TECHNICAL FIELD OF THE INVENTION

[0001] This invention relates, in general, to equipment utilized in conjunction with operations performed in relation to subterranean wells and, in particular, to the use of one or more integrated computational elements to optically analyze production fluid during artificial lift operations.

BACKGROUND OF THE INVENTION

[0002] Without limiting the scope of the present invention, its background is described with reference to using an electric submersible pump during downhole artificial lift operations in a subterranean well, as an example.

[0003] It is well known in the fluid production art that certain wells have insufficient reservoir pressure to boost the production fluid to the surface. To overcome low reservoir pressure, various artificial lift techniques that increase the flow of production fluid to the surface of the well can be used. For example, the artificial lift function may be accomplished by positioning a pump in the well or by otherwise improving the lift efficiency of the well. Numerous types of pumps have been employed for artificial lift operations including plunger lifts, sucker rod pumps, progressive cavity pumps and electric submersible pumps.

[0004] In recent years, electric submersible pumps have gained popularity due to their efficiency, dependability and versatility. In fact, electric submersible pumps are considered a low-maintenance, cost-effective alternative to many of the other types of artificial lift pumps. Electric submersible pumps have proven to be suitable for operations at exceptionally high downhole temperatures and they can handle a wide range of flow rates and lift requirements. In addition, electric submersible pumps can be used when the production fluid contains chemical contaminants such as hydrogen sulfide and carbon dioxide as well as abrasive contaminants such as sand. Further, the operation of electric submersible pumps is not significantly impacted by an increase in the water cut of the production fluid.

[0005] It has been found, however, that the efficiency of electric submersible pumps can be compromised when significant gas fractions are present in the production fluid. Attempts have been made to overcome this gas fraction problem. For example, mechanical devices such as downhole gas separators or downhole gas compressors have been used to reduce the gas content of the production fluid before it enters the pump section of the electric submersible pump. It has been found, however, that the risk of over heating and damaging the pump motor when significant gas fractions are encountered still remains too high.

[0006] Therefore, a need has arisen for an improved artificial lift system that is operable to overcome insufficient reservoir pressure and increase the flow of production fluid to the surface of the well. A need has also arisen for such an improved artificial lift system that is operable for use in the hostile temperature, chemical and abrasive environments encountered downhole. Further, a need has arisen for such an improved artificial lift system, the operation of which is not compromised when significant gas fractions are present in the production fluid.

SUMMARY OF THE INVENTION

[0007] The present invention disclosed herein is directed to an improved artificial lift system that is operable to overcome insufficient reservoir pressure and increase the flow of production fluid to the surface of a well. The improved artificial lift system of the present invention is operable for use in the hostile temperature, chemical and abrasive environments encountered downhole. In addition, operation of the improved artificial lift system of the present invention is not compromised when significant gas fractions are present in the production fluid.

[0008] In one aspect, the present invention is directed to a downhole pump assembly for pumping production fluid to a surface of a well. The downhole pump assembly includes a fluid pump that is operable to pump the production fluid to the surface. An optical computing device having at least one integrated computational element is configured to optically interact with the production fluid proximate the fluid pump and is configured to generate optically interacted light. At least one detector is arranged to receive the optically interacted light and to generate an output signal corresponding to a characteristic of the production fluid.

[0009] In one embodiment, the optical computing device may include an electromagnetic radiation source. In this embodiment, the electromagnetic radiation source may be a light source selected from the group consisting of a broad spectrum light source, an infrared light source and a near-infrared light source. In some embodiments, a signal processor may be communicably coupled to the at least one detector. The signal processor may be configured to receive the output signal corresponding to the characteristic of the production fluid and provide a resulting output signal. In these embodiments, a downhole control system may be communicably coupled to the signal processor. The control system may be configured to receive the resulting output signal from the signal processor and adjust a state of the fluid pump in response to the resulting output signal. In certain embodiments, the resulting output signal may be indicative of the characteristic of the production fluid proximate the fluid pump. In one example, the characteristic of the production fluid may be a concentration of a substance in the production fluid such as the concentration of gas in the production fluid. In some embodiments, the fluid pump may include an electric submersible pump and an electric motor.

[0010] In another aspect, the present invention is directed to an artificial lift system for pumping production fluid to a surface of a well. The artificial lift system includes a downhole pump assembly including a fluid pump operable to pump the production fluid to the surface, an optical computing device having at least one integrated computational element configured to optically interact with the production fluid proximate the fluid pump and configured to generate optically interacted light and at least one detector arranged to receive the optically interacted light and to generate an output signal corresponding to a characteristic of the production fluid. The artificial lift system also includes a surface control system and a cable assembly that operably couples the surface control system and the downhole pump assembly. The cable assembly is configured to provide power to the fluid pump and to provide a communication path for signals between the surface control system and the optical computing device.

[0011] In one embodiment, a signal processor is communicably coupled to the at least one detector. The signal processor may be configured to receive the output signal corresponding to the characteristic of the fluid and provide a resulting output signal. In this embodiment, the surface control system may be configured to receive the resulting output signal from the signal processor and provide a commend signal to adjust a state of the fluid pump in response to the resulting output signal.

[0012] In a further aspect, the present invention is directed to a method of operating a downhole pump assembly. The method includes disposing the downhole pump assembly in a well, the downhole pump assembly including a fluid pump, at least one optical computing device having at least one integrated computational element and at least one detector; optically interacting the at least one integrated computational element with a production fluid proximate the fluid pump; generating optically interacted light corresponding to a characteristic of the production fluid; receiving the optically interacted light with the at least one detector; generating an output signal with the at least one detector, the output signal being indicative of the characteristic of the production fluid; and adjusting a state of the fluid pump responsive to the characteristic of the production fluid.

