PETE 406

Lesson 8

Offshore Drilling

Content

• Inland barges (submersible)

• Jackup rigs– Wildcats– Shallow water templates– Cantilevered over platform

• Platform rigs

• Floaters - semi’s and drillships

Inland barge

• Used in swamps, bays, inland water, shallow offshore.

• Floated and towed to location

• On location these rigs are submerged

• Well is drilled

• Personnel and supplies are brought in by boat.

Jackup rigs

Noble Drilling’s

Cecil Forbes

A Jack-Up Rig

Jackup rigs

• Independent legs or mat supported

• Some are self propelled to location, but most moved by tugs

• On location survey boat surveys location

Jackup rigs

• Legs jacked down to sea floor

• Hull picked up above water

• Rig “pre-loaded”

• Seawater pumped out

• Jacked up to working “air gap”

• Well drilled

Jackup rigs

• Used for both wildcat and development

• Shallow water up to 350-400’ WD

• Derrick may be fixed or cantilevered

Platform rigs

• Tendered

Platform Rig

• Self contained

Platform Rig

• Operations similar to land except:– Limited storage space– Crew lives on location– Cementing operations simpler

Floating rigs

• Semi-submersible

• Drill ships

Sonat’s George Washington

A Semi-Submersible

Rig

Zapata’s Trader

A Drillship

Semi-submersible

Marine Riser

Subsea BOP stack

Drilling from Floating Vessel

• Rig move– Hole opener pulled

from storage and prepared for use

– Structural casing is measured and brought on deck

– Inspect and test riser and BOP system

Drilling from Floating Vessel

– Water depth at new location verified– Tide tables obtained– Choke manifold inspected and tested

• Site surveyed and marked with buoys

Drilling from Floating Vessel

• Anchor boats on location

• Heading adjusted and anchor setting begins

Drilling from Floating Vessel

Drilling from Floating Vessel

• Anchor lines tensioned

Drilling from Floating Vessel

• Well prepared for spudding– Temporary guide base

(A) set

– 36” Structural hole drilled to 80’ to 200’ BML

– 30” Structural casing (B) run and cemented with permanent guide base (C) attached

AB

C

k

• 26” Conductor hole drilled to approx. 1000’ BML– Can be

drilled with or without riser

– 20” conductor casing run and cemented.

lling

• Wellhead installed with conductor casing

While WOC riser and stack are N/U and latched onto the wellhead

Control pods

Surface hole drilled to 3000’ to 5000’ BML

Surface casing is run and cemented through riser and BOP’s

Floating Drilling

• Float collar drilled out and casing tested

• Float shoe drilled out and 5’ to 15 feet of new formation drilled

• Hole is circulated and conditioned

• Casing seat is tested

Intermediate hole drilled to just above target zone and logged

Intermediate casing set, cemented and tested

Intermediate casing drilled out

Hole circulated and conditioned

Casing seat tested

Production hole drilled to TD and logged

Production casing or liner run and cemented

Well completed and tested

Floating Drilling

• After testing, hole prepared for abandonment– P&A, PNA– TA, T&A, TNA

• Perfs squeezed, and cement plugs set according to regulatore rules and regulations

Floating Drilling

• Riser and BOP retreived

• Casing cut approx. 10’ BML if PNA

• Temporary and permanent guide base retrieved

• Anchors pulled

• Vessel under way to next location