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 bore of the subterranean well can reach or pass through a zone that has induced or natural fractures, are cavernous, or otherwise have a high permeability, and which is known as a lost circulation zone. In addition, wellbore stability issues can occur while drilling in any well and can include hole collapse, or fractures leading to a lost circulation. These issues can be due to weak formations, permeable rocks, or fractures that occurs naturally or are induced while drilling.

In such a case, the drilling mud and other fluids that are pumped into the well can flow into the lost circulation zone. In such cases all, or a portion of the drilling mud and other fluids can be lost in the lost circulation zone.

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 at all 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.

Sealing these problematic zones is important before continuing to drill the rest of the well. If the problem zone is not sealed or supported, the wellbore wall can collapse and cause the drill string to get stuck, or the drilling mud can become lost in the formation.

In some currently available systems, when unacceptable drilling fluid losses are encountered, conventional lost circulation technologies can be deployed into the drilling fluid from a terranean surface. The drilling fluid, which includes loss mitigation chemicals, is pumped downhole as part of the standard well circulation system. The modified drilling fluid passes through the bottom hole assembly (BHA), including a drill bit, or bypasses the BHA through a circulation port and is ultimately designed to plug lost circulation zone. As an example, the modified drilling fluid can seal the exposed formation at a location in the wellbore in which losses are occurring. Once sealing of the wellbore has occurred and acceptable fluid loss control is established, drilling operations may resume. <CIT> describes a drilling fluid for use when drilling a borehole including solid polymeric objects as a lost circulation additive. The objects may be moulded, 3D-printed or chopped from larger pieces of polymer by granulating machinery. Shapes with edges, points, corners or projections assisting the objects in lodging within and bridging a fracture encountered or formed while drilling. <CIT> describes a method of triggering heating within a subterranean formation by introducing a wellbore fluid containing a dispersed carbon nanomaterial into a wellbore through the subterranean formation; lowering a microwave or ultraviolet radiation source into the wellbore; and irradiating the wellbore with microwave or ultraviolet radiation, thereby increasing the temperature of the wellbore fluid and/or wellbore.

Conventional loss circulation material (LCM) may seal uniformly shaped formation voids with an opening size, for example, of up to approximately <NUM>-<NUM> millimeters (mm) but struggle with un-uniform and larger voids. In some current systems activators can be used to harden a LCM. Such activators can be stimulated, for example, by temperature, pH, or over time alone. However, it can be difficult to predict the exact temperature and pH at the location of the loss zone, and the time required to reach and fill the loss zone can change due to unexpected events while delivering the LCM to the loss zone. If the LCM hardens before reaching the loss circulation zone, the entire downhole assembly could become plugged and require replacement. Alternately, if the required temperature or pH is not reached, the LCM may not harden.

Embodiments of this disclosure include systems and methods that include an LCM that has oligomers, monomers and photo-initiators. An ultraviolet source is assembled adjacent to the drilling bit. When severe losses occur, the LCM containing the oligomer, monomer, and photo-initiator could be pumped down from the surface. Photo-initiators are sensitive to ultraviolet light and as the LCM passes through the illuminating ultraviolet source, the photo-initiator gets activated to generate free-radicals. These free radicals trigger the monomer to undergo a cross-linking or polymerization reaction with oligomer. Therefore, the whole LCM which is in a flowable state before irradiation by the ultraviolet light starts to harden and set. The hardened material can possess sufficient compressive strength to be able withhold the overburden pressure. A downhole actuator is used to turn on and off the ultraviolet light source wherever necessary by sending signal to the power source in the ultraviolet light source system.

A first aspect of the present invention provides a method for sealing a lost circulation zone of a subterranean well includes extending a drill string into the subterranean well. The drill string has an ultraviolet system, an actuator, and a fluid flow path. The actuator is instructed to transmit an on signal to the ultraviolet system to switch the ultraviolet system to an on condition. In the on condition the ultraviolet system generates ultraviolet light directed towards the fluid flow path of the drill string. A loss circulation material is delivered into the fluid flow path of the drill string, the loss circulation material having an oligomer, a monomer, and a photo-initiator. The loss circulation material is exposed to the ultraviolet light to activate the loss circulation material. The loss circulation material is delivered to the lost circulation zone. Instructing the actuator to transmit the on signal to the ultraviolet system to switch the ultraviolet system to the on condition includes rotating the drill string in a predetermined on signal pattern.

