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CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to remote monitoring of flow conduits, such as pipelines and wellbores, and more particularly to a system of self-contained measurement stations for measuring parameters of interest of the flow conduit and transmitting the measurements to a mobile interrogation device. 
     2. Description of the Related Art 
     Fluid conduits such as pipelines and aqueducts extend for tens, hundreds, or thousands of kilometers and may be used to transport liquids, gases, slurries or combinations thereof. Such conduits may have multiple sections that run above or below ground. Sections may be run underground to avoid natural obstacles such as rivers or simply as a safety precaution. Other sections may be run above ground depending on the topography and underlying strata. Sensing stations are commonly located at major features, such as pumping station that may be separated by tens or hundreds of kilometers. Sensors are used to determine any of a number of parameters of interest related to the operation and safety of the conduit and/or related to the fluid transported therein. However, due to the relatively large separation of these stations, conditions that may be indicative of potential problems or failures may go undetected until they become so great as to cause a catastrophic event, such as for example a substantial leak that may be a serious environmental problem. It would be highly desirable to be able to determine various parameters relating to the physical condition of the conduit including, but not limited to, mechanical strain and stress, crack initiation and propagation, temperature, acceleration and vibration, seismic events, corrosion, pressure integrity, and flowing fluid properties, such as chemical species, radiation, and chemical contamination. The very nature of the length and location of such conduits, however, make the distribution of power and signal lines to multiple measurement stations substantially impractical and cost prohibitive. 
     There is a demonstrated need for a system for providing more measurements along fluid conduits without the need for additional power and signal lines. 
     SUMMARY OF THE INVENTION 
     The present invention contemplates a system for monitoring a flow conduit using remotely interrogated measurement stations disposed along the conduit. 
     In one preferred embodiment, a system for monitoring at least one parameter of interest relating to a flow conduit having a through passage and a fluid flow therein comprises at least one measurement station coupled to the flow conduit for taking a measurement relating to the parameter of interest. An interrogation device is adapted to move proximate the measurement station and to transmit a first signal to the measurement station, and to receive a second signal from the measurement station relating to the parameter of interest. 
     In one aspect, a method for monitoring at least one parameter of interest relating to a flow conduit having a fluid flow therein, comprises coupling at least one measurement station to the flow conduit at a predetermined location. The measurement station is adapted to measure the at least one parameter of interest. An interrogation device is passed proximate the at least one measurement station. A first signal is transmitted from the interrogation device to the measurement station, and the measurement station measures the at least one parameter of interest in response thereto. A second signal related to the parameter of interest and transmitted by the measurement station is received at the interrogation device. 
     In another aspect, a system for determining at least one parameter of interest relating to a flow conduit having a fluid flowing therein, comprises making the flow conduit from a composite material. At least one electrical conductor is embedded along the flow conduit in the composite material, and is adapted to transmit and receive radio frequency signals. A plurality of measurement stations are disposed, spaced apart, along the flow conduit at predetermined locations. Each of the plurality of measurement stations is adapted to receive a first signal transmitted from the at least one electrical conductor and to transmit a second signal in response thereto related to a measurement of the at least one parameter of interest. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
         FIG. 1  is a schematic drawing of a fluid conduit traversing an uneven terrain; 
         FIG. 2  is a schematic drawing of a self contained measurement and information station according to one embodiment of the present invention; 
         FIG. 3  is a schematic drawing of a measurement module of a self contained measurement and information station according to one embodiment of the present invention; 
         FIG. 4  is a schematic drawing of an articulated conduit inspection pig for use as a mobile interrogation device according to one embodiment of the present invention; 
         FIG. 5  is a schematic drawing showing an automotive device and an aircraft device for use as mobile interrogation devices according to one embodiment of the present invention; 
         FIG. 6  is a schematic drawing of a composite conduit with embedded conductors for transmitting command signals and/or power to multiple measurement stations according to one embodiment of the present invention; 
         FIG. 7  is a schematic drawing of a coiled composite tubing having embedded conductors and a plurality of self contained measurement and information stations disposed along the tubing according to one embodiment of the present invention; and 
         FIG. 8  is a schematic drawing of a casing with a plurality of self contained measurement and information stations disposed along the tubing and an interrogation device deployed on a tubular member according to one embodiment of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In one preferred embodiment, see  FIG. 1 , a fluid conduit  1  extends across terrain  10 . Note that the term fluid conduit as used herein, means a closed conduit, such as a pipeline or other substantially tubular member, and an open conduit such as an aqueduct for transporting liquids such as water. Such conduits may extend for tens, hundreds, or thousands of kilometers and may be used to transport liquids, gases, slurries or other fluids. The conduit  1 , for example may be a pipeline having multiple sections  5 ,  6 ,  7  that run above or below ground. Sections may be run underground to avoid natural obstacles such as river  8  or simply as a safety precaution. Other sections may be run above ground depending on the topography and underlying strata. Self contained measurement and information stations  20 , called measurement stations for simplicity, are disposed along conduit  1  at predetermined locations, to determine any of a number of parameters of interest related to the operation and safety of the conduit and/or related to the fluid transported therein. The greater the number of measurement stations  20 , the better will be the confidence that the conduit is operating properly. Various parameters may be measured relating to various physical conditions including, but not limited to, mechanical strain and stress, crack initiation and propagation, temperature, acceleration and vibration, seismic events, corrosion, pressure integrity, and flowing fluid properties, such as flow rate and chemical species, radiation, and chemical contamination. For an open channel, such as an aqueduct, measurement stations  20  may be mounted to determine parameters related to the flow channel such as, for example, seismic events, and/or for determining parameters related to the flowing fluid. Such fluid related parameters, for a water supply flow for example, may relate to chemical analysis and water purity or to contamination by chemical and/or biological agents. The very nature of the length and location of such conduits make the distribution of power and signal lines to multiple measurement stations  20  physically impractical and cost prohibitive. 
