Azimuthal Seismic Fracture Detection in a Carbonate Reservoir - Integrated Seismic P-Wave Study

Understanding the distribution of fractures in carbonate reservoirs can greatly improve modeling of production rate and flow anisotropy. Seismic anisotropy may be a cost-effective technique sensitive to open fractures affecting flow, and can provide volumetric information on fracture properties. This talk focuses on azimuthal AVO effects at interfaces between fractured and unfractured rocks. We calculate AzAVO attributes for a Cretaceous limestone reservoir in East Texas. The workflow integrates inversion results with rock physics, forward seismic modeling, dipole sonic and image logs, and core to interpret azimuthal attributes relative to geology and production data. AzAVO inversion results for the field show anomalies that broadly tie to fracture indicators and are geologically reasonable. Anisotropy magnitude aligns with many NE-trending faults, which is consistent with fault-related fracturing. AzAVO orientations generally parallel ENE-trending fractures in core, maximum horizontal stress from image logs, and fast-velocity direction from a dipole sonic log. However, moderate to poor seismic data quality and sparse geologic well control limit our confidence in quantitative fracture prediction. Overburden effects manifested by amplitude dimming degrade AzAVO inversion quality over the structural crest and highlight the sensitivity of the inversion algorithm to amplitude artifacts.