1. Environmental Impacts of Oil and Gas Exploration and Production: Ground Water Impacts at OSPER Sites, Osage County, Oklahoma *Yousif K. Kharaka, James J. Thordsen, Evangelos Kakouros, and Gil Ambats U. S. Geological Survey, Menlo Park, California, USA GSA Annual Meeting October, 2005 Financial support from DOE-NETL Drilling support from EPA-NRMRL Osage Nation Tribal Authorities U.S. Army Corps of Engineers

2. Distribution of Petroleum wells in Oklahoma, Osage County, & the study Area

3. Topics Discussed 1- OSPER “A” site, Osage County, OK. 2- Chemical & isotopic compositions of source & ground waters at OSPER “A” site. 3- Delineating the plume boundaries at “A”. 4- Processes--Mixing (brine, prec. & GW), ET & water-rock-bacterial interactions. 5- Future plans & concluding remarks.

4. OSPER “A” Site Oil production (100,000 bbl) from shallow. Pennsylvanian sandstones started in 1912, mostly completed by 1937. No site activity for 65-70 years. No waterflooding at this site All the produced water (~1million bbl) released to ground surface; petroleum initially collected at oil pit. Deep erosion of northern part of the site

5. Geology Map Upper area (south) gentle slope tree kills from early(?) salt releases revegetated with grasses Asphaltic pits highly weathered oil one pit contains relatively fresh tank sludge(?) Lower area (north) steeper slope prominent salt scar (~2 m deep) salt (& gypsum) at surface

6. Photo by Ken Jewell, USEPA (Jan. 2004)

8. Sampling Trips to the Sites March 2001--- Source fluids from oil wells, GW, and Skiatook Reservoir. Surface pools at both sites. February 2002 --- ~60 Geoprobe, auger and rotary wells drilled, cored, completed and sampled at and two sites. June 2002 --- Water level, conductance, and T measurements, followed by collection of ~40 water and a few oil samples. November 02 --- Drilling with geoprobe and sampling. March-April 03 ---Drilling (EPA auger) and sampling. January 2004 --- (9) deep wells (WRD air) at “A”, and sampling. May 2004 --- (4) deep (EPA auger) wells at “B”; sampling. February 2005 --- Water levels and sampling at both sites. September 2005 --- Weir discharges.

10. “A” site Stiff Diagrams

11. New wells (1/04) Traverse a-a’

12. Site A - a-a’ traverse (with tritium)[update 10/12/05] 4.2 1.7 0.3 1.4 6.9 0.1 1.2 1.0 9.9 4.2 Tritium (in T.U.)

13. 200 205 210 215 220 225 230 0255075100125150175200225 Distance along traverse, in meters Altitude, in meters above sea level AE07 South AA06 AE51 AA01 AA02 AE06 AA10AE55 North Skiatook Lake DRY brine pits salt scar erosion low: 215.8 m (2/2003) Skiatook Lake levels high: 219.1 m (3/2004) AE13 AA61 AA04 ~5 ~20 39 730 920 23 12,300 420 15,300 470 2,960 4.5 207 520 6,060 150 9,840 504 18,400 365 10,000 6,230 96 6,500 180 18,300 375 ?? 3,350 19 a-a’ traverse 15,000 10,000 5,000 2,500 chloride (mg/L) sulfate (mg/L)

15. W-E traverse

17. Mineral-Water Interactions for S at OSPERs

18. Summary and Conclusions At OSPER ‘A’ site: 1)GW plume (3,000-30,000 mg/l TDS) extends beyond the salt scarred area & intersects Skiatook Lake; 3-D limits?? 2)The extent of inorganic and organic GW plumes are different. 3)Salt & organics from produced water releases still remain in soils and GW after 65+ years of natural attenuation. Future Plans Natural attenuation; solute transport (overland &GW); remediation. *** Environmental Geosciences, 2005, v. 12, No. 2 ***