Home – Home – Jornals – Russian Geology and Geophysics 2013 number 1

Kuh-e Mond Field is a conventional heavy-oil resource in the Zagros Foreland Basin, Iran, produced from the fractured carbonates partially filled with dolomite, calcite, and anhydrite cement. Vitrinite reflectance data from carbonate reservoir suggest low-maturation levels corresponding to paleotemperatures as low as 50ºC. The observed maturation level (<0.5% R_max) does not exceed values for simple burial maturation based on the estimated burial history. Oil inclusions within fracture-filled calcite and dolomite cement indicate the key role of these fractures in oil migration.
Fluid inclusion temperature profiles constructed from the available data revealed the occurrence of petroleum in dolomite, calcite, and anhydrite and characterize the distinct variations in the homogenization temperatures (T_h). Fluid inclusions in syntectonic calcite veins homogenize between 22ºC and 90ºC, showing a salinity decrease from 22 to 18 eq. wt.% NaCl. Fluid inclusions in anhydrite homogenize at 50ºC, showing that the pore fluids became warmer and more saline during burial. The T_h range in calcite-dolomite cement depicts a change in water composition; therefore, we infer these cements precipitated from petroleum-derived fluids. The petroleum fluid inclusions microthermometry data suggest that the reservoir became filled with heavy black oils and high-salinity waters and indicate that undersaturated oil was present in a hydrostatically pressured reservoir.
The T_h data do not support vertical migration of hot fluids throughout the section, but extensive lateral fluid migration, most likely, drove tectonically dewatering in the south or west of the pool.