Oil&Gas Tech - Offshore

7/28/2019 Oil&Gas Tech - Offshore

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A THERMIE PROGRAMME ACTION

Oil and Gas Process TechnologyThe latest advances for use on offshore production installations

European Commission

Directorate-General for Energy (DG XVII)


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THE THERM IE PRO G RA M M E

THERMIE is an important European Community instrument, designed to promote greater useof innovative energy technologies developed in Europe. THERMIE is a five year programme(1990-1994) contributing approximately 150 MECU each year.

The main aims of THERMIE are to:

promote innovative energy technologies; disseminate information on these technologies; encourage greater use of new and renewable energy sources; improve energy efficiency; improve environmental protection.

THERMIE has been developed from previous Community programmes and providesenhanced provision for:

co-ordination with complementary programmes in Member States; extensive dissemination of proven technologies; evaluation, follow-up, dissemination and co-operation; co-operation with non-member countries;

consideration of environment and safety within eligibility criteria; liaison with key intermediary bodies within Member States to aid promotion of innovation.

The THERMIE programme covers a wide range of technologies for the production,transformation and use of energy. These are:

rational use of energy in industry, buildings and transport; renewable energy sources including energy from biomass and waste, thermal and

photovoltaic solar energy, wind, hydroelectric and geothermal energy; solid fuels, use of gaseous, liquid and solid wastes and gasification with a combined cycle; hydrocarbons; their exploration, production, transport and storage.

THERMIE PublicationsA key element of the THERMIE programme is the enhanced dissemination of informationrelating to proven measures. This information is brought together in a wide range ofpublications. These provide an invaluable source of information for those wishing to appreciatethe current state of the art within particular technologies.

THERMIE Colour CodingTo enable readers to quickly identify those publications relating to specific parts of theTHERMIE programme, each will be colour coded with a stripe in the lower right hand corner ofeach document, i.e.:

RATIONAL USE OF ENERGYRENEWABLE ENERGYSOLID FUELSHYDROCARBONS


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4. HEA T EX C HA N G E 7

4.1 C o m p a c t Exc ha ng e rs 8

4.2 M o d ula r Exc ha ng e rs 9

4.3 Up ra ting Existing Exc ha ng e rs 9

5. G A S TREA TM EN T 9

5.1 IFPEX O L 95.2 Hig e e 10

5.3 M e m b ra ne Te c hno lo g y 11

5.4 Enha nc e d O il Re c o ve ry 12

6. PRO DUC ED W A TER TREA TM EN T 12

6.1 Hyd ro c y c lo ne s 12

6.2 Flo ta tio n C e lls 13

6.3 Ele c tro - c o a le sc e rs 14

6.4 W a te r Tre a tm e nt M e m b ra ne s 14

7. IN JEC TIO N W A TER TREA TM EN T 14

7.1 Fib re Filte r 15

7.2 Filto m a t 15

7.3 So lid / liq uid Hy d ro c y c lo ne s 16

8. G A S C O M PRESSIO N 16

8.1 Re g e ne ra tive C irc ula to r 17

9. M ULTIPHA SE PUM PIN G 17

10. DRILLIN G FLUIDS 17

11. C O N TRO L A N D IN STRUM EN TA TIO N 18

11.1 M e te ring 18

11.2 A uto m a tio n 18

11.3 The PLA TIN E Pro je c t 19

Reproduction of the Contents is Subject to Acknowledgement of the European

Commission.

Neither the European Commission, nor any person acting on its behalf: (a) makes anywarranty or representation, express or implied, with respec t to the informationcontained in this publication; (b) assumes any liability with respect to the use of, or

damage resulting from this information.

The views expressed in this publication do not necessarily reflect the views of theCommission.


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1. INTRODUCTIONAny study of process technology for offshore applications has to be set within the frameworkof probable future developments. This publication examines the existing offshorehydrocarbon reserves of the European Union (EU) Member States and Norway, and identifiesthe developments likely within the next ten years. The new European processing technologieswhich are available are assessed in relation to the oil and gas discoveries previously analysed.

From the data available the majority of finds are in the United Kingdom Continental Shelf

(UKCS) North Sea (NS) sector. However, many of the largest undeveloped fields in the NorthSea are in Norwegian waters. The majority of UKCS NS finds awaiting development arerelatively small, with less than 30 million barrels of recoverable oil. It is unlikely that manylarge UKCS NS fields are still to be discovered.

In contrast, the UK North West Atlantic area currently has three large fields waiting to bedeveloped and since the area is less well explored, there may be additional discoveries to bemade.

In comparison with the UK and Norway, the other European countries have significantlysmaller and fewer fields awaiting development. Consequently, UK and Norwegian fields willhave the greatest influence on developments requiring new technology.

