Full-azimuth differential seismic facies analysis for predicting oil-saturated fractured reservoirs

This work presents a novel technology for azimuth-dependent facies analysis (Facies Analysis versus Azimuth — FACIVAZ) to improve the prediction of hydrocarbon-saturated permeable fractures in terrigenous carbonate reservoirs. The analysis is performed in the depth domain along high-resolution, full-azimuth, angle domain common image gathers created by the EarthStudy 360™ Local Angle Domain (LAD) imaging system. The amplitude and phase preservation of the seismic reflectivities obtained by this imaging system is crucial to the proposed analysis. Prior to the facies analysis, the general orientation and intensity of the target fracture systems are analysed and characterized by azimuth-dependent velocity and amplitude analyses (VVAZ and AVAZ) performed along these LAD gathers. The remaining effects of the azimuth-dependent (and frequency-dependent) absorption and dispersion on the LAD gather events are then detected and further connected to the rate of the existing oil-saturated fractures within the reservoirs. The examples presented in this article show the effectiveness of the proposed FACIVAZ technology in accurately predicting the distribution of seismic facies in target production areas associated with oil-saturated fractured reservoirs in Western Siberia and Middle Volga. The results strongly agree with the corresponding facies characteristics measured in the boreholes along the reservoir area, and therefore serve as valuable information for the drilling decisions of new wells.