1. SHIPPING AND MIXING - How are chemical mixtures permitted and reported?

Operators are allowed to ship chemicals to the installation that are not listed on their permit, however chemicals must be on the permit before use although the mixing of any chemicals/muds in the pits is allowed.

 In recognition of Health and Safety requirements/concerns, pre-mixing or pre-diluting of products onshore is acceptable providing all products in the mixture are registered with CEFAS.  All products should be listed on the permit and should also be reported to EEMS as normal.  Both the applications and the returns must relate to a specific certified chemical, not the amended form of the chemical i.e. if a chemical is certified as a 100% solid, the application should indicate how much of the 100% product will be used and/or discharged, even if it is supplied to the installation in a different format e.g. a 50% solution.

The Offshore Inspectorate will be able to check how the concentrate is being used when they are offshore.  The operator is obliged to use the product as specified in the certification documentation.

 The Portal (and non-Portal) application entries and the EEMS return entries should relate to the form of the chemical that has been certified.  The chemical manufacturer or supplier who certified the product will specify the formulation that has been submitted for certification.  All applications and returns should then be related to that specification.

 The use of any chemicals generated offshore must be recorded in the PON15D.  In the case of sodium hypochlorite, it is the ‘available chlorine’ in the product which is recorded, not the volume of the product.  

  1.      ENVIRONMENTAL IMPACT ASSESSMENT – Pipeline Discharge & Scale Squeeze Operations - How is the Risk Quotient (RQ) calculated for pipeline discharge operations?

 The CHARM Implementation Network (CIN) suggested approach to calculate a risk quotient (RQ) for Pipeline Discharge operations:

 The RQ can be obtained using the Completion and Work-Over algorithm for which the entries would be as follows:

  •  Set Chemical type to surface and well ceaning;
  • Set Dose as the dose of substance applied to pipeline;
  • Force Dilution Factor to 0.001;
  • Set Fraction released to unity (1);
  • Enter Toxicity information from the data sheet;
  • The RQ output can be used as an HQ, for ranking and comparison purposes;
  • For a ‘real’ risk quotient calculation it would be necessary to use more detailed hydrodynamic modelling.  There is a range of dilution models available to the modeller.


The CHARM Implementation Network (CIN) suggested approach to calculate a hazard quotient (HQ) for Scale Squeeze operations: 

  • Select the “Completion and Work-over” algorithm;
  • Set Type of chemical’ to ‘Other completion/work-over chemical’;
  • Set the dose as the initial concentration in the injection in units of mg l-1;


Set the fraction of chemical discharged to 0.3;

Accept the RQ output as an HQ and use this for ranking and comparison purposes


The CIN suggested approach to calculate a risk quotient (RQ) for scale squeeze operations:


The dose should be the best estimate of the peak concentration (in the initial return slug);

Set ‘Fraction released’ to unity (1);

Calculate the batch-wise dilution factors using the tables at the back of the manual if for any completion and work-over chemical;

It will usually be necessary to use the “Standard” Production Chemical algorithm to model the tail of the return profile.


There are not definitive methods for carrying out a chemical risk assessment of a pipeline discharge or scale squeeze operation, and the Department will consider alternative risk assessment methods/models when presented with the appropriate scientific evidence.


  1. USE OF EXISTING STOCKS OF EXPIRED PRODUCTS - Can existing stocks of expired chemicals be used?


  1. a)When the HOCNF certification of a product expires, the product will be removed from the CEFAS lists of approved chemicals.  Applications for chemical permits must not include "expired" products that are no longer on the approved lists.


  1. b)All products included in a permit application must be on the approved lists at the time of submission of the application.  If there are any expired products included in an application, they will be rejected and the applicant will be requested to seek alternative products.


  1. c)If a product will expire during the period between submission of the application and the date of commencement of the requested permit, the Department will require confirmation that the product has been, or will be, submitted for re-certification.  If an applicant fails to provide this confirmation, the product will be rejected and the applicant will be requested to seek an alternative product.


  1. d)If an applicant provides the requested confirmation under Paragraph c, but the re-certification process has not been completed prior to commencement of the works, the applicant will be able to use existing stocks of the expired product, subject to the conditions outlined in Paragraphs f-i below.


