Abstract:
A system according to an exemplary aspect of the present disclosure includes, among other things, a generator-detector configured to be attached to a pipe. The generator-detector is configured to measure the concentration of mercury in the pipe in a non-destructive manner. A method is also disclosed.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/359,269, filed Jul. 7, 2016, the entirety of which is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    This disclosure relates to a Mercury-in-Pipe Assessment Tool (MiPAT) for non-destructive analysis of all forms of mercury (Hg) present in process equipment including but not limited to vessels, piping, hoses, pumps, exchangers, and all types of pipelines. The MiPAT of this disclosure provides oil and gas producers, for example, with the ability to cost-effectively assess and monitor the concentration and distribution of adsorbed, absorbed, chemisorbed, and free liquid phase mercury in oil and gas production, gathering, and processing systems and pipelines including subsea pipelines. 
         [0003]    Current methods for the measurement of mercury in pipe are limited. One common method includes using a field portable handheld x-ray spectrometer to analyze an open end of a pipe or a coupon, which is a section of pipe that has been removed. Another technique involves pipe coupon digestion using a wet chemistry method, such as acid digestion, to prepare pipe coupons for analysis by AFS (atomic fluorescence spectroscopy) or AAS (atomic absorption spectroscopy), as examples. Another known method includes thermal desorption of a pipe coupon at about 800° C. to prepare the sample for analysis by AFS or AAS. 
       SUMMARY 
       [0004]    A system according to an exemplary aspect of the present disclosure includes, among other things, a generator-detector configured to be attached to a pipe. The generator-detector is configured to measure the concentration of mercury in the pipe in a non-destructive manner. 
         [0005]    In a further non-limiting embodiment of the foregoing system, the pipe is a portion of a pipeline for transporting oil or gas. 
         [0006]    In a further non-limiting embodiment of any of the foregoing systems, the pipe is a portion of a subsea pipeline. 
         [0007]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector includes a spectroscopic beam generator-detector. 
         [0008]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector is configured to measure the concentration of mercury at two locations within the pipe, and the generator-detector is configured to average the two measurements. 
         [0009]    In a further non-limiting embodiment of any of the foregoing systems, the two locations are about 180 degrees apart from one another. 
         [0010]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector uses neutron activation analysis. 
         [0011]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector includes a thermal neutron source and a gamma detector. 
         [0012]    In a further non-limiting embodiment of any of the foregoing systems, the system further includes at least one magnet configured to mechanically couple the generator-detector to the pipe. 
         [0013]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector is configured to measure mercury in the pipe down to a lower detection limit of 10 mg/kg±30%. 
         [0014]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector is configured to measure mercury in the pipe to a lower detection limit down to at least 10 ppm±50%. 
         [0015]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector is configured to measure mercury in the pipe to a lower detection limit down to 1 ppm±50%. 
         [0016]    In a further non-limiting embodiment of any of the foregoing systems, the generator-detector is configured for use underwater at a depth down to at least 75 meters (about 250 feet). 
         [0017]    A method according to an exemplary aspect of the present disclosure includes, among other things, mechanically coupling a device to a pipe, and measuring the concentration of mercury in the pipe using the device in a non-destructive manner. 
         [0018]    In a further non-limiting embodiment of the foregoing method, the pipe is a subsea pipe, and wherein the device is initially positioned on the pipe by a diver. 
         [0019]    In a further non-limiting embodiment of any of the foregoing methods, the device includes a generator-detector. 
         [0020]    In a further non-limiting embodiment of any of the foregoing methods, the generator-detector includes at least one of a spectroscopic beam generator-detector, a thermal neutron source, and a gamma detector. 
         [0021]    In a further non-limiting embodiment of any of the foregoing methods, the generator-detector is configured to measure mercury in the pipe to a lower detection limit down to at least 10 ppm±50%. 
         [0022]    In a further non-limiting embodiment of any of the foregoing methods, the generator-detector is configured to measure mercury in the pipe to a lower detection limit down to 1 ppm±50%. 
         [0023]    In a further non-limiting embodiment of any of the foregoing methods, the method includes deploying the device underwater at a depth down to at least 75 meters (about 250 feet). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1A  is a side view of an example MiPAT arranged relative to a section of pipe. 
           [0025]      FIG. 1B  is a sectional view taken along line  1 B- 1 B in  FIG. 1A  and illustrates the detail of the arrangement between the MiPAT and the section of pipe. 
