Fluorescent metal-organic frameworks

Abstract

A composition comprising a fluorescent metal-organic framework (MOF) and a drilling fluid is provided. The MOF includes a porous crystal structure and a fluorescence source. The method includes introducing the MOF into the drilling fluid and circulating the drilling fluid through the well during a drilling operation that produces the formation debris such that the fluorescent MOF interacts with the formation debris, thereby producing a marked debris. The method further includes collecting returned cuttings from the circulating drilling fluid at the surface of the well, detecting the presence of a fluorescent MOF on the returned cuttings to identify marked cuttings, and associating the marked cuttings with a drilling depth in the well at an instant during the drilling operation.

Description

Background Art

[0001] Drilling fluid, also known as "drilling mud" or simply "mud", is used to facilitate the drilling of boreholes in the subsurface, such as oil and gas wells. The primary functions of drilling fluid include providing hydrostatic pressure to prevent the ingress of formation fluids into the borehole, thereby keeping the drill bit cool and clean during drilling, entraining drill cuttings, and suspending drill cuttings during drilling pauses and as the drilling assembly moves in and out of the borehole. Drill cuttings, also known as "cuttings" or "formation cuttings", are rock fragments generated by the drill bit as it advances along the borehole. Mud logging is the creation of a log of the borehole by examining the cuttings brought to the surface by circulating the drilling mud.

[0002] A taggant or "label" is a chemical or physical marker added to a material to allow various forms of testing of the tagged material. A tag detector can be used to detect the tag. Physical tags can take many different forms, but are typically tiny in size, added to the material at low levels, and easily detected. Tags can be encoded based on specific properties (such as optical, chemical, electrical, or mechanical properties) to act as a virtual "fingerprint." Examples of coded tags include tiny metal tags (e.g., between 0.3 and 1.0 mm) with unique multi-digit alphanumeric identification codes. For example, the identification code can be etched into the optically variable (holographic) substrate of the tag. The tag can be suspended in a UV-sensitive transparent adhesive that can be brushed or sprayed onto any item for authentication or other security purposes. Summary of the invention

[0003] This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In one aspect, embodiments disclosed herein relate to a composition comprising a fluorescent metal-organic framework (MOF, or metal-organic framework) and a drilling fluid.

[0005] In another aspect, embodiments herein relate to a method comprising introducing a MOF into a drilling fluid. The drilling fluid can then be circulated through the well during a drilling operation that produces formation cuttings, such that the fluorescent MOF interacts with the formation cuttings to produce labeled cuttings. The method also includes collecting returned cuttings from the circulating drilling fluid at the surface of the well, and detecting the presence of the fluorescent MOF on the returned cuttings to identify the labeled cuttings. The identified labeled cuttings can be associated with a drilling depth in the well at a time during the drilling operation.

[0006] Other aspects and advantages of the claimed subject matter will be apparent from the following description and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A system according to an embodiment of the present disclosure is shown.

[0008] Figure 2 is a block flow diagram of a method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0009] Now will be described in detail with reference to the accompanying drawings the specific embodiments of the present disclosure. For consistency, the same elements in various figures are represented by the same reference numerals.

[0010] In the following detailed description of the embodiments of the present disclosure, a large number of specific details are set forth to provide a more thorough understanding of the present disclosure. However, it will be appreciated by those of ordinary skill in the art that the present disclosure can be implemented without these specific details. In other cases, well-known features are not described in detail to avoid unnecessarily complicating the description.

[0011] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in the application). The use of ordinal numbers does not imply or create any particular ordering of elements, nor does it limit any element to only a single element, unless explicitly disclosed as such, such as using the terms "before," "after," "single," and other such terms. Instead, the use of ordinal numbers is to distinguish between elements. For example, a first element is different from a second element, and a first element may encompass more than one element, and may be located after (or before) a second element in the ordering of elements.

[0012] Embodiments disclosed herein generally relate to a composition comprising a fluorescent metal-organic framework (MOF) and a drilling fluid. The MOF comprises a porous crystalline structure and a fluorescent source (which can be incorporated into or present as part of the extended network of the MOF). In some cases, the fluorescent source can be otherwise attached to the MOF framework.

[0013] Methods for determining the drilling depth of formation cuttings using the composition are also described. Fluorescent MOFs according to one or more embodiments can be injected into a drilling fluid during a drilling operation and travel downhole. The disclosed fluorescent MOF can interact with the downhole formation and, in some cases, attach to the drilling cuttings generated during the drilling process. Thus, drilling cuttings can be "tagged" with the fluorescent MOF described herein. Fluorescent MOF tags with different fluorescence emission wavelengths, i.e., tags that emit different colors, can be controllably introduced at different drilling depths. When the tagged cuttings are returned to the surface via the circulating drilling fluid, they can be identified primarily based on the fluorescence emission from the tag. This fluorescence can be associated with the associated drilling depth, and the cuttings can be identified by the depth at which they originated. Thus, the disclosed composition can be used to determine the drilling depth of various drilling cuttings.

[0014] In addition, fluorescent MOF tags with different emission wavelengths can also have different powder x-ray diffraction (PXRD) spectra and molecular weight fragmentation spectra. Metal-organic frameworks (MOFs) are inorganic and organic hybrid polymer coordination compounds constructed by connecting metal ions or clusters to organic ligands, thereby providing a porous but rigid crystal structure. The crystal structure is adjustable by selecting the organic linker (organic linker, or organic linking chain) in the metal-organic framework. Therefore, the crystal structure of the MOF unit cell and the molecular weight of its organic linker can be used as an additional recognition parameter, thereby providing a complex recognition matrix for these fluorescent tags.

[0015] Drilling system

[0016] Figure 1 A schematic diagram of a system 100 is shown in accordance with one or more embodiments of the present disclosure, in which the compositions and methods disclosed herein may be used. In one or more embodiments, the Figure 1 One or more of the modules and / or elements shown in . Figure 1 As shown, system 100 may include well system 110, cuttings return and detection system 120, analysis and control system 130, and drilling fluid marking system 140, which may be in direct and indirect communication with each other.

[0017] Well system 110 may include a well 111 drilled through an underground formation ("formation") 112 to a hydrocarbon-bearing layer of the formation below the earth's surface ("surface") 113. Formation 112 may include different rock layers having different properties, such as varying degrees of permeability, porosity, capillary pressure, and resistivity. In the event that well system 110 is operated as a production well, well system 110 may facilitate the extraction (or "production") of hydrocarbons from the hydrocarbon-bearing layers of formation 112. As well 111 is drilled through formation 112, portions of the well may be cased with casing (extending from the surface of the well) or liner (extending downhole from one end of a previously installed casing or liner) to line the wellbore wall. The terms "open hole," "borehole," and "wellbore" may be used interchangeably and refer to the uncased portion of a well.

[0018] In some embodiments, the well system 110 may include a drilling rig 114 located above the opening of the well 111, a well subsurface system 115, a well surface system 116, and a well control system 117. The well control system 117 may control various operations of the well system 110, such as well production operations, well drilling operations, well completion operations, well maintenance operations, and reservoir monitoring, evaluation, and development operations. In some embodiments, the well control system 117 may include a computer system that is the same or similar to the analysis and control system 130, which will be described in more detail below.

