Atmospheric Emissions – Process Venting and VOC Emissions from Offshore Loading


Note – VOC emissions from offshore loading are covered by the Vent Consent requirements under the Energy Act 1976.

Key Legislation:

For more detail on the Legislation relevant to this page, please use the following links:

Supporting Legislation:
Emission Trading Schemes:
Guidance Notes: The Oil and Gas Authority (OGA) is now responsible for venting consent.They have issued guidance on the review of flare and vent applications during commissioning and production operations, available here.

Field Consents Guidance

Flaring and Venting during the commissioning phase Guidance

Flaring and Venting during the production phase Guidance

Consent Needed: Consent to Vent is required under the Energy Act 1976. For Vent Consents both the inert gas and the hydrocarbon faction obtained from the licensed area must be included in the consent application, and the combined rate for both will be the consent basis. Consents to vent are required for all Category 4 (Unignited Vents) including venting of gases from onboard crude oil storage tanks including FPSOs during crude oil filling operations (see the Performances Standards tab). Where a field is venting > 5 tonnes per day the vent level will be reviewed and a vent consent issued annually. These applications will be subject to detailed review by OGA and operators must exercise a high level of technical and operational diligence in estimating quantities. This level of vent is considered to represent a potential opportunity for further reduction in levels. These applications will need full supporting details with medium and long term plans for reduction of venting. Where a field is venting < 5 tonnes per day, a longer term vent consent may be applied for/issued (see the Renewal and Variation tab). Less detailed (minimum) information may be provided on the application form for these venting levels.See the Performance Standards tab for options on multiple fields producing across the same facility.

Crude Oil Tankers

From 1 July 2010 all crude oil tankers must have on board a VOC Management Plan approved by the MCA.

How to Apply: Application should be submitted via the UK Oil Portal. The OGA Guidance Notes for the Completion of Flare and Vent Applications provide further information.Venting consent applications should contain the following:

  • A summary of the main points of the application
  • A summary of the main venting assumptions
  • A detailed description of the plant start-up procedures and philosophy; the procedure for filling the gas export line should also be described
  • The commissioning schedule
  • Venting calculations – to include venting on a daily basis and total quantities. The quantities of gas should be presented on the same basis as the hydrocarbon gas in the Flaring Consent application

Sketches and figures should also be supplied for:

  • Overall commissioning programme
  • Fuel gas system
  • Gas dehydration system
  • Gas compression system
  • Gas export system and pipeline
  • Onshore facilities
Who to Apply to: Applications to be submitted to the UK Oil Portal 
When to Apply: Consent(s) should be submitted at least two months before ‘First Oil’ and towards the expiry of the existing consent for operations. However, it is advised by BEIS and OGA that the operator is in contact with the regulator at all stages, from design through construction to commissioning planning, and demonstrate that all reasonable steps have been taken to keep venting to a minimum.
Limits Placed on Vent Volumes:

Consent will specify the vent volume that must not be exceeded over a specified period.

Definition of Unignited Vents: OGA has provided definitions for four categories of flare and vent activities, of which, Category 4 applies to venting.Category 4 – Unignited Vents  This covers inert gases and hydrocarbon gases which may be discharged to an atmospheric vent. The Energy Act requires both the inert and hydrocarbon gases obtained from the licensed area that are vented to be covered by the consent. This should also include venting of gases from onboard crude oil storage tanks, e.g. for FPSOs during crude oil filling operations. However, this excludes inert gases that are generated on board the installation for the purpose of providing an inert blanket for on board oil storage tanks.Vents may contain nitrogen, carbon dioxide, water vapour, hydrocarbons and possibly traces of sulphur compounds, etc. Operators should give an estimated annual average composition of vented stream(s) in the notes section of the vent application.
Multiple Field Tie-ins to Single Facility: Where several fields tie-in to common facilities and venting is < 5 tonnes per day, and the fields have the same operator and licensees, the operator may apply for a single composite consent and the level of venting permitted in this consent will be based on the sum of the individual field contributions to the total vent level.Where the fields have different operators and licensees, separate consents will usually continue to be issued. However, if all parties agree to apply for a single vent consent covering all the fields going into the facilities and the total vent level is < 5 tonnes per day then a combined 3-year vent consent will be considered.
Vent Volumes: Daily vent and cumulative vent volumes.
What to Report: There are two types of reporting required for venting. The first is statutory reporting to OGA on vent volumes. The second is additional reporting of environmental emissions due to venting through EEMS for the UK-PRTR and E-PRTR (see Atmospheric Emissions Reporting).Vent Consent Reporting to OGA with periodicity and details as specified in vent consent.EEMS Reporting Complete atmospheric emissions inventory EEMS pro forma (Atmospheric) and guidance notes can be obtained from the EEMS website.
Who to Report to: Vent Consent  OGA Petroleum Production Reporting according to terms of consent.EEMS Reporting Completed forms should submitted electronically to the EEMS website.
When to Report: Vent Consent  As specified in consent.EEMS Reporting Annually before 7 February.
What to do if in Breach of Consent: This is reported through the routine vent consent reporting.
Offshore Inspection: The BEIS (then DECC) Offshore Oil and Gas Environment Unit Enforcement Policy sets out the general principles that Inspectors shall follow in relation to enforcement, including prosecution.
Duration of Consent: Applications can be made for vent consents on an annual basis or for a 3-year period (e.g. 2010-2012), depending upon the total daily hydrocarbon vent level from a field. Long term vent consents will not be permitted for any field that seek permission to vent at rates in excess of 5 tonnes a day. If a field is venting less than 5 tonnes of hydrocarbon gas a day, and if, for the period 2010 to 2012 the vent application does not request any increase in the levels permitted in the extant vent consent, licensees can apply for a three year vent consent. If this application is approved by the Department, a long term consent will be issued, subject to a number of conditions (see OGA Guidance on the review of Flare and Vent Applications).
When to Renew Consent/Exemption: OGA will invite applications for renewal in September each year, with annual consents being issued in December for the following year.
Pending Legislation: None at Present.
Updated Energy and Emissions projections: 2015 A report detailing projections of the UK emissions performance against national greenhouse gas targets under existing policies has been released by BEIS. It includes projections of the demand for each type of fuel for different sectors of the economy. The report includes projected energy demand for electricity and indicates what mix of generation will meet it (link here).
Cold Flaring: This is considered a venting activity and is controlled under the venting consent. It should not be reported as flaring or counted against the flaring consent.