System and method for distributed fiber optics sensing

Abstract

Various embodiments provide systems that include an optical cable deployable in a wellbore. At least a first plasmonic element and a second plasmonic element are associated with the optical fiber cable at a first location and a second location, respectively. The system further includes an optical interrogator system configured to: transmit an outgoing light into the optical fiber cable; and receive an incoming light corresponding to the outgoing light.

Description

SYSTEM AND METHOD FOR DISTRIBUTED FIBER OPTICS SENSINGBACKGROUND

[0001] Pressure and temperature measurement is used in many applications in, for example, the oil and gas industry and in the chemical engineering industry. As an example, in the oil and gas industry, knowledge of the downhole pressure and temperature is helpful in flow profiling and monitoring, hydraulic fracture monitoring, and leak detection. Methods to measure the pressure and temperature downhole using single point sensor(s) are known. Further, distributed pressure and / or temperature sensing has been reported using arrays of single point sensor(s). However, there remains a need for alternative distributed pressure and / or temperature sensing systems and methods that can extend the range of distributed fiber optic measurements.SUMMARY

[0002] 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.

[0003] Various embodiments provide systems that include an optical cable deployable in a wellbore. At least a first plasmonic element and a second plasmonic element are associated with the optical fiber cable at a first location and a second location, respectively. The first plasmonic element may be one of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, or a pressure and temperature sensitive plasmonic element. The second plasmonic element may be one of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, or a pressure and temperature sensitive plasmonic element. The system further includes an optical interrogator system configured to: transmit an outgoing light into the optical fiber cable; and receive an incoming light corresponding to the outgoing light. The incoming light includes information corresponding to at least one interaction between the outgoing light and at least one of the first plasmonic element and the second plasmonic element.

[0004] Some embodiments provide methods that include: deploying an optical fiber cable in a wellbore. The fiber optic cable includes at least a first plasmonic element and a second plasmonic element at a first location and a second location, respectively. The first plasmonic element may be one of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, or a pressure and temperature sensitive plasmonic element. The second plasmonic element may be one of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, or a pressure and temperature sensitive plasmonic element. The methods further include transmitting an outgoing light into the optical fiber cable and receiving an incoming light corresponding to the outgoing light. The incoming light includes information corresponding to at least one interaction between the outgoing light and at least one of the first plasmonic element and the second plasmonic element. The methods further include processing the incoming light to yield a measurement.

[0005] Other embodiments, aspects and / or advantages of the claimed subject matter will be apparent from the following description and the appended claims.BRIEF DESCRIPTION OF DRAWINGS

[0006] Specific embodiments of the disclosed technology will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency.

[0007] FIG. 1 depicts an optical fiber cable including a plurality of plasmonic elements distributed across its length in accordance with some embodiments, where the optical fiber cable extends from an optical interrogator system into a wellbore.

[0008] FIGs. 2A-2B show detail of an optical fiber cable including plasmonic elements in accordance with various embodiments.

[0009] FIGs. 3A-3B depict graphene based plasmonic elements within tapered sections of an optical fiber cable in accordance with various embodiments.

[0010] FIGs. 3C-3D depict graphene based plasmonic elements implemented on a non-tapered optical fiber cable in accordance with some embodiments.

[0011] FIGs. 4A-4B depict carbon nanotube based plasmonic elements within tapered sections of an optical fiber cable in accordance with various embodiments.

[0012] FIGs. 4C-4D depict carbon nanotube based plasmonic elements implemented on a non- tapered optical fiber cable in accordance with some embodiments.

[0013] FIG. 5 is a flow diagram showing a method in accordance with some embodiments for measuring properties within a wellbore.DETAILED DESCRIPTION

[0014] Various embodiments of the disclosure will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency.

[0015] In the following detailed description of embodiments of the disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the disclosure. However, it will be apparent to one of ordinary skill in the art that the disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0016] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as an adjective for an element (i.e., any noun in the application). The use of ordinal numbers is not to imply or create any particular ordering of the elements nor to limit any element to being only a single element unless expressly disclosed, such as using the terms "before", "after", "single", and other such terminology. Rather, the use of ordinal numbers is to distinguish between the elements. By way of an example, a first element is distinct from a second element, and the first element may encompass more than one element and succeed (or precede) the second element in an ordering of elements.

[0017] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “cell” includes reference to one or more of such cells.

