tank control valve <NUM> between an open position and a closed position. When tank control valve <NUM> is in the closed position, wetting fluid <NUM> located within wetting fluid tank <NUM> is blocked from traveling from wetting fluid tank <NUM> to wetting unit <NUM>.

When tank control valve <NUM> is in the open position, wetting fluid <NUM> located within wetting fluid tank <NUM> can travel from wetting fluid tank <NUM> to wetting unit <NUM>. A tank sensor can be used to measure the amount of wetting fluid <NUM> that is delivered from wetting fluid tank <NUM> to wetting unit <NUM> while the tank control valve <NUM> is in the open position.

Operator interface <NUM> can be used to communicate with control unit <NUM>. Operator interface <NUM> can, for example, provide instructions to control unit <NUM> to instruct batch disposal system <NUM> to prepare the mix of lost circulation shape <NUM> to be used in the lost circulation mix. Operator interface can also be used to display the status of the sensors and valves of batch disposal system <NUM>, to display the fixed data, to display the historical and current variable data, to assist in calculating the optimal lost circulation mix from the fixed and variable data, and to perform other tasks associated with the sealing of lost circulation zone <NUM>.

After the lost circulation shapes <NUM> have been filled and wetted with wetting fluid <NUM>, the filled and wetted lost circulation shapes <NUM> can be delivered into discharge unit <NUM>. Discharge unit <NUM> can be a container that is filled with the wetted lost circulation shapes <NUM>. The container can be used to transport the wetted lost circulation shapes <NUM> to the uphole end of the wellbore <NUM>. Alternately, the container can feed directly through the drilling floor into subterranean well <NUM>.

Looking at <FIG>, in an alternate example embodiment, instead of using stock lost circulation shapes <NUM>, batch disposal system <NUM> can include additive manufacturing unit <NUM>. Additive manufacturing unit <NUM> can be used to form lost circulation shapes <NUM>. Additive manufacturing unit can form lost circulation shapes <NUM> by vat photopolymerisation, material extrusion, material jetting, binder jetting, powder bed fusion, direct energy deposition, or sheet lamination fabrication techniques. Additive manufacturing unit <NUM> can form any lost circulation shape <NUM> within the available range of lost circulation shapes.

Additive manufacturing unit <NUM> can be in communication with wetting unit <NUM>. Control unit <NUM> can control the lost circulation shapes <NUM> being formed by additive manufacturing unit <NUM> and delivered into wetting unit <NUM>. Control unit <NUM> can further be used to control the amount of wetting fluid <NUM> being delivered into wetting unit <NUM> from wetting fluid tank <NUM>. After the lost circulation shapes <NUM> have been filled and wetted with wetting fluid <NUM>, the filled and wetted lost circulation shapes <NUM> can be delivered into discharge unit <NUM>.

In an example of operation, looking at <FIG>, in step <NUM> fixed data can be provided. The fixed data can include in step <NUM> the available range of lost circulation shape data "LCS Data. " In step <NUM>, the available range of lost circulation material data "LCM Data" can be provided. In step <NUM> the available range of lost circulation shape data and the available range of lost circulation material data can be used for the selection calculation of lost circulation shapes <NUM> and lost circulation material <NUM> to be used in the initial lost circulation mix.

In step <NUM>, the geophysical data can be provided. In step <NUM> the fixed data can be used to calculate the initial lost circulation mix as well as the initial delivery sequence for the initial lost circulation mix.

In step <NUM>, the variable data can be provided. The variable data can include the initial drill string downhole flow rate data that is provided in step <NUM> and the initial annulus uphole flow rate data that is provided in step <NUM>. The initial loss volume can be calculated in step <NUM> from the initial drill string downhole flow rate data and the initial annulus uphole flow rate data. In step <NUM> the initial lost circulation mix volume can be calculated using both the variable data and the fixed data. Having obtained the lost circulation mix, sequence, and volume, the batch of lost circulation shapes <NUM> to be used in the initial lost circulation mix can be produced in step <NUM> by batch disposal system <NUM>.

During the delivery of the initial lost circulation mix into subterranean well <NUM>, revised variable data can be determined by repeating step <NUM> to determine a revised drill string downhole flow rate data and repeating step <NUM> to determine a revised annulus uphole flow rate data. The revised loss volume can be calculated in step <NUM> from the revised drill string downhole flow rate data and the revised annulus uphole flow rate data. This revised loss volume can be compared to the initial loss volume to determine in step <NUM> if the volume loss has decreased.