In alternate embodiments, after exposing the loss circulation material to the ultraviolet light, the actuator can be instructed to transmit an off signal to the ultraviolet system to switch the ultraviolet system to an off condition by rotating the drill string in a predetermined off signal pattern.

In other alternate embodiments, the photo-initiator can be a benzyl dimethyl acetal, and exposure to the ultraviolet irradiation by the ultraviolet system can cause the benzyl dimethyl acetal to generate a free radical. The oligomer can be a polyacrylate and the monomer can be a styrene. Exposure to the ultraviolet irradiation by the ultraviolet system can trigger a polymerization reaction of the styrene and the polyacrylate. A cross-linked polymer can be formed within the lost circulation zone and drilling of the subterranean well can be ceased until the cross-linked polymer has hardened and set within the lost circulation zone. After the cross-linked polymer has hardened and set within the lost circulation zone, drilling of the subterranean well can be resumed, and drilling can occur from a position uphole of the lost circulation zone to a position downhole of the lost circulation zone.

In yet other alternate embodiments, the oligomer can be a resin that is an unsaturated polyester resin, acrylated epoxy resin, acrylated polyurethane epoxy resin, acrylated styrene resin, and acrylated ether resin. The ultraviolet system can include a light emitting diode type ultraviolet light source. The actuator can be a tubular actuator assembly, and the method can include securing the tubular actuator assembly to a downhole end of a j oint of the drill string. The ultraviolet system can be a tubular ultraviolet assembly that is located downhole of the tubular actuator assembly, and the method can further include securing a drill bit assembly to a downhole side of the tubular ultraviolet assembly.

In still another alternate embodiment, the actuator can be a tubular actuator assembly having an internal pipe member with a segment formed of a first material. An external pipe member can circumscribe the internal pipe member. A bearing can be positioned between the internal pipe member and the external pipe member, the bearing formed of a second material. The first material can be reactive to the second material. Instructing the actuator to transmit the on signal to the ultraviolet system can include rotating the external pipe member relative to the internal pipe member and interpreting a pattern of a reaction of the segment as the bearing rotates past the segment.

A second aspect of the present invention provides a system for sealing a lost circulation zone of a subterranean well includes a drill string having an ultraviolet system, an actuator, and a fluid flow path. The actuator is operable to transmit an on signal to the ultraviolet system to switch the ultraviolet system to an on condition. In the on condition the ultraviolet system generates ultraviolet light directed towards the fluid flow path of the drill string. The system further includes a loss circulation material for delivery into the fluid flow path of the drill string. The loss circulation material has an oligomer, a monomer, and a photo-initiator operable to be activated upon exposure to an ultraviolet irradiation by the ultraviolet system. The system further includes a predetermined on signal pattern defined by rotation of the drill string.

In alternate embodiments, the predetermined on signal pattern can be operable to instruct the actuator to transmit the on signal to the ultraviolet system to switch the ultraviolet system to the on condition. A predetermined off signal pattern can be defined by rotation of the drill string. The predetermined off signal pattern can be operable to instruct the actuator to transmit an off signal to the ultraviolet system to switch the ultraviolet system to an off condition.

In other alternate embodiments, the photo-initiator can be a benzyl dimethyl acetal that is operable to generate a free radical when exposed to the ultraviolet irradiation by the ultraviolet system. The oligomer can be a polyacrylate and the monomer can be a styrene. Exposure to the ultraviolet irradiation by the ultraviolet system can be operable to trigger a polymerization reaction of the styrene and the polyacrylate.

In still other alternate embodiments, the system can further include a cross-linked polymer set within the lost circulation zone, the cross-linked polymer including the oligomer, and the monomer. The ultraviolet system can include a light emitting diode type ultraviolet light source. The actuator can be a tubular actuator assembly secured to a downhole end of a joint of the drill string. The ultraviolet system can be a tubular ultraviolet assembly that is located downhole of the tubular actuator assembly and a drill bit assembly can be secured to a downhole side of the tubular ultraviolet assembly.

