Potential Pathways between Oil & Gas Activities and Protected Groundwater
Oil and gas collect in zones that generally have little connection to the surface. Development of these resources requires drilling through confining formations, pumping fluids up to the surface, separating the useable petroleum out of the fluid, and disposing of wastes. As a result, pathways may have been created that could allow fluids to move from the zone of oil and gas development activities into the zone of protected groundwater. This section describes each potential pathway for fluid movement and the relative importance of different factors.
Because chemical constituents are affected by the pathways they travel, we can use geochemical tools to determine where fluid in a groundwater sample came from and to what extent that groundwater has been affected by one or more oil and gas development activities. The same tools can distinguish between oil and gas moving through natural and unnatural pathways.
Research outside of California has shown that oil and gas-related constituents found in groundwater are often the result of movement along leaky wellbores (Jackson and others, 2013; Davies and others, 2014; Darrah and others, 2014). Current DOGGR regulations spell out well construction standards intended to keep water and oil-bearing zones separate (California Department of Conservation, 2011) and include periodic testing of well integrity. However, some wells were drilled before those standards were put in place.
Vertical oil wells are by far the most common type of well bore in California and many of the largest fields have very dense well networks. Of the 168 currently active oil fields greater than 2 square miles (mi²) in size, 31 contain more than 100 known wellbores per square mile (California Department of Oil, Gas, and Geothermal Resources, 2015). Even a small percentage of compromised wellbores could correspond to a large number of transport pathways.
Land deformation can also cause wells to fail. Oil field operations, including withdrawal of petroleum, water and steam flooding, and waste disposal using injection wells, all potentially cause land deformation (Blom and others, 2005; Bawden and others, 2003; Poland and Davis, 1969). Earthquakes and depletion of groundwater reservoirs can also cause land deformation.
Groundwater‐quality monitoring related to sump disposal is managed by the State Water Resources Control Board and Regional Boards and is not part of the COGG Program. However, water samples from sumps are needed for end-member geochemical interpretive analyses.
Oil production in California currently relies on the cycling of large volumes of water and steam through oil-bearing zones by subsurface injection. The figure below shows the statewide aggregated water volumes (in TAF) injected as water or steam to enhance oil recovery and as waste disposal in comparison to the volume of produced waters reported each year by DOGGR's annual production/injection databases and reports between 1968 and 2013. Injections for enhanced recovery include water‐flooding, steam‐flooding, cyclic steaming, and pressure maintenance. Well stimulation is a distinct recovery method that involves fracturing the rock matrix in order to enhance the flow of oil or natural gas. The total volume injected for this method is estimated at less than 1 TAF per year (California Council on Science and Technology, 2014).
These enhanced recovery and water injection activities are not designed to create new fractures or force fluids towards protected groundwater, but it could be hypothesized that the increased pore pressure they cause may encourage fractures when improperly located or operated (Saripalli and others, 2000; Bryant and others, 2003; Suarez-Rivera and others, 2002; Gadde and Sharma, 2001). Minner and others (2002) conducted a detailed study of this phenomenon in the Lost Hills area for the purposes of refining hydraulic fracturing operations, noting that “water injection and reservoir fluid production result in poroelastic stress changes that can dramatically alter the created fracture geometry on infill wells".
Federal Underground Injection Control regulations require operators to monitor hydrostatic pressure in injection wells to prevent pressure build up and to keep the injected fluid within the permitted zone (Environmental Protection Agency, 2001). The locations where water and steam flooding are taking place in dense well networks are tightly controlled by oil and gas developers and are in dense well networks. Water disposal wells are typically oil wells that have been converted to this purpose.
Natural pathways for groundwater contamination also exist. Oil, gas, and associated formation water may migrate to the surface along faults and fractures; factors which control and enhance this flow are complex. Eichhubl and Boles (2000), for example, describe processes controlling fluid flow along faults in the Monterey formation.
The geology of a basin may constrain or increase the mobility of hydrocarbons and/or formation water from oil and gas deposits to shallower groundwater aquifers. In basins with impermeable “cap” formations, the deeper oil and gas deposits are effectively isolated from shallower aquifers. However, in basins with relatively porous overlying strata, hydrocarbons and formation water may migrate from deep deposits to shallower aquifers. Similarly, the character and density of faults within a basin may greatly impact the mobility of deeper hydrocarbons and formation water by acting as conduits by which these materials can be transported through cap formations into shallower aquifers.
Poland, J.F., and Davis, G.H., 1969, Land subsidence due to withdrawal of fluids: Reviews in Engineering Geology, v. 2, p. 187-270.
Bean, R.T., and Logan, J., 1983, Lower Westside water quality investigation, Kern County: California State Water Resources Control Board [variously paged].
Hainey, B.W., Keck, R.G., Smith, M.B., Lynch, K.W., and Barth, J.W., 1997, On-site fracturing disposal of oilfield waste solids in Wilmington Field, Long Beach Unit, CA: Society of Petroleum Engineers Western Regional Meeting, June 25-27, 1997, Long Beach, Calif., Proceedings, 8 p., DOI: 10.2118/38255-MS
Sipple-Srinivasan, M.M., Bruno, M.S., Hejl, K.A., Danyluk, P.G., and Olmstead, S.E., 1998, Disposal of crude contamination soil through slurry fracture injection at the West Coyote field in California: Society of Petroleum Engineers Western Regional Meeting, May 10-13, 1998, Bakersfield, California, Proceedings, 8 p., DOI: 10.2118/46239-MS
Eichhubl, P., and Boles, J.R., 2000, Focused fluid flow along faults in the Monterey Formation, coastal California: Geological Society of America Bulletin , v.112, p. 1667-1679.
Saripalli, K.P., Sharma, M.M., Bryant, S.L., Modeling injection well performance during deep-well injection of liquid wastes: Journal of Hydrology, v. 227, p. 41-55, DOI: 10.1016/S0022-1694(99)00164-X
Environmental Protection Agency, 2001, Technical Program Overview: Underground Injection Control Regulations: Environmental Protection Agency, Office of Water, EPA 816-R-02-025, 87 p. (Revised July 2001).
Gadde, P.B., and Sharma, M.M., 2001, Growing injection well fractures and their impact on waterflood performance: Society of Petroleum Engineers Annual Technical Conference and Exhibition, October 3, 2001, New Orleans, Louisiana, Proceedings, 12 p., DOI: 10.2118/71614-MS
Minner, W.A., Wright, C.A., Stanley, G.R., de Pater, C.J., Gorham, T.L., Eckerfield, L.D., and Hejl, K.A., 2002, Waterflood and production-induced stress changes dramatically affect hydraulic fracture behavior in Lost Hills infill wells: Society of Petroleum Engineers Annual Technical Conference and Exhibition, September 29-October 2, 2002, San Antonio, Texas, Proceedings, 13 p., DOI: 10.2118/77536-MS
Suarez-Rivera, R., Stenebraten, J., Gadde, P.B., and Sharma, M.M., 2002, An experimental investigation of fracture propagation during water injection: International Symposium and Exhibition on Formation Damage Control, February 20-21, 2002, Lafayette, Louisiana, Proceedings, 11 p., DOI: 10.2118/73740-MS
Bawden, G.W., Sneed, M., Stork, S.V., and Galloway, D.L., 2003, Measuring human-induced land subsidence from space: U.S. Geological Survey Fact Sheet 069-03, 4 p.
Bryant, S.L., Paruchuri, R.K., and Saripalli, K.P., 2003, Flow and solute transport around injection wells through a single, growing fracture: Advances in Water Resources, v. 26, no. 8, p. 803-813, DOI: 10.1016/S0309-1708(03)00065-4
Blom, R.G., Fielding, E.J., Brink, J.L., Patzek, T.W., and Silin, D.B., 2005, Monitoring subsidence at the Lost Hills Diatomite Oil Field, California, with SAR Interferometry and Other Remote Sensing Technologies: NASA Solid Earth & Natural Hazards 2005 Program Review, May 3-5, 2005, Sioux Falls, S.Dak., Proceedings, 40 p.
