Flaring and Venting

8/12/2019 Flaring and Venting

http://slidepdf.com/reader/full/flaring-and-venting 1/18



P ublications

Global experience

he International Association of Oil & Gas Producers (formerly the E&P Forum) hasaccess to a wealth of technical knowledge and experience with its members operatingaround the world in many different terrains. We collate and distil this valuable knowl-edge for the industry to use as guidelines for good practice by individual members.

Consistent high quality database and guidelines

Our overall aim is to ensure a consistent approach to training, management and bestpractice throughout the world.

he oil and gas exploration and production industry recognises the need to develop con-sistent databases and records in certain elds. The OGP’s members are encouraged touse the guidelines as a starting point for their operations or to supplement their ownpolicies and regulations which may apply locally.

Internationally recognised source of industry information

Many of our guidelines have been recognised and used by international authorities andsafety and environmental bodies. Requests come from governments and non-governmentorganisations around the world as well as from non-member companies.

Disclaimer

Whilst every effort has been made to ensure the accuracy of the information contained in this publication, neither the OGP nor any of its members will assume liability for any use madethereof.

Copyright OGP

Material may not be copied, reproduced , republished, downloaded, posted, broadcast or

transmitted in any way except for your own personal non-commercial home use. Any otheruse requires the prior written permission of the OGP.

hese Terms and Conditions shall be governed by and construed in accordance with the lawsof England and Wales. Disputes arising here from shall be exclusively subject to the jurisdic-tion of the courts of England and Wales.



Flaring & venting in the oil & gasexploration & production industry

Report No: 2.79 288

January 2000



Authors

These guidelines have been prepared for the OGP by the Flaring and Venting Task Force of the OGP’s Environ-

mental Quality Committee. The task force members were:

John Kearns BHP Petroleum

Kit Armstrong Chevron

Les Shirvill hell

Emmanuel Garland Elf

Carlos Simon exaco

Jennifer Monopolis Exxon

he OGP

The International Association of Oil & Gas Producers (OGP) is the international association of oil companiesand petroleum industry organisations formed in 1974. It was established to represent its members interests at thenternational Maritime Organisation and other specialist agencies of the United Nations, and to governmental

and other international bodies concerned with regulating the exploration and production of oil and gas. Whilemaintaining this activity, the Forum also concerns itself with the development and dissemination of best practice onall aspects of exploration and production operations, with particular emphasis on safety of personnel and protectionof the environment. As of late 1999, the OGP has 60 members made up of 49 oil companies, 8 national oil industry

associations, and 3 technical institutes operating in 60 different countries.


http://slidepdf.com/reader/full/flaring-and-venting 6/18ii

International Association of Oil & Gas Producers

© 2000 OGP

The option to release gas to the atmosphere by aringand venting is an essential practice in oil and gas pro-duction, primarily for safety reasons. Flaring is the

controlled burning of natural gas produced in associa-tion with oil in the course of routine oil and gas pro-duction operations. Venting is the controlled release ofunburned gases directly into the atmosphere. The avail-ability of a are or a vent ensures that associated naturalgas can be safely disposed of in emergency and shut-down situations. Where gas cannot be stored or usedcommercially, the risk of re and explosion must bereduced by either aring or venting.

t is in an oil company’s interest to minimise the amountof gas ared in order to realise as much value as possi-ble from the hydrocarbons being produced. A variety ofmechanisms may potentially be used to minimise ar-ing. However, it may not be technically or economicallyfeasible to sell some or all of the gas, for reasons thatare often a combination of geography, availability ofcustomers, and government energy policies. Similarly, itmay not be technically or economically feasible to rein-ect the gas into underground reservoirs. Therefore, gas

may have to be ared as a waste product. In some cases,venting may be preferable to aring, depending on con-siderations such as local noise impacts, toxicity of gases

being produced, and hydrocarbon content of the gas.

For environmental and resource conservation reasons,aring and venting should always be minimised asmuch as practicable, consistent with safety considera-

tions. Flaring and venting can have local environmen-tal impacts, as well as producing emissions which havethe potential to contribute to global warming. Avail-able data indicate that, on a worldwide basis, gas aringcontributes only 1% of anthropogenic carbon dioxideemissions, and aring and venting contribute only 4%of anthropogenic methane emissions. Case studies inthis booklet illustrate some of the ways in which theindustry has sought to reduce aring and/or minimiseits impacts through commercialisation of gas reserves,improvements in operation, maintenance and design of

are systems, and new ways of storing associated gas.

Despite these developments, the essential point is thatno single approach to dealing with associated gas will beappropriate for all projects or locations. Industry needsto be able to choose from among a variety of creativeand common sense approaches to address aring andventing concerns in specic operations. To achieve this,governments need to provide an energy policy frame-

work which will encourage and allow companies toselect from among very different approaches in order toachieve the best practicable outcome in particular cir-

cumstances.

Executive summary



Flaring & venting in the oil & gas exploration & production industry

© 2000 OGP

1 Introduction

he option to release gas to the atmosphere by aring orventing is a necessary practice in the production of oiland gas. This booklet is intended to provide basic non-

technical information about the reasons gas is ared1 orvented . It explains what aring and venting are, whythey occur, their links with the safety of workforces andlocal populations, and relevant environmental impacts.

t also describes some of the varied steps being taken within the industry to improve environmental perform-ance by reducing aring and venting emissions. Case

studies are presented to illustrate some current andexperimental practices in the oil and gas productionbusiness.

Flaring is the controlled burning of natural gas in thecourse of routine oil and gas production operations.

his burning occurs at the end of a are stack or boom.Flare systems and their operation have been discussedby a number of authors of technical papers. Shore’spaper ‘Making the Flare Safe’ (Ref. 1) provides a gen-eral introduction to the systems used in the oil and gasindustry.

A complete are system consists of the are stack orboom and pipes which collect the gases to be ared. Theare tip at the end of the stack or boom is designed toassist entrainment of air into the are to improve burnefciency. Seals installed in the stack prevent ashbackof the ame, and a vessel at the base of the stack removesand conserves any liquids from the gas passing to theare. Depending on the design, one or more ares maybe required at a production location.

A are is normally visible and generates both noise andheat. During aring, the burned gas generates mainly

water vapour and carbon dioxide. Efcient combustionin the ame depends on achieving good mixing between

the fuel gas and air, and on the absence of liquids. Low-pressure pipe ares are not intended to handle liquids

and do not perform efciently when hydrocarbon liq-uids are released into the are system.

The percentage combustion efciency of a well designedand operated are is in the high ninety percent range.Recent work by the U.S. Environmental Protection

Agency has shown that combustion efciencies are oftengreater than 98% (Ref. 2)

Gas being ared may come from a variety of sources.t may be excess to that which can be supplied com-

mercially to customers. It may be unburned process gas

from the processing facilities. It may be vapours col-lected from the tops of tanks as they are being lled.ometimes, the gas may be from process upsets, equip-

ment changeover or maintenance. Occasionally, a pro-duction shutdown may require the temporary aring ofall the gas stored on or arriving at a facility, to releasehigh pressure and avoid a catastrophic situation occur-ring.

t is in the oil company’s interest to realise as muchvalue as possible from the hydrocarbon accumulationsthe company is producing. Therefore, it is also in the

company’s interest to minimise the amount of gas beingared. In this respect, the commercial aims of the com-pany are consistent with good environmental practice.

2 What is aring?

This booklet addresses aring during oil and gas production operations. Although ares are sometimes used duringdrilling to test the productivity of a potential well, the technologies and issues related to burning during these so-called‘well tests’ are different from aring during production operations and are not discussed here.

2 There are situations where small amounts of gases escape to the atmosphere from pump seals, valves and tank spaces.These are typically called “ fugitive” emissions. Fugitive emissions are the subject of a number of other reports (see Ref.

3). This booklet deals only with the controlled release or venting of gases.Calculations of combustion efciency do not normally include the negligible effect of carbon emitted as soot or smoke.Further, unless the are is very smoky, the solid carbon emitted is likely to be insignicant. In fact, measurements madeon propane ares have shown that soot accounted for a decrease of less than 0.5% in the combustion efciency.




© 2000 OGP

The aim of minimising aring can be achieved througha variety of mechanisms which may range from mar-keting initiatives to maintenance strategies to new tech-

nologies. The following discussion, and the case studies which illustrate it, serve to explain how different solu-tions are appropriate in different circumstances.

Oil accumulations always occur with some amount ofassociated gas. Ideally, the associated gas will be sold toa customer as a fuel or petrochemical feedstock. How-ever, unlike oil, gas is not an easily transportable fuel.

A customer must be reasonably physically close in orderfor the additional expense of gas processing and trans-portation to be economically justiable. The customermust also be willing to enter into the necessary com-mercial arrangements. The political will also needs toexist within government to provide an appropriate scalregime which will allow the project to go ahead.

owever, these conditions can be difcult to achieve inpractice. The government may have other national pri-orities that conict with developing a supportive nan-cial regime. Potential customers may have other projectsthey wish to pursue. Case Study No. 1 shows howmarket factors can inuence aring within a particularcountry or region.

Technology may also offer new ways to commercialiseassociated gas reserves. Although gas itself is relativelydifcult to transport, it can be liqueed and then trans-

ported more easily. In recent years, the exploration andproduction industry has signicantly improved gas lique-faction technologies - technologies which until recentlycould only be applied to the largest gas reserves.

n the situation where the associated gas cannot be com-mercialised, only three options remain: 1) vent it, 2)are it, or 3) reinject and store it in the undergroundformations from which the oil is being recovered. Rein-ection is a practicable option for some oilelds, but not

in all cases. In some situations, the geological nature ofthe underground formations is such that the injectedgas would migrate back to the oil production wells tooeasily, leading to inefcient and energy intensive gasrecycling. Even for formations where reinjection is geo-logically practicable, the oileld itself may be too smallin economic terms to support the additional reinjectioninfrastructure.

Although the current viability of underground gas stor-age is limited by geology and economics, some com-panies are investigating ways of making undergroundstorage more attractive. One example of this is the Sleip-

ner carbon dioxide storage project now in operation off-shore Norway (see Case Study No. 2).

What is venting?

Venting is the controlled release of gases into the atmos-

phere in the course of oil and gas production operations.These gases might be natural gas or other hydrocarbonvapours, water vapour, and other gases, such as carbondioxide, separated in the processing of oil or naturalgas.

n venting, the natural gases associated with the oil pro-duction are released directly to the atmosphere and notburned. Safe venting is assured when the gas is releasedat high pressure and is lighter than air. Because of thestrong mixing potential of high-pressure jets, the hydro-carbon gases discharged mix well with the air down to

safe concentrations at which there is no risk of explo-

sion. Venting is normally not a visible process. However,

it can generate some noise, depending on the pressureand ow rate of the vented gases.

n some cases, venting is the best option for disposal ofthe associated gas. For example, in some cases, a highconcentration of inert gas is present in the associatedgas. Without a sufciently high hydrocarbon content,the gas will not burn and aring is not a viable option.

ometimes the source of inert gas may come from theprocess systems. The purging of process systems withinert gas may, in itself, justify venting as the safestmeans of disposal.




© 2000 OGP

4 Safety aspects

he availability of a are or a vent is absolutely neces-sary in oil and gas production operations. It ensuresthat safe disposal of the hydrocarbon gas inventory in

the process installation is possible in emergency andshutdown situations. Where gas cannot be stored orused commercially, it is essential that the risk of re andexplosion be reduced by either aring or venting.

Even where associated gas is being sold or reinjected,small amounts of gas will still need to be ared or ventedfor safety reasons. Oil and gas processing and storageequipment is often operated at high pressures and tem-peratures. When abnormal conditions occur, the controland safety systems must release gas to the emergencyare or vent to prevent hazards to the employees orpublic. Good maintenance and operating strategies arethe main mechanisms used to keep this already smallvolume as low as practicable.

Emergency ares are normally tted with pilot systemsmaintaining a small ame as the ignition source in case

the full size are is activated. Recently, new are equip-ment designed to operate without a pilot ame, andhence without emission when not active, was installed

on a number of Statoil’s production facilities in Norway.This equipment, built around high reliability valves andignition systems, is described in Case Study No. 3.