  1. e)If a product will expire during the period of validity of the requested permit, the applicant will be able to use existing stocks of the expired product, subject to the conditions outlined in Paragraphs f-i below.


  1. f)All chemical permits will contain a condition requiring the permit holder to notify the Department in advance of any proposed use of existing stocks of an expired product.  The notification will be filed/stored alongside the permit, so that use of the product is not interpreted as a breach of the permit conditions when the Department reviews the (EEMS) permit return.


  1. g)Existing stocks of an expired product must be the property of the permit holder or an agent undertaking the operation on behalf of the permit holder (e.g. a drilling or pipeline installation/testing contractor).  There must be a clear audit trail to confirm ownership.


  1. h)Existing stocks of an expired product can be held at the site of the works; at any onshore premises operated by the permit holder; at any onshore premises operated by an agent undertaking the operation on behalf of the permit holder; or at any onshore premises operated by any other agent acting on behalf of the permit holder (e.g. a harbour authority, supply base operator, supply vessel operator or even the chemical supplier).  Wherever the stocks are held, there must be a clear audit trail to confirm ownership of the chemical mentioned in Paragraph g.  It is also recommended that copies of the chemical permit and the notification referred to in Paragraph f should be held by any agent that could be involved in the provision of an expired product.


  1. i)The permit holder, or the agent undertaking the operation on behalf of the permit holder, is not allowed to obtain additional stocks of an expired product from any third party.  Inspectors appointed under the Offshore Chemicals Regulations 2002 will be entitled to request copies of the documentation relating to the audit trail to confirm ownership of stocks of expired products.  Obtaining additional stocks of a product after it has expired will be treated as a serious offence.


  1. DIESEL BIOCIDES - Is the use of biocide in fuel subject to the Regulations?


There is no requirement to include biocides added to diesel (or other fuels) in chemical permits.  This decision recognises that biocide use in fuels does not constitute an "operational use" of a chemical, and takes account of the OSPAR "Common interpretation on which chemicals are covered and not covered by the harmonised mandatory control system under OSPAR Decision 2000/2". 






  1. USE OF DIESEL AS A SOLVENT OR CARRIER - Is the use of diesel as a solvent or carrier subject to the Regulations?


Diesel is occasionally used operationally as a solvent or carrier, for example during squeeze operations.  In all cases, the diesel is not discharged to the sea, and it is usually left down-hole or combined with the produced fluids.


Diesel is not notified and included in the approved chemical lists, and there is no intention to ask suppliers to submit diesel for classification.  It will therefore not be included on the drop down chemical lists that are used to complete the online applications.  All operational use of diesel should be explained in the justification.


As diesel will not be included in the chemical tables that will form the basis of the chemical permit, its use should not be reported in the term or annual return.


  1. CHEMICAL CUTTERS - Is the use of chemical cutters subject to the Regulations?


Chemicals used to cut well tubulars are not covered by either the OCNS approval procedure or the chemical permitting system.


The most commonly-used chemical cutters are based on bromine trifluoride which, when used under high pressure, becomes a gas that is directed at the surface of the pipes.  In view of the small quantities of chemical involved and the minimal environmental impact, cutters based on bromine trifluoride have been excluded from the chemical permitting system.


The Department will consider other chemical cutters on a case-by-case basis, and will advise operators accordingly.


  1. CHEMICALS SUPPLIED FROM ONSHORE FACILITIES – Are chemicals that are supplied from onshore facilities subject to the Regulations?


Chemicals supplied from onshore facilities via a pipeline or umbilical, which are then injected into the export stream and returned onshore for regeneration, are not covered by the Offshore Chemicals Regulations 2002, and do not require to be on the approved lists.  This also applies to pipe dopes/dope substitutes/dope-less friction controlling lubricants when they are applied onshore and there is no requirement to replace the chemicals offshore.  Where there may be a requirement to apply dope substitutes or dope-less friction controlling lubricants offshore, the chemicals are covered by the chemical permitting system and therefore are covered by the Regulations.


However, where there is offshore top-up of chemicals supplied directly from onshore, the offshore use must be included in the chemical permit application, as this is considered to be an operational use covered by the OSPAR Harmonised Mandatory Control Scheme (HMCS).  Similarly, where there is offshore discharge of chemicals supplied directly from onshore, the discharge must be included in the chemical permit application. 


