Inspection of monoethylene glycol (MEG) tanks using multi-spectral imaging

Abstract

A method includes: positioning a near-Infrared (NIR) and / or short wave Infrared (SWIR) camera into a tank holding a degraded monoethylene glycol (MEG) mixture such that a detector of the camera is below a surface of the degraded MEG mixture in the tank; transmitting electromagnetic signals in a NIR regime and / or SWIR regime through the degraded MEG mixture in the tank; detecting NIR and / or SWIR electromagnetic signals reflected from a surface of the tank at the detector of the camera; and processing an output of the camera to inspect the surface of the tank.

Description

INSPECTION OF MONOETHYLENE GLYCOL (MEG) TANKS USING MULTI- SPECTRAL IMAGINGFIELD OF THE INVENTION

[0001] The present disclosure is directed generally to tank inspection and, more particularly, to techniques for inspecting tanks containing degraded monoethylene glycol (MEG) mixtures using multi-spectral imaging.BACKGROUND

[0002] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0003] In oil and / or gas operations, monoethylene glycol (MEG) and / or MEG mixtures can be injected into and circulated through flowlines to prevent or manage hydrate formation within the production flowline. To support MEG injection operations, systems typically include one or more tanks to hold the MEG prior to circulation and / or after water has been removed (this MEG is often referred to as “lean MEG”) and one or more tanks to hold the MEG after it is retrieved from the production flowline and has picked up water (this MEG is often referred to as “rich MEG”). At the time MEG or a MEG mixture is initially injected into a flowline, the mixture may be relatively clear. However, once the MEG mixture has been circulated through the flowline for a period, the MEG begins to degrade. Degraded MEG mixtures (whether rich or lean) generally include amounts of water, dissolved salts, and / or other suspended solids that can make the degraded MEG mixture appear cloudy. In addition, degraded MEG mixtures may be relatively dark (e.g., dark brown) in color compared to water. As such, the visibility through degraded MEG mixtures is limited.

[0004] MEG tanks must undergo inspection periodically throughout their use. Typically, inspection of MEG tanks involves visual inspection of inside surfaces of the tank (e.g., to evaluate coating health and / or corrosion or defects on tank walls). If there exists a concern of fatigue and cracks, the visual inspection may also involve looking for cracks in the tanksurfaces. However, due to the optical properties of degraded MEG mixtures in the visual range (e.g., cloudiness and darker color), conventional remote visual inspection techniques cannot be used. Instead, the MEG tanks are emptied and then visually inspected, resulting in process interruptions and scheduling issues.

[0005] It is now recognized that a need exists for systems and methods for inspecting tanks holding degraded MEG mixtures without requiring the degraded MEG mixtures to be drained from the tanks.SUMMARY

[0006] A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0007] In accordance with aspects of the disclosure, a method includes: positioning a nearInfrared (NIR) and / or short wave Infrared (SWIR) camera into a tank holding a degraded monoethylene glycol (MEG) mixture such that a detector of the camera is below a surface of the degraded MEG mixture in the tank; transmitting electromagnetic signals in a NIR regime and / or SWIR regime through the degraded MEG mixture in the tank; detecting NIR and / or SWIR electromagnetic signals reflected from a surface of the tank at the detector of the camera; and processing an output of the camera to inspect the surface of the tank.

[0008] In accordance with other aspects of the disclosure, a monoethylene glycol (MEG) tank inspection system includes: a support structure including at least a first portion at one end configured to be manipulated from a location outside a tank of degraded MEG mixture; a nearInfrared (NIR) and / or short wave Infrared (SWIR) camera disposed proximate a distal end of the support structure, the camera and the distal end of the support structure configured to be submerged into the degraded MEG mixture inside the tank; and a NIR and / or SWIR transmitter configured to transmit electromagnetic signals in a NIR regime and / or SWIR regime into the degraded MEG mixture inside the tank.

[0009] In accordance with other aspects of the disclosure, a monoethylene glycol (MEG) tank inspection system includes: a remote operated vehicle (ROV) or autonomous underwater vehicle (AUV) configured to be positioned into a tank of degraded MEG mixture and movedthrough the degraded MEG mixture inside the tank; a near-infrared (NIR) and / or short wave Infrared (SWIR) camera integrated with the ROV, the camera configured to be submerged into the degraded MEG mixture inside the tank; and a NIR and / or SWIR transmitter configured to transmit electromagnetic signals in a NIR regime and / or SWIR regime into the degraded MEG mixture inside the tank.BRIEF DESCRIPTION OF DRAWINGS

[0010] The drawings illustrate only example embodiments and are therefore not to be considered limiting in scope, as the example embodiments may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the example embodiments. Additionally, certain dimensions or positions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements.

