Characterizing Groundwater Contamination by Petroleum Operations

Authors: Jonathan Fisher, Oklahoma State University, Stillwater, OK.

Venue: Oklahoma Clean Lakes and Watersheds Association’s 16th Annual Conference in Tahlequah, OK, April 11-13, 2007 (http://www.oclwa.org/ [external site]).

Abstract: Produced water, which often has elevated levels of dissolved salts and soluble hydrocarbons, is a byproduct of petroleum production. This study investigated the extent and potential for effects of produced water contamination from occasional surface seepage and possible subsurface flow into an unconfined aquifer along the shore of Skiatook Lake in northeastern Oklahoma. We monitored the chemistry and toxicity of the produced-water source and selected groundwater wells. Produced-water toxicity monitoring employed three cladoceran species (Daphnia pulex, D. magna, and Ceriodaphnia dubia) and one fish, the fathead minnow (Pimephales promelas), while groundwater monitoring used only D. pulex. The chemical constituents of the produced water and receiving groundwater varied little over time. Both the produced water and groundwater were toxic to the test organisms. Cladoceran produced water 48-h median lethal concentrations (LC50) ranged between 1% and 5%. Fathead minnow LC50s were between 7% and 11% for acute (48-h) survival endpoints and median effects concentrations of 2% to 6% for growth effects. D. pulex bioassays on groundwater samples resulted in 48-h LC50s ranging from 3.9% near a produced-water injection well to greater than 100% elsewhere at the impact site. We also used geographic information systems to explore gradients in chemical composition and predicted effects on test organisms by contaminated groundwater.

Related NETL Project: The primary goal of the related NETL project DE-FC26-04NT15544 entitled “Field Validation of Toxicity Tests to Evaluate the Potential for Beneficial Use of Produced Water” is to determine how well laboratory toxicity tests of produced-water samples indicate the potential for environmental impacts. The project is being conducted at a field site at Lake Skiatook, OK, where produced water is leaking from an evaporation pit on the shoreline of the lake.

NETL Project Contacts
NETL - Jesse Garcia (jesse.garcia@netl.doe.gov or 918-699-2036)
OSU - Joseph Bidwell (bidwelj@okstate.edu or 405-744-6941)