Introduction to Offshore Drilling & Subsea System_Part I_Aerex
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Copyright © Mohd Zaini Kadir, 2011. All Rights Reserved
INTRODUCTION TO Offshore Oil & Gas Operation & Subsea System – Part I
Mohd Zaini Kadir - Tie-In Engineering ManagerNovember 2011
Copyright © Mohd Zaini Kadir, 2011. All Rights Reserved
1. Part I : Introduction to Offshore Operation1. Oil & Gas2. Exploration3. Drilling Rigs4. Drilling a Well5. Exploration Drilling6. Development Drilling & Completion
2. Part II: Subsea Production System1. XMT2. Manifold 3. Tie-in System4. Control System
Content
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Part I: Introduction to Offshore Operation
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Demonstration
Sand & Coke
Bubbles
Straw
Tap
Sea Bed
Sea
We want to retrieve oil andgas but not sand or water
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Source of oil and gas
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A permeable rock allows hydrocarbons to flow from pore to pore within the rock.
Migration
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Trapping Oil and Gas
■ Oilfields and gasfields are areas where
hydrocarbons have become trapped in
permeable reservoir rocks, such as
porous sandstone or fractured
limestone.
■ Migration towards the surface is stopped
or slowed down by impermeable rocks
such as clays, cemented sandstones or
salt which act as seals.
■ Oil and gas accumulate only where
seals occur above and around reservoir
rocks so as to stop the upward migration
of oil and gas and form traps
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Trapped oil and gas (cont’d)
■ Structural traps are formed where rocks are folded into suitable shapes or reservoir and sealing rocks are juxtaposed across faults
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In an anticlinal trap, hydrocarbons migrate into a porous and permeable layer and are trapped there by an overlying impervious layer.
In a fault trap, an impervious layer moves opposite a porous and permeable layer, thereby trapping hydrocarbons.
Trapped oil and gas (cont’d)
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In an unconformity trap, an impervious layer is deposited on top of a hydrocarbon-bearing layer. Hydrocarbons can be
trapped around and above a salt dome
Trapped oil and gas (cont’d)
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A change in permeability within a single rock layer can trap hydrocarbons.
A combination of folding, faulting, and an unconformity can trap hydrocarbons.
Trapped oil and gas (cont’d)
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Exploration - Seismic
A special air gun produces sound that is reflected from rock layers. Detectors pick up the sound reflections.
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Seismic Surveys
■ Ship towing both a submerged air or
water gun array, to produce short
bursts of sound energy, and a set of
streamers of several kilometres length.
■ Each streamer contains a dense array
of hydrophone groups that collect and
pass to recorders echoes of sound
from reflecting layers.
■ The depths of the reflecting layers are
calculated from the time taken for the
sound to reach the hydrophones via
the reflector; this is known as the two-
way travel time
Sea bed
Reflector one
Reflector two
Reflector three
Fig 1 Seismic ray paths from several reflectors
HydrophoneAir Gun
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A seismic section, colour-enhanced by a computer in this example, gives a view of the subsurface and thus the possibility of traps.
Bright spots, shown in red on this colour-enhanced seismic section, may indicate accumulations of natural gas.
Exploration – Seismic Data
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Exploration – Seismic Data
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Ultra deepVery deepDeep
Shallow waterDeep waterVery deep waterUltra deep water
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Exploration
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Exploration
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[9,842ft]
[4,921ft]
[1,640ft]
[393ft]
Exploration
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Four types of mobile offshore drilling units: (A) jackup; (B) drill ship; (C) submersible; (D) semi submersible
Drilling Rigs
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• In shallow water (less than 200 ft depth) an offshore platform rig is used for both drilling and production.• This rig is called a jack- up because it is relatively easy to set up from the ground (seafloor) up to water level.• It is used for both drilling and production. This rig was set up in the Persian Gulf (250 feet water depth).
Drilling Rigs
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• This rig operates in deeper water (about 600 feet depth). Not every part of the rig is anchored to the sea floor. It is therefore called a semi-submersible.
• Buoyancy engineering is utilized to keep some of the structure inside the water so that it neither sinks nor floats (neutral buoyancy).
Drilling Rigs
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• In deeper water (up to 1000ft), a drilling rig such as this would be used.• Long structural members that reach the seafloor support the platform from which drilling and production operations occur.
Drilling Rigs
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• This short seminar will talk about offshore drilling technology in up to 5 miles sea water depth, and certain aspects of the type of engineering that is required to make it possible.
• Our focus will be on riser technology that permits drilling to be performed from a vessel on the ocean surface when the oil formation is several miles from the ocean surface to the sea floor.