Another safety issue in the application of aring andventing is the toxicity of the gases being disposed. Insome situations, the toxicity of the gas relative to thetoxicity of its combustion products may need to be con-sidered when choosing between aring and venting as ameans of disposal. An example would be where gas con-taining hydrogen sulphide is being produced. Hydro-gen sulphide is a gas that can be fatal if inhaled even atlow concentrations. However, its combustion product,sulphur dioxide, is relatively less toxic.

eople outside the oil and gas industry sometimesexpress concerns about the environmental impacts ofaring and venting. One such concern relates to thepotential for global climate change. Both carbon diox-ide and methane (the major component of natural gas)are known as greenhouse gases associated with concernsabout global warming.

Flaring produces predominantly carbon dioxide emis-

sions, while venting produces predominantly methaneemissions. The two gases have different effects, how-ever. The global warming potential of a kilogram ofmethane is estimated to be twenty-one times that of akilogram of carbon dioxide when the effects are consid-ered over one hundred years. When considered in thiscontext, aring will generally be preferred over ventingthe same amount of gas in the design of new facilities

where sufcient amounts of gas will be produced to runa are.

While there are still many uncertainties in our under-

standing of the complex issue of climate change, itmakes sense to avoid the unnecessary release of carbondioxide or methane into the atmosphere, where practi-cable. This points to a need to reduce emissions in a rea-

sonably practicable way. The case studies in this bookletillustrate some of the ways the oil and gas industry isachieving those reductions. However, it is important torecognise that other environmental impacts also needto be managed.

ometimes those needs can conict with managinggreenhouse gas emissions. This conict may take a vari-ety of forms, but usually relates to the need to manage

potential contributions to local environmental impacts,such as air quality, alongside global issues, such as cli-mate change. Although the global warming potentialof methane when compared to carbon dioxide usuallysuggests that aring is a more environmentally attrac-tive option than venting, neighbours of onshore oil andgas developments sometimes prefer venting because it isless visible and produces less noise.

n all cases, the company has the responsibility to makeparties involved aware of all aspects of the issue to ensurereasoned decisions are taken and supported. Case Study

o. 4 illustrates the way in which local factors need tobe taken into account when designing are systems.

5 Environmental issues




© 2000 OGP

5.1 Measuring quantities of gas ared or vented

One of the challenges involved in addressing environ-mental aspects of aring and venting is identifyinghow much gas is being released. All oilelds contain

associated gas. In much the same way that bubblesappear when the cap is removed from a bottle of car-bonated drink, so the associated gas is released whenoil is brought up from the deep rock strata in whichit is found. The proportion of associated gas to oilthe so-called GOR or Gas Oil Ratio) can vary signi-

cantly between oilelds. Moreover, in some oilelds,the GOR increases as more and more oil is produced,

while in others it can reduce with time. Consequently,the amount of gas which must be dealt with can varydramatically from year to year between oilelds and

even within a specic oileld.

As previously discussed, some or all of this associatedgas may have to be ared or vented. Oil and gas pro-duction systems can be complex. The gas eventuallyreaching the are or vent can come by means of a gath-ering system from a variety of sources - pressure reliefsystems, maintenance related depressurising systems,etc. Many of these systems supply gas to the gatheringsystem, often only sporadically.

A major difculty in managing aring and venting

is identifying exactly how much gas is coming fromthe various sources that are contributing to the overallvolume ared and vented. There is debate within theindustry regarding the extent to which it is possible

to measure gas ow rates accurately under such variedconditions with the measuring devices presently avail-able on the market. Although some oil companies and

equipment manufacturers would disagree, low-pressuregas rate measurement can be a signicant problem.Others believe that the best way to obtain consistentdata is to base it on estimates and calculations.

n order to provide some degree of consistency of data,the OGP has published its own measurement andestimation protocol (Ref. 4). This document providesguidance on the different approaches to measuring orestimating are and vent volumes.

Measurements and estimates of amounts of gas ared

and vented have been produced by a number of organi-sations. On a global scale, the Carbon Dioxide Infor-mation Analysis Centre in the U.S. is considered oneof the most denitive data sources (see Refs. 5 & 6).Regional data have been produced by intergovernmen-tal agencies, as well as by oil industry associations suchas the OGP (see e.g., Ref. 7). Some individual oil com-panies and national oil industry associations also com-pile aring and venting data (see e.g., Ref. 8).

Because of linkages with the climate change debate,aring and venting emission data are often presented

in terms of the two main greenhouse gases which areproduced: carbon dioxide and methane.