[0013] The method may also include supplying a source of electromagnetic radiation selected from the group consisting of broad spectrum light, infrared light and near-infrared light; receiving the output signal corresponding to the characteristic of the fluid with a signal processor and providing a resulting output signal from the signal processor; receiving the resulting output signal from the signal processor with a surface control system via a cable assembly and sending a control signal to adjust the state of the fluid pump from the surface control system to the fluid pump via the cable assembly; receiving the resulting output signal from the signal processor with a downhole control system and sending a control signal to adjust the state of the fluid pump from the downhole control system; and/or generating optically interacted light corresponding to a concentration of gas in the production fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:

[0015] Figure 1 is a schematic illustration of an electric submersible pump assembly positioned in a wellbore according to an embodiment of the present invention;

[0016] Figure 2 is a schematic illustration of an artificial list system including an electric submersible pump assembly positioned in a wellbore according to an embodiment of the present invention;

[0017] Figure 3 is a schematic illustration of an exemplary integrated computation element for use in an electric submersible pump assembly according to an embodiment of the present invention;

[0018] Figure 4 is a block diagram of an optical computing device including an integrated computation element for use in an electric submersible pump assembly according to an embodiment of the present invention;

[0019] Figure 5 is a schematic illustration of an optical computing device disposed in an electric submersible pump assembly positioned in a wellbore according to an embodiment of the present invention; [0020] Figure 6 is a schematic illustration an optical computing device for use in an electric submersible pump assembly according to an embodiment of the present invention; and

[0021] Figure 7 is a schematic illustration an optical computing device for use in an electric submersible pump assembly according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention, and do not delimit the scope of the present invention.

[0023] Referring initially to figure 1, an electric submersible pump assembly positioned in a well is schematically illustrated and generally designated 10. A wellbore 12 extends through the various earth strata including formation 14. A casing 16 is secured within wellbore 12. A tubing string 18 is disposed within wellbore 12. The lower end of tubing string 18 includes various tools such as a sensor subassembly 20, a fluid pump 22, a gas separator 24, a fluid intake subassembly 26, an electric motor 28, a downhole control system 30 and a sensor subassembly 32. Even though electric submersible pump assembly 10 has been described and depicted as having a particular array of components, it should be understood by those skilled in the art that other arrangements of components having a greater or lesser degree of functionality could alternatively be used without departing from the principles of the present invention. In the illustrated embodiment, a cable assembly 34 extends from the surface to provide electric power to various components of electric submersible pump assembly 10. A second cable assembly 36 is depicted as extending among various components of electric submersible pump assembly 10 to provide communication therebetween. Even though two cable assemblies have been described and depicted, it should be understood by those skilled in the art that the required power and signal capability could alternative be handled by a single cable assembly.

[0024] In operation, if artificial lift is required to boost production fluid 38 to the surface of wellbore 12, electric submersible pump assembly 10 may be lowered into wellbore 12 and positioned within production fluid 38, as depicted in figure 1. Thereafter, electric power is supplied to electric motor 28 via cable assembly 34. As electric motor 28 rotates, production fluid enters electric submersible pump assembly 10 at fluid intake subassembly 26. The production fluid then passes through gas separator 24 which separates and discharges at least a portion of the gas faction that may be present in production fluid 38 via ports 40 for production to the surface, for example, in the annulus between casing 16 and tubing string 18. The remaining portion of production fluid 38 then enters fluid pump 22, which sufficiently increases the pressure of production fluid 38 so it will flow to the surface within tubing string 18. As discussed above, the efficiency of electric submersible pumps can be compromised when a significant gas fraction is present in production fluid 38. In the present invention, one or more sensors, such as sensor subassembly 20 and/or sensor subassembly 32, which are disposed in electric submersible pump assembly 10 proximate fluid pump 22 are used to monitor and initiate corrective action if the gas fraction in production fluid 38 becomes elevated.

[0025] Preferably, sensor subassembly 20 and sensor subassembly 32 each include a source of electromagnetic radiation, at least one optical computing device having at least one integrated computational element and at least one detector. The integrated computational elements are optically interacted with production fluid 38. This optical interaction generates optically interacted light corresponding to a characteristic of production fluid 38, in this case, the concentration of gas. The optically interacted light is then received by a detector that generates an output signal indicative of the characteristic of the production fluid. This output signal may then be processed by, for example, a signal processor in downhole control system 30 or sensor subassemblies 20, 32. The signal processor then generates a resulting output signal that may be interpreted by downhole control system 30. If downhole control system 30 determines that the gas fraction information obtained by sensor subassembly 20, sensor subassembly 32 or both is elevated, downhole control system 30 may send a control or command signal to adjust a state of electric motor 28. For example, the command signal may be to reduce the speed of electric motor 28, which increases the inlet pressure thereby reducing the likelihood of gas coming out of solution prior to entering fluid pump 22. Alternatively, the command signal may be to cease operation of electric motor 28 to allow formation pressure near wellbore 12 to build up or it may be to commence operation of electric motor 28 after the formation pressure near wellbore 12 has sufficiently built up. As another alternative, the command signal may be to increase the gas separation operation by turning on additional gas separators (not pictured) or increasing the operation speed of gas separator 24. As such, the output signal indicative of the gas fraction in production fluid 38 is used to optimize the artificial lift operation and prevent unnecessary processing of gas by fluid pump 22 as well as potential damage to electric motor 28. [0026] Even though figure 1 depicts the present invention in a vertical wellbore, it should be understood by those skilled in the art that the present invention is equally well suited for use in wellbores having other directional configurations including horizontal wellbores, deviated wellbores, slanted wells, lateral wells and the like. Accordingly, it should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward, uphole, downhole and the like are used in relation to the illustrative embodiments as they are depicted in the figures, the upward direction being toward the top of the corresponding figure and the downward direction being toward the bottom of the corresponding figure, the uphole direction being toward the surface of the well and the downhole direction being toward the toe of the well.

[0027] Referring next to figure 2, an artificial lift system is schematically illustrated and generally designated 50. A wellbore 52 extends through the various earth strata including formation 54. A casing 56 is secured within wellbore 52. A tubing string 58 is disposed within wellbore 52. The lower end of tubing string 58 includes various tools such as a sensor subassembly 60, a fluid pump 62, a gas separator 64, a fluid intake subassembly 66, an electric motor 68 and a sensor subassembly 70, which may be referred to collectively as electric submersible pump assembly 72. In the illustrated embodiment, a cable assembly 74 extends from a surface control system 76 to various components of electric submersible pump assembly 72 and is operable to carry power, signal, data and the like therebetween.

[0028] In operation, if artificial lift is required to boost production fluid 78 to the surface of wellbore 52, electric submersible pump assembly 72 may be lowered into wellbore 52 and positioned within production fluid 78, as depicted in figure 2. Thereafter, electric power is supplied to electric motor 68 via cable assembly 74. As electric motor 68 rotates, production fluid enters electric submersible pump assembly 72 at fluid intake subassembly 66. The production fluid then passes through gas separator 64 which separates and discharges at least a portion of the gas faction that may be present in production fluid 78 via ports 80 for production to the surface, for example, in the annulus between casing 56 and tubing string 58 for further processing. The remaining portion of production fluid 78 then enters fluid pump 62, which sufficiently increases the pressure of production fluid 78 so it will flow to the surface within tubing string 58 for further processing. As discussed above, the efficiency of electric submersible pumps can be compromised when significant gas fractions are present in the production fluid. In the present invention, one or more sensors, such as sensor subassembly 60 and sensor subassembly 70 are used to monitor and initiate corrective action if the gas fraction in production fluid 78 becomes elevated. [0029] Preferably, sensor subassembly 60 and sensor subassembly 70 each include a source of electromagnetic radiation or may receive electromagnetic radiation from surface controller 76 via cable assembly 74. Sensor subassemblies 60, 70 also include at least one optical computing device having at least one integrated computational element and at least one detector. The integrated computational elements are optically interacted with production fluid 78. This optical interaction generates optically interacted light corresponding to a characteristic of production fluid 78, in this case, the concentration of gas. The optically interacted light is then received by a detector that generates an output signal indicative of the characteristic of the production fluid. This output signal may then be processed by, for example, a signal processor in surface controller 76 or in sensor subassemblies 60, 70. The signal processor then generates a resulting output signal that may be interpreted by surface controller 76. If surface controller 76 or an operator of surface controller 76 determines that the gas fraction information obtained by sensor subassembly 60, sensor subassembly 70 or both is elevated, surface controller 76 may send a command signal to adjust a state of electric motor 68. For example, the command signal may be to change the speed of electric motor 28 or turn electric motor 28 on or off. Alternatively, the command signal may be to change or increase the gas separation operation. As such, the output signal indicative of the gas fraction in production fluid 78 is used to optimize the artificial lift operation and prevent unnecessary processing of gas by fluid pump 62 as well as potential damage to electric motor 68.

[0030] Referring next to figure 3, an integrated computation element of an optical computing device for use in an electric submersible pump assembly of the present invention is schematically illustrated and generally designated 100. In general, the various configurations of optical computing devices, also commonly referred to as "opticoanalytical devices," are used for real-time or near real-time monitoring of production fluids. In operation, the systems and methods disclosed herein may be useful and otherwise advantageous in qualitative and quantitative determinations regarding production fluids. A significant and distinct advantage of these devices is that they can be configured to specifically detect and/or measure a particular component or characteristic of interest of a fluid, such as a gas concentration at wellbore conditions without having to undertake a time- consuming sample processing procedure. With real-time or near real-time analyses on hand, the exemplary systems and methods described herein may be able to provide some measure of proactive or responsive control over the fluid flow and enable the collection and use of fluid information in conjunction with operational information to optimize current and subsequent operations. The optical computing devices suitable for use in the present embodiments can be deployed at any fiuidly communicable points within an electric submersible pump assembly and preferably proximate to the fluid pump as depicted in figures 1 and 2. Also as shown, one or more optical computing devices can be utilized, for example, upstream and downstream of the fluid pump.

[0031] As used herein, the term "fluid" may refer to any substance that is capable of flowing, including particulate solids, liquids, gases, slurries, emulsions, powders, muds, glasses, combinations thereof, and the like. In some embodiments, the fluid can be an aqueous fluid, including water or the like. In some embodiments, the fluid can be a nonaqueous fluid, including organic compounds, more specifically, hydrocarbons, oil, a refined component of oil, petrochemical products, and the like. In some embodiments, the fluid can be a treatment fluid or a formation fluid. Fluids can include various flowable mixtures of solids, liquids and/or gases. Illustrative gases that can be considered fluids according to the present embodiments include, for example, air, nitrogen, carbon dioxide, argon, helium, methane, ethane, butane, and other hydrocarbon gases, combinations thereof and/or the like.

[0032] As used herein, the term "characteristic" may refer to a chemical, mechanical or physical property of a substance. A characteristic of a substance may include a quantitative value of one or more chemical components therein. Such chemical components may be referred to herein as "analytes." Illustrative characteristics of a substance that can be monitored with the optical computing devices disclosed herein can include, for example, chemical composition (e.g., identity and concentration in total or of individual components), impurity content, pH, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, combinations thereof, and the like.

[0033] As used herein, the term "flow path" may refer to a route through which a fluid is capable of being transported between two points. In some cases, the flow path need not be continuous or otherwise contiguous between the two points. Exemplary flow paths include, but are not limited to, a casing string, a tubing string, a path through a sensor assembly, combinations thereof, or the like. It should be noted that the term flow path does not necessarily imply that a fluid is flowing therein, rather that a fluid is capable of being transported or otherwise flowable therethrough.

[0034] As used herein, the term "substance," or variations thereof, may refer to at least a portion of a material of interest to be evaluated using the optical computing devices described herein. In some embodiments, the substance is the characteristic of interest, as defined above, and may include any integral component of the fluid flowing within the flow path. In other embodiments, the substance may be a material of interest flowing jointly with and otherwise separate from the fluid.

[0035] As used herein, the term "electromagnetic radiation" may refer to radio waves, microwave radiation, infrared and near-infrared radiation, visible light, ultraviolet light, X- ray radiation and gamma ray radiation.

[0036] As used herein, the term "optical computing device" may refer to an optical device that is configured to receive an input of electromagnetic radiation from a substance and produce an output of electromagnetic radiation from a processing element arranged within the optical computing device. The processing element may be, for example, an integrated computational element (ICE) used in the optical computing device. As discussed in greater detail below, the electromagnetic radiation that optically interacts with the processing element is changed so as to be readable by a detector, such that an output of the detector can be correlated to at least one characteristic of interest being measured or monitored in the fluid. The output of electromagnetic radiation from the processing element can be reflected electromagnetic radiation, transmitted electromagnetic radiation, and/or dispersed electromagnetic radiation. Whether reflected or transmitted electromagnetic radiation is analyzed by the detector may be dictated by the structural parameters of the optical computing device as well as other considerations known to those skilled in the art. In addition, emission and/or scattering of the substance, for example via fluorescence, luminescence, Raman scattering, and/or Raleigh scattering, can also be monitored by the optical computing devices.

[0037] As used herein, the term "optically interact" or variations thereof may refer to the reflection, transmission, scattering, diffraction or absorption of electromagnetic radiation either on, through or from one or more processing elements (i.e., integrated computational elements). Accordingly, optically interacted light refers to electromagnetic radiation that has been reflected, transmitted, scattered, diffracted or absorbed by, emitted, or re -radiated, for example, using the integrated computational elements, but may also apply to interaction with a fluid or a substance in the fluid.

[0038] In some embodiments, suitable structural components for the exemplary optical computing devices are described in commonly owned United States Patent numbers 6,198,531; 6,529,276; 7,123,844; 7,834,999; 7,911,605; 7,920,258; and 8,049,881, each of which is incorporated herein by reference in its entirety, United States Application Publication numbers 2009/0219538 and 2009/0219539, each of which is also incorporated herein by reference in its entirety and United States Patent Application number 13/456,467, which is incorporated herein by reference in its entirety. As will be appreciated, variations of the structural components of the optical computing devices described in the above -referenced patents and patent applications may be appropriate, without departing from the scope of the disclosure, and therefore, should not be considered limiting to the various embodiments disclosed herein.

[0039] The optical computing devices described in the foregoing patents and patent applications combine the advantages of the power, precision and accuracy associated with laboratory spectrometers, while being extremely rugged and suitable for downhole use. Furthermore, the optical computing devices can perform calculations (analyses) in real-time or near real-time without the need for time-consuming sample processing. In this regard, the optical computing devices can be specifically configured to detect and analyze particular characteristics and/or analytes of interest of a fluid or a substance in the fluid. As a result, interfering signals are discriminated from those of interest in the substance by appropriate configuration of the optical computing devices, such that the optical computing devices provide a rapid response regarding the characteristics of the fluid or substance as based on the detected output. In some embodiments, the detected output can be converted into a voltage that is distinctive of the magnitude of the characteristic being monitored in the fluid. The foregoing advantages and others make the optical computing devices particularly well suited for downhole use.

[0040] The optical computing devices can be configured to detect not only the composition and concentrations of a substance in a fluid, but they also can be configured to determine physical properties and other characteristics of the substance as well, based on their analysis of the electromagnetic radiation received from the substance. For example, the optical computing devices can be configured to determine the concentration of an analyte and correlate the determined concentration to a characteristic of a substance by using suitable processing means. As will be appreciated, the optical computing devices may be configured to detect as many characteristics or analytes as desired for a given substance or fluid. All that is required to accomplish the monitoring of multiple characteristics or analytes is the incorporation of suitable processing and detection means within the optical computing device for each characteristic or analyte. In some embodiments, the properties of the substance can be a combination of the properties of the analytes therein (e.g., a linear, non-linear, logarithmic and/or exponential combination). Accordingly, the more characteristics and analytes that are detected and analyzed using the optical computing devices, the more accurately the properties or concentration of the given substance will be determined. [0041] The optical computing devices described herein utilize electromagnetic radiation to perform calculations, as opposed to the hardwired circuits of conventional electronic processors. When electromagnetic radiation interacts with a substance, unique physical and chemical information about the substance may be encoded in the electromagnetic radiation that is reflected from, transmitted through or radiated from the substance. This information is often referred to as the spectral "fingerprint" of the substance. The optical computing devices described herein are capable of extracting the information of the spectral fingerprint of multiple characteristics or analytes within a substance and converting that information into a detectable output regarding the overall properties of the substance. That is, through suitable configurations of the optical computing devices, electromagnetic radiation associated with characteristics or analytes of interest in a substance can be separated from electromagnetic radiation associated with all other components of the substance in order to estimate the properties of the substance in real-time or near real-time.

[0042] As briefly mentioned above, the processing elements used in the exemplary optical computing devices described herein may be characterized as integrated computational elements (ICE). Each ICE is capable of distinguishing electromagnetic radiation related to the characteristic or analyte of interest from electromagnetic radiation related to other components of a substance. As best seen in figure 3, ICE 100 may include a plurality of alternating layers 102 and 104, such as silicon (Si) and Si0 ₂ (quartz), respectively. In general, these layers 102, 104 consist of materials whose index of refraction is high and low, respectively. Other examples might include niobia and niobium, germanium and germania, MgF, SiO, and other high and low index materials known in the art. The layers 102, 104 may be strategically deposited on an optical substrate 106. In some embodiments, the optical substrate 106 is BK-7 optical glass. In other embodiments, the optical substrate 106 may be another type of optical substrate, such as quartz, sapphire, silicon, germanium, zinc selenide, zinc sulfide, or various plastics such as polycarbonate, polymethylmethacrylate (PMMA), polyvinylchloride (PVC), diamond, ceramics, combinations thereof and the like.

[0043] At the opposite end, ICE 100 may include a layer 108 that is generally exposed to the environment of the flow path, device or installation. The number of layers 102, 104 and the thickness of each layer 102, 104 are determined from the spectral attributes acquired from a spectroscopic analysis of a characteristic of the substance using a conventional spectroscopic instrument. The spectrum of interest of a given characteristic of a substance typically includes any number of different wavelengths. It should be understood that the exemplary ICE 100 depicted in figure 3 does not in fact represent any particular characteristic of a given substance, but is provided for purposes of illustration only. Consequently, the number of layers 102, 104 and their relative thicknesses, as shown in figure 3, bear no correlation to any particular characteristic of a given substance. Nor are layers 102, 104 and their relative thicknesses necessarily drawn to scale, and therefore should not be considered limiting of the present disclosure. Moreover, those skilled in the art will readily recognize that the materials that make up each layer 102, 104 may vary, depending on the application, cost of materials and/or applicability of the material to the substance.

