Quantitative Implementation of Acoustic Impedance Inversion to Porosity and Lithology Prediction of Clastic Reservoir, Luhais Oil Field, Southern Iraq

Abstract

In the present study, some of petrophysical properties of Nuhr Umr Formation in Luhais oil field (south of Iraq) are evaluated by using an acoustic impedance inversion process. 2D seismic reflection data of (29) lines covering the field, neutron porosity logs, and synthetic acoustic impedance logs were used in inversion of seismic sections into an acoustic impedance and porosity sections. To compensate the low frequency in relative acoustic impedance that rely on seismic data frequency (band-limit frequency), we inverted relative acoustic impedance with combination the low frequency of well data to obtain absolute acoustic impedance. The absolute acoustic impedance shows consistency and good tie with an acoustic impedance log. At the reservoir interval the lithology was discriminate and evaluate the facies quality of Nahr-Umr Formation using absolute acoustic impedance inversion and subdivided into three main members. The shale facies indicate high porosity (25%) corresponding to low acoustic impedance (6500 Kpa. m/s) at the top of the reservoir. The petrophysical analysis declare and confirm higher quality reservoir is noticed and recognized in the middle member of Nahr-Umr reservoir.

Keywords: seismic inversion, porosity prediction, Absolute Acoustic impedance