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Using ??87Sr values to identify sources of salinity to a freshwater aquifer, Greater Aneth Oil Field, Utah, USA

Chemical Geology

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, ,
DOI: 10.1016/S0009-2541(97)00063-6

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Abstract

Salinity increases in water from the freshwater Navajo aquifer in the Aneth area have been documented in recent years. Previous studies during the 1980s in the Aneth area suggested that brines associated with oil production and their subsequent re-injection were the probable source of salinity in the Navajo aquifer. Differences in the delta strontium-87 (??87Sr) composition of ground-water samples from southeastern Utah were used to determine if oil-field brine or water from the upper Paleozoic aquifer is a plausible source of salinity to the Navajo aquifer. The ??87Sr values of the oil-field brine samples (mean = -0.95???, range = -1.06 to -0.19???, n = 5) are substantially more negative than the values in water samples from wells completed in the Navajo aquifer (mean = 0.73, range= -0.85 to 2.02???, n = 48), indicating that oil-field brine is not a source of salinity. The ??87Sr values in water samples from wells completed in the upper Paleozoic aquifer (mean = 0.80???, range = 0.34 to 1.10???, n = 4) are similar to the mean isotopic composition of the more saline water from the Navajo aquifer. The ??87Sr values in water from the Navajo aquifer confirm that two distinct flow areas are present. Mixing models using the ??87Sr values and Sr concentrations of non-saline water from the Navajo aquifer and saline water from the upper Paleozoic aquifer indicate that water from the upper Paleozoic aquifer is a plausible source of saline water to the Navajo aquifer. Most Navajo aquifer wells that contain water with a ??87Sr signature similar to water from the upper Paleozoic aquifer are located within or adjacent to an area where the hydraulic gradient is favorable for upward movement of water from the upper Paleozoic aquifer into the Navajo aquifer. ?? 1997 Elsevier Science B.V.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Using ??87Sr values to identify sources of salinity to a freshwater aquifer, Greater Aneth Oil Field, Utah, USA
Series title:
Chemical Geology
DOI:
10.1016/S0009-2541(97)00063-6
Volume
141
Issue:
3-4
Year Published:
1997
Language:
English
Publisher:
Elsevier
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Chemical Geology
First page:
195
Last page:
209
Number of Pages:
15