Petrographic, petrophysical, and geochemical characteristics of Barremian carbonate rocks from the Enguri High Arch Dam area (Georgia)

Joint petrophysical, geochemical, and petrographic studies on Barremian carbonate rocks from the Gagra-Java Zone at the transition of the Central Greater Caucasus to the Rioni Basin in Georgia are rare and almost absent in literature. In a joint research project between Georgian and German research institutes, this work showcases the first consistent dataset on rock properties, which are the foundation of the Enguri High Arch Dam, a large and regionally important energy infrastructure. The studied carbonate rocks from a 307 m deep research well are subdivided into two carbonaceous and two dolomitic sections, exhibit intense brecciation, represented by multiple rubble zones. Petrographic analyses in conjunction with petrophysical sample analyses do not show a clear correlation of rock properties to the rock’s microfabric. Generally, matrix permeabilities are low to very low (< 10 mD) and do not correlate with matrix porosities. Elevated matrix permeability is only found in samples from the topmost 120 m of the studied well, but is not restricted to samples exhibiting carbonate mineral dissolution (mostly dolomite dissolution), which can be observed along the whole studied well. ... mehrBased on cathodoluminescence analyses eight distinctly different phases of carbonate cement precipitation in brecciated sections and fractures can be distinguished and related to faulting and compressive tectonic phases resulting in the formation of stylolites. The analyses are supplemented by first UCS measurements (ranging from 19.9–175.0 MPa) to gain a better understanding on the mechanical properties of the studied samples.