The Department of Trade and Industry (DTI) regulates environmental aspects of the UK offshore E&P industry. The Scottish Office Agriculture, Environment and Fisheries Department (SOAEFD) and The Centre for Environment, Fisheries and Aquaculture Science (CERES - formerly part of the Ministry of Agriculture, Fisheries and Food) provide the DTI with specialist scientific support.
The UK is a Contracting Party to the Oslo and Paris Commission (OSPAR or PARCOM), which regulates international aspects of offshore discharges to the North Sea and North East Atlantic. Regulations applied on the UKCS have to be compatible with OSPAR Decisions and are thus greatly influenced by pressure from other Contracting Parties to OSPAR, such as the Netherlands, Norway, Denmark and Germany.
Current UK regulatory framework
Water Based Muds (WBM): There are no specific controls on the discharge of WBM to sea, although chemicals added to WBM are regulated under the Offshore Chemicals Notification Scheme (OCNS). It is considered unlikely that any additional restrictions will be placed on the discharge of WBM as available evidence suggests that the impact on the environment is low.
Oil Based Muds (OBM): The discharge of OBM to sea is regulated under exemptions to the Prevention of Oil Pollution Act (1971). Discharges have been increasingly restricted, and an Oil on Cuttings (OOC) limit of 10 g/kg now applies to all wells (effective 01/01/97). This limit is not achievable using proven techniques and technologies. In practical terms, the imposition of the 10 g/kg OOC limit can be taken as an effective ban on the discharge of OBM cuttings.
Synthetic muds (synthetic mud): Current UK legislation affecting the discharge of synthetic drilling muds to sea can be summarised as follows:
synthetic muds are regulated under the Offshore Chemicals Notification Scheme (OCNS) - their discharge to sea is only permitted when muds are allocated to the least hazardous category (Group E) of this scheme. Other controls on the discharge of synthetic muds include:
An upper limit for OOC (as synthetic mud base oil) of 100 g/kg. This used to be requested "when achievable," but is increasingly being required by the DTI as a condition of discharge;
No discharges from larger hole sections (>16 ins), other than in exceptional circumstances (operators to justify such discharges to DTI);
Operators are required to carry out sea bed surveys to investigate the fate and effects of discharges under field conditions. This is a conditional requirement depending on the availability of survey results. SOAEFD consider that results from five surveys provide a reasonable basis for assessing the environmental properties of each synthetic mud. Requirements for sea bed surveys are increasingly applied only when using new muds.
UK regulatory developments
The results described above challenge the scientific robustness of the regulatory framework governing synthetic muds, and the DTI has responded by proposing the following controls on their discharge to sea:
· Discharges of synthetic muds above a 1% oil on cuttings limit to be phased out over a four year period.
· All classes of synthetic mud base oils will be subject to the same phase out programme, with the possible exception of esters;
· Pending further evidence from seabed surveys the discharge of ester based muds will continue to be permitted;
· Reduction targets will be applied on a company-by-company basis, with operators free to determine how targets shall be achieved.
DTI have discussed and agreed these controls with other Government Departments, UKOOA and EOSCA (European Offshore Speciality Chemicals Association), and they were presented to a PARCOM meeting in February 1997 as the UK strategy for regulating synthetic mud discharges. These proposals were provisionally accepted by Parcom pending a workshop on the impact of synthetic muds to be hosted in the UK in November 1997. Following this workshop a final position on legislation will be decided by Parcom in February 1998.
As noted above, a decision about the esters has been deferred until results from sea bed survey studies are available. Company carried out such a study several years ago, and results showed little degradation. If other studies on the UKCS confirm this, then the esters will be subject to the same controls as other synthetic muds. Note in this context that studies have been carried out in both Norway and the Netherlands which appear to show that esters degrade relatively rapidly under field conditions. However, the experimental design of the Norwegian study has been widely criticised, and the relevance of the Dutch study to conditions in the Central and Northern North Sea is questionable.
Following on from this, there are indications that the Government will define criteria to determine the environmental acceptability of new drilling muds, based on persistence in the environment. This would provide an opportunity for mud companies to develop new products.