3D Seismic to absolute acoustic impedance inversion of the Lower Devonian Tadrart Sandstone in Ghadames Basin, NW Libya

Abstract

The aim of this study is to map 3D acoustic impedance from 3D post-stacked seismic data, and then predict 3D porosity values from the acoustic impedance results for the Lower Devonian Tadrart reservoir sandstone using seismic inversion. Theoretically, seismic inversion is the process of transforming seismic reflection data into qualitative rock properties such as acoustic impedance and porosity, which is also very important for reservoir evaluation. Seismic inversion can be performed on pre or post stacked seismic data, it can be applied when the conventional seismic interpretation may become misleading under certain conditions. Most of oil and gas companies use the seismic inversion to improve the seismic interpretation by removing the side lobes and tuning effects from seismic data, to improve the estimation of rock properties, and to increase resolution and reliability. Inversion of seismic reflection data for various lithological and petro physical attributes is broadly used for reservoir characterization and hydrocarbons detection. Rock property related attributes are easier to interpret than the seismic reflectivity, which is related to boundaries between zones of contrasting acoustic impedance properties. Broadly, the commonalities between all impedance type properties are in their relations to the values measured from the seismic traces. The fundamental problem is the lack of low-frequency information in the seismic data leading to many uncertainties in the solution. The absolute acoustic impedance inversion is the method that has been applied in this study, and it is applied in Hamra field, northwest Ghadames basin, the approach of this work by extrapolating the well logs information into the seismic properties, this is, in turn, better estimations of reservoir properties such as porosity and an additional benefit that the interpretation efficiency is greatly improved.