In most process technology areas there are already new available technologies which couldcut costs by reducing plant size or maintenance requirements. The aim of this study is toevaluate recent technologies, providing sufficient detail to allow potential operators, theirconsultants and contractors to appraise the applicability of the equipment to their ownsituation, either as part of a new installation or as a retrofit system.

2. OFFSHORE HYDROCARBON DISCOVERIES

2.1 Oil ReservesThis section examines known offshore discoveries and aims to identify likely developmentswithin the next ten years. It covers the UKCS and Norwegian sector of the North Sea, which

represent the majority of discoveries. It also considers the Danish, German and Dutch sectorsof the North Sea and Irish waters, plus the Spanish, Italian and Greek sectors of the

Mediterranean Sea. Most fields in these latter sectors are expected to be less than 1,600 m3/d

(10 MBOPD) with only a few exceeding 3,200 m3/d (20 MBOPD). A summary of oildiscoveries in all sectors is shown in Fig 1.

Fig 1 Oil discoveries - all sectors

Since the UK and Norway dominate in offshore activities, they will have the greatest impacton technological developments. A summary of UK and Norwegian oil discoveries is shown inFig 2.

Fig 2 UK and Norwegian Oil Discoveries

The largest NS fields have already been exploited or are under development. Smaller fieldsand those which are more difficult to exploit have been deferred until they becomecommercially attractive. The UK has discoveries in the North Western Atlantic, thedevelopment of which has been delayed due to lack of infrastructure and high cost.

Most fields waiting development are less than 5 million m3 (30 million barrels) of recoverable

oil, with daily production rates peaking at around 2,400 to 3,200 m3/day (15 to 20 MBOPD).Subsea tiebacks are likely to be the most viable development option. Floating production


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systems (FPS) are possible for higher production rates of say 3,200 to 8,000 m3/day (20 to 50MBOPD).

Larger throughputs of 6,400 m3/day (40 MBOPD) and above could be commercial using jacketsupported platforms. These rates are indicative, since subsea could be appropriate for muchlarger throughputs if the infrastructure is adequate. However, subsea developments could beuneconomic if they are too far from a host facility and flowlines are too expensive. Highflowline costs could make the FPS option more attractive at lower throughputs.

Fig 3 shows a distribution curve for oil discoveries and indicates the most likely form ofdevelopment for the different field sizes.

For the UKCS, larger developments requiring conventional facilities could total ten within thenext decade, including West of Shetland. Some discoveries will be aggregated to make themviable. For example, eight fields are proposed for co-development through a centralproduction facility in BPs Eastern Trough Accumulation Projects (ETAPS). With ETAPS,satellite fields will be subsea tiebacks or unmanned wellhead jackets.

West of Shetland and in the deeper, colder waters of Northern Norway, fields are large butremote and other technologies such as tension leg platforms and semi-buoyant structures maybe required. Thus, whilst the number of large fields may be low, they will be dependent onnew technology to enable equipment and deck weights to be minimised.

2.2 Gas ReservesA summary of gas discoveries for all sectors is shown in Fig 4 and for the UK and Norway inFig 5.

Most fields are in the marginal economics category. The average field size is less than 2 MM

m3/day, with few at 10 MM m3/day or above. Half of a total of seventy-eight were less than

2 MM m3/day and minimum facilities wellhead platforms will be the likely means of

development. A further thirteen fields listed were thought to be less than 1 MM m3/dayoutput. For viable development they would need to be either part of a group development or

tied back to an existing facility through a subsea or minimum wellhead facility.

Fig 6 shows a gas find distribution curve and indicates the most likely form of developmentfor the size.

Large standalone discoveries have been made West of Shetland and there may be more in thatarea. However, they will be difficult to develop due to deeper waters and absence of majorexport pipeline systems.

2.3 New Equipment and ProcessesSeveral areas of process technology for the offshore industry have been improved in the past

ten years including separation by cyclonic devices and filtration. In addition, membranes havebeen developed which allow automation and reduced manning for a range of applications.

Many new equipment forms are modular, allowing higher throughputs by adding extramodules. Basic module sizes are adequate for most future developments, that is 1,600 to 3,200

m3/d (10 to 20 MBOPD) but at high throughputs modularization becomes less attractive.However, high volume fields are less likely to require new technology since they are moreviable.

In the following sections various equipment types are examined. These include:


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Improved coalescence devices have been developed and tested. These include NATsdevelopment of the EPIC high voltage, high frequency pulsed DC electro-coalescers, whichare based on experimental work by Bradford University.

Normally, electrostatic demulsifiers use high DC currents and are limited by the watercontent of the fluid. At high water content the fluid conducts. The new DC system usesinsulated electrodes enabling it to operate at high water cuts.

EPIC is a non-invasive, non-polluting system and has been successfully tested by BP on theWytch Farm field. A pulsed high energy field applied across the emulsion breaks stable waterin oil emulsions in minutes. Tests have shown separator performance improvements of up to400%. EPIC enables separators to be smaller, improves the performance of existing vesselsand reduces the need for chemical demulsifiers.