[0019] The drilling rig 114 may hold equipment for drilling a borehole to form the well 111. Major components of the drilling rig 114 may include a drilling fluid tank, a drilling fluid pump (e.g., a drilling rig mixing pump), a derrick or mast, a drawworks, a rotary table or top drive, a drill string, power generation equipment, and auxiliary equipment.

[0020] Well 111 may include a borehole extending from surface 113 into formation 112. The upper end of well 111 (terminating at surface 113) may be referred to as the "up-hole" end of well 111, while the lower end of the well (terminating in formation 112) may be referred to as the "down-hole" end of well 111.

[0021] In some embodiments, during operation of the well system 110, the well control system 117 may collect and record well data for the well system 110 (e.g., from monitoring devices (e.g., logging tools) lowered into the well during monitoring operations (e.g., during field logging operations) or from drilling operations). For example, during drilling operations of the well 111, the well data may include mud properties, flow rates, drilling volumes, and penetration rates, formation characteristics, etc. In some embodiments, the well data may be recorded in real time and may be available for review or use within seconds, minutes, or hours after the condition is sensed (e.g., measurements may be available within 1 hour after the condition is sensed). In such embodiments, the well data may be referred to as "real-time" well data. The real-time well data may enable the operator of the well 111 to assess the relative current state of the well system 110 and make real-time decisions regarding the development of the well system 110 and the reservoir, such as adjusting the drilling fluid as needed and regulating the production flow from the well.

[0022] In some embodiments, the well surface system 116 may include a wellhead mounted at the "uphole" end of the well, where or near the well terminates at the surface 113, wherein the wellhead may include a rigid structure for supporting (or "hanging") casing and production tubing extending into the well 111. Drilling fluid directed from the well to the surface may flow through the wellhead after leaving the well 111 and the well underground system 115, which includes, for example, casing, production tubing, a drill string, and a bottom hole assembly (including a drill bit). Such fluids may carry the disclosed fluorescent MOF downhole, as will be explained in more detail below. In some embodiments, the well surface system 116 may include a flow regulating device that is operable to control the flow of a substance flowing into and out of the well 111. For example, the well surface system 116 may include one or more valves 118 that are operable to control the flow of fluid from the well 111. For example, valve 118 can be fully opened to allow unrestricted flow of return drilling material from well 111, valve 118 can be partially opened to partially restrict (or "throttle") the flow of fluid from well 111, and valve 118 can be fully closed to fully restrict (or "block") the flow of fluid from well 111 and through the well surface system 116.

[0023] In some embodiments, the well surface system 116 may include surface sensors for sensing properties of fluids passing through or otherwise located in the well surface system 116, such as pressure, temperature, and flow rate of the fluids flowing through the wellhead or other conduits of the well surface system 116 after leaving the well 111. The surface sensors may also include sensors for sensing properties of the drilling rig 114 and drilling equipment, such as drill bit depth, hole depth, hook load, rotation speed, weight on bit, etc.

[0024] During drilling operations, drilling fluid 102 may be pumped from a drilling fluid source 104, which may be supplied, for example, by truck or tank, wherein the drilling fluid source 104 may include premixed drilling fluid or separately provided components mixed on site. In some embodiments, the drilling fluid source 104 may include spent drilling fluid from a mud pit 106, which includes drilling fluid that is circulated through the well, returned to the surface, and cleaned. According to one or more embodiments of the present disclosure, a fluorescent MOF may be pumped downhole with the drilling fluid 102 and circulated through the well 111 to mark cuttings as they are formed by drilling.

[0025] The fluorescent MOF may be supplied by a tag injection assembly 141 in the tag system 140. The tag injection assembly 141 may include a plurality of tag chambers 142, each of which contains a different tag and has a valve 143 at the chamber outlet. A metering pump 144 may be in fluid communication with the chamber outlet of the tag chamber 142, so that when the tag is released from the tag chamber 142 through the associated valve 143, the tag may be metered into the drilling fluid 102. For example, when the drilling fluid 102 is pumped from the drilling fluid source 104 to the well 111, a selected tag may be released from the tag chamber 142 and metered at a selected rate by the metering pump 144 to mix with the drilling fluid 102 and flow into the well 111 with the drilling fluid 102.

[0026] The valve 143 and the metering pump 144 may be operated and controlled using a controller 145. The controller 145 may be integrated with the tag injection assembly 141, or may be remote from the tag injection assembly 141. The controller 145 may send commands to the valve 143 (e.g., to open or close the valve) and the metering pump 144 (e.g., to control the rate at which tags are metered through the pump). The controller 145 may also receive signals from the valve 143 and the metering pump, e.g., signals relaying operating status. The controller 145 may send commands to perform one or more operations designed by the analysis and control system 130. For example, the analysis and control system 130 may determine an optimized tag release operation and send instructions to the controller 145 to perform the optimized tag release operation. The controller 145 may then send commands to one or more valves 143 and metering pumps 144 to release tags from one or more tag chambers 142 at a given rate and on a schedule according to the optimized tag release operation.

[0027] One or more pumps 105 may be used to pump the mixed tag and drilling fluid into the well 111 while drilling the well. The drilling fluid 102 and tag may be pumped through a drill string extending through the well and out of a bottom hole assembly at the end of the drill string (e.g., through a drill bit). When the tag is ejected from the bottom of the drill string along with the drilling fluid, the tag may be attached to the formation being drilled. In one or more embodiments, the drill bit may press the tag into the formation, which may cause the tag to adhere to or stain portions of the formation (which then become cuttings). In some embodiments, hydraulic circulation may be the primary driving force for attaching the tag to the formation, however, the detailed interaction mechanism between the tag and the formation depends on the type of tag used and may vary (e.g., chemical interaction, physical attachment, adsorption, and / or electrostatic interaction). While drilling the formation, cuttings 103 from the formation with attached tags may be sent to the surface of the well and analyzed in a cuttings return and detection system 120.

[0028] When drilling fluid 102 and tagged cuttings 103 are pumped to the surface of well 111 during drilling operations, the returned drilling fluid can be directed via one or more conduits (e.g., a piping system) to one or more separators 121 (sometimes referred to in the industry as mud shakers) in a drilling cuttings return and detection system 120. In some embodiments, the returned cuttings can be automatically directed to the one or more separators 121 based on commands received from the well control system 117. The separator 121 can include, for example, one or more screens 122 arranged in the flow path of the returned drilling fluid to capture and separate the cuttings 103 from the drilling fluid. For example, the separator 121 can have a screen 122 positioned laterally at the upper end of the separator 121, wherein the returned drilling fluid can flow through the screen 122 after returning from the well 111. As the returning drilling fluid 102 flows through the screen 122, the rock cuttings 103 in the returning drilling fluid 102 can be captured by the screen 122, while the drilling fluid 102 flows through the screen openings. In this way, the rock cuttings 103 brought out from the drilling 111 can be captured and retained by the screen 122 in the separator 121. In some embodiments, more than one screen and / or more than one separator can be used to separate the rock cuttings from the returning drilling fluid. In some embodiments, one or more conveyors can convey the screen and / or rock cuttings along the path, for example, to move the rock cuttings to a different location for analysis.

