Sandstone Diagenesis of Hazro Formation in S. Hazro Field, Southeast Turkey

CUBUKCU, AYLA, Turkish Petroleum Company, Ankara, Turkey

S. Hazro field is located south of Hazro, southeast Turkey. The Lower-Middle Devonian Hazro Formation, which averages 150 m in thickness, is divided into three lithofacies. The Lower Clastic Member is dominated by fine- to medium-grained quartzarenites, interpreted as tidal flat and barrier-bar deposits, with an average thickness of 60 m, bearing gas and condensate. The Upper Clastic Members (consisting mainly of sandstones and dolomite) are of poor reservoir quality.

Observations through core and epoxy-impregnated thin section analyses give porosities ranging from 1 to 25% in the sandstones of the Lower Clastic Member. Many well-sorted sandstones with high porosities show evidence of dissolution of lime mud and lack of late diagenetic dolomite cement.

Most probably the paragenetic sequence is (1) formation of anhydrite and lime mud cement; (2) dissolution of lime mud and enhancement of secondary porosity; (3) formation of euhedral dolomite and silica overgrowths in the pores; (4) authigenic clay formation; and (5) late diagenetic dolomite cementation.

The main authigenic clays that are most abundant in porous sandstones are grain-coating Fe-chlorites, mixed layer illite-chlorites, and pore-bridging hairy illites.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)