Tracer composition

Abstract

The present disclosure relates to tracing gas flow in a hydrocarbon reservoir with a composition comprising a degradable polymer and a detectable component. An exemplary method includes introducing a tracer composition at a first location in the reservoir, contacting the tracer composition with the reservoir to hydrolyze the degradable polymer, and detecting a degraded tracer composition comprising the hydrolyzed polymer and the detectable component in a gas sample collected at a second location in the reservoir.

Description

Priority requirements

[0001] This application claims priority to U.S. Patent Application No. 18 / 416,359, filed January 18, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the use of compositions comprising a biodegradable polymer and a detectable component to trace gas flow in a hydrocarbon reservoir. Background Technology

[0003] Tracer techniques can be used in hydrocarbon reservoirs to map, monitor, and confirm in-situ hydrocarbons, as well as to monitor hydrocarbon production in areas of interest. For example, tracer techniques can be used to generate one or more parameters that can be used for reservoir characterization, including, for example, inter-well connectivity, fluid distribution, fracture location, swept volume, and residual oil saturation.

[0004] However, simultaneously monitoring gas production from hydrocarbon reservoirs can be challenging, especially after acidizing or fracturing. Traditional tools for monitoring such production can be expensive and, in some cases, indistinguishable due to overlap with signals from other chemicals present in the reservoir. Similarly, the use of production logging tools (PLTs) can be costly and involve disruption to routine operations.

[0005] Therefore, there is a need to improve the tracing of gas flow in hydrocarbon reservoirs. Summary of the Invention

[0006] This disclosure provides a method for tracing gas flow in a hydrocarbon reservoir. The method includes: introducing a tracer composition comprising a degradable polymer and a detectable component at a first location in the reservoir; and contacting the tracer composition with the reservoir to hydrolyze the degradable polymer. The method further includes detecting the degraded tracer composition, comprising the hydrolyzed polymer and the detectable component, in a gas sample collected at a second location in the reservoir. The detectable component includes particulate metal oxide and a fluorescent dye disposed on the surface of the particulate metal oxide.

[0007] This disclosure also provides a yield-enhancing treatment solution comprising an aqueous medium and a tracer composition suspended in the aqueous medium. The tracer composition comprises a degradable polymer and a detectable component, wherein the detectable component includes particulate metal oxide and a fluorescent dye disposed on the surface of the particulate metal oxide. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of an underground stratum that includes a hydrocarbon reservoir.

[0009] Figure 2 This is a flowchart of a method for tracing gas flow in a hydrocarbon reservoir.

[0010] Figure 3 The images show a comparative composition (leftmost vial) aged under elevated temperature and humidity before pressure was applied, and a tracer composition (the remaining vials) according to certain embodiments of this disclosure.

[0011] Figure 4 The images show comparative compositions (leftmost tray) aged under elevated temperature and humidity and subjected to pressure, and tracer compositions (other trays) according to certain embodiments of this disclosure.

[0012] Figure 5 These are photographs showing tracer compositions according to certain embodiments of the present disclosure after aging at elevated temperature and humidity before pressure is applied.

[0013] Figure 6 These are photographs showing tracer compositions according to certain embodiments of the present disclosure after aging under elevated temperature and humidity and applied pressure.

[0014] Figure 7 The photograph shows a comparative composition after aging under elevated temperature and humidity before pressure was applied.

[0015] Figure 8 These are photographs showing tracer compositions according to certain embodiments of the present disclosure after aging at elevated temperature and humidity before pressure is applied.

[0016] Figure 9 These are photographs showing tracer compositions according to certain embodiments of the present disclosure after aging under elevated temperature and humidity and applied pressure.

[0017] Figure 10 These are fluorescence images of tracer compositions according to certain embodiments of the present disclosure prior to aging under elevated temperature and humidity.

[0018] Figure 11 These are fluorescence images of tracer compositions according to certain embodiments of the present disclosure after aging under elevated temperature and humidity and applying pressure.

[0019] Figure 12 These are fluorescence images of tracer compositions according to certain embodiments of the present disclosure prior to aging under elevated temperature and humidity.

[0020] Figure 13 These are fluorescence images of tracer compositions according to certain embodiments of the present disclosure after aging under elevated temperature and humidity and applying pressure. Detailed Implementation

[0021] This disclosure relates to a method for tracing gas flow in a hydrocarbon reservoir using a tracer composition comprising a degradable polymer and a detectable component. Upon introduction at a first site in the reservoir (e.g., at a production enhancement treatment site), the hydrolysis of the degradable polymer can produce a degraded tracer composition that can be carried through the reservoir by the gas flow. This degraded tracer composition can be detected at a second site in the reservoir (e.g., at a production site). The gas flow pattern in the reservoir can be determined by comparing the detectable component of the degraded tracer composition collected at the second site with the detectable component of the tracer composition introduced at the first site. The tracer compositions of this disclosure can be cost-effective and can have unique, customizable detection properties, for example, suitable for introduction into multiple production enhancement treatment stages of a hydrocarbon reservoir for gas flow analysis across the entire reservoir.

