Offshore petroleum discharge system

Abstract

A method and associated vessel for transferring liquids from offshore tankers to an onshore storage facility. The system utilizes a flexible pipe that is heavier than the water it displaces, such that the flexible pipe sinks to the sea floor even when empty. The high weight and relatively small profile of the flexible pipe avoids the need for anchoring the pipe to the sea floor. The flexible pipe has a bending radius of no greater than five feet, such that it can be wound onto spools onboard the vessel, and can be rapidly deployed, retrieved, and reused in another location. The vessel containing the spools of flexible pipe is dynamic positioning capable, and contains the equipment required to establish a position onshore to receive the liquid being transferred; means to deploy, retrieve, and repair the flexible pipe; and means to receive liquid from a tanker vessel and pump that liquid through the flexible pipe to the onshore storage facility.

1 . A method for transferring liquids from a ship offshore to an onshore storage facility, said method comprising the steps of; 
 identifying a beach receiving and transferring point;    locating a vessel offshore of the identified beach receiving and transferring point, the vessel containing spools of flexible pipe, the empty pipe being heavier than the water which it displaces, and a holding tank for the liquid to be transferred;    placing a pipeline termination unit at the identified beach receiving and transferring point;    connecting the pipeline termination unit to an onshore storage facility;    connecting the holding tank of the vessel offshore with the pipeline termination unit using the empty flexible pipe; and    pumping a liquid from the holding tank of the vessel offshore, through the flexible pipe, to the pipeline termination unit and from the pipeline termination unit to the onshore storage facility.    
   
   
       2 . A method as claimed in  claim 1  further comprising the step of maintaining the vessel in a constant position when the holding tank of the vessel is connected to the pipeline termination unit by the flexible pipe.  
   
   
       3 . A method as claimed in  claim 1  wherein the step of connecting the holding tank of the vessel offshore with the pipeline termination unit using the flexible pipe further comprises the steps of: 
 placing a winch adjacent to the pipeline termination unit at the identified beach receiving and transferring point;    connecting the winch to the end of the flexible pipe on the vessel, using a tow rope;    pulling the flexible pipe from the spools of flexible pipe on the vessel ashore to a point adjacent to the pipeline termination unit using the winch and tow rope; and    connecting the end of the flexible pipe pulled ashore to the pipeline termination unit.    
   
   
       4 . A method as claimed in  claim 1  wherein the step of identifying a beach receiving and transferring point further comprises evaluating the condition of the sea floor upon which the flexible pipe will be located.  
   
   
       5 . A method as claimed in  claim 4  wherein the step of evaluating the condition of the sea floor upon which the flexible pipe will be located utilizes a side scan sonar device.  
   
   
       6 . A method as claimed in  claim 1  further comprising the step of unloading the liquid to be transferred to the onshore storage facility from a tanker vessel to the vessel containing spools of flexible pipe.  
   
   
       7 . A method as claimed in  claim 6  wherein the step of unloading from a tanker vessel further comprises the steps of: 
 connecting the tanker vessel to the vessel containing spools of flexible pipe using floating hose; and    pumping the liquid from the tanker vessel into the holding tank on the vessel containing spools of flexible pipe.    
   
   
       8 . A method as claimed in  claim 6  wherein the step of unloading from a tanker vessel further comprises the step of maintaining the tanker in a constant position during the unloading process by utilizing a tender vessel to assist with the positioning of the tanker.  
   
   
       9 . A method as claimed in  claim 1  further comprising the steps of; 
 monitoring the back pressure on the pump pumping the liquid from the holding tank of the vessel offshore to the pipeline termination unit; and    regulating the back pressure on the pump pumping the liquid from the holding tank of the vessel offshore to the pipeline termination unit, using a pressure control valve and by-pass piping with by-pass control valve.    
   
   
       10 . A method as claimed in  claim 1  further comprising the step of clearing and testing the flexible pipe after it is in place on the sea floor by running a pipe pig through the flexible pipe.  
   
   
       11 . A method as claimed in  claim 1  wherein the step of connecting the holding tank of the vessel offshore with the pipeline termination unit utilizes up to four sections of flexible pipe, each section being up to two miles in length.  
   
   
       12 . A method as claimed in  claim 1  further comprising the step of controlling the buildup of static electricity in the flexible pipe by grounding a steel layer of the flexible pipe.  
   
   
       13 . A method as claimed in  claim 1  further comprising the step of maintaining the flexible pipe in position on the sea floor by utilizing a pipe of sufficient weight relative to sea water and having an outside diameter small enough to resist being moved by water currents.  
   
   
       14 . A method as claimed in  claim 13  wherein said step of maintaining the flexible pipe in position on the sea floor is accomplished by utilizing flexible pipe that weighs empty at least fifty percent more than the seawater displaced by the flexible pipe.  
   
   
       15 . A method as claimed in  claim 13  wherein said step of maintaining the flexible pipe in position on the sea floor is accomplished by utilizing flexible pipe that weighs empty at least fifty percent more than the seawater displaced by the flexible pipe and that has an outside diameter of less than nine inches.  
   
   
       16 . A method as claimed in  claim 1  further comprising the steps of; 
 disconnecting the flexible pipe from the pipeline termination unit when pumping is completed;    rewinding the flexible pipe onto the spools on the vessel offshore.    
   
   
       17 . A method as claimed in  claim 16  wherein said step of rewinding the flexible pipe onto the spools is facilitated by utilizing flexible pipe with a minimum bending radius of no greater than five feet.  
   
   
       18 . An equipped vessel for transferring liquids from tankers to an onshore storage facility, comprising: 
 an ocean-going hull form with a deck;    a holding tank within said hull form for holding liquid being transferred from a tanker to an onshore storage facility;    floating hose for connecting said holding tank with a tanker containing liquid to be transferred;    flexible pipe, said flexible pipe when empty being heavier than the water which it displaces, for conveying the liquid being transferred from said holding tank to an onshore storage facility;    one or more spools for containing said flexible pipe on said deck when said flexible pipe is not in use;    means for deploying said flexible pipe for connection with an onshore storage facility;    a transfer pump for pumping the liquid being transferred from said holding tank through said flexible pipe;    means to maintain position at sea;    a amphibious utility vessel; and    means to launch and retrieve said amphibious utility vessel.    
   
   
       19 . An equipped vessel as claimed in  claim 18  wherein said flexible pipe is of sufficient weight relative to sea water, and has an outside diameter small enough, to resist being moved by water currents.  
   
   
       20 . An equipped vessel as claimed in  claim 19  wherein said flexible pipe weighs empty at least fifty percent more than the seawater displaced by the flexible pipe.  
   
   
       21 . An equipped vessel as claimed in  claim 19  wherein said flexible pipe weighs empty at least fifty percent more than the seawater displaced by the flexible pipe and has an outside diameter of less than nine inches.  
   
   
       22 . An equipped vessel as claimed in  claim 19  wherein said flexible pipe weighs empty at least fifty percent more than the seawater displaced by the flexible pipe, has an outside diameter of less than nine inches, and has a minimum bending radius of no greater than five feet.  
   
   
       23 . An equipped vessel as claimed in  claim 18  wherein said means for recovering said flexible pipe after deployment comprises a winch.  
   
   
       24 . An equipped vessel as claimed in  claim 18  further comprising a spare transfer pump for pumping the liquid being transferred from said holding tank through said flexible pipe.  
   
   
       25 . An equipped vessel as claimed in  claim 18  wherein said means to maintain position at sea further comprises one or more tunnel thrusters and a swing-down 360 degree azimuthing thruster forward, and one or more tunnel thrusters and one or more controllable pitch wheels aft.  
   
   
       26 . An equipped vessel as claimed in  claim 18  wherein said one or more spools each contains two miles of said flexible pipe.  
   
   
       27 . An equipped vessel as claimed in  claim 18  further comprising five of said spools for containing said flexible pipe, with four of said spools each containing two miles of said flexible pipe, and the fifth spool being used to facilitate repair or transfer of said flexible pipe.  
   
   
       28 . An equipped vessel as claimed in  claim 18  w herein said means for deploying said flexible pipe for connection with an onshore storage facility comprises a tow rope and winch deployable onshore using said amphibious utility vessel.  
   
   
       29 . An equipped vessel as claimed in  claim 18  wherein a portion of said flexible pipe is armored to prevent damage when deployed across hazardous sea floor.  
   
   
       30 . An equipped vessel as claimed in  claim 18  further comprising a side scan sonar for evaluating the condition of the sea floor upon which said flexible pipe will be deployed.  
   
   
       31 . An equipped vessel as claimed in  claim 18  further comprising a pressure control valve and by-pass piping with by-pass control valve for regulating the back pressure on said transfer pump for pumping the liquid being transferred from said holding tank through said flexible pipe.  
   
   
       32 . An equipped vessel as claimed in  claim 18  further comprising means for clearing and testing said flexible pipe after it is deployed on the sea floor by running a pipe pig through said flexible pipe.  
   
   
       33 . An equipped vessel as claimed in  claim 18  wherein said flexible pipe includes a steel layer which can be grounded to discharge any buildup of static electricity.