[0011] FIG. 1 is a schematic block diagram of equipment used to circulate monoethylene glycol (MEG) in a subsea oil and / or gas installation, in accordance with one or more aspects of the present disclosure.

[0012] FIG. 2 is a schematic diagram illustrating a near Infrared (NIR) and / or short wave Infrared (SWIR) camera mounted on a support structure used to position the camera in a tank of degraded MEG mixture, in accordance with one or more aspects of the present disclosure.

[0013] FIG. 3 is a schematic diagram illustrating a NIR and / or SWIR camera integrated into a remote operated vehicle (ROV) moving through a tank of degraded MEG mixture, in accordance with one or more aspects of the present disclosure.

[0014] FIG. 4 is a plot illustrating results of a spectroscopic scan performed on two samples of rich MEG, in accordance with one or more aspects of the present disclosure.

[0015] FIGS. 5A-5C are photographs of an experiment demonstrating the effectiveness of using multi-spectral imaging to view a surface through rich MEG, in accordance with one or more aspects of the present disclosure.

[0016] FIGS. 6A-6C are photographs of an experiment demonstrating the effectiveness of using multi-spectral imaging to view a surface through lean MEG, in accordance with one or more aspects of the present disclosure.

[0017] FIG. 7 is a process flow diagram illustrating a method for inspecting a tank containing rich MEG using multi-spectral imaging, in accordance with one or more aspects of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0018] The present disclosure is directed to systems and methods for inspecting a tank holding a degraded monoethylene glycol (MEG) mixture without removing the degraded MEG mixture from the tank. The inspection may be of one or more inside surfaces of the tank. The inspection systems and methods may utilize multi-spectral imaging, in particular at near-infrared (NIR) and / or short wave Infrared (SWIR) wavelengths to visualize the inside surface(s) of the tank without removing the degraded MEG mixture from the tank. The inspection may be performed on rich MEG tanks, lean MEG tanks, or tanks including any other degraded MEG mixtures therein. In the use of MEG for dehydration and hydrate prevention, the MEG is considered degraded when it breaks down into organic acids. As such, the MEG mixture is considered “degraded” when there is an observed increase in the concentration of organic acids in the MEG mixture. The breakdown of MEG into organic acids is believed to occur when the MEG of the MEG mixture contacts high temperature such as hot spots in the reboiler. In addition, some of the coloration of the MEG mixture may be due to iron content from the pipeline as well as other additives. The presence of organic acids, with or without other coloration impacts, can make it difficult to see through the degraded MEG mixture under visible light conditions.

[0019] In the following description, the terms “rich MEG” and “lean MEG” are used. The term “rich MEG” refers to a mixture including degraded MEG that has been extracted from a flow of production fluid and contains a certain amount of water therein. The rich MEG mixture also may comprise salts dissolved therein, and / or other suspended solids. The term “lean MEG” refers to: 1) a mixture including MEG that is initially supplied to a MEG circulation system prior to injection; 2) a mixture including degraded MEG resulting from rich MEG going through one or more regeneration processes prior to reinjection; or a combination thereof.

[0020] Based on an initial investigation into transmission efficiency of light at various wavelengths through a field sample of degraded MEG mixture (specifically, rich MEG), the inventor found that degraded MEG mixtures appear more transparent in the NIR regime and / or SWIR regime. As such, an inspection system such as a submersible camera or an inspection ROV or AUV operating in the NIR regime and / or SWIR regime may be used for inspecting tanks holding degraded MEG mixtures without the tank being drained. The camera operatingin the NIR regime and / or SWIR regime may be used to provide visual inspection of tank wall(s) and / or navigation (e.g., of an ROV / AUV). Similar inspection techniques may be used to inspect tanks holding other types of fluids that are transmissible to NIR and / or SWIR wavelengths.

[0021] Turning now to the drawings, FIG. 1 illustrates a subsea oil and / or gas installation 100 including equipment for circulating MEG through a production flowline 102. MEG is injected into a subsea flowline (e.g., production flowline 102) to prevent, inhibit, reduce, or otherwise mitigate hydrate formation in the flowline. When MEG is circulated through the production flowline 102, it adsorbs water from the produced hydrocarbon stream. Without the MEG, this water might otherwise freeze and form hydrates (ice-like solids) in the production flowline 102. The arrows in FIG. 1 represent the flow of MEG through the system.

[0022] The MEG circulation equipment may include, for example, one or more lean MEG tanks 104, an injection flowline 105 leading to an injection point 106, one or more separator units 108, one or more rich MEG tanks 110, and one or more MEG regeneration units 112. As illustrated, the lean MEG tank(s) 104, separator unit(s) 108, rich MEG tank(s) 110, and MEG regeneration unit(s) 112 may be located at a surface facility 114 located proximate / above a seawater surface 116. In other embodiments, one or more of these components may be located subsea or on land.

[0023] While FIG. 1 illustrates a rich MEG tank 110 being used in a subsea oil and / or gas installation 100, it should be noted that a similar MEG circulation process may be performed in land-based oil and / or gas installations to prevent, inhibit, reduce, or otherwise mitigate hydrate formation in a production flowline. As such, the MEG tank inspection systems and methods described below may be used for inspection of MEG tanks both onshore and offshore. In a land-based MEG circulation system, the MEG tanks may be relatively smaller than the tanks would be in an offshore MEG circulation system.

[0024] The MEG circulation process may proceed as follows. First, lean MEG may be injected into the production flowline 102 (e.g., at the injection point 106.) The injection point 106 is shown as being at a wellhead 118. However, the injection point 106 may be at any other desired location along the production flowline 102, as will be apparent to a person having ordinary skill in the art. Once in the flowline 102, the MEG mixes with and adsorbs water from the hydrocarbon stream. The MEG mixture flows with the produced fluid back to the surface facility 114. On the way, the MEG mixture / produced fluid may pass through one or more subsea facilities or equipment (e.g., pipeline end termination (PLET) or pipeline end manifold (PLEM)) 120 and up a riser 122 to the surface facility 114. The MEG mixture / produced fluidmay pass through any number and arrangement of equipment along the production flowline 102 from the injection point 106 to the surface facility 114, as will be understood by a person having ordinary skill in the art.

[0025] At the surface facility 114, the MEG mixture is recovered. The one or more separator units 108 may extract or otherwise separate out rich MEG from the produced fluids. The extracted rich MEG is then stored in one or more rich MEG tanks 110. As discussed above, the rich MEG stored in the tank(s) 110 has water entrained in it, making it more transparent than the lean MEG in tank(s) 104. The rich MEG stored in the tank(s) 110 may also have a cloudy appearance due to the presence of dissolved salts and / or other contaminants. The exact composition of the rich MEG may vary depending on the oil and / or gas application where it is used, the production process, the number of times the MEG has been recirculated through the production process, the amount of degradation of MEG, etc. The rich MEG is simply degraded MEG (with water and / or salts) that has been separated out from production fluids returned from the production flowline 102.

[0026] The rich MEG may be communicated from the rich MEG tank(s) 110 to one or more MEG regeneration unit(s) 112. The MEG regeneration unit(s) 112 may remove water (and possibly other contaminants) from the rich MEG through evaporation and / or other treatments. The MEG regeneration unit(s) 112 may output lean MEG to the lean MEG tank(s) 104. As such, the regeneration unit(s) 112 process the rich MEG from tank(s) 110 into lean MEG sent to tank(s) 104 for reuse in the production system. As the MEG cycles through this circulation system, the MEG degrades, causing the MEG mixtures (rich and lean MEG) to take on a darker, less transparent color.

[0027] For circulation in subsea installations (e.g., 100), a large volume of MEG is needed to reach from the surface facility down to the subsea reservoir and back. As such, the rich MEG tank(s) 110 and / or lean MEG tank(s) 104 may be sized to hold a relatively large volume of degraded MEG mixtures therein. Rich MEG tanks 110 and lean MEG tanks 104, like many tanks located offshore, have an inspection requirement to ensure the integrity of both the MEG tanks 110 / 104 and the overall surface facility 114. Due to the large size of the MEG tanks 110 / 104, previous methods of inspection involved bringing a vessel alongside, pumping the degraded MEG mixture out of the tank 110 / 104 into the vessel, and then having people enter the tank to perform the visual inspection. These previous methods of tank inspection are timeconsuming and costly. Inspection using conventional underwater cameras is also impractical because of the cloudiness of the degraded MEG mixture located in the tank.