In yet other alternate embodiments, the actuator can be a tubular actuator assembly having an internal pipe member with a segment formed of a first material. An external pipe member can circumscribe the internal pipe member. A bearing can be positioned between the internal pipe member and the external pipe member, the bearing formed of a second material. The first material can be reactive to the second material. A pattern of a reaction of the segment can be defined as the external pipe member is rotated relative the internal pipe member and the bearing rotates past the segment. The pattern of the reaction can be interpretable to instruct the actuator to transmit the on signal to the ultraviolet system.

So that the manner in which the above-recited features, aspects and advantages of the disclosure, as well as others that will become apparent, are attained and can be understood in detail, a more particular description of the embodiments of the disclosure briefly summarized above may be had by reference to the embodiments thereof 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, therefore, not to be considered limiting of the disclosure's scope, for the disclosure may admit to other equally effective embodiments.

The Specification, which includes the Summary of Disclosure, Brief Description of the Drawings and the Detailed Description, and the appended Claims refer to particular features (including process or method steps) of the disclosure. Those of skill in the art understand that the disclosure includes all possible combinations and uses of particular features described in the Specification. Those of skill in the art understand that the disclosure is not limited to or by the description of embodiments given in the Specification. The inventive subject matter is not restricted except only in the appended Claims.

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 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 relates 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.

Spatial terms describe the relative position of an object or a group of objects relative to another object or group of objects. The spatial relationships apply along vertical and horizontal axes. Orientation and relational words including "uphole" and "downhole"; "above" and "below" and other like terms are for descriptive convenience and are not limiting unless otherwise indicated.

Where the Specification or the appended Claims provide a range of values, 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, or can be otherwise associated with hydrocarbon development activities.

Drill string <NUM> can extend into and be located within wellbore <NUM>. Drill string <NUM> can include tubular member <NUM> and bottom hole assembly <NUM>. Tubular member <NUM> can extend from earth's 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>.

Drill string <NUM> can further include ultraviolet system <NUM>, actuator <NUM>, and fluid flow path <NUM>. In the example embodiment of <FIG>, fluid flow path <NUM> is a central bore of the tubular members that make up drill string <NUM>. Actuator <NUM> and ultraviolet system <NUM> are separate systems that can be seamlessly integrated with other downhole tools, devices, and instruments so that actuator <NUM> and ultraviolet system <NUM> do not displace existing drilling portfolios.

Wellbore <NUM> can be drilled from surface <NUM> and into and through various formation zones <NUM> of subterranean formations. Formation zones <NUM> can include layers of reservoir that are production zones, or that are non-production zones. Formation zones <NUM> can also include a problem zone such as lost circulation zone <NUM>. In embodiments, lost circulation zone <NUM> can be uphole of or downhole of production zones.

The formation zones <NUM> can be at an elevation of uncased open hole bore <NUM> of subterranean well <NUM>. Drill string <NUM> can pass though cased bore <NUM> of subterranean well <NUM> in order to reach uncased open hole bore <NUM>. Alternately, the entire wellbore <NUM> can be an uncased open hole bore.

Looking at <FIG>, actuator <NUM> is a tubular actuator assembly. The tubular actuator assembly can be secured to a downhole end of a joint <NUM> of drill string <NUM>. The actuator assembly can have bore <NUM> that is aligned with a bore of joint <NUM> to form a part of fluid flow path <NUM> of drill string <NUM>.

The tubular actuator assembly can include internal pipe member <NUM> and external pipe member <NUM>. External pipe member <NUM> can be secured to the downhole end of a joint <NUM> of drill string <NUM>. External pipe member <NUM> can have an outer diameter that is substantially similar or the same as the outer diameter of a joint <NUM> of drill string <NUM>.

