Full Azimuth Differential Seismic Facies Analysis (FACIVAZ) for Prediction of Oil Saturated Fractured Reservoirs

The traditional approach to seismic facies analysis using conventional stack cubes often gives an uncertain result and limits the possibility of reliable prediction of productive sections. This is because the seismic recording form in the stack data is the averaged result of the stacking of various traces from different azimuthal directions obtained from different angles of incidence-reflection. The report presents a new approach and the technology of full azimuthal differential seismic facies analysis (Facies analysis versus azimuth - FACIVAZ) with the use of full-azimuth seismic data to improve the accuracy of the qualitative prediction of oil-saturated zones into fractured reservoirs. The work (First Break, Vol 37, January, 2019) showed that in the fractured or fractured-porous reservoirs, distortions in the frequency composition of the reflected signals occur due to the azimuth-dependent effects of dispersion and absorption of seismic signals in oil-saturated fractured media. These frequency distortions ultimately affect on the trace shape depending on the azimuth of each ray’s pair. In the case of full-azimuth seismic exploration, using deep processing of pre-stack data in the local angle domain the change in the record trace form depending on the azimuth direction becomes especially noticeable and significant. This effects are registered in seismic record traces and are used in FACIVAZ technology for more accurate and reliable qualitative prediction of oil-saturated fractured zones into reservoirs. In the report are given the basis and the technological process of the proposed approach as well as real examples of using in seismic facies analysis in comparison with the traditional approach at two oil fields in CIS. In the azimuth-dependent interpretation of seismic facies, the degree of increasing the accuracy of the forecast was estimated using borehole information on well productivity. It is shown that the FACIVAZ technology increases lateral seismic facies field resolution and increases the accuracy of prediction of oil-saturated permeable reservoir zones in comparison with traditional technologies. FACIVAZ also increases the reliability of separating oil-saturated fractures from dry fractures and can be used both in combination with an integrated interpretation and in the task of operational support for drilling wells.