[0018] Terms such as “approximately,” “substantially,” etc., mean that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0019] It is to be understood that one or more of the elements shown in the flowchart may be omitted, repeated, and / or performed in a different order than the order shown. Accordingly, the scope disclosed herein should not be considered limited to the specific arrangement of steps shown in the flowchart.

[0020] Although multiple dependent claims are not introduced, it would be apparent to one of ordinary skill that the subject matter of the dependent claims of one or more embodiments may be combined with other dependent claims.

[0021] In the following description of FIGs. 1-5, any component described with regard to a figure, in various embodiments disclosed herein, may be equivalent to one or more like-named components described with regard to any other figure. For brevity, descriptions of these components may not be repeated with regard to each figure. Thus, each and every embodiment of the components of each figure is incorporated by reference and assumed to be optionally present within every other figure having one or more like-named components. Additionally, in accordance with various embodiments disclosed herein, any description of the components of a figure is to be interpreted as an optional embodiment which may be implemented in addition to, in conjunction with, or in place of the embodiments described with regard to a corresponding like-named component in any other figure.

[0022] Various embodiments disclosed herein provide distributed pressure and / or temperature sensing within a wellbore. Pressure and temperature measurement are useful in many applications in the oil and gas industry, and chemical processing industries. In the oil and gas industry, knowledge of the downhole pressure and temperature (i.e., pressure and temperature within a wellbore) may be used, for example, in flow profiling and monitoring, hydraulic fracture monitoring, and / or leak detection. Some embodiments use pressure and / or temperature sensitive plasmonic elements attached to and / or integrated into an optical fiber cable. The pressure and / or temperature sensitivity of the plasmonic elements results from the plasmon , resonance properties of the elements. In operation, a light pulse is transmittedthrough the optical fiber cable by an optical interrogator system. The light pulse is affected by its interaction with the plasmon resonance of the plasmonic elements causing reflection and backscattering of the light pulse. The returning light is analyzed to separate effects due to pressure and / or temperature effects on the plasmonic elements, and thereby yield a distributed pressure and / or temperature measurement for the wellbore in which the optical fiber cable is deployed. The returning light received by an optical interrogation system may be returned by reflection where the optical fiber cable is a single ended fiber cable (i.e., a one-way cable), or may be returned by both reflection and continued transmission where the optical fiber cable is a U-shaped cable having an optical path extending from the optical interrogator system to a U-turn section and then returning from the U-turn section back to the optical interrogator system (i.e., a round trip cable).

[0023] Turning to FIG. 1 , an optical fiber cable 120 is shown deployed within a wellbore 110. Wellbore 1 10 extends through various strata and into a subterranean formation 115. Optical fiber cable 120 includes a plurality of plasmonic elements each at a respective distributed sensor location 125 (shown as dots along optical fiber cable 120). In some embodiments, distributed sensor location 125 are equally distributed across the entire length of optical fiber cable 120. In various embodiments, distributed sensor location 125 are equally distributed across only one or more portions of the length of optical fiber cable 120. As more fully described below, the plasmonic elements located at distributed sensor locations 125 may be pressure sensitive plasmonic elements, temperature sensitive plasmonic elements, or pressure and temperature sensitive plasmonic elements.

[0024] As used herein, the phrase “optical fiber cable” is used in its broadest sense to mean any cable capable of transmitting a light signal. Thus, an optical fiber cable may be, but is not limited to, a fiber-optic cable, an optical waveguide cable, an optical ribbon, or the like. Such an optical fiber cable may be just bare fiber or may be surrounded by an insulated casing. Further, such an optical fiber cable may include only a single optically conductive strand or two or more optically conductive strands. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of optical fiber cables that may be used in relation to different embodiments.

[0025] While shown as free floating within wellbore 110, optical fiber cable 120 may be either free floating within wellbore 110 or may be fastened or integrated within wellbore 110. Forexample, optical fiber cable 120 may be attached to a casing within wellbore 110 or otherwise incorporated into or with one or more fixed elements within wellbore 110.

[0026] An optical interrogation system 130 is deployed near an entrance to wellbore 110 and is optically connected to optical fiber cable 120. Optical interrogation system 130 is configured to transmit a light signal as outgoing light through optical fiber cable 120. This outgoing light may be a single light pulse or a series of light pulses. In some embodiments, the outgoing light may be a pulsed light generated by, for example, a pulsed laser. The outgoing light includes one or more known characteristics, such as, for example, an amplitude, a phase, and a frequency.

