Page 64 - Wire Rope News & Sling Technology - April 2019
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         System and method for deployment and retrieval of
         seismic nodes along a carrier rope
         Pat. 10,209,382 U.S. class B63B 21/60  Int. class G01V 1/38
         Inventor: Ian McMillan, Houston, TX., Michael Russell, Vil-
         lentrois,  FR., Thomas Hills, Alicanye, ES., Terje Nalum,
         Stavern, NO.
         Lysaker, NO.
           This patent presents a system for attaching a plurality
         of seismic nodes along a main carrier rope. The main car-
         rier rope is made of steel or synthetic fiber, and comprises
         no power or communication lines. The system has a length   Figure 19: Schematic illustration of system and method for deployment
         measuring device for providing a measured length (L m) of   and retrieval of seismic nodes.
         deployed main carrier rope; a data source for providing posi-
         tioning data affecting the rope position of each seismic node   L 3 of rope can be provided between different pairs of nodes
         on the main carrier rope; a control unit for providing an at-  110.  In other  words,  each  seismic  node 110 has  a unique
         tachment command whenever the measured length (L m) cor-  rope position along the main carrier rope, and these rope po-
         responds to a rope position of a seismic node computed from   sitions need not have a constant and equal distance between
         the positioning data; and a node attaching unit for attaching   them. Thus, the nodes 110 can be deployed at their preferred
         a seismic node to the main carrier rope in response to the   positions along the path 10 independently of their rope po-
         attachment command. The system is capable of attaching   sitions along the main carrier rope 101. This combines the
         nodes with different node spacing between some or all nodes   ability to deploy the nodes 110 at their preferred positions
         along the main carrier rope. As the rope positions are deter-  on the seafloor with the convenient retrieval of nodes 110
         mined by the measured length (L m), the system automati-  attached to a main carrier rope.
         cally compensates for creep or stretch in the main carrier   Figure 18 illustrates a similar scenario, where the main
         rope. Attaching a seismic node to the main carrier rope at   carrier rope 101 rests on a sloping seafloor. In figure 18, the
         any rope position by means of a clamping device, a suspen-  desired horizontal distance is denoted y to emphasize that
         sion device and a fly line is also disclosed.        the desired distances may vary between different applica-
           Figures 17 and 18 illustrate the context of the present in-  tions, e.g. one depicted in figure 17 and another in figure 18.
         vention. In figure 17 nodes 110 are attached to a main carri-  As shown, the desired distance y can be obtained by provid-
         er rope 101. The main rope 101 does not contain power lines   ing different node spacings L 4 and L 5 measured along the
         or communication lines. The nodes 110 are to be deployed   main carrier rope 101.
         along a desired path 10. The path 10 is depicted as a straight   Figure 19 schematically illustrates a system 1 according to
                                                              the invention. The main carrier rope 101 is shown during de-
                                                              ployment. The nodes 110 are to be attached to the rope 101
                                                              with variable distances, e.g. the distances L 1-L 5 in figures
                                                              17 and 18. For this, the system 1 comprises a control unit
                                                              200 that compares a measured length L m with the desired
                                                              length, e.g. L 1, and attaches a new node 110a to the main
                                                              carrier rope 101 at the appropriate position.
                                                               In somewhat  greater  detail, a  length  measuring  device
                                                              210 measures the length L m along the main carrier rope 101
                                                              and provides the measured length L m to the control unit 200.
         Figure 17: Variable node spacing around an obstruction.
         line for illustrative purposes, and may have another shape
         in a real application. The path 10 passes a floating platform
         11 kept in position by four anchor lines 12. In figure 17 two
         anchor lines 12 extend past the path 10. The nodes 110 are
         to be deployed along the path 10 with a fixed distance x be-
         tween each node. Traditionally, single nodes without any in-
         terconnection would be deployed by an ROV. However, the
         present invention  allows variable node spacing along the   Figure 20: Schematic view of a node carrier.
         main carrier rope 101, such that different lengths L 1, L 2 and
                                                              In addition, a data source represented by boxes 220, 230 and
                                                              240 provide input to control unit 200 such that the desired
                                                              length can be calculated. The data source is schematically
                                                              illustrated by a survey planning source  220, a source for
                                                              environmental data 230 and a navigation system 240. The
                                                              survey planning source 220 illustrates any system or device
                                                              to obtain, store and provide relevant predetermined data, for
                                                              example geophysical requirements. The source 230 for envi-
                                                              ronmental data provides current data from the environment
                                                              in which the node is to be deployed. The environmental data
         Figure 18: Variable node spacing due to sea floor profile.  may comprise any data concerning  topology, obstructions

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