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


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


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


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


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.



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


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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.



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


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


Ultra deepVery deepDeep

Shallow waterDeep waterVery deep waterUltra deep water

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Exploration


Exploration

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[9,842ft]

[4,921ft]

[1,640ft]

[393ft]

Exploration


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 jackup 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


• 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


• 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


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


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


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


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


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


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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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.


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



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


Platform installation in the Caspian Sea

Lifting of jacket

Transportation of deck

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Fabrication, transportation, lifting, hook-up important for design


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


■ No oil storage

Platform Concepts


Jack-up platform■ Conventional technology

■ Ideal for shallow water


■ 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


Fixed concrete platform■ Conventional technology

■ Robust long-life structures


■ Platform wells

■ Rigid (protected) risers

■ Deepwater construction site and transportation route


■ 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


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



■ No oil storage

Platform Concepts


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


Snorre A - TLP

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Heidrun – Production start 1995


History of Tension Leg Platforms

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Deep Draft Floater (DDF)■ Un-proven technology

■ Conventional mooring



■ Platform wells


■ Limited marine operations


■ Possibility for oil storage

Platform Concepts


Spar platform■ Proven technology

■ Limited deck area




■ Platform wells


■ Risers protected in wave zone, “ice protection”

■ Complex marine operations


■ 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


Shallow Buoy/Barge■ Simple structure

■ Large deck area

■ Possibility for drilling rig



■ Large motions

■ Subsea wells

■ Flexible risers

■ Risers protected in wave zone “ice protection”

■ Simple marine operations


■ Oil storage

Platform Concepts

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Platform Concepts


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



■ Well understood dynamic behavior

■ Subsea wells

■ Flexible risers



■ No oil storage

Platform Concepts


Typical floating production system

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Veslefrikk – first floating production platform on the NCS, 1989


Platform Concepts

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Ship-shaped unit■ Proven technology

■ Large deck area



■ Well understood dynamic behavior, large motions

■ Weather vaning

■ Subsea wells

■ Flexible risers and swivel

■ Congested riser area



■ Oil storage

Platform Concepts


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


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.



Introduction to Offshore Drilling & Subsea System_Part I_Aerex

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