HOW TO IMPROVE ENERGY EFFICIENCY ON OIL & GAS FACILITIES
Anne Rocher 1, Frédéric Garnaud 2
1. Total Exploration and Production – Energy Efficiency Coordinator
2. Total Exploration and Production - RD program manager surface technologies
Keywords: 1. energy assessments; 2. performance improvement; 3. consumptions reduction.
Climate change and emission management presents big challenges for all industrial sectors.
Demands for action to stabilize greenhouse gas emissions are stronger and when looking at different options
for their mitigation, energy efficiency appears to have a major role to play.
The IEA World Energy Outlook 2008 (WEO 2008) estimates that the energy efficiency
recommendations could deliver over 8.2 Gton/year of CO2 emission reduction by 2030.
In the near future energy efficiency is potentially the most important and cost-effective means for
mitigating greenhouse gas emissions from industry.
TOTAL has been involved for several years in the minimization of greenhouse gas emissions. The
primary actions focussed on the flaring/venting reduction. A zero continuous flaring policy has been applied
to all new developments since 2000. Even if access to gas market is not available, alternative solutions, such
as gas re-injection either in the same reservoir or other disposal reservoir, must be implemented. For all
other operated assets, TOTAL’s commitment is to halve continuous flaring between 2005 and 2012, as
announced at the Global Gas Flaring Forum in Paris (2005),
Beyond flaring reduction, TOTAL is now working on improving energy efficiency of both existing
operated assets and new developments. Within Oil & Gas Industry, approximately 2/3 of today’s greenhouse
gases emissions are due to flaring/venting, but in the next 10 to 15 years this tendency will be reversed and
about 2/3 of emissions will be related to combustion of fuels (fuel gas, oil/condensates or diesel) required to
generate necessary energy for Oil & Gas Plants.
2 Objectives of the paper
The objectives of this paper are to describe the methodologies and tools developed internally by
TOTAL to minimize energy consumptions firstly on existing assets, and through studies of new
developments. A summary of main achievements is discussed hereafter. Finally, an example of energy
efficiency improvement will be given, whereby fuel gas has been replaced by nitrogen as the flare purge gas.
3 TOTAL methodology for energy efficiency improvements
a. Energy assessments on existing assets
Review of energy consumption forecast for producing assets tends to show a constant increase. This
increase could be explained by a number of reasons:
a) Increasing maturity of both oil and gas fields. For gas fields, the effect of
depletion results in an increasing need for compression, and for oil fields,
increasing water cut and water re-injection policy results in an increase of
b) Similarly, the flaring/venting reduction objectives lead to reinjection of
associated gas resulting in higher energy requirements for gas
c) The future issues are deep and ultra deep offshore developments, acid gas
fields, LNG, oil sands and oil and gas shales. In all cases, energy needs
are higher due to water depth, H2S and CO2 treatment of acid gas with
high levels of acid contaminants, liquefaction of gas for transportation to
markets, development of oil sands and oil and gas shales all these
requiring energy intensive processes. This will be discussed in the second
part of this paper through actions developed to improve performances of
TOTAL has decided to focus on energy efficiency activities since 2006, under the responsibility of
one energy efficiency coordinator. Alongside the coordinator, a transverse multidisciplinary team has been
created with specialists from headquarter and from affiliates deeply involved in the day to day activities;
As part of the energy efficiency plan implementation, it was decided to carry-out an evaluation of
each operated asset within all TOTAL’s affiliate around the world and to establish a performance
improvement plan. Prioritization of existing assets to be assessed was based on internal reporting, giving
data in term of GHG emissions and fuel consumptions.
A specific internal methodology has been developed and it was decided to test its implementation
within two affiliate's pilots:
- one dealing with mature oil assets with no gas market for valorisation of associated gas,
- one dealing with gas and condensate fields operated under the European legislation in term of
As the methodology demonstrated positive results for these two pilots, it has been decided to deploy
it on all operated assets of TOTAL Exploration and Production, with prioritisation as describe later.
Methodology and associated results.
The objectives of the energy assessment are to:
- quantify the use of energy and identify the main energy consumers
- establish reliable values of consumptions and losses on assets which give a reliable baseline for
the considered asset at the time of energy assessment,
- define opportunities to reduce the consumptions and losses and when possible opportunities to
increase oil and gas production
- propose short, medium and long term actions with a preliminary technical and economical
evaluation to allow a prioritisation of these actions.
The first action to be implemented is a site visit by two experts, one in rotating machineries and one
in process/operations. During this site visit, from few days up to 2 weeks according to the complexity of the
asset, all relevant data such as Piping and Instrument Diagrams (PID), electrical schemes, equipments data
sheet, GHG emissions reporting, recent daily production reports, collected before the site visit, are discussed
with the site crew as well as operational issues. During this phase it is crucial that all specialists of the
affiliate and the site are involved in the discussion and in the elaboration of a first list of opportunities that
could lead to energy consumptions improvement. First because they perfectly know their equipments and
operation issues and secondly because a high involvement of the site and affiliate team at this stage of the
process will lead to a better involvement in the implementation of proposed actions.
At the end of the site visit, the final debriefing with all concerned persons in the affiliate shall cover
the energy baseline results, with description of main consumers and all opportunities identified to improve
the energy consumptions, and/or optimization of production.
Systematically all these opportunities of improvement identified during the site survey are collected
by the energy efficiency coordinator under a standard file as presented in figure 1. This allows to standardize
the opportunities identified during all energy assessments on various assets, with a detailed technical
description, a preliminary evaluation of benefits in term of fuel gas/electricity/vapour/diesel consumptions
reduction, production increase if any, flaring/venting reduction, CO2 emissions reduction and maintenance
costs reduction. Each opportunity is also preliminary evaluated regarding pay back and economical benefits.
Fig. 2: standard file for opportunity description and actions decided
After preliminary technical and economical evaluation of all identified opportunities of one asset,
each of them are reviewed and classified by a multidisciplinary team of specialists both from affiliate and
from headquarter, specialists (process, rotating equipments, environment, field operations, and petroleum
architects). Subsequently, for all actions presenting high ‘interest’, a leader is nominated to schedule and
implement the required actions. It should be noted that some actions considered as non feasible (economic
and/or technical reasons) are parked for further re-assessment.
A global evaluation of the benefits of the actions to be implemented either immediately or after
additional studies is done. Specific energy indicators are calculated which allow to define the baseline of the
energy performance of each asset and shows the improvements expected by the implementation of decided
For each asset, the compilation of all proposed actions together with associated schedule, leads to
the elaboration of an Energy Efficiency Plan. Consolidation of all assets of an affiliate, leads to the definition
of consolidated Energy Efficiency Plan for this affiliate.
The overall process is described on Figure 3.
Fig. 3: Methodology and deliverables of energy assessments
For the time being, 23 operated assets of TOTAL Exploration & Production in 5 major affiliates have
been assessed and energy efficiency plans defined, covering about 50% of the energy consumptions of the
Exploration & Production branch. The full deployment of these energy assessments will continue in the next
Applying the same methodology for all assets is a guarantee that all surveys are conducted under
the same scope of work and same level of details of investigation. At the same time, reporting is identical,
and the calculation of same energy indicators allows comparing sites which are comparable in their
characteristics and challenges. This will in a short term lead to a reliable internal benchmark of comparable
About 10 to 20 opportunities are identified on each site, depending of the complexity and the age of
the site, of which about 2 to 5 are rejected for economical reasons.