[0022] tracer composition

[0023] This disclosure relates to a method for tracing gas flow in a hydrocarbon reservoir by introducing a tracer composition into the reservoir. The tracer composition comprises a degradable polymer and a detectable component.

[0024] In some embodiments, the biodegradable polymer can be hydrolyzed under the conditions of the hydrocarbon reservoir. For example, the biodegradable polymer of this disclosure can become brittle and decompose upon exposure to elevated humidity, temperature, and pressure in the reservoir.

[0025] In some embodiments, the biodegradable polymer includes thermoplastics. In some embodiments, the thermoplastic includes thermoplastic polyesters. For example, in some such embodiments, the thermoplastic includes poly(lactic acid) (PLA), polyethylene terephthalate (PET), polypropylene terephthalate (PBT), and polybutylene terephthalate (PBT).

[0026] In some embodiments, the degradable polymer comprises a thermoplastic polyester elastomer. In some embodiments, the thermoplastic polyester elastomer comprises a block copolymer containing hard and soft segments. In some such embodiments, hydrolysis of the thermoplastic polyester elastomer causes the soft segments to break down, thereby reducing the viscoelasticity of the tracer composition. Such a brittle composition can degrade into smaller particles under applied pressure (such as pressure applied in a hydrocarbon reservoir), which can then be carried through the reservoir by gas flow.

[0027] In some embodiments, the hard segment comprises a polyester comprising alkylene glycol monomer units and aromatic dicarboxylic acid monomer units. In some embodiments, the alkylene glycol monomer units comprise ethylene glycol, propylene glycol, butanediol, or any combination thereof. In some embodiments, the aromatic dicarboxylic acid monomer units comprise terephthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyl dicarboxylic acid, or any combination thereof. For example, in some such embodiments, the hard segment comprises ethylene glycol terephthalate, propylene glycol terephthalate, butylene glycol terephthalate, or any combination thereof. In some embodiments, the soft segment comprises a polyether, polyester, polycarbonate, or any combination thereof. In some embodiments, the soft segment comprises a polyether, such as a polyoxyalkylene glycol. For example, in some such embodiments, the polyoxyalkylene glycol comprises polytetramethylene glycol. In some embodiments, the soft segment comprises a polyester, such as polycaprolactone or polybutylene adipate.

[0028] In some embodiments, the thermoplastic polyester elastomer comprises poly(butylene terephthalate)-co-(tetramethylene ether)diol terephthalate (PBT-PTMG). In some embodiments, the thermoplastic polyester elastomer comprises poly(ethylene terephthalate)-co-(tetramethylene ether)diol terephthalate (PET-PTMG). Exemplary thermoplastic polyester elastomers include HYTREL. ® Thermoplastic polyester elastomers, such as HYTREL ® 7246.

[0029] In some embodiments, the weight-average molecular weight of the biodegradable polymer is from about 20,000 g / mol to about 500,000 g / mol, for example, from about 20,000 g / mol to about 300,000 g / mol, from about 20,000 g / mol to about 250,000 g / mol, from about 20,000 g / mol to about 150,000 g / mol, from about 50,000 g / mol to about 500,000 g / mol, from about 50,000 g / mol to about 300,000 g / mol, from about 50,000 g / mol to about 250,000 g / mol, from about 50,000 g / mol to about 150,000 g / mol, from about 100,000 g / mol to about 500,000 g / mol, from about 100,000 g / mol to about 30 ... g / mol to about 250,000 g / mol or about 100,000 g / mol to about 150,000 g / mol.