If there has been no decrease in the volume loss, or if there has been an unsatisfactory decrease in the volume loss, then the lost circulation mix volume can be adjusted to arrive at a revised lost circulation mix. A batch of lost circulation shapes <NUM> to be used in the revised lost circulation mix can be produced in step <NUM> by batch disposal system <NUM>. If there has been a satisfactory decrease in the volume loss, then batch disposal system <NUM> can continue to produce the batch of lost circulation shapes <NUM> that was used in the initial lost circulation mix.

Looking at <FIG>, when delivering the lost circulation mix into subterranean well <NUM>, lost circulation shape <NUM> and lost circulation material <NUM> are circulated downhole through drill string <NUM> with drilling fluid. The drilling fluid can be formulated for the particular conditions of wellbore <NUM>. The drilling fluid can be, for example, a water based mud, an oil based mud, or a synthetic based mud.

Lost circulation shape <NUM> and lost circulation material <NUM> can be introduced into drill string <NUM> at surface <NUM> and can exit drill string <NUM> through circulating sub port <NUM>. Because lost circulation shape <NUM> is generally neutrally buoyant in the drilling fluid, the pumping time required for delivering lost circulation material <NUM> to lost circulation zone <NUM> can be calculated by volume displacement methods, which is well understood in the art of circulating fluids in wellbores.

During the process of delivering lost circulation shape <NUM> and lost circulation material <NUM> downhole, if drilling operations could continue for a process that used only the lost circulation material <NUM>, this process would not change with the addition of lost circulation shape <NUM>. Therefore, embodiments for delivering the lost circulation shape <NUM> and lost circulation material <NUM> downhole could be undertaken while drilling operations continue and without having to remove drill string <NUM> from wellbore <NUM>. The addition of lost circulation shape <NUM> may not otherwise change the lost circulation sealing procedure.

Looking at <FIG> and <FIG>, lost circulation shape <NUM> and lost circulation material <NUM> enter cavity <NUM>. Looking at <FIG> and <FIG>, lost circulation shape <NUM> can become wedged within cavity <NUM>. Looking at <FIG> and <FIG>, as drilling fluid continues to pass through lost circulation shape <NUM>, lost circulation material <NUM> can become lodged in or against lost circulation shape <NUM> until a complete formation fault pressure seal is obtained. As lost circulation shape <NUM> is trapped and lost circulation zone <NUM> becomes blocked this will result in a pressure differential creation across the blockage formed by lost circulation shape <NUM> due to the drilling overbalance hydrostatic pressure.

In the example embodiments of <FIG> and <FIG>, lost circulation shape <NUM> has deformed, collapsed or been crushed within cavity <NUM>. A crushed lost circulation shape <NUM> could trap lost circulation material more quickly than uncrushed lost circulation shape <NUM>. In addition, a crushed lost circulation shape <NUM> could become lodged deeper into cavity <NUM>, providing a more secure seal of lost circulation zone <NUM> (<FIG>).

Lost circulation shape <NUM> is sized to be wedged into cavities <NUM> of lost circulation zone <NUM>, forming a wedged lost circulation shape. Lost circulation material <NUM> is then trapped by the wedged lost circulation shape to seal lost circulation zone <NUM>.

Embodiments described in this disclosure therefore provide systems and methods that are capable of sealing a lost circulation zone with cavities that are larger than those that can be sealed with currently available lost circulation material. Systems and methods provide for delivery to the lost circulation zone <NUM> without the need for a specific secondary remedial bottom hole assembly or the need for a longer, adapted, or revised sealing operation.

Claim 1:
A method for sealing a lost circulation zone (<NUM>) associated with a subterranean well (<NUM>), the method including:
determining geophysical data of the lost circulation zone;
providing an available range of lost circulation shape data;
providing an available range of lost circulation material (<NUM>) data, where the geophysical data, the available range of lost circulation shape data, and the available range of lost circulation material data are part of a fixed data set;
determining an initial lost circulation mix from the fixed data set;
determining an initial drill string (<NUM>) downhole flow rate and an initial annulus uphole flow rate and calculating an initial loss volume;
delivering the initial lost circulation mix into the subterranean well; and
determining a revised drill string downhole flow rate and a revised annulus uphole flow rate and calculating a revised loss volume.