Abstract:
A system for detecting leaks from a subsea system is disclosed which includes at least one subsea structure anchored to a sea floor, a fluorescence detector attached to the subsea structure, the fluorescence detector adapted to generate a light beam having a wavelength that will fluoresce material leaking from the subsea system when the material is irradiated with the light beam, and a camera adapted to observe the fluorescence of the material as it is being irradiated by the light source.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is generally directed to the field of detecting leaks from underwater systems, and, more particularly, to a fluorescence measurement system for detecting leaks from subsea systems and structures. 
         [0003]    2. Description of the Related Art 
         [0004]    There are many existing subsea production systems and structures that are employed in the production of oil and gas from subsea wells. Due to environmental, regulatory and perhaps safety regulations, it is important to be able to readily detect the leakage of undesirable materials from such subsea structures. For example, the detection of leaks of hydrocarbons or hydraulic fluid and/or other chemicals from such underwater systems is very important as it enhances the environmental and operational efficiency of such subsea systems, e.g., subsea hydrocarbon production facilities. 
         [0005]    Many techniques have been employed to attempt to detect undesirable leakage of material from such subsea systems. For example, it is known in the prior art to employ acoustic, fluorescence, temperature and gas based measurement systems to detect such leakage. In most cases, such leak detection systems were non-permanent in nature in that they were used during periodic survey operations. In some cases, however, such systems were permanently positioned subsea adjacent the subsea system being monitored. 
         [0006]    The majority of underwater fluorescence, temperature and gas sensors used for leak detection have a very small or limited field of sensing capability. That is, they are essentially point sensors. In the case of temperature and gas sensors, such devices are typically only capable of making measurements at the actual sensing device. Fluorescence sensors have slightly greater range than temperature or gas sensors, but it is still very limited. For example,  FIG. 1  is a schematic depiction of a prior art fluorescence point sensor device  10  with a very small sensing field depicted by the circle  12 , e.g., approximately 2 cm. Thus, such fluorescence based systems typically only sense a very small volume of water. 
         [0007]    The point sensing nature of prior art fluorescence, temperature and gas based sensors can be detrimental to the detection of leaking materials. For example, employing leak detection sensors with such a limited range means that, in order to be detected, the plume of leaking material has to actually reach such sensors before it can be detected. This means that a very large number of permanent sensors of this nature would need to be employed to effectively monitor an underwater production system. Obviously, deploying a large number of permanent point-type sensors to effectively monitor a subsea facility would be very expensive and poses a number of practical problems relating to the deployment of such sensors, as well as providing power and data communication with such sensors. 
         [0008]    On the other hand, acoustic based leak detection devices are capable of detecting leaks in a larger area via the noise that may be produced by material leaking from the underwater structures. However, such acoustic systems only detect a secondary effect of the leak, i.e., noise. The performance capability of such acoustic systems may be severely restricted in noisy environments. Such acoustic systems are generally not able to precisely locate the source of the leak. 
         [0009]    The breakage or movement of components of a subsea facility, such as pipes, may provide direct evidence of a leak location or information on potential future leak sites. In some cases, such breakage or movement can be visually observed using video cameras or other like devices. However, current practice typically only allows for visual inspection via video cameras during routine surveys, or, in a few instances, via permanently deployed subsea camera systems. In both approaches, the detection of breakage or movement of subsea components, such as pipes, relies on the observational skills of the camera operator. This makes such camera based observation highly dependent on the skill, subjective judgment and diligence of the operators of such systems, and generally makes them less desirable for long-term, continuous monitoring of subsea facilities to detect leaks. 
         [0010]    The present invention is directed to various devices and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems. 
       SUMMARY OF THE INVENTION 
       [0011]    The following presents a simplified summary of the disclosed subject matter in order to provide a basic understanding of some aspects of the subject matter disclosed herein. This summary is not an exhaustive overview of the technology disclosed herein. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later. 
         [0012]    In one illustrative embodiment, a system for detecting leaks from a subsea system is disclosed which includes at least one subsea structure anchored to a sea floor, a fluorescence detector attached to the subsea structure, the fluorescence detector adapted to generate a light beam having a wavelength that will fluoresce material leaking from the subsea system when the material is irradiated with the light beam, and a camera adapted to observe the fluorescence of the material as it is being irradiated by the light source. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
           [0014]      FIG. 1  is a simplified schematic depiction of a prior art fluorescence detection device; 
           [0015]      FIGS. 2 and 3  are schematic depictions of a subsea facility employing one illustrative embodiment of the leak detection system described herein; and 
           [0016]      FIG. 4  is a schematic depiction of an illustrative fluorescence detection device that may be employed to detect leaks from subsea facilities, as described herein. 
       
    
    
       [0017]    While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Various illustrative embodiments are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
         [0019]    The present subject matter will now be described with reference to the attached figures. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase. 
         [0020]    The present disclosure is directed to a system for detecting leakage of undesirable materials, e.g., hydrocarbons, hydraulic fluid, chemicals, etc., from a subsea facility.  FIGS. 2 and 3  are, respectively, schematic side views and top views of portions of a subsea facility  100 . As depicted therein, the subsea facility  100  comprises a plurality of subsea components  22  that may have a plurality of interconnecting conduits  24 , e.g., pipes, wherein fluids, such as oil and gas, chemicals, etc., may flow between and among the various subsea components  22 . 