[0044] In some embodiments, the material of each layer 102, 104 can be doped or two or more materials can be combined in a manner to achieve the desired optical characteristic. In addition to solids, the exemplary ICE 100 may also contain liquids and/or gases, optionally in combination with solids, in order to produce a desired optical characteristic. In the case of gases and liquids, ICE 100 can contain a corresponding vessel (not shown), which houses the gases or liquids. Exemplary variations of ICE 100 may also include holographic optical elements, gratings, piezoelectric, light pipe, digital light pipe (DLP), and/or acousto-optic elements, for example, that can create transmission, reflection and/or absorptive properties of interest.

[0045] The multiple layers 102, 104 exhibit different refractive indices. By properly selecting the materials of the layers 102, 104 and their relative thickness and spacing, ICE 100 may be configured to selectively pass/reflect/refract predetermined fractions of electromagnetic radiation at different wavelengths. Each wavelength is given a predetermined weighting or loading factor. The thickness and spacing of layers 102, 104 may be determined using a variety of approximation methods from the spectrograph of the characteristic or analyte of interest. These methods may include inverse Fourier transform (IFT) of the optical transmission spectrum and structuring ICE 100 as the physical representation of the IFT. The approximations convert the IFT into a structure based on known materials with constant refractive indices. Further information regarding the structures and design of exemplary integrated computational elements (also referred to as multivariate optical elements) is provided in Applied Optics, Vol. 35, pp. 5484-5492 (1996) and Vol. 129, pp. 2876-2893, which are hereby incorporated by reference.

[0046] The weightings that layers 102, 104 of ICE 100 apply at each wavelength are set to the regression weightings described with respect to a known equation, data or spectral signature. Briefly, ICE 100 may be configured to perform the dot product of the input light beam into ICE 100 and a desired loaded regression vector represented by each layer 102, 104 for each wavelength. As a result, the output light intensity of ICE 100 is related to the characteristic or analyte of interest. Further details regarding how the exemplary ICE 100 is able to distinguish and process electromagnetic radiation related to the characteristic or analyte of interest are described in United States Patent numbers 6,198,531; 6,529,276; and 7,920,258, previously incorporated herein by reference.

[0047] Referring now to figure 4, illustrated is a block diagram illustrates how an optical computing device 200 is able to distinguish electromagnetic radiation related to a characteristic of a substance from other electromagnetic radiation. As shown in figure 4, after being illuminated with incident electromagnetic radiation, a fluid 202 containing a characteristic of interest or a substance produces an output of electromagnetic radiation (e.g., sample -interacted light), some of which is electromagnetic radiation 204 corresponding to the characteristic of interest and some of which is background electromagnetic radiation 206 corresponding to other components or characteristics of the fluid 202.

[0048] Although not specifically shown, one or more spectral elements may be employed in the device 200 in order to restrict the optical wavelengths and/or bandwidths of the system and thereby eliminate unwanted electromagnetic radiation existing in wavelength regions that have no importance. Such spectral elements can be located anywhere along the optical train, but are typically employed directly after the light source, which provides the initial electromagnetic radiation. Various configurations and applications of spectral elements in optical computing devices may be found in commonly owned United States Patent numbers 6,198,531; 6,529,276; 7,123,844; 7,834,999; 7,911,605; 7,920,258 and 8,049,881; United States Application Publication numbers 2009/0219538 and 2009/0219539; and United States Patent Application number 13/456,467, previously incorporated herein by reference.

[0049] The beams of electromagnetic radiation 204, 206 impinge upon the optical computing device 200, which contains an exemplary ICE 208 therein. In the illustrated embodiment, ICE 208 may be configured to produce optically interacted light, for example, transmitted optically interacted light 210 and reflected optically interacted light 214. In operation, ICE 208 may be configured to distinguish the electromagnetic radiation 204 from the background electromagnetic radiation 206. The transmitted optically interacted light 210, which may be related to the characteristic or analyte of interest of the fluid 202, may be conveyed to a detector 212 for analysis and quantification. In some embodiments, the detector 212 is configured to produce an output signal in the form of a voltage that corresponds to the particular characteristic of the fluid 202. In at least one embodiment, the signal produced by the detector 212 and the concentration of the characteristic of the fluid 202 may be directly proportional. In other embodiments, the relationship may be a polynomial function, an exponential function and/or a logarithmic function. The reflected optically interacted light 214, which may be related to the characteristic and other components of the fluid 202, can be directed away from detector 212. In alternative configurations, ICE 208 may be configured such that the refiected optically interacted light 214 can be related to the analyte of interest and the transmitted optically interacted light 210 can be related to other components of the fluid 202.

[0050] In some embodiments, a second detector 216 can be present and arranged to detect the refiected optically interacted light 214. In other embodiments, the second detector 216 may be arranged to detect the electromagnetic radiation 204, 206 derived from the fluid 202 or electromagnetic radiation directed toward or before the fluid 202. Without limitation, the second detector 216 may be used to detect radiating deviations stemming from an electromagnetic radiation source (not shown), which provides the electromagnetic radiation to the device 200. For example, radiating deviations can include such things as, but not limited to, intensity fluctuations in the electromagnetic radiation, interferent fluctuations (e.g., dust or other interferents passing in front of the electromagnetic radiation source), coatings on windows included with the optical computing device 200, combinations thereof or the like. In some embodiments, a beam splitter (not shown) can be employed to split the electromagnetic radiation 204, 206, and the transmitted or reflected electromagnetic radiation can then be directed to one or more ICE 208. That is, in such embodiments, ICE 208 does not function as a type of beam splitter, as depicted in figure 4, and the transmitted or reflected electromagnetic radiation simply passes through ICE 208, being computationally processed therein, before travelling to the detector 212.

[0051] The characteristic(s) of the fluid 202 being analyzed using the optical computing device 200 can be further processed computationally to provide additional characterization information about the fluid 202. In some embodiments, the identification and concentration of each analyte in the fluid 202 can be used to predict certain physical characteristics of the fluid 202. For example, the bulk characteristics of a fluid 202 can be estimated by using a combination of the properties conferred to the fluid 202 by each analyte. In some embodiments, the concentration of each analyte or the magnitude of each characteristic determined using optical computing device 200 could be fed into an algorithm operating under computer control. The algorithm may be configured to make predictions on how the characteristics of the fluid 202 change if the concentrations of the analytes are changed relative to one another. In some embodiments, the algorithm can produce an output that is readable by an operator who can manually take appropriate action, if needed, based upon the output. In some embodiments, the algorithm can take proactive process control by automatically adjusting flow parameters of a flow path, such as reducing fluid flow rate or pressure within the flow path, in order to manipulate the characteristics of the fluid.

[0052] The algorithm can be part of an artificial neural network configured to use the concentration of each detected analyte in order to evaluate the overall characteristic(s) of the fluid 202 and predict how to modify the fluid 202 or a fluid flow in order to alter the properties of the fluid or a related system in a desired way. Illustrative but non-limiting artificial neural networks are described in commonly owned United States Patent Application Publication number 2009/0182693, which is incorporated herein by reference. It is to be recognized that an artificial neural network can be trained using samples of substances having known concentrations, compositions and/or properties, and thereby generating a virtual library. As the virtual library available to the artificial neural network becomes larger, the neural network can become more capable of accurately predicting the characteristics of a substance having any number of analytes present therein. Furthermore, with sufficient training, the artificial neural network can more accurately predict the characteristics of the substance, even in the presence of unknown analytes.

[0053] It is recognized that the various embodiments herein directed to computer control and artificial neural networks, including various blocks, modules, elements, components, methods, and algorithms, can be implemented using computer hardware, software, combinations thereof, and the like. To illustrate this interchangeability of hardware and software, various illustrative blocks, modules, elements, components, methods and algorithms have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software will depend upon the particular application and any imposed design constraints. For at least this reason, it is to be recognized that one of ordinary skill in the art can implement the described functionality in a variety of ways for a particular application. Further, various components and blocks can be arranged in a different order or partitioned differently, for example, without departing from the scope of the embodiments expressly described.

[0054] Computer hardware used to implement the various illustrative blocks, modules, elements, components, methods, and algorithms described herein can include a processor configured to execute one or more sequences of instructions, programming stances, or code stored on a non-transitory, computer-readable medium. The processor can be, for example, a general purpose microprocessor, a microcontroller, a digital signal processor, an application specific integrated circuit, a field programmable gate array, a programmable logic device, a controller, a state machine, a gated logic, discrete hardware components, an artificial neural network, or any like suitable entity that can perform calculations or other manipulations of data. In some embodiments, computer hardware can further include elements such as, for example, a memory (e.g., random access memory (RAM), flash memory, read only memory (ROM), programmable read only memory (PROM), erasable read only memory (EPROM)), registers, hard disks, removable disks, CD-ROMS, DVDs, or any other like suitable storage device or medium.

[0055] Executable sequences described herein can be implemented with one or more sequences of code contained in a memory. In some embodiments, such code can be read into the memory from another machine -readable medium. Execution of the sequences of instructions contained in the memory can cause a processor to perform the process steps described herein. One or more processors in a multi-processing arrangement can also be employed to execute instruction sequences in the memory. In addition, hard-wired circuitry can be used in place of or in combination with software instructions to implement various embodiments described herein. Thus, the present embodiments are not limited to any specific combination of hardware and/or software.

[0056] As used herein, a machine-readable medium will refer to any medium that directly or indirectly provides instructions to a processor for execution. A machine-readable medium can take on many forms including, for example, non-volatile media, volatile media, and transmission media. Non-volatile media can include, for example, optical and magnetic disks. Volatile media can include, for example, dynamic memory. Transmission media can include, for example, coaxial cables, wire, fiber optics, and wires that form a bus. Common forms of machine-readable media can include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, other like magnetic media, CD-ROMs, DVDs, other like optical media, punch cards, paper tapes and like physical media with patterned holes, RAM, ROM, PROM, EPROM and flash EPROM.

[0057] Referring now to figure 5, an exemplary system for monitoring production fluid in a wellbore according to an embodiment of the present invention is depicted and generally designated 300. In the illustrated embodiment, fluid 302, represented by the arrows, is flowing within a flow path 304 depicted as a casing string 306 positioned in the wellbore having an electric submersible pump assembly 308 disposed therein. As will be appreciated, however, flow path 304 may be any other type of flow path, as generally described or otherwise defined herein including, but not limited to, the interior of a tubing string, the interior of a sensor assembly or the like. Electric submersible pump assembly 308 includes an electric submersible pump 310, an optical computing device 312, a signal processor 314 and a downhole control system 316. Optical computing device 312 may be somewhat similar to optical computing device 200 of figure 4, and therefore may be best understood with reference thereto. Optical computing device 312 may be useful in determining a particular characteristic of fluid 302 within flow path 304, such as determining the concentration of gas present within fluid 302. It should be noted that, while only one optical computing device is shown in figure 5, it will be appreciated that system 300 may employ any number of optical computing devices within flow path 304 or other flow paths, without departing from the scope of the disclosure.

[0058] As will be described in more detail below, optical computing device 312 may be configured to produce an output signal 318 in real-time or near real-time in the form of a voltage (or current) that corresponds to particular characteristic of interest in fluid 302. For example, optical computing device 312 may generate an output signal 318 that may be conveyed to or otherwise received by signal processor 314 that is communicably coupled to optical computing device 312. In real-time or near real-time, signal processor 314 may be configured to provide a resulting output signal 320 which may be conveyed to or otherwise received by downhole control system 316 that is communicably coupled to signal processor 314. The resulting output signal 320 may correspond to the concentration of gas present within fluid 302. In other embodiments, resulting output signal 320 may be indicative of characteristics such as density, specific gravity, pH, total dissolved solids, sand or particulates, combinations thereof and the like.

[0059] Downhole control system 316 may recognize that the resulting output signal 320 from signal processor 314 is within or without a predetermined or preprogrammed range of suitable operation for electric submersible pump 310. For example, output signal 318 may report that the gas concentration in fluid 302 is above or below a predetermined level. In such a case, downhole control system 316 may be configured to autonomously react to the resulting output signal 320 and provide a control signal 322 to electric submersible pump 310 to undertake the appropriate action such as changing an operational state of the electric motor including starting the motor, stopping the motor and changing the speed of the motor to increase or decrease the flow rate therethrough.

[0060] Referring now to figure 6 and with reference to figure 5, therein is illustrated is a schematic view of an exemplary optical computing device 400, which may represent a more detailed view of optical computing devices 312 of figure 5. As illustrated, optical computing device 400 is optically associated with flow path 304, such as the annular region between casing string 306 and the outer housing of electric submersible pump assembly 308, having fluid 302 flowing therethrough. Optical computing device 400 includes an electromagnetic radiation source 402 configured to emit or otherwise generate electromagnetic radiation 404. The electromagnetic radiation source 402 may be any device capable of emitting or generating electromagnetic radiation, as defined herein. For example, the electromagnetic radiation source 402 may be a light bulb, a light emitting device (LED), a laser, a blackbody, a photonic crystal, an X-Ray source, combinations thereof or the like.

[0061] In some embodiments, a lens 406 may be configured to collect or otherwise receive the electromagnetic radiation 404 and direct a beam 408 of electromagnetic radiation 404 toward fluid 302. Lens 406 may be any type of optical device configured to transmit or otherwise convey electromagnetic radiation 404 as desired. For example, lens 406 may be a normal lens, a Fresnel lens, a diffractive optical element, a holographic graphical element, a mirror (e.g., a focusing mirror), a type of collimator or any other electromagnetic radiation transmitting device known to those skilled in art. In other embodiments, lens 406 may be omitted from optical computing device 400 and electromagnetic radiation 404 may instead be directed toward fluid 302 directly from electromagnetic radiation source 402.

[0062] In one or more embodiments, optical computing device 400 may also include a sampling window 410 arranged adjacent to or otherwise in contact with fluid 302 for detection purposes. Sampling window 410 may be made from a variety of transparent, rigid or semi-rigid materials that are configured to allow transmission of electromagnetic radiation 404 therethrough. For example, sampling window 410 may be made of, but is not limited to, glasses, plastics, semi-conductors, crystalline materials, polycrystalline materials, hot or cold- pressed powders, combinations thereof, or the like. In order to remove ghosting or other common imaging issues that may result from reflectance on sampling window 410, optical computing device 400 may employ one or more internal reflectance elements (IRE), such as those described in co-owned United States Patent number 7,697,141, and/or one or more imaging systems, such as those described in co-owned United States Patent Application number 13/456,467, the contents of each hereby being incorporated by reference.

[0063] After passing through sampling window 410, electromagnetic radiation 404 impinges upon and optically interacts with fluid 302. As a result, optically interacted radiation 412 is generated by and reflected from fluid 302. Those skilled in the art, however, will readily recognize that alternative variations of optical computing device 400 may allow optically interacted radiation 412 to be generated by being transmitted, scattered, diffracted, absorbed, emitted, or re-radiated by and/or from fluid 302, without departing from the scope of the disclosure. Optically interacted radiation 412 generated by the optical interaction with fluid 302 may be directed to or otherwise be received by ICE 414 arranged within optical computing device 400. ICE 414 may be a spectral component substantially similar to ICE 100 described above with reference to figure 3. Accordingly, in operation ICE 414 may be configured to receive optically interacted radiation 412 and produce modified electromagnetic radiation 416 corresponding to a particular characteristic of interest of fluid 302. In particular, modified electromagnetic radiation 416 is electromagnetic radiation that has optically interacted with the ICE 414, whereby an approximate mimicking of the regression vector corresponding to the characteristic of interest in fluid 302 is obtained.

[0064] It should be noted that, while figure 6 depicts ICE 414 as receiving electromagnetic radiation as reflected from fluid 302, ICE 414 may be arranged at any point along the optical train of optical computing device 400, without departing from the scope of the disclosure. For example, in one or more embodiments, ICE 414 (as shown in dashed) may be arranged within the optical train prior to sampling window 410 and equally obtain substantially the same results. In other embodiments, sampling window 410 may serve a dual purpose as both a transmission window and ICE 414 (i.e., a spectral component). In yet other embodiments, ICE 414 may generate the modified electromagnetic radiation 416 through reflection, instead of transmission therethrough.

[0065] Moreover, while only one ICE 414 is shown in optical computing device 400, embodiments are contemplated wherein at least two ICE components may be used in optical computing device 400 and configured to cooperatively determine the characteristic of interest in fluid 302. For example, two or more ICE may be arranged in series or parallel within optical computing device 400 and configured to receive optically interacted radiation 412 and thereby enhance sensitivities and detector limits of optical computing device 400. In other embodiments, two or more ICE may be arranged on a movable assembly, such as a rotating disc or an oscillating linear array, which moves such that the individual ICE components are able to be exposed to or otherwise optically interact with electromagnetic radiation for a distinct brief period of time. The two or more ICE components in any of these embodiments may be configured to be either associated or disassociated with the characteristic of interest in fluid 302. In other embodiments, the two or more ICE may be configured to be positively or negatively correlated with the characteristic of interest in fluid 302. Additional discussion of these optional embodiments employing two or more ICE components can be found in co- pending United States Patent Application numbers 13/456,264, 13/456,405, 13/456,302 and 13/456,327, the contents of which are hereby incorporated by reference in their entireties.

[0066] In other embodiments, multiple optical computing devices can be placed at a single location along flow path 304 and each optical computing device may contain a unique ICE that is configured to detect a particular characteristic of interest in fluid 302. In such embodiments, a beam splitter can divert a portion of the electromagnetic radiation being reflected by, emitted from, or transmitted through fluid 302 and into each optical computing device. Each optical computing device, in turn, can be coupled to a corresponding detector or detector array that is configured to detect and analyze an output of electromagnetic radiation from the respective optical computing device. Parallel configurations of optical computing devices can be particularly beneficial for applications that require low power inputs and/or no moving parts.

[0067] Those skilled in the art will appreciate that any of the foregoing configurations can further be used in combination with a series configuration in any of the present embodiments. For example, two optical computing devices having a rotating disc with a plurality of ICE components arranged thereon can be placed in series for performing an analysis at a single location along the length of flow path 304. Likewise, multiple detection stations, each containing optical computing devices in parallel, can be placed in series for performing a similar analysis.

