Natural fractures and faults in the subsurface play an important role in fluid flow and accumulation. Therefore, identifying and mapping the distribution of fractures and faults systems is critical to understanding the fluid dynamics within a reservoir.
Although fractures and small-throw faults are not easily identifiable using conventional 3-D seismic techniques, their orientation and intensity can often be inferred using seismic attributes such as coherence and seismic curvature.
This case study will demonstrate how seismic curvature was used to map small scale fractures in a Saudi Arabian oil field which has been affected by premature water breakthrough. Premature water breakthrough is an increasing concern to all the geoscientists and engineers involved in developing the field. Curvature illuminates subtle fracturing that was difficult to detect with conventional seismic amplitudes. Using curvature allows geoscientists to map, for the first time, small-scale fractures believed responsible for bringing water prematurely to the top of the reservoir. The integration of image logs, zones of lost fluid circulation, production test and well test data has increased our interpretation confidence and helped optimize the placement of future horizontal wells.