Natural fractures in the Upper Sarvak Formation in the Lurestan Zone, the Zagros Basin, Iran

Document Type : Research Paper


1 Department of Geology, Faculty of Science, Bu-Ali Sina University, Hamedan, Iran

2 Department of Statistics, Faculty of Science, Bu-Ali Sina University, Hamedan, Iran


Two surface sections of the Sarvak Formation in the Lurestan zone (Zagros fold-thrust belt) were examined to inspect the naturally occurring fractures. The inspected are located sections in the Surgah anticline and the Kuh-e-Charmi anticline; in the Ilam and the Kermanshah provinces respectively. The Sarvak Formation was carefully examined to record the fracture types, their spatial distribution, spacing and cross-cutting relationships. Detailed examinations were undertaken on 420 fractures, 40 core plugs porosity and P-wave velocity and 205 thin sections. Three genetic types of fractures including tectonic, pressure-solution and dissolution related fractures were identified. The tectonic related fractures include two main sets (namely with NW-SE and NE-SW trends). In addition, distinguished two types of stylolites include the bed-perpendicular and the tectonic stylolites (bed-parallel); that postdate the fractures (veins). The Sarvak Formation underwent various diagenetic processes in couple with fracturing. The pore types include microporosity, intergranular porosity, mold porosity and fracture-stylolite. Petrophysical measurements (performed on some core plugs prepared from surface block samples), show that the carbonates of the Sarvak Formation have low porosity (74% of the samples have less than 3%) and high compressional wave velocity (Vp), (96% of the samples have 6000 m/s), Therefore, it could be concluded that the Sarvak Formation is a tight interval in a reservoir aspect.


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