[0028] The present disclosure addresses these drawbacks by providing systems and methods for inspecting a MEG tank 110 / 104 containing a degraded MEG mixture without emptying the tank. The present disclosure involves using cameras that operate in the NIR and / or SWIR range for visual inspection of the tank 110 / 104. FIGS. 2 and 3 illustrate two different types of MEG tank inspection systems that may be used with the tank(s) 110 / 104 described above. As illustrated in both FIGS. 2 and 3, the MEG tank 110 / 104 contains a degraded MEG mixture 208. The degraded MEG mixture 208 may be lean MEG. The degraded MEG mixture 208 may be rich MEG. The composition of the degraded MEG mixture 208 may be such that the concentration of MEG in the degraded MEG mixture 208 is between 5% and 90%. In some embodiments (e.g., with rich MEG), the degraded MEG mixture 208 may have a MEG concentration between 5% and 20%. In some embodiments (e.g., with lean MEG), the degraded MEG mixture 208 may have a MEG concentration between 70% and 90%. A portion of the degraded MEG mixture 208 may include MEG that has been circulated through a MEG circulation system (e.g., as shown in FIG. 1) for a certain period. The period or number of circulation cycles over which the MEG is degraded and / or replaced may depend on the fluid chemistry, the well(s), and / or how the equipment is operated.

[0029] FIG. 2 illustrates a MEG tank inspection system 200 including a NIR and / or SWIR camera 202 (referred to hereinafter as “camera”) coupled to a support structure 204. The support structure 204 is configured to be manipulated from a location outside of the MEG tank 110 / 104 being inspected. The support structure 204 includes at least a first portion 206 at one end configured to be manipulated from a location outside the tank 110 / 104 holding a degraded MEG mixture 208. The support structure 204 may remain stationary with respect to the attached camera 202 while allowing for manipulation of the camera 202 within the tank 110 / 104 via manipulation of the support structure 204 from a location outside the tank 110 / 104. For example, the support structure 204 may include a rod, as shown. As another example, the support structure 204 may include a mechanical arm with one or more bends. The support structure 204 may be manually moved with respect to the tank 110 / 104 to reposition the camera 202 within the tank 110 / 104. The support structure 204 may be automatically (e.g., robotically) moved with respect to the tank 110 / 104 to reposition the camera 202 within the tank 110 / 104. The support structure 204 may be movable with respect to the attached camera 202 in other embodiments. For example, the support structure 204 may be a movable mechanical arm that can be adjusted manually or automatically (e.g., robotically). The support structure 204 may be movable at one or more set pivot points (e.g., elbows) located along its length, or a largeportion of the support structure 204 may be flexible allowing for adding bends to the support structure 204.

[0030] As illustrated, the camera 202 may be disposed proximate a distal end 210 of the support structure 204. The camera 202 and the distal end 210 of the support structure are configured to be submerged into the degraded MEG mixture 208 inside the tank 110 / 104. The camera 202 includes a NIR and / or SWIR detector 212 (referred to hereinafter as “detector”) tuned for detection of electromagnetic signals in the NIR regime and / or the SWIR regime of the electromagnetic spectrum. The NIR regime may include electromagnetic signals at a wavelength between approximately 780 nm and approximately 1400 nm. The SWIR regime may include electromagnetic signals at a wavelength between approximately 1400 nm and approximately 3000 nm. The detector 212 of the camera 202 is configured to take measurements of electromagnetic signals in the NIR regime and / or the SWIR regime that are reflected from surfaces of the MEG tank 110 / 104 and output signals (e.g., image data) indicative of these measurements. The detector 212 may be a commercially available infrared or near-infrared receiver.

[0031] The system 200 also includes a NIR and / or SWIR transmitter 214 (referred to hereinafter as “transmitter”) configured to transmit electromagnetic signals in the NIR regime and / or the SWIR regime through the degraded MEG mixture 208 inside the tank 110. The transmitter 214 may be integrated with the camera 202 having the detector 212 and / or with the distal end 210 of the support structure 204. For example, as illustrated, the camera 202 includes both the transmitter 214 and detector 212 for transmitting and detecting, respectively, electromagnetic signals in the NIR regime. In other embodiments, the transmitter 214 may be a standalone component from both the camera 202 and the support structure 204.

[0032] Electromagnetic signals output from the transmitter 214 may travel through the degraded MEG mixture 208 in the tank 110 / 104 where they are reflected back from one or more surfaces 216 of the tank 110 / 104, and the detector 212 may detect the NIR and / or SWIR signals reflected from the surface(s) 216. The detector 212 may then output image data that are analyzed to inspect of the surfaces 216 of the tank 110 / 104 while the degraded MEG mixture 208 is in the tank 110 / 104.