Among the 10-15 others, some are implemented quite rapidly, directly by the site, as they are not
requiring heavy engineering and modification (quick win but generally low benefit opportunities). For the
majority, opportunities need more detailed studies before final decision of implementation, due to major
modifications on the installation (re-routing of piping, addition of flow meters, etc…). And their
implementation need at least a partial shut down of the installation and thus must be planned with other
Example of energy assessment on a gas field with condensate production:
Total loss calculated during site survey: 1.8% (top quartile of its peers as shown by figure 3)
FIELD A FIELD A
Figure 4: Field A – Ranking in the evaluation of total losses
In order to provide a comparison of energy consumption across the different types of equipment, all
energy consumptions are re-calculated and expressed in thermal value. For electrical power, this
corresponds to the thermal energy used to generate the electrical power (not the electrical power itself). The
thermal energy of a stream is calculated using the Lower Heating Value (LHV) of this stream.
An alternative method of representing this data is the Sankey diagram:
Analysis of Field A case
• Greenhouse gas emission
Fuel gas consumption for compression and power generation represent about 78% of
greenhouse gas emissions on this site where gas and condensates are exported by pipeline.
Vent gas Fuel gas -
Flare gaz generation
Diesel fuel Fuel gas -
Fuel gas -
Figure 5: Field A - Sources of greenhouse gas emissions
• Energy Efficiency
Figure 6: energy distribution as per survey Figure 7: breakdown of electrical load by consumer
- The energy distribution shows that about 60% of energy needs are related to gas export
compression through a pipeline network directly to final gas market; Both booster and
export compressors are turbine driven.
- Electric power is provided through 2 turbines driven generators. The analysis of electrical
load shows that the main consumers are the condensate export pumps and seawater
pumps. It is worth mentioning that for this gas Field A, the overall electrical load is
relatively small (about 50MW), thus there are limited opportunities for reducing
greenhouse gas emissions reducing the electrical load
• Lesson learnt
Several good points of design have been highlighted during the site survey:
- the use of high efficiency turbines with waste heat recovery to cover the heat
requirements of the installation,
- multiple fuel gas meters allowing an accurate follow-up and reporting of fuel gas
- fuel chromatograph (on the export gas line), giving an excellent follow up of fuel gas
- variable speed MOL pump drive
- control simulators.
The site survey team also reported that the installation was well operated and maintained
and found an excellent design of shutdown reports.
• Opportunities for Energy Efficiency Improvement
18 energy saving opportunities have been identified ranging from quick wins through to more capital
intensive modifications. These energy savings opportunities are classified into 5 main categories: operations,
equipment performance, awareness / energy monitoring, business / planning and reporting.
It is estimated that 7 quick win opportunities will reduce the greenhouse gas emissions by almost 5%
of total. One of the most beneficial opportunities involves control loop tuning of the plan in order to improve
its overall stability and so reduce the number of shutdowns. The other 11 opportunities require more studies
and technical and financial efforts and are estimated to allow a further 5% reduction in CO2 emissions.
Finally, it is very important to ensure that the proposed recommendations are taken into account into
budgets and annual plans to guarantee their implementation.
Energy Efficiency Improvement – Good Practice
From a numerous Energy Efficiency assessments on existing assets, it is possible to identify
recurrent energy saving opportunities that can be easily implemented on other assets. This consolidation
work is done by the energy efficiency coordinator.
These recurrent energy saving opportunities can be classified in various categories:
- optimization of operating conditions, including improvement of rotating machines operations,
- re-routing of flows actually sent to vent or flare,
- recovery of some flows such as blanketing gas on some equipments or flash drums vapours,
- better metering among the installation for a better follow up of consumptions,
- re-design of some equipment.
The energy coordinator is in charge to issue a guide of good practices for energy efficiency
On the other hand, the energy assessments systematically report good practices (both on operation
and on design side) which can be also easily implemented. Among them, one can note for instance:
- use of energy efficient turbines (aero-derivatives with higher efficiency than heavy duty turbines)
- installation of Waste Heat Recovery Units on turbine exhaust gas that will increase the overall
efficiency of the turbine by allowing the use of this waste energy for heating purposes on the
- fuel gas meters on main consumers, and as far as possible on individual consumers of fuel gas
(this point is also valid for diesel consumptions),
- use of ultra sonic flow meters on flares
- process heat integration during design
- energy efficient procedures for start-up after shut down,
- dry gas seals on compressors,
Overall consolidation of the information collected during the energy assessments is vital to ensure i)
the success of the methodology i.e. reduction of fuel consumption, ii) an efficient transfer of operational
experiences to the design principle for the future projects.
