Offshore Engineering for Structural Engineers

OFFSHORE ENGINEERING FOROFFSHORE ENGINEERING FOR STRUCTURAL ENGINEERS

Facilitator: Kunle AdelekeFacilitator: Kunle Adelekekadeleke@yahoo.com

March 2009March 2009

Table of Content

IntroductionT f Off h Pl tfTypes of Offshore PlatformsFixed Platform DescriptionAcronyms & Terminologies

1.0 INTRODUCTION

• Oil and gas are considered among the world's most important resources. The oil and gas industry plays a critical role in driving the global economy.

• Oil is not only an essential raw material to over 2,000 end products but isalso used for transportation, heating, electricity and lubrication. It supplies about 50% of the world’s total energy requirements.

• About 90 countries produce oil, although a few major producers account for the bulk of world output.

• Oil and gas reserves are heavily concentrated in the Middle East, and gasin the Russian Federation. About 40% of the world’s crude oil are supplied by

12 OPEC countries (Algeria, Angola, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria,Qatar Saudi Arabia the United Arab Emirates and Venezuela) They accountQatar, Saudi Arabia, the United Arab Emirates and Venezuela). They account for about two-thirds of proven reserve.

• Major non-OPEC oil producing countries are, the United States, Mexico,Denmark, Norway, the United Kingdom and Russia, China and Vietnam.

1.1 The Industry

• The petroleum industry comprise upstream and downstream sectors.

• Upstream involves exploration, development, and production of oil and gas.

• Downstream covers transport, refining, petrochemicals, distribution, and retail.

1.2 Exploration

Oil and gas exploration encompasses the processes and methods involved inlocating and discovering potential sites for oil and gas drilling and extraction. This is the first-stage of oil and gas production. Many uncertainties exist during the exploration process Geological surveys are conducted for onshore explorationthe exploration process. Geological surveys are conducted for onshore explorationand seismic imaging for offshore exploration.

Seismic display in avisualization room

Colour display of anOil & Gas field

1.3 Drilling & Extraction

Drilling is the final stage in the exploration process. When 3D seismic has been completed, it is time to drill the well. Onshore exploration relies on fixed or mobile drillings rigs. Offshore exploration can require fixed offshore Jackup drill rigs, Semi-Submersible drill rigs and Deep Water Drill Ships. Larger production platforms may l h h i d i d illi ialso have their own production drilling equipment.

• Jack-up Drill Rigs, as the name suggests, are platforms that can be jacked up above the sea using legs which can be lowered like jacks. These platforms, used in relatively low depths are designed to move from place to place and then anchor themselves bylow depths, are designed to move from place to place, and then anchor themselves by deploying the jack-like legs.

• Semi-submersible Drill Rigs: having legs of sufficient buoyancy to cause the structure to float, but of weight sufficient to keep the structure upright. Semi-submersible rigs can b d f l t l d b b ll t d d b lt i th tbe moved from place to place; and can be ballasted up or down by altering the amount of flooding in buoyancy tanks; they are generally anchored by cable anchors during drilling operations, though they can also be kept in place by the use of dynamic positioning. Semi-submersible can be used in depths from 600 to 6,000 feet (180 to 1,800 m).

• Drillships, a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory drilling of new oil or gas wells in deep water but can also be used for scientific drilling. It is often built on a modified tanker hull and outfitted with a dynamic positioning system to maintain its position over the welldynamic positioning system to maintain its position over the well.

Onshore Drilling Rigs

Components of a drilling rig

Onshore drilling rig, Sonora Field, West Texas

Offshore Drilling Rigs

Jackup Drilling Rig S i S b D illi RiJackup Drilling Rig Semi-Sub Drilling Rig

West Polaris Drillship

1.4 Onshore Development

In onshore development, the wells are grouped together in clusters forming a gathering system. This gathering system consists of a network of connecting carbon steel pipes which sends the oil and gas to a production and processing f ilitfacility.

