Seismic Curvature Attributes for Subtle Fault Detection in Tight Volcanic Reservoirs from Barmer Basin, India

Abstract

Abstract The current study area, Raageshwari Deep Gas field is situated in the southern part of onshore Barmer Basin in Rajasthan, India. The field contains a gas condensate reservoir with excellent gas quality within the dominantly volcanic formations (Basalt and Felsic) and overlying clastic Fatehgarh Formation. These are tight reservoirs and optimal field development necessitates reasonable characterization of faults and natural fractures thereby aiding well placement by targeting areas of enhanced permeability for better well performance. The minor faults with throws significantly less than the duration of the seismic wavelet may not be detected in variance attribute data. However, reflection curvature is an attribute that also relates to structural deformation and shows greater spatial resolution. The detailed structural lineaments revealed through this analysis are indicative of sub-seismic faults and possible increased intensity of natural fractures. The maximum and minimum curvature data help to accentuate small scale reflection geometry changes and can be used to interpret minor faults. To discriminate stratigraphic features and identify fracture zones, careful calibration was done with production data, image logs and microseismic measurements from the wells. The curvature attributes highlighted lineament distributions, interpreted to be small scale faults and subtle structural deformations associated with fractures. Lineaments of fault/fracture from curvature attributes were observed to correlate with interpretations from borehole image logs. Detected subtle faults were further validated with other measurements like microseismic and production data. These well calibrations provide confidence in the use of specialized seismic attributes for fracture characterization in the field. Results of this study will be used for optimal placement of infill wells for enhanced field productivity.