Improving Reservoir Heterogeneity Prediction and Well Placement by Interim Seismic Acoustic Impedance Inversion

Abstract

Abstract Improving seismic data quality prior to acoustic impedance (AI) inversion is one of the main challenges for interpreters. Proper reprocessing of seismic data may attenuate most of the noise and multiples but it can be costly and time-consuming. Therefore, while data reprocessing is in-progress, an interim solution is implemented to enhance 3D seismic quality. The solution was an effective data conditioning workflow that significantly improved seismic quality for satisfactory inversion results. Having achieved acceptable seismic data quality, we inverted the seismic volume to estimate acoustic impedance. A seismic porosity model is transformed from this acoustic impedance and used for reservoir heterogeneity prediction and well placement. The analysis indicates that the wavelet equalization is a very useful tool for stabilizing the wavelet phase and amplitude spectrum in the study area. To ensure stability of the seismic wavelet at well locations, wavelet extraction is performed before and after wavelet equalization. The structural and stratigraphic interpretation is significantly improved by inverting the conditioned seismic data to relative acoustic impedance (RAI). The acoustic impedance estimates is validated by comparing them with well log values. This validation is essential to quantify the depth conversion and to provide optimum guidelines for drilling/geo-steering. Therefore, the final acoustic impedance inversion is showed good correlation with well log data. The inversion results are successfully used to position new horizontal wells in the study area. Our experience revealed the importance of acoustic impedance inversion in guiding geo-steering wells, particularly in heterogeneous reservoirs. However, the limitation of vertical seismic resolution remains the main challenge. The study provides best practice of seismic data optimization by stabilizing wavelet phase before inversion. Ultimately this improved our ability to position horizontal wells in heterogeneous reservoirs.