3.5 Separation on Floating FacilitiesOne problem of conventional separators is that their performance suffers when used onfloating production vessels. Research on the affects of motion on separation includedassessment of various types of internal baffles to restrict wave motion and sloshing. Motionaffects are now broadly understood and vessels can be designed with lower contingency.Cyclonic and centrifugal devices described in section 3.1 should be unaffected by motion.

A more conventional type known as the Endecottseparator (Fig 10) was tested by the BHRGroup at Cranfield and shown to be effective against wave movements.

The separator has a low footprint area and minimises carry over and carry under which resultfrom sloshing. It comprises two horizontal drums, one above the other and inter-connected byseveral riser tubes. The tubes are of relatively small diameter which reduces wave effects inthat area. The oil and water interface occurs in the riser tubes.

4. HEAT EXCHANGEShell and tube exchangers have changed little over the past forty years. Thermal design is

more sophisticated allowing less "safety margin". However, fouling factor data remainslimited and is conservative. It leads to larger designs than needed which gives low fluidvelocities and contributes to fouling.

For offshore applications, space and weight present problems for shell and tube exchangers.Other exchanger types have been considered but there is a reluctance to use unproven types.Compact exchangers have been used for many years onshore for LNG and low temperaturechillers but have not been widely used for offshore oil and gas. LNG is a clean fluid, wherecontaminants that may deposit in the exchanger have been removed. Compacts are now beingused for compression cooling.

New baffle types allow easier installation and cleaning as well as greater thermal efficiency.They include the Spiral Flow Shell and Tube Heat Exchanger (SFHE) developed by Norsk

Hydro,and the VUCHZ (Czechoslovakia) Helixchanger.These combine familiarity with somesavings.

In other process industries, including LNG and oil refining, there is interest in thermalefficiency typified by Pinch technology and integration of thermal duties. However, there hasbeen little interest offshore because there is usually excess process heat.

4.1 Compact ExchangersCompact exchangers such as platefin, Heatric, spirally wound etc, have high heat exchangearea-to-volume ratios, enabling them to be much lighter than conventional exchangers. They


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can be used in standard two fluid applications but are more effective in multistream duties,with up to seven streams heat exchanged.

Multistream compacts have not been used offshore because two stream exchangers areusually adequate. They could be used for gas compression, low temperature separation (LTS),dephlegmators and refluxing condensers.

Platefin exchangers are constructed of aluminium and limited in pressure, temperature and

corrosion service. Alfa-Laval/Rolls-Royce and Heatric have developed diffusion bondedexchangers which are similar to platefins. However, they have higher temperature andpressure capabilities with better corrosion performance, which has been achieved by usingstainless steel and titanium.

Heatric units (Fig 11) have already been used for offshore gas treatment plant. The advantagesinclude high efficiency, close temperature approach and low fluid inventory. They offer costsavings where expensive materials are required. Fouling can be a problem since they havenarrow passages and are not easily cleaned. However, fouling can be reduced by maintaininghigh velocities and tests have shown this to be the case.

The manufacturers claim 25 times more heat transfer area than shell and tube heat exchangersof the same size and weight. In addition, there are no heat affected zones which are

detrimental to strength and corrosion resistance characteristics.

More conventional exchangers including gasketed and welded plate types are used offshoreto 20 bars and 60-70 bars respectively. Heatric and Rolls-Royce/Alfa-Laval exchangers usesimilar configurations but 200 to 300 bar pressures can be withstood by diffusion bonding.

Spirally wound exchangers have been in cryogenic use for many years. They are made inmany materials including stainless steel, are capable of withstanding very high pressures andare amongst the largest exchangers which have been built.

Their main advantage over other compacts is that the tubeside pressures can be as high asthose achieved with conventional shell and tube exchangers, eg in excess of 300 bars. Since the

tubes can be configured in a variety of materials they can be used in corrosive service. Thespiral format allows operation over a wide temperature range since tubeside thermalexpansion is accommodated in the structure. They are probably the most flexible exchangersfor a wide operating range.

4.2 Modular ExchangersModular exchangers offer construction advantages, that is standard units can be linked inparallel or series or combinations to suit standardisation requirements. Spares can be reducedby simplifying stock control. TRANSON is a standardised modular construction allowing achoice of materials. The tube bundle is fitted with a spiral baffle which reduces the fouling bydecreasing dead spots in the shell. The modular components are such that the units can beassembled to allow efficient use of space.

TRANSON claims savings in heat transfer area, unit size, weight and cost, based on areduction in fouling factor and standardisation.

4.3 Uprating Existing ExchangersTubular heat exchanger performance is enhanced by inserting a static mixing device inside thetubes which shears and mixes the fluid. In tubular systems, frictional drag at the wall creates avelocity profile with maximum flow at the centre. Heat transfer is controlled by the filmcoefficient at the tube wall. The device reduces the velocity gradient across the tube givinguniform temperature and velocity over the cross section of the tube.


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Cal Gavin Ltdoffers a range of inserts known as HiTran.Shorter residence time at the wallreduces fouling for heat sensitive fluids. Tubes remain cleaner and in service longer and heattransfer is improved.

Experimental studies on HiTran with a light Arabian crude showed that the level of foulingwas less than that of a conventional tube and the heat transfer coefficient was increased byabout 40%.

5. GAS TREATMENTOffshore gas treatment includes gas sweetening, dehydrating and hydrocarbon dewpointing.There are established technologies in the industry but newer technologies are available whichcould result in savings.

5.1 IFPEXOLIFPEXOL (Fig 12), developed by Institut Franais du Ptrole, is used to treat natural gas,providing an integrated unit which performs a number of process operations including gasdehydration, NGL extraction and gas sweetening. The process uses freeze point depression ofa methanol solvent, enhancing its affinity for water absorption.

IFPEX-l (for dehydration) and IFPEX-2 (for sweetening and hydrocarbon recovery) may becombined as a unit or used separately. The system is claimed to offer benefits over tri-ethylene glycol (TEG) and enhanced variants, since IFPEXOL is environmentally friendly andthe chemicals and plant are low cost. The processes can also be split to allow satellite andmain platform operation. Figs 13 and 14 show the basic arrangement of the processes.

In comparison with conventional systems, IFPEX-1 offers weight and space savings. It doesnot require a large stripping column for the recovery of methanol as only a fraction of the feedgas needs to pass through the IFPEX-1 column to achieve methanol recovery. Unlike TEGthere is no regeneration skid, saving on space and energy requirements.

It is claimed that IFPEXOL can save up to 30% on capital costs, in addition to its savings on

weight and space.

5.2 HigeeHigee(Fig 15) was originally developed by ICI but is now owned by the Glitsch Corporation.It is a rotating mass transfer device; that is equivalent to a packed tower in which the packingrotates. Fluids to be separated or absorbed are forced radially through a rotating packing.Rotation enhances gravity allowing the apparatus to be more compact. It can be used fordehydration and sweetening.

The unit size is approximately a tenth of conventional systems but some savings would belost since surge capacity is required.

For gas treatment systems, gas enters through a nozzle located at the periphery of the casing

cylinder and travels through the rotating packing into the centre from which it exits the unit.Scrubbing liquid is introduced through the central axis and is sprayed on to the rotatingpacking. The centrifugal forces drive the liquid droplets out to the periphery where they draindown at the wall of the unit. The gas and liquids interact as they flow countercurrent throughthe devices.

The capital cost savings over conventional units are small but weight and space savings can besignificant for offshore developments. The cost savings assume that each design ismanufactured in carbon steel. If more exotic materials or higher operating pressures arerequired the savings will be higher since smaller diameters and thinner wall thicknesses areachievable with the Higee system.


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5.3 Membrane TechnologyMembranes can be used for various aspects of oil and gas processing such as gas separation,dehydration, oily and injection water treatment. They are extensively used in water treatment(Fig 16). The selectivity of membranes is improving and the range of applications is widening.Membranes are thin barriers which allow preferential passage of particular materials throughthe structure. Membranes permeate gases at differing rates, for example C02 permeates up to

40 times faster than methane.

The most widely used gas membranes partition oxygen and nitrogen, or remove C02, H2S

and/or water from hydrocarbons. The latter is the main application of membranes forhydrocarbons processing. They are still in development but have established wide acceptanceonshore through attributes which make them ideal for offshore use. However, there areproduct losses which can be reduced by recycle compression. Some 150 units are installedonshore for water and acid gas removal but few are installed offshore.

Membranes have several advantages over other systems including:

low capital cost which derives from their basic simplicity; ease of installation - they are modular and skid mounted and there are usually only three

connections necessary to connect up a unit; weight and space savings - at low throughputs they are smaller than alternative processes

- and can be configured to suit the available space; they have no moving parts (unless a compressor is used to recycle gas to increase product

recoveries or improve purities) allowing them to operate as automated units and withlimited maintenance crews;

they have low environmental impact since no chemicals are circulated; they can work with no power or utilities but it may be beneficial to use gas cooling or

heating to precondition a stream as this can increase efficiency and improve membranelife.

Membranes have recently been developed to separate heavy hydrocarbons from lighterfractions. This should enable capital and operational cost savings for hydrocarbon dewpoint

and calorific value control plant.

5.4 Enhanced Oil RecoveryMembranes have been used onshore for Enhanced Oil Recovery (EOR), for example thereinjection of C02 or N2. When these gases are injected into the reservoir they dissolve into the

in situ oil, which becomes less viscous and more mobile. The produced fluids will contain C02and/or N2. These gases can be separated from hydrocarbons by membrane and recycled for

reinjection.

