Cross plotting elastic parameters derived by seismic amplitude inversion targeting a carbonate geothermal reservoir, Northwest Hungary

Abstract Seismic amplitude variations with offset hold valuable insights into rock density and two key elastic properties: compressional and shear velocities (or impedances). These parameters are derived by performing simultaneous inversion of multiple P-wave offset reflection stacks. Before inversion, wavelets for each offset stack are computed separately, enabling compensation for offset-dependent effects such as phase shifts, bandwidth variations, tuning, and NMO stretch. This correction enhances the accuracy of amplitude and phase spectra in the processed data. The resulting impedance volumes can be analyzed individually or integrated with other geophysical indicators to identify rock facies. Within this framework, the Lamé parameters Lambda and Mu prove especially useful. Well log analyses indicate that the geothermal reservoir fracture carbonate exhibits lower Lambda, corresponding to reduced incompressibility, and higher Mu, indicating increased rigidity. Our novel method supports the interpretation of fracture carbonate in the targeted Little Hungarian Plain region, where conventional P-wave impedance cannot easily differentiate reservoir fracture zones. Utilizing stiffness contrasts related to hot water-bearing fractures within the simultaneous inversion results allows effective discrimination of these geothermal features.