One challenge is to improve the energy management on our existing assets but another challenge
for the future is to design today the new development that will sustain our production in the years to come.
This is the aim of the next section presenting methodology for new developments.
b. Energy Efficiency in new developments
As already mentioned, the new developments currently under studies will sustain our production of
tomorrow but also our energy efficiency of tomorrow. It is therefore of great importance to take into account
the energy efficiency aspects at early stage of the design, considering the earliest energy efficiency aspects
are integrated, the easiest the integration is possible, and the more cost effective it will be.
The cost benefit of designing energy efficient development should not be directly measured against
capex but taking into account the overall benefit of energy savings over the entire life of the project.
In order to assess the overall benefit of energy efficiency improvement actions, TOTAL has
launched, in parallel of energy assessments on existing assets, actions to be implemented during the design
of new developments as early as the conceptual study level.
It is now mandatory within TOTAL’s development study referential to assess the energy efficiency of
each process scheme proposed for a new development. This allows management to decide and choose the
more appropriated scheme to match TOTAL’s commitment in term of consumptions and energy efficiency.
The main advantage of this approach is a project with an energy architecture carefully studied, with a
more accurate evaluation of consumptions, optimized choice of number of turbines, type of turbines,
redundancy policy. Similarly, all electric schemes, with or without variable speed on compressors and pumps
are compared to mix schemes with turbines and turbo-compressors or turbo-pumps
In order to provide a methodology to assess and compare energy efficiency of different concepts, as
well as for the optimization of the final definition of new development, TOTAL has developed 4 energy
indicators to cover all the specificities of new developments of green fields and re-developments of brown
These 4 indicators are designed to measure, for a given development:
- the auto consumption compared to the production or the overall products that could be valorised,
- the overall consumptions and losses compared to the production or the overall products that could
be valorised immediately or in a near future,
- the efficiency, comparing the energy entering the system to the energy valuable immediately or in a
- the energy intensity comparing all consumed energy (auto-consumed and purchased) to the
These indicators take at different levels and under various configurations the following information:
- valorised production: oil, gas, LNG, condensates, GPL, etc….
- production that could be valorised later: gas re-injected in an adequate reservoir where a blow
down production is later feasible,
- auto consumptions: fuel gas (or oil or condensates or steam) produced on the field and auto
- imported utilities: energy purchased, produced outside the perimeter of the study but necessary for
the production (electricity, diesel, steam, purchased gas, purchased crude oil, etc…)
- losses, both process losses, flaring and venting
- exported utilities: energy produced inside the perimeter of the study and sold to consumers
- gas-lift: gas injected for activation purposes, which comes back together with well production in a
The definition of these key performance indicators provides a common basis for quantification of a
field’s energy performance. The indicators are complementary and provide a characterisation of the project’s
performance on different aspects.
The use of these 4 different indicators helps to compare schemes that are comparable. Each field
has specific characteristics such as its size, the reservoir pressure and performance along the life of the field,
the quality of oil and gas, the pressure maintenance strategy (depletion, water injection, gas injection) and
also the specifications and specificities of exportation.
Obviously a gas field development with LNG production needs much more energy, than a gas field
development with direct exportation by pipeline to a local market. Similarly, acid gas field developments are
also energy intensive projects with the need to deal with CO2 and H2S removal.
As an example, figure 8 gives comparison of auto consumption indicator for various kinds of projects,
varying from about 1 to 2% for oil and gas developments up to 20% in heavy oil developments under Steam
Assisted Gravity Drainage scheme, through 8 to 12% of auto consumption for LNG projects.
In case of redevelopment of mature fields, the comparison is done between the re development
scheme proposed and the do nothing case.
% of production
Mature Heavy Oil
Oil / Gas LNG Mine
Figure 8: Energy needs (expressed in % of production)
In the evaluation of the performances of a new development, the perimeter of the study has to be
defined very carefully, to be sure to compare subjects that are comparable.
Production of utilities
«SOLD» FUEL GAS
Inlet flows REINJECTED GAS
FIELD EXPORTED OIL
GAS Satellites, export pump
GAS LIFT Subsea and surface equipments EXPORTED GAS
DIESEL FUEL GAS
An internal Excel tool has been developed with the description of the methodology and objectives.
This methodology has been applied systematically for all development studies for the past 2 years
allowing the development of a significant data base for comparison purposes. The Excel tool is now fed with
the feed-back from all studies, giving the mean value and best value for each kind of TOTAL new
development project, classified in oil field (with associated gas), gas field, acid gas field, LNG, etc…
Definitively, this tool helps the users to rank their project regarding energy performances among
other TOTAL’s projects and to adapt their choices in order to reach the best compromise. This is illustrated
by the figure 9 where for an on-going study of a new project of Floating Production Storage and Offloading
unit (“FPSO 1”) the energy efficiency indicator values are compared to the mean value and best value of
TOTAL E&P similar FPSO projects.
One important issue in these calculations is to take into account the life of field indicators.
Equipments are often sized and optimised for a plateau rate or peak rate. But looking at profiles during the
entire life of the field, oil (and associated gas) or gas production is decreasing, water production is
increasing; pressure maintenance is also changing in large proportions. Thus power generation,
compressors and pumps are generally efficient during the production plateau and rather inefficient during the
remaining period of production decline. A view at the life of field level, taking into account the forecasted
profiles of oil, gas, water, enables to make better choices. Some examples:
- the number of trains working in parallel,
- the use of variable speed drives,
- the selection and sizing of equipments
all these enabling better adaptation of equipments to the evolution of the real production profiles.
Years 1-2 Years 3-9 Years 10-19 Life of field
FPSO 1 mean FPSO best FPSO
Figure 9: auto consumptions calculated for FPSO1 with
energy efficiency tool
Finally, a Project Energy Review is organized at an adequate time within the schedule of the
development studies, early enough to keep the opportunity to modify the selected concept in order to
improve the overall performance of the project, but not too early as this energy review needs to be done
based on relatively accurate material balances, utilities and power requirements.
Process team is obviously the leader in the discussion to explain their choices, but other specialities
are involved such as rotating equipment or environment senior specialists, and operation team. The
objective is to check, with regards to the list of good practices, what has been implemented and what has
been rejected with associated technical explanation. The list of good practices has been established
internally using the results of previous energy assessments on existing assets. This list is also improved with
results from R&D when innovative technologies can be implemented in our future projects.
The objective of this methodology is to take into account as early as possible energy efficiency
criteria in our new development studies. Today, energy efficiency is one of the key criteria reviewed to
finalize the concept and technology selection within our development studies, just as capital cost, operating
costs and GHG emissions. This will impact positively our performance indicators in the future.
4 Example of energy efficiency improvement on existing installation
One example of improvement in fuel gas consumptions and associated greenhouse gas emissions
given hereafter is purge of flares using nitrogen instead of hydrocarbon gases. This subject has been
highlighted during various site surveys, as a good practice on one site and as opportunity to reduce
greenhouse gas emissions and fuel gas consumptions on other sites.
The flare system is an essential safety part of any offshore or onshore petroleum facility and must be able to
relieve gas from the process during upset or emergency situations.
It is necessary to avoid the air penetration in the tip of the stack that could form an explosive mixture in the
stack or the flare header. This phenomena can happen when the flow of gas through a flare or vent stack is
below a minimum value. Normal design of flare systems is to inject an adequate flow of oxygen free gas in
the system to avoid air ingress and burnback.
Various factors can affect the rate of air ingress:
• Gas density: the rate of ingress increases as the purge gas density falls.
• Stack diameter: the required purge velocity, to maintain similar oxygen concentrations in the stack,
increases with stack diameter.
