Seismic inversion emerged as an important tool for reservoir characterization and quantifying reservoir properties. It combines geophysical, geological and petro physical data through a robust inversion scheme to extract more meaningful reservoir information. When compared to working with seismic amplitudes, inversion results show higher resolution with accurate interpretations, which in turn facilitates better estimates of reservoir properties such as porosity.

In this study, Mauddud carbonate reservoirs of western flank of Sabriyah, saddle part between Raudhatain - Sabriyah and South of Sabriyah were considered for porosity studies. The two fields namely Raudhatain and Sabriyah are well developed. The Mauddud Limestone of Upper Cretaceous is one of the main producer in these fields. Around 600 wells drilled over the main structures of these fields show good porosity development in Mauddud reservoir ranging from 15-35%.

This paper mainly deals to know the porosity development towards the Western flank of Sabriyah, saddle part between Raudhatain and Sabriyah and Southern part of Sabriyah through the post stack Constrained Sparse Spike Inversion (CSSI), which was successfully performed on a 3D seismic volume over a carbonate reservoir Mauddud. The Inversion results improved the structural model, closely represented the true sub-surface geology and predicted reservoir porosity. A relationship between acoustic impedance and porosity was established using well data and applied in transforming into porosity volume. This porosity volume was used to generate porosity maps for Mauddud reservoir interval to analyze the porosity distribution. The generated maps show moderate to good porosity development in the Western flank, moderate porosity developed in the saddle part, moderate to good porosity development in SE of Sabriyah field and some isolated porosity development in South West of Sabriyah field. This study has allowed understanding the internal reservoir heterogeneity, facies variation within the reservoir and has provided a strong base to refine the planning and placement of development and exploratory wells with higher confidence.

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