[0030] In some embodiments, the detectable component includes a colorant. In some such embodiments, the colorant is detectable in the visible spectrum. In some embodiments, the colorant includes pigments, such as green, red, or yellow pigments. Exemplary colorants include OMNICOLOR™ multipurpose color concentrates, such as OMNICOLOR™ Fluorescent Green, OMNICOLOR™ Flame Red, and OMNICOLOR™ Fluorescent Yellow. In some embodiments, the tracer composition comprises about 0.01 wt% to about 20 wt% of a colorant and about 80 wt% to about 99.99 wt% of a biodegradable polymer, or about 0.01 wt% to about 10 wt% of a colorant and about 90 wt% to about 99.99 wt% of a biodegradable polymer. In some embodiments, the tracer composition comprises about 0.01 wt% to about 0.5 wt%, about 0.01 wt% to about 0.3 wt%, about 0.025 wt% to about 1 wt%, about 0.025 wt% to about 0.5 wt%, about 0.025 wt% to about 0.3 wt%, about 0.05 wt% to about 1 wt%, about 0.05 wt% to about 0.5 wt%, or about 0.05 wt% to about 0.3 wt% of a colorant. In some embodiments, the tracer composition comprises about 95 wt% to about 99.5 wt%, about 95 wt% to about 99 wt%, about 98 wt% to about 99.99 wt%, about 98 wt% to about 99.5 wt%, about 98 wt% to about 99 wt%, about 99 wt% to about 99.99 wt%, about 99 wt% to about 99.5 wt%, or about 99 wt% to about 99 wt% of a biodegradable polymer.

[0031] In some embodiments, the detectable components include fluorescent dyes and metal oxides. In some such embodiments, the fluorescent dye is detectable in the visible spectrum. Exemplary fluorescent dyes include xanthan dyes, cyanine dyes, and coumarin dyes. In some embodiments, the fluorescent dye includes xanthan dyes such as fluorescein, rhodamine, eosin, or Texas red. In some such embodiments, the fluorescent dye includes rhodamine dyes, such as rhodamine B.

[0032] In some embodiments, the metal oxide includes metal oxide hydroxides or metal hydroxides. In some embodiments, the metal oxide includes aluminum oxide. In some embodiments, the aluminum oxide includes aluminum oxide hydroxide (aluminum oxide hydroxide or aluminum hydroxide), aluminum hydroxide, or both. In some embodiments, the aluminum oxide includes AlO.x (OH) 2y The sum of x and y is at most about 2, for example, about 1 to about 2, or about 1.5. In some embodiments, the aluminum oxide includes Al2O3, AlO(OH), Al(OH)3, or any combination thereof. For example, in some embodiments, the aluminum oxide includes Al(OH)3.

[0033] In some embodiments, the metal oxide is in particulate form. For example, in some embodiments, the detectable component includes particulate aluminum oxide, such as particulate aluminum hydroxide. In some embodiments, the average particle size of the particulate metal oxide is about 10 nm to about 10 µm, for example, about 10 nm to about 5 µm, about 10 nm to about 1 µm, about 100 nm to about 10 µm, about 100 nm to about 5 µm, about 100 nm to about 1 µm, about 500 nm to about 10 µm, about 500 nm to about 5 µm, or about 500 nm to about 1 µm.

[0034] In some embodiments, a fluorescent dye is disposed on the surface of a particulate metal oxide. For example, in some embodiments, the detectable component includes a fluorescent dye disposed on the surface of a particulate aluminum oxide (such as particulate aluminum hydroxide). In some such embodiments, the fluorescent dye and the particulate metal oxide are covalently bonded. For example, in some embodiments, the detectable component includes a fluorescent dye covalently bonded to the surface of particulate aluminum hydroxide. In some embodiments, the detectable component includes Rhodamine B covalently bonded to particulate aluminum hydroxide, which is formed, for example, by a dehydration reaction of Rhodamine B with -OH groups present on the surface of particulate aluminum hydroxide.

[0035] In some embodiments, the tracer composition comprises about 0.001 wt% to about 0.1 wt% of a fluorescent dye, about 1 wt% to about 80 wt% of a metal oxide, and about 10 wt% to about 99 wt% of a biodegradable polymer. In some embodiments, the tracer composition comprises about 0.001 wt% to about 0.05 wt%, about 0.001 wt% to about 0.03 wt%, about 0.0025 wt% to about 0.1 wt%, about 0.0025 wt% to about 0.05 wt%, about 0.0025 wt% to about 0.03 wt%, about 0.005 wt% to about 0.1 wt%, about 0.005 wt% to about 0.05 wt%, or about 0.005 wt% to about 0.03 wt% of a fluorescent dye. In some embodiments, the tracer composition comprises about 1% to about 60% by weight, about 1% to about 40% by weight, about 10% to about 80% by weight, about 10% to about 60% by weight, about 10% to about 40% by weight, about 20% to about 80% by weight, about 20% to about 60% by weight, or about 20% to about 40% by weight of a metal oxide. In some embodiments, the tracer composition comprises about 10% to about 99% by weight, about 10% to about 90% by weight, about 10% to about 80% by weight, about 40% to about 99% by weight, about 40% to about 90% by weight, about 40% to about 80% by weight, about 60% to about 99% by weight, about 60% to about 90% by weight, or about 60% to about 80% by weight of a biodegradable polymer.