[0027] Optical interrogation system 130 is further configured to receive a light signal or an incoming light corresponding to the outgoing light. The incoming light includes characteristics that may be related to those of the outgoing light including, but not limited to, an amplitude, a phase, a frequency shift, an amplitude and frequency spectra, or the like. The incoming light corresponds to the outgoing light as it may include elements of reflection and backscattering of the transmitted light signal. Again, the incoming light received by optical interrogation system 130 may be returned by reflection where optical fiber cable 120 is a single ended fiber cable (i.e., a one-way cable), and / or may be returned by continued transmission where optical fiber cable 120 is a U-shaped cable having an optical path extending from optical interrogator system 130 to a U-turn section and then returning from the U-turn section back to optical interrogator system 130 (i.e., a round trip cable).

[0028] Optical interrogation system 130 may be any optical interrogation system known in the art that can be configured to separate pressure and / or temperature data from light received from an optical fiber cable having plasmonic elements in accordance with embodiments discussed herein. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of optical interrogation systems that may be used in relation to different embodiments.

[0029] In operation, optical fiber cable 120 is deployed in wellbore 110. This may include, but is not limited to, guiding optical fiber cable 120 as it is moved farther into wellbore 110. Any approach known in the art for deploying a cable into a wellbore may be used in relation to different embodiments. Once deployed, optical interrogation system 130 transmits outgoing light (e.g., a light pulse) with known characteristics (e.g., an amplitude, a frequency, and aphase) into optical fiber cable 120. This outgoing light interacts with one or more of the plasmonic elements included in optical fiber cable 120. In some cases, optical interrogation system 130 repeats light pulses periodically to facilitate repetition of measurements based upon returned light over time.

[0030] Optical interrogation system 130 detects incoming light (i.e., received light signal) received from optical fiber cable 120. Where only a single ended fiber cable (i.e., a one-way cable) is used, the incoming light is limited to the portion of the outgoing light (i.e., transmitted light) pulse that is reflected back. In contrast, where a U-shaped cable having a fiber cable extends to a U-turn section and returns from the U-turn section back to optical interrogator system 130 (i.e., a round trip cable) is used, the incoming light may include both the portion of the outgoing light pulse that is reflected back and the portion of the outgoing light that propagates from the input end of the U-shaped cable to the output end of the U-shaped cable.

[0031] Optical interrogation system 130 processes the incoming light to yield a measurement. The measurement may be: a distributed pressure measurement, a distributed temperature measurement, or a distributed pressure and temperature measurement. The variation of the characteristics of the incoming light relative to the outgoing light can be measured and assessed. Such measurement and assessment may include, but is not limited to, assessing reflected signal characteristics exhibited in the incoming light across an array of channels or time. The reflected characteristics may include, but are not limited to, an amplitude, a phase, a frequency shift, and / or an amplitude and frequency spectra. Alternatively or in addition, such measurement and assessment may include processing the incoming light by removing a part of the incoming light that is unrelated to the pressure and the temperature within wellbore 110. Yet further, such measurement and assessment may additionally or alternatively include determining pressure using a known relationship between temperature and pressure or determining temperature using the known relationship between temperature and pressure. In some embodiments, processing the incoming light may include detecting a change in the incoming light or a characteristic of the incoming light over time, and deducing information about a pressure and / or temperature change based upon the detected change. Any signal processing techniques known in the art for separating information from a light signal may be used in relation to the various embodiments.

[0032] Turning to FIG. 2A, detail of optical fiber cable 120 is shown having tapered sections in accordance with various embodiments. As shown, optical fiber cable 120 includes a number of tapered sections (e.g., a tapered section 205 and a tapered section 215) that are each located at a respective distributed sensor location 125. Tapered section 205 is part of a section 201 of optical fiber cable 120, and tapered section 215 is part of a section 211 of optical fiber cable 120. In some embodiments, a diameter of tapered section 205 is less than ninety (90) percent of a diameter of the non-tapered part of section 201, and a diameter of tapered section 215 is less than ninety (90) percent of a diameter of the non-tapered part of section 211. In various embodiments, a diameter of tapered section 205 is less than seventy-five (75) percent of a diameter of the non-tapered part of section 201, and a diameter of tapered section 215 is less than seventy-five (75) percent of a diameter of the non-tapered part of section 211. In some embodiments, a diameter of tapered section 205 is less than fifty (50) percent of a diameter of the non-tapered part of section 201, and a diameter of tapered section 215 is less than fifty (50) percent of a diameter of the non-tapered part of section 21 1.