Internal pipe member <NUM> can be supported within external pipe member <NUM> so that external pipe member <NUM> circumscribes internal pipe member <NUM>. Internal pipe member <NUM> can, for example, be supported within external pipe member <NUM> between uphole support <NUM> and downhole support <NUM>. Uphole support <NUM> and downhole support <NUM> can extend radially inward from an inner diameter surface of external pipe member <NUM>.

Bearings <NUM> can be positioned between internal pipe member <NUM> and external pipe member <NUM>. End bearings <NUM> can be located between an uphole end of internal pipe member <NUM> and uphole support <NUM>, and also can be located between a downhole end of internal pipe member <NUM> and downhole support <NUM>. Side bearings <NUM> can be located between an outer diameter surface of internal pipe member <NUM> and an inner diameter surface of external pipe member <NUM>. Bearings <NUM> can rotate with external pipe member <NUM> about a central axis of external pipe member <NUM>. As an example, bearings <NUM> can be retained with external pipe member <NUM> by conventional bearing retention means.

Internal pipe member <NUM> includes segments <NUM>. In embodiments, there may be only one segment <NUM>. In alternate embodiments there is an array of segments <NUM> spaced around a surface of internal pipe member <NUM>. Segments <NUM> are positioned so that segments <NUM> are aligned with bearings <NUM>. As an example, segment <NUM> can be located on an outer diameter surface of internal pipe member <NUM> and can be axially aligned with a side bearing <NUM>. In alternate embodiments, segment <NUM> can be positioned at an uphole surface or downhole surface of internal pipe member <NUM> and can be radially aligned with an end bearing <NUM>.

Segment <NUM> can be formed of a first material and bearing <NUM> can be formed of a second material. The first material can be reactive to the second material. In an embodiment of the disclosure, as drill string <NUM> is rotated external pipe member <NUM> will rotate relative to internal pipe member <NUM>. As drill string <NUM> is rotated, external pipe member <NUM> can rotate with drill string <NUM> and internal pipe member <NUM> can remain static. As bearing <NUM> rotates past segment <NUM>, a reaction of the first material of segments <NUM> to the second material of bearing <NUM> can be sensed. As an example, the first material can have an opposite polarity as the second material. Alternately, the first material can be a piezoelectric material and the second material can cause a mechanical stress on the first material.

In order to instruct the actuator to transmit a signal to ultraviolet system <NUM>, drill string <NUM> can be rotated from the surface so that external pipe member <NUM> rotates relative to internal pipe member <NUM> in a predetermined pattern. The pattern can include, for example, a number of turns of drill string <NUM>, a speed or rate of rotation of drill string <NUM>, or a direction of rotation of drill string <NUM>.

The reaction of the first material of segments <NUM> to the second material of bearing <NUM> that is sensed as bearing <NUM> rotates past segment <NUM> and can be converted to a digital signal for interpretation by an electronics package <NUM> of tubular actuator assembly. Electronics package <NUM> can include a digital logic circuit for signal interpretation and can include an actuator system transceiver for signaling ultraviolet system <NUM> based on the instructions received by way of the predetermined pattern of the rotation of drill string <NUM>.

As an example, one predetermined pattern of rotation of drill string <NUM> can be an instruction to actuator <NUM> to send an on signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an on condition. As another example, another predetermined pattern of rotation of drill string <NUM> can be an instruction to actuator <NUM> to send an off signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an off condition.

Looking at <FIG>, ultraviolet system <NUM> is a tubular ultraviolet assembly that is located downhole of the tubular actuator assembly. In the example embodiment of <FIG>, the tubular ultraviolet assembly is secured to a downhole end of the tubular actuator assembly. In alternate embodiments, the tubular ultraviolet assembly can be spaced apart from ultraviolet system <NUM> by a joint of drill pipe or by other downhole tools or equipment.

A drill bit assembly can be secured to a downhole side of the tubular ultraviolet assembly. It is desirable to have the tubular ultraviolet assembly proximate to the drill bit, including directly adjacent to the drill bit, so that the loss circulation material passes through the tubular ultraviolet assembly immediately before exiting a downhole end of drill string <NUM>. In this way the chance of loss circulation material becoming hardened within drill string <NUM> is minimized.

