Converted Wave AVO QC and Joint PP-PS Density Inversion at Clair Ridge

High-quality converted wave (PS) imaging and amplitude variation with offset (AVO) products can assist geological interpretation and are important to decouple the response of pressure and fluid effects. Ultra-high density ocean-bottom node (UHDOBN) acquisition over Clair Ridge, West of Shetland, U.K., was designed to record low seismic frequencