Various embodiments relate to a method and a seabed supported base structure for providing a shallow water drilling terminal, where a prefabricated floating seabed substructure is towed to site, ballasted to rest on the seabed and/or piled to the seabed forming a seabed foundation. The seabed supported base structure is provided with at least one cantilevered unit with openings for drilling of wells, projecting sideways out from the exterior side of a vertical wall, terminated above sea level. A prefabricated floating drilling module provided with an outrigger with sidewise movable drilling device is towed to the site, guided into the seabed substructure through an opening in the wall structure at the periphery of the base structure, ballasted and mated onto the base structure, whereupon wells are drilled from a drilling gear. Upon completed drilling and operation of the wells, the drilling unit is removed and substituted by a production unit.

A method for excavating a well cellar includes lowering an excavating apparatus having a cellar liner therein to a bottom of a body of water. The well cellar is excavated while contemporaneously lowering the cellar liner into the well cellar until a top of the cellar liner is substantially level with the bottom of the body of water. A pilot well is excavated below a bottom of the cellar. A well head support pipe is inserted into the pilot well. The bottom of the well cellar and a top of the cellar liner are covered.

A method for excavating a well cellar includes lowering an excavating apparatus having a cellar liner therein to a bottom of a body of water. The well cellar is excavated while contemporaneously lowering the cellar liner into the well cellar until a top of the cellar liner is substantially level with the bottom of the body of water. A pilot well is excavated below a bottom of the cellar. A well head support pipe is inserted into the pilot well. The bottom of the well cellar and a top of the cellar liner are covered.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.

An oil storage, loading and offloading system includes a submerged oil storage tank with multiple vertically placed flexible containers. The system directly connects to the topsides of an offshore oil production platform above water to assist oil loading and offloading operations. During loading, oil is pumped in and stored inside flexible containers, which are expanded to displace equivalent amount of water out of the oil storage tank; during offloading, oil is pumped out from flexible containers and the reduced volume of each contracted container is then filled in by the equivalent amount of water from the surroundings There is no physical contact between water and oil. The submerged tank on-bottom weight has a limited variation during the loading and offloading operations. This disclosed system can be utilized for fixed offshore platforms, especially for shallow water marginal field developments, and for deepwater floating platforms such as SPAR and semi-submersible (SEMI) structures.