Drilling Rigs
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Drilling Rigs
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Floating unitPositioned by Thrusters(DP = Dynamic Positioning)
In this dynamic positioning system, hydrophones on the vessel's hull receive signals from a subsea beacon.The signals and information from a taut wire and a wind sensor are transmitted to onboard computers, The computers process all data and activate the thrusters to maintain the floating unit on station.
Drilling Rigs
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Riser pipe connects the stationary subsea well equipment to the surface equipment on a floating rig.
Drilling Rigs
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Drill collars are heavy pipe that put weight on the bit.
Racked in the derrick, this drill pipe is ready to be run back into the hole.
A typical drill stem assembly
Drilling A Well
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A drill bit has teeth to penetrate a formation to make hole.
Drilling mud is a special liquid essential to the drilling process.
Drilling mud jets out of the bit nozzles to lift cuttings off the bottom of the hole.
Drilling A Well
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The mud pump picks up drilling mud from steel mud tanks and sends it down the kelly (or top drive), drill pipe, drill collars, and bit Mud and cuttings return to the surface up the annulus.
Mud and cuttings return to the surface via the annulus, the space between the pipe and sides of the hole.
Drilling A Well
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Drilling A Well
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A horizontal well begins vertically and is deflected to horizontal.
A bent sub has a 1% to 3% bend in it to begin deflecting the hole from vertical.
Drilling A Well
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Cemented conductor casing lines the top part of the hole. More hole has been drilled out below the casing.
Several casing strings are run and cemented as the well reaches total depth. Note the names given to each string.
Exploration Drilling
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Typical Subsea Well Program:
■ Drill 36” hole to ~80m
■ Run and cement 30” Conductor
■ Drill 26” hole to ~800m
■ Run and cement 20” casing with 18 3/4” WH
■ Run Blow-out-preventer (BOP)
■ Drill 17 ½” hole to ~1300m
■ Run and cement 13 3/8” Casing
■ Drill 12 1/4” hole to ~1700m
■ Run and cement 9 5/8” Casing
■ Drill 8 ½” hole to ~2000m
■ Clean up well
■ Abandon well (run plug or close valve)
■ Proceed to completion operations
This program can be a 100 days plan
Subsea Well Program
BOP
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Xmas Tree Systems
Typical Tree Installation Sequence:
■ Install Xmas Tree on Wellhead using drill string and Tree Running Tool (TRT)
■ Recover TRT
■ Run BOP and marine riser
■ Remove down hole plugs
■ Run completion / production tubing
■ Perforate tubing at reservoir depth
■ Inhibit well and prepare to abandon
■ Install internal tree cap
■ Recover marine riser and BOP
■ Drill rig moves to next well
■ Flowlines and flying leads installed by Rig or installation vessel
XTXT
BOP
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Development Drilling & Completion
A subsea template allows several wells to be drilled, completed, and produced from a relatively small area on the seafloor.
Several directionally drilled wells tap an offshore reservoir.
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Development Drilling & Completion
A perforating gun is lowered into the wellbore and fired. Shaped charges perforate the casing, cement, and formation.
When a packer is set, it forms a seal between the outside of the tubing and the inside of the casing, causing reservoir fluids to flow into the tubing.
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Platform ConceptsMain issues in selection process:
Dry trees versus wet trees
Drilling/workover facilities
Oil storage and offloading versus pipeline
Contractor capabilities and previous experience
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Fixed steel platform■ Conventional technology
■ Limited water depth
■ Platform wells
■ Rigid (supported) risers
■ Comprehensive marine operations
■ Offshore installation of topsides
■ No oil storage
Platform Concepts
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Development Drilling & Completion
A platform tender is anchored next to a relatively small platform.
A self-contained platform houses all the drilling and production equipment, crew quarters, galley, offices, and recreation rooms.A platform jacket is so tall, it is usually
built and transported on its side.
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Fabrication Transportation Installation
Piling
Installation of modules
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Platform installation in the Caspian Sea
Lifting of jacket
Transportation of deck
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Fabrication, transportation, lifting, hook-up important for design
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Fabrication, transportation, lifting, hook-up Kvitebjørn
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Compliant tower■ Extension of conventional fixed
platform technology
■ Complex structural behavior
■ Suitable for deeper water
■ Platform wells
■ Rigid (supported) risers
■ Very comprehensive marine operations
■ Offshore installation of topsides
■ No oil storage
Platform Concepts
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Jack-up platform■ Conventional technology
■ Ideal for shallow water
■ Limited water depth
■ Platform wells
■ Rigid tensioned risers
■ Simple marine operations, self-installing platform
■ At-shore installation of topsides
■ Possibility for subsea oil storage tank
Platform Concepts
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Jack-up platforms for production
Yme - Norway Shah Deniz -Azerbaijan
Siri - Denmark
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Fixed concrete platform■ Conventional technology
■ Robust long-life structures
■ Limited water depth
■ Platform wells
■ Rigid (protected) risers
■ Deepwater construction site and transportation route
■ Comprehensive marine operations
■ In-shore installation of topsides
■ Oil storage
Platform Concepts
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Construction phases for a concrete platform
In dock construction
Inshore construction
Towing to field
Submergence
Deck mating
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A large crane hoists a deck section onto the jacket.