[0029] A detection system 120 including one or more UV light sources 123 and a detection device may be used to detect the presence of tags on drilling cuttings. Figure 1 In the illustrated embodiment, the detection device is exemplified by a camera 124. In some embodiments, a UV light source 123 may be disposed at a location around the separator 121 to illuminate the rock cuttings 103 with UV light, and the camera 124 may be located above the separator 121 and positioned to take pictures of the rock cuttings 103 as they are illuminated by the UV light. Figure 1 As shown, the UV light source 123 and the camera 124 can be held at a distance above the top screen 122 of the separator 121 and positioned facing the screen 122. The UV light source 123 and the camera 124 can be positioned adjacent to or close to each other so that when the UV light source 123 illuminates the rock cuttings 103 with UV light, the camera 124 can be in a position to capture an image of the illuminated rock cuttings 103. In some embodiments, the camera 124, the UV light source 123, and the separator 121 can be integrated into one equipment unit. In some embodiments, one or more conveyors can be used to convey the captured rock cuttings 103 from the separator 121 to a separate detection system having at least one UV light source and camera.

[0030] Depending on the flow rate of the return fluid in the drilling operation and the amount of cuttings returned, the separated and captured cuttings can be moved relatively quickly through the separator 121 to allow for a continuous separation operation. To facilitate the continuous separation operation, the UV light source 123 can continuously direct UV light toward the collection of cuttings, thereby continuously illuminating the cuttings, and the camera 124 can be controlled to capture images of the illuminated cuttings at a rate commensurate with the speed of cuttings separation and removal. In some embodiments, the UV light source 123 can be controlled to operate in coordination with the camera 124, so that the operation of the UV light source 123 is timed to illuminate the collection of cuttings immediately before and during the image of the cuttings is captured by the camera 124, and wherein the coordinated operation of both the UV light source 123 and the camera 124 can be performed at a rate commensurate with the speed of cuttings separation and removal. The camera 124 can be controlled by a timer and / or using a software program to capture images when the UV light source is turned on. For example, the camera 124 can be controlled to take pictures at certain intervals (e.g., every 5 minutes, every 10 minutes, or at intervals related to the flow rate of the returning drilling fluid measured along the flow path between the well 111 and the separator 121), and the UV light source 123 can be controlled to continuously illuminate the separated rock cuttings or to illuminate the separated rock cuttings at the same picture taking interval as the camera 124.

[0031] In embodiments where a camera is used as a detection device, an image processing system 125 may be used to analyze images captured by the camera 124 and identify the percentage of tagged rock cuttings 103 (rock cuttings illuminated to the identified color under UV light) from the total captured rock cuttings 103 in the image. The image processing system 125 may be provided as part of the detection system 120, for example, where the camera 124 includes software instructions to perform image analysis on the pictures it captures to identify the tagged rock cuttings 103.

[0032] The detection data (including the identified amount of at least one tag color) can then be sent to the analysis and control system 130, as discussed in more detail below. In some embodiments, an image processing system 125 can be provided as part of the analysis and control system 130, wherein the camera 124 can send images of the captured rock cuttings 103 to the image processing system in the analysis and control system for processing and identification of the tagged rock cuttings 103. The image processing system 125 can analyze the images in real time as each image is taken. For example, in some embodiments, the image processing system 125 can analyze a first image taken by the camera 124 and identify the percentage of rock cuttings tagged with one or more tag colors before the camera 124 takes a second image.

[0033] Any available image processing software can be used to process the images captured by the camera 124 and identify the amount of at least one label color in each image. In some embodiments, the image processing software can include instructions to divide the image into discrete uniformly sized units (e.g., pixels) and compare the colors in each unit. A ratio of different color units can be calculated, which can be used to calculate the percentage of cuttings marked with a selected label color (which can be captured in the image when the cuttings are illuminated by UV light) of the total amount of cuttings detected in the image. The drilling depth that produced the formation cuttings can then be determined based on the colors identified in the collected images.

[0034] In one or more embodiments, fluorescent MOF can be extracted from the returned rock cuttings for further identification. Extraction of fluorescent MOF from the returned rock cuttings can be performed using various methods known to those skilled in the art (including dispersion, sedimentation, decantation and filtration, centrifugation and solvent thermal extraction). Due to the ordered rigid structure of MOF, fluorescent MOF tags can also be identified by their crystal structure using powder x-ray diffraction (PXRD). In some embodiments, the PXRD spectra of MOF can be used as a unique identification technique. In other embodiments, PXRD can be used in combination with UV detection to identify MOF tags. For example, after obtaining the emission wavelength in real time according to the above method, the crystal structure of fluorescent MOF can be obtained by PXRD in the laboratory. MOFs with different crystal structures will provide different PXRD spectra.

[0035] In addition to the fluorescence emission wavelength and PXRD spectra, the molecular weight fragmentation spectra of fluorescent MOF can also be obtained and used for identification. Various organic ligands can be used for MOF construction, thereby providing additional parameters for identification. The molecular weight of the organic ligand can be obtained from the molecular weight fragmentation spectra obtained using gas chromatography-mass spectrometry (GC-MS). In addition, liquid chromatography-mass spectrometry (LC-MS) can be used to determine the molecular weight of the organic ligands that make up MOF. Therefore, a complex recognition matrix that depends on emission wavelength, PXRD spectra and building block (building block, or building unit) molecular weight can be used to identify each fluorescent MOF tag. Using such a recognition matrix can improve the accuracy of labeled cuttings identification.

[0036] Fluorescent MOF compositions

[0037] As previously described, the present disclosure relates to a composition that can be used to determine the drilling depth of cuttings formed during the drilling process. The composition according to one or more embodiments of the present disclosure includes a fluorescent MOF. MOF is a porous crystalline material composed of metal ions or metal ion clusters connected by organic "linker" molecules. Herein, the terms "linker" and "ligand" can be used interchangeably to refer to organic molecules that form an extended network of MOFs together with metal ions or clusters. Various methods can be used to introduce fluorescence into MOFs, such as using fluorescent building blocks to produce the framework of MOFs, thereby covalently binding fluorescent moieties to the pores and / or channels of non-fluorescent MOF frameworks, and inserting fluorophores into the pores of MOFs. Each method can be used to provide fluorescent MOFs in the present disclosure.

[0038] Fluorescence refers to a form of luminescence that can emit light when ultraviolet light or other electromagnetic radiation is absorbed. For example, when ultraviolet light is absorbed by a fluorescent compound (also referred to as a fluorophore), the fluorescent compound can emit visible light, which can be referred to as fluorescence. Therefore, as used herein, a fluorophore is a compound that emits visible light when it absorbs electromagnetic radiation. Suitable fluorophores are fluorophores that emit fluorescence at known wavelengths on the visible light spectrum (i.e., from about 400 to about 700 nanometers) and are stable under formation conditions. As will be appreciated by those skilled in the art, fluorophores with different emission wavelengths can be selected to distinguish between different fluorophores.