[0036] In some embodiments, the tracer composition comprises an extrudate of a degradable polymer and a detectable component. In some embodiments, the tracer composition is in particulate form, such as pellets or fibers. In some embodiments, the tracer composition comprises particles with an average size of at least about 5 mm, said average size being, for example, at least about 7.5 mm, at least about 10 mm, at least about 15 mm, at least about 20 mm, at least about 30 mm, at least about 40 mm, or at least about 50 mm. In some embodiments, the tracer composition is in the form of fibers with an average length of at least about 4 mm (e.g., at least about 6 mm or at least about 10 mm). In some such embodiments, the average diameter of the fibers is from about 0.01 mm to about 1 mm, for example, from about 0.01 mm to about 0.3 mm, from about 0.05 mm to about 0.5 mm, or from about 0.1 mm to about 1 mm.

[0037] Production enhancement treatment fluid (stimulation fluid)

[0038] This disclosure also provides a production-enhancing treatment fluid comprising an aqueous medium and a tracer composition suspended in the aqueous medium. In some embodiments, the production-enhancing treatment fluid comprises the tracer composition of this disclosure. The production-enhancing treatment fluid may comprise other components known in the art. For example, in some embodiments, the production-enhancing treatment fluid further comprises a scale inhibitor, an emulsifier, a friction reducer, a weighting agent, or any combination thereof.

[0039] In some embodiments, the aqueous medium includes fresh water, field water, saltwater, brine, seawater, or any combination thereof. In some such embodiments, the aqueous medium includes produced water.

[0040] In some embodiments, the enhancement treatment solution contains an acid. In some embodiments, the acid includes hydrofluoric acid, hydrochloric acid, or both. For example, in some embodiments, the enhancement treatment solution contains hydrochloric acid. In another instance, in some embodiments, the enhancement treatment solution contains both hydrochloric acid and hydrofluoric acid.

[0041] Tracing methods

[0042] This disclosure also provides a method for tracing gas flow in a hydrocarbon reservoir. The method includes introducing a tracer composition at a first location in the reservoir, contacting the tracer composition with the reservoir to hydrolyze a degradable polymer, thereby producing a degraded tracer composition comprising the hydrolyzed polymer and a detectable component. The method further includes detecting the degraded tracer composition in a gas sample collected at a second location in the reservoir.

[0043] Figure 1 This is a schematic diagram of a subsurface formation including a hydrocarbon reservoir 110. In the illustrated embodiment, drilling system 102 is configured to introduce tracer composition 122 at a first location 112 of the hydrocarbon reservoir 110. Hydrolysis of the biodegradable polymer of tracer composition 122 produces a degraded tracer composition 124, which is carried by gas flow 114 to a second location 116 of the hydrocarbon reservoir 110. The degraded tracer composition 124 is captured from a gas sample flowing through conduit 130 at a filter 132.

[0044] In some embodiments, the method includes introducing any tracer composition of this disclosure at a first location in the reservoir. In some embodiments, the method includes introducing a tracer composition into an acidified reservoir. In some embodiments, the method includes introducing a tracer composition into a fracturing reservoir.

[0045] In some embodiments, the method includes pumping a production enhancement fluid comprising a tracer composition into the reservoir at a first location. The production enhancement fluid can be any production enhancement agent described herein, such as a production enhancement fluid suitable for acidizing or fracturing operations.

[0046] The degraded tracer composition may comprise particles with an average size smaller than the average particle size of the tracer composition introduced at the first location. For example, in some embodiments, the degraded tracer composition comprises particles with an average size less than about 2 mm, such as less than about 1.5 mm, less than about 1.0 mm, less than about 0.5 mm, less than about 0.25 mm, less than about 0.1 mm, less than about 75 µm, less than about 50 µm, less than about 25 µm, less than about 10 µm, less than about 5 µm, or less than about 1 µm. In some embodiments, the degraded tracer composition comprises particles with an average size of at least about 500 nm. In some embodiments, the degraded tracer composition comprises a powder.

[0047] In some embodiments, the detectable component includes a colorant, and detecting the degraded tracer composition includes visualizing the colorant. In some embodiments, the detectable component includes a fluorescent dye, and detecting the degraded composition includes detecting the fluorescent dye using a fluorometer. In some embodiments, the detectable component includes a metal oxide, and detecting the degraded composition includes detecting the metal oxide using an X-ray fluorescence spectrometer.

[0048] Figure 2 This is a process flow diagram of a method 200 for tracing gas flow in a hydrocarbon reservoir. The method begins at block 202 with the introduction of a tracer composition comprising a degradable polymer and a detectable component at a first location in the reservoir. At block 204, the tracer composition is contacted with the reservoir to hydrolyze the degradable polymer. At block 206, the degraded tracer composition comprising the hydrolyzed polymer and the detectable component is detected at a second location in the reservoir.

