John A. Veil

A white paper describing produced water from production of crude oil, natural gas, and coal bed methane.

One of the key missions of the U.S. Department of Energy (DOE) is to ensure an abundant and affordable energy supply for the nation. As part of the process of producing oil and natural gas, operators also must manage large quantities of water that are found in the same underground formations. The quantity of this water, known as produced water, generated each year is so large that it represents a significant component in the cost of producing oil and gas. Produced water is water trapped in underground formations that is brought to the surface along with oil or gas. It is by far the largest volume byproduct or waste stream associated with oil and gas production. Management of produced water presents challenges and costs to operators. This white paper is intended to provide basic information on many aspects of produced water, including its constituents, how much of it is generated, how it is managed and regulated in different settings, and the cost of its management.

Produced water volumes and management practices in the United States.

Produced water volume generation and management in the United States are not well characterized at a national level. The U.S. Department of Energy (DOE) asked Argonne National Laboratory to compile data on produced water associated with oil and gas production to better understand the production volumes and management of this water. The purpose of this report is to improve understanding of produced water by providing detailed information on the volume of produced water generated in the United States and the ways in which produced water is disposed or reused. As the demand for fresh water resources increases, with no concomitant increase in surface or ground water supplies, alternate water sources, like produced water, may play an important role. Produced water is water from underground formations that is brought to the surface during oil or gas production. Because the water has been in contact with hydrocarbon-bearing formations, it contains some of the chemical characteristics of the formations and the hydrocarbons. It may include water from the reservoir, water previously injected into the formation, and any chemicals added during the production processes. The physical and chemical properties of produced water vary considerably depending on the geographic location of the field, the geologic formation, and the type of hydrocarbon product being produced. Produced water properties and volume also vary throughout the lifetime of a reservoir. Produced water is the largest volume by-product or waste stream associated with oil and gas exploration and production. Previous national produced water volume estimates are in the range of 15 to 20 billion barrels (bbl; 1 bbl = 42 U.S. gallons) generated each year in the United States (API 1988, 2000; Veil et al. 2004). However, the details on generation and management of produced water are not well understood on a national scale. Argonne National Laboratory developed detailed national-level information on the volume of produced water generated in the United States and the manner in which produced water is managed. This report presents an overview of produced water, summarizes the study, and presents results from the study at both the national level and the state level. Chapter 2 presents background information on produced water, describing its chemical and physical characteristics, where it is produced, and the potential impacts of produced water to the environment and to oil and gas operations. A review of relevant literature is also included. Chapter 3 describes the methods used to collect information, including outreach efforts to state oil and gas agencies and related federal programs. Because of the inconsistency in the level of detail provided by various state agencies, the approaches and assumptions used to extrapolate data values are also discussed. In Chapter 4, the data are presented, and national trends and observations are discussed. Chapter 5 presents detailed results for each state, while Chapter 6 presents results from federal sources for oil and gas production (i.e., offshore, onshore, and tribal lands). Chapter 7 summarizes the study and presents conclusions.

Decision and risk analysis study of the injection of desalination by-products into oil- and gas-producing zones.

When reverse osmosis (RO) is used to desalinate brackish water feed streams, a small but significant amount of the brine is discharged as a “reject” stream from the RO unit. This brine contains concentrated dissolved salts and other materials. Disposing of this brine concentrate for traditional RO processes can represent a significant fraction of the cost of operating the unit to recover fresh water. Coincidently, in the oil and gas industry, high salinity brines are routinely injected into formations for pressure maintenance and secondary recovery by water flooding. If water from desalination operations could be injected into these oil- and gas-containing formations, the estimated cost savings could be as much as 30% of the cost of operating the desalination unit. This represents a significant cost savings for RO technology that would make fresh water available to communities in need of this valuable resource. To provide a comprehensive assessment of the perceived benefits compared to the possible hazards of this practice, we use risk analysis theory to define this process in more detail. The potential for formation damage, reduced injectivity, produced water scaling, and environmental impact is evaluated through comparison with traditional waterflood compatibility studies. We also provide an analysis of how state and federal Underground Injection Control (UIC) rules may be used to regulate injection of RO reject brines. The risk analysis study goes beyond classical decision analysis theory to address the “triple bottom line” economic, environmental, and societal benefits afforded by the process and provides a roadmap to gather quantifiable information for regulators, businesses, and community leaders who might consider this technology.