To date, no gas injection EOR has been applied offshore in the UKCS and EC, but it isstandard onshore practice in the USA. Earlier studies on gas injection EOR schemes for NorthSea application failed because conventional plant was large and expensive and additional oil

recoveries were uneconomic. In part this was due to high purity specifications for injectiongas which increased plant size and complexity.

Membrane or membrane in combination with conventional systems could produce moreeconomic plant designs for EOR. One of the principal forms of EOR is the injection ofnitrogen, which is usually produced by cryogenic distillation but can also be produced bymembranes, if product purities are relaxed.

6. PRODUCED WATER TREATMENT


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Water treatment for injected and produced water has previously proved problematic.Traditional units such as flotation cells for produced water and dual media filters for injectedwater are heavy and bulky. In the case of produced water, several have failed to achieveconsistent statutory residual oil levels.

Several methods of water treatment have been developed including cyclonic separation,reinjection of produced water, electro coalescers, rotating cyclones and water injectioncyclones. There have also been improvements in flotation cell technology though these remain

large. The most notable improvement has been cyclonic separation using hydrocyclones.

6.1 HydrocyclonesThere are several types of oily water hydrocyclone available including Dynaclean, Vortoil andOilspin. They are modular and can be manifolded to provide greater capacity. Modularisationenables flexibility to turndown conditions but adds complexity of valving and piping.

Oilspin consists of banks of hydrocyclones mounted within a pressure vessel which allowsturndown or capacity increase as required.

Both Oilspin and Vortoil use similar methods of operation. Produced water is fed into the unitvia a tangential inlet, which produces a high fluid spin within the cyclone head. A vortexingcore is formed by the spinning action, which allows migration of the oil droplets from the bulk

of the liquid to the central core. Geometry and pressure settings of the cyclone tube cause anaxial reversal of the central oil core. The lower density of the oil rich phase permits removal ofthe stream from the rear of the tube, while the bulk of the liquid is pushed forward and out ofthe tube. As in a conventional unit, the efficiency improves with increasing oil droplet sizeand increasing differential density between the two liquid phases. Oilspin and Vortoil requireuse of a downstream degasser vessel to disengage residual gas from the water in a similarmanner to standard systems.

Dynaclean (Fig 17) is a more recent development of a water deoiling hydrocyclone. Originallydeveloped by Neyrtec, with sponsorship from the European Commission and Total, it hasbeen designed specifically for application offshore. Unlike regular cyclones Dynacleanproduces a vortex by rotating the cyclone tube. The system has good de-oiling characteristics

without the requirement of high velocity and turbulence.

Application of the Vortoil hydrocyclones for deoiling of produced water has been widespreadsince the mid 1980s. They generally require high feed pressures, which necessitates feedpumps to boost the inlet pressure as field pressures decline. Pumping of the feed stream isundesirable as shearing of the oil and water phases may occur. Peristaltic pumps have beenused to overcome fluid shear. The hydrocyclone may be used upstream of productionseparators for preseparation for fields with increasing water cuts.

6.2 Flotation CellsConventional induced gas flotation (IGF) units are bulky and heavy. The Serck Baker InducedGas Flotation unit is relatively smaller but is still a large item. However, it provides moreconsistent operation.

It comprises four active cells in series with combined inlet and outlet compartments. Inducedgas removes residual oil from the water. Oily water enters under pressure and passes alongthe bottom of the vessel; this allows break out of free oil in the inlet compartment and firststage of separation. Underflow of the water avoids disturbance of the natural flow of oildroplets to the surface. The cells are fitted with a system to induce gas from the top of thevessel dispersing it as microbubbles into the water, mechanically mixing the oil and gas. Theoil droplets attach to the gas bubbles, enhancing their buoyancy and rise rate.

The induced gas flotation unit has several unique features:


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it is a non-motorised, self-adjusting, floating oil skimming arrangement;

the unit is cylindrical which requires less sealing - it is gas tight and suitable for sourwater.

6.3 Electro-coalescersOne problem with hydrocyclones is their sensitivity to inlet pressure. Earlier types required

drive pressures of around 7 bar g (100 lb/in2g). At lower pressure there was insufficientenergy (pressure drop) to allow separation. Water pressure can be increased by pumping.This shears the oil particles reducing their size and making cyclones less efficient in coalescingthe oil. Upstream electro coalescers can increase the oil droplet size entering the cyclone,thereby making separation in the hydrocyclone easier and at lower pressures. The operatingrange of the hydrocyclone is therefore increased.

6.4 Water Treatment MembranesThere has been considerable testing of produced water membranes. Tests indicate that theycan be used where particle sizes are too small for cyclonic devices. If oil in water dischargelevels are further reduced to below the currently required 30ppm, or soluble oil is included,they may become necessary for future platforms.

