DPV2043 Week Unit7

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UNIT 7: SURFACE FACILITIES

MOHD FIRDAUS BIN KAMURI

DEPARTMENT OF PIPING

KKTM KEMAMANEmail: [email protected]

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LEARNING OUTCOMES

After completing this subject, student should be able to:

1. Describe the onshore and offshore processes.

2. Identify the different types of upstream facilities.

3. Discuss the processes in different types of facilities.

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Oil and gas production process

Onshore

The picture shows a well equipped with a sucker rod pump (donkey pump) oftenassociated with onshore oil production

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Offshore

Fixed platform

Minimal structures that can be constructed quickly and costeffectively often lack redundancy and they are somewhat moresusceptible to failure than other structures. There are more than 100minimal structure designs and most of these were intended tosupport deck payloads of 400-1000 tons and transmit the functionaland environmental loads to the seafloor through driven or drilled andgrouted piles. Some of the other structures carry larger deckpayloads and/or rely on gravity base structures, rather than piles, to

transmit the loads to the seafloor. Although each minimal structuredesign is unique, these designs can be grouped into structure typesdefined as Tripods, Braced Caissons, Braced Monopods andMonotowers

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Tripods: A typical Tripod is a tubular space frame consisting ofthree legs and the bracing system that connects the legs. It issecured to the seafloor with three piles.

Figure : Typical Tripod

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7.1 Drilling Platform

Definitions

Drilling Facilities: Defined to be structures located on a platformcontaining systems and equipment required for drilling oilwells.

Abbreviations DDA: Drilling data acquisition system.

BOP: Blow out preventer.

MWD: Measurement while drilling.

TSV: Tender support vesseL

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FUNCTIONAL REQUIREMENTSGeneral

The main objectives are to optimise the design and operations of drillingfacilities with respect to utilisation, operational efficiency, life cycle cost andacceptable safety levels.

The Principle of Removable Drilling Facilities

The drilling facilities shall be removable and provide efficientmobilization/demobilization onto production/wellhead platforms in order toobtain a high degree of utilisation. Two classes of drilling facilities has beendefined; class I for wells up to appr. 6500m and class II for wells up to appr.

10000m. The intention of defining two classes is to optimise between thetwo principal requirements of:

a) drilling all ranges of wells

b) having a standardised design.

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Operational Requirements

General

The drilling facilities shall be designed to be operated and maintained withminimum manning levels. Complexity of the systems and equipment, andthe amount of equipment, shall therefore be kept low.

Regularity The operation of the drilling facilities shall obtain a regularity of 98% with

respect to equipment and maintenance down time.

Simultaneous operations

The design shall allow for optimum simultaneous drilling and production

operations. It shall be possible to perform well intervention operations through the drill

floor

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Back-up power for drilling

In case of platform main power failure back-up power for drilling is required tosecure well and equipment. The back-up power source shall supply minimum500kW. It shall at least be possible to

circulate at reduced rate

mix and transfer mud lift/rotate drill rating

complete cement job

Drilling instrumentation

A Drilling Data Acquisition system (DDA) shall be supplied to allow for the

operator to monitor drilling trends and store historical data. A permanent,common arrangement for signal collection shall be utilized by drilling contractor,MWD, mud logger and other third party to assist in performing efficient and safedrilling operations.

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Health, safety and environment

The facilities shall be designed to minimise operational risks for fires, blowouts, gas

leaks and serious personnel injuries.

Drilling Systems

The drilling facilities shall include all systems that are required to successfully drill the platformwells. These systems shall include:

Derrick (mast) and hoisting equipment

Rotary equipment Pipehandling system and storage

Drillfloor and substructure w/equipment

Bulk system

Mud mixing and storage system

High pressure mud system

Mud treatment system

Cementing system

Kill & Choke manifold system

BOP, diverter and drilling riser system

Drilling data acquisition system

Functional requirements to the above systems are described in the NORSOK Standard Systemand Service Data Sheets. Space requirements for a cuttings disposal (e.g. injection) system shall

be considered.

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Utility Systems

The following utility systems shall support the drilling facilities:

Back up power supply

Plant and bulk air

Contaminated drains (mud) HVAC

Hydraulic power

Hot water, high pressure washdown system

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Layout Requirements

General

All work areas in connection with drilling activities shall be arranged so as toensure totally adequate safety for personnel and operations, working

environment and pollution control, in accordance with technical safety,environmental care, working environment and project safety goals. Thelayout of the drilling facilities shall take due consideration to areas that maybe critical to dropped objects, especially in connection with materialshandling. The layout shall ensure that maintenance and service can becarried out in an ergonomically efficient way.

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Materials handling

The layout and design of the drilling facilities shall place emphasis onachieving an efficient and safe method of transporting and handling ofmaterials from one place to another. This is especially relevant for drillingtubular handling, but is equally important for chemicals and equipment

transport to/from workshops etc.

Workshops, stores and offices

Workshops for welders, electricians, instrument engineers, hydraulicengineers and mechanics with necessary equipment shall be available.There shall be sufficient dry and heated stores for drilling equipment andspare parts. Relevant transportation/handling facilities shall be provided.The drilling offices shall be classified a safe area with optimum access to allareas of the drilling facilities, especially the drill floor.

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Completion and intervention equipment

Sufficient space shall be provided for equipment and operations forcompletion and intervention equipment (electric logging/wireline, coil tubing,snubbing, well completion and well testing). All necessary utilities shall beavailable close to the specific equipment, including temporary

communications equipment.

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Interfaces

Utility interfaces

All utilities between the drilling facilities and the platform shall have termination points outside thedrilling facilities. Platform systems shall be routed outside the dedicated area for the drilling facilities.

The following utilities shall be supplied by the platform facilities to support the drilling facilities:

Main electrical power

Emergency power Fire and gas control systems

Fire water

Emergency shutdown system

Sea, fresh and potable water

Mud base fluids

Drains

Uninterruptable electrical power supply

Instrument air

Diesel

Telecommunications

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Layout

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Test Separators and Well test

Test separators are used to separate the well flow from one or morewells for analysis and detailed flow measurement. In this way, thebehavior of each well under different pressure flow conditions canbe determined. This normally takes place when the well is taken intoproduction and later at regular intervals, typically 1-2 months and will

measure the total and component flow rates under differentproduction conditions.

The separated components are also analyzed in the laboratory todetermine hydrocarbon composition of the Gas oil and Condensate.

The test separator can also be used to produce fuel gas for power

generation. In place of a test separator one could also use a threephase flow meter to save weight.

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Production separators

The main separators are gravity type. As mentioned the productionchoke reduces will pressure to the HP manifold and First stageseparator to about 3-5 MPa (30-50 times atmospheric pressure).Inlet temperature is often in the range of 100-150 degrees C.

the well stream is colder due to Subsea wells and risers. The

pressure is often reduced in several stages; here three stages areused, to allow controlled separation of volatile components. Thepurpose is to achieve maximum liquid recovery and stabilized oiland gas, and separate water.

A large pressure reduction in a single separator will cause flash

vaporization leading to instabilities and safety hazards. Theretention period is typically 5 minutes, allowing the gas to bubbleout, water to settle at the bottom and oil to be taken out in themiddle. In this platform the water cut (percentage water in the wellflow) is almost 40% which quite high. In the first stage separator, thewater content is typically reduced to less than 5%.

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At the crude entrance there is a baffle slug catcher that will reduce the effectof slugs (Large gas bubbles or liquid plugs). However some turbulence isdesirable as this will release gas bubbles faster than a laminar flow.

The liquid outlets from the separator will be equipped with vortex breakersto reduce disturbance on the liquid table inside. This is basically a flange

trap to break any vortex formation and ensure that only separated liquid istapped off and not mixed with oil or water drawn in though these vortices.Similarly the gas outlets are equipped with demisters, essentially filters thatwill remove liquid droplets in the gas.

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Other types of separators such as vertical separators, cyclones(centrifugal separation) can be use to save weight, space or improveseparation.There also has to be a certain minimum pressuredifference between each stage to allow satisfactory performance inthe pressure and level control loops.

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Second stage separator

Second stage separator

The second stage separator is quite similar to the first stage HPseparator. In addition to output from the first stage, it will alsoreceive production from wells connected to the Low Pressuremanifold. The pressure is now around 1 MPa (10 atmospheres) and

temperature below 100 degrees C. The water content will bereduced to below 2%. An oil heater could be located between thefirst and second stage separator to reheat the oil/water/gas mixture.This will make it easier to separate out water when initial water cut ishigh and temperature is low. The heat exchanger is normally a

tube/shell type where oil passes though tubes in a cooling mediumplaced inside an outer shell.

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Third stage separator

Third stage separator

The final separator here is a two phase separator, also called aflash-drum. The pressure is now reduced to about atmosphericpressure (100 kPa) so that the last heavy gas components will boilout. In some processes where the initial temperature is low, it might

be necessary to heat the liquid (in a heat exchanger) again beforethe flash drum to achieve good separation of the heavy components.There are level and pressure control loop.