© 2000 OGP

Atmospheric carbon dioxide (CO2) is produced bothfrom natural sources and human (anthropogenic) activ-ities. The most important source of carbon dioxide from

human activities is the release during the consumptionof fossil fuels. Figure 1 shows that96% of human-related emissions ofcarbon dioxide are associated with theconsumption of either solid, liquid,or gaseous hydrocarbon fuels.

he Carbon Dioxide Information Analysis Centre also identies twoadditional contributors that make upthe remaining 4%. These are cementmanufacture and gas aring oper-ations. On a worldwide basis, gasaring contributes only 1% to anthro-pogenic carbon dioxide emissions.

he relative contributions from thesesources in 1994 are presented inFigure 1 (source, Ref. 5).

As one perspective on these data, it can be noted thattropical deforestation with its resulting emissions to theatmosphere is estimated to be thirty times greater than

the emissions from gas aring

.

5.2 Carbon dioxide emissions from aring

5.3 Methane emissions from aring and venting

Atmospheric methane is producedfrom a range of both natural sources,such as wetlands, and human activi-ties. Of the total sources of methaneentering the atmosphere for the period1980-1990, 30% came from naturalsources and 70% from anthropogenicsources (Ref. 6).

he anthropogenic sources can befurther broken down into those thatarise from the use of fossil fuelsand those from so-called biosphericsources. Biospheric sources includesuch things as release of methane fromrice farming, livestock rearing, burn-ing of biomass fuels such as wood,and landlls. These biospheric sourcescontribute over 73% of anthropo-genic methane emissions (Ref. 6).

Figure 1: Contributions to anthropogenic carbon dioxide emissions, 1994

Source: United States National Aeronautic and Space Administration s Goddard Institute for Space Studies.[http://www.giss.nasa.gov/research/intro/matthews.01/]

Gas flaringCement manufacture

Gaseous fuel use

Liquid fuel use

Solid fuel use

Flaring & ventingGas supply

Landfill

Biomass burning

Coal mining Rice production

Livestock farming

Figure 2: Contributions to global methane emissions, 1994




© 2000 OGP

6 Resource conservation

Another concern sometimes expressed is that the natu-ral gas burned in a are or vented to the atmosphere isa natural resource which could be effectively used as asource of energy or useful chemicals. Progressively, the

world is seeking ways to avoid wasting natural resources,particularly those considered not renewable. As it is inthe interest of the industry to realise as much value aspossible from its hydrocarbon production, aring andventing should always be minimised, consistent withsafety considerations.

any oilelds currently still in production were startedat a time when there was less concern about conservation

of resources

than there is today and the issue of global warming hadnot been identied. However, for all of the reasons pre-viously described, oil companies have continued to seek

ways to reduce waste of gas and maximise the nancialreturn from the resources they are developing.

As an example, Barns (Ref. 9) describes how, in 1950,the Indonesian oil industry ared 95% of the totalamount of associated gas that it produced. By 1985, theamount of gas being ared had declined to 28%. Casetudy No. 1 shows in some detail the kinds of factors

that affect the speed and extent to which resource con-servation improvements can be achieved in mature oilproducing regions.

The overall impact of these factors has been a gradualreduction in volumes of gas ared and vented

over the last two decades. It is generallyaccepted that aring and venting vol-umes peaked in the mid 1970’s (Refs.5 & 6). As an example, Figure 3 showshow the amount of carbon dioxidereleased from aring has reducedsince that time. Increase in later yearsis attributed to the general expansionof the E&P industry.

Figure 3: Worldwide carbon dioxide emissions

from aring (MM metric tonnes)

0

50

100

150

200

250

300

350

400

19951990198519801975

A n n u a

l C O 2 e m i s s i o n s

The remaining anthropogenic sources are associated with the use of fossil fuels and include such thingsas aring and venting of natural gas, leakage from

gas supply systems, and methane released during coalmining operations. Venting operations contribute sig-nicantly more methane than aring operations.

The overall contribution of the various sources of meth-ane in the atmosphere for 1994 are shown schematicallyin Figure 2 (source, Ref. 6). On a worldwide basis, ar-

ing and venting operations contribute 4% to anthropo-genic methane emissions.