[0049] definition

[0050] Unless the context clearly indicates otherwise, the terms “a,” “an,” and “the” are used in this disclosure to refer to one or more species. Unless otherwise stated, the term “or” is used to mean a non-exclusive “or.” The expression “at least one of A and B” has the same meaning as “A, B, or A and B.” Furthermore, it should be understood that phrases or terms used in this disclosure that are not otherwise defined are for descriptive purposes only and not for limiting purposes. The use of any section headings is intended to aid in reading this document and should not be construed as limiting; information relating to a section heading may appear within or outside that particular section.

[0051] Values ​​expressed as ranges should be interpreted flexibly to include not only the numerical values ​​explicitly stated as limits of the range, but also all individual numerical values ​​or subranges covered within that range, as if each numerical value and subrange were explicitly stated. For example, "about 0.1% to about 5%" or "about 0.1% to 5%" should be understood to include not only about 0.1% to about 5%, but also the individual numerical values ​​(e.g., 1%, 2%, 3%, and 4%) and subranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. Unless otherwise stated, the expression "about X to Y" has the same meaning as "about X to about Y". Similarly, unless otherwise stated, the expression "about X, Y, or about Z" has the same meaning as "about X, about Y, or about Z".

[0052] As used in this disclosure, the term “about” may allow for a degree of variability in the value or range, such as within 10%, 5%, or 1% of the stated value or range limit.

[0053] In the methods disclosed herein, actions can be performed in any order except where the timing or sequence of operations is explicitly stated. Furthermore, specified actions can be performed simultaneously unless the explicit language of the claims specifies that they are performed individually. For example, the claimed action of X and the claimed action of Y can be performed simultaneously in a single operation, and the resulting method will fall within the literal scope of the claimed method.

[0054] As used in this disclosure, the term "size" with respect to particles refers to the primary size of the particle. For example, the size of a cylindrical particle is the larger of its diameter and its height. In another instance, the size of a spherical particle is its diameter.

[0055] As used in this disclosure, the term "metal oxide" refers to stoichiometric and non-stoichiometric metal oxides, metal oxide hydroxides, and metal hydroxides. Exemplary metal oxides include silicon oxides and aluminum oxides.

[0056] As used in this disclosure, the term "subsurface formation" refers to any material located below the Earth's surface (including below the bottom surface of the ocean). For example, a subsurface formation or material can be any portion of a wellbore and any portion of a subsurface oil- or water-producing formation or area in contact with wellbore fluids. Injecting material into a subsurface formation can include contacting that material with any portion of the wellbore or any subsurface area in contact with wellbore fluids. Subsurface material can include any material placed in the wellbore, such as cement, drill shaft, liner, tubing, casing, or screen; injecting material into a subsurface formation can include contact with such subsurface material. In some instances, a subsurface formation or material can be any subsurface area capable of producing liquid or gaseous petroleum materials or water, or any subsurface portion in contact with liquid or gaseous petroleum materials or water fluids.

[0057] As used in this disclosure, the term "hydrocarbon reservoir" refers to an underground oil-producing area within a subsurface formation. Hydrocarbon reservoirs can produce liquid or gaseous petroleum materials.

[0058] As used in this disclosure, the term "downhole" means below the Earth's surface, such as within a wellbore or in fluid connection with the wellbore.

[0059] As used in this disclosure, the term "production enhancement fluid" refers to a fluid or slurry used downhole to enhance hydrocarbon production (e.g., in acidizing or fracturing operations).

[0060] Example

[0061] Example 1. A tracer composition containing a colorant

[0062] The tracer compositions 1-3 were prepared by: extruding 4g of thermoplastic polyester elastomer (HYTREL) containing poly(butylene terephthalate) hard segments and polyether-based soft segments using a HAAKE MiniLab 3 extruder at 240°C. ® 7246 (DuPont™) was compounded with 0.05 g of a colorant containing green pigment (FL Green), a colorant containing red pigment (Flame Red), and a colorant containing yellow pigment (FL Yellow) (OMNICOLOR™ multipurpose colorant, Avient). The tracer composition was extruded through a thin circular die to form fibers. A colorant-free comparative composition C1 was prepared by extruding 4 g of the above thermoplastic polyester elastomer at 240°C.

[0063] Tracer compositions 1-3 and composition C1 were aged under argon atmosphere in an autoclave at 150°C and approximately 100% relative humidity, with degradation monitored daily. All samples began to become brittle after approximately 4 days, but remained non-crushable under compression. After approximately 6 days, the samples degraded into small particles or powder upon application of pressure. Even after degradation, the samples remained distinguishable. Figure 3 and 4 The images show samples stored for 6 days at elevated temperature and humidity before and after the application of pressure.

