Abstract

The U.S. Geological Survey is conducting research on the impacts of produced waters on petroleum resource development and the environment. Ongoing multidisciplinary investigations are focused on the 1) quantity and quality of current water production, 2) geologic and geochemical parameters that influence the viability of injection wells, and 3) processes that affect the dispersion of inorganic and organic constituents of produced water that are released into the surface and near-surface environment.

Introduction

One of the responsibilities of the U.S. Geological Survey is to evaluate petroleum resources of the United States. To refine our assessment methods, USGS personnel are conducting research to understand the impact of produced water on development of oil and gas resources and the environment. Handling and disposal of produced water as well as assessing and remediating sites contaminated by produced waters can be major costs to a producer. Disposal costs can exceed $1.00 per barrel in some areas. Considering typical production of ten barrels of water for each barrel of oil, costs of water disposal may prohibit continued production and lead to abandonment of development plans. Identification of resources whose development is sensitive to issues related to produced water will lead to more detailed assessments and highlight needs for development of technology that will reduce water handling costs while complying with environmental requirements. The ultimate goals of the Energy Team research on produced water are to 1) develop estimates of the quantity and quality of water that will be produced with future petroleum resource development, 2) investigate current disposal practices especially parameters related to injection wells, and 3) describe processes that control dispersion of environmental contaminants related to produced waters.

The following text outlines some of the produced water research activities of the U.S. Geological Survey. The scope of the activities is intentionally broad because of the diversity of issues relevant to produced waters. Results of these studies are intended for application to resource assessment, resource development, land-use planning, site assessments, and environmental remediation.

Studies of Produced Water Quality and Quantity

Preliminary efforts to describe the quantity of water produced with oil and gas have paralleled the play analysis approach used in the 1995 USGS National Assessment of Oil and Gas Resources. Available production records that include water volume data are compiled based on reservoir rock and geologic setting. Although production records are considered less reliable for water volume data than for petroleum data, general tendencies in the amount of water produced among reservoirs can be defined. The summary for selected producing intervals in the San Juan basin is offered as an illustration of this approach (Table 1). The water to petroleum production ratio is available for each producing interval and within each interval in the basin. Variations in the volume of water produced across the basin or within a play from each reservoir or accumulation (set of reservoirs) are evaluated and will be interpreted in the context of the local geology and hydrology as part of future USGS efforts.

Coal-bed methane is becoming an important source of natural gas, but the quantity of produced water typically associated with this resource can limit development of some plays. Produced water volumes from coal-bed methane wells are typically 10 to 100 times higher than most natural gas producing wells. Potential producing intervals in northeast Wyoming and northwest Colorado cannot be developed because the ground water recharge rate is greater than can be accommodated by standard development pumps. P. 131^

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