Options, Methods, and Costs for Offsite Commercial Disposal of Exploration and Production Wastes

In the United States, most exploration and production (E&P) wastes generated at onshore oil and gas wells--contaminated soils, naturally occurring radioactive material (NORM), oil-based muds and cuttings, produced water, tank bottoms, and water-based muds and cuttings--are disposed of or otherwise managed at the well site. Some of these E&P wastes, however, are not suitable for onsite management, and some well locations in sensitive environments cannot be used for onsite management. In these situations, operators must find offsite waste-disposal solutions. Responding to this need, offsite commercial disposal facilities are businesses that charge a fee for accepting and managing E&P wastes generated by others. Funded by the U.S. Department of Energy (USDOE), the authors of this paper assembled a unique set of data covering options, methods, and costs for offsite disposal of E&P wastes in the United States (Puder and Veil 2006a). Data were collected for more than 200 disposal facilities. This paper describes the project and the findings, which were published in September 2006.

Regulatory Issues Affecting Management of Produced Water from Coal Bed Methane Wells

This paper describes the existing national discharge regulations, the ways in which CBM produced water is currently being managed, the current CBM discharge permitting practices, and how these options might change as the volume of produced water increases because of the many new wells being developed.

A Holistic Look at Minimizing Adverse Environmental Impact Under Section 316(b) of the Clean Water Act

Section 316(b) of the Clean Water Act (CWA) requires that “the location, design, construction, and capacity of cooling water intake structures reflect the best technology available for minimizing adverse environmental impact.” As the U.S. Environmental Protection Agency (EPA) develops new regulations to implement Section 316(b), much of the debate has centered on adverse impingement and entrainment impacts of cooling-water intake structures. Depending on the specific location and intake layout, once-through cooling systems withdrawing many millions of gallons of water per day can, to a varying degree, harm fish and other aquatic organisms in the water bodies from which the cooling water is withdrawn. Therefore, opponents of once-through cooling systems have encouraged the EPA to require wet or dry cooling tower systems as the best technology available (BTA), without considering site-specific conditions. However, within the context of the broader scope of the CWA mandate, this focus seems too narrow. Therefore, this article examines the phrase “minimizing adverse environmental impact” in a holistic light. Emphasis is placed on the analysis of the terms “environmental” and “minimizing.” Congress chose “environmental” in lieu of other more narrowly focused terms like “impingement and entrainment,” “water quality,” or “aquatic life.” In this light, BTA for cooling-water intake structures must minimize the entire suite of environmental impacts, as opposed to just those associated with impingement and entrainment. Wet and dry cooling tower systems work well to minimize entrainment and impingement, but they introduce other equally important impacts because they impose an energy penalty on the power output of the generating unit. The energy penalty results from a reduction in plant operating efficiency and an increase in internal power consumption. As a consequence of the energy penalty, power companies must generate additional electricity to achieve the same net output. This added production leads to additional environmental impacts associated with extraction and processing of the fuel, air emissions from burning the fuel, and additional evaporation of freshwater supplies during the cooling process. Wet towers also require the use of toxic biocides that are subsequently discharged or disposed. The other term under consideration, “minimizing,” does not equal “eliminating.” Technologies may be available to minimize but not totally eliminate adverse environmental impacts.

The potential for effluent trading in the energy industries.

In January 1996, the US Environmental Protection Agency (EPA) released a policy statement endorsing wastewater effluent trading in watersheds, hoping to promote additional interest in the subject. The policy describes five types of effluent trades: point source/point source, point source/nonpoint source, pretreatment, intraplant and nonpoint source/nonpoint source. This paper evaluates the feasibility of implementing these types of effluent trading for facilities in the oil and gas, electric power and coal industries. This paper finds that the potential for effluent trading in these industries is limited because trades would generally need to involve toxic pollutants, which can only be traded under a narrow range of circumstances. However, good potential exists for other types of water-related trades that do not directly involve effluents (e.g. wetlands mitigation banking and voluntary environmental projects). The potential for effluent trading in the energy industries and in other sectors would be enhanced if Congress amended the Clean Water Act (CWA) to formally authorize such trading.

