Pore types distribution and their reservoir properties in the sequence stratigraphic framework: a case study from the Oligo-Miocene Asmari Formation, SW Iran

Pore type distribution is among the most important factors controlling fluid flow in heterogeneous carbonate reservoirs. This study aims to determine pore type distribution through wells and inter-well locations (micro- to field scales) in the most important heterogeneous reservoir of SW Iran, the Asmari Formation. In this regard, pores are classified into three main classes (stiff or diagenetic, reference or depositional, and cracks or tectonically) and six subclasses (intraparticle, moldic/vug, microporosity, interparticle, intercrystalline, and fracture), based on their elastic, petrophysical, and dynamic properties. In each subclass, the relevant static and dynamic attributes of the pore system such as average porosity, permeability, T2 distribution, pore size, capillary pressure, and flow zone index (FZI) are also determined. Variation of these parameters within these six subclasses is predicted along wellbore, using core data and the velocity deviation and nuclear magnetic resonance (NMR) logs. These results are then used in an integrated pore typing approach, which incorporates the data from petrophysical properties and dynamic behavior of pores (pore type distribution data) with those of depositional and diagenetic aspects. Using sequence stratigraphy, the dominant pore types (subclass) and their relevant properties are determined then extrapolated from micro- to mega- (field) scales. The spatial distribution of pore types at the field scale provides a clue for the tracking of high and low permeable zones across the field.