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Coalescer

Coalescer

After the third stage separator, the oil can go to a coalescer for finalremoval of water. In this unit the water content can be reduced tobelow 0.1%. The coalescer is completely filled with liquid: water atthe bottom and oil on top. Inside electrodes form an electric field to

break surface bonds between conductive water and isolating oil inan oil water emulsion. The coalescer field plates are generally steel,sometimes covered with dielectric material to prevent short circuits.The critical field strength in oil is in the range 0.2 to 2 kV/cm. Fieldintensity and frequency as well as the coalescer grid layout is

different for different manufacturers and oil types

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Electrostatic Desalter

Electrostatic Desalter

If the separated oil contains unacceptable amounts of salts, it can beremoved in an electrostatic desalter (Not used in the Njord example)The salts, which may be Sodium, Calcium or Magnesium chloridescomes from the reservoir water and is also dissolved in the oil. The

desalters will be placed after the first or second stage separatordepending on Gas Oil Ratio (GOR) and Water cut.

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Water treatment

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Water treatment

Water treatment

Water from the separators and coalescers first goes to a sandcyclone, which removes most of the sand. The sand is furtherwashed before it is discharged. The water then goes to ahydrocyclone, a centrifugal separator that will remove oil drops. The

hydrocyclone creates a standing vortex where oil collects in themiddle and water is forced to the side.

Finally the water is collected in the water de-gassing drum.Dispersed gas will slowly rise to the surface and pull remaining oildroplets to the surface by flotation. The surface oil film is drained,

and the produced water can be discharged to sea. Recovered oil inthe water treatment system is typically recycled to the third stageseparator.

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Gas treatment and Compression

The gas train consist of several stages, each taking gas from asuitable pressure level in the production separators gas outlet, andfrom the previous stage. Incoming gas is first cooled in a heatexchanger. It then passes through the scrubber to remove liquidsand goes into the compressor. The anti surge loop and the surge

valve allows the gas to recirculate.

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Heat exchangers

For the compressor operate in an efficient way, the temperature ofthe gas should be low. The lower the temperature is the less energywill be used to compress the gas for a given final pressure andtemperature. However both gas from separators and compressedgas are relatively hot. This ends up as a temperature increase.

Temperature exchangers of various forms are used to cool the gas.Plate heat exchangers consist of a number of plates where the gasand cooling medium pass between alternating plates in opposingdirections. Tube and shell exchangers place tubes inside a shellfilled with of cooling fluid. The cooling fluid is often pure water with

corrosion inhibitors.

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Scrubbers and reboilers

The separated gas may contain mist and other liquid droplets. Liquiddrops of water and hydrocarbons also form when the gas is cooledin the heat exchanger, and must be removed before it reaches thecompressor. If liquid droplets enter the compressor they will erodethe fast rotating blades. A scrubber is designed to remove small

fractions of liquid from the gas.

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Compressor anti surge and performance

Several types of compressors are used for gas compression, eachwith different characteristics such as operating power, speed,pressure and volume:

1. Reciprocating Compressor . Used for lower capacity gascompression and high reservoir pressure gas injection.

2. Screw compressors. Two counter rotating screws with matchingprofiles provide positive displacement and a wide operating range.Typical use is natural gas gathering.

3. Axial blade and fin type compressors with up to 15 wheels providehigh volumes at relatively low pressure differential (discharge

pressure 3-5 times inlet pressure), speeds of 5000-8000 rpm, andinlet flows to 200.000 m3/hour. Applications include aircompressors and cooling compression in LNG plants.

4. Centrifugal compressors (for oil and gas)

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Satellite platform

Conductor support systems, also known as conductor supportedsystems or satellite platforms, are installations which are smallunmanned platforms consisting of little more than a well bay, and asmall process plant. They are designed to operate in conjunctionwith a static production platform which is connected to the platform

by flow lines and/or by Umbilical cable.

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7.4 Floaters

The original neutrally buoyant floating structures are ships andbarges and these vessels are subjected to substantial heave, pitchand roll motions detrimental to offshore operations in intermediate toharsh environment. Considering the green water on the deck andthe undesirable motions. an innovation was introduced to separate

the deck from the vessel and keep the major portion of the vesselbuoyancy away from the water surface. This gave rise to theinnovation of semi-submersible. The three-column Sedco 135 semi-submersible is a good example of not only precluding green waterand minimising motions but also providing adequate positive stability

through the use of large-diameter legs far enough apart.

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Example of Topside Side Elevation

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Spar DTU

A spar is a deep-draft floating caisson, which is a hollow cylindricalstructure similar to a very large buoy. Its four major systems are hull,moorings, topsides, and risers. The spar relies on a traditionalmooring system (that is, anchor-spread mooring) to maintain itsposition. About 90 percent of the structure is underwater.