Cooling water use patterns at US nonutility electric generating facilities

Abstract Cooling water is used by many industrial facilities. The largest user of cooling water is the electric power industry, although other significant users include the pulp and paper, chemical, iron and steel, aluminum, and petroleum refining industries. The US Environmental Protection Agency (EPA) is currently developing regulations to implement section 316(b) of the Clean Water Act, which deals with cooling water intake structures. The EPA will examine cooling water use patterns at various industries. Data pertaining to cooling water use patterns at utility plants are readily available; however, no information has been assembled for cooling water use at electric power generating facilities owned or operated by entities other than utilities (nonutilities). This paper presents data concerning cooling water use from two subsets of the nonutility sector and focuses on plants using once-through cooling systems. The first subset includes 123 nonutility plants that each generate at least 150 MW of power. Collectively, they represent 41,494 MW of generating capacity, or about 56% of the total nonutility generating capacity. Approximately 17% of the installations within that subset utilize once-through cooling water. The second subset includes 58 waste-to-energy facilities, which individually produce less than 80 MW but collectively generate about 2200 MW. Only 11% of this subset of plants uses once-through cooling water. The total 15,372 MW generated by once-through nonutilities is equivalent to only 6% of the 258,906 MW generated by utilities utilizing once-through cooling. From a national perspective this share may appear relatively insignificant. However, in some states, the nonutility once-through total is equivalent to a more significant percentage of the utility once-through total.

Disposal of NORM waste in salt caverns

Some types of oil and gas production and processing wastes contain naturally occurring radioactive materials (NORM). If NORM is present at concentrations above regulatory levels in oil field waste, the waste requires special disposal practices. The existing disposal options for wastes containing NORM are limited and costly. This paper evaluates the legality, technical feasibility, economics, and human health risk of disposing of NORM-contaminated oil field wastes in salt caverns. Cavern disposal of NORM waste is technically feasible and poses a very low human health risk. From a legal perspective, there are no fatal flaws that would prevent a state regulatory agency from approving cavern disposal of NORM. On the basis of the costs charged by caverns currently used for disposal of nonhazardous oil field waste (NOW), NORM waste disposal caverns could be cost competitive with existing NORM waste disposal methods when regulatory agencies approve the practice.

Predicted Impacts from Offshore Produced Water Discharges on Hypoxia in the Gulf of Mexico

Summer hypoxia (dissolved oxygen<2 mg/L) in the bottom waters of the northern Gulf of Mexico has received considerable scientific and policy attention because of potential ecological and economic impacts. This hypoxic zone forms off the Louisiana coast each summer and has increased from an average of 8,300 km in 1985–1992 to over 16,000 km in 1993–2001, reaching a record 22,000 km in 2002. The almost threefold increase in nitrogen load from the Mississippi River Basin (MRB) to the Gulf since the middle of the last century is the primary external driver for hypoxia. A goal of the 2001 Federal Action Plan is to reduce the 5-year running average size of the hypoxic zone to below 5,000 km by 2015. After the Action Plan was developed, a new question arose as to whether sources other than the MRB may also contribute significant quantities of oxygen-demanding substances. One very visible potential source is the hundreds of offshore oil and gas platforms located within or near the hypoxic zone, many of which discharge varying volumes of produced water. The objectives of this study were to assess the incremental impacts of produced water discharges on dissolved oxygen in the northern Gulf of Mexico, and to evaluate the significance of these discharges relative to loadings from the MRB. Predictive simulations were conducted with three existing models of Gulf hypoxia using produced water loads from an industry study. Scenarios were designed that addressed loading uncertainties, settleability of suspended constituents, and different assumptions on delivery locations for the produced water loads. Model results correspond to the incremental impacts of produced water loads, relative to the original model results, which included only loads from the MRB. The predicted incremental impacts of produced water loads on dissolved oxygen in the northern Gulf of Mexico from all three models were small. Even considering the predicted ranges between lowerand upper-bound results, these impacts are likely to be within the errors of measurement for bottomwater dissolved oxygen and hypoxic area at the spatial scale of the entire hypoxic zone.