[0033] The system 200 may further include at least one processor 218 coupled to at least one memory 220 and used to perform the analysis on measurements taken by the camera 202. For example, as illustrated, the system 200 may include an information handling system 222 that is separate from the camera 202, the information handling system 222 including the at least one processor 218 and at least one memory 220 located outside of the tank 110 / 104. The atleast one processor 218 may be communicatively coupled to the camera 202 via a wired or wireless connection. In other embodiments, at least one processor 218 and at least one memory 220 may be collocated with the camera 202, either onboard the camera 202 or proximate the camera 202 at the distal end of the support structure 204. In such embodiments, the at least one processor 218 may be communicatively coupled to at least the detector 212 of the camera 202. In still other embodiments, multiple processors 218 and / or memories 220 may be split between the camera 202 and a separate location outside the tank 110 / 104 and communicatively coupled to the camera 202.

[0034] Regardless of their locations, the at least one memory 220 contains instructions that, upon execution by the at least one processor 218, cause the at least one processor 218 to perform one or more steps of a method in accordance with the present disclosure. For example, the processor(s) 218 may: receive an output from the camera 202 (e.g., from the detector 212 of the camera 202) indicative of reflections of electromagnetic waves in the NIR regime and / or the SWIR regime from a surface 216 of the MEG tank 110 / 104; and inspect the surface 216 of the MEG tank 110 / 104 based on the output from the camera 202. The inspection may include processing images received from the camera 202 to detect a location of a potential defect, crack, corrosion, or other change in structure of the surface 216 of the tank 110 / 104. In some embodiments, the processor(s) 218 may be coupled to a visual display configured to display images of the tank surface 216 to a user.

[0035] The MEG tank 110 / 104 shown in FIG. 2 may be a relatively smaller MEG tank 110 / 104. Such smaller MEG tanks 110 / 104 may be more commonly used in land-based oil and / or gas installations. The support structure 204 may provide a relatively low cost way to move the camera 202 through the smaller MEG tank 110 / 104 to capture images of the entire inside surface area of the tank 110 / 104 during the tank inspection. Other embodiments may use other types of equipment to move a camera through a MEG tank for inspection purposes.

[0036] FIG. 3 illustrates a MEG tank inspection system 300 including a remote operated vehicle (ROV) 302 with a NIR and / or SWIR camera 304 (referred to hereinafter as “camera”). The ROV 302 is configured to be positioned into a tank 110 / 104 of degraded MEG mixture 306 and to move through the degraded MEG mixture 306 inside the tank 110 / 104. The ROV 302 may be remotely controlled from outside the tank 110 / 104 being inspected. The camera 304 is integrated with the ROV 302 and configured to be submerged into the degraded MEG mixture 306 inside the tank 110 / 104.

[0037] The ROV 302 may include a propulsion system for moving the ROV 302 through the tank 110 / 104. In some embodiments, the ROV 302 may include an onboard navigation systemto assist in controlling the propulsion system to move the ROV 302 through the tank 110 / 104 without impacting any surfaces 308 of the tank 110 / 104. The ROV 302 may receive operating power through a cable 309 to power the propulsion system and other onboard equipment of the ROV 302 (e.g., including the camera 304).

[0038] The camera 304 includes a NIR and / or SWIR detector 310 (referred to hereinafter as “detector”) tuned for detection of electromagnetic signals in the NIR regime and / or the SWIR regime of the electromagnetic spectrum. The NIR regime may include electromagnetic signals at a wavelength between approximately 780 nm and approximately 1400 nm. The SWIR regime may include electromagnetic signals at a wavelength between approximately 1400 nm and approximately 3000 nm. The detector 310 of the camera 304 is configured to take measurements of electromagnetic signals in the NIR regime and / or the SWIR regime that are reflected from surfaces 308 of the MEG tank 110 / 104 and output signals (e.g., image data) indicative of these measurements. The detector 310 may be a commercially available infrared or near-infrared receiver.

[0039] The system 300 also includes a NIR and / or SWIR transmitter 312 (referred to hereinafter as “transmitter”) configured to transmit electromagnetic signals in the NIR regime and / or the SWIR regime through the degraded MEG mixture 306 inside the tank 110 / 104. The transmitter 312 may be integrated with the camera 304 having the detector 310 and / or at another location of the ROV 302. In other embodiments, the transmitter 312 may be separate from the ROV 302 (e.g., the transmitter may be integrated with a separate ROV).

[0040] Electromagnetic signals output from the transmitter 312 may travel through the degraded MEG mixture 306 in the tank 110 / 104 where they are reflected back from one or more surfaces 308 of the tank 110 / 104, and the detector 310 may detect the NIR and / or SWIR signals reflected from the surface(s) 308. The detector 310 may then output signals that are analyzed to inspect of the surfaces 308 of the rich MEG tank 110 while the degraded MEG mixture 306 is in the tank 110 / 104.

