The mid‐Cretaceous Sarvak Formation, the second‐most important reservoir unit in Iran, is composed mainly of grain‐supported carbonates. For the purposes of this study, flow units in the upper part of the formation were identified, mapped and classified as part of an integrated reservoir characterization study at a giant oilfield in SW Iran. Pore types and geometries, pore‐scale diagenetic history and core‐scale depositional attributes were logged using conventional petrographic and lithological methods. The resulting data were combined with core descriptions, mercury‐injection capillary pressure data, and wireline log and geophysical data to identify five reservoir rock types: (i) highly oil‐stained, grain‐supported carbonates, including patch reef and barrier complex deposits with high porosities and permeabilities; (ii) leeward and seaward shoal deposits including grain‐supported packstones and skeletal wackestones with high porosities and permeabilities; (iii) dominantly mud‐supported lagoonal and open‐marine facies with fair porosity and permeability; (iv) grain‐supported but highly cemented facies which had poor reservoir characteristics; and (v) calcareous shales and shaly limestones with no reservoir quality. Based on the reservoir rock types, eight flow units were recognised. Subsequently, four reservoir zones were defined based on these flow units at a field scale. This study has contributed to our understanding of flow units in this complex carbonate reservoir, and has improved our ability to characterize and model the architecture of the reservoir from pore to core to field scale.

-Planktonic foraminiferal biostratigraphy of the Gurpi Formation at the Danial section in northeast Izeh, the Zagros Basin, Iran, provides improved age resolution and good biostratigraphic control for late Cretaceous to Paleocene strata. The section was examined based on biostratigraphy, geochemistry, and lithology. The recorded fauna are of open marine forms, and most of the Late Cretaceous-Paleocene standard tropical/subtropical planktonic foraminiferal zones are represented. The high biostratigraphic resolution represented by Plummerita hankeninoide for the Late Maastrichtian and Guembelitria cretacea for the Early Danian, together with the Ir anomaly, represent a continuous Cretaceous-Paleogene (K-Pg) succession in the studied area. The sudden extinction of 42 out of 53 species at the K-Pg boundary, especially in globotruncanids and large heterohelicids, indicates a sudden change in tropical-subtropical deep photic sea water under the mesotrophic conditions of the Late Maastrichtian. On the other hand, planktonic foraminifera experienced relatively high stress conditions during this time as indicated by the low species richness and low abundance of globotruncanids simultaneously with blooms of the disaster opportunist Guembelitria species.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe quantity of direct interest in the flow through porous media is not the properties of the matrix (e.g. grain size distribution) but rather the properties of the pore (e.g. pore size distribution). The determination of representative capillary pressures is of vital important for the mapping of the reservoir fluid distribution. Mercury porosimetry or mercury injection-capillary pressure curves are commonly used to measure the distribution of pores and pore throat sizes. Pore aperture size estimated from mercury injection tests has been used to categorize the rock by pore type, evaluate seals for traps and to explain the locations of stratigraphic hydrocarbon accumulations.In image analysis, the OM (Optical Microscopy) images provide macroporosity information, whereas the ESEM (Environmental Scanning Electronic Microscopy) images yield information on microporosity. Comparison of total porosity determined from plugs indicates that macroporosity and microporosity values based on image analysis match the plug data, confirming the validity of the method. The combination of macroporosity and microporosity data yields pore size distribution and pore shape information that can explain the distribution of physical properties, in particular permeability. Permeability can mainly controlled by the macropore shape in high-permeability samples, and by the amount of intrinsic microporosity in the low permeability samples.In this investigation three pore and port geometric systems have been recognized, 1) Type-1 system that belongs to mud dominated bioclastic peloidal packstone, at the top of reservoir, with good porosity and fair permeability shows large and smooth pores and ports as bimodal, 2) Type-2 system presented in mud dominated bioclastic peloidal packstone / grainstone with fair porosity and low permeability shows moderate to small pores and ports and 3) Type-3 system that has been seen in ploidal bioclastic grainstone and mud dominated planctonic foraminiferal packstone, packstone /wackestone and wackestone with low porosity and low permeability shows small pores and ports as matrix porosity.

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