Geophysical Logging and Analysis

Prof. Youngseuk KeehmEmail: keehm@kongju.ac.kr

Geoenvironmental Sciences

Chap. 4: Oil & Gas Platforms

Geoenvironmental Sciences

Offshore Rigs

Jack-up Rigs Semi-submergible Rigs Drilling ships Fixed Platforms Seastar Platforms Floating Production

Systems Tension Leg Platforms Subsea System Spar Platforms

Geoenvironmental Sciences

Jack-up Rigs

- Stable at relatively shallow depth- Possible water depth is determined

by the length of legs

- Movable- Three or four legs- Can adjust height

Geoenvironmental Sciences

Semi-submergible Rigs

- Widely used in deep water- Can do ballasting- Can handle water-level

fluctuation

- Can handle deep water by using anchors

- Can do the job without anchors if DPS (Dynamic Positioning System) is used

Geoenvironmental Sciences

Drilling Ships

- Most widely used in exploration

- Have “moon pool” (hole) in the center of the ship

- Derrick is positioned on the moon pool

- DPS is essential

Geoenvironmental Sciences

Fixed Platforms

- Most widely used- Very stable since legs are fixed on

the sea floor- Only possible at shallow depth

- Concrete structures are used in cold regions, such as North Sea or Sakhalin

- These structures can be used as storage tanks

Geoenvironmental Sciences

Seastar Platforms

- Small-scale TLP (tension leg platform)- Used at water depth smaller tha

3,500 feet- Used for small oil/gas reservoirs

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Floating Production Systems

- Fixed by mooring anchors

- FPSO (Floating Production Storage Offloading)

- FPU (Floating Production Unit) is useful scattered reservoirs

Geoenvironmental Sciences

Tension Leg Platforms

- Large version of Seastar platform- Large horizontal movement (~ 20 ft),

but very limited vertical movement- Suitable for deep (>7,000ft)

reservoris

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Subsea Systems

- Fixed well heads on the sea floor- Oil production using Christmas

Tree- Produced oil is carried by

underwater pipelines or floating production systems

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Spar Platforms

- Platform is on cylinder structure (spar)- Fixed by cables - Can handle big storms (hurricane)- The first one was built in 1996 at GOM (diameter: 70ft, length: 770ft,

water depth: 1930ft)

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Jack-up Rigs

Cecil Forbes

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Semi-submersible Rigs

Sonat’sGeorge Washington

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Drillship

Zapata’s Trader

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TLP

Shell’s Auger TLP

Geoenvironmental Sciences

Petronius

World’s tallest offshore structure1,754’ water depth, 2,001’ from sea bottom