[0033] In some embodiments, the same type of plasmonic element (not shown) is implemented in both tapered section 205 and tapered section 215. The type of plasmonic element may be, but is not limited to, a graphene based plasmonic element, a carbon nanotube (CNT) based plasmonic element, and tapered section based plasmonic element. A tapered section based plasmonic element relies upon the interaction of light with a tapered section of optical fiber cable 120 due to the differential impact of pressure and / or temperature on the tapered section compared with non-tapered areas of optical fiber cable 120. In some cases, the plasmon and surface plasmon phenomena are used which involve the quantum states of collective movement of electron plasma. This plasma interacts with the light propagating inside the fiber. The surface properties affect the properties of surface plasmons. Hence, tapered and non-tapered parts affect surface plasmons and their interaction with the light by altering their properties, because of different geometry and properties of tapered and non- tapered parts.

[0034] In some such embodiments, the type of plasmonic element implemented in tapered section 205 is a different from the type of plasmonic element deployed in tapered section 215. As an example, the type of plasmonic element deployed in tapered section 205 may be a carbon nanotube based plasmonic element and the type of plasmonic element deployed in taperedsection 215 may be a graphene based plasmonic element. Examples of graphene based plasmonic elements deployed in a tapered section are discussed below in relation to FIGs. 3A- 3B. Examples of carbon nanotube based plasmonic elements deployed in a tapered section are discussed below in relation to FIGs. 4A-4B.

[0035] Turning to FIG. 2B, detail of optical fiber cable 120 is shown that does not include tapered sections in accordance with other embodiments. As shown, optical fiber cable 120 exhibits the same diameter at each of the distributed sensor locations 125. A plasmonic element (not shown) is implemented at a section 221 of optical fiber cable 120, and another plasmonic element (not shown) is implemented at a section 221 of optical fiber cable 120. In some embodiments, the same type of plasmonic element (not shown) is implemented in both section 221 and section 231. The type of plasmonic element may be, but is not limited to, a graphene based plasmonic element or a carbon nanotube based plasmonic element. In other embodiments, the type of plasmonic element implemented at section 221 is a different from the type of plasmonic element deployed at tapered section 231. As an example, the type of plasmonic element deployed at section 221 may be a carbon nanotube based plasmonic element and the type of plasmonic element deployed at section 231 may be a graphene based plasmonic element. Examples of graphene based plasmonic elements deployed on a non- tapered cable are discussed below in relation to FIGs. 3C-3D. Examples of carbon nanotube based plasmonic elements on a non-tapered cable are discussed below in relation to FIGs. 4C- 4D.

