Abstract:
According to some embodiments, a testing system that is configured to test subsea power components in-situ while they are deployed on the sea floor. The testing system includes a top side testing system with test instruments, a multi-conductor work-over umbilical cable, and a subsea deployable test head. The test head can be deployed using and ROV and makes electrical connection to the subsea power component via wet connects.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to electrically powered subsea systems. More particularly, the present disclosure relates to systems and methods configured for in-situ testing and/or monitoring of subsea power components while on the seafloor. 
       BACKGROUND 
       [0002]    In subsea environments, various fluid processing systems can be deployed. For example, in the case of seafloor-deployed fluid processing equipment for the oil and gas industry, various types of electrically powered systems are used such as subsea fluid pumps and subsea compressors. Additionally, in cases where the umbilical power supply system is relatively long, subsea step-down power transformers can be deployed on the seafloor to allow for more higher voltage energy transmission through the umbilical system. Prior to deployment of such electrically powered components (e.g. electric motors used to drive pumps or compressors and transformers) on the seafloor, each component can be tested for various electrical faults, such as insulation faults, including ground faults, as well as continuity faults. Currently, such electrical testing is performed on the surface prior to deployment of the components on the seafloor, for example on a surface vessel being used to deploy the equipment, or on land. While such surface testing of the electrical components is useful in detecting electrical faults prior to deployment, they do not detect faults that may arise during transportation through the seawater and onto the seabed, nor do they detect faults that may arise during the time the components are placed on the seabed prior to being put into operation. 
       SUMMARY 
       [0003]    This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
         [0004]    According to some embodiments, a system is described for in-situ testing of a power component in a subsea environment. The system includes: a surface subsystem which includes testing equipment configured to measure electrical characteristics of the power component from which electrical faults can be determined; a subsea subsystem configured for deployment in a subsea environment, including connectors (such as releasable wet connectors) configured to transmit electricity between the subsea test subsystem and the power component; and a cable which includes electrical conductors for transmitting electricity between the surface test subsystem and the subsea test subsystem. When the connectors are connected to the power component electrical faults can be determined based on the electrical measurements of the power component by surface test subsystem. 
         [0005]    According to some embodiments, the subsea subsystem also includes a negatively buoyant subsea test head on which the connectors are mounted. The test head can be configured for deployment in the subsea environment using a remotely operated underwater vehicle (ROV). The power component can be configured for continuous deployment in the subsea environment for at least five years. 
         [0006]    According to some embodiments, the power component is a subsea motor that can be used to drive a subsea device such as a subsea pump, a subsea compressor, or a subsea separator. The power component can be powered by three-phase electric power, the subsea subsystem can include at least three connectors (such as releasable wet connectors), and the cable can include at least three electrical conductors. The power component can form part of a fluid processing system that is configured to process hydrocarbon bearing fluids produced from a subterranean rock formation. According to some other embodiments, the power component is not an electric motor but rather some other type of subsea power component. Examples include a subsea transformer, a subsea variable frequency drive (VFD) and subsea switchboard. According to some embodiments the connector can be a single connector with multiple electrical connection elements such as pins, or pin-receptacles arranged in a male, female, or combinations of male/female elements. According to some embodiments, the connector or connectors are a stab-type connector(s). 
         [0007]    The cable can be a suspension cable configured to suspend a negatively buoyant subsea test head on which the connectors are mounted. According to some other embodiments, the cable can be an umbilical cable used to deploy a remotely operated underwater vehicle (ROV) that in turn is used to deploy a negatively buoyant subsea test head on which the connectors are mounted. 
         [0008]    According to some embodiments, a method is described for in-situ testing of a power component in a subsea environment. The method includes: deploying a surface subsystem to a surface location; deploying a subsea subsystem to the power component which is deployed at a subsea location, the subsea subsystem being in electrical communication with the surface subsystem at least in part through a cable including electrical conductors; making electrical connection between the subsea subsystem and the power component using connectors (such as releasable wet connectors); and measuring with the surface subsystem electrical characteristics of the power component from which electrical faults can be determined. According to some embodiments, after the measuring, the method can further include: disconnecting the connectors from the power component; and operating the power component. 
         [0009]    According to some embodiments, one or more of the described systems and/or methods can be used in topside or subsea fluid processing equipment in an analogous fashion. 
