Impacts of Oil and Gas Production on Contaminant Levels in Sediments

Abstract

Recent technological progresses have unlocked tremendous shale energy resources, leading to increased production of oil and gas and a variety of new environmental pollution issues in the United States. One such example is management of produced waters, which are often disposed of via deep well injection. Produced water injection has been linked to induced seismicity. Thus, there are strong incentives for alternative management strategies that come with new, uncertain environmental risks. This paper summarizes studies of sediment pollution due to oil and gas production. The goal is to highlight potential environmental risks associated with produced water management, including long-term contamination of sediments. Sediment contaminants from produced waters include organic and inorganic toxic compounds. Three different indicators have been developed for sediment pollution: the geoaccumulation index, pollution load index, and the enrichment factor. The main pollutants in sediments resulting from oil and gas production are heavy metals, salts, naturally occurring radioactive materials (NORMs), oil and grease (O&G), benzene, toluene, ethylbenzene and xylene (BTEX), total petroleum hydrocarbon (TPH), and polycyclic aromatic hydrocarbon (PAHs). These pollutants reach sediments and water resources via pipeline leaks, truck spills, improper waste disposal, and underground injection. Methods to decrease contaminant risks in sediments include surface capping, bioremediation, and phytoremediation. The shale oil and gas boom has exacerbated produced water management issues. As states consider regulation of treated produced waters, there is a strong need to consider potential contaminants of concern. Several case studies from the U.S., Middle East, Africa, Asia, and South America were used to assess levels of contamination around the world’s sediments in regions with high levels of oil and gas activity. Appropriate management of residual pollution from oil and gas operations should consider the nature of contaminants and sediments, the routes of contamination, the levels of contamination, the effect of contaminants on the sites, and methods for contaminant cleanup.