While there are oil or gas only installations, more often the wellstream will consist of a full range of hydrocarbons from gas (methane butane propaneconsist of a full range of hydrocarbons from gas (methane, butane, propane etc.), condensates (medium density hydro-carbons) to crude oil. With this well flow we will also get a variety of non wanted components such as water, carbon dioxide, salts, sulfur and sand.

In the production and processing facility the oil and gas is treated through chemical and heating processes. The oil and gas is then separated from water and sediments and placed in storage after which the resources can be

d th h i li t l di t i l h th dpumped through pipelines to loading terminals where the resources are ready to be transported by oil tankers or transport vehicles. The water removed from the oil and gas is also treated and eventually pumped back into the reservoir.

1.5 Offshore Development

In offshore development, depending on the size and water depth, different types of structures are used. Drilling wells can be conducted from either the platform or underwater. The production from thefrom either the platform or underwater. The production from the wellheads feed into the production and test manifolds from where the crude is sent into the separators. The production and extraction process can consist of fixed platforms or floating vessels. Offshore platforms contain processing equipment and facilities onboard and the resourcescontain processing equipment and facilities onboard and the resources extracted are transported by pipeline or stored so it can be loaded on tankers. Additional processing requirements are completed at onshore production facilities. p

In gas production and development, production and condensation plants are required in which a liquefaction plant provides treatment, refrigeration and liquefaction followed by the storage and loading of liquefied gas. The gas is transferred to liquefied natural gas tankers (LNG's) which transports the gas to a treatment plant where the gas undergoes re-gasification from storage tanks at the plantundergoes re-gasification from storage tanks at the plant.

Oil & Gas Production Process

2.0 TYPES OF OFFSHORE PLATFORMS

The different development options can be broadly classified into three categories:

• fixed platforms,

• floating systems,

• subsea systemssubsea systems

2.1 Fixed Platforms

These are the structures that physically sit on the bottom of the sea BeingThese are the structures that physically sit on the bottom of the sea. Being held by the sheer weight of the structure or by piles driven into the seabed to hold them in place. Fixed platforms are economically feasible for installation in water depths up to about 1,700 feet (520 m). They include:

• Jacket-based platforms: these consist of a jacket and a deck. The jacket is tall, vertical section built from tubular steel members and is locked to the seabed by driven piles. The deck (or topside) is where crew quarters, production facilities and drill rigs are located. p g

• Compliant towers; - these are made of tubular steel members and are fixed to the bottom with piling, and supports a deck. Compliant towers are designed to sustain significant lateral deflections and forces, and are typically used insustain significant lateral deflections and forces, and are typically used in water depths ranging from 1,500 and 3,000 feet (450 and 900 m).

• Gravity base platforms; - They are enormous concrete fixed structures placed on the bottom, typically with oil storage cells in the “skirt” that rests on the seaon the bottom, typically with oil storage cells in the skirt that rests on the sea bottom. The large deck receives all parts of the process and utilities in large modules. Gravity base platforms are used in up to 1000ft of water, but the seabed has to be especially firm to ensure no creep over time.

Shallow water complex:They contain several independent platforms with different parts of the process and utilities limked with gangway bridges Individual platforms may include Wellheadutilities limked with gangway bridges. Individual platforms may include Wellhead platforms, Riser Platform, Processing Platform, Gas Compression Platform, Accomodation Platform and Power Generation Platform.

Ekofisk Field Center by Phillips Petroleum (ConocoPhillips)

Fixed Platform in the Gulf of Mexico Gravity Base PlatformFixed Platform in the Gulf of Mexico Gravity Base Platform

Living Quarters, Production & Gas Compression Modules on a Production Platform Complex Offshore Nigeria

2.2 Floating Production Systems

These include TLPs, FPS’s, spars, and FPSOs. All four have to be moored in place with tendons or wire rope and chains in order to stay connected to the wells below.

