Sahib, Layth Y. (2019)
Crude oil and oil brine seeps: sources, detection and environmental effects in soil and water, Kirkuk NE Iraq.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

Natural hydrocarbons have extensively contaminated both the hydro-lithospheres, damaging the environment and the health of the people living in the Kirkuk region of North-East Iraq, which is an area with a world´s significant crude oil reserves as well as various hydrocarbon seeps and brines. The study area is located in the Zagros fold-thrust belt, within the Low Folded Zone in the northeast of the Mesopotamia basin. Complex fracture systems and faults frequently cut across the Eocene, and middle Oligocene limestone reservoirs and the evaporates Miocene cap rock. High-density maps of the detected faults and lineaments within Fatha Formation have interpreted as potential seepage locations, even for seeps that are not exposed on the surface. The present thesis aims to investigate hydrocarbon seeps, and oil brine seeps contamination impact on the surface, groundwater as well as the soil’s physical and chemical properties. Therefore, various methods were used starting by identifying the origin of the seeps as a base to assess the source and ending by estimating the contamination level of hydrocarbons and related brines in water and soil directly or remotely. The essential concept of the present thesis is based on the known hydrocarbon seepage sits – which were recorded for hundreds of meters on the surface – and the sub-surface properties of the stratigraphy and hydrogeology conditions. In addition to the several reports and studies, the primary data source was based on the wide variation of the collected samples, i.e., crude oil and brine water samples from the selected oil reservoir to define the reservoir characterization and migration level. Moreover, the reservoir oil types were used to compare them with surface crude oil seeps samples. The surface and groundwater from the selected location and different aquifers beside soil and rock samples explained the aquifer's recharge and led to the appropriate speculation of the hydrodynamic and hydrogeological conditions. The measurements included: a) oil density, organic and inorganic components and biomarkers for crude oil samples, and polycyclic aromatic hydrocarbon PAHs; b) hydrochemistry, stable isotopes; and c) the spectral reflectance behavior of crude oil and different contaminated soil samples, organic components (organic carbon (OC) and total petroleum hydrocarbons (TPHs)) and x-ray diffraction to explain the chemical composition of the soil samples. The multiple data were transformed into one database, and the results were used to complete the final hypotheses in a conceptual model, which explains the mixing mechanism of crude oil and brine seeps with the surrounding environment. The strontium isotopes (87Sr/86Sr) showed the mixing processes between shallow groundwater resources, uprising oil field brines and differentiates it from the dissolution of gypsum and halite from the Fatha Formation. The final discussion and conclusions connect all of the results and try to simulate the sub-surface hydraulic conductivity and highlight the contamination zones that were explained in the final comprehensive conceptual model, enriching our knowledge of the petroleum and the hydrogeology systems of the selected fields within the Zagros fold-thrust belt. The obtained results mainly highlight the reasons behind the environmental consequences that can be a threat to the human health. The conclusion of this study opens the door to compare the findings with other locations within the study region, which contains similar complex stratigraphy and structures.

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