Spatial analysis and environmental impact assessment of Ordovician oil shale using ArcGIS: A case study of North Eastern Estonia

Obinna Nzekwe
Technische Universität Darmstadt, Institute of Applied Geosciences, Schnittspahnstr. 9, 64287 Darmstadt, Germany
[email protected]

The Late Cambrian to Ordovician crustal section of Estonia contains kukersite oil shale as well as graptolite argillite. These are widespread georesources (except kukersite) characterized by specific geochemical signatures, with high amounts of U, Mo, Zn, Pb and other metals.

Geoenvironmental modelling using spatial analysis tools in ArcGIS software, PAST statistical software and 3-D modelling with GOCAD have been used to integrate geologic, geochemical and environmental information to evaluate, better understand and spatially analyze the graptolite argillite in Estonia. Spatial analysis of well data reveals that relatively high contents of microelements: U (>200 ppm), Pb (>200 ppm), Mo (>300 ppm), Zn (>200 ppm), V (>1000 ppm), Th (> 11 ppm) and Ag (>0.7 ppm) occur in northeastern Estonia. Thickness of argillite ranges from 0.10 m to 8 m. Furthermore, Spearman’s rank-order correlation test suggests weak to no monotonic association between contents of microelements and depth of the upper surface of graptolite argillite. Principal component analysis seperates the microelements into three associations: (1) V, Mo and U; (2) Pb and Ag; (3) Zn and Th, which also show no correlation with depths. Thus quality and quantity is very heterogeneous. At the same time, both well distribution throughout the target area and knowledge on spatial quality/quantity distribution are not satisfying.

This study aims to (1) work out spatial variability of the metalliferous organic-rich shale in northeastern Estonia, (2) assess related potentials and (3) develop best-use scenarios in order to minimize negative impacts of oil shale mining to human health and environment.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects