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A deep-water floating offshore platform includes a buoyant hull having a substantially flat top, and substantially flat bottom, and a plurality of substantially flat sides. The hull further includes a tendon access shaft and a plurality of riser guide sleeves. The tendon access shaft extends below t

A deep-water floating offshore platform includes a buoyant hull having a substantially flat top, and substantially flat bottom, and a plurality of substantially flat sides. The hull further includes a tendon access shaft and a plurality of riser guide sleeves. The tendon access shaft extends below the bottom of the hull and includes a counterweight connected to the lower portion of the tendon access shaft to provide stability to the hull. The hull can be constructed from a cargo tank section of an existing oil tanker or through the use of new construction based on using the flat-plate design used in constructing cargo tank sections of oil tankers.

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1. An offshore platform, comprising:a buoyant hull having a top, a bottom, and a plurality of substantially flat sides extending between the top and the bottom to form a hull interior, the bottom of the hull including a first aperture positioned substantially in a central portion of the bottom of th

1. An offshore platform, comprising:a buoyant hull having a top, a bottom, and a plurality of substantially flat sides extending between the top and the bottom to form a hull interior, the bottom of the hull including a first aperture positioned substantially in a central portion of the bottom of the hull to thereby define a first tendon access shaft aperture, the top of the hull including a second aperture positioned substantially in a center portion of the top of the hull to thereby define a second tendon access shaft aperture, a conduit extending between the first tendon access shaft aperture and the second tendon access shaft aperture to thereby define a tendon access shaft, the bottom of the hull sealed about the tendon access shaft to prevent loss of buoyancy for the hull interior, and a tendon extending into the tendon access shaft to moor the hull to a site specific location.2. The platform of claim 1, wherein the buoyant hull further includes:a plurality of smaller apertures positioned in a surrounding relationship to the first tendon access shaft aperture to thereby define a plurality of bottom riser slot apertures;a corresponding plurality of smaller apertures positioned in a surrounding relationship to the second tendon access shaft aperture to thereby define a plurality of top riser slot apertures; anda plurality of riser guide sleeves positioned between the top riser slot apertures and the bottom riser slot apertures, the bottom of the hull sealed about the riser guide sleeves to prevent loss of buoyancy for the hull interior.3. The platform of claim 2, further comprising a counterweight connected to the lower portion of the tendon access shaft and having a plurality of riser conductor slots extending therethrough to provide lateral stability to a plurality of risers extending through the plurality of riser conductor slots.4. The platform of claim 1, further comprising a plurality of water tight compartments connected to the bottom of the buoyant hull to provide adequate buoyancy and stability in the event of watertight compartment flooding.5. The platform of claim 1, further comprising:production equipment positioned within the hull interior to enhance stability of the hull and to process well fluid; anda conduit extending from the production equipment to a subsea well facility.6. An offshore platform, comprising:a buoyant hull having a substantially flat top, and substantially flat bottom, and a plurality of substantially flat sides, the bottom of the hull including a first aperture positioned substantially in a central portion of the bottom of the hull to thereby define a first tendon access shaft aperture, a plurality of smaller apertures positioned in a surrounding relationship to the first tendon access shaft aperture to thereby define a plurality of bottom riser slot apertures, the top of the hull including a second aperture positioned substantially in a center portion of the top of the hull to thereby define a second tendon access shaft aperture, and a corresponding plurality of smaller apertures positioned in a surrounding relationship to the second tendon access shaft aperture to thereby define a plurality of top riser slot apertures, the second tendon access shaft aperture positioned in a matching actual relationship with the first tendon access shaft, and the top riser slot apertures positioned in a matching axial relationship with the bottom riser slot apertures;a conduit having an upper portion and a lower portion and extending from below the bottom of the hull and through the first and second tendon access shaft apertures to thereby define a tendon access shaft, the upper portion of the tendon access shaft cooperatively engaged with the hull to provide access to a tendon;a counterweight connected to the lower portion of the tendon access shaft and having a plurality of riser conductor slots to provide lateral stability to a plurality of risers; andwherein the counterweight has a plurality of riser conductor slots connected to a plurality of risers to support a vertical load of the risers and provide additional vertical stability to the offshore platform and the risers.7. An offshore platform, comprising:a buoyant hull having a substantially flat top, and substantially flat bottom, and a plurality of substantially flat sides the bottom of the hull including a first aperture positioned substantially in a central portion of the bottom of the hull to thereby define a first tendon access shaft aperture, a plurality of smaller apertures positioned in a surrounding relationship to the first tendon access shaft aperture to thereby define a plurality of bottom riser slot apertures, the top of the hull including a second aperture positioned substantially in a center portion of the top of the hull to thereby define a second tendon access shaft aperture and a corresponding plurality of smaller apertures positioned in a surrounding relationship to the second tendon access shaft aperture to thereby define a plurality of top riser slot apertures, the second tendon access shaft aperture positioned in a matching actual relationship with the first tendon access shaft, and the top riser slot apertures positioned in a matching axial relationship with the bottom riser slot apertures;a conduit having an upper portion and a