  1. CHEMICAL DISPERSANTS – What is the procedure for applying to use chemical dispersants?


Produced water sheens are occasional by-products of the production and processing of crude oil offshore. They are particularly prevalent in calm weather conditions and can be seen at levels as low as 10mg/l or less.  For the majority of produced water sheens, the use of a chemical dispersant is not considered to be best practicable environmental option (BPEO). Improved topsides processing is a preferred route to preventing sheen formation. Nonetheless, there are circumstances in which the Department will grant permission for a dispersant to be used as a topsides produced water treatment.  These circumstances would involve sheens that are routinely present in areas of environmental sensitivity and/or in areas where there are routinely significant numbers of birds present on the surface of the water surrounding the platform.


In all cases, permission to use a chemical dispersant, for the purpose of dispersing a routinely observed produced water sheen, should be sought by application to the Department as part of a chemical permit submission or variation. Since it is not always easy for permit reviewers to identify chemicals intended for use as chemical dispersants, applicants must highlight the fact that a chemical dispersant is intended to be used and provide a full justification for it's use. All applications to use chemical dispersants will be subject to the normal review process by the Department and it's statutory consultees. In addition, use of any chemical dispersant must be declared in an application for a permit to discharge produced water granted under The Offshore Petroleum Activities (Oil Pollution Prevention and Control) Regulations 2004.


  1. MULTIPLE WELL TESTING OF DIFFERENT STRATA – Does the EWT threshold of production of oil in excess of 2000 tonnes and/or for a flow period of more than 96 hours or the production of gas for more than a 96 hour flow period  apply to the sum of all zones tested?


Tests of distinct zones within a well are treated separately, and therefore there is not a cumulative process to determine whether they qualify as an EWT.  In all cases, the final decision will rest with LED, and therefore the Consents Team should be consulted if in any doubt, as the environmental regime for EWTs will only kick-in if there is an EWT consent requirement.


If  none of the potential tests within each zone exceed the EWT threshold it will be unnecessary to seek a separate Direction for an EWT.  Nevertheless, full details of the test regime should be included in the request for a Direction for the well (the PON15B).


  1. APPROVAL FOR THE DISCHARGE OF SET DOWNHOLE CHEMICAL PRODUCTS - What is the procedure for obtaining approval for the discharge of set downhole chemical products?


When Liquid stone is mixed with a liquid stone activator and then pumped downhole over the perforations, the product sets hard and the excess is milled out using coiled tubing and discharged to sea.


The most appropriate way to deal with this discharge is to permit the 'Use' of product with 'zero' discharge. Any solid discharged should then be quantified and explained in Section C of the PON15B.


This approach could be mirrored for other solids that are routinely pumped downhole as liquids and then milled out later as solids. The common example is cement which is often milled days, weeks or months after setting down hole. Currently approval can be gained for the use and discharge of liquid cement but not solids.


Liquid stone should be included as 'use' under section G and the discharge of the milled solidified material should be detailed in section C Justification with a quantification of the likely amounts. The discharge column in section G should be 0 with an asterisk to detail the only discharge will be as milled solidified material and that further details are provided in section C.


  1. ZERO DISCHARGE BREACH - If there is a discharge of a chemical currently on a permit with a use quantity but a zero discharge would this constitute a breach of permit conditions if the discharge was under 10%?



3)     Permitted quantities of chemicals

The permit holder shall ensure that the quantities of all chemicals used or discharged during the course of the operations covered by the permit do not exceed by more than 10% the quantities detailed in the permit application.  In the event that the permit holder becomes aware that the use or discharge of any chemical may exceed the quantity detailed in the permit application by more than 10%, the permit holder must notify the Department within two working days.


The above condition refers to an increase in discharge by no more than 10% of that permitted and must be notified within 2 working days to DECC.   It is of the opinion that moving from zero discharge to making a discharge would be a variation in the fate of the chemical and not simply an increase in discharge and therefore would not be permitted under condition 3. This opinion is based on the fact that moving from no discharge to undertaking a discharge may require a CHARM calculation and may result in a different assessment of the likely impact.



Therefore in DECC's opinion, if a discharge of a chemical is made where the original application stated zero discharge, then this would constitute a breach of permit conditions.



Oil&Gas Field Profile

Refinery&Maren Profile


About us





Contact us


f t t