[0039] As mentioned above, MOFs are organic-inorganic hybrid crystalline porous materials that include metal ions or metal ion clusters and organic linkers. Due to their porous structure, MOFs can be used in a variety of applications, and the framework of MOFs can be tuned for specific applications. For example, by adjusting the geometry and other properties of the organic linker, the size, shape, and internal surface of the MOF can be selected based on its desired use. Common organic linkers used in MOFs include terephthalic acid (1,2-benzenedicarboxylic acid), trimesic acid (benzene-1,3,5-tricarboxylic acid), and 2-methylimidazole. Similarly, metal ions can be selected based on the number of open binding sites, providing the opportunity to control the MOF topology. Commonly used metal ions in MOFs include Zn 2+ 、Co 2+ , Cu 2+ , Fe 3+ and Zr 4+ Therefore, the fluorescent MOFs of the present disclosure can be designed to have specific topologies, as well as other properties that can be tuned by selecting metal ions and / or organic linkers.

[0040] In one or more embodiments, the fluorescent MOF includes fluorescent building blocks, such as fluorescent metal clusters and / or fluorescent organic linkers. In such embodiments, the fluorescent moieties are incorporated into the interlocking extended network of the MOF. The restricted rotation and spacing of the fluorescent building blocks can prevent aggregation-induced fluorescence quenching (which is common in highly planar aromatic luminescent materials).

[0041] In embodiments where the fluorescent MOF includes fluorescent metal ions or clusters, examples of fluorescent metal ions or clusters may include, but are not limited to, ions or clusters of rare earth elements / lanthanides, actinides, and transition metals. Examples of rare earth element ions and clusters include Eu 3+ Sc 3+ , Y 3+ 、Sm 3+ 、Pm 3+ 、Nd 3+ , Pr 3+ 、Tm 3+ , Er 3+ 、Dy 3+ and combinations thereof. Transition metals that can be incorporated into the MOF extended network as metal ions or clusters include Zn 2+ 、Zr 4+ 、Co 3+ 、Ni 2+ Cr 3+ , Nb 5+ , Cu 2+ , Cu 1+ , Fe 2+ , Fe 3+ 、Ti 4+ 、Al 2+ and combinations thereof. Suitable actinides that can be included in the fluorescent MOF in the form of ions or clusters include Am 4+ , U 4+ 、Am 3+ 、Np 4+ and Np 3+ wait.

[0042] Optionally, the fluorescent MOF of the embodiment may include a fluorescent organic linker. Examples of fluorescent linkers include, but are not limited to, 1,4-benzenedicarboxylic acid and its derivatives; 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid and its derivatives; biphenyl-4,4'-dicarboxylic acid and its derivatives; 1,6-anthracene dicarboxylic acid and its derivatives; 1,1',4',1"-terphenyl-2',4,4",5'-tetracarboxylic acid (TPTC), 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane (TPPE), trans-4,4'- Stilbene dicarboxylic acid, 2,7-pyrene dicarboxylic acid and its derivatives; 1,6-pyrene dicarboxylic acid and its derivatives; 1,3,6,8-pyrene tetracarboxylic acid and its derivatives; pyrene-1-carboxylic acid and its derivatives; pyrene-2-carboxylic acid and its derivatives; 8-anilino-1-naphthalenesulfonic acid and its derivatives; porphyrine mono-, di-, tri-, tetra- and polycarboxylic acids and derivatives; phthalocyanine mono-, di-, tri-, tetra- and polycarboxylic acids and derivatives; other organic linkers and their combinations.

[0043] In one or more embodiments, the fluorescent MOF comprises a non-fluorescent MOF framework (i.e., a MOF made of non-fluorescent building blocks) that has been modified after synthesis to include a fluorescent moiety. Several families of non-fluorescent MOFs are known in the art, each exhibiting unique properties. Specifically, the Lavoisier Institute Materials (MIL) family, the zeolitic imidazolate framework (ZIF) family, and the University of Oslo (UiO) family of MOFs can be used for aqueous and oil-based samples, such as the drilling fluids of the present disclosure. Therefore, in one or more embodiments, the fluorescent moiety can be covalently attached to a non-fluorescent MOF, including but not limited to MOFs of the MIL family, the ZIF family, and the UiO family.

[0044] Organic molecules with highly conjugated structures can be used as fluorescent moieties bound to the pores of non-fluorescent MOFs. For example, aromatic, heteroaromatic and highly unsaturated compounds can be used as fluorescent moieties. Specifically, fluorescent moieties that can be bound to non-fluorescent MOFs include, but are not limited to, rhodamine dye derivatives, fluorescein derivatives, fluorescein isothiocyanate, uranin derivatives, eosin derivatives, BODIPY dye derivatives, porphyrin derivatives, phthalocyanine derivatives and combinations thereof.

[0045] As described above, post-synthesis modification can be used to attach the fluorescent moiety to MOF. There is no particular restriction on the post-synthesis modification (PSM) method for attaching the fluorescent moiety to MOF. As will be appreciated by those skilled in the art, there are various post-synthesis modification methods that can be used to provide fluorescent MOFs according to the present disclosure. For example, in one or more embodiments, MOF can undergo covalent PSM, ionic PSM, coordinated PSM or inorganic PSM to include a fluorescent moiety. Covalent PSM can involve forming a covalent bond between a functional group included on the organic linker of MOF and the fluorescent moiety. For example, fluorescein isothiocyanate can react with the hydroxyl group of the organic linker in MOF to covalently attach the fluorescent moiety. MOFs undergoing coordinated PSM can cause the fluorescent moiety to coordinate with the central metal ion or cluster of MOF. An example of an inorganic PSM is metal exchange in a MOF metal cluster, which may occur when MOF is exposed to a solution of different metal salts. Ionic PSM can occur via ion exchange between counterions and ionic MOFs. In one or more special embodiments, the fluorescent moiety is attached to MOF via covalent post-synthesis modification.

[0046] In one or more embodiments, the fluorescent MOF includes at least one fluorophore that is physically adsorbed to the pores and / or channels of the non-fluorescent MOF. Since the hybrid network of the MOF includes both metal clusters and organic ligands, the MOF generally exhibits strong interactions required for adsorption of fluorophores, such as hydrophobic / hydrophilic interactions and electrostatic interactions.

[0047] In one or more embodiments, examples of the types of fluorophores that are physically adsorbed to the MOF include fluorescent dyes, quantum dots, emitting beads, fluorescent microspheres, fluorescent polymers, lanthanide ions, metal complexes, rare earth elements, and combinations thereof. Examples of fluorophores can include, but are not limited to, polymers covalently modified with fluorescent dye moieties, polymers with fluorescent dyes inserted inside cross-linked polymer structures, fluorescent polymer microspheres (such as, for example, and ), fluorescent glass microspheres, fluorescent glass beads, fluorescent ceramic particles, fluorescent mineral particles, fluorescent proteins (such as green fluorescent protein), fluorescent quantum dots, rare earth metal derivatives and lanthanide compounds and fluorescent porous organic polymers. Examples of fluorescent dyes include, but are not limited to, fluorescein and rhodamine B.

