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Offshore Drilling

Offshore Drilling. History of Offshore Drilling. First well drilled offshore : 1897 off the coast of southern California Wooden pier extended 300’ into the Pacific Ocean Early Barges and Platforms:

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Offshore Drilling

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  1. Offshore Drilling

  2. History of Offshore Drilling • First well drilled offshore : • 1897 off the coast of southern California • Wooden pier extended 300’ into the Pacific Ocean • Early Barges and Platforms: • Seismic surveys in the 1930’s showed hydrocarbon formations in the marshlands, bayous and shallow bays next to the Gulf of Mexico. • Oil companies dredged a 4’-8’ deep channel in marshes and bays then towed in a barge • They sunk the barge and secured it using wooden pilings, then erected a rig on the deck above the waterline.

  3. History of Offshore Drilling • Wooden Platforms • Companies built wooden platforms on timber piles and erected rigs on top of the platforms • Barges brought supplies out to the platform, or trestles were built from the shore to the platform creating a road for trucks to use.

  4. History of Offshore Drilling • The first steel platform was built in 1947 and installed in the Gulf of Mexico at a water depth of 20’. • Operators anchored surplus barges and tenders to the sides of the platform. • Barges/tenders carried supplies, living quarters, and circulating equipment. • These platforms worked in water depths of less than 60’, and moved from well to well.

  5. History of Offshore Drilling • Mobile Offshore Drilling Units • 1948 Naval architects and engineers designed a system consisting of a barge with several steel beams, or posts attached to its deck • Drilling Equipment was installed on the deck • When the rig arrived on location the lower part (barge hull) was allowed to fill with water in order to sink the rig to the sea floor • The deck extended to the surface due to the posts attached to the barge • Called: “Posted Barge Rigs”

  6. Offshore Drilling Today • Moving further and deeper out to sea • Justification to drill at greater depths • Typical reserves needed for offshore/deepwater drilling is 300 million barrels to offset cost and produce desired revenues. • Drilling rigs differ for exploration and development wells. • Exploratory: typically have mobile offshore drilling units • Development Wells: typically use fixed platforms with production and well maintenance facilities • New technologies are allowing the use of non-fixed units for development purposes.

  7. Mobile Offshore Drilling Units • Typically classified in two categories: • Submersibles • Floaters • Submersibles: Supported by the sea floor • Posted Barges • Bottle-type submersibles • Arctic submersibles • Jackups • Floaters: Float on or just below the surface of the water • Bottle-type Semisubmersibles • Column-Stabilized Semisubmersibles • Drill Ships

  8. Submersibles Bottle Type Submersible Jackup Arctic Submersible (Concrete Island Drilling System)

  9. Jackups • http://www.youtube.com/watch?v=K013XFkZNeA • http://www.youtube.com/watch?v=r-YCIQEwNR4&feature=related • http://www.youtube.com/watch?v=Vi5EPleIOoQ

  10. Floaters Semisubmersibles Drill Ships

  11. Semisubmersibles • http://www.youtube.com/watch?v=LW1hbDC0mv8&feature=related • Can be used anywhere especially in deepwater • Rig is partially submerged to maintain stability • Sturdy enough to operate in rough water

  12. Drill Ships • http://www.youtube.com/watch?v=0yZEon4x7Sc&feature=related • Faster to move than submersibles • Have very deep operating depths • Station themselves with: • Anchors • Dynamic positioning • Are more susceptible to weather conditions and wave dynamics.

  13. Offshore Drilling Platforms • Rigid Platforms: typical water depths of less than 1000’ • http://www.youtube.com/watch?v=Jh2tHUYKYik&feature=related • Steel Jacket Platform • Tubular steel members and piles driven deep into the sea floor support the rig floor and all supporting, drilling equipment and personnel. • Concrete Gravity Platform • Built from steel reinforced concrete caissons (columns) support the structure above and because of weight do not require anchoring to the sea floor.

  14. Steel Jacket Platform • http://www.youtube.com/watch?v=VjzYQBtjv9U&feature=related

  15. Concrete Gravity Platform

  16. Steel Caisson Platforms • Designed for arctic conditions, drilling is completed through the legs of the rig in order to protect it from moving ice.

  17. Compliant Platforms • Tension Leg Platforms (TLP) • Topside resembles a semi submersible, but the hull is attached to the seafloor via steel tubes called tendons • New designs can drill in waters 4000’ deep and more • Guyed Tower Platforms (Spar) • Large pontoons similar to semisubmersible • Connected to seabed floor via jack-up legs, tension legs or mooring systems • http://www.youtube.com/watch?v=qYvUArgZaSk&feature=relmfu

  18. Questions • Explain how the first mobile offshore drilling unit was anchored to the sea floor. • What is MODU? • Explain the difference between a “floater” and a “semi-submersible” MODU • Which is better to use in rough sea conditions a semisubmersible or a drill ship? Why? • What are the advantages of using a drill ship? • What are the disadvantages of using a drill ship? • When would you drill from a fixed platform rather from an MODU? • What is a TLP?

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