f Diagenesis of the Upper Oligocene Sandstones from a Well which Located Erzurum Around

In the study, diagenesis of Upper Oligocene aged Kömürlü and Penek Formations sandstones from a well which located Erzurum around at Aşkale sub-basin in the East Anatolia basin were determined by using completely the subsurface datas (core samples). The diagenetic history of the Upper Oligocene Sandstones from a well which located Erzurum around is described based on petrological analysis of samples. Diagenesis in the sandstones principally involves the progressive development of various types of cements in the following order: Calcite and feldspar formation, smectite, mixed layer smectite-illite and smectite-chlorite authigenesis, illite, chlorite authigenic minerals, and quartz overgrowths. After the formation of the quartz overgrowths phases there is a dissolution phase creating secondary porosity via the dissolution of grain framework and cement. These secondary porosity zone consist of reservoir properties for hydrocarbon formation. Authigenic minerals affect negatively these sandstones hydrocarbon reservoirs.