[0048] MOFs with inserted fluorophores can be designed to have particularly porous structures so that the selected fluorophores can easily diffuse into the MOF. For example, a MOF with a hollow structure can be prepared and exposed to a dispersion of quantum dots, so that quantum dots of matching size are adsorbed and diffused into the pores and channels of the MOF.

[0049] The fluorescent MOF of the embodiment can have a surface functionality suitable for attachment to drilling cuttings. The fluorescent MOF tag can be physically or chemically adsorbed to the cuttings. For example, the fluorescent MOF can diffuse into the pores of the drilling cuttings. In addition, the MOF tag can electrostatically interact with the charged surface of the cuttings and thus chemically adsorb to the cuttings.

[0050] Downhole, MOF may be exposed to harsh conditions such as high temperature and low pressure. In one or more embodiments, fluorescent MOF can be protected from the destructive effects of the downhole environment. Therefore, according to one or more embodiments, fluorescent MOF can be incorporated into a composite material or protected with various materials. For example, fluorescent MOF can be encapsulated in a glass, ceramic or polymer matrix to form a composite material. In one or more embodiments, MOF can be trapped inside porous ceramics or silica. In some embodiments, a polymer shell can be grafted onto the surface of MOF. In other embodiments, MOF can be dispersed in a polymer matrix (such as epoxy resin). Still other embodiments may include soaking a polymer or surfactant in a MOF solution to successfully incorporate MOF into a polymer composite.

[0051] For example, in order to trap MOF in the pores of silica, a dual solvent strategy can be used. The dual solvent strategy is based on a hydrophobic solvent and a hydrophilic solution (containing a MOF precursor with a volume equal to or less than the pore volume of the silica support). Using this strategy, MOF can be selectively trapped in the channels of the silica support. In another exemplary embodiment, the MOF particles can be suspended in a volatile solvent and mixed with a solution of a dissolved polymer until both are uniformly dispersed. This mixture can then be cast into a desired shape, after which the solvent is evaporated, resulting in a MOF in a polymer matrix.

[0052] In some embodiments, the polymer matrix in the composite material can be made of a composite material of block-co-polymers, alternating polymers, cross-linked polymers, star polymers, branched polymers, dendritic polymers or interwoven polymer fibers. For example, the composite material can be made of polymers, including but not limited to polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene imine (PEI), polyimides (PI), polymethacrylates (PMA), polyvinylidene fluoride, polyvinyl pyrrolidone, polysulfones, polydimethylsiloxane, polyacrylonitrile and polyamides, etc.

[0053] Fluorescent MOF according to one or more embodiments may also include magnetic particles. Examples of suitable magnetic particles include, but are not limited to, Co, Mn, Ni and Fe clusters. Co, Mn, Ni and Fe oxides and alloys may also be used. In one or more particular embodiments, the fluorescent MOF includes magnetic iron oxide nanoparticles, superparamagnetic iron oxide nanoparticles or a combination thereof. Similar to fluorophores, magnetic particles may be encapsulated in the pores of the MOF. Magnetic particles may allow the fluorescent MOF to be separated from drilling cuttings using a magnetic field. This provides a method for optionally recovering and reusing the fluorescent MOF.

[0054] Method for preparing fluorescent MOF

[0055] The present disclosure also relates to methods for making the disclosed fluorescent MOF. As previously described, fluorescence can be introduced into the MOF by a variety of methods. Depending on the type of extended network used to make the MOF, the method for preparing the fluorescent MOF can be different. For example, a MOF with a fluorescent organic linker incorporated into the framework can be prepared by reacting a suitable organic linker with a metal salt to produce a crystalline fluorescent MOF. Methods for basic MOFs will be known to those skilled in the art. Various examples of methods for forming MOFs according to embodiments of the present disclosure are provided below.

[0056] In one or more embodiments, the method for preparing MOF includes the use of fluorescent building blocks, such as fluorescent metal ions or clusters, and / or fluorescent organic linkers as described above. In such a method, the fluorescent building blocks can be added to a vial including an acid and a solvent. The solvent can be an aprotic solvent of any polarity, such as dimethylformamide, dimethyl sulfoxide, dichloromethane, dimethylacetamide, acetonitrile, etc. Then, the mixture can be heated at an elevated temperature for a sufficiently long period of time to form MOF. Any suitable elevated temperature can be used, provided that it is sufficient to promote product formation. In one or more embodiments, the range of the elevated temperature can be 80°C to 160°C. The time period can be sufficient to provide a MOF product. In the method of the embodiment, the mixture can be heated for 48 to 96 hours.

[0057] In the method of one or more embodiments, after heating for a sufficient period of time, the mixture can be slowly cooled to promote crystallization of the MOF product. The mixture can be cooled to any suitable temperature that promotes crystallization. For example, the mixture can be cooled to a temperature below 40°C, below 35°C, below 30°C, below 25°C, or below 20°C. Cooling can be carried out slowly to promote larger, more defined crystals with fewer impurities. In one or more particular embodiments, the mixture containing the MOF product can be cooled at a rate in the range of 0.01 to 0.25°C / min.

[0058] Then, the fluorescent MOF crystals produced by the method of one or more embodiments can be purified according to methods known to those skilled in the art. Certain purification techniques (such as soaking and washing) can be performed multiple times to obtain pure fluorescent MOF crystals.

[0059] In one or more embodiments, a method for preparing a fluorescent MOF comprises reacting a non-fluorescent MOF with a fluorescent compound in the presence of a catalyst to provide a MOF with a covalently attached fluorophore. Non-fluorescent MOFs and fluorescent moieties as previously described may be used. Suitable catalysts include those used for cross-coupling reactions, such as Pd, Cu, Ag, and Fe, among others.

[0060] In one or more embodiments, the method may include dispersing carbon quantum dots (CQDs) into a solution containing a non-fluorescent MOF. Carbon quantum dots are fluorescent, and therefore, when adsorbed to a non-fluorescent MOF, a MOF with a physically adsorbed fluorophore may be formed.

[0061] Compositions of drilling fluids including fluorescent MOFs

[0062] The fluorescent MOF according to the present disclosure can be added to a drilling fluid to provide a drilling fluid composition.The disclosed MOF can be suitable for use in any drilling fluid.

[0063] One or more embodiments of the drilling fluid include water-based fluids. The water-based fluid includes water. The water can be distilled water, deionized water, tap water, fresh water from surface or underground sources, produced water, formation water, natural and synthetic brine, brackish water, natural and synthetic seawater, black water, brown water, grey water, blue water, potable water, non-potable water, other water, and combinations thereof, suitable for the wellbore environment. In one or more embodiments, the water used may naturally contain contaminants, such as salts, ions, minerals, organic matter, and combinations thereof, as long as these contaminants do not interfere with the operation of the drilling fluid.

[0064] One or more embodiments of drilling fluids include oil-based fluids. Oil-based drilling fluids may also be referred to as invert emulsions. Oil-based fluids include oil. Oil may be crude oil, refined oil (such as diesel and mineral oil), non-petroleum organic matter, and combinations thereof that are suitable for use in a wellbore environment. In one or more embodiments, the oil used may naturally contain contaminants, such as salts, minerals, and combinations thereof, as long as these contaminants do not interfere with the operation of the drilling fluid.

[0065] In one or more embodiments, the drilling fluid may contain water in the range of about 50 wt % to 97 wt % based on the total weight of the drilling fluid. In one or more embodiments, the drilling fluid of the embodiments may contain greater than 70 wt % water based on the total weight of the drilling fluid.

[0066] In one or more embodiments, the water used for the drilling fluid can have salts or ions with elevated levels compared to fresh water, such as salts or ions naturally present in formation water, produced water, seawater, and brine. In one or more embodiments, salts or ions are added to the water used to increase the salt or ion level in the water, thereby affecting certain properties (such as the density of the drilling fluid) or mitigating the swelling of clay in contact with the drilling fluid. Without being bound by any theory, increasing the saturation of water by increasing the salt concentration or other organic compound concentration in the water can increase the density of the water, and thus increase the density of the drilling fluid. Suitable salts can include, but are not limited to, alkali metal halides (such as chlorides), hydroxides, or carboxylates. In one or more embodiments, the salts included as part of the water-based fluid can include salts of ions dissociated into sodium, calcium, cesium, zinc, aluminum, magnesium, potassium, strontium, silicon, lithium, chlorides, bromides, carbonates, iodides, chlorates, bromates, formates, nitrates, sulfates, phosphates, oxides, and fluorides, and combinations thereof. Without being bound by any theory, the brine may be used to establish an osmotic equilibrium between the drilling fluid and portions of the subterranean formation, such as swellable clays.

[0067] In one or more embodiments, the drilling fluid may contain one or more salts in an amount ranging from about 1 to about 300 ppb (lbs / barrel). For example, the drilling fluid may contain one or more salts in an amount ranging from a lower limit of any one of 1, 10, 50, 80, 100, 120, 150, 180, 200, 250, and 280 ppb to an upper limit of any one of 20, 30, 40, 50, 70, 100, 120, 150, 180, 200, 220, 240, 260, 280, and 300 ppb, wherein any lower limit may be used in combination with any mathematically compatible upper limit.

[0068] In one or more embodiments, the drilling fluid may include at least one pH adjusting agent. The pH adjusting agent may be at least one alkaline compound. Examples of alkaline compounds may include, but are not limited to, lime (calcium hydroxide, calcium oxide, or mixtures thereof), soda ash (sodium carbonate), sodium hydroxide, potassium hydroxide, and combinations thereof. The alkaline compound may react with gases (such as CO2 or H2S (also referred to as acid gases)) encountered by the drilling fluid composition during drilling operations and prevent the gas from hydrolyzing the components of the drilling fluid composition. The drilling fluid composition of some embodiments may include a pH adjuster in the range of about 0.01 wt % to about 0.7 wt %, such as 0.01 wt % to 0.5 wt %, 0.01 wt % to 0.3 wt %, 0.01 wt % to 0.1 wt %, 0.01 wt % to 0.05 wt %, 0.05 wt % to 0.7 wt %, 0.05 wt % to 0.5 wt %, 0.05 wt % to 0.3 wt %, 0.05 wt % to 0.1 wt %, 0.1 wt % to 0.7 wt %, 0.1 wt % to 0.5 wt %, 0.1 wt % to 0.3 wt %, 0.3 wt % to 0.7 wt %, 0.3 wt % to 0.5 wt %, and 0.5 wt % to 0.7 wt % of the pH adjuster, based on the total weight of the drilling fluid composition. In one or more embodiments, the drilling fluid composition may optionally include 0.01 ppb to 10 ppb of at least one pH adjuster based on the total volume of the drilling fluid composition.

[0069] The drilling fluid of the embodiment can have a neutral or alkaline pH. In one or more embodiments, the drilling fluid can have a pH in the range of about 7, 7.5, 8, 8.5, 9, 9.5, and 10 to about 7.5, 8, 8.5, 9, 9.5, 10, 10.5, and 11, wherein any lower limit can be combined with any mathematically feasible upper limit.

[0070] In one or more embodiments, the drilling fluid may include a weighting agent, which may be dispersed in the drilling fluid. The solid may be finely divided and have a specific gravity (SG) that increases the density of the drilling fluid when added to a water-based fluid. Examples of suitable weighting materials include, but are not limited to, barite (minimum SG 4.20), hematite (minimum SG 5.05), calcium carbonate (minimum SG 2.7-2.8), siderite (minimum SG 3.8), ilmenite (minimum SG 4.6), magnesium tetroxide (minimum SG 4.8), and combinations thereof.

[0071] The drilling fluid of the embodiment can include a weighting material in an amount sufficient to increase the density of the drilling fluid composition to support the wellbore and prevent fluid intrusion. In one or more embodiments, the drilling fluid composition can include a weighting material in a range of about 1 wt % to about 30 wt % based on the total weight of the drilling fluid composition. For example, the drilling fluid can contain a weighting agent in an amount ranging from about 1 ppb to about 700 ppb (such as about 10 ppb to about 650 ppb, about 50 ppb to about 700 ppb, or about 100 ppb to about 600 ppb or about 200 ppb to about 500 ppb).

[0072] In one or more embodiments, the drilling fluid can have a density in the range of about 62 pounds cubic feet (pcf) to about 170 pcf as measured using a Fann Model 140 Mud Balance according to ASTM Standard D4380. For example, the drilling fluid can have a density in the range of about 63 pcf to about 150 pcf, 65 pcf to 140 pcf, 70 pcf to 160 pcf, 80 pcf to 150 pcf, 90 pcf to 140 pcf, 100 pcf to 160 pcf, 70 pcf to 150 pcf, 70 pcf to 100 pcf, and 120 pcf to 160 pcf. The drilling fluid can have a density greater than or equal to 62 pcf, such as greater than or equal to 70 pcf, and such as greater than or equal to 100 pcf.

[0073] In one or more embodiments, the drilling fluid may include an appropriate amount of fluorescent MOF for delivering the tag to the formation downhole. The amount of fluorescent MOF can be adjusted according to the type of fluorescent MOF used. In one or more embodiments, the drilling fluid may include 0.1 to 30 wt % (weight percent) of fluorescent MOF relative to the total weight of the drilling cuttings. For example, the drilling fluid may include the following amount of fluorescent MOF, the lower limit of the amount being 0.1, 0.2, 0.5, 1.0, 2.0, 2.5, 5.0 and 10 wt %, and the upper limit being 5.0, 10, 12, 15, 18, 20, 25 and 30 wt %, wherein any lower limit can be paired with any mathematically compatible upper limit.

[0074] Method of correlating recovered drill cuttings to drilling depth

[0075] One or more embodiments of the present disclosure are directed to methods of determining the drilling depth of drill cuttings using the disclosed fluorescent MOFs. Figure 2 An exemplary method 200 is shown in FIG. Figure 2The method 200 shown in FIG. 2 includes introducing a fluorescent MOF (tag) into a drilling fluid 202. The fluorescent MOF tag can be introduced into the drilling fluid by mixing the tag with the drilling fluid before pumping the drilling fluid downhole (e.g., via reference Figure 1 Labeling system 140 described herein). A label having a specific fluorescence emission wavelength can be introduced at a known drilling depth.