[0036] Turning to FIG. 3A, a graphene based plasmonic element 305 is shown deployed in tapered section 205 in accordance with some embodiments. Graphene based plasmonic element 305 includes a graphene layer 307 deposited directly onto optical fiber cable 120 at tapered section 215. In some embodiments, the region of tapered section 205 including graphene layer 307 will be exposed to the environment within wellbore 110. In other embodiments, the region of tapered section 205 including graphene layer 307 is protected by another layer and / or cladding. In some embodiments chemical vapor deposition (CVD) is used to deposit the graphene. In other embodiments, optical deposition is used to deposit the graphene. In yet other embodiments, an optically induced graphene coating is applied. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments to place the graphene for graphene based plasmonic element 305. In some embodiments, the graphene layer is protectedby a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene, and thus the previously deposited graphene is not affected. In other embodiments, carbon / graphene formation can be laser-induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0037] In operation, plasmons are created in graphene layer 307 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0038] Turning to FIG. 3B, another graphene based plasmonic element 315 is shown deployed in tapered section 205 in accordance with some embodiments. Graphene based plasmonic element 315 includes a graphene layer 317 deposited onto a substrate 319. Tn some embodiments CVD is used to deposit the graphene. In other embodiments, optical deposition is used to deposit the graphene. In yet other embodiments, an optically induced graphene coating is applied. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments to place the graphene for graphene based plasmonic element 305. In some embodiments, the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene, and thus the previously deposited graphene is not affected. In other embodiments, carbon / graphene formation can be laser- induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0039] Substrate 319 is connected to optical fiber cable 120 at tapered section 215. Substrate319 may be any material compatible with depositing a thin layer of carbon and attachable toan optical cable. Any method known in the art for depositing substrate 319 on optical fiber cable 120 or of attaching substrate 319 to optical fiber cable 120 may be used. In some embodiments, the region of tapered section 205 including graphene layer 317 is exposed to the environment. In other embodiments, the region of tapered section 205 including graphene layer 317 is protected by another layer and / or cladding. In some embodiments, the substrate is formed on the optical fiber cable by flash evaporation. This remains in place on the optical fiber cable due to inter-atomic interactions. In various embodiments, the substrate is formed of Cu. In other embodiments, the substrate is formed of Si or SiO2. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of substrate materials that may be used in relation to different embodiments. In some embodiments, substrate 319 and / or the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene and / or substrate formation, and thus the previously deposited graphene and / or formed graphene is not affected. In other embodiments, carbon / graphene formation can be laser-induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0040] In operation, plasmons are created in graphene layer 317 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0041] Turning to FIG. 3C, yet another graphene based plasmonic element 325 is shown implemented directly on a surface of optical fiber cable 120 at section 221 of optical fiber cable 120. Graphene based plasmonic element 325 includes a graphene layer 327 deposited directly onto optical fiber cable 120. In other embodiments, optical deposition is used to deposit the graphene. In yet other embodiments, an optically induced graphene coating is applied. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments toplace the graphene for graphene based plasmonic element 305. In some embodiments, the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene, and thus the previously deposited graphene is not affected. In other embodiments, carbon / graphene formation can be laser- induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0042] Any method for depositing graphene may be used including, but not limited to, optical deposition as is known in the art. In some embodiments, section 221 including graphene layer 327 will be exposed to the environment in wellbore 110. In other embodiments, section 221 including graphene layer 327 is protected by another layer and / or cladding. In operation, plasmons are created in graphene layer 327 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0043] Turning to FIG. 3D, a further graphene based plasmonic element 335 is shown implemented on a substrate 339 that is attached to a surface of optical fiber cable 120 at section 221 of optical fiber cable 120. Graphene based plasmonic element 335 includes a graphene layer 337 deposited on substrate 339. In some embodiments CVD is used to deposit the graphene. In other embodiments, optical deposition is used to deposit the graphene. In yet other embodiments, an optically induced graphene coating is applied. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments to place the graphene for graphene based plasmonic element 305. In some embodiments, the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene, and thus the previously deposited graphene is not affected. In other embodiments, carbon / graphene formation can be laser-induced on the fiber from thesurrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0044] Substrate 339 is attached to optical fiber cable 120. Substrate 339 may be any material compatible with depositing a thin layer of carbon and atachable to an optical cable. Any method known in the art for depositing substrate 339 on optical fiber cable 120 or of attaching substrate 339 to optical fiber cable 120 may be used. In some embodiments, section 221 including graphene layer 337 is exposed to the environment. In other embodiments, section 221 including graphene layer 337 is protected by another layer and / or cladding. In some embodiments, the substrate is formed on the optical fiber cable by flash evaporation. This remains in place on the optical fiber cable due to inter-atomic interactions. In various embodiments, the substrate is formed of Cu. In other embodiments, the substrate is formed of Si or SiO2. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of substrate materials that may be used in relation to different embodiments. In some embodiments, substrate 339 and / or the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene and / or substrate formation, and thus the previously deposited graphene and / or formed graphene is not affected. In other embodiments, carbon / graphene formation can be laser-induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0045] In operation, plasmons are created in graphene layer 337 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0046] Turning to FIG. 4A, a carbon nanotube based plasmonic element 405 is shown deployed in tapered section 205 in accordance with some embodiments. Carbon nanotubebased plasmonic element 405 includes carbon nanotubes 407 deposited directly onto optical fiber cable 120 at tapered section 215. In some embodiments, the region of tapered section 205 including carbon nanotubes 407 is exposed to the environment. In other embodiments, the region of tapered section 205 including carbon nanotubes 407 is protected by another layer and / or cladding. In some embodiments CVD is used to deposit the CNTs. In other embodiments, optical deposition is used to deposit the CNTs. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments to place the CNTs. In some embodiments, the CNTs are protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the CNTs, and thus the previously deposited CNTs are not affected. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited CNTs from environmental factors.