• Tension leg platforms (TLPs);- these have floating hulls made of buoyant columns and pontoons. Steel pipe tendons hold the hull below their natural level of flotation keeping the tendons in tension and the hull in placelevel of flotation, keeping the tendons in tension and the hull in place eliminating most vertical movement of the structure. TLPS are used in water

depths up to about 6,000 feet (2,000 m).

• Spar platforms;- consists of a single tall floating cylinder hull, supporting a fixed deck. The large cylinder, weighted at the bottom stabilises the structure in water. Eight to 16 wire or synthetic rope and chain combinations moor the g y phull to the seabed.

• Floating production systems (FPS’s);- these consists of ship shape, TLP-like, or a semisubmersible hulls with production facilities on boardor a semisubmersible hulls with production facilities on board.

• Floating production, storage and offloading systems (FPSOs): These have large ship shape, made either converted tankers or new construction. They have no drilling capability. Moored to place with rope and chain They process production from subsea wells andrope and chain. They process production from subsea wells and store large crude oil volumes, accumulated for later transport by shuttle tankers.

FSO SPAR

Agbami FPSO

Some Typical Offshore Projects

BPThunder Horse FPU

ChevronTexacoSanha Platform

BPAtlantis FPU Hull

ExxonMobilKizomba “B” TLP

TotalFina ElfDalia FPSO Topsides ExxonMobil

ChevronTexacoBenguela-Belize CT Project

Dalia FPSO Topsides ExxonMobilSable Compression P/F

2.3 Subsea Systems

These can have single or multiple wellheads on the sea floor connected directly to a host platform or to a subsea manifold. The systems include connections by flowlines and risers to fixed or floating

t th t ld b il It b t i d th tsystems that could be miles away. It can be set in any depth water.

3.0 FIXED PLATFORM DESCRIPTION

• Most common offshore structures used for oil/gas exploration and production.

• Suitable for water depths from <50m up to about 300m

• The deck (topside) contains drilling and production equipmentThe deck (topside) contains drilling and production equipment

• Jacket leg - the steel or concrete structure that rises from the seabed to above the water line.

• The pilings, steel cylinders that secures the platform to the seabed

• The conductors or risers, steel pipes through which the wells are , p p gdrilled, completed, and produced.

3.0 ACRONYMS & TERMINOLOGIESABSAmerican Bureau of ShippingAFCApproved for constructionApproved for constructionAFDApproved for designAISCAmerican Institute Of Steel ConstructionAmerican Institute Of Steel ConstructionAnnulusSpace between concentric casing strings.APIAmerican Petroleum InstituteAmerican Petroleum InstituteAPI GravityAn arbitrary scale expressing the relative density of liquid petroleum products. ASMEAmerican Society of mechanical engineersAmerican Society of mechanical engineers.Associated gasNaturally occurring reservoir gas found in association with oil, either dissolved in the oil or found as a cap or pocket of free gas above the oil.AWSAmerican Welding Society.

BarrelA common English-unit measure of liquid volume which, in the petroleum industry, equals 42 U S liquid gallons for petroleum or natural gas liquid productsequals 42 U.S. liquid gallons for petroleum or natural gas liquid products measured at 60°F and equilibrium vapor pressure.

BOMBill of materialBill of materialCaissonLength of pipe extending vertically downwards from an installation into the sea as a means of depositing of waste waters, or of a location of a sea water pumpCasing Pipe used to line and seal the well and prevent collapse off the borehole. A number of casing strings (lengths) are used in ever decreasing diameters.Casing head gasCasing head gasUnprocessed natural gas produced from a reservoir containing oil. It contains heavier hydrocarbon vapors and is usually produced under low pressure from a casing head on the well.Catenary mooringCatenary mooringSystem consisting of multiple chains or wire ropes spreading from the buoy or tanker to the anchor points.Cathodic protectionCorrosion protection system which relies on sacrificial anodes or impressedCorrosion protection system which relies on sacrificial anodes or impressed current to protect submerged steel components from corrosion by electrolytic action.