Several crossflow membrane filter systems are available for deoiling. Some have automatedbackwashing capability, others include chemical cleaning. However, cleaning can be timeconsuming. While most rely on crossflow operation some require a dynamic layer, that is aprecoat of larger particles which improves the efficiency of the filter.

Hydrocyclones, traditional filters and flotation cells are only able to remove particulatematerials. Membranes are able to remove between 20% and 50% of dissolved oil. However,they are relatively expensive compared to hydrocyclones.

7. INJECTION WATER TREATMENTNew processes and equipment have been developed for sea water injection purposes,particularly filters and solid-liquid hydrocyclones for removal of larger particles prior todownstream filtering to reservoir specifications.

Injection water requirements have changed recently. Previously operators required treatedwater to have oxygen contents of less than 5 parts per billion (ppb) and removal of 98% ofsolid particulate above 2 microns size. Some have retained these specifications but others haveallowed them to be relaxed, resulting in a marked effect on the size and operability of units.

7.1 Fibre FilterA filter developed by BP and marketed by Kalsep, incorporates fibres which are compressedfor filtration and expanded for back flushing. Compression is achieved by a twisting action

which brings fibres closer together. Prior to back flushing, fibres are twisted in the oppositedirection becoming separated. Compressed, the fibres trap particles greater than 5 microns;uncompressed, in back wash mode, the filter gap increases to 200 microns allowing theparticles to escape. The Fibrotex filter is shown in Fig 18.

The filter offers a more efficient method of filtering than that provided by the traditionalparticulate removal, backwash filters. The unit has the following features:

water quality comparable with sand filters, that is 98% removal of all particles over 5microns;

it is fully backwashable but consumes 80-90% less backwash than conventional filters;


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the unit is very compact and fully transportable; backwash takes a matter of minutes compared to 40-50 minutes required for multimedia

or sand filters; it can be used as a single throughput unit or operated in series or parallel; installation and commissioning times are minimal.

7.2 FiltomatAtkins Fulford has a range of filters, named Filtomat, which are self-cleaning and allowcontinuous operation: standard Filtomat; Filtomat MCF; and Filtomat Thread.

The standard filter comprises three chambers:

coarse strainer; fine strainer; rinse.

Water is passed through the filter causing build-up of solids on the fine strainer. This isaccompanied by an increase in pressure drop across the screen. At a pre-set pressure drop, thefilter commences the cleaning cycle.

In the MCF version cleaning is continuous. This overcomes problems of high suspended solidlevels and rapid reverse side screen blockage. The cleaning mechanism is similar to the basicunit except that the dirt collector is constantly rotating, allowing high dirt loads at lowerpressure drops.

The Thread Filteris capable of removing 98% of suspended solids above 2 microns. The filtermedium is a textile thread wound parallel onto a rigid plastic surface forming a cassette (Fig19). A number of cassettes are manifolded in a vessel to provide the liquid flow capacityrequired.

Liquid passes from the outside of the medium to the inside. The dirt is trapped on both the

face and inside the medium (Fig 20).

The cleaning cycle is performed by high pressure water jets in the direction of the main flow.Design of the jets and the filter medium allow a significant quantity of jetted water to passthrough the thread layer, hit the rigid plastic surface and be propelled backwards through themedium to form a local backflush. The process provides a highly efficient method of cleaningthe filter (Fig 21).

7.3 Solid/Liquid HydrocyclonesSolid/liquid hydrocyclones, such as those manufactured by Richard Mozley Ltd, can be usedto remove solids from injection water and oil from drilling muds and sands. The operation ofthe solid/liquid hydrocyclone is much the same as its liquid/liquid counterpart.

Hydrocyclones are a more compact and efficient solution for solids removal from injectionwater than the traditional filtration methods (Fig 22). They are typically one tenth of theweight and size of conventional units. Development of the units for offshore operations iscontinuing, but already the equipment has shown considerable promise as an alternativemethod to filtering.

8. GAS COMPRESSIONThere are few major advances in compression technology which would lead to significantlysmaller units. Improvements in sealing and bearing arrangements have been made, inparticular the use of magnetic bearings. These have limited effects on capital expenditure and


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weight and space, but allow reduced maintenance and intervention. Dry seals have reducedspace and weight requirements by eliminating associated equipment such as degassing plant.

8.1 Regenerative CirculatorBertinand Ciehas developed the Gastight Regenerative Circulator.It is described as being aconcept between centrifugal compressors and volumetric compressors which allows highpressure ratios to be developed at low flowrates. The originators identify recirculatingregeneration gas for molecular sieves as an application. The compressor is claimed to be

cheaper, simpler and more reliable than other options. Casing pressures are higher than forROOTS type machines, that is up to 110 bar, as opposed to 30 to 40 bar for the latter. Therange of applications offshore could be limited. Apart from circulating regeneration gas theconcept might be used for low volume interstage compression.

