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Abstract

The U.S Environmental Protection Agency (EPA) recently published effluent guidelines on the appropriate use of synthetic-based drilling fluids (SBFs). These regulations control what types of SBFs are allowed for discharge and how much SBF can be retained on the cuttings directly discharged to surface waters. In order to provide operators with greater flexibility in complying with the new controls on SBF cuttings, EPA promoted an alternative compliance option based on the use of Best Management Practices (BMPs).

This paper provides an overview of the SBF BMP compliance alternative, its use among operators, and elements of an effective BMP Plan. This paper focuses on implementation aspects and identifies potential benefits for operators using the BMP compliance alternative. In addition, this paper presents a comparison of SBF discharges associated with cuttings for SBF wells that did and did not use this compliance alternative. Monitoring data indicate that discharges from SBF wells using the compliance alternative are lower than the discharges from SBF wells that did not use the compliance alternative. Finally, this paper examines the degree to which operators are on a cycle of continuous improvement and expanding beyond this compliance alternative on a voluntary basis to examine other areas for pollution prevention and reduction of pollutant discharges.

Introduction

The U.S Environmental Protection Agency (EPA) recently published technology-based regulations which support the use and development of synthetic-based drilling fluids (SBFs) as a pollution prevention technology (January 22, 2001; 66 FR 6850).¹ Rabke et al² outlines the expedited steps EPA used to develop these new technology-based controls and the close cooperation between EPA and industry stakeholders during the rulemaking process. EPA incorporated these new SBF limitations and standards into the Western Gulf of Mexico (GOM) National Pollutant Discharge Elimination System (NPDES) permit which regulates most offshore oil and gas extraction activities (December 18, 2001; 66 FR 65209) and became effective on February 16, 2002.³

EPA identified a number of pollution prevention benefits of using approved SBFs in place of traditional water-based drilling fluids and oil-based drilling fluids including potential lower air emissions and pollutant discharges to surface waters. The technology-based controls in these regulations also promote pollution prevention by encouraging more efficient solids control technology to increase recycling of SBF in the drilling operation. Increased SBF recycling reduces the quantity of SBF required for drilling operations and the quantity of SBF discharged with drill cuttings.

EPA used a two-part approach to control SBF-cuttings discharges. The first part is the control of which SBFs are allowed for discharge through use of stock limitations (e.g., sediment toxicity, biodegradation, PAH content, metals content) and discharge limitations (e.g., diesel oil prohibition, formation oil prohibition, sediment toxicity, aqueous toxicity).⁴ The second part is the control of the quantity of SBF discharged with SBF-cuttings. EPA identified that the retention limit is a very important control because it controls: (1) the amount of SBF discharged to the ocean; (2) the biodegradation rate of discharged SBF; and (3) the potential for SBF-cuttings to develop cuttings piles and mats, which are detrimental to the benthic environment.

EPA allowed operators two choices to demonstrate compliance with the SBF retention on cuttings (ROC) limitation. Operators may choose to either comply with: (1) a single numeric discharge limitation with cuttings monitoring on the entire SBF well interval; or (2) a set of best management practices (BMPs) developed by the operator, with reduced cuttings monitoring. EPA identified that BMPs require performance-based measures in order to maximize their effectiveness. In comments on the rulemaking, industry also stated that BMPs would be extremely effective at reducing the quantity of non-cuttings related SBF and would focus operator attention on reducing these discharges.⁵