Investigating the Impress of the Active Tectonics and the Rate of Fractures in Ilam Formation, Fars Area, SW Iran

Abstract

The evolution of the Active Tectonics of the Ilam Formation (Santonin) form potential reservoir rocks at oilfields and structures in costal fars. Core and cuttings samples and wire-line logs from wells in the East Gardan field were used to investigate microfacies types and porosity evolution. Facies modelling was applied to predict the relationship between facies distribution and reservoir characteristics to construct a predictive geologic model which will assist future exploration in East Gardan field. Microfacies analysis and electrofacies identification and correlations indicate that the limestones of the Ilam Formation were deposited in a ramp setting. The ramp developed over the distal margin of the Santonin proforeland basin, adjacent to the evolved forebulge. Inner ramp facies are characterized by carbonate bank bioclastic packstones. Middle ramp facies dominate the Ilam Formation and consist of bioturbated, massive, dolomitic and bioclastic limestones. Bioclasts include benthic and planktonic foraminifera. Intense less common Palaeophycus bioturbation has enhanced the porosity of this facies. Outer ramp deposits consist of alternating mid-ramp bioturbated bioclastic massive limestones and argillaceous and marly limestones. Bioclastic packstones and intensively bioturbated bioclastic limestones of the mid-outer ramp are the primary source of fabric-selective porosity which is greatly enhanced by diagenetic overprints.