Presentation on offshore platform design
07/30/2003 OFFSHORE PLATFORM DESIGN WELCOME WELCOME PRESENTATION ON PRESENTATION ON OFFSHORE PLATFORM DESIGN OFFSHORE PLATFORM DESIGN 07/30/2003 OFFSHORE PLATFORM DESIGN Welcome aboard exciting world of Offshore platforms design. In Next 45 Welcome aboard exciting world of Offshore platforms design. In Next 45 minutes we will take you to educational trip of offshore platforms with minutes we will take you to educational trip of offshore platforms with breathtaking views and path breaking engineering accomplishments. breathtaking views and path breaking engineering accomplishments. 07/30/2003 OFFSHORE PLATFORM DESIGN OVERVIEW OVERVIEW Offshore platforms are used for Offshore platforms are used for exploration of Oil and Gas from exploration of Oil and Gas from under Seabed and processing. under Seabed and processing. The First Offshore platform was The First Offshore platform was installed in 1947 off the coast of installed in 1947 off the coast of Louisiana in 6M depth of water. Louisiana in 6M depth of water. Today there are over 7,000 Today there are over 7,000 Offshore platforms around the Offshore platforms around the world in water depths up to world in water depths up to 1,850M 1,850M 07/30/2003 OFFSHORE PLATFORM DESIGN OVERVIEW OVERVIEW Platform size depends on facilities to be Platform size depends on facilities to be installed on top side eg. Oil rig, living installed on top side eg. Oil rig, living quarters, Helipad etc. quarters, Helipad etc. Classification of water depths: Classification of water depths: – < 350 M- Shallow water < 350 M- Shallow water – < 1500 M - Deep water < 1500 M - Deep water – > 1500 M- Ultra deep water > 1500 M- Ultra deep water – US Mineral Management Service US Mineral Management Service (MMS) classifies water depths greater (MMS) classifies water depths greater than 1,300 ft as deepwater, and greater than 1,300 ft as deepwater, and greater than 5,000 ft as ultra-deepwater. than 5,000 ft as ultra-deepwater. 07/30/2003 OFFSHORE PLATFORM DESIGN OVERVIEW OVERVIEW Offshore platforms can broadly categorized in two types Offshore platforms can broadly categorized in two types Fixed structures that extend to the Seabed. Fixed structures that extend to the Seabed. Steel Jacket Steel Jacket Concrete gravity Structure Concrete gravity Structure Compliant Tower Compliant Tower 07/30/2003 OFFSHORE PLATFORM DESIGN OVERVIEW OVERVIEW Structures that float near the water surface- Recent development Structures that float near the water surface- Recent development Tension Leg platforms Tension Leg platforms Semi Submersible Semi Submersible Spar Spar Ship shaped vessel (FPSO) Ship shaped vessel (FPSO) OFFSHORE PLATFORM DESIGN 07/30/2003 TYPE OF PLATFORMS (FIXED) TYPE OF PLATFORMS (FIXED) JACKETED PLATFORM JACKETED PLATFORM – Space framed structure with tubular Space framed structure with tubular members supported on piled members supported on piled foundations. foundations. – Used for moderate water depths up to Used for moderate water depths up to 400 M. 400 M. – Jackets provides protective layer Jackets provides protective layer around the pipes. around the pipes. – Typical offshore structure will have a Typical offshore structure will have a deck structure containing a Main Deck, deck structure containing a Main Deck, a Cellar Deck, and a Helideck. a Cellar Deck, and a Helideck. – The deck structure is supported by deck The deck structure is supported by deck legs connected to the top of the piles. legs connected to the top of the piles. The piles extend from above the Mean The piles extend from above the Mean Low Water through the seabed and into Low Water through the seabed and into the soil. the soil. OFFSHORE PLATFORM DESIGN 07/30/2003 TYPE OF PLATFORMS (FIXED) TYPE OF PLATFORMS (FIXED) JACKETED PLATFORM (Cont.) JACKETED PLATFORM (Cont.) – Underwater, the piles are contained Underwater, the piles are contained inside the legs of a “jacket” structure inside the legs of a “jacket” structure which serves as bracing for the piles which serves as bracing for the piles against lateral loads. against lateral loads. – The jacket also serves as a template The jacket also serves as a template for the initial driving of the piles. for the initial driving of the piles. (The piles are driven through the (The piles are driven through the inside of the legs of the jacket inside of the legs of the jacket structure). structure). – Natural period (usually 2.5 second) Natural period (usually 2.5 second) is kept below wave period (14 to 20 is kept below wave period (14 to 20 seconds) to avoid amplification of seconds) to avoid amplification of wave loads. wave loads. – 95% of offshore platforms around 95% of offshore platforms around the world are Jacket supported. the world are Jacket supported. OFFSHORE PLATFORM DESIGN 07/30/2003 TYPE OF PLATFORMS (FIXED) TYPE OF PLATFORMS (FIXED) COMPLIANT TOWER COMPLIANT TOWER – Narrow, flexible framed structures Narrow, flexible framed structures supported by piled foundations. supported by piled foundations. – Has no oil storage capacity. Production is Has no oil storage capacity. Production is through tensioned rigid risers and export through tensioned rigid risers and export by flexible or catenary steel pipe. by flexible or catenary steel pipe. – Undergo large lateral deflections (up to Undergo large lateral deflections (up to 10 ft) under wave loading. Used for 10 ft) under wave loading. Used for moderate water depths up to 600 M. moderate water depths up to 600 M. – Natural period (usually 30 second) is kept Natural period (usually 30 second) is kept above wave period (14 to 20 seconds) to above wave period (14 to 20 seconds) to avoid amplification of wave loads. avoid amplification of wave loads. OFFSHORE PLATFORM DESIGN 07/30/2003 TYPE OF PLATFORMS (FIXED) TYPE OF PLATFORMS (FIXED) CONCRETE GRAVITY CONCRETE GRAVITY STRUCTURES: STRUCTURES: – Fixed-bottom structures made from concrete Fixed-bottom structures made from concrete – Heavy and remain in place on the seabed Heavy and remain in place on the seabed without the need for piles without the need for piles – Used for moderate water depths up to 300 M. Used for moderate water depths up to 300 M. – Part construction is made in a dry dock Part construction is made in a dry dock adjacent to the sea. The structure is built from adjacent to the sea. The structure is built from bottom up, like onshore structure. bottom up, like onshore structure. – At a certain point , dock is flooded and the At a certain point , dock is flooded and the partially built structure floats. It is towed to partially built structure floats. It is towed to deeper sheltered water where remaining deeper sheltered water where remaining construction is completed. construction is completed. – After towing to field, base is filled with water After towing to field, base is filled with water to sink it on the seabed. to sink it on the seabed. – Advantage- Less maintenance Advantage- Less maintenance