Marine Chemical Discharges – Introduction and Background

Chemicals are used offshore in oilfield applications for a variety of purposes; to assist production, for drilling, or in pipelines. Types of chemicals used include corrosion inhibitors, scale inhibitors, anti-foaming agents and demulsifiers.

Chemicals are added to either the injection water or to the produced fluids in order to: protect the installation, protect the reservoir, maintain production efficiency, or to separate the oil/gas and water.

After chemicals have been added to fluids, they partition between the produced fluids; some dissolve primarily in the oily fraction, some primarily in the water fraction, and some in both. Chemicals which move into the water phase are released into the environment with the produced water.

Drilling muds are liquids used in drilling operations to cool and lubricate the bit and to control pressure in the well. Muds are pumped down the drill string, through the bit and back to the surface carrying the drill-cuttings through the annulus. Drilling muds can be divided into three broad categories depending on the base fluid used, namely, Oil-Based Muds (OBM), Synthetic-Based Muds (SBM) and Water-Based Muds (WBM). OBM and SBM are jointly referred to as organic phase fluids (OPF). In addition to the base fluid, drilling muds contain barite and a variety of chemicals which are added to give the mud the desired properties.

The use and discharge of all chemicals is heavily regulated through a process which requires that only pre-tested chemicals are used and their effect on the environment is assessed before use and discharge.

Marine Chemical Discharges – Key Statistics and Commentary

Marine Chemical Discharges

Figure Env12 displays the amount of chemicals used in oilfield activities that were discharged to the marine environment in 2002-06. 2006 data is a projection, as Q4 chemical discharge returns are currently outstanding from the new EEMS system. Based on the projection of average Q1-Q3 data, the tonnages of ‘production’ and ‘pipeline’ chemicals have decreased but the discharge of drilling chemicals has increased by approximately 26 tonnes. Q4 may have experienced less drilling activity than Q1-3 in 2006 and so this total amount may decrease when Q4 chemical discharge data is reported to EEMS.

UKCS Chemicals discharged by Type 2002-2006

Marine Chemical Discharges – Supplementary Information

For further information on the legislation governing the use of drilling chemicals offshore, please visit:
Oil & Gas UK Environmental Legislation Website -
http://www.ukooaenvironmentallegislation.co.uk/Index.htm

CEFAS Offshore Chemical Notification Scheme website -
http://www.cefas.co.uk/offshore-chemical-notification-scheme-(ocns).aspx