High-performance non-aqueous drilling fluids (NADFs) are required to meet the challenging technical requirements of many offshore wells. Significant advances have led to the development of advanced NADFs, such as paraffins, olefins and esters, that are less toxic and more biodegradable than early generation diesel and mineral oil base fluids. Advanced NADFs provide the necessary drilling performance while ensuring environmentally-sound operations. Three options exist to manage waste from NADF-coated drill cuttings: marine discharge, downhole injection, and hauling to shore for land disposal. All options have advantages and disadvantages with regard to total life cycle environmental impact, safety, cost, and operational performance. Marine discharge of cuttings associated with advanced NADFs, however, is the option with the highest safety and operational flexibility. Further, the improved environmental performance of advanced NADFs broadens the acceptability of marine discharge. Field monitoring studies at multiple offshore drilling sites reveal a relatively consistent picture of the fate and effects of discharging drill cuttings associated with NADFs. The degree of impact is a function of local environmental conditions (water depth, currents, temperature), the amount of material discharged, and the type of drilling fluid used. More significant temporal and spatial effects were observed at sites that used early generation drilling fluids. Wells drilled with advanced NADFs resulted in smaller zones of seafloor impact and more rapid recovery of the benthic communities. This paper, based on the work performed by a task force of the International association of Oil and Gas Producers (OGP)1, summarizes our knowledge base of the environmental-effects related to the discharge of NADF-coated drill cuttings. In addition, it describes tools and techniques for assessing environmental effects including laboratory methods to determine drilling fluid toxicity, biodegradability, and bioaccumulation potential and numerical models to predict the seafloor distribution of cuttings. The paper is intended to aid regulatory development and project environmental assessments by providing information to help balance environmental, operational, and cost considerations when choosing waste-management options for NADF drilling. Introduction Exploration and development drilling activities have expanded globally into such regions as the Caspian Sea, the UK Atlantic margin, offshore Brazil and West Africa, and the deep waters of the Gulf of Mexico as technology has improved the economics of finding and extracting oil and gas. New drilling concepts, including extended reach, horizontal and multi-lateral wells, enable development to proceed with fewer platforms allowing these resources to be developed more economically. These techniques also have an environmental benefit of reducing the zone of seafloor disturbance. New drilling concepts are technically challenging and require high-performance drilling fluids with capabilities exceeding those available from water based fluids (WBFs). As a result, non-aqueous drilling fluids (NADFs), for which the continuous phase is primarily a non-water soluble base fluid i.e. non-aqueous base fluid (NABF), have been used extensively by the petroleum industry. Access to a full range of drilling fluid technology is necessary to achieve drilling performance objectives and to support cost-effective development, especially in deep water or where horizontal or extended reach drilling is employed.

Thermomonospora curvata was cultivated on mineral salts medium containing glucose and cellobiose under conditions that increasingly favored the uptake of glucose. In each case cellobiose was utilized in preference to glucose and induced Il-glucosidase and endoglucanase activity. [14C]glucose metabolism studies indicated that cellobiose was not cleaved by extracellular I-glucosidase and transported as glucose. No evidence of cellobiose phosphorylase or a cellobiose-specific phosphoenolpyruvate-phosphotransferase system was observed.

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ChevronTexaco began investigating bioremediation as an option for treating Exploration and Production (E&P) wastes and remediation of site spills in 1992. In 1993, ChevronTexaco began full-scale landfarming operations of E&P wastes in Colorado. Since then ChevronTexaco has initiated numerous site-specific cleanups using bioremediation technologies such as composting and in-situ remediation, and we continue to operate bioremediation facilities for the treatment of ongoing E&P wastes that are generated as part of our normal operations. ChevronTexaco has successfully implemented bioremediation in diverse climates and in remote international locations. In this paper our top ten "lessons learned" in successfully applying bioremediation will be reviewed. These include predicting bioremediation end-points, the use of commercial microbial products, how to monitor treatment effectiveness, field equipment needed, interfacing with regulators, reusing treated wastes, costs by waste type and technology, and training of personnel. We will also discuss how to determine when bioremediation is a good option, when it is not a good option, and how to select the best biotechnology for a specific site. Introduction Biological treatment technologies are among the most practical and cost-effective methods for managing exploration and production (E&P) wastes such as tank bottoms, pit sludges, drilling muds, and oily soils from spill cleanups. Biological treatment methods depend on the ability of microorganisms to degrade oily waste into harmless products (carbon dioxide, water, and biomass) through biochemical reactions. The most common biological treatment technologies applied in the upstream petroleum industry include:composting (windrowing, forced aeration piles, and static/ passive aeration piles), andland treatment (landfarming, landspreading, and in-situ biotreatment). In biological treatment processes, microorganisms decompose hydrocarbons into water, carbon dioxide, and biomass. The bacteria and fungi responsible for biodegradation require oxygen, water, nutrients, and a source of carbon (such as the carbon in crude oils) to thrive. Biological treatment technologies commonly used in the upstream petroleum industry include composting and land-based treatment methods such as landfarming, landspreading, and in-situ biotreatment. In-vessel composting, bio-slurry systems, soil venting, and saturated zone bioremediation technologies are not commonly used due to high costs (typically >$100/ton) and/or their limited applicability to E&P wastes and site conditions. ChevronTexaco began investigating bioremediation as an option for treating E&P wastes and remediation of site spills in 1992, and has successfully implemented bioremediation technologies around the world. In this paper our top ten "lessons learned" in successfully applying bioremediation will be reviewed. Lesson #1 - Special "Bug" Products Are Not Needed There are many commercial microbial products (commonly referred to as "bugs") on the market for enhancing soil bioremediation. Published results by independent researchers indicate that these products do not enhance biodegradation rates or end-points for hydrocarbons or other organic compounds.1,2,3 The reason that "bug" products are not needed for soil bioremediation is that most soils contain a sufficient population of microorganisms to biodegrade amenable contaminants. For example, soils contain up to 10 million bacteria per gram, and a significant portion of this indigenous population is capable of degrading hydrocarbons.4 This indigenous population of hydrocarbon-degrading organisms will "bloom," or increase within 24–48 hours of exposure to hydrocarbons. Tilling, watering, pH maintenance, and adding nutrients to the soil will ensure that optimal conditions are maintained for the microbes. Figure 1 illustrates typical results in that the population of microorganisms increased from 10 million to 1 billion per gram per gram of soil 5 days after crude oil addition and establishment of optimal soil environmental conditions.

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