9. MULTIPHASE PUMPINGMultiphase pumps have been under development for several years. These include the rotatinggear pumps developed by Multiphase PumpingSystems, which have been extensively tested.Bornemann of Germany has also developed similar pumps.

Multiphase pumping will be a niche market applied to smaller oil fields, delivering oil and

gas to a central facility. The satellite is likely to be less than 8,000 m 3/d (50 MBOPD). At largersizes it would probably be commercially viable to have separation facilities, unless the satelliteis very close to the host platform. The closer the host facility and satellite, the less is thenecessity to pump multiphase.

In general, multiphase pumping will not provide significant savings of topsides weight orcost, compared with separator and conventional pump combinations, when associated gas canbe flared. It could give savings if the associated gas has to be separately piped to anotherfacility, which would entail the cost of a compressor and the additional line. However, if themultiphase line has to be in a more expensive material due to acid component levels in the gasphase, there may be no saving.

BHR Group has developed a jet booster which allows multiphase pumping and compression

in combination with a centrifugal pump. The centrifugal design works by recirculating someof the liquid phase, thereby reducing the fractional gas rate. Additionally, there is thePoseidon pump which is marketed by Sulzer. This is described in more detail in aTHERMIE maxibrochure on multiphase technologies.

10. DRILLING FLUIDSDrilling fluids systems are not usually perceived as part of the process package. However,significant developments have been made in powder handling, mud mixing and cementmixing. In the case of powder handling and conveying, powder losses and unit sizes andweights can be reduced by low pressure fluidisation. A few platforms have applied some ofthe techniques.

In the case of mixing, there is potential to reduce mixer size and batch quantities stored, whichwould have a marked effect on platform operating tonnages. This can be achieved throughstatic in-line mixers (Alval),which can also produce a more consistent product than the usualmix tank method which requires residence time for conditioning. Little use has been made ofthis technology.

Additionally, since residual oil levels allowed in cuttings have been reduced, there have beenimproved methods for the cleaning of cuttings, including solvent washing and centrifuging.This combination enables residual oil to be reduced to less than 1% by weight.


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The drilling fluid handling facilities could be significantly improved by better processengineering.

11. CONTROL AND INSTRUMENTATION

11.1 MeteringMultiphase metering is useful as it reduces the need for test separators and test lines.

The Starcut Water Monitorwas developed by Texaco and marketed by Jiskoot Autocontrols.It is field proven, using microwaves to provide reliable, accurate measurements of 0-100%watercut in the presence of free-gas. It is capable of unattended and remote operation inhostile environments. It can be used for watercut tests at wellheads, wet-oil transportpipelines and from separators.

Other multiphase meter developments include the Fluentameter and a new meter under testfrom the BHR Group (see Section 9).

11.2 AutomationProcess automation can enable a topsides facility to operate either unmanned or withminimum staffing. Remote control of facilities requires minimal operation and maintenance.

There is no single factor which allows automation to be achieved. Improvement of reliability,sensing and controlling equipment and improvement in the reliability of rotating machineryare the main factors in meeting the objective. In the case of sensing equipment, 60% of failuresare caused by human intervention either through operations or maintenance. A further 30%result from poor packaging. Only 10% are due to random component failure.

The following points summarise an approach towards the achievement of unmannedfacilities:

simplification and minimisation of systems and equipment; minimisation of moving parts; minimisation of dependency on auxiliary systems; optimisation of pressure energy in the well fluids; installation of standbys for equipment subject to failure; over-sizing of equipment to improve reliability; utilisation of minimum or low maintenance equipment.

11.3 The PLATINE project

The PLATINE project, supported by the EC THERMIE programme, was initiated in 1986 withthe objective of developing an unmanned production platform which was able to operateremotely from a control location onshore (Fig 23). The project aimed to find viable means ofimproving the profitability of field developments, particularly to reduce operating costs andincrease productivity.

The project covered a number of areas including the well safety system, gas lift optimisation,and safety and surveillance.


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OPETThe Organisations for the Promotion of Energy Technologies (OPETs)Within all Member States there are a number of organisations recognised by the EuropeanCommission as an Organisation for the Promotion of Energy Technologies (OPET). It is therole of these organisations to help to coordinate specific promotional activities within MemberStates. These may include staging of promotional events such as conferences, seminars,workshops or exhibitions as well as the production of publications associated with the

THERMIE programme.