[0047] In operation, plasmons are created in carbon nano tubes 407 when light traversing optical fiber cable 120 interacts with the carbon nanotubes. As carbon nanotubes have electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0048] Turning to FIG. 4B, another carbon nanotube based plasmonic element 415 is shown deployed in tapered section 205 in accordance with some embodiments. Carbon based nanotube plasmonic element 415 includes a carbon nanotubes 417 deposited onto a substrate 419. Any method for depositing CNTs on substrate 419 may be used including, but not limited to, optical deposition or chemical vapor deposition as are known in the art. Substrate 419 is connected to optical fiber cable 120 at tapered section 215. Substrate 419 may be any material compatible with depositing a thin layer of carbon and attachable to an optical cable. Any method known in the art for depositing substrate 419 on optical fiber cable 120 or of attaching substrate 419 to optical fiber cable 120 may be used. In some embodiments, the region of tapered section 205 including carbon nanotubes 417 is exposed to the environment. In other embodiments, the region of tapered section 205 including carbon nanotubes 417 is protectedby another layer and / or cladding. In some embodiments, the substrate is formed on the optical fiber cable by flash evaporation. This remains in place on the optical fiber cable due to interatomic interactions. In various embodiments, the substrate is formed of Cu. In other embodiments, the substrate is formed of Si or SiO2. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of substrate materials that may be used in relation to different embodiments. In some embodiments, substrate 419 and / or the CNTs are protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the CNTs and / or substrate formation, and thus the previously deposited CNTs are not affected. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0049] In operation, plasmons are created in carbon nanotubes 417 when light traversing optical fiber cable 120 interacts with the carbon nano tubes. As carbon nano tubes have electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0050] Turning to FIG. 4C, yet another carbon nanotube based plasmonic element 425 is shown implemented directly on a surface of optical fiber cable 120 at section 221 of optical fiber cable 120. Carbon nanotube based plasmonic element 425 includes a carbon nanotubes 427 deposited directly onto optical fiber cable 120. Any method for depositing or attaching carbon nanotubes to optical fiber cable 120 may be used including, but not limited to, optical deposition as is known in the art. In some embodiments, section 221 including carbon nanotubes 427 will be exposed to the environment within wellbore 110. In other embodiments, section 221 including carbon nanotubes 427 is protected by another layer and / or cladding. In some embodiments CVD is used to deposit the CNTs. In other embodiments, optical deposition is used to deposit the CNTs. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches that may be used in relation to different embodiments to place the CNTs. In some embodiments, the CNTs are protected bya surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the CNTs, and thus the previously deposited CNTs are not affected. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited CNTs from environmental factors.

[0051] In operation, plasmons are created in carbon nanotubes 427 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0052] Turning to FIG. 4D, a further carbon nanotube based plasmonic element 435 is shown implemented on a substrate 439 that is attached to a surface of optical fiber cable 120 at section 221 of optical fiber cable 120. Carbon nanotube based plasmonic element 435 includes a carbon nanotubes 437 deposited on substrate 439. Any method for depositing graphene on substrate 439 may be used including, but not limited to, optical deposition or chemical vapor deposition as are known in the art. Substrate 439 is attached to optical fiber cable 120. Substrate 439 may be any material compatible with depositing a thin layer of carbon and attachable to an optical cable. Any method known in the art for depositing substrate 439 on optical fiber cable 120 or of attaching substrate 439 to optical fiber cable 120 may be used. In some embodiments, section 221 including carbon nanotubes 437 is exposed to the environment. In other embodiments, section 221 including carbon nanotubes 437 is protected by another layer and / or cladding. In some embodiments, the substrate is formed on the optical fiber cable by flash evaporation. This remains in place on the optical fiber cable due to inter- atomic interactions. In various embodiments, the substrate is formed of Cu. In other embodiments, the substrate is formed of Si or SiO2. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of substrate materials that may be used in relation to different embodiments. In some embodiments, substrate 439 and / or the graphene layer is protected by a surrounding insulation later or cladding. In some embodiments, the surrounding insulation layer or cladding is formed at temperatures substantially lower than those used to deposit the graphene and / or substrate formation, andthus the previously deposited graphene and / or formed graphene is not affected. In other embodiments, carbon / graphene formation can be laser-induced on the fiber from the surrounding insulation layer or cladding itself. Based upon the disclosure provided herein, one of ordinary skill in the art will recognize a variety of approaches for protecting the deposited graphene from environmental factors.

