Method and apparatus for management of fluids in an underwater storage tank

Abstract

Apparatus and method for managing water or other ballast fluid in an underwater storage tank ( 14 ), used for storing fluids such as oil or CO2, where a dis-connectable inflatable bag ( 16 ) is coupled to the underwater storage tank to capture displaced ballast fluid from the underwater storage tank. A supply line ( 36 ) between the bag and tank provides a closed loop system. Embodiments are shown in which the tank is initially filled with fresh water and multiple dis-connectable inflatable bags are used.

1 . An apparatus for managing a first fluid in an underwater storage tank, used for storing a second fluid, comprising a dis-connectable inflatable bag coupled to the underwater storage tank to capture displaced first fluid from the underwater storage tank. 
     
     
         2 . The apparatus according to  claim 1  wherein the dis-connectable inflatable bag has a first port for the entry and exit of the first fluid, to and from the underwater storage tank. 
     
     
         3 . The apparatus according to  claim 2  wherein the dis-connectable inflatable bag has a second port, the second port being closed when the dis-connectable inflatable bag is attached to the underwater storage tank. 
     
     
         4 . The apparatus according to  claim 2  wherein the dis-connectable inflatable bag has a second port, the second port being open when the dis-connectable inflatable bag is attached to the underwater storage tank to allow fluids lighter than the first fluid to rise to a holding vessel. 
     
     
         5 . The apparatus according to  claim 1  wherein the dis-connectable inflatable bag is arranged adjacent the underwater storage tank. 
     
     
         6 . The apparatus according to  claim 5  wherein there are a plurality of dis-connectable inflatable bags arranged adjacent the underwater storage tank. 
     
     
         7 . The apparatus according to  claim 2  wherein the apparatus further comprises a supply line between the first port and a first fluid exit port at the bottom of the underwater storage tank. 
     
     
         8 . The apparatus according to  claim 7  wherein the supply line includes one or more valves. 
     
     
         9 . The apparatus according to  claim 5  wherein the supply line includes a branch line to divert the first fluid to production facilities associated with the underwater storage tank. 
     
     
         10 . The apparatus according to  claim 7  wherein the supply line includes an intermediate tank, the intermediate tank being used to collect and separate the second fluid or sludge which may have entered the supply line as the first fluid from the underwater storage tank is offloaded. 
     
     
         11 . The apparatus according to  claim 10  wherein the intermediate tank has at least one take-off port to direct the separated second fluid/sludge back to the underwater storage tank. 
     
     
         12 . The apparatus according to  claim 11  wherein there are two take-off ports, arranged at a top and a bottom of the intermediate tank, with the supply line arranged to draw from a point between the top and the bottom of the intermediate tank. 
     
     
         13 . The apparatus according to  claim 1  wherein there is a holding tank to capture any fluids lighter than the first fluid which have entered the dis-connectable inflatable bags, using the natural buoyancy of those compounds. 
     
     
         14 . A method for managing a first fluid in an underwater storage tank, used for storing a second fluid, comprising capturing the first fluid displaced from the underwater storage tank in a dis-connectable inflatable bag. 
     
     
         15 . The method according to  claim 14  wherein the first fluid is water and the second fluid is oil to provide a method for managing the water in an underwater oil storage tank, comprising capturing the water displaced from the underwater oil storage tank in a dis-connectable inflatable bag. 
     
     
         16 . The method according to  claim 15  including the steps of:
 (a) connecting a supply line between a single port of the dis-connectable inflatable bag and a water exit port at the bottom of the underwater oil storage tank; 
 (b) with the dis-connectable inflatable bag deflated, initially filling the underwater oil storage tank with water; 
 (c) loading oil into the underwater oil storage tank to displace the water into the supply line; 
 (d) passing the displaced water into the dis-connectable inflatable bag and storing the displaced water in the dis-connectable inflatable bag; and 
 (e) discharging oil from the underwater oil storage tank for export while allowing the displaced water to return to the underwater oil storage tank from the dis-connectable inflatable bag. 
 
     
     
         17 . The method according to  claim 16  wherein at step (a) a plurality of bags are attached to a branched connection on the supply line, with each branch containing a valve and the method includes the step of isolating one or more dis-connectable inflatable bags. 
     
     
         18 . (canceled) 
     
     
         19 . The method according to  claim 16  wherein at step (d) the underwater oil storage tank is initially filled with fresh water. 
     
     
         20 . (canceled) 
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . The method according to  claim 16  wherein the method includes the step of discharging water from the underwater oil storage tank through an oil export line. 
     
     
         27 . The method according to  claim 14  wherein the first fluid is water and the second fluid is liquefied CO2 to provide a method for managing the water in an underwater CO2 storage tank, comprising capturing the water displaced from the underwater CO2 storage tank in a dis-connectable inflatable bag.