Division of Oil, Gas, and Geothermal Resources, 1968-2008, Annual reports of the State Oil and Gas Supervisor: California Department of Conservation, accessed March 7, 2017 at https://www.conservation.ca.gov/dog/pubs_stats/annual_reports/Pages/annual_reports.aspx.
California Code of Regulations, 2011, Development, Regulation, and Conservation of Oil and Gas Resources [Title 14, Div. 2, Chap. 4]: Publication No. PRC04.
Jackson, R.E., Gorody, A.W., Mayer, B., Roy, J.W., Ryan, M.C., and Van Stempvoort, D.R., 2013, Groundwater protection and unconventional gas extraction; the critical need for field-based hydrogeological research: Ground Water, v. 51, p. 488-510, DOI: 10.1111/gwat.12074
Beeson, D., Hoffman, K., Larue, D., McNaboe, J., and Singer, J,, 2014, Creation and utility of a large fit-for-purpose earth model in a giant nature field-— Kern River field, California: American Association of Petroleum Engineers Bulletin, v. 98, no. 7, p. 1305-1324, DOI: 10.1306/02051413090
California Council on Science and Technology, 2014, Advanced well stimulation technologies in California; An independent review of scientific and technical information: Sacramento, California Council on Science and Technology, 394 p.
Darrah, T.H., Vengosh, A., Jackson, R.B., Warner, N. R., and Poreda, R.J., 2014, Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales: Proceedings of the National Academy of Science, v. 111, no. 39, p. 14076-14081, DOI: 10.1073/pnas.1322107111
Davies, R.J., Almond, S., Ward, R.S., Jackson, R.B., Adams, C., Worrall, F., Herringshaw, L.G., Gluyas, J.G., and Whitehead, M.A., 2014, Oil and gas wells and their integrity; implications for shale and unconventional resource exploitation: Marine and Petroleum Geology, v. 56, p. 239-254, DOI: 10.1016/j.marpetgeo.2014.03.001
Division of Oil, Gas, and Geothermal Resources, 2015, DOGGR Well Finder: Digital spatial data for oil wells in California; California Department of Conservation, accessed February 28, 2015 at: https://maps.conservation.ca.gov/doggr/wellfinder/#/-118.94276/37.12009/6
Holcomb, R.E., 2015, Oil field produced water pond status report #6: Central Valley Regional Water Quality Control Board status report no. 6, 4 p. memorandum of November 16, 2015, accessed at https://www.waterboards.ca.gov/centralvalley/water_issues/oil_fields/information/disposal_ponds/pond_status_rpt6_2015_1116.pdf.
Shimabukuro, D.H. and Horner, T., 2015, Wastewater disposal and waterflood injection volumes in California: in Geological Society of America 2015 Annual Meeting, Baltimore, Maryland, November 1-4, 2015: Geological Society of America, unpaginated.
Shimabukuro, D.H., Haugen, E.A., Battistella, C., Treguboff, E.W., and Kale, J.M., 2015, Using oil and gas well log records to understand possible connections between wastewater injection zones and usable groundwater aquifers in California, in American Geophysical Union Fall 2015 Meeting, San Francisco, Calif., December 14-18, 2015: American Geophysical Union, unpaginated.
Crandall-Bear, A. and Shimabukuro, D.H., 2016, A visual history of oil field development and wastewater injection in California oil fields, in Cordilleran Section 112th Annual Meeting, Ontario, Canada, April 4-6, 2016: Geological Society of America, v. 48, n. 4, DOI: 10.1130/abs/2016CD-274739
Davis, Tracy A., Landon, Matthew K., and Bennett, George L. V, 2018, Prioritization of oil and gas fields for regional groundwater monitoring based on a preliminary assessment of petroleum resource development and proximity to California’s groundwater resources, U.S. Geological Survey, Scientific Investigations Report, SIR 2018-5065, DOI: 10.3133/sir20185065