PREDICTION OF OPEN FRACTURES IN THE ASMARI FORMATION USING GEOMETRICAL ANALYSIS: AGHAJARI ANTICLINE, DEZFUL EMBAYMENT, SW IRAN

M. Vatandoust^* and A. Farzipour Saein^*+

* Department of Geology, Faculty of Sciences, University of Isfahan, PO Code 81746-73441, Isfahan, Iran.

+ Corresponding author, email: a.farzipour@sci.ui.ac.ir, asaein@gmail.com.

Key words: Asmari Formation, Aghajari field, Zagros fold-and-thrust belt, Dezful Embayment, Iran, curvature analysis, geometrical analysis, fracture analysis.

Reservoir quality in the carbonates of the late Oligocene – early Miocene Asmari Formation at oilfields in SW Iran is enhanced by the presence of a well-developed fracture network. In anticlinal structures, fracture density is partly controlled by geometrical parameters such as the fold curvature. In this study, a geometrical analysis of the Asmari Formation at the NW-SE oriented Aghajari Anticline in the Dezful Embayment is presented, and is based on inscribed circle and curvature analyses of the fold. Iso-curvature and fracture potential maps of the Asmari Formation based on the geometrical analysis are compared to the results of fracture density logs determined from image logs at four widely-spaced wells, and to dynamic mud loss data. The geometrical analysis demonstrates that in areas of high curvature (such as the SE and NW parts of the SW limb of the Aghajari Anticline and the central part of the NE limb), the fracture density is high. Regions of high curvature (in plan or section view) have the greatest potential to develop open fractures. The predicted fracture density distribution based on the geometrical analysis of the Asmari Formation is in good agreement with actual fracture data from the four wells and with mud loss data from the Aghajari oilfield.

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