       FIG. 2  shows one preferred embodiment of measurement station  20  having measurement module  30 , radio frequency (RF) transmitting and receiving antenna  22 , and flexible adhesive base  21  for attaching measurement module  30  to flow conduit  1 . In one embodiment, see  FIG. 3 , measurement module  30  includes at least one sensor  27  for detecting the parameter of interest. Alternatively, sensor  27  may be external to measurement module  30  and suitably electrically connected using techniques known in the art. Interface module  24  conditions the output signal from sensor  27 , if necessary, and transfers the signal to data memory in controller module  23 . Controller module  23  has a processor with sufficient memory for storing program instructions and for storing acquired sensor measurement data. The controller module may contain a unique identification, such as a digital identifier, for uniquely identifying each measurement station  20  that may be used for correlating the measurements with location on the conduit  1 . Also included is RF transceiver  26  for receiving command and power signals and for transmitting data signals in response to the received command signals. 
     In one preferred embodiment, the measurement module  30  has no internal power source, but receives power via the received RF signal. This power is converted to usable power by power module  28 . Sensor  27  is chosen as a low power sensor such that the RF link transmits sufficient power to power measurement module  30  including sensor  27  and to transmit the resulting data signal using RF transceiver  26 . The components of measurement module  30  are encapsulated in a suitable compound  29  to protect the components from the environment. 
     The RF command signal and RF power are transmitted from, and the data signals received by, a mobile interrogation device (see  FIGS. 4 and 5 ) such as an internal inspection pig  40 , an automotive device  45 , and an aircraft device  50 . Inspection pigs are commonly self-powered for movement in the conduit or, alternatively, may be pumped through flow conduit  1 . Any type of inspection pig is suitable for this invention The automotive device  45  may be any common vehicle including, but not limited to an automobile, a truck, and an all-terrain vehicle. The automotive device, is adapted to carry an RF transceiver (not shown) and a controller (not shown) transmitting command signals and power to measurement stations  20  and receiving and storing data signals from measurement stations  20 . The aircraft device  50  may be an airplane, helicopter, or any suitable aircraft and may be manned or a remotely controlled, unpiloted aircraft. Remotely controlled aircraft device  50  may be preprogrammed to follow a predetermined flight pattern along the known path of flow conduit  1 , using, for example, preprogrammed way points and GPS signals to guide aircraft device  50  along the predetermined flight pattern. Relatively small remotely controlled vehicles are commercially available. 
     The placement of a particular measurement station  20  at a predetermined location and the type of flow conduit  1  will be used to determine the type of interrogation device used for that particular measurement station  20 . For example, the flow conduit  1  may be (i) a tubular conduit of metallic material such as steel, (ii) a tubular conduit out of a non-metallic material such as a composite material, or (iii) an open-channel conduit. For a metallic conduit, the RF energy will not penetrate the conduit. Therefore, a measurement station  20  mounted inside the metallic conduit  1  (see  FIG. 4 ) requires an internal interrogation device such as a pipeline pig  40 . A measurement station  20  mounted outside of a metallic conduit  1  (see  FIG. 5 ) requires an external interrogation device such as automotive device  45  and/or aircraft device  50 . For a composite material, the conduit  1  is substantially transparent to RF energy and allows the measurement stations  20  to be mounted internally, externally, and/or embedded within the conduit and be able to operate with an internal and/or external interrogation device. 
     The sensors  27  used to detect the parameters of interest include, but are not limited to, (i) mechanical strain gages, (ii) fiber optic strain gages, (iii) ultrasonic detectors for detecting micro-crack initiation and propagation, (iv) accelerometers, (v) temperature sensors, including distributed fiber optic temperature sensors known in the art, (vi) pressure sensors, (vii) corrosion detectors, (viii) radiation detectors, (ix) spectroscopic chemical detectors, and (x) ultrasonic detectors for measuring the wall thickness of the flow conduit for detecting erosion and/or corrosion of the conduit. The sensors  27  may detect characteristics associated with the conduit and/or the fluid flowing therein. One skilled in the art will recognize that many of the sensors, for example accelerometers and seismic detectors, are currently achievable using Micro Electromechanical Systems (MEMS) fabrication techniques for providing low power consumption devices. Other sensors are available using piezoelectric crystal technology or resonant crystal technology that require very low power consumption. Thermocouple temperature sensors, for example, generate their own electrical signal and do not require external power to operate. 