© 2000 OGP

7 Conclusions

Flaring and venting are unavoidable processes in theproduction of oil and gas. Primarily for reasons of safety,some gas may need to be ared or vented at the pro-

duction site. In other cases, for reasons that are often acombination of geography and availability of customersfor gas, as well as local political factors, some or all ofthe associated gas produced with the oil is ared.

ndustry continues to seek opportunities to reduce theamount of gas being ared and vented. As an example,since the mid-1970’s, the amount of carbon dioxideemitted due to aring has nearly halved, and furtherreductions continue to be sought. New technologiesare being developed to assist in the commercialisationof associated gas reserves. Operation, maintenance anddesign of are systems are improving. New ways of stor-ing associated gas are being investigated.

While recognising the need for these improvements, itis important to note that aring and venting are rela-tively small contributors to anthropogenic greenhousegas-related emissions. Overall, aring and venting con-

tribute only 1% to anthropogenic carbon dioxide emis-sions, and 4% to anthropogenic methane emissions.

The most important single conclusion to be drawn fromthe information presented in this booklet is the needfor industry to be able to choose from among a varietyof creative and common sense approaches to addressaring and venting concerns in specic operations.

Whether with respect to selecting among technologies,choosing between aring or venting, or maintaining abalance between climate change and other environmen-tal concerns, regulatory frameworks need to allow forbest practicable choices to be made, rather than man-dating a specic solution. No single approach will nec-essarily be appropriate for all projects or locations.

The intrinsic value of the gas being ared or ventedmotivates the industry to manage the issue well. Gov-ernment regulatory policy needs to be sufciently ex-ible to facilitate the choice of the management approachmost appropriate for the project and the situation.




© 2000 OGP

Appendix A – case studies

Case study 1: The role of market forces – aring and the Nigerian oil industry

Case study 2: Research and development into carbon dioxide storage – the Sleipner

O Project

ost of Nigeria’s oil facilities were built in the 1960’s

and 1970’s. In those days gas was not a popular energysource. Gas was more difcult to produce and transportthan crude oil; there were few market outlets (domesticand international) for gas and there was little environ-mental awareness of the consequences of gas aring.

n the 1960’s and 1970’s, the main interest was in thedevelopment of the country’s oil reserves. At this initialstage, the existing oil elds did not produce signicantamounts of associated gas. This fact, coupled with thelack of a domestic gas market and commercial energypricing policy, meant that installation of an expensive

network of compression facilities and pipelines neededto link these scattered elds and market the gas couldnot be economically justied. Consequently, when therst small volumes of gas did start to ow to Nigerianindustry, they were from non-associated gas reservoirs,

which were a cheaper and more reliable source becausethey were produced at high pressure and did not dependon oil production.

One of the earliest solutions to the dilemma of gas ar-ing in Nigeria was the re-injection of produced asso-ciated gas into underground reservoirs. SPDC (Shell

etroleum Development Company) was the rst com-pany in Nigeria to re-inject gas, at Oguta in 1978. How-ever, associated gas re-injection proved not to be a viableproposition in all cases. Most Nigerian oil reservoirs aretechnically unsuitable for large-scale re-injection.

From the standpoint of export markets, Nigeria’s physi-cal isolation from the nearest major international gas

markets in Europe ruled out a pipeline. This left the

technologically more complex and expensive option ofliquefying and shipping the gas. Nigeria’s rst liqueednatural gas (LNG) plant is currently being installed.There are already plans for future expansion.

owever LNG is only part of the answer. Any success-ful programme to end gas aring in Nigeria dependson creating local markets. The key to achieving thislies with industry, which alone can harness the sort ofvolumes required. Although many industries are con-nected to gas pipelines, the major users of large volumesof gas so far are the National Electric Power Authority

(NEPA) which uses gas to generate electricity and theNational Fertiliser Company (NAFCON). Several newprojects that will use associated gas are being planned,but there remains a need for more gas-based industrialdevelopment.

For that to happen, consumers need incentives to usegas rather than other energy sources, and suppliers needincentives to build expensive gas gathering, compres-sion and treatment systems. Harnessing the gas whichis currently being ared must, at the end of the day, bean economic proposition. The price has to be right to

ustify the use of gas by the consumer. The price mustalso justify the supplier’s investment in the necessaryplant and equipment. To achieve this, allowances haveto be made in scal and gas pricing policies and in oper-ating agreements. The oil industry in Nigeria is working

with the government to accomplish these objectives.

