Drilling Waste Management: Past, Present, and Future

Abstract

Abstract The process of drilling oil and gas wells generates large volumes of drill cuttings and spent muds. The American Petroleum Institute estimates that in 1995, about 150 million barrels of drilling waste was generated from onshore wells in the United States alone. Onshore and offshore operators have employed a variety of methods for managing these drilling wastes, depending on what state and federal regulations allow and how costly those options are for the wells in question. In the offshore, the options are limited to discharge, underground injection, and transport back to shore for disposal. Onshore operators have a wider range of options— some wastes are managed onsite while others are removed to offsite commercial disposal facilities. The onshore waste management options employed include landspreading and landfarming, evaporation and burial onsite, underground injection, incineration and other thermal treatment, bioremediation and composting, and reuse and recycling. Some drilling waste management practices used in the past did not protect the environment and public health to the extent desired and were later prohibited by regulatory agencies. This paper reviews some of those past waste management practices and indicates how wastes are currently being managed. Over time, state and federal regulatory requirements will become stricter, drilling and mud system technologies will advance, and some companies may voluntarily adopt waste management options that have even less environmental impacts that those in use today. The paper also discusses some possible drilling waste management practices that are likely to be employed in the upcoming decade. Introduction The well-drilling process generates two types of wastes — used drilling fluids and drill cuttings. Drilling fluids (or muds) are used to aid the drilling process. Muds are circulated through the drill bit to lubricate the bit and to aid in carrying the ground-up rock particles (drill cuttings) to the surface, where the muds and cuttings are separated by mechanical means. Most onshore wells are drilled with water-based or oil-based muds, while offshore wells may also use synthetic-based muds. The American Petroleum Institute (API)1 estimates that about 150 million barrels (bbl) of drilling waste was generated at U.S. onshore wells in 1995. Purpose Oil and gas wells have been drilled for over a century. In the early years of the industry, little attention was usually given to suitable management of drilling wastes. The purpose of this paper is to review the past waste management practices and indicate how wastes are currently being managed. Over time, state and federal regulatory requirements will become stricter, drilling and mud system technologies will advance, and some companies may voluntarily adopt waste management options that have even less environmental impacts that those in use today. The paper also discusses some possible management practices for drilling wastes that are likely to be employed in the upcoming decade. The U.S. Department of Energy (DOE) is responsible for ensuring an adequate and affordable supply of energy for the nation. One of DOE's goals is to identify and support new technologies that help oil and gas at lower cost and with less environmental impact. The author has evaluated many waste management technologies and strategies for DOE throughout the past decade. Some of these are included in the following discussion.