     In operation, the measurement stations  20  are disposed along the flow conduit  1 . The measurement stations  20  may be both above and below ground along the length of flow conduit  1  depending on the path of conduit  1 . An interrogation device is caused to pass in relative proximity to the measurement stations  20 . The interrogation device has an RF transceiver for transmitting command signals and power to the measurement stations  20  and for receiving data signals from the measurement stations  20 . The data collected is downloaded from the interrogation device, using techniques known in the art, to a central control station (not shown) for monitoring the various parameter data collected. 
     In another preferred embodiment, measurement module  30  includes an internal power source (not shown) for powering the electronic devices and sensors as required. The internal power source may include, but is not limited to, (i) a commercially packaged battery, (ii) a thick film battery integrally attached to the measurement module, (iii) a piezoelectric power source deriving power from shock and vibration in the proximity of the measurement module, (iv) a solar cell integrated into an external surface of the measurement module, and (v) a thermoelectric generator integrated into the measurement module. All of these power sources are known in the art. Any combination of these sources may be used and their selection is application specific, and may be determined without undue experimentation, by considering such factors as (i) power required for the type of sensors, (ii) transmission strength required of data signals, and (iii) location of measurement station and flow conduit (for example, above ground or below ground). 
     In another preferred embodiment, the power sources described above are mounted external to the measurement module  30  and connected to the measurement module via connectors and/or cables using techniques known in the art. 
     In one preferred embodiment, measurement module  30  contains a real time clock for time stamping measurements. A low power seismic detector, for example, may be continuously measuring seismic activity, but the data is only stored and time stamped if the sensed event exceeds a predetermined threshold or alarm criterion. The data is retrieved by the interrogation device and may be used to indicate that more extensive inspection is needed in the area where the seismic event was detected. 
     In one preferred embodiment, shown in  FIG. 6 , composite fluid conduit  60  has electrical conductors  61  embedded in the wall  63  of fluid conduit  60  during the manufacturing process for forming the conduit. Measurement stations  20  are disposed along the conduit at at least one of (i) on an internal walls of conduit  60 , (ii) on an external wall of conduit  60 , and (iii) embedded in a wall  63  of conduit  60 . The electrical conductors  61  may be disposed substantially longitudinally in the wall of conduit  60 . Alternatively, the electrical conductors  61  may be spirally wrapped in the wall of conduit  60 . Electrical conductors  60  are connected to RF transceiver (not shown) in a controller  62 . Power and command signals are transmitted through the conductors which act as RF antennas. The signals are detected by the measurement modules  30  along the conduit. The measurement stations  20  receive and convert the RF signals to power and command instructions for taking data from sensors in the measurement modules  30 . The data are then transmitted via an RF signal that is received by the electrical conductors  61  and decoded by controller  62 , according to programmed instructions. The signals from measurement stations  20  are suitably encoded and identified, using techniques known in the art, so as to be able to determine the measurement stations  20  associated with each data signal. 
     In one preferred embodiment, see  FIG. 7 , a composite conduit, as described previously having embedded electrical conductors and internal, external, and/or embedded measurement stations  20 , may be formed as a coiled tubing  71 , contained on reel  70 , for use in drilling and/or completing a wellbore  72 . Measurements from measurement modules  30 , embedded in the coiled tubing  71 , may be used to determine parameters of interest regarding the condition of the tubing string and/or parameters related to the drilling process. Such parameters of interest include, but are not limited to, (i) directional parameters, (ii) drilling induce vibration, including axial and torsional, (iii) weight on bit, (iv) downhole pressure, (v) downhole temperature, and (vi) formation parameters including natural gamma ray emission. 
     In one preferred embodiment, see  FIG. 8 , metallic casing  83  is fixed in place in production wellbore  80 . Measurement modules  30  are fixed to an internal surface of casing  83  and measure parameters of interest including, but not limited to, (i) fluid pressure, (ii) fluid temperature, (iii) fluid flow rate, (iv) corrosion, and (v) casing stress. An interrogation device  82  is deployed on wireline  81  and is passed in proximity to measurement modules  30  and has an RF transceiver that transmits RF power and command signals to measurement modules  30 , which in turn, make measurements and transmit that data via RF transmission to interrogation device  82 . Interrogation device  82  has internal memory for storing the received data and is downloaded at the surface. Alternatively, wireline  81  has electrical conductors and received data is transmitted directly to the surface. The interrogation device  82  may alternatively be deployed on a coiled tubing (not shown) using techniques known in the art.

Summary:
A system for monitoring at least one parameter of interest relating to a flow conduit having a through passage and a fluid flow therein comprises at least one measurement station coupled to the flow conduit for taking a measurement relating to the parameter of interest. An interrogation device is adapted to move proximate the measurement station and to transmit a first signal to the measurement station, and to receive a second signal from the measurement station relating to the parameter of interest. The measurement station receives power from the first signal.