Anchoring method and apparatus

Abstract

The present invention relates to apparatus and a method of embedding a plate anchor. The method comprises providing a plurality of embedment modules each of which is suitable for embedding a plate anchor within a different type of soil. The method comprises determining the type of soil of a seabed at a target site and selecting an embedment module based on the type of soil at the target site. The embedment module is removably mounted within a modular follower assembly. The modular follower assembly is deployed from a vessel and the embedment module is actuated to drive the plate anchor into the seabed. The modular follower assembly is then retrieved to the vessel. The modular follower assembly is reconfigured to provide the modular follower assembly with different embedment modules for a subsequent deployment and to embed further plate anchors within different soil types.

1 . A method of embedding a plate anchor, the method comprising:
 providing a plurality of embedment modules each of which is suitable for embedding a plate anchor within a different type of soil;   determining the type of soil of a seabed at a target site;   selecting an embedment module based on the type of soil at the target site;   removably mounting the embedment module within a modular follower assembly;   deploying the modular follower assembly from a vessel;   actuating the embedment module to drive the plate anchor into the seabed;   retrieving the modular follower assembly to the vessel and reconfiguring the modular follower assembly to provide the modular follower assembly with different embedment modules for a subsequent deployment.   
     
     
         2 . A method of embedding a plate anchor according to  claim 1  in which the method comprises securing a first plate anchor within the modular follower assembly and embedding the first plate anchor at a first target site, retrieving the modular follower assembly and reconfiguring the embedment modules within the modular follower assembly, securing a further plate anchor within the modular follower assembly and embedding the further plate anchor at a further target site. 
     
     
         3 . A method of embedding a plate anchor according to  claim 2  in which the method comprises embedding a plurality of plate anchors to provide tethering points for a floating offshore wind turbine or other offshore device. 
     
     
         4 . A method of embedding a plate anchor according to  claim 1  in which the method comprises identifying layers and/or strata within the seabed and mounting one or more embedment modules to the follower assembly to penetrate the identified layers and/or strata within the seabed. 
     
     
         5 . A method of embedding a plate anchor according to  claim 1  in which the method comprises mounting a combination of embedment modules to the modular follower assembly to penetrate through a number of layers/strata of the seabed. 
     
     
         6 . A method of embedding a plate anchor according to  claim 1  in which the method comprises selecting and mounting one or more embedment modules from the following:
 a vibro hammer embedment module; 
 an impact hammer embedment module; 
 a suction embedment module; and 
 a jetting module. 
 
     
     
         7 . A method of embedding a plate anchor according to  claim 1  in which the method comprises providing a clamp module for the modular follower assembly and removably mounting the clamp module within the modular follower assembly and wherein the method comprises clamping the plate anchor between opposing jaws of the clamp module and subsequently releasing the jaws from the plate anchor once the plate anchor is located in the desired position/depth within the seabed. 
     
     
         8 . A method of embedding a plate anchor according to  claim 1  in which the method comprises providing a power pack module for the modular follower assembly and removably mounting the power pack module to the modular follower assembly wherein the power pack module supplies hydraulic or electric power to at least one embedment module. 
     
     
         9 . A method of embedding a plate anchor according to  claim 1  in which the method comprises adjusting a length of a housing of the modular follower assembly. 
     
     
         10 . A method of embedding a plate anchor according to  claim 9  in which the method comprises providing a number of housing sections which can be removably incorporated into or removed from the tubular housing of the modular follower assembly. 
     
     
         11 . A method of embedding a plate anchor according to  claim 10  in which the method comprises adjusting a longitudinal length of the tubular housing following the retrieval of the modular follower assembly from a first deployment and prior to a later deployment wherein the method comprises providing a number of sections which provide a variety of sections having different longitudinal lengths. 
     
     
         12 . A method of embedding a plate anchor according to  claim 1  in which the method comprises tethering a floating offshore wind turbine or other offshore device to the seabed and connecting a plurality of mooring lines extending from the floating offshore wind turbine or other offshore device to a number of embedded plate anchors. 
     
     
         13 . Plate anchor embedment apparatus comprising a modular follower assembly having a housing, the modular follower assembly extending from a first longitudinal end to a second longitudinal end, the follower assembly comprising:
 a plate anchor engagement module;   a lifting and lowering line securement mechanism;   a first mounting mechanism for removably mounting a first embedment module thereto;   a second mounting mechanism for removable mounting a second embedment module thereto;   a power supply module for supplying power to at least one embedment module;   wherein the follower assembly is reconfigurable on a vessel between subsea deployments to enable embedment modules to be changed for a subsequent deployment and to enable embedment modules mounted to the follower assembly to be removed therefrom or mounted thereto.   
     
     
         14 . Plate anchor embedment apparatus according to  claim 13  in which the first embedment module generates embedment forces for use in efficiently embedding the plate anchor in a first layer/stratum and the second embedment module generates embedment forces for use in efficiently embedding the plate anchor in a second layer/stratum. 
     
     
         15 . Plate anchor embedment apparatus according to  claim 13  in which a combination of embedment modules of the modular follower assembly is arranged to penetrate the plate anchor through a number of consecutive layers/strata of the seabed. 
     
     
         16 . Plate anchor embedment apparatus according to  claim 13  in which the first and second embedment modules comprise one of the following:
 a vibro hammer embedment module; 
 an impact hammer embedment module; 
 a suction embedment module; and 
 a jetting module. 
 
     
     
         17 . Plate anchor embedment apparatus according to  claim 13  comprising a clamp module which is removably mountable within the modular follower assembly and wherein the clamp module comprises a clamping mechanism comprising opposing jaws for clamping a plate anchor therebetween. 
     
     
         18 . Plate anchor embedment apparatus according to  claim 13  in which the power supply module comprises a power pack module removably mountable to the modular follower assembly in which the power pack module is arranged to supply hydraulic and/or electric power. 
     
     
         19 . Plate anchor embedment apparatus according to  claim 13  in which the modular follower assembly comprises a housing having an adjustable longitudinal length. 
     
     
         20 . Plate anchor embedment apparatus according to  claim 19  in which the plate anchor embedment apparatus comprises a number of housing sections which can be removably incorporated into or removed from the housing of the modular follower assembly and wherein the sections provide a variety of sections having different longitudinal lengths.