Source Rock Maturity from Seismic Data - Lowvelocity Anomalies as Potential Indicators of Hydrocarbon Generation

In this study we investigate the source rock maturity of the organic-rich Upper Jurassic Farsund and Lola formations in the southern Danish Central Graben. We do this by analyzing an interval velocity volume derived through seismic processing flows for discrete low-velocity anomalies occurring within the source rock succession. We have mapped the anomalies and calibrated them with source rock data within several wells in the study area. Although not unambiguous, our results indicate that some of the low-velocity anomalies potentially can be ascribed to variations in source rock composition and maturity, and hydrocarbon generation. Two critical steps are to 1) quality-check the utilized interval velocity volume i.e. rule-out any geophysical effects and artefacts and 2) calibrate the mapped low-velocity anomalies to source rock effects i.e. rule-out effects from other geological features such as lithological variations, porosity-permeability fluctuations, diagenesis, anisotropy, overpressure and clay content. Besides of using information from well logs and laboratory measurements on core and drill cuttings samples, calibration is based on utilizing seismic attributes and fluid flow features which address the overall migration routes in the conventional hydrocarbon plumbing system of the study area.