[0068] The modified electromagnetic radiation 416 generated by the ICE 414 may subsequently be conveyed to a detector 418 for quantification of the signal. Detector 418 may be any device capable of detecting electromagnetic radiation and may be generally characterized as an optical transducer. In some embodiments, detector 418 may be, but is not limited to, a thermal detector such as a thermopile or photoacoustic detector, a semiconductor detector, a piezo-electric detector, a charge coupled device (CCD) detector, a video or array detector, a split detector, a photon detector (such as a photomultiplier tube), photodiodes, combinations thereof, or the like, or other detectors known to those skilled in the art. Detector 418 may be configured to produce an output signal, such as output signal 318, as generally discussed above with reference to figure 5. Output signal 318 may be generated in real-time or near real-time and may be conveyed in the form of a voltage (or current) that corresponds to the particular characteristic of interest in fluid 302. The voltage returned by detector 418 is essentially the dot product of the optical interaction of optically interacted radiation 412 with respective ICE 414 as a function of the concentration of the characteristic of interest of fluid 302. As such, output signal 318 produced by detector 418 and the concentration of the characteristic of interest in fluid 302 may be directly proportional. In other embodiments, however, the relationship may correspond to a polynomial function, an exponential function, a logarithmic function and/or a combination thereof.

[0069] In some embodiments, optical computing device 400 may include a second detector 422, which may be similar to the first detector 418 in that it may be any device capable of detecting electromagnetic radiation. Similar to the second detector 216 of figure 4, second detector 422 of figure 6 may be used to detect radiating deviations stemming from electromagnetic radiation source 402. Undesirable radiating deviations can occur in the intensity of electromagnetic radiation 404 due to a wide variety of reasons and potentially causing various negative effects on optical computing device 400. These negative effects can be particularly detrimental for measurements taken over a period of time. In some embodiments, radiating deviations can occur as a result of a build-up of film or material on sampling window 410, which has the effect of reducing the amount and quality of light ultimately reaching the first detector 418. Without proper compensation, such radiating deviations could result in false readings and output signal 318 would no longer be primarily or accurately related to the characteristic of interest.

[0070] To compensate for these types of undesirable effects, second detector 422 may be configured to generate a compensating signal 424 generally indicative of the radiating deviations of electromagnetic radiation source 402, and thereby normalize output signal 318 generated by the first detector 418. As illustrated, second detector 422 may be configured to receive a portion of optically interacted radiation 412 via a beam splitter 426 in order to detect the radiating deviations. In other embodiments, however, second detector 422 may be arranged to receive electromagnetic radiation from any portion of the optical train in optical computing device 400 in order to detect the radiating deviations, without departing from the scope of the disclosure.

[0071] In some applications, output signal 318 and compensating signal 424 may be conveyed to (either jointly or separately) or otherwise received by a signal processor 314. Signal processor 314 may be configured to computationally combine compensating signal 424 with output signal 318 in order to normalize output signal 318 in view of any radiating deviations detected by the second detector 422. In some embodiments, computationally combining the output and compensating signals may entail computing a ratio of the two signals. For example, the concentration or magnitude of each characteristic determined using optical computing device 400 could be fed into an algorithm run by signal processor 314. The algorithm may be configured to make predictions on how the characteristics of fluid 302 change if the concentrations of the analytes are changed relative to one another. Signal processor 314 may be configured to generated resulting output signal 320 corresponding to the concentration of the characteristic of interest in fluid 302.

[0072] Referring now to figure 7 and with continued reference to figures 5 and 6, therein is illustrated is a schematic view of an exemplary optical computing device 500, which may represent a more detailed view of optical computing devices 312 of figure 5, albeit an alternative to the optical computing device 400. Accordingly, optical computing device 500 may be similar in some respects to optical computing device 400 of figure 6, and therefore may be best understood with reference thereto where like numerals will indicate like elements that will not be described again. Optical computing device 500 may again be configured to determine the concentration of a characteristic of interest in fluid 302 as contained within flow path 304. Unlike optical computing device 400 in figure 6, however, optical computing device 500 in figure 7 is configured to transmit the electromagnetic radiation through fluid 302 via a first sampling window 502a and a second sampling window 502b. The first and second sampling windows 502a,b may be similar to the sampling window 410 described above in figure 6. In this embodiment, flow path 304 may direct the flow of fluid 302 through an interior portion of electric submersible pump assembly 308 such as within sensor assembly 20 in figure 1.

[0073] As electromagnetic radiation 404 passes through fluid 302 via the first and second sampling windows 502a,b, it optically interacts with fluid 302. Optically interacted radiation 412 is subsequently directed to or otherwise received by ICE 414 as arranged within optical computing device 500. It is again noted that, while figure 7 depicts ICE 414 as receiving optically interacted radiation 412 as transmitted through sampling windows 502a,b, ICE 414 may equally be arranged at any point along the optical train of optical computing device 500, without departing from the scope of the disclosure. For example, in one or more embodiments, ICE 414 may be arranged within the optical train prior to the first sampling window 502a and equally obtain substantially the same results. In other embodiments, one or each of the first or second sampling windows 502a,b may serve a dual purpose as both a transmission window and ICE 414 (i.e., a spectral component). In yet other embodiments, ICE 414 may generate modified electromagnetic radiation 416 through reflection, instead of transmission therethrough. Moreover, as with the system 300 of figure 5, embodiments are contemplated herein which include the use of at least two ICE components in optical computing device 500 configured to cooperatively determine the characteristic of interest in fluid 302. [0074] Modified electromagnetic radiation 416 generated by ICE 414 is subsequently conveyed to detector 418 for quantification of the signal and generation of an output signal 318, which corresponds to the particular characteristic of interest in fluid 302. Optical computing device 500 may also include the second detector 422 for detecting radiating deviations stemming from electromagnetic radiation source 402. As illustrated, the second detector 422 may be configured to receive a portion of optically interacted radiation 412 via the beam splitter 426 in order to detect the radiating deviations. In other embodiments, however, the second detector 422 may be arranged to receive electromagnetic radiation from any portion of the optical train in optical computing device 500 in order to detect the radiating deviations, without departing from the scope of the disclosure. Output signal 318 and compensating signal 424 may then be conveyed to (either jointly or separately) or otherwise be received by signal processor 314 which may computationally combine the two signals and provide in real-time or near real-time resulting output signal 320 corresponding to the concentration of the characteristic of interest in fluid 302.

[0075] While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.