Historically, spars were used as marker buoys, for gatheringoceanographic data, and for oil storage. The spar design is nowbeing used for drilling, production, or both. The distinguishingfeature of a spar is its deep-draft hull, which produces very favorablemotion characteristics compared to other floating concepts. Low

motions and a protected centerwell also provide an excellentconfiguration for deepwater operations. Water depth capability hasbeen stated by industry as ranging up to 10,000 ft.

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Spar DTU
http://www.globalsecurity.org/military/systems/ship/images/spars-image3.jpg

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Semi submersible

A semisubmersible or semi-submersible is a marine vessel that isconfigured with large buoyant pontoon structures below the watersurface and long columns through the water surface supporting aplatform at a significant height.

Such a vessel may be able to transition from a deep to a shallow

draft by deballasting (removing water ballast from the hull), andthereby become a surface vessel. The heavy lift vessels use thiscapability to submerge the majority of their structure, locate beneathanother floating vessel, and then deballast to pickup the other vesselas a cargo.

With its hull structure submerged at a deep draft, thesemisubmersible is less affected by wave loadings than a normalship. With a small water-plane area however, the semisubmersibleis sensitive to load changes, and therefore must be carefullytrimmed to maintain stability.

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Semi-submersible Crane vessels (SSCV)

These semi-submersible crane vessels (SSCV's) consist of twolower hulls (pontoons), three columns on each pontoon and anupper hull. During transit an SSCV will be de-ballasted to a draughtwhere only part of the lower hull is submerged. During liftingoperations, the vessel will be ballasted down. This way, the lower

hull is well submerged. This reduces the effect of waves and swell.High stability is obtained by placing the columns far apart. The highstability allows them to lift extreme high loads.

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Floating Storage Off Loading (FSO)

Floating storage and offloading units (FSO) are used worldwide bythe offshore oil industry to receive oil from nearby platforms andstore it until it can be offloaded onto oil tankers. A similar system,the floating production storage and offloading unit (FPSO), has theability to process the product while it is onboard. These floating units

reduce oil production costs and offer, mobility, large storagecapacity, and production versatility.

These units are usually moored to the seabed through a spreadmooring system. A turret-style mooring system can be used in areasprone to severe weather. This turret system lets the unit rotate to

minimize the effects of sea-swell and wind.

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7.4.1 Floating Storage Off Loading (FSO)

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7.4.2 Floating Production Storage Off Loading(FPSO)

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7.5 TENSION LEG PLATFORM (TLP)

A Tension-leg platform or Extended Tension Leg Platform (ETLP) is avertically moored floating structure normally used for the offshoreproduction of oil or gas, and is particularly suited for water depthsgreater than 300 metres (about 1000 ft) and less than 1500 meters(about 4900 ft). The platform is permanently moored by means of

tethers or tendons grouped at each of the structure's corners. A groupof tethers is called a tension leg. A feature of the design of the tethersis that they have relatively high axial stiffness (low elasticity), such thatvirtually all vertical motion of the platform is eliminated. This allows theplatform to have the production wellheads on deck (connected directly

to the subsea wells by rigid risers), instead of on the seafloor.

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7.5 TENSION LEG PLATFORM (TLP)

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Mobile platform

Mobile offshore drilling unit (MODU) Offshore drilling typically refers to the discovery and development of

oil and gas resources which lie underwater through drilling a well.Most commonly, the term is used to describe oil extraction off thecoasts of continents, though the term can also apply to drilling in

lakes and inland seas
http://en.wikipedia.org/wiki/Oilhttp://en.wikipedia.org/wiki/Oil

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Mobile platform

Mobile offshore production unit (MOPU) The MOPU comprises the hull and topside facilities. The hull

includes all facilities and equipment that would normally be suppliedwith a mobile jack-up unit including jacking systems, legs,foundations, accommodations, helideck and utilities. The topsides

facility will include all equipment required for processinghydrocarbon fluids from the reservoir.

The topsides facility will contain processing equipment to separate,measure, dehydrate, and sweeten the raw gas. Acid gas and waterhandling equipment will also be installed on the MOPU

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Mobile platform

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Sub-sea facilities

Sub Sea Test Tree (SSTT) The purpose of the sub sea test tree (SSTT) is to provide a primary

safety system to control tubing pressure and to provide a means torapidly and safely disconnect from the well should adverseconditions occur. All of the major testing contractors have sub sea

test tree safety systems and various configurations exist to suit therequirements of the planned operation. In common, all sub sea testtrees consist of two valves for control of tubing pressure. These maybe either independent dual ball valves or an independent ball.

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DPV2043 Week Unit7

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