[0076] After the tag is introduced into the drilling fluid, the drilling fluid is circulated through the well 204 during the drilling operation carrying formation cuttings. During the process of circulating the drilling fluid, as formation cuttings are produced, the fluorescent MOF interacts with the formation cuttings, thereby producing tagged cuttings 206.

[0077] As drilling fluid circulates in the well, cuttings (including tagged cuttings) are returned to the surface of the well in the circulating fluid. The method 200 includes collecting these returned cuttings 208 from the circulating drilling fluid at the surface of the well. In some embodiments, the returned cuttings may be collected via a reference Figure 1 The cuttings return and detection system 120 is described for collection.

[0078] Once the returned drilling cuttings are collected, the presence of the fluorescent MOF tag can be detected on the returned cuttings to identify the labeled cuttings 210. The presence of the fluorescent MOF tag can be detected by irradiating the returned cuttings with UV light and obtaining an image of the cuttings with a camera. Other methods for detecting fluorescent MOFs on drilling cuttings can be used. For example, fluorometry, ultraviolet spectroscopy, spectrophotometry, gel permeation chromatography with a light scattering detector, and X-ray fluorescence analysis (XRF) can all be suitable detection methods. In addition, detection methods that are not based on the luminescent properties of MOFs (such as powder x-ray diffraction, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, nuclear magnetic resonance, and gel permeation chromatography) can be used to detect and quantify the returned tags.

[0079] The method 200 then includes associating 212 the tagged cuttings identified from the returned cuttings with a drilling depth in the well at a time during the drilling operation. The association can be performed by identifying the fluorescence of the tagged cuttings and associating the fluorescent MOF with the tag introduced at a given time. The time when a particular tag is introduced can be associated with a given drilling depth (e.g., based on drill pipe length, pumping rate, and calculated return time).

[0080] In one or more embodiments, multiple tags can be used to determine the depth of the cuttings at different times during the drilling operation. In such an embodiment, after the steps previously described, a second fluorescent MOF tag can be pumped down the well along with the drilling fluid. As the well is drilled, the second fluorescent MOF tag can be attached to the formation cuttings and mark them. During the drilling operation, as the drilling fluid circulates, the drilled cuttings return to the surface of the well, and the presence of the second fluorescent MOF can be detected on the marked cuttings in the same or similar manner as the detection of the previous fluorescent MOF tag.

[0081] In one or more embodiments, the first fluorescent MOF tag can have a first emission wavelength and the second fluorescent MOF tag can have a second emission wavelength. The first emission wavelength is different from the second emission wavelength, so that the first fluorescent MOF can be distinguished from the second fluorescent MOF by irradiating the fluorescent MOFs with UV light and obtaining an image of the cuttings with a camera. As will be appreciated by those skilled in the art, any number of different fluorescent MOFs can be used at different depths during the drilling process. Fluorescent MOFs can be selected based on their emission wavelengths so that they can be distinguished from each other using any of the above-mentioned detection methods.

[0082] In further embodiments, the fluorescent MOF can have a first emission wavelength, a first powder x-ray diffraction (PXRD) pattern, and a first set of molecular weights, and the second fluorescent MOF comprises a second emission wavelength, a second powder x-ray diffraction (PXRD) pattern, and a second set of molecular weights. The first emission wavelength is different from the second emission wavelength, the first PXRD pattern is different from the second PXRD pattern, and the first set of molecular weights is different from the second set of molecular weights, such that the first fluorescent MOF can be distinguished from the second fluorescent MOF using a three-dimensional detection matrix consisting of illuminating the fluorescent MOF with UV light and obtaining an image of the cuttings with a camera, obtaining a PXRD pattern of the fluorescent MOF, and obtaining the molecular weights of the fluorescent MOF building blocks using gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS).

[0083] As previously described, in one or more embodiments, the fluorescent MOF may include magnetic particles. In such embodiments, the disclosed method may also include using a magnetic field to separate the fluorescent MOF from the formation cuttings. The magnetically collected fluorescent MOF can be collected and recycled for reuse. In addition, non-magnetic samples can also be recycled and reused. In such cases, it is usually sufficient to rinse the cuttings with a small amount of organic solvent (which will remove the tags from the cuttings). The removed tags can then be collected and recycled for reuse.

[0084] A method for waterfront mapping using fluorescent MOFs

[0085] One or more embodiments relate to the use of fluorescent MOFs to map waterfront areas in highly permeable zones of reservoirs. The MOFs used in such applications may have the same structure and composition as previously described. In such embodiments, the MOFs may be used as tracers to provide information about well connectivity. For example, an injection fluid including a fluorescent MOF tracer may be injected into a well. The fluorescent MOF travels through the formation with the injection fluid. After a predetermined period of time, the fluorescent MOF may be produced with the produced fluid at a production site. At the production site, the MOF fluorescence in the produced fluid may be detected as described above and used to determine the water breakthrough time. The breakthrough times at different production sites may be used to provide fluid flow information for the reservoir.

[0086] If no MOF is detected at the surface via fluorescence, this indicates that the fractures and wells are interconnected. The absence of MOF indicates that the injected fluid is likely lost to the fractures in the reservoir. This method can provide the necessary information to manage production and avoid loss of displaced oil from the mapped area.

[0087] Example

[0088] The following examples are provided to illustrate embodiments of the present disclosure.The examples are not intended to limit the scope of the invention, and they should not be so interpreted.

[0089] Example 1: MOF 1

[0090] MOF 1 includes physically adsorbed carbon quantum dots as fluorophores. The carbon quantum dots were synthesized as follows: 5 g of sodium hydroxide, 100 mL of acetone and 3 ml of divinylbenzene were blended to undergo an aldol condensation reaction under vigorous stirring for 2 hours, and the product was then placed in ambient air, at room temperature and under standard atmospheric pressure for 72 hours. Then, 1 M dilute HCl was used to adjust the pH to neutral. The product was centrifuged and purified with deionized water several times, and the final product was frozen at -70 ° C for 24 hours to obtain CQD powder. The synthesis of MOF 1 was achieved via a one-step method as follows: 2-aminoterephthalic acid (1.44 g, 8.0 mmol), Cr(NO3)3·9H2O (3.20 g, 8.0 mmol) and NaOH (0.80 g, 20 mmol) were dissolved in 60 mL of deionized water by vigorous stirring at room temperature for 30 minutes. Then, different contents of CQD were slowly dispersed, and the color of the mixture solution became light yellow. Subsequently, the resulting suspension was vigorously stirred for 30 minutes, and then the solution was transferred to a Teflon-lined autoclave and heated at 150°C for 12 hours under autogenous pressure, followed by cooling to room temperature. The obtained solid product (MOF 1) was separated via centrifugation and washed three times with DMF, methanol, and deionized water, respectively.

