Sedimentology and geostatistical modeling of Quwarah Member, Qasim Formation: Paleozoic sandstone reservoir outcrop analog, Saudi Arabia

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Saudi Digital Library
This study aims to establish, from outcrop reservoir analog description, a geological and petrophysical model for the Paleozoic oil and gas Quwarah sandstone reservoir in central and eastern Saudi Arabia. The model is intended to provide database and enhance understanding and prediction of the reservoir behavior in the subsurface. The study is carried out at Qasim area where Quwarah Member of Qasim Formation (Middle to Late Ordovician) outcrops. The methods and techniques adopted in this study include field sedimentological facies analysis on outcrop sections, and sample collection for laboratory permeability measurements, petrographic analysis and porosity measurements form thin sections. The facies porosity and permeability data are integrated for purpose of description and characterization of the sandstone reservoir through construction of quantitative models using geostatistical modeling techniques. Based on the sedimentological fades analysis, the study subdivided Quwarah member into three parts (lower, middle and upper) with distinctive facies. The petrographic properties and diagentic features of the Quwarah member have been thoroughly studied to identify the depositional environments of the lower, middle and upper parts of the member. The generated 2 D model of the spatial distribution of porosity on Quwarah member demonstrated spatial behavior that reflects the depositional environments of the three parts of the Quwarah member. The 2 D permeability model showed a good agreement between high porosity and permeability values at the upper right part of the section. However, low porosity values are dominant at the left part and lower right part. This may reflect the depositional facies and diagentic variation within transitional (lower part) and the tidal/intertidal (middle/upper part) environments.