[0053] In operation, plasmons are created in carbon nano tubes 437 when light traversing optical fiber cable 120 interacts with the graphene. As graphene has electrical and magnetic properties that are sensitive to the pressure and temperature, the plasmons are affected by the ambient pressure and / or temperature resulting in pressure and / or temperature induced changed in the light received by optical interrogation system 130. In some embodiments, the change is in the light received by optical interrogation system 130 includes a frequency shift when compared with the light transmitted by optical interrogation system 130.

[0054] Turning to FIG. 5, a flow diagram 500 shows a method in accordance with some embodiments for measuring properties within a wellbore. Following flow diagram 500, an optical fiber cable is deployed in a wellbore (block 505). The optical fiber cable includes at least a first plasmonic element at a first location on the optical fiber cable and a second plasmonic element at a first location on the optical fiber cable. Each of the first plasmonic element and the second plasmonic element may be one of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, or a pressure and temperature sensitive plasmonic element.

[0055] Outgoing light is transmitted into the optical fiber cable (block 510). The outgoing light exhibits known characteristics including, but not limited to, an amplitude, a frequency, and phase. In some embodiments, the outgoing light is a light pulse or a short burst of light. In some embodiments, the outgoing light is periodically repeated to facilitate repetition of measurements based upon reflected light over time.

[0056] Incoming light is received from the optical fiber cable (block 515). The incoming light includes information corresponding to at least one interaction between the outgoing light and at least one of the first plasmonic element and the second plasmonic element. In particular, the light traversing the optical fiber cable causes an excitation of plasmons in the various plasmonic elements. The coupling of the propagating output light with plasmons may affect one or more characteristics of the light including, for example, a frequency shift of theincoming light relative to the outgoing light, an attenuation of amplitude of the incoming light relative to the outgoing light, a spectrum of the incoming light relative to the outgoing light, and / or a phase shift of the incoming light relative to the outgoing light. The sensitivity of the plasmons (e.g., by changing graphene, or carbon nanotubes) due pressure and / or temperature results in the variation of characteristics of the incoming light relative to the outgoing light.

[0057] Where only a single ended fiber cable (i.e., a one-way cable), the incoming light is limited to the portion of the outgoing light that is reflected back. In contrast, where a U-shaped cable having a fiber cable extends to a U-turn section and returns from the U-turn section back to the optical interrogator system (i.e., a round trip) is used, the incoming light may include both the portion of the outgoing light that is reflected back and the portion of the outgoing light that propagates from the input end of the U-shaped cable to the output end of the U- shaped cable.

[0058] The incoming light is processed to yield a measurement (block 520). The measurement may be: a distributed pressure measurement, a distributed temperature measurement, or a distributed pressure and temperature measurement. The variation of the characteristics of the incoming light relative to the outgoing light can be measured and assessed. Such measurement and assessment may include, but is not limited to, assessing reflected signal characteristics exhibited in the incoming light across an array of channels. The reflected signal characteristics may include, but are not limited to, an amplitude, a phase, a frequency shift, and / or an amplitude and frequency spectra. Additionally or alternatively, such measurement and assessment may include processing the incoming light by removing a part of the incoming light that is unrelated to pressure and temperature within the wellbore. Yet further, such measurement and assessment may additionally or alternatively include determining pressure using a known relationship between temperature and pressure, or determining temperature using the known relationship between temperature and pressure. In some embodiments, processing the incoming light may include detecting a change in the incoming light or a characteristic of the incoming light over time, and deducing information about the pressure and / or temperature change based upon the detected change.

[0059] By processing different channels (e.g., based on the travel time of the pulse), the information about different parts of the optical fiber cable can be obtained. The changes can be due not only to the pressure and / or temperature change, but to other factors as well. In someembodiments, it is possible to assess pressure and temperature simultaneously through use of several characteristics of the incoming light (e.g., frequency shift and attenuation).

[0060] Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

CLAIMSWhat is claimed:

1. A system, comprising: an optical fiber cable deployable in a wellbore; a first plasmonic element associated with the optical fiber cable at a first location, wherein the first plasmonic element is selected from a group consisting of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, and a pressure and temperature sensitive plasmonic element; a second plasmonic element associated with the optical fiber cable at a second location, wherein the second plasmonic element is selected from a group consisting of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, and a pressure and temperature sensitive plasmonic element; and an optical interrogator system configured to: transmit an outgoing light into the optical fiber cable; and receive an incoming light corresponding to the outgoing light, wherein the incoming light includes information corresponding to at least one interaction between the outgoing light and at least one of the first plasmonic element and the second plasmonic element.