[0041] The system 300 may further include at least one processor 314 coupled to at least one memory 316 and used to perform the analysis on measurements taken by the camera 304. For example, as illustrated, the system 300 may include an information handling system 318 that is separate from the ROV 302, the information handling system 318 including the at least one processor 314 and at least one memory 316 located outside of the tank 110 / 104. The at least one processor 314 may be communicatively coupled to the camera 304 in the ROV 302 via a wired (e.g., through cable 309) or wireless connection. In other embodiments, at least one processor 314 and at least one memory 316 may be onboard the ROV 302. In suchembodiments, the at least one processor 314 may be communicatively coupled to at least the detector 310 of the camera 304. In still other embodiments, multiple processors 314 and / or memories 316 may be split between the ROV 302 and a separate location outside the tank 110 / 104 that is communicatively coupled to the camera 304 of the ROV 302.

[0042] Regardless of their locations, the at least one memory 318 contains instructions that, upon execution by the at least one processor 316, cause the at least one processor 316 to perform one or more steps of a method in accordance with the present disclosure. For example, the processor(s) 316 may: receive an output from the camera 304 (e.g., from the detector 310 of the camera 304) indicative of reflections of electromagnetic waves in the NIR regime and / or the SWIR regime from a surface 308 of the MEG tank 110 / 104; and inspect the surface 308 of the MEG tank 110 / 104 based on the output from the camera 304. The inspection may include processing images received from the camera 304 to detect a location of a potential defect, crack, corrosion, or other change in structure of the surface 308 of the tank 110 / 104. In some embodiments, the processor(s) 314 may be coupled to a visual display configured to display images of the tank surface 308 to a user. The visual display of images taken by the onboard camera 304 of the ROV 302 may also be used to assist in the navigation of the ROV 302 through the tank 110 / 104, particularly if the inside of the tank 110 / 104 has a complex geometry.

[0043] In addition to tank inspection, the processor(s) 316 may process image data provided by the camera 304 to provide navigational assistance to the ROV 302 being moved through the tank 110 / 104. For example, a control system (onboard and / or separate from the ROV 302) may output control signals to the propulsion system of the ROV 302 in response to determining that the ROV 302 is in close proximity to a wall 308 of the tank 110 / 104 based on the image data received from the camera 304.

[0044] The MEG tank 110 / 104 shown in FIG. 3 may be a relatively larger MEG tank 110 / 104 (e.g., having a volume between approximately 1700 m3and 7500 m3). Such larger MEG tanks 110 / 104 may be more commonly used in offshore oil and / or gas installations. The ROV 302 may be dropped into the larger MEG tank 110 / 104 where it can be steered, either through an automated navigation system or remotely by an operator, to capture images of the entire inside surface area of the tank 110 / 104 during the tank inspection. An ROV-based system may also be beneficial for larger tanks 110 / 104 having internal baffles or other complex shapes to direct the flow of the degraded MEG mixture therein. Although described as being an ROV-based system, other embodiments of the present disclosure may use other types of self-navigating equipment (e.g., an automated underwater vehicle (AUV)) to move a NIR and / or SWIR camera through a MEG tank for inspection purposes. All the description provided with relation to FIG.3 is applicable to use of an AUV rather than an ROV, without departing from the scope of the present disclosure.

[0045] FIGS. 4-5C show experimental results that demonstrate the effectiveness of NIR and / or SWIR spectroscopy for capturing images through a degraded MEG mixture for the inspection of MEG tanks.

[0046] FIG. 4 is a plot 400 showing measurements of transmissibility of different wavelengths of electromagnetic signals through two samples of rich MEG taken from the field. The two samples of rich MEG were taken from the rich MEG tank on the same offshore platform for transmissibility testing. The results as seen in the plot 400 show steady improvements in the transmissibility of the rich MEG as wavelength increases from the visual regime into the NIR and SWIR regime of the electromagnetic spectrum. While rich MEG can often appear opaque to the naked eye, the fluid has an improved transmissibility in the NIR regime and / or the SWIR regime. The plot 400 shows a spike in transmissibility around 960 nm for both samples. Because of this spike in transmissibility within the NIR range of the electromagnetic spectrum, it is believed that an NIR camera will be able to take clear images when submerged in degraded MEG mixtures (such as rich MEG). As such, the initial testing supports the concept of using an NIR camera for MEG tank inspections. Similar improvements may be realized using a SWIR camera as well.

[0047] FIGS. 5A-5C are photographs showing additional experimental results indicating the suitability for NIR cameras to perform inspections of tanks filled with a degraded MEG mixture. FIG. 5 A shows the initial test setup, including a sample of rich MEG within a beaker with a glass cover plate. The imaging target in the test is a napkin with lines drawn on it located below the beaker. Lighting is provided from a fume hood above the setup, and a black Infrared (IR) light emitting diode (LED) source is positioned next to the beaker.