CBControl BuoyControl BuoyCCRCentral Control Room.CGTCompliant Guyed TowerChokeA valve like device with a fixed or variable aperture specifically intended t l t th fl f fl idto regulate the flow of fluids.Christmas treeAn assembly of valve attached to the wellhead and used to control well productionproduction.COChange OrderCondensateThe liquid formed by the condensation of a vapor or gas; specifically, thehydrocarbon liquid separated from natural gas because of changes in temperature and pressure when the gas from the reservoir wastemperature and pressure when the gas from the reservoir was delivered to the surface separator.

ConductorThe first and the largest diameter pipe to be inserted(spudded) into the seabed when drilling a well. It keeps thehole open, provides a return passage for the drilling mud andsupports the subsequent casing strings.supports the subsequent casing strings.CPTCompliant Piled Tower.CPUCPUCaisson Production Unit.DALsDesign Accident Loads.DPRDepartment of Petroleum ResourcespDynamic positioningSatellite monitoring system used to control the action ofthruster propellers to maintain a vessel on location withoutthruster propellers to maintain a vessel on location withoutdeploying anchors.

EIAEnvironmental Impact Assessment (analysis)EPCIEPCIEngineering Procurement Construction InstallationFATFactory Acceptance TestFactory Acceptance TestFEEDFront End Engineering and DesignFlexible RiserFlexible, usually reinforced polymer pipe, for transmission of oil/gas between seabed and FPS.Flow linePi i hi h di t ll fl id f llh d t if ld fi tPiping which directs well fluids from wellheads to manifold or first process vessel.FPFull PenetrationFull PenetrationFPDSOFloating Production, Drilling, Storage and Offloading System.

FPSFloating Production SystemFPSOFPSOFloating, Production, Storage and Offloading SystemFPUFloating Production UnitFloating Production UnitGAGeneral ArrangementGas injectionjThe injection of a natural gas into a reservoir to maintain or increase the reservoir pressure or reduce the rate of decline of the reservoir pressure.Gas liftA th d f b i i d il t t th f b i j tiA method of bringing crude oil or water to the surface by injection gas into the producing well bore.Gathering systemThe network of pipelines which carry gas from the wells to theThe network of pipelines which carry gas from the wells to the processing plant or other separation equipment.GroutMixture of cement and water (no sand) used to secure and seal attachment s ch as piles into jacket legsattachment such as piles into jacket legs.

HAZIDHazard identification studiesHAZOPHAZOPHazard and operability studies.IDCInter Discipline CheckInter Discipline CheckIFAIssued For ApprovalIFCIssued For ConstructionIFIIssued For InformationIFPIssued For Preliminary DesignIIFI id t d I j FIncident and Injury Free.JacketSteel support framework used to support platform topsides

Lean gas(1)The residue gas remaining after recovery of natural gas liquids in a gas

i l tprocessing plant.(2)Unprocessed gas containing little or no recoverable natural gas liquids.Lean oilAbsorption oil as purchased or recovered by the plant, or oil from which the absorbed constituents have been removed.Light hydrocarbonThe low molecular weight hydrocarbons such as methane, ethane, propane and butane.LNG (liquefied natural gas)LNG (liquefied natural gas)The light hydrocarbon portion of natural gas, predominately methane, which as been liquefiedLPGLPG Liquefied petroleum gas, essentially propane and butane held in the liquid state under pressure to facilitate storage and transportation.LQLQLiving Quarters

LSALife Saving ApplianceManifoldManifoldAn assembly of pipes, valves and fitting by which fluid from one or more sources is selectively directed to various process systems.Marine drilling riser pipe extending from the blowout preventer on the seabed to g p p g pthe drilling rig on the surface, to permit the return of the drilling mud.MHMan HourMODUMODUMobile Offshore Drilling Unit MTOMaterial Take-offMaterial Take-offMud lineThe base of the jacket at the seabedNatural gasgGaseous form of petroleum. Consisting predominately of mixtures of hydrocarbon gases. The most common component is methane.NNPCNi i N i l P l C iNigerian National Petroleum Corporation