2. The system of claim 1, wherein the optical interrogator system is further configured to: process the incoming light to separate a pressure data from the incoming light to yield distributed pressure measurements within the wellbore.

3. The system of claim 1, wherein the optical interrogator system is further configured to: process the incoming light to separate a temperature data from the incoming light to yield distributed temperature measurements within the wellbore.

4. The system of claim 1, wherein the optical interrogator system is further configured to: remove a part of the incoming light unrelated to one or more of temperature and pressure.

5. The system of claim 1 , wherein the incoming light comprises one or more signal characteristics selected from the group consisting of: an amplitude, a phase, a frequency shift, an amplitude spectrum, and a frequency spectrum.

6. The system of claim 1, wherein the first plasmonic element is physically coupled to the optical fiber cable at the first location.

7. The system of claim 6, wherein the first plasmonic element comprises a material selected from the group consisting of: graphene, carbon nanotubes, and a combination of graphene and carbon nanotubes.

8. The system of claim 1, wherein the optical fiber cable is tapered at the first location, and wherein the first plasmonic element is integrated into the taper.

9. The system of claim 8, wherein the first plasmonic element comprises a material selected from the group consisting of: graphene, carbon nanotubes, and a combination of graphene and carbon nanotubes.

10. The system of claim 1, wherein the first plasmonic element is a first pressure sensitive plasmonic element, and wherein a pressure sensitivity of the first pressure sensitive plasmonic element is achieved through a pressure affected plasmon resonance property affecting transfer of light though the optical fiber cable.

11. The system of claim 1 , wherein the first plasmonic element is a first temperature sensitive plasmonic element, and wherein a temperature sensitivity of the first temperature sensitive plasmonic element is achieved through a temperature affected plasmon resonance property affecting transfer of light though the optical fiber cable.

12. A method, comprising: deploying an optical fiber cable in a wellbore, wherein the optical fiber cable comprises: a first plasmonic element at a first location on the optical fiber cable, wherein the first plasmonic element is selected from a group consisting of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, and a pressure and temperature sensitive plasmonic element; a second sensitive plasmonic element at a second location on the optical fiber cable at a second location, wherein the second plasmonic element is selected from a group consisting of: a pressure sensitive plasmonic element, a temperature sensitive plasmonic element, and a pressure and temperature sensitive plasmonic element;transmitting an outgoing light into the optical fiber cable; receiving an incoming light corresponding to the outgoing light, wherein the incoming light includes information corresponding to at least one interaction between the outgoing light and at least one of the first plasmonic element and the second plasmonic element; and processing the incoming light to yield a measurement.

13. The method of claim 12, wherein the measurement is a distributed pressure measurement within the wellbore, and wherein processing the incoming light comprises: separating a pressure data component from the incoming light to yield the distributed pressure measurement.

14. The method of claim 12, wherein the measurement is a distributed temperature measurement within the wellbore, and wherein processing the incoming light comprises: separating a temperature data component from the incoming light to yield the distributed temperature measurement.

15. The method of claim 12, wherein the first plasmonic element is physically coupled to the optical fiber cable at the first location.

16. The method of claim 15, wherein the first plasmonic element comprises a material selected from the group consisting of: graphene, carbon nanotubes, and a combination of graphene and carbon nanotubes.

17. The method of claim 12, wherein the optical fiber cable is tapered at the first location, and wherein the first plasmonic element is integrated into the taper.

18. The method of claim 17, wherein the first plasmonic element comprises a material selected from the group consisting of: graphene, carbon nanotubes, and a combination of graphene and carbon nanotubes.

19. The method of claim 12, wherein the first plasmonic element is a first pressure sensitive plasmonic element, and wherein a pressure sensitivity of the first pressure sensitive plasmonic element is achieved through a pressure affected plasmon resonance property affecting transfer of light though the optical fiber cable.

20. The method of claim 12, wherein the first plasmonic element is a first temperature sensitive plasmonic element, and wherein a temperature sensitivity of the first temperature sensitive plasmonic element is achieved through a temperature affected plasmon resonance property affecting transfer of light though the optical fiber cable.

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