Emissions Document Directory > Drilling

This section  provides a directory of documents on procedures and  techniques for mitigating and managing drilling operations and drilling discharges, or are case studies of 'best practice' in drilling operations.

During drilling, specially formulated fluids called "muds" are used to cool and lubricate the drill bit, control pressure and bring the cuttings (rock or sand from a borehole) back to the surface. These muds are most commonly based on water (WBM), but in some cases mineral oil (OBM) or synthetics (SBM) believed to be more biodegradable. Although the use of WBM is preferred, sometimes OBM or SBM has to be used when drilling conditions are more difficult.

Inevitably, when drilling with OBM, rock cuttings are contaminated with oil from the muds. In the past, when working offshore these cuttings were often discharged of sea, in accordance with local regulation.

Where OBM is used offshore, the spent mud and cuttings are now  re-injected or transported to shore for treatment and disposal, or recycling.

The objective of environmental management of drilling operations is to attempt to minimise the potential environmental impacts.

• There are now drilling technologies that offer opportunities for minimising environmental impacts, but not all are applicable to every drilling operation.

• Opportunities to use these technologies are among the elements to consider in preparing the drilling plan.

• It is important to facilitate research and development to improve drilling technologies and achieve the overall objective as stated above.
  (Expert meeting Noordwijk 1997)

Drilling rig in the North Sea