Offshore production and storage facility and method of installing the same

Abstract

A concrete barge having oil storage tanks secured to its deck is towed to an oil production site where it is sunk to the sea bottom. Oil from an adjacent caisson supported production facility is temporarily stored in the tanks pending later transfer to an oil tanker. The caisson may be braced from the barge in hard-bottomed locations or may be guyed to the sea floor. Compartments in the concrete barge are filled with water as required for ballast and trim while the barged is being towed to location. The compartments are flooded with seawater to provide the sinking force to carry the barge and tank assembly to the sea bottom and hold the assembly on the sea bottom. Descent of the barge from the surface to the sea bottom is regulated by controlling the placement and pressure of air in the storage tanks. The submerged barge and tanks are filled with seawater to prevent hydrostatically induced crushing pressure differentials. Oil added to the tanks from the production facility displaces an equal volume of seawater from the tanks to ensure that the tanks remain constantly filled with a fluid. Oil is displaced from the tanks to the tanker by the introduction of seawater into the tank bottoms. The outlet from the tanks is taken from the tank tops so that the lighter oil is discharged into the sales lines as the heavier water occupies an increasing volume in the lower level of the tank. The tanks are coated in concrete to increase their collapse resistance.

Dependencies are inferred from the claim text.