[0048] FIG. 5B illustrates a photograph of the imaging target (napkin with lines drawn on it) underneath the beaker with the rich MEG sample. This first photograph was taken using a cellular phone-based camera with lighting provided by the overhead light of the fume hood. As such, the camera detected electromagnetic reflections in the visible light range of wavelengths (e.g., 380 nm to 700 nm).

[0049] FIG. 5C illustrates a NIR photograph of the imaging target underneath the beaker with the rich MEG sample. This second photograph was taken using a DSLR camera converted to detect signals in the NIR regime with the IR LED light source turned on. As such, the camera used detection of electromagnetic reflections in the NIR range of wavelengths (e.g., 780 nm to 1400 nm).

[0050] Comparing the photographs of FIGS. 5B and 5C, the lines drawn on the napkin are clearer in the NIR photograph (5C) than the visible light photograph (5B). In addition, the texture of the napkin can be clearly seen in the NIR photograph (5C) but not in the visible light photograph (5B). As such, the photographs show there is improvement in the visibility going from the visible range of wavelengths to NIR range of wavelengths. Both the optical spectra testing of FIG. 4 and the photographic testing of FIGS. 5A-5C support the concept that degraded MEG mixtures exhibit enough optical clarity in the NIR range to use modified NIR submersible cameras and NIR equipped RO Vs for inspection of MEG tanks. Similar improvements may be realized using a SWIR camera as well.

[0051] FIGS. 6A-6C are photographs showing additional experimental results indicating the suitability for NIR cameras to perform inspections of tanks filled with a degraded MEG mixture. FIG. 6A shows the initial test setup, including a sample of lean MEG within a tank with a transparent plate at one end. The lean MEG is a degraded MEG mixture having an 82% concentration of MEG. As illustrated, the lean MEG is a dark brownish color, indicative of the degradation of the MEG in the MEG mixture. The imaging target in the test is a 1951 USAF resolution test chart placed inside the tank. Photographs of the imaging target were taken using a camera at various positions 100 mm to 920 mm from the imaging target illuminated by various wavelengths of light (e.g., white light and NIR wavelengths).

[0052] FIG. 6B illustrates a photograph of the imaging target inside the tank with the lean MEG sample as viewed from 300 mm. This first photograph was taken using a camera with lighting provided by a white LED light source. As such, the camera detected electromagnetic reflections in the visible light range of wavelengths.

[0053] FIG. 6C illustrates a NIR photograph of the imaging target inside the tank with the lean MEG sample as viewed from 300 mm. This second photograph was taken using a camera with lighting provided by a NIR LED light source. As such, the camera detected electromagnetic reflections in the NIR range of wavelengths.

[0054] Comparing the photographs of FIGS. 6B and 6C, the markings on the imaging target are clearer in the NIR photograph (6C) than the visible light photograph (6B). As such, the photographs show there is improvement in the visibility going from the visible range of wavelengths to NIR range of wavelengths. The photographic testing of FIGS. 6A-6C further supports the concept that degraded MEG mixtures exhibit enough optical clarity in the NIR range to use modified NIR submersible cameras and NIR equipped RO Vs for inspection of MEG tanks. Similar improvements may be realized using a SWIR camera as well.

[0055] FIG. 7 illustrates a process flow diagram of a method 700 for inspecting a tank containing a degraded MEG mixture using multi-spectral imaging (particularly in the NIR and / or SWIR wavelength range). It should be noted that the method 700 shown in FIG. 7 is merely an example and other embodiments may include additional steps not shown, have one or more illustrated steps removed, or have certain illustrated steps performed in different orders than shown, without departing from the scope of the present disclosure.

[0056] At block 702, the method 700 includes positioning a NIR and / or SWIR camera (referred to hereinafter as “camera”) into a tank holding a degraded MEG mixture (e.g., rich MEG, lean MEG, etc.) such that a detector of the camera is below a surface of the degraded MEG mixture in the tank. In some embodiments, this may involve positioning an ROV or AUV in the tank, with the camera integrated with the ROV or AUV. In other embodiments, this may involve positioning a support structure from a location outside of the tank such that a distal end of the support structure is located under the surface of the degraded MEG mixture in the tank, with the camera disposed proximate the distal end of the support structure.

