An E&P Industry Perspective on Acceptability Criteria for the Marine Discharge of Cuttings Drilled with Synthetic Based Drilling

Abstract

Abstract This paper discusses the issues that the oil and gas exploration and production industry (the E&P industry) considers to be of importance in the development of acceptability criteria for the marine discharge of cuttings from drilling with synthetic-based drilling fluids. Synthetic-based drilling fluids are used to improve performance when drilling through sensitive formations, under extremes of temperature and pressure, and when drilling highly deviated wells. Synthetic-based drilling fluids are designed to have improved environmental behaviour, particularly with respect to persistence, compared with conventional oil-based drilling fluids. Drilled cuttings must be removed periodically from the drilling rig due to limitations on storage capacity. Drilling operations are often carried out under conditions in which technical and logistical factors make zero discharge operations highly impractical. As a result, marine discharge, subject to appropriate controls, is a management option that must be considered for cuttings from drilling with synthetic drilling fluids. The E&P industry supports the use of scientific criteria based on consideration of persistence in the receiving environment, toxicity and potential for bioaccumulation to determine the acceptability of marine discharge of drilled cuttings. Consistent with that support, industry associations and individual operators are cooperating with regulators to develop practical laboratory testing protocols and monitoring programmes. Progress has been made towards developing practical laboratory techniques to assess the relative degradation rates of different base fluids under conditions relevant to the seabed environment. However, new methods for measuring biodegradation rates should be validated according to accepted procedures before adoption as the basis for regulatory controls. Practical and robust testing methods are needed to implement acceptability criteria and to provide for the development of new drilling fluid technology. The relationship of acceptability criteria and practical test methods to the complex natural seabed environment needs to be established to provide a reasonable basis for relating test results to environmental effects. The seabed surveys and laboratory studies now underway or recently completed will provide valuable insight into this issue. Based upon these factors, the E&P industry recommends that: Acceptability criteria for marine discharge of drilled cuttings from drilling with synthetic-based drilling fluids (1) be developed based on consideration of environmental risk factors such as persistence, toxicity and bioaccumulation, and (2) be implemented by means of practical and robust test methods. Agreement be pursued on clearly defined criteria for the acceptability of synthetic-based drilling fluid materials for discharge to facilitate the development of new and environmentally acceptable drilling fluid technology. Criteria for marine discharge provide for exceptions for essential use on a site- specific basis, considering technical drilling requirements, safety, assessment of environmental risk and the practicality and environmental effects of zero discharge alternatives.