[0064] Thermal analysis was performed on unextruded thermoplastic polyester elastomer, composition C1, and tracer compositions 1-3 before and after aging using differential scanning calorimetry (DSC). The heat flow as a function of temperature was compared to determine whether extrusion with or without colorant affected the thermal properties of the tracer compositions. All DSC thermograms were obtained during heating and cooling at a rate of 10 °C / min. The results showed consistent melting points of ~219 °C and recrystallization temperatures of ~174 °C for both the unextruded thermoplastic polyester elastomer and composition C1, confirming a certain level of supercooling. Similar results were observed for tracer compositions 1-3 before aging: melting points of ~217 °C and recrystallization temperatures of ~180 °C. The results of DSC analysis indicate that mixing the thermoplastic polyester elastomer with colorant via extrusion had no significant effect on the thermal properties of tracer compositions 1-3 before aging. DSC scans of tracer compositions 1-3 after aging showed similar melting points at ~216°C, but slightly higher recrystallization temperatures at 185°C, indicating that the degraded particles mainly consist of hard segments of thermoplastic polyester elastomer. Glass transition events were observed for tracer compositions 1 and 2, confirming the transition from a rigid to a flexible structure.

[0065] Example 2. Tracer composition containing metal oxide and fluorescent dye

[0066] 1.6 g of Al(OH)3 powder was mixed with 10 mL of 100 ppm Rhodamine(R)B aqueous solution and then dried in an oven at 94 °C for 12 hours to obtain a detectable component containing Rhodamine B covalently bonded to the surface of particulate Al(OH)3.

[0067] Tracer composition 4 was prepared as follows: Using a HAAKE MiniLab 3 extruder at 240°C (20°C higher than the melting point of the thermoplastic polyester elastomer), 1.6 g of the detectable component was mixed with 4 g of a thermoplastic polyester elastomer containing poly(butylene terephthalate) hard segments and polyether-based soft segments. ®7246 (DuPont™) was blended. The tracer composition was extruded through a thin circular die to form fibers. Comparative composition C2, free of detectable components, was prepared by extruding 4 g of the above thermoplastic polyester elastomer at 240°C.

[0068] Tracer composition 5 was prepared as follows: using a HAAKE MiniLab 3 extruder, at 190°C (20°C higher than the melting point of poly(lactic acid), 1.6 g of the detectable component was mixed with 4 g of poly(lactic acid) (Igneo™ Biopolymer 2500HP). The tracer composition was extruded through a thin circular die to form fibers. Comparative composition C3, which did not contain the detectable component, was prepared by extruding 4 g of the above poly(lactic acid) at 190°C. Comparative composition C4, which did not contain Rhodamine B, was prepared by extruding a mixture of 1.6 g of Al(OH)3 powder and 4 g of poly(lactic acid) at 190°C.

[0069] Tracer compositions 4 and 5, as well as compositions C2-C4, were aged in an autoclave under argon at 150°C and approximately 100% relative humidity, with degradation monitored daily. Within approximately one day, tracer composition 5 and composition C3 degraded into small particles or powder upon pressure application. Even after degradation, tracer composition 5 retained its distinguishable color. Figure 5 and 6 The images show samples stored for one day at elevated temperature and humidity, before and after the application of pressure. Figure 7 As shown, composition C4 does not degrade into solid particles after aging, but instead forms sticky, hygroscopic oligomers.

[0070] Tracer compositions 4 and C2 begin to become brittle after approximately 4 days, but the samples remain non-crushable under compression. After approximately 6 days, the tracers degrade into small particles or powder upon application of pressure. Even after degradation, tracer composition 5 retains its distinguishable color. Figure 8 and 9 The images show samples stored for 6 days at elevated temperature and humidity before and after the application of pressure.

[0071] Tracer compositions 4 and 5, before and after aging, and composition C4, before aging, were examined under a fluorescence microscope. Measurements were performed using a Chroma ET-CY3 / Rhodamine filter at a 500-ms exposure and a gain factor of 1. Tracer composition 4 (before aging and 6 days after aging) was examined under a fluorescence microscope. Figure 10 and 11 ), and for tracer compositions 5 before aging and after 1 day of aging (respectively). Figure 12 and 13Fluorescence imaging revealed strong and discernible levels of rhodamine dye. No fluorescence signal was detected for composition C4.