PDMSPlant Design Management SystemPFDProcess Flow DiagramPigSpherical device inserted into a gas sub sea pipeline to sweep the line of deposits of rusts scale and condensated liquids May also be used to clean oil pipelines of waxrusts, scale and condensated liquids. May also be used to clean oil pipelines of wax and may be ”intelligent”, that is containing measuring and inspection equipment.PiggingA procedure for forcing a device through a pipeline for cleaning purposes, separating

d t i ti th liproducts, or inspecting the line.PipelinePiping used to convey fluids between platforms or between a platform and a shore facilityfacility.PPPartial PenetrationPressure vesselContainer, normally cylindrical used to contain internal, or occasionally external pressure.Produced waterF ti f t d f th il d i th f lFormation of water removed from the oil and gas in the process of pressure vessels.PSVPressure Safety Valve.

PWHTPost Weld Heat TreatmentQuantity assuranceQuantity assuranceA sequence of planned and systematic action necessary to provide adequate confidence that a product or service will satisfy given requirements of qualityof quality.Quality controlThe operational techniques and activities that are used to ensure that a quality product or service will reproducedquality product or service will reproduced.Raw gasUnprocessed gas, or the inlet gas to a gas processing plant.RFQRequest For QuotationRiggA term normally associated with drilling equipment, that is a drilling rig.Also a slang term used extensively to describe any of the structures and vessels associated with oil and gas production and explorationvessels associated with oil and gas production and exploration.

RiserThe vertical portion of a sub sea pipeline (including the bottomThe vertical portion of a sub sea pipeline (including the bottom bend) arriving on or departing from a platform.RPERegistered Professional Engineer.ScourRemoval of the sea bed in the vicinity of a jacket, sub sea wellhead or pipeline by tidal action.ScrubberScrubberPressure vessel containing equipment designed to remove or scrub liquids from a gas stream.Semi-FPSSemi-Submersible floating Production System.SkidSteel framework used to contain equipment, may be transportableSSIDSafety In DesignSOLASSafety of Life at Sea (one of the international conventions)Safety of Life at Sea (one of the international conventions)

Specific gravityThe ratio of the mass of a given volume of substance to that of equalThe ratio of the mass of a given volume of substance to that of equal volume of another substance used as standard. Unless otherwise stated, air is used as standard for gases and water for liquids, with volume measured at 60°F and standard atmospheric pressure.p pSPMSingle Point MooringSweetSweetGas containing essentially no objectionable sulfur compounds. Also, treated gas leaving a sweetening unit.S tSweet gasGas which has no more than the maximum sulfur and/or Co2 content defined by (1) the specification for the sales gas from a plant (2) the d fi iti b l l b d Al t t d l i t i itdefinition by a legal body . Also, treated gas leaving a sweetening unit.TLPTension Leg PlatformTLWPTension Leg Wellhead Platform

TopsidesUpper part of a fixed installation which sits on top of the jacket and pp p p jconsists of the decks, accommodation and process equipmentTurretSystem either built into the hull or attached to the bow of a tanker. Consists of a large tube connected to a vessel via a slew ring bearing. Mooring chains are attached to the turret. The slew ring allows weathervaning. Flexible risers bring produced fluids into the turretinto the turret.Fluid swivels transfer the fluid to the weathervaning tanker.WellheadThe assembly of fittings valves and controls located at the surface andThe assembly of fittings, valves, and controls located at the surface and connected to the flow lines, tubing, and casing of the well so as to control the flow in the reservoirWet gasWet gasA gas containing water, or a gas which has not been dehydratedWork overRe-entry into a completed well for modification or repair workRe-entry into a completed well for modification or repair workWPSWelding Procedure Specification