         [0021]    It should be understood that the system  100  depicted in  FIGS. 2 and 3  is intended to be representative in nature in that it may represent any type of subsea facility wherein it is desirable to monitor and detect the leakage of material from the system  100 . For example, the illustrative system  100  may be a subsea oil and gas production, drilling or storage facility, subsea processing, etc. Moreover, it should also be understood that the components  22  are intended to be representative of any of a variety of different types of components that may be found or employed in such a subsea facility  100 . For example, the illustrative components  22  may be a Christmas tree, a production manifold, a blowout preventer (BOP), a pump, a compressor, etc. Thus, as will be recognized by those skilled in the art after a complete reading of the present application, the present invention should not be limited to use with any particular type of system or any type of components of such a system. 
         [0022]    As shown in  FIGS. 2 and 3 , the system  100  further comprises a plurality of fluorescence detectors  30  and cameras  32 . The number and locations of the fluorescence detectors  30  and cameras  32  depicted in  FIGS. 2 and 3  is provided by way of example only, as the fluorescence detectors  30  and camera  32  may be positioned at any desired location within the system  100 . Moreover, it is not required that each fluorescence detector  30  be deployed with an associated camera  32 . Rather, the system described herein provides great flexibility as it relates to the number and positioning of the fluorescence detectors  30  and cameras  32  throughout the system  100  such that leak detection monitoring may be efficiently conducted. The camera  32  and the fluorescence detector  30  may be positioned in the system  100  as individual components, or the camera  32  and detector  30  may be packaged together as a single unit. 
         [0023]      FIG. 4  is a schematic depiction of an illustrative fluorescence detector  30  that may be employed as described herein. The fluorescence detector  30  projects a modulated beam of light  34  to illuminate a volume of water adjacent any desired portion of the system  100 , e.g., a portion of a pipe  24  or a component  22 . In general, the fluorescence detector  30  should be designed such that the sensing range of the fluorescence detector  30  is as large as possible. In one illustrative embodiment, the fluorescence detector  30  should have a sensing range of about 1-2 meters, or greater. The greater the volume of water encompassed within the modulated beam of light  34 , the more effective the fluorescence detector  30  will be at detecting leaks. The light  34  may be generated using a range of light sources including lasers and LED based systems. 
         [0024]    The light  34  has a wavelength that is close to the absorption band associated with the fluorescence emission of the leaking material, e.g., oil, hydraulic fluid, chemicals, test dyes, etc. Different hydrocarbon materials have varying excitation wavelengths, as do hydraulic fluids and commonly employed leak detection chemicals. Thus, in one illustrative example, to detect the leakage of oil from the system  100 , the light  34  may have a wavelength of approximately 349 nm which is suitable for the excitation of hydrocarbons or other hydrocarbon mixtures and other materials. Of course, to detect other types of material, the wavelength of the light  34  may be different. Determining the appropriate excitation wavelength for the light  34  may be readily determined based upon the intended application. 
         [0025]    In one illustrative embodiment, the fluorescence detector  30  may be like the ones described in UK patent application GB 2405467 and U.S. Pat. No. 4,178,512, both or which are hereby incorporated by reference in their entirety. 
         [0026]    The camera  32  may be any of a variety of different camera systems that are suited for the intended purpose described herein. The camera  32  may be permanently affixed to some portion of the system  100 . In some applications, the lens of the camera  32  may be coated with a marine anti-fouling coating to limit the growth of material, such as algae, on the lens. The growth of such material might adversely impact the ability of the camera  32  to perform its intended function. 
         [0027]    In one illustrative embodiment, the fluorescence detector  30  may be mounted on a schematically depicted pan and tilt scanning stage  40  to provide a means to direct the beam of light  34  toward various desired portions of the system  100 . The cameras  32  may also be mounted on such a pan and tilt scanning stage  40 . The design, structure and operation of such pan and tilt scanning stages  40  are well known to those skilled in the art. In one particularly illustrative embodiment, both the fluorescence detectors  30  and the cameras  32  are permanently mounted on various portions  22 ,  24  of the system  100 , and the fluorescence detectors  30  and cameras  32  are each mounted on pan and tilt scanning stages  40 . 
         [0028]    In operation, the fluorescence detector  30  generates the modulated beam of light  34 . The light  34  may be generated continuously, periodically or intermittently. Any leaking material within the volume occupied by the light  34  will fluorescence which can be readily observed by use of the camera  32 . Given the relatively large volume occupied by the beam of light  34 , the visual observation of fluorescing material, i.e., leaking material, may be more readily observed by a system operator as compared to the prior art fluorescence detectors described previously. In one illustrative example, the light  34  may occupy a volume of approximately 0.5 m 3 . 
         [0029]    Moreover, by mounting the fluorescence detectors  30  and/or cameras  32  on pan and tilt scanning stages  40 , the true source of the leak may be more readily detected. In some applications, depending upon the number and location of fluorescence detectors  30  deployed, it may be possible to use two or more of the fluorescence detectors  30  to more precisely locate the true source of the leak. 
         [0030]    The present system may also provide the potential to assess the quantity of the material that is leaking via the magnitude of the detected fluorescence signal as the fluorescence intensity for a given volume is proportional to the concentration of the fluorescent material in the volume. Such capability may permit operators to monitor any increase in the leakage rate based upon the amount of the leaking material detected over a period of time, e.g., the volume of the leaking material may decrease or increase from day to day. Such capability enables maintenance personnel to make informed decisions on the appropriate time to repair the source of the leak and/or to make future failure predictions. 
         [0031]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order or the various components stacked and assembled in different configurations. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.