• Wind speed: as wind speed increases the low pressure area in the stack becomes more marked and
the air ingress increases.
Usual design of flares takes into account the purge of flare headers and stack with HC gas, generally from
the fuel gas system. The flow rates that are needed to avoid air ingress are dependant of the molecular
weight of the gas, the diameter of the stack and the tip design.
Nitrogen with a purity of at least 97% can be used as an alternative source of purge gas.
Hydrocarbon flare purge rates are dictated by the need to maintain a steady flame at the flare tip. This is
done to ensure no lift-off or burn back resulting in damaging the tip, extinguishing of the flame or allowing an
explosive atmosphere to develop within the flare stack or headers.
Nitrogen purge rates, when applied to flare stacks, are not affected by these criteria, as they are not required
to maintain a flame. Instead, the aim of the nitrogen flow is to create and maintain a positive pressure in all
points of the flare system. The purge rate is dictated by the diameter of the flare stack, not by burner type or
design, with flow rates only having to be high enough to prevent air ingress into the flare stack.
Actually the quantity of nitrogen required is slightly less than the amount of low molecular weight fuel gas
Air supply is needed to generate nitrogen, as the basic principle is to separate oxygen from atmospheric air,
using either Pressure Swing Absorption (PSA) or membranes technologies. An air compressor skid is thus
required, which is sometimes not included by the suppliers in the nitrogen generator package.
An example of balance between fuel gas purge and nitrogen purge is given hereafter:
Purge and pilot Fuel Gas N2 purge and pilot fuel gas
Flow rate 2400 Nm3/h 2250 Nm3/h (note 1)
Power / fuel gas consumption for N2 300 kW (0.15 MMSCFD)
Power / fuel gas consumption for air 200 kW (0.1 MMSCFD)
Associated GHG emissions (kton CO2/year) 53 7
Note 1: designed for both flare purge needs and other blanketing requirements
Nitrogen (N2) production skid is designed for delivering N2 with a purity of at least 97% at a discharge
pressure of 5.5 bars. Air compressor is designed to deliver 6000 Nm2/hr to comply with the nitrogen skid.
In this case, the net reduction of fuel gas of about 1.7 MMSCFD represents an immediate gain of gas
production at gas market price.
And the net reduction of greenhouse gas emissions will represent 46 kton CO2/year, which represents in this
case a reduction of about 13% of the overall emissions of the site.
In case of retrofitting of an existing installation, flare networks often offer existing nitrogen connections, the
purpose being to purge the system during start-up and maintenance phases. Those connections could be
used for continuous nitrogen purging of the flare system. It is also still possible to inject nitrogen exactly
where the fuel gas is currently injected.
For periods where the supply of nitrogen is interrupted, during routine maintenance of the nitrogen system or
failure of the nitrogen skid, a back-up of fuel gas is required to maintain the purge to the flare stacks.
Decision to install a nitrogen purge system on an existing installation has to be studied carefully, mainly on
the two following points:
- other hydrocarbon permanent release to the flare from specific process equipments, often named fatal gas.
This is the case of various blanketing gas, for instance on oily water treatment, oil storage tanks on FPSO,
some closed drains and glycol drain drum. Another example is stripping gas in glycol regeneration units, to
reach the final specification of water content in the gas. In most cases, fuel gas can be replaced by nitrogen
gas considered as an oxygen free gas and thus fulfilling the same goal. After a fine inventory of all
requirements, this additional nitrogen flow must be taken into account in the final design of the nitrogen unit.
- hydrocarbon leaks particularly from valves: a preliminary calculation showed that, above 10 wt% of
methane in the nitrogen purge flow, the system has to be switched back to HC gas purge. Indeed, the effect
of venting such quantity of methane becomes more detrimental to the environment than purging with HC gas
which will burn (the impact of methane on global warming is about 21 times greater than that of CO2).
Solutions that can be implemented to follow-up leakage on valves can be either acoustic leak detectors
(which can offer both detection and quantification of leaks through passing valves), or infra-red cameras
(which enable leaks detection but no quantification) or permanent sampling points installed on flare headers.