Members of the current OPET Network are:

ADEME - Agence de lEnvironnement et la Maltrise de lEnergie 27, rue Louis Vicat, F- 75015PARISTel: 33-1-47.65.20.21/56. Fax: 33-1-46.45.52.36

ASTER - Agenzia perlo Sviluppo Tecnologico dellEmilia Romagna, via San Felice 26, I - 40122BOLOGNA. Tel: 39-51-23.62.42. Fax: 39-51-22.78.03

BCEOM - Societe Fran~caise dlngenierie, Place des Freres Montgolfier, F - 78286

GUYANCOURT Cedex. Tel: 33-1-30.12.49.90. Fax: 33-1-30.12.10.95

BRECSU - Building Research Establishment, Garston, Watford, Hertfordshire, UK- WD2 7JR.Tel:44-923-66.47.54/56. Fax: 44-923-66.40.97

CCE - Estrada de Alfragide, Praceta 1 -Alfragide, P - 2700 AMADORA.Tel: 351-1-471.14.54/81.10. Fax: 351 -1-471. 13. 1 6

CEEETA - PARTEX Cps, Cal,cada da Estrela, 82 -1 DT, P- 1200 LISBOATel: 351-1-395.56.08. Fax: 351-1-395 24 90

CESEN - Viale Brigata Bisagno, 2, I -16129 GENOVATel: 39-10-550.46.70. Fax: 39-10-550.46. 18

CORA c/o SEA - Saarlandische Energie-Agentur, Altenkesselerstrasse 17, D - 66115SAARBRUCKENTel: 49-681-976.21.70. Fax: 49-681-976.21.75

COWlconsult - Engineers and Planners A/S, Parallelvej 15, DK - 2800 LYNGBYTel: 45-45-97.22.11. Fax: 45-45-97.22.12

CRES - Centres for Renewable Energy Sources, 19 km Athinon - Marathona Avenue, GR -19009 PIKERMI.Tel: 30-1-603.99.00. Fax: 30-1-603.99.04/11


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EAB - Energie-Anlagen Berlin GmbH, Flottwellstr. 4-5, D- 10722 BERLINTel: 49-30-25.49.6-0. Fax: 49-30-25.49.62.30

ECOTEC - Research and Consulting Ltd, Priestley House, 28-34 Albert Street, UK-BIRMINGHAM B47UD.Tel: 44-21-616.10.10. Fax: 44-21-616.10.99

ECD - Energy Centre Denmark, Suhmsgade 3, DK- 1125 K0BENHAVN KTel: 45-33-11.83.00. Fax: 45-33-11.83.33

ENEA - ERG-PROM CRE-Casaccia, ViaAnguillarese, 301, I - 00060 S. Maria di Galeria ROMATel: 39-6-30.48.4118-3686. Fax: 39-6-30.48.6449

ETM Consortium - European Technology Marketing, 51, rue Colonel Picquart, B-1030BRUXELLESTel: 32-2-539.00.15. Fax 32-2-534.86.30

ETSU - Harwell, Oxfordshire, UK - OX11 0RATel: 44-235-43.33.27. Fax: 44-235-43.20.50

EUROPLAN - CHORUS, 2203 Chemin de Saint Claude, Nova Antipolis, F - 06600 ANTIBESTel: 33-93.74.31.00. Fax: 33-93.74.31.31

EVE - Ente Vasco de la Energia, Edificio Albia 1, San Vicente 8- Planta 14, E - 48001 BILBAOTel: 34-4-423.50.50. Fax: 34-4-424.97.33

FAST - Federazione delle Associazioni Scientifiche e Tecniche, Piazzale Rodolfo Morandi 2, 1-20121 MILANOTel: 39-2-76.01.56.72. Fax: 39-2-78.24.85

Fiz-Karlsruhe / KFA Julich, c/o Abt. BEO, Postfach 1913, D - 52405 JULICHTel: 49-2461/61-3729. Fax: 49-2461/61-5837

FORBAIRT - The Irish Science and Technology Agency, Glasnevin, IR - DUBLIN 9Tel: 353-1-837.01.01. Fax: 353-1-837.28.48

Friedemann und Johnson - Consultants, Pestalozzistr. 88, D-10625 BERLINTel: 49-30-312.2684. Fax: 49-30-31 3.2671

GEP - rue Louis Blanc 1, La Defense 1, F - 92038 PARIS LA DEFENSETel: 33-1-47.17.67.37. Fax: 33-1-47.17.67.47

GOPA - Consultants, Hindenburgring 18, D - 61348 BAD HOMBURGTel: 49-6172-930-0. Fax: 49-61 74-3-5046

ICAEN - Institut Catala dEnergia, Avda Diagonal, 453 Bis, Atic, E - 08036 BARCELONATel: 34-3-439.28.00. Fax: 34-3-419.72.53

ICEU Leipzig GmbH, Auenstr. 25, D - 04105 LEIPZIGTel: 49-341-29.46.02/43.50. Fax: 49-341-29.09.04

ICIE - Istituto Cooperativo per llnnovazione, Via Nomentana 133, I - 00161 ROMATel: 39-6-884.58.48. Fax: 39-6-855.02.50

IDAE - Instituto para la Diversificacion y Ahorro de la Energ~a, P de la Castellana 95 - P 21E- 28046 MADRID


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