A unique event took place in October 1996 when Sta-toil, Norway’s State oil and gas company, began storingcarbon dioxide under the North Sea. Statoil’s Sleipnergas eld is situated 250 km west of the Norwegian coast.

As with many gas elds around the world, extractingthe gas also yields unwanted products. In this case thegas contains 9% carbon dioxide. For the gas to be mar-ketable, this concentration must be reduced to 2.5%.

istorically, gas contaminants have been typicallyvented to the atmosphere prior to selling the natural

gas. However, Norwegian government concerns aboutcarbon dioxide emissions from human activity and theirpotential contribution to global warming prompted adecision to impose a carbon tax on oil and gas produc-

tion. Statoil and its partners started to look at radicallynew technology in order to commercialise the Sleipnergas reserve. They eventually decided that it might betechnically and economically feasible (considering thecarbon tax) to separate the carbon dioxide from thehydrocarbon gas and re-inject it into deep undergroundformations.

A new offshore platform, Sleipner ‘T’, containing allthe necessary equipment was sited alongside the exist-ing production platform, Sleipner ‘A’, in 1996. On

leipner ‘T’, the carbon dioxide contained within thenatural gas is separated by a complex chemical process.The extracted carbon dioxide are then compressed andinjected into a water lled sandstone reservoir 1000 m




© 2000 OGP

Case study 3: Technical innovations in are design – the Gullfaks Project

Case study 4: Local factors inuence are design in Venezuela

echnological innovations pioneered in Norway could,in some situations, provide a means of eliminating the

small amount of ‘pilot’ gas which is currently neededon conventional are systems. The technique, whichhas been pioneered on the North Sea Gullfaks eld,involves routing gas which was previously ared back toan existing gas export system through pipework with avalve which can quickly divert the ow to the are stackif the pressure starts to increase. As an added safetymeasure, the piping contains an extra loop with a rup-ture disk to provide a second fail-safe escape route if thevalve does not open.

An automatic ignition system, comprising a gun tted

at the top of the are stack to shower specially-formu-lated pellets at a steel plate, provides sparks to light theare when it is needed. Under normal conditions, thepiping in the are stack is protected against a build up

of explosive mixtures by being lled with an inert gasfrom a nitrogen generation plant.

A critical factor in developing the system was beingable to convince the Norwegian safety regulator thatthe system would meet their requirements. The break-through was achieved when it was decided to add theloop with the rupture disk. This ensured that there

would be two possible routes by which gas could reachthe are stack in an emergency.

After a number of start-up problems, the Gullfaks ‘C’platform are has now been extinguished while aringon Gullfaks ‘A’ is down by 60% and will end in the nearfuture. If the experience proves positive, steps to reducearing on some other platforms are likely. However, thetechnique is only suitable for use with inclining arestacks rather than the vertical stacks tted on many ofthe existing oil developments around the world.

DVSA, the Venezuelan national oil company, uses ahigh-pressure gas injection system to improve oil recov-ery in its operations in the eastern part of the country.

he high-pressure gas injection system employs the

largest high-pressure gas compressors for well injectionin the world. One of the necessary components of thissystem is equipment which will safely are the com-pressed gas in the event of either planned or unplannedshutdowns.

n the case of this gas injection project, several localenvironmental constraints presented a unique set ofproblems for system designers:

• Due to the very high prole nature of the projectand the plant s location near a major industrialresidential city, a 100% smokeless are operation

was required.

• A relatively small plot was available on which to sitethe are system. The compression plant is situated

near a major highway and is surrounded by existingproduction and oil processing plant facilities.

• Due to the proximity of a nearby international air-port, and other local safety considerations, there

was a need to restrict such factors as are stackheight and heat radiation intensity.

• The system needed to be capable of handling a widerange of gas owrates.

• An unreliable local power supply produced therequirement that all are system controls be fail-safe with a 24-hour automatic battery back-up.