           [0026]      FIG. 2  illustrates the example MiPAT of  FIGS. 1A-1B  in use relative to a section of subsea pipeline. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    The MiPAT of the present disclosure is a device (or combination of devices) that measures the concentration of mercury (Hg) within a pipe in a non-destructive manner. In particular, there is no need to harvest a pipe coupon when using the MiPAT. The MiPAT can be used to measure the concentration of mercury anywhere along the length of a piping run or pipeline. 
         [0028]      FIG. 1A  illustrates one example MiPAT  10  arranged relative to a pipe  12  viewed from a side.  FIG. 1B  is a cross-sectional view taken along line  1 B- 1 B in  FIG. 1A . As used in this disclosure, the term “MiPAT” is not a limiting term, and is used to refer to the device generally illustrated in  FIGS. 1A-1B , which includes a number of interconnected devices and components. 
         [0029]    In this example, the MiPAT  10  includes a generator-detector  14  electrically coupled to a data line  16  and a power line  18 . The data line  16  and power line  18  can be provided in a single conduit, which can be a tether (sometimes referred to as an “umbilical cord”). It should be understood that the generator and the detector can be separate components. In this example, however, the separate generator and detector components are within the same unit. The generator-detector  14  generally speaking has a dual functionality and is configured to both generate a beam of energy, and in particular a beam of neutrons, configured to permeate the pipe  12  and to detect when that beam is reflected back to the generator-detector  14 . 
         [0030]    The data and power lines  16 ,  18  are in turn connected to a controller  20  or other computing unit and a power source  22  at a remote location. While in this example the MiPAT  10  is tethered to a remote location, such as a boat or rig, in some examples the MiPAT may be battery powered and communicate wirelessly with a remote computing unit to accomplish data transfer. 
         [0031]    The controller  20  and power source  20  are illustrated schematically in the figures. It should be understood that the controller  20  could be part of a larger control module, or could alternatively be a stand-alone controller. Further, the controller  20  may be programmed with executable instructions for interfacing with and operating the various components of the MiPAT  10 . The controller  20  additionally includes a processing unit and non-transitory memory for executing the various control strategies and modes of the MiPAT. 
         [0032]    The generator-detector  14  in this example is mechanically coupled to an exterior of the pipe  12  by way of magnets  24 . The magnets  24  are of a sufficient strength to couple the generator-detector  14  to the pipe  12 , but do not interfere with the measurements of the generator-detector  14 . While magnets  24  are shown, generator-detector  14  may be coupled to the pipe exterior using other techniques. 
         [0033]    One example generator-detector  14  of this disclosure includes an exterior housing  26  attached to the magnets  24 . A spectroscopic beam generator-detector  28  is provided within the housing  26 . The magnets  24  are spaced-apart from one another, as shown in  FIG. 1B , such that the spectroscopic beam generator-detector  28  can project energy in the form of a neutron beam, for example, from an exterior surface of the housing  26  toward the pipe  12  without interfering with the magnets  24 . 
         [0034]    In one example of use, once the MiPAT  10  is affixed to the pipe  12  in a location of interest, the controller  20  instructs the generator-detector  14  to take a measurement. In response to instructions from the controller  20 , a neutron beam is generated and directed at the target location on the subject pipe. The neutron beam permeates the pipe  12 . As noted above, the beam can permeate up to a 1-inch thick pipe wall. Mercury within the pipe  12  will cause a specific gamma energy response that is detected and measured by the detector. The generator-detector  14  is configured to generate a signal corresponding to the gamma energy spectra, and the controller  20  is configured to interpret this signal as a particular level of mercury within the pipe  12 . Again, this is one example of use, and this disclosure extends to other examples. 
         [0035]    In one example, the MiPAT  10  measures the concentration of total mercury at two points, 180 degrees apart, e.g. at pipe top  27  (e.g., the location closest to the MiPAT) and pipe bottom  29  (e.g., the location furthest from the MiPAT) of a particular section of pipe, and reports the concentration as an average of the two points. In another example, the MiPAT  10  is moveable, either manually or by an automated mechanism, circumferentially around the pipe in the directions D 1 , D 2 . The MiPAT is shown in phantom in  FIG. 1B  at a location near the pipe bottom, at  10 ′. The MiPAT may be moveable up to 360° around the pipe to obtain additional measurements. In some examples, only two measurements are taken from a single MiPAT position. In other examples, additional measurements are taken at additional MiPAT positions. Those measurements can be averaged, and the concentration may be reported as the average. 
         [0036]    The MiPAT  10  has the capability of essentially “seeing through” a 1 inch thick pipe wall and measuring mercury down to a lower detection limit of 10 mg/kg±30%. Alternatively the MiPAT  10  can measure mercury down to a lower detection limit of 10 parts per million (ppm)±50%. In a further example, the MiPAT  10  can measure mercury down to a lower detection limit of 1 ppm±50%. 
         [0037]    The MiPAT  10  in one example is configured for use underwater at depths down to 75 meters (about 250 feet). In other examples the MiPAT  10  is deployable to depths down to 100 meters (about 330 feet). 
         [0038]    Another example generator-detector  14  uses neutron activation analysis. In that example, the generator-detector  14  includes a thermal neutron source (or generator) and a gamma detector that can operate with high resolution, high efficiency and without liquid nitrogen in confined spaces. Yet another example generator-detector  14  includes a radioactive source. Other example generator-detectors  14  includes a neutron generator and sodium iodide (NaI) detectors, and a high purity geranium (HPGe) detector. The generator-detectors  14  may be electromechanically cooled. 
         [0039]    The generator-detector  14  may include a single detector and multiple sources, although this disclosure extends to generator-detectors having at least one source (generator) and at least one detector. 
         [0040]    With reference to  FIG. 2 , the MiPAT  10  is capable of being manually affixed to an exposed underground or underwater pipe  12 , by way of the magnets  24 , for example. In  FIG. 2 , the pipe  12  is fluidly coupled between two oil platforms  30 ,  32 , and is sometimes referred to as a conductor pipe. The platforms  30 ,  32  project from the seafloor  34  above the water line (or water level)  36 . 
         [0041]    As shown in  FIG. 2 , a relatively long run of the pipe  12  is covered by mud at the seafloor  34  and may be encased in concrete. In those cases, the concrete and/or mud is removed by a dive team, for example, to expose the pipe  12  and allow for fixation of the MiPAT  10  relative to the pipe  12 . 
         [0042]    While the seafloor  34  and concrete adjacent the pipe  12  may need to be removed, a benefit of the MiPAT  10  is that the pipe  12  does not have to be cut, disassembled, or opened during the assessment process. In other words, the measurements of the present disclosure are taken in a non-destructive manner. In particular, since the present disclosure allows measurements to be taken in a non-destructive manner, measurements can be taken without requiring a system shutdown (e.g., the platforms  30 ,  32  can continue normal operations). These features reduce the risk of exposure to vapor inside the pipe  12 , including mercury and/or hydrocarbon vapors, and reduces the time and effort required to obtain accurate and representative measurements of mercury in process piping and pipelines. 
         [0043]    Referring back to  FIG. 2 , when used in subsea applications, the MiPAT includes a water proof housing  38  designed so that the generator-detector  14  can be deployed in water depths up to  100  meters for the assessment of subsea pipelines. The MiPAT can be deployed by divers or by a remotely operated vehicle (ROV)  40 . When an ROV  40  is used, the ROV  40  can include the controller  20  and power source  22  in one example. 
         [0044]    The MiPAT  10  of the present disclosure may be used to serve oil and gas operators in the decommissioning of mercury impacted offshore oil and gas production facilities and subsea pipelines. The MiPAT may also be used for the monitoring of mercury accumulation in operating pipelines. The MiPAT also provides oil and gas producers with an easily deployable tool for assessing the concentration and distribution of mercury along the length of any piping section or subsea pipeline ultimately providing a more accurate representative assessment of mercury in pipe. Specifically, while the MiPAT  10  is shown adjacent a section of the pipe  12  that is subsea, the MiPAT can be used to analyze the pipe  12  at locations above the seafloor  34  or above the water line  36 . 
         [0045]    To this end, while  FIG. 2  shows the MiPAT  10  used in the context of offshore drilling, the MiPAT  10  is not limited to such uses, and can be used in other environments. For example, the MiPAT  10  can be used in scrap yard/smelter operations for rapid assessment and monitoring of steel pipe. The MiPAT  10  is also deployable on production platforms, processing plants, refineries, etc. 
         [0046]    It should be understood that terms such as “generally,” “substantially,” and “about” are not intended to be boundaryless terms, and should be interpreted consistent with the way one skilled in the art would interpret those terms. 
         [0047]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0048]    One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.