lower portion and extending from below the bottom of the hull and through the first and second tendon access shaft apertures to thereby define a tendon access shaft, the upper portion of the tendon access shaft cooperatively engaged with the hull to provide access to a tendon;a counterweight connected to the lower portion of the tendon access shaft and having a plurality of riser conductor slots to provide lateral stability to a plurality of risers; andwherein the tendon access shaft further includes a tendon access shaft extension to extend the distance of the counterweight from the bottom of the hull to provide additional stability to the platform such that the platform floats vertically without the need of additional subsea support.8. The platform of claim 7, wherein the tendon access shaft extension includes a tendon connector having a connection aperture for connecting a single tendon.9. The platform of claim 7, wherein the tendon access shaft extension includes a tendon connector having a plurality of tendon connection apertures for connecting a plurality of tendons.10. A method of constructing an offshore platform, comprising the steps of:removing an intact midsection oil cargo tank from an existing tanker;removing an inner portion of the removed oil cargo tank section, separating the oil cargo tank section into a plurality of separate sub-sections; andrejoining the separate subsections to form a buoyant hull having a top, a bottom, and a plurality of flat sides, the hull having a width and length that are substantially the same.11. A method of claim 10, further comprising the step of removing and rotating bulkheads forming sides of the hull such that bulkhead stiffeners are on the inside of said hull.12. A method of claim 10, further comprising the steps of:forming an aperture in the bottom and an aperture in the top aligned with the aperture in the bottom; andsecuring a conduit sealingly between the apertures.13. A method of claim 10, further comprising the steps of:forming a plurality of first riser slot apertures in a central section of the bottom of the new hull and forming a plurality of second riser slot apertures in the top of the new hull axially positioned in a matching relationship above the plurality of first riser slot apertures and installing a corresponding plurality of riser guide sleeves between the first and second riser slot apertures; andforming a first tendon access shaft aperture in a central section of the bottom of the new hull and forming a second tendon access shaft aperture in the top of the new hull axially positioned in a matching relationship above the first tendon access shaft aperture and installing a tendon access shaft having a tendon access shaft extension between the first and second tendon access shaft apertures with the tendon access shaft extension extending below the bottom of the new hull.14. The method of claim 13, further comprising the step of attaching a counterweight to a lower end of the tendon access shaft.15. The method of claim 10, further comprising the step of removing corners of the hull and adding side panels at the corners to form an at least eight-sided hull.16. A method of constructing an offshore platform, comprising the steps of:forming a buoyant hull having a top, a bottom, and a plurality of substantially flat sides extending between the top and the bottom to form a hull interior;forming a first tendon access shaft aperture in a central section of the bottom of the hull;forming a second tendon access shaft aperture in the top of the hull axially positioned in a matching relationship above the first tendon access shaft aperture;installing a tendon access shaft having a tendon access shaft extension between the first and second tendon access shaft apertures with the tendon access shaft extension extending below the bottom of the hull;sealing the bottom of the hull about the tendon access shaft to prevent loss of buoyancy for the hull interior; andconnecting a tendon to the tendon access shaft to moor the hull to a site specific location.17. The method of claim 16, further comprising the steps of:forming a plurality of first riser slot apertures in a central section of the bottom of the hull;forming a plurality of second riser slot apertures in the top of the hull axially positioned in a matching relationship above the plurality of first riser slot apertures;installing a corresponding plurality of riser guide sleeves between the first and second riser slot apertures; andsealing the bottom of the hull about the riser guide sleeves to prevent loss of buoyancy for the hull interior.18. The method of claim 17, further comprising the step of:attaching to a lower end of the tendon access shaft a counterweight having a plurality of riser conductor slots to provide lateral stability to a plurality of risers extending from the buoyant hull.19. A method of forming and using an offshore platform, comprising the steps of:cutting a tank section or sections from a tanker to define a hull;installing production equipment placed within an interior of the hull to enhance stability of the hull;mooring the hull;connecting a conduit from a subsea well facility to the production equipment;flowing well fluid to the production equipment and processing the well fluid; and thendischarging the well fluid from the production equipment.20. The method of claim 19, further comprising the steps of:installing in the hull a tendon access shaft having a tendon access shaft extension extending below a bottom of the hull; andconnecting a tendon to the tendon access shaft extension to provide mooring for the hull.21. The method of claim 20, further comprising the step of:attaching to a lower end of the tendon access shaft a counterweight to provide additional stability to the offshore platform so that the offshore platform floats substantially vertically without the need of additional subsea mooring support.22. The method of claim 20, further comprising the step of:attaching to the tendon access shaft a tendon connector having a connection aperture for connecting a tendon to moor the hull.23. The method of claim 19, further comprising the step of:removing corners of the hull and adding side panels at the corners to form an at least eight-sided hull.24. A method of constructing an offshore platform, comprising the steps of:cutting and removing one or more intact midsection oil cargo tanks from an existing tanker to form a buoyant hull having a top, a bottom, a plurality of substantially flat sides, and a plurality of watertight bulkheads; andadding additional watertight bulkheads to the buoyant hull to increase a number of watertight compartments.