Abstract

Seismic inversion plays an important role in reservoir characterization starting from exploration to development phase of the field. Its role becomes more crucial and challenging in field development as it is needed to formulate the optimum well placement strategy so that hydrocarbon recovery can be maximized. Most of the time, it is found that reservoir properties of hydrocarbon bearing sand overlap with brine and background shale. Such challenges are generally addressed by various geophysical techniques including seismic inversion. Simultaneous inversion is the most widely used and acceptable method to characterize the reservoir. It has been observed that simultaneous inversion is not always suitable to discriminate class-1 oil sands and brine sands. This leads to the use of more advanced pre-stack inversion techniques like Extended Elastic Impedance Inversion (EEI). Simultaneous inversion (SI) exploits volume of angle/offset gather and partial stacks to generate elastic properties (P-impedance, S-impedance and density) using AVO equations. However, prediction of density is slightly less accurate due to poor signal to noise ratio at ultra far offset. Consequently, properties like lithology, density, resistivity etc, which correlate at higher angles or virtual angles (negative angles) are not very well captured by SI. EEI solves this problem very efficiently as it gives flexibility to a wider range of angles (+90o to -90o ). In the present study, Simultaneous Inversion and Extended Elastic inversion have been performed using more than 20 wells to characterize clastic reservoir, whose delineation was challenging due to overlapping of the elastic properties and reservoir thickness less than seismic resolution. Integration of EEI with conventional pre-stack deterministic inversion provides a significantly improved understanding of both reservoir facies and fluid distribution. Reservoir characterization is one of the essential and challenging parts of any field development. It is required to formulate the optimum well placement strategy so that returns on investments can be maximized by improving the recovery. In the present study, Seismic Data Inversion (SI and EEI) were used to support field development by optimizing and identifying development well locations for best productivity of oil and more than 25 wells were drilled with 100 % success rate.