         [0010]    According to some embodiments, a subsea system is described for in-situ testing of a power component in a subsea environment. The system includes: a housing configured for deployment in a subsea environment; testing equipment configured to measure one or more electrical characteristics of the power component from which one or more electrical faults can be determined; and one or more connectors configured to transmit electricity between the testing equipment and the power component, wherein when the connectors are connected to the power component the one or more electrical faults can be determined based on the one or more electrical measurements of the power component by testing equipment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The subject disclosure is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the subject disclosure, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
           [0012]      FIG. 1  is a diagram illustrating a subsea environment in which a subsea power component testing system is deployed, according to some embodiments; 
           [0013]      FIG. 2  is a diagram illustrating some aspects of a subsea power component testing system, according to some embodiments; 
           [0014]      FIGS. 3A and 3B  are diagrams illustrating further aspects of a test head used for subsea power component testing, according to some embodiments; 
           [0015]      FIG. 4  is a flow chart illustrating some aspects of in-situ testing of subsea power components, according to some embodiments; and 
           [0016]      FIG. 5  is a diagram illustrating some aspects of an integrated subsea power component testing system, according to some embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The particulars shown herein are by way of example, and for purposes of illustrative discussion of the embodiments of the subject disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the subject disclosure. In this regard, no attempt is made to show structural details of the subject disclosure in more detail than is necessary for the fundamental understanding of the subject disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the subject disclosure may be embodied in practice. Further, like reference numbers and designations in the various drawings indicate like elements. 
         [0018]    According to some embodiments, techniques are described that avoid drawbacks associated with surface-only testing of subsea power components such as subsea transformers and subsea electric motors. A testing system that is configured to test subsea power components in-situ while they are deployed on the sea floor is described. Unlike surface-only testing, such subsea in-situ testing is able to detect faults that may arise during transportation though the seawater and onto the seabed, as well as during the time the components are placed on the seabed prior to being put into operation. 
         [0019]      FIG. 1  is a diagram illustrating a subsea environment in which a subsea power component testing system is deployed, according to some embodiments. On sea floor  100  a station  120  is shown which is downstream of several wellheads being used, for example, to produce hydrocarbon-bearing fluid from a subterranean rock formation. Station  120  includes a subsea pump  130 . The station  120  is connected to one or more umbilical cables, such as umbilical  132 . The umbilicals in this case are being run from a platform  112  through seawater  102 , along sea floor  100  and to station  120 . In other cases, the umbilicals may be run from some other surface facility such as a floating production, storage and offloading unit (FPSO), or a shore-based facility. In addition to pump  130 , the station  120  can include various other types of subsea equipment, including other power components such as other pumps and/or compressors, and one or more subsea step-down transformers. Subsea step-down transformers can be used, for example, where it is desirable to supply high-voltage power through the umbilical  132 . The umbilical  132  can also be used to supply barrier and other fluids, and control and data lines for use with the subsea equipment in station  120 . 
         [0020]    Also visible in  FIG. 1  is ROV  142 , tethered using main lift umbilical  146  and tether management system  144  and tether cable  148 . According to some embodiments, ROV  142  is being used to deploy test head  150  that is configured to make electrical connection with and facilitate testing of one or more power components, such as transformers and/or motors used to drive pumps and/or compressors in station  120 . The test head  150  is deployed using umbilical cable  152  from surface vessel  140 , which is also being used to deploy ROV  142 . 
         [0021]      FIG. 2  is a diagram illustrating some aspects of a subsea power component testing system, according to some embodiments. Above the sea surface  210 , the power component testing system includes a topside system  250  that in this example resides within vessel  140 . The topside system  250  includes a testing container  252  that houses power test instruments  254  and terminals  256 . The umbilical cable  152  is handled by cable handling system  258 . The test instruments are configured to carry out the electrical tests, for example isolation resistance testing, high voltage testing and continuity testing. According to some embodiments, the umbilical cable  152  simply contains three high-voltage high-current conductors such that the test instruments  258  can be similar or identical to known test instruments used in similar tests in a surface environment. Below surface  210  is the subsea system  240  that includes a portion of umbilical cable  152  as well as test head  150 . Subsea test head  150  is shown being deployed on electrical power component  130  which can be, for example, an electric motor used to drive a subsea compressor or pump, or a subsea transformer. Test head  150  is preferably negatively buoyant and is shown being deployed using ROV  142  that includes an ROV manipulator arm  244  that can include a tool and/or TV  242 . ROV  142  also includes a light  246 . ROV  142  is shown positioning test head  150  on ledge  232  of component  130  such that connectors on head  150  are aligned with connectors  230  on component  130 . According to some embodiments, the cable  152  is a simple deployment cable without electrical conductors, and the power connection with component  130  through test head  150  is provided instead through ROV  142 , ROV tether cable  148  and mail lift umbilical  146  to vessel  140  (and to terminals  256 ). 
