Reservoir heterogeneity, sedimentology, and diagenesis of ordovician bedinan formation, southern diyarbakir basin, se turkey: paleogeographic implications

Yıldız, Gökay.
Recent high-quality oil discoveries in SE Turkey, specifically Diyarbakır Basin from the Ordovician aged Bedinan Formation sandstone reservoir levels have introduced many questions. The fact that variable hydrocarbon production rates in the studied wells oblige us to delineate internal framework of the sandstone levels and to find the answer for the reason of the reservoir heterogeneity which will be a proxy to find convenient well stimulation methods in order to increase hydrocarbon recovery. In this study, Gazzi-Dickinson method of point counting on thin sections, X-ray computed tomography imaging technique, semi-quantitative X-ray diffraction (XRD) bulk powder mineral analysis, seismic lines, wireline log data, and available well data were used to understand the depositional environment, the paleogeography during the geological evaluation, the mineral framework and the provenance of the levels of interest. Additionally, petrophysical log interpretation via Petrel software together with regional stratigraphy and correlation studies were carried out to explain the reason and scale of the reservoir heterogeneity. As a consequence of the studies, it is seen that the subarkose to quartz arenitic sandstone levels of the Bedinan Formation were deposited between the lower and vi upper shoreface of an ice-distal glaciomarine depositional environment. Additionally, the origin of sandstones are related to igneous and cratonic sources. The most important result of this study on the reservoir heterogeneity of this sandstone levels of uppermost Bedinan Formation is that besides the depositional facies, structural features and compaction, particularly diagenetic clay coating minerals (illite, kaolinite and illite/smectite mixed clay layer) together with quartz and carbonate cements have exerted great control on the reservoir quality in meters scale, which results in variable hydrocarbon production rate.