[0057] At block 704, the method 700 includes transmitting electromagnetic signals in a NIR regime and / or SWIR regime through the degraded MEG mixture in the tank. At block 706, the method 700 includes detecting NIR and / or SWIR electromagnetic signals reflected from a surface of the tank at the detector of the camera. At block 708, the method 700 includes processing an output of the camera to inspect the surface of the tank. In some embodiments, this may include processing images received from the camera to detect a location of a potential defect, crack, or corrosion of the surface of the tank. In some embodiments, the method 700 may include displaying images of the surface of the tank on a visual display based on the output of the camera.

[0058] It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of example embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

CLAIMSWhat is claimed is:

1. A method, comprising: positioning a near-infrared (NIR) and / or short wave Infrared (SWIR) camera into a tank holding a degraded monoethylene glycol (MEG) mixture such that a detector of the camera is below a surface of the degraded MEG mixture in the tank; transmitting electromagnetic signals in a NIR regime and / or SWIR regime through the degraded MEG mixture in the tank; detecting NIR and / or SWIR electromagnetic signals reflected from a surface of the tank at the detector of the camera; and processing an output of the camera to inspect the surface of the tank.

2. The method of claim 1, wherein positioning the camera into the tank comprises positioning a remote operated vehicle (ROV) or autonomous underwater vehicle (AUV) in the tank, wherein the camera is integrated with the ROV or AUV.

3. The method of claim 2, further comprising navigating the ROV or AUV through the tank based at least in part on the output of the camera.

4. The method of claim 1, wherein positioning the camera into the tank comprises positioning a support structure from a location outside of the tank such that a distal end of the support structure is located under the surface of the degraded MEG mixture in the tank, wherein the camera is disposed proximate the distal end of the support structure.

5. The method of claim 4, wherein the support structure includes a mechanical arm with one or more bends.

6. The method of claim 4, wherein positioning the camera into the tank comprises automatically moving the support structure.

7. The method of claim 1, wherein the degraded MEG mixture is rich MEG.

8. The method of claim 1, wherein the degraded MEG mixture is lean MEG.

9. The method of claim 1, wherein a concentration of MEG in the degraded MEG mixture is between 5% and 90%.

10. The method of claim 1, wherein processing the output of the camera to inspect the surface of the tank comprises processing images received from the camera to detect a location of a potential defect, crack, or corrosion of the surface of the tank.

11. The method of claim 1, further comprising displaying images of the surface of the tank on a visual display based on the output of the camera.

12. A monoethylene glycol (MEG) tank inspection system, comprising: a support structure comprising at least a first portion at one end configured to be manipulated from a location outside a tank of degraded MEG mixture; a near-infrared (NIR) and / or short wave Infrared (SWIR) camera disposed proximate a distal end of the support structure, the camera and the distal end of the support structure configured to be submerged into the degraded MEG mixture inside the tank; and a NIR and / or SWIR transmitter configured to transmit electromagnetic signals in a NIR regime and / or SWIR regime into the degraded MEG mixture inside the tank.

13. The system of claim 12, further comprising at least one processor communicatively coupled to the camera and at least one memory containing instructions that, upon execution by the processor, cause the processor to: receive an output from the camera indicative of reflections of electromagnetic waves in the NIR regime and / or SWIR regime from a surface of the tank; and inspect the surface of the tank based on the output from the camera.

14. The system of claim 12, wherein the transmitter is integrated with the camera and / or the distal end of the support structure.

15. The system of claim 12, wherein the transmitter is a standalone component from the camera and the support structure.

16. A monoethylene glycol (MEG) tank inspection system, comprising: a remote operated vehicle (ROV) or autonomous underwater vehicle (AUV) configured to be positioned into a tank of degraded MEG mixture and moved through the degraded MEG mixture inside the tank; a near-infrared (NIR) and / or short wave Infrared (SWIR) camera integrated with the ROV or AUV, the camera configured to be submerged into the degraded MEG mixture inside the tank; and a NIR and / or SWIR transmitter configured to transmit electromagnetic signals in a NIR regime and / or SWIR regime into the degraded MEG mixture inside the tank.

17. The system of claim 16, further comprising at least one processor communicatively coupled to the camera and at least one memory containing instructions that, upon execution by the processor, cause the processor to: receive an output from the camera indicative of reflections of electromagnetic waves in the NIR regime and / or SWIR regime from a surface of the tank; and inspect the surface of the tank based on the output from the camera.

18. The system of claim 16, wherein the transmitter is integrated with the ROV or AUV.

19. The system of claim 16, wherein the transmitter is separate from the ROV or AUV.

20. The system of claim 16, further comprising a control system coupled to a propulsion system of the ROV or AUV, wherein the control system is configured to output control signals to the propulsion system based on the output from the camera.

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