Five boats tow a concrete platform to a site in the North Sea.
Platform Concepts
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Tension leg platform (TLP)■ Well-known, but fine-tuned
hull/mooring configuration
■ Complex dynamic behavior
■ Suitable for deep water
■ Platform wells
■ Top-tensioned (exposed) rigid risers
■ Comprehensive marine operations
■ At-shore installation of topsides
■ No oil storage
Platform Concepts
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Tension legs
Well template
Anchor foundations
Export riser
Oil storage
Oil pipeline
Risers/wells
HullSatellite wells
Satellite wells
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1. Deck on barge
2. Hull submerged before mating
3. Deck mating
4. Deck mating complete
Installation phases for tension leg platform
5. Hook-up of tension legs
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Snorre A - TLP
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Heidrun – Production start 1995
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History of Tension Leg Platforms
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Deep Draft Floater (DDF)■ Un-proven technology
■ Conventional mooring
■ Suitable for deep water
■ Complex dynamic behavior
■ Platform wells
■ Top-tensioned (exposed) rigid risers
■ Limited marine operations
■ At-shore installation of topsides
■ Possibility for oil storage
Platform Concepts
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Spar platform■ Proven technology
■ Limited deck area
■ Conventional mooring
■ Suitable for deep water
■ Complex dynamic behavior
■ Platform wells
■ Top-tensioned (exposed) rigid risers
■ Risers protected in wave zone, “ice protection”
■ Complex marine operations
■ Offshore installation of topsides
■ Possibility for some oil storage, but not tried
Platform Concepts
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Installation phases for Spar platform
Hull in horizontal position
Installation of deckReady for operation
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Shallow Buoy/Barge■ Simple structure
■ Large deck area
■ Possibility for drilling rig
■ Conventional mooring
■ Suitable for deep water
■ Large motions
■ Subsea wells
■ Flexible risers
■ Risers protected in wave zone “ice protection”
■ Simple marine operations
■ At-shore installation of topsides
■ Oil storage
Platform Concepts
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Platform Concepts
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Platform Concepts
Deep Buoy■ Un-proven technology, but similar
to semisubmersibles■ Possibility for drilling rig■ Limited deck area■ Conventional mooring■ Suitable for deep water
■ Well understood dynamic behavior, large motions
■ Subsea wells■ Flexible risers
■ Risers protected in wave zone –“ice protection”
■ Simple marine operations■ At-shore installation of topsides■ Oil storage
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Floating platform■ Proven technology
■ Possibility for drilling rig
■ Conventional mooring
■ Suitable for deep water
■ Well understood dynamic behavior
■ Subsea wells
■ Flexible risers
■ Simple marine operations
■ At-shore installation of topsides
■ No oil storage
Platform Concepts
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Typical floating production system
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Veslefrikk – first floating production platform on the NCS, 1989
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Platform Concepts
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Ship-shaped unit■ Proven technology
■ Large deck area
■ Conventional mooring
■ Suitable for deep water
■ Well understood dynamic behavior, large motions
■ Weather vaning
■ Subsea wells
■ Flexible risers and swivel
■ Congested riser area
■ Simple marine operations
■ At-shore installation of topsides
■ Oil storage
Platform Concepts
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Turret and swivel systems
Turret location, a choice based on an overall assessment of:
General lay-out
Natural ventilation
Weather protection
Active heading control
Motions and accelerations
Riser loads
Mooring loads
Challenges:
Crucial for production
Crucial for well control
Congested area
Potential leak sources
Material handling
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Norne
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A tie-in pipe line joins a trunk line running to a shore facility.
This lay barge is at work in the North Sea.
Protruding from the stern of this semi submersible lay barge is the stinger, which supports the pipe as it enters the water
Oil & Gas Transportation
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In this subsea production system, oil flows from wells on the template, up the production riser, and to a special mooring buoy, where a tanker loads the oil.
Development Drilling & Completion
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