Stochastic Inversion-Driven Petrophysical Modelling in Sub-Tuning Reefal Carbonates: Soğucak Formation, Thrace Basin, Türkiye

Seismic inversion plays a critical role in populating subsurface properties into geomodel; however, its effectiveness is often constrained by the resolution limits of seismic data. This study evaluates the effectiveness of stochastic versus deterministic acoustic-impedance inversion for estimating total porosity (Φ_total), effective porosity (Φ_e) and permeability (K) in the complex reefal carbonates of the Soğucak formation, Deveçatağı oil field—northwestern Thrace Basin, Türkiye—whose thickness ranges from 2 to 57 m. The wedge model indicates a tuning thickness of 60 m in Soğucak formation which limits the vertical resolution of the deterministic inversion that directly affects the geomodel resolution. To address this challenge, a stochastic inversion was performed to resolve beds below the tuning thickness, using a high-resolution 1 millisecond (ms) vertical sampling grid and producing non-unique, fine-layered impedance realizations. Petrophysical relationships were established using 75 core plugs showing strong porosity–permeability trends that were cross-validated with wireline logs. These relationships were applied to acoustic-impedance volumes derived from both deterministic and stochastic inversion. Correlations at well locations used in the model are naturally higher due to constraints from acoustic-impedance logs; therefore, we emphasized blind-well correlations to assess predictive performance at locations without well control. Blind-well tests at W-2, W-4, W-6 and W-11 demonstrate valid predictive capability, with stochastic inversion achieving correlations of 0.65–0.73 compared to 0.45–0.52 for deterministic inversion, effectively resolving sub-tuning thickness beds and reliably predicting porosity and permeability. By overcoming the resolution limitations of deterministic inversion, stochastic inversion supported by robust petrophysical relationships—when applicable—provides a reliable and field-proven tool that can be adapted to carbonate reservoirs in diverse geological settings worldwide.