[0091] Drilling fluid 1

[0092] Aqueous drilling fluid samples were prepared in a Hamilton Beach multimixer. Unless otherwise stated, a mixing speed of 12,000 rpm (revolutions per minute) was used. Each sample was prepared by starting with water and then adding each of the listed components to provide a drilling fluid having the following composition. The prepared drilling fluid contained 35 wt % water, about 5 wt % bentonite / clay, 0.3 wt % starch / cellulose, 0.1 wt % xanthan gum / guar gum, about 30 wt % sodium chloride, 0.15 wt % caustic soda, 1.5 wt % marble medium, 26 wt % barite, and 1.95 wt % of the fluorescent MOF from Example 1.

[0093] Drilling fluid 2

[0094] Oil-based drilling fluid samples were prepared in a Hamilton Beach multimixer. Unless otherwise stated, a mixing speed of 12,000 rpm (revolutions per minute) was used. Each sample was prepared by starting with mineral oil and then adding each of the listed components to provide a drilling fluid having the following composition. The prepared drilling fluid contained 68.6 wt % mineral oil, 17 wt % water, 5.7 wt % calcium chloride, 1.7 wt % lime, 1.7 wt % surfactant, 0.8 wt % clay, 2.55 wt % calcium carbonate, and 1.95 wt % of the fluorescent MOF from Example 1.

[0095] Embodiments of the present disclosure may provide at least one of the following advantages. The disclosed compositions and methods may allow for more accurate depth determination of drilling cuttings in real time during drilling operations compared to conventional methods of analyzing drilling cuttings. Analysis may be performed quickly on site, rather than shipping samples to a laboratory for analysis. Additionally, complex identification matrices may be used for advanced systems. Furthermore, in some embodiments, tags may be recycled using magnetic recovery of MOFs comprising magnetic particles.

[0096] Although only several exemplary embodiments are described in detail above, it will be readily appreciated by those skilled in the art that many changes may be made in these exemplary embodiments without substantially departing from the present invention. Therefore, all such changes are intended to be included within the scope of the present disclosure as defined in the appended claims.

Claims

1. A composition of matter comprising: Fluorescent metal-organic frameworks (MOFs); and Drilling fluid.

2. The composition of claim 1, wherein the fluorescent MOF comprises a fluorescent building block.

3. The composition of claim 2, wherein the fluorescent building block is a fluorescent organic linker selected from the group consisting of: 1,4-benzenedicarboxylic acid and its derivatives; 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid and its derivatives; biphenyl-4,4'-dicarboxylic acid and its derivatives; 2,7-pyrenedicarboxylic acid and its derivatives; 1,6-pyrenedicarboxylic acid and its derivatives; 1,3,6,8-pyrenetetracarboxylic acid and its derivatives; pyrene-1-carboxylic acid and its derivatives; pyrene-2-carboxylic acid and its derivatives; 8-anilino-1-naphthalenesulfonic acid and its derivatives; 1,6-anthracenedicarboxylic acid and its derivatives; 1,1',4',1"-terphenyl-2',4,4",5'-tetracarboxylic acid (TPTC), 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethane (TPPE), trans-4,4'-stilbene dicarboxylic acid, other organic linkers, and combinations thereof.

4. The composition of claim 2, wherein the fluorescent building block is a fluorescent metal cluster selected from the group consisting of: Eu 3+ Sc 3+ , Y 3+ 、Sm 3+ 、Pm 3+ 、Nd 3+ , Pr 3+ 、Tm 3+ , Er 3+ 、Dy 3+ , Tb 3+ 、Zn 2+ 、Zr 4+ 、Co 3+ 、Ni 2 + Cr 3+ , Nb 5+ , Cu 2+ , Cu 1+ , Fe 2+ , Fe 3+ 、Ti 4+ 、Al 3+ 、Am 4+ , U 4+ 、Am 3+ 、Np 4+ 、Np 3+ and their combinations.

5. The composition of claim 1, wherein the fluorescent MOF comprises a non-fluorescent building block and a fluorescent moiety bound to the MOF. The composition of claim 5 , wherein the fluorescent moiety is covalently bound to the MOF.

7. The composition of claim 5, wherein the fluorescent moiety is selected from the group consisting of rhodamine dyes and their derivatives, fluorescein and its derivatives, fluorescein isothiocyanate, sodium fluorescein and its derivatives, eosin and its derivatives, BODIPY dyes and their derivatives, porphyrins and their derivatives, phthalocyanines and their derivatives, and combinations thereof.

8. The composition of claim 1, wherein the MOF comprises a fluorophore inserted into the pores of the MOF.

9. The composition of claim 8, wherein the fluorophore is selected from the group consisting of metal ions, metal complexes, rhodamine B, fluorescein, quantum dots, emitting beads, and combinations thereof.

10. The composition of claim 1, wherein the MOF further comprises magnetic particles selected from the group consisting of iron oxide nanoparticles, superparamagnetic iron oxide nanoparticles, and combinations thereof.

11. The composition of claim 1, wherein the MOF is incorporated into a composite material of a porous silica, glass, ceramic or polymer matrix.

12. The composition of claim 1, further comprising formation cuttings, wherein the MOF is attached to the formation cuttings.

13. A method comprising: Introducing fluorescent metal-organic frameworks (MOFs) into drilling fluids; During a drilling operation that produces formation cuttings, circulating the drilling fluid through the well so that the fluorescent MOF interacts with the formation cuttings to produce labeled cuttings; collecting returned cuttings from the circulating drilling fluid at the surface of the well; detecting the presence of the fluorescent MOF on the returned cuttings to identify the labeled cuttings; as well as The marked cuttings are associated with a drilling depth in the well at a time during the drilling operation.

14. The method of claim 13, wherein detecting the fluorescent MOF comprises illuminating the labeled rock cuttings with UV light and obtaining an image of the rock cuttings with a camera.

15. The method of claim 13, wherein detecting the fluorescent MOF comprises irradiating the labeled rock chips with UV light and obtaining an image of the labeled rock chips with a camera, analyzing the labeled rock chips by powder x-ray diffraction (PXRD) and obtaining a PXRD spectrum of the labeled rock chips, and analyzing the labeled rock chips by GC-MS or LC-MS and obtaining a molecular weight fragmentation spectrum of the labeled rock chips.

16. The method of claim 13, wherein the returned cuttings are collected in a shaker.

17. The method according to claim 13, further comprising: After circulating the fluorescent MOF, pumping a second fluorescent MOF down the well along with the drilling fluid, wherein the second fluorescent MOF is configured to adhere to and mark formation cuttings as the well is drilled; returning the drilling fluid and marked formation cuttings from the well; as well as The presence of the second fluorescent MOF is detected on the labeled cuttings.

18. The method of claim 17, wherein the fluorescent MOF comprises a first emission wavelength, wherein the second fluorescent MOF comprises a second emission wavelength, and wherein the first emission wavelength is different from the second emission wavelength, such that the fluorescent MOF can be distinguished from the second fluorescent MOF by illuminating the fluorescent MOF with UV light and obtaining an image of the marked rock cuttings with a camera.

19. The method of claim 13, further comprising, after detecting the presence of the fluorescent MOF on the returned rock cuttings, using a magnetic field to separate the fluorescent MOF from the formation rock cuttings.

Images