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Strontium isotopes as an indicator for groundwater salinity sources in the Kirkuk region, Iraq

Sahib, Layth Y. and Marandi, Andres and Schüth, Christoph (2016):
Strontium isotopes as an indicator for groundwater salinity sources in the Kirkuk region, Iraq.
In: Science of the Total Environment, Elsevier, pp. 935-945, 562, ISSN 18791026, DOI: 10.1016/j.scitotenv.2016.03.185, [Article]

Abstract

The Kirkuk region in northern Iraq hosts some of the largest oil fields in the Middle East. Several anticline structures enabled vertical migration and entrapment of the oil. Frequently, complex fracture systems and faults cut across the Eocene and middle Oligocene reservoirs and the cap rock, the Fatha Formation of Miocene age. Seepage of crude oil and oil field brines are therefore a common observation in the anticline axes and contamination of shallow groundwater resources is a major concern. In this study, 65 water samples were collected in the Kirkuk region to analyze and distinguish mixing processes between shallow groundwater resources, uprising oil field brines, and dissolution of gypsum and halite from the Fatha Formation. Hydrochemical analyses of the water samples included general hydrochemistry, stable water isotopes, as well as strontium concentrations and for 22 of the samples strontium isotopes (87Sr/86Sr). Strontium concentrations increased close to the anticline axes with highest concentrations in the oil field brines (300 mg/l). Strontium isotopes proved to be a valuable tool to distinguish mixing processes as isotope signatures of the oil field brines and of waters from the Fatha Formation are significantly different. It could be shown, that mixing of shallow groundwater with oil field brines is occurring close to the major fault zones in the anticlines but high concentrations of strontium in the water samples are mainly due to dissolution from the Fatha Formation.

Item Type: Article
Erschienen: 2016
Creators: Sahib, Layth Y. and Marandi, Andres and Schüth, Christoph
Title: Strontium isotopes as an indicator for groundwater salinity sources in the Kirkuk region, Iraq
Language: English
Abstract:

The Kirkuk region in northern Iraq hosts some of the largest oil fields in the Middle East. Several anticline structures enabled vertical migration and entrapment of the oil. Frequently, complex fracture systems and faults cut across the Eocene and middle Oligocene reservoirs and the cap rock, the Fatha Formation of Miocene age. Seepage of crude oil and oil field brines are therefore a common observation in the anticline axes and contamination of shallow groundwater resources is a major concern. In this study, 65 water samples were collected in the Kirkuk region to analyze and distinguish mixing processes between shallow groundwater resources, uprising oil field brines, and dissolution of gypsum and halite from the Fatha Formation. Hydrochemical analyses of the water samples included general hydrochemistry, stable water isotopes, as well as strontium concentrations and for 22 of the samples strontium isotopes (87Sr/86Sr). Strontium concentrations increased close to the anticline axes with highest concentrations in the oil field brines (300 mg/l). Strontium isotopes proved to be a valuable tool to distinguish mixing processes as isotope signatures of the oil field brines and of waters from the Fatha Formation are significantly different. It could be shown, that mixing of shallow groundwater with oil field brines is occurring close to the major fault zones in the anticlines but high concentrations of strontium in the water samples are mainly due to dissolution from the Fatha Formation.

Journal or Publication Title: Science of the Total Environment
Volume: 562
Publisher: Elsevier
ISBN: 0048-9697
Uncontrolled Keywords: Kirkuk oil fields,L. Fars (Fatha) Formation,Oil field brine contamination,Oil seepage,Sr isotope ratio
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Earth Science > Hydrogeology
Date Deposited: 17 Apr 2018 12:03
DOI: 10.1016/j.scitotenv.2016.03.185
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