         [0022]      FIGS. 3A and 3B  are diagrams illustrating further aspects of a test head used for subsea power component testing, according to some embodiments. In  FIG. 3A , test head  150  is shown being positioned above shelf  232  on component  130  such that docking cones  360  on head  150  are aligned with guideposts  330  on shelf  232 . The test head  150  is lowered down on the shelf  232  with ROV  142  (not shown) and suspension cables  314 . In  FIG. 3B , test head  150  is shown fully lowered on the shelf  232 . The wet make-break (i.e. connectable and releasable) electrical connectors  350  are urged to mate with connectors  230  on component  130 , for example, using a leadscrew mechanism that includes a spindle  320  that is driven by an ROV using a standard ROV operated spindle handle  310 . The lead screw mechanism pushes terminal box  324  and compliant mount wet connectors  350  to mate with connectors  230  on component  130 . According to other embodiments another type of connector or connectors are used. For example, according to some embodiments, a direct electric submersible pump (ESP) ROV stab-type connector is used. According to some embodiments a single connector is used that includes three pins for making three separate electrical connections between test head  150  and component  130 . According to other embodiments, other arrangements and/or combinations of connector elements (e.g. male vs. female mating surfaces, pins, plugs, blades, sockets, etc.). According to some embodiments the number of connectors is one, two, three or more connectors depending on the application and the type of connectors used. According to some embodiments, other structures are used for positioning and/or aligning the connectors than the docking cones and guidepost arrangement shown in  FIGS. 3A and 3B . 
         [0023]      FIG. 4  is a flow chart illustrating some aspects of in-situ testing of subsea power components, according to some embodiments. In block  410  the subsea power component, for example, a pump or compressor module with an integrated electric drive motor or a subsea transformer, is positioned on the sea floor. Some time after the subsea component is positioned on the sea floor and before it is put into operation, the in-situ testing is carried out. In block  412 , the subsea test head, such as head  150  shown in  FIGS. 1, 2 and 3 , is positioned onto the subsea component. The test head is preferably negatively buoyant and is placed using an ROV. According to some embodiments, docking cones and guideposts are used to align the test head in a suitable position with respect to the power component. In block  414 , the test head wet-connect is mated with the power connectors on the power component. In the case of three-phase power, each of three power connectors from the test head is mated with the appropriate supply power connector on the power component being tested. According to some embodiments, the ROV is used to make the connections. In some examples, the ROV turns a spindle that actuates a leadscrew that pushes the make-break connectors forward. In block  416 , the surface-based testing instruments perform various electrical tests on the power component, using conductors running between the surface equipment and the subsea test head. According to some embodiments, the tests performed include high voltage (e.g. 5 KV) insulation resistance testing (e.g. using a megohmmeter) to detect insulation failures (e.g. ground faults), and continuity tests to detect broken conductors. In block  418 , if testing is satisfactory, the test head connectors are removed from the power component and the test head is lifted away, for example using an ROV. According to some embodiments, further power components can be tested by the same test head. For example, if there are other motors and/or transformers on the same subsea station, the ROV can relocate the test head for testing of such components. In block  420 , the power jumpers for the tested power component are connected. For example, in the case of subsea transformer or subsea motor the power supply, jumpers from an umbilical termination head, or from a transformer are connected. Fluid connections can also be made, if necessary prior to placing the tested power component into operation. 
         [0024]      FIG. 5  is a diagram illustrating some aspects of an integrated subsea power component testing system, according to some embodiments. In this case, test instruments  554  are included in the test head  150  instead of being located on the surface (e.g. instruments  254  in  FIG. 2 ). The test instruments  554  are configured to carry out the electrical tests, for example isolation resistance testing, high voltage testing and continuity testing. According to some embodiments, the testing is remotely controlled via the ROV  142  communicating via its surface link through tether cable  148 , or via control signals carried within cable  152 . According to some other embodiments, a hybrid system is used wherein some testing instruments  554  integrated in head  150  are combined with and some surface testing instruments  245  (as shown in  FIG. 2 ) are used to carry out the electrical tests of subsea power component  130 . 
         [0025]    While the techniques for in-situ testing of subsea power components have thus far been described in the context of testing prior to operation. According to some embodiments, the test head and other testing system components can be used for testing of such power components during their lifetime installed on the seafloor without having to retrieve the power components to the surface. 
         [0026]    While the techniques for in-situ testing of subsea power components have thus far been described in the context of testing power components such as three-phase transformers and/or subsea motors for driving pumps and compressors, other types of power components can be tested. Examples of other types of power components include subsea variable frequency drives (VFDs) and subsea switchboards. According to some embodiments, two-phase, single phase electrically power subsea components can also be tested in-situ in the subsea environment using the techniques described herein. 
         [0027]    While the subject disclosure is described through the above embodiments, it will be understood by those of ordinary skill in the art that modification to and variation of the illustrated embodiments may be made without departing from the inventive concepts herein disclosed. Moreover, while some embodiments are described in connection with various illustrative structures, one skilled in the art will recognize that the system may be embodied using a variety of specific structures. Accordingly, the subject disclosure should not be viewed as limited except by the scope and spirit of the appended claims.