One of the key design considerations was the need forsmokeless operation within the limitations imposed by

stack height and radiation. A are design had to beselected which would not only provide optimal mixingof gas and air to produce virtually smokeless operationover the entire owrate range, but would also produce a

below the seabed. Using this system, over 1 milliontonnes per year of carbon dioxide is being pumpedbelow the ocean oor instead of the atmosphere.

his technology is still in its infancy, and much willbe learned from its use on Sleipner. The owners of theeld have agreed that an international programme isto be formed in order to monitor and research the per-formance of this facility so that the underground stor-

age of carbon dioxide can be more fully understood.The International Energy Agency’s Greenhouse GasResearch and Development Programme is working with

tatoil to establish and manage this programme. Themajor task for this group will be to monitor the sta-bility of the underground reservoir and to observe thedevelopment of the expanding carbon dioxide bubblein order to ensure that the gas remains within the reser-voir.




© 2000 OGP

small but very intense ame with low radiation effects.To handle the full ow range, a three-stack array wasinstalled that included two high-pressure and one low-

pressure are tip.

Before installation, the ares were tested individuallyand collectively and performed smokelessly within the

radiation limits over the full specied range of opera-tion. Pre-installation checks also included a check of thebattery back-up system and the instant re-light system

that immediately re-ignites the are (or shuts in the gasow) if the are goes out for any reason.

Appendix B – references

1. “Making the Flare Safe”, David Shore, Journal of Loss Prevention in Process Industries, Vol 9, No. 6,pp363-381, 1996.

2. Flare efciency Study, EPA-600/2-83-052, U.S. Environmental Protection Agency, Cincinnati, OH, July1983.

. IEA Report No. PH2/7 (Jan 1997), Methane Emissions from the Oil and Gas Industry.

. OGP Technical Report No. 2.59/197 (Sept 1994), Methods for Estimating Atmospheric Emissions from E&POperations.

5. Marland G., Andres R. J., Boden T. A., Johnston C., & Brenkert A., Global, Regional, and National CO2

Emissions Estimates from Fossil Fuel Burning, Cement Production, and Gas Flaring: 1751-1995 (revised January1998), Carbon Dioxide Information Analysis Centre, Oak Ridge National Laboratory, U.S. Department ofEnergy, Oak Ridge, Tenn., U.S.A.

. Stern, D. I., and R. K. Kaufmann, Estimates of Global Anthropogenic Methane Emissions: 1860-1994. TrendsOnline: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Centre, Oak RidgeNational Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A., 1988

. OGP Report No. 2 66/216 (Dec 1994), Atmospheric Emissions from the Offshore Oil and Gas Industry in Western Europe.

. Greenhouse Gas Emissions - Emissions and Action Plans. The Australian Petroleum Exploration and ProductionIndustry Association. August 1997.

9. Barns D. W., and Edmonds J. A. 1990. An Evaluation of the Relationship between the Production and Useof Energy and Atmospheric Methane Emissions. US Department of Energy, Washington D.C., DOE/NBB-0088P.



What is OGP?

The International Association of Oil & Gas Producers encompasses the world’s leadingprivate and state-owned oil & gas companies, their nationaland regional associations,and major upstream contractors and suppliers

Vision

• o work on behalf of all the world’s upstream companies to promote responsible andprotable operations.

Mission

• To represent the interests of the upstream industry to international regulatory andlegislative bodies.

• To achieve continuous improvement in safety, health and environmental performanceand in the engineering and operation of upstream ventures.

• To promote awareness of Corporate Social Responsibility issues within the industryand among stakeholders.

Objectives

• To improve understanding of the upstream oil and gas industry, its achievements andchallenges, and its views on pertinent issues.

• To encourage international regulators and other parties to take account of the industry’sviews in developing proposals that are effective and workable.

• To become a more visible, accessible and effective source of information about theglobal industry, both externally and within member organisations.

• To develop and disseminate best practices in safety, health and environmentalperformance and the engineering and operation of upstream ventures.

• To improve the collection, analysis and dissemination of safety, health andenvironmental performance data.

• To provide a forum for sharing experience and debating emerging issues.

• To enhance the industry’s ability to inuence by increasing the size and diversity ofthe membership.

• To liaise with other industry associations to ensure consistent and effective approachesto common issues.



�

�

�

�

Flaring and Venting

Documents

Transcript of Flaring and Venting