[0072] Implementation Plan

[0073] Some implementations of this disclosure are provided in the following list:

[0074] Implementation Scheme 1. A method for tracing gas flow in a hydrocarbon reservoir, the method comprising: introducing a tracer composition at a first location in the reservoir, wherein the tracer composition comprises a degradable polymer and a detectable component; contacting the tracer composition with the reservoir to hydrolyze the degradable polymer; and detecting the degraded tracer composition in a gas sample collected at a second location in the reservoir, wherein the degraded tracer composition comprises the hydrolyzed polymer and the detectable component; wherein the detectable component comprises particulate metal oxide; and a fluorescent dye disposed on the surface of the particulate metal oxide.

[0075] Implementation Scheme 2. The method according to Implementation Scheme 1, wherein the degradable polymer comprises thermoplastic.

[0076] Implementation Scheme 3. The method according to Implementation Scheme 2, wherein the thermoplastic comprises poly(lactic acid).

[0077] Implementation Scheme 4. The method according to any one of Implementation Schemes 1-3, wherein the degradable polymer comprises a thermoplastic polyester elastomer.

[0078] Implementation Scheme 5. The method according to Implementation Scheme 4, wherein the thermoplastic polyester elastomer comprises a block copolymer, the block copolymer comprising hard segments and soft segments.

[0079] Implementation Scheme 6. The method according to Implementation Scheme 5, wherein the hard segment comprises polyethylene terephthalate, propylene terephthalate, butylene terephthalate, or any combination thereof.

[0080] Implementation Scheme 7. The method according to Implementation Scheme 5 or Implementation Scheme 6, wherein the soft segment comprises polyether, polyester, polycarbonate or any combination thereof.

[0081] Implementation Scheme 8. The method according to Implementation Scheme 7, wherein the soft segment comprises a polyether, and the polyether comprises a polyoxyalkylene glycol.

[0082] Implementation Scheme 9. The method according to any one of Implementation Schemes 1-8, wherein the fluorescent dye is detectable in the visible spectrum.

[0083] Implementation Scheme 10. The method according to Implementation Scheme 9, wherein the fluorescent dye comprises zeatin dye.

[0084] Implementation Scheme 11. The method according to Implementation Scheme 10, wherein the zeatin dye comprises rhodamine dye.

[0085] Implementation Scheme 12. The method according to any one of Implementation Schemes 1-11, wherein the metal oxide comprises aluminum hydroxide.

[0086] Implementation Scheme 13. The method according to any one of Implementation Schemes 1-12, wherein the fluorescent dye is covalently bonded to the surface of the particulate metal oxide.

[0087] Implementation Scheme 14. The method according to any one of Implementation Schemes 1-13, wherein the average size of the particulate metal oxide is about 10 nm to about 10 µm.

[0088] Implementation Scheme 15. The method according to any one of Implementation Schemes 1-14, wherein the tracer composition comprises an extrusion of the degradable polymer and the detectable component.

[0089] Implementation Scheme 16. The method according to any one of Implementation Schemes 1-15, wherein the tracer composition comprises particles with an average size of at least about 5 mm.

[0090] Implementation Scheme 17. The method according to any one of Implementation Scheme 16, wherein the particles of the tracer composition comprise granules or fibers.

[0091] Implementation Scheme 18. The method according to any one of Implementation Scheme 17, wherein the particles comprise fibers with an average length of at least about 4 mm.

[0092] Implementation Scheme 19. The method according to any one of Implementation Schemes 16-18, wherein the degraded tracer composition comprises particles with an average size of less than about 2 mm.

[0093] Implementation Scheme 20. The method according to Implementation Scheme 19, wherein the particles of the degraded tracer composition comprise powder.

[0094] Implementation Scheme 21. The method according to any one of Implementation Schemes 1-20, wherein introducing the tracer composition includes pumping a production enhancement treatment fluid containing the tracer composition into the reservoir at the first location.

[0095] Implementation Scheme 22. The method according to Implementation Scheme 21, wherein the yield-enhancing treatment liquid comprises acid.

[0096] Implementation Scheme 23. The method according to any one of Implementation Schemes 1-22, wherein the second location includes a gas conduit.

[0097] Implementation Scheme 24. The method according to any one of Implementation Schemes 1-23, wherein detecting the degraded tracer composition comprises capturing the degraded tracer composition on a filter.

[0098] Implementation Scheme 25. The method according to any one of Implementation Schemes 1-24, wherein detecting the degraded tracer composition comprises detecting the fluorescent dye using a fluorometer.

[0099] Implementation Scheme 26. The method according to any one of Implementation Schemes 1-25, wherein detecting the degraded tracer composition comprises detecting the metal oxide using an X-ray fluorescence spectrometer.

