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Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA

Publication ,  Journal Article
McMahon, PB; Kulongoski, JT; Vengosh, A; Cozzarelli, IM; Landon, MK; Kharaka, YK; Gillespie, JM; Davis, TA
Published in: Applied Geochemistry
November 1, 2018

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gas fields are commonly used to examine the source of the formation water and possible impacts on groundwater in areas of oil and gas development. Understanding the geochemical variability of oil-field water could help to evaluate its origin and delineate possible contamination of shallow aquifers in cases where oil-field water is released to the environment. Here we report geochemical and multiple isotope (H, C, O, Sr, Ra) data from 22 oil wells, three sources of produced water that are disposed of in injection wells, and two surface disposal ponds in four oil fields in the southern San Joaquin Valley, California (Fruitvale, Lost Hills, North and South Belridge). Correlations between Cl and δ18O, as well as other ions, and gradual increases in salinity with depth, indicate dilution of one or more saline end-members by meteoric water. The saline end-members, represented by deep samples (610 m–2621 m) in three oil-bearing zones, are characterized by Na–Cl composition, near-seawater Cl concentrations (median 20,000 mg/L), enriched δ18O–H2O (median 3.4‰), high ammonium (up to 460 mg-N/L), and relatively high radium activity (226Ra+228Ra = 12.3 Bq/L). The deepest sample has low Na/Cl (0.74), high Ca/Mg (5.0), and low 87Sr/86Sr (0.7063), whereas the shallower samples have higher Na/Cl (0.86–1.2), Ca/Mg near 1, and higher 87Sr/86Sr (∼0.7083). The data are consistent with an original seawater source being modified by various depth and lithology dependent diagenetic processes. Dilution by meteoric water occurs naturally on the east side of the valley, and in association with water-injection activities on the west side. Meteoric-water flushing, particularly on the east side, results in lower solute concentrations (minimum total dissolved solids 2730 mg/L) and total radium (minimum 0.27 Bq/L) in oil-field water, and promotes biodegradation of dissolved organic carbon and hydrocarbon gases like propane. Acetate concentrations and δ13C of dissolved inorganic carbon indicate biogenic methane production occurs in some shallow oil zones. Natural and human processes produce substantial variability in the geochemistry of oil-field water that should be considered when evaluating mixing between oil-field waters and groundwater. The variability could result in uncertainty as to detecting the potential source and impact of oil-field water on groundwater.

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Published In

Applied Geochemistry

DOI

EISSN

1872-9134

ISSN

0883-2927

Publication Date

November 1, 2018

Volume

98

Start / End Page

127 / 140

Related Subject Headings

  • Geochemistry & Geophysics
  • 3703 Geochemistry
  • 0502 Environmental Science and Management
  • 0402 Geochemistry
 

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McMahon, P. B., Kulongoski, J. T., Vengosh, A., Cozzarelli, I. M., Landon, M. K., Kharaka, Y. K., … Davis, T. A. (2018). Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA. Applied Geochemistry, 98, 127–140. https://doi.org/10.1016/j.apgeochem.2018.09.015
McMahon, P. B., J. T. Kulongoski, A. Vengosh, I. M. Cozzarelli, M. K. Landon, Y. K. Kharaka, J. M. Gillespie, and T. A. Davis. “Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA.” Applied Geochemistry 98 (November 1, 2018): 127–40. https://doi.org/10.1016/j.apgeochem.2018.09.015.
McMahon PB, Kulongoski JT, Vengosh A, Cozzarelli IM, Landon MK, Kharaka YK, et al. Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA. Applied Geochemistry. 2018 Nov 1;98:127–40.
McMahon, P. B., et al. “Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA.” Applied Geochemistry, vol. 98, Nov. 2018, pp. 127–40. Scopus, doi:10.1016/j.apgeochem.2018.09.015.
McMahon PB, Kulongoski JT, Vengosh A, Cozzarelli IM, Landon MK, Kharaka YK, Gillespie JM, Davis TA. Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA. Applied Geochemistry. 2018 Nov 1;98:127–140.
Journal cover image

Published In

Applied Geochemistry

DOI

EISSN

1872-9134

ISSN

0883-2927

Publication Date

November 1, 2018

Volume

98

Start / End Page

127 / 140

Related Subject Headings

  • Geochemistry & Geophysics
  • 3703 Geochemistry
  • 0502 Environmental Science and Management
  • 0402 Geochemistry