Finally, pilot flames are another important issue when modifying an existing installation from HC gas purge to
nitrogen gas purge. Pilot burners are provided to ensure a continuous ignition source at the flare stack. The
system consists of multiple continuous pilot burners arranged around the flare tip, supplemented by a remote
controlled pilot ignition system to ensure against flare failure. These pilot burners stay lit even when using
nitrogen purge. But as there is no big flame due to the burning of HC purge gas, two risks of extinguishment
of the pilot flame are possible:
- if a cloud of non flammable gas around the tip (in case of no wind)
- very bad weather conditions and high speed wind.
A check is necessary with the flare tip provider and one solution is to change the design of the pilot spatial
configuration, pushing the pilot pipes aside of the cylinder.
It is to be mentioned that the pilot flames are generally monitored using thermocouples that are mounted on
top of the flare stack within the flame. This system is effective, even if sometimes be cumbersome when a
thermocouple failure occurs. An extra form of detection is the use of thermal imaging cameras installed to
monitor the status of pilot flames.
However, the operating philosophy of this kind of system is to revert from nitrogen to HC fuel gas as the
purging medium in case of failure of both thermocouples and cameras
The replacement of HC gas purge by nitrogen purge on existing flaring systems is a good example of
improvement of energy efficiency by reducing greenhouse gas emissions on one side as no more gas is
burnt continuously, and by marketing at gas price market the saved fuel gas. This improvement is a quite
light modification of existing installations which pay back is less than two years in our experience.
Another solution can be implemented but only in new developments as it requires a specific design of the
flare system. This solution is a flare gas recovery system, as authorized by API 521. Downstream of the flare
drum, one Fast Opening Valve (FOV) controls its upstream pressure to be above atmospheric pressure. Gas
from valves leaks, glycol skids, water treatment, is recovered with a compression system. The flare header is
purged with nitrogen instead of hydrocarbon. The flare is then normally unlit. In case of high pressure
detection in the flare network, the FOV opens and the ignition system lights the flare on. In parallel to the
valve, there is a non re-closing item (such as a bursting disk or a buckling pin valve) installed as a back-up in
case the FOV fails to open. This equipment is of high importance to prevent explosion in the flare header,
which is not designed to resist high pressures. Installation of two bursting discs in parallel, set at different
pressure levels, may be considered in order to increase protection. In case of failure of the system, natural
gas purging is resumed and the flare lit.
5 Conclusions and Perspectives
Most of exploration and production emissions come from combustion of fuel gas or diesel to provide
our projects with energy requirements. Therefore improving energy efficiency must be at the core of our
programmes to maximise sales products and reduce greenhouse gas emissions, in parallel to our actions in
reducing and stopping continuous flaring.
Optimizing operation conditions, sharing best practices, taking the energy factor into account right
from the beginning of any new project and implementation of new technologies or process schemes are the
key action levers to improve the performances of our production industry.
Performance management, both of existing assets and future projects, needs a multidisciplinary
involvement and at all levels of the organization: operations, process, rotating equipment, environment
teams are the keys of the success.
Finally, our future consumptions are at studies level today: it is the more cost effective way of
improving our future emissions levels compared to the modifications of existing installations. Energy efficient
architectures and processes need to be implemented and competitive results from research need to be
included as soon as possible in these new developments.
Some ways of improvements are to be more largely developed in the future: sub sea processing
allowing direct re-injection of fluids (water or associated gas) rather than bringing them to the surface before
re-injection, long multiphase tie-back to centralize process centres and thus energy needs, larger use of
alternative energies in addition of overall needs, all electric architecture with variable speed drives and
cogeneration for big projects with high amount of energy requirements.
 Energy Technology Perspectives 2008 (International Energy Agency)
 CAPP (Canadian Association of Petroleum Producers) – Module 4 - Efficient Use of Fuel Gas in
 API 521, p 141-145