[0100] Implementation Scheme 27. A yield-enhancing treatment liquid, the yield-enhancing treatment liquid comprising an aqueous medium and a tracer composition, wherein the tracer composition is suspended in the aqueous medium; and

[0101] The tracer composition comprises a degradable polymer and a detectable component, wherein the detectable component includes: a particulate metal oxide; and a fluorescent dye disposed on the surface of the particulate metal oxide.

[0102] Implementation Scheme 28. The production enhancement treatment liquid according to Implementation Scheme 27, wherein the production enhancement treatment liquid further comprises acid.

[0103] Implementation Scheme 29. The production enhancement treatment liquid according to Implementation Scheme 28, wherein the acid includes hydrofluoric acid, hydrochloric acid, or both.

[0104] Implementation Scheme 30. The production enhancement treatment fluid according to any one of Implementation Schemes 27-29, wherein the aqueous medium includes produced water.

[0105] Other embodiments are also within the scope of the appended claims.

Claims

1. A method for tracing gas flow in a hydrocarbon reservoir, the method comprising: A tracer composition is introduced at a first location in the reservoir, wherein the tracer composition comprises a degradable polymer and a detectable component; The tracer composition is brought into contact with the reservoir to hydrolyze the degradable polymer; as well as The degraded tracer composition was detected in a gas sample collected at a second location in the reservoir, wherein the degraded tracer composition comprises a hydrolyzed polymer and the detectable component; The detectable components include: Particulate metal oxides; and Fluorescent dyes are disposed on the surface of the particulate metal oxide.

2. The method of claim 1, wherein the degradable polymer comprises thermoplastic.

3. The method of claim 2, wherein the thermoplastic comprises poly(lactic acid).

4. The method of claim 1, wherein the degradable polymer comprises a thermoplastic polyester elastomer.

5. The method of claim 4, wherein the thermoplastic polyester elastomer comprises a block copolymer containing hard segments and soft segments.

6. The method of claim 5, wherein the hard segment comprises polyethylene terephthalate, propylene terephthalate, butylene terephthalate, or any combination thereof.

7. The method of claim 5, wherein the soft segment comprises polyether, polyester, polycarbonate, or any combination thereof.

8. The method of claim 7, wherein the soft segment comprises a polyether, and the polyether comprises a polyoxyalkylene glycol.

9. The method of claim 1, wherein the fluorescent dye is detectable in the visible spectrum.

10. The method of claim 9, wherein the fluorescent dye comprises thallium dye.

11. The method of claim 10, wherein the sulfonate dye comprises rhodamine dye.

12. The method according to claim 1, wherein the metal oxide comprises aluminum hydroxide.

13. The method of claim 1, wherein the fluorescent dye is covalently bonded to the surface of the particulate metal oxide.

14. The method of claim 1, wherein the average size of the particulate metal oxide is about 10 nm to about 10 µm.

15. The method of claim 1, wherein the tracer composition comprises an extrusion of the degradable polymer and the detectable component.

16. The method of claim 1, wherein the tracer composition comprises particles with an average size of at least about 5 mm.

17. The method of claim 16, wherein the particles of the tracer composition comprise granules or fibers.

18. The method of claim 17, wherein the particles comprise fibers with an average length of at least about 4 mm.

19. The method of claim 16, wherein the degraded tracer composition comprises particles with an average size of less than about 2 mm.

20. The method of claim 19, wherein the particles of the degraded tracer composition comprise powder.

21. The method of claim 1, wherein introducing the tracer composition comprises pumping a production enhancement treatment fluid containing the tracer composition into the reservoir at the first location.

22. The method of claim 21, wherein the yield-enhancing treatment liquid comprises acid.

23. The method of claim 1, wherein the second location comprises a gas conduit.

24. The method of claim 1, wherein detecting the degraded tracer composition comprises capturing the degraded tracer composition on a filter.

25. The method of claim 1, wherein detecting the degraded tracer composition comprises detecting the fluorescent dye using a fluorometer.

26. The method of claim 1, wherein detecting the degraded tracer composition comprises detecting the metal oxide using an X-ray fluorescence spectrometer.

27. A yield-enhancing treatment solution, said yield-enhancing treatment solution comprising an aqueous medium and a tracer composition, wherein... The tracer composition is suspended in the aqueous medium; and The tracer composition comprises a degradable polymer and a detectable component, wherein the detectable component includes: Particulate metal oxides; and Fluorescent dyes are disposed on the surface of the particulate metal oxide.

28. The yield-enhancing treatment solution according to claim 27, wherein the yield-enhancing treatment solution further comprises acid.

29. The production enhancement treatment liquid according to claim 28, wherein the acid comprises hydrofluoric acid, hydrochloric acid, or both.

30. The production enhancement treatment fluid according to claim 27, wherein the aqueous medium comprises produced water.

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