DIFFERENT TYPES OF OFFSHORE RIGS

Prepared by: NILOTPAL NATHB.Tech Petroleum engineering(3rd semester), 2013-2017.Dibrugarh University Institute of Engineering and Technology (DUIET),Assam, India

Mainly two types of OFFSHORE RIGS

BOTTOM SUPPORTED

1. Jack-up2. Barge3. Fixed platform

FLOATING VESSEL1. Drillship2. Semisubmersible

FLOATING VESSEL Floating vessel is a type of offshore rig with

facilities used to drill wells, to extract and process oil and to temporarily store product until it can be brought to shore for refining and marketing.

Drillships Semisubmersibles

DRILLSHIPS Marine vessel modified to drill oil & gas wells Operable at 2,000-10,000 ft of water. Equipped with drilling derrick, moon pool,

positioning equipment , living quarters & helipad.

ADVANTAGES Easy mobility Operable at great water depthsDISADVANTAGESo Is easily agitated by waves, winds & current.

First developed in 1940s by marine architects by modifying a US Navy patrol craft.

In 2011, Drillship Dhirubhai deepwater KG2 operated by TRANSOCEAN set world record at 10,194 ft while working for RELIANCE in India.

Japan’s CHIKYU drills at 4 miles below the seabed which is 2-3 times that of otherdrillships.

Transocean, Pride, Seadrill, Maersk, Frontier drilling & Noble own & operate drillships.

DRILLSHIPS

SEMISUBMERSIBLES Able to work in harsher

conditions that drillships can withstand.

Depth around 520m. Contains drilling equipment &

other machinery supported by platoon type columns submerged into water.

Could be fitted with a dynamic position system.

Transported by tugs & barge.

ADVANTAGES

They are easier to transport as they float

They are more stable than drillships.

SEMISUBMERSIBLES

1. Jack up2. Fixed platform3. Barge

They are mostly used in exploratory drilling.

Operational in water depths upto 210m

Mobile yet gives the stability of a fixed rig.

Could be constructed at the shore and be moved to location.

Less rig uptime and downtime.

JACKUP RIGS

A JACK UP RIG BEING TRANSPORTED TO LOCATION USING TUGS.

A JACK UP RIG BEING TRANSPORTED ON A HEAVY LIFT SHIP

FIXED OFFSHORE RIGS1. CONVENTIONAL FIXED

PLATFORM.2. COMPLIANT TOWER

PLATFORM.3. GRAVITY BASED

STRUCTURE (GBS).

A fixed rig could be tendered or self contained. A tendered fixed platform

CONVENTIONAL FIXED PLATFORMS

JacketStructure

Topsideplatform

CONVENTIONAL FIXED PLATFORMS

Simplest type of offshore rig.Water depths, up to 412m (Shell's Bullwinkle

platform)Non mobile, thus are for long term use.Needs to be assembled at location.

CONVENTIONAL FIXED PLATFORMS

Bullwinkle's Jacket during moving to location

SHELL'S BULLWINKLE PLATFORM IN GULF OF MEXICO

COMPLIANT TOWER RIGS

Compliant tower section

Use of flex elements such as flex legs or axial tubes, resonance is reduced and wave forces are de-amplified. Compliant towers are designed to sustain significant lateral deflections and forces.

Despite its flexibility, the compliant tower system is strong enough to withstand hurricane conditions.

Section of compliant tower being constructed at a dry dock

Benguela Belize Compliant Tower platform.

COMPLIANT TOWER PLATFORMS

Operational in water depths of 450m to 650m.Ability to dampen the incoming waves by incorporating flex

materials in the tower section.Can withstand harsher weather conditions (hurricanes,

typhoon, etc.) compared to semisubmersible and conventional fixed platforms.

Conventional production risers can be accommodated leading to reduced costs.

GRAVITY BASED STRUCTURE PLATFORMS

GRAVITY-BASED STRUCTURES• A gravity-based structure

(GBS) is a support structure held in place by gravity. A common application for a GBS is an offshore oil platform.

• Made of steel reinforced concrete, commonly known as CONDEEP- DEEP-sea CONcrete structure

Setup on a long term basis.Could be constructed at shore

facilities and moved to location.Resists extreme weather

conditions.Added storage area.Some CONDEEPS are also able to

resist iceberg forces. Eg: Hibernia

GRAVITY-BASED STRUCTURES

Hibernia GBS platform

DRILLING BARGESWater depths upto 40 feetMainly inland water drillingIncase of a swamp, requires

dredging of a slip, for it to be moved to location.

Wave action should not be severe.

A SWAMP BARGE

Wave simulations on an offshore rig

Offshore rigs are susceptible to some of the most harshest sea environments in the world.

Thank You