Inversion of Amplitude Versus Offset (AVO) results are used to derive elastic rock properties. These rock properties can be used for quick determination of lithology and fluid content for exploration/development of reservoirs. The AVO inversion methods such as Elastic Impedance inversion (EI) and LMR (Lambda-Mu-Rho) inversion are used and calibrated with porosity observed on well logs and on core plugs from a field in north-east Oklahoma, USA.