The tubular ultraviolet assembly is an elongated tubular member with a bore that is in fluid communication with bore <NUM> of tubular actuator assembly and with a bore of drill string <NUM> to form a part of fluid flow path <NUM> of drill string <NUM>. The tubular ultraviolet assembly can have an outer tubular member that is secured to a member of drill string <NUM> that is adjacent to the tubular ultraviolet assembly uphole of the tubular ultraviolet assembly, and to a member of drill string <NUM> that is adjacent to the tubular ultraviolet assembly downhole of the tubular ultraviolet assembly.

The tubular ultraviolet assembly includes ultraviolet source <NUM>. Ultraviolet source <NUM> directs ultraviolet light in a direction towards the fluid flow path <NUM> of drill string <NUM>. In the example embodiments of <FIG>, ultraviolet source <NUM> directs ultraviolet light in a direction radially inward towards a central axis of the tubular ultraviolet assembly, which is the fluid flow path of drill string <NUM>.

When ultraviolet system <NUM> is in the on condition, ultraviolet source <NUM> is generating ultraviolet light. In an example embodiment, when ultraviolet system <NUM> is in the on condition an alternating current is applied to ultraviolet source <NUM>, and a selected frequency and wave length of ultraviolet light is created by an ultraviolet lamp. As an example, the ultraviolet light can have a wavelength in a range of <NUM> to <NUM>, the wavelength being dependent on the work to be performed. As an example, ultraviolet system <NUM> can provide shortwave ultraviolet light with a wavelength of <NUM> to <NUM> for top surface curing. Alternately ultraviolet system <NUM> can provide medium range wavelength ultraviolet light with a wavelength of <NUM> to <NUM> for mid depth penetration curing. Alternately ultraviolet system <NUM> can provide longwave ultraviolet light with a wavelength of <NUM> to <NUM> for deeper penetration curing and for cross linking applications. In an example embodiment, ultraviolet system <NUM> can be a battery powered light emitting diode (LED) type ultraviolet light source. An LED type ultraviolet lamp consumes less power and lasts a longer time compared to conventional ultraviolet lamps. The ultraviolet light source can be used to trigger polymerization or crosslinking reaction of photopolymers used as lost circulation materials. When ultraviolet system <NUM> is in the off condition, ultraviolet source <NUM> is not generating ultraviolet light.

Ultraviolet system <NUM> can further include ultraviolet system transceiver <NUM>. Ultraviolet system transceiver <NUM> can communicate with electronics package <NUM> of the tubular actuator assembly. In the example embodiment, ultraviolet system <NUM> and actuator <NUM> can communicate wireless by way of ultraviolet system transceiver <NUM> can communicate with electronics package <NUM> of the tubular actuator assembly. In alternate embodiments, ultraviolet system <NUM> and actuator <NUM> can communicate through a wired connection, such as through a wired drill pipe. An example of communication between ultraviolet system <NUM> and actuator <NUM> is actuator <NUM> sending the on signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an on condition. Another example of communication between ultraviolet system <NUM> and actuator <NUM> is actuator <NUM> sending the off signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an off condition.

Ultraviolet system <NUM> can further include power source <NUM>. Power source <NUM> can be, for example, a battery. Power source <NUM> can have sufficient stored power to allow for operation of ultraviolet system <NUM> over the duration of a drilling operation.

When in the on position, ultraviolet system <NUM> can direct ultraviolet light towards a loss circulation material that is delivered in the fluid flow path <NUM> of drill string <NUM>. After passing through ultraviolet system <NUM>, the loss circulation material can be delivered to lost circulation zone <NUM> (<FIG>).

Looking at <FIG>, the loss circulation material <NUM> can include oligomer <NUM>, monomer <NUM>, and photo-initiator <NUM>. The loss circulation material can include a "responsive" material. As used in this disclosure a "responsive" material is a material that undergoes reversible or irreversible chemical changes in response to an applied external stimulus, such as irradiation by ultraviolet light. As an example, photo-initiators are sensitive to ultraviolet light and generate free radicals upon irradiation by ultraviolet light. The generated free radical will excite the monomer which will either polymerize or cross link the oligomer upon which the loss circulation material becomes thick, will harden, and will eventually set. Fillers <NUM> can also be used in the loss circulation material to reduce shrinkage due to polymerization. As an example, the filler could be a silica. Alternately, the filler could be barite, calcium carbonate, ilmenite, hematite, or fly ash.

If loss circulation material <NUM> is not exposed to the ultraviolet light, loss circulation material <NUM> can remain in its fluid or flowable form indefinitely. This will mitigate the risk of the loss circulation material <NUM> setting prematurely, such as setting within drill string <NUM>.

Looking at <FIG>, in an example embodiment, oligomer <NUM> is a polyacrylate. In alternate embodiments, oligomer <NUM> can be a resin. For example, oligomer <NUM> can be unsaturated polyester resin (<FIG>), acrylated epoxy resin (<FIG>), acrylated polyurethane epoxy resin (<FIG>), acrylated styrene resin (<FIG>), or acrylated ether resin (<FIG>).

In the example embodiment of <FIG>, monomer <NUM> is a styrene. Alternately, monomer <NUM> can be diethylenetriamine, triethylentetraamine, or tetraethylenepentamine.

Photo-initiators are generally either an ionic or a free radical photo-initiator. The selection of a photo-initiator is typically dependent on the type of polymerization reaction between the monomer and the oligomer. In example embodiments, photo-initiator <NUM> can be an onium salt, an organometallic compound and pyridinium salt, or a benzophenone, benzyl dimethyl acetal. In the example embodiment of <FIG>, photo-initiator <NUM> is a benzyl dimethyl acetal. In the example of <FIG>, upon ultraviolet irradiation, a free radical is generated by the benzyl dimethyl acetal which triggers the free radical polymerization reaction of styrene and polyacrylates to form cross-linked polymer <NUM>.

In an example of operation, looking at <FIG>, drill string <NUM> that includes ultraviolet system <NUM> and actuator <NUM> can be used to drill subterranean well <NUM>. As drill string <NUM> forms subterranean well <NUM>, drilling fluid <NUM> can be circulated downhole through drill a fluid flow path <NUM> of drill string <NUM>, can exit through bottom hole assembly <NUM>, and return uphole in the annulus.

Looking at <FIG>, during drilling operations, drill string <NUM> could encounter lost circulation zone <NUM>. When the downhole end of bottom hole assembly has drilled into lost circulation zone <NUM>, drilling fluid <NUM> can flow into lost circulation zone <NUM>. Because drilling fluid <NUM> is flowing into lost circulation zone <NUM>, a lesser portion of drilling fluid <NUM> is being returned through annulus <NUM> to the surface. In order to address such a loss of circulation fluid, a loss circulation material can be used to plug lost circulation zone <NUM>.

Looking at <FIG>, before introducing the loss circulation fluid into drill string <NUM>, actuator <NUM> can be instructed to transmit an on signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an on condition. In the on condition ultraviolet system <NUM> generates ultraviolet light directed towards fluid flow path <NUM> of drill string <NUM>.

In order to provide a predetermined on signal to instruct actuator <NUM>, drill string <NUM> can be rotated from the surface so that external pipe member <NUM> rotates relative to internal pipe member <NUM> in a predetermined pattern. As an example, drill string <NUM> can be rotated in a specific direction for specific number of times for actuator <NUM> to generate a unique on signal pattern which is then interpreted by digital logics to turn on battery powered ultraviolet system <NUM>. The digital logics can be coded to respond to one or more unique signal patterns. Actuator <NUM> can communicate with ultraviolet system <NUM> wirelessly or through a wired drill pipe.

Looking at <FIG>, after ultraviolet system <NUM> has been switched to an on condition loss circulation material <NUM> can be delivered into fluid flow path <NUM> of drill string <NUM>. As loss circulation material <NUM> passes through fluid flow path <NUM> of drill string <NUM>, loss circulation material <NUM> displaces drilling fluid <NUM>. Drilling fluid <NUM> can flow through annulus <NUM> to the surface or can be lost to lost circulation zone <NUM>.

As loss circulation material <NUM> passes through ultraviolet system <NUM>, loss circulation material <NUM> is exposed to ultraviolet light that irradiates loss circulation material <NUM>, to generate free-radicals from photo-initiator <NUM>. These free radicals trigger the monomer <NUM> to undergo a cross-linking or polymerization reaction with oligomer <NUM> (<FIG>).

Looking at <FIG>, drilling fluid <NUM> can be delivered into fluid flow path <NUM> of drill string <NUM> to displace loss circulation material <NUM>. After loss circulation material <NUM> passes through ultraviolet system <NUM>, loss circulation material <NUM> is delivered to lost circulation zone <NUM>. Because loss circulation material <NUM> has been irradiated with ultraviolet light, the resulting cross-linking or polymerization reaction can form cross-linked polymer <NUM> within lost circulation zone <NUM>. Drilling of subterranean well <NUM> is ceased until cross-linked polymer <NUM> has hardened and set within lost circulation zone <NUM>.

After all of loss circulation material has passed through ultraviolet system <NUM>, actuator <NUM> can be instructed to transmit an off signal to ultraviolet system <NUM> to switch ultraviolet system <NUM> to an off condition. In the off condition ultraviolet system <NUM> does not generate ultraviolet light.

In order to provide a predetermined off signal to actuator <NUM>, drill string <NUM> can be rotated from the surface so that external pipe member <NUM> rotates relative to internal pipe member <NUM> in a predetermined pattern. As an example, drill string <NUM> can be rotated in a specific direction for specific number of times for actuator <NUM> to generate a unique off signal pattern which is then interpreted by digital logics to turn on battery powered ultraviolet system <NUM>. The digital logics can be coded to respond to one or more unique signal patterns. Actuator <NUM> can communicate with ultraviolet system <NUM> wirelessly or through a wired drill pipe.

Looking at <FIG>, after cross-linked polymer <NUM> has hardened and set within lost circulation zone <NUM>, drilling of subterranean well <NUM> can resume. Drill string <NUM> can be rotated so that the drill bit assembly of bottom hole assembly <NUM> continues the drilling of subterranean well <NUM>. The drill bit can drill through cross-linked polymer <NUM> from a position uphole of lost circulation zone <NUM> (<FIG>) to a position downhole of lost circulation zone <NUM> (Figure <NUM>) and normal drilling operations can be resumed. The drilling operation and the methods for sealing a lost circulation zone of a subterranean well in accordance with embodiments of this disclosure can be managed through an Industrial Internet of Things (IIoT) platform.

Therefore, embodiments of this disclosure provide systems and methods for curing lost circulation that can ensure effective placement and activation of loss circulation material at the loss circulation zone, thereby minimizing or eliminating any error in the placement and activation of the loss circulation material. In embodiments of this disclosure an actuator is located downhole and can be controlled from the surface. The ultraviolet system is placed adjacent to the drill bit and can trigger the polymerization or crosslinking reaction of the loss circulation material. The loss circulation material thickens and hardens in very short period of time and can seal off the fractures or vugs causing lost circulation.

Claim 1:
A method for sealing a lost circulation zone (<NUM>) of a subterranean well (<NUM>), the method including:
extending a drill string (<NUM>) into the subterranean well, the drill string having an ultraviolet system (<NUM>), an actuator (<NUM>), and a fluid flow path (<NUM>);
instructing the actuator to transmit an on signal to the ultraviolet system to switch the ultraviolet system to an on condition, where in the on condition the ultraviolet system generates ultraviolet light directed towards the fluid flow path of the drill string;
delivering a loss circulation material (<NUM>) into the fluid flow path of the drill string, the loss circulation material having an oligomer (<NUM>), a monomer (<NUM>), and a photo-initiator (<NUM>);
exposing the loss circulation material to the ultraviolet light to activate the loss circulation material; and
delivering the loss circulation material to the lost circulation zone;
where instructing the actuator to transmit the on signal to the ultraviolet system to switch the ultraviolet system to the on condition includes rotating the drill string in a predetermined on signal pattern.