Offshore Drilling

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Offshore Drilling
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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 1930s 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.

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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.

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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.

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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

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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.

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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

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

• http//www.youtube.com/watch?vK013XFkZNeA
• http//www.youtube.com/watch?vr-YCIQEwNR4feature
  related
• http//www.youtube.com/watch?vVi5EPleIOoQ

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Floaters
Semisubmersibles
Drill Ships
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Semisubmersibles

• http//www.youtube.com/watch?vLW1hbDC0mv8feature
  related
• Can be used anywhere especially in deepwater
• Rig is partially submerged to maintain stability
• Sturdy enough to operate in rough water

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Drill Ships

• http//www.youtube.com/watch?v0yZEon4x7Scfeature
  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.

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Offshore Drilling Platforms

• Rigid Platforms typical water depths of less
  than 1000
• http//www.youtube.com/watch?vJh2tHUYKYikfeature
  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.

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Steel Jacket Platform

• http//www.youtube.com/watch?vVjzYQBtjv9Ufeature
  related

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Concrete Gravity Platform
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Steel Caisson Platforms

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

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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?vqYvUArgZaSkfeature
  relmfu

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Questions

1. Explain how the first mobile offshore drilling
   unit was anchored to the sea floor.
2. What is MODU?
3. Explain the difference between a floater and a
   semi-submersible MODU
4. Which is better to use in rough sea conditions a
   semisubmersible or a drill ship? Why?
5. What are the advantages of using a drill ship?
6. What are the disadvantages of using a drill ship?
7. When would you drill from a fixed platform rather
   from an MODU?
8. What is a TLP?