Abstract: Multiple 3D Scenario Modeling of Reservoir Heterogeneity in the Khuff Carbonates of the South Pars Field, Offshore Iran

CLAYTON, CHRIS, ROBERT COOK and TOM HYDE

The South Pars Field is formed by an extremely large open periclinal structure with its axis trending approximately SW-NE. The reservoir formation in South Pars (Khuff carbonates) is a platform carbonate sequence of late Permian to early Triassic age, composed of a layered succession of limestones, dolomites and subordinate anhydrites. Larger scale (10's m thick) units within the Khuff are regionally correlatable from Saudi Arabia northwards as far as SE Iran.

The impact of lateral reservoir heterogeneity was judged to be the most significant geological uncertainty affecting sustainable field production performance and development planning. In order to assess its impact on the reservoir properties, several equally probable geological scenarios were generated (using Shell GEOCAP Software) containing varying amounts and types of of reservoir heterogeneity. The geological realizations vary with respect to both geological body geometries and the methods of reservoir property modeling.

The amount and/or type of heterogeneity present in the various models makes less than 5% difference to the contained GIIP. The volumetrics in all cases are dominantly influenced by the highly correlatable nature of the reservoir at the scale of a few 10's of meters or above. The static connectivity (i.e., volume of rock of a particular property connected to a certain interval in a well or wells) and dynamic productivity of the reservoir is however significantly influenced by the degree of reservoir heterogeneity. The perhaps non-intuitive result is that in general, the less heterogenous models have lower connectivity and slightly poorer performance than the more heterogenous models.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria