Offshore well apparatus with a protected production system

Abstract

An offshore well apparatus so constructed and arranged to minimize chances of pollution of sea water by production fluids which may be released as a result of damage to the well apparatus resulting from natural causes, such as, action of masses of ice at the seabed, earth slides in the seabed formation, and breakage of the production system above the seabed. The offshore well apparatus includes a platform means at the sea surface and a well template means on the seabed formation beneath the platform means, a well casing means supported from the template means and extending into a well hole, riser pipe means extending into the well casing means and having a riser connecting means at its lower end connected to a production fluid control means located at a selected depth within the well casing means, and fluid pressure actuating means for the production fluid control means including means for automatically shutting off production flow at a selected depth below the seabed. The depth location of the production control means is dependent upon the geological characteristics of the seabed formation and is normally located below the action of ice masses on the seabed and below known slippage planes in the geological formation of the seabed. Riser connecting means to the production control means is releasable in the event weather and ocean conditions are severe enough to cause danger to the platform means if the platform is held in normal operating position above the well hole, said riser pipe means having its lower end positioned in the upper portion of the well casing means. An offshore well apparatus including multiple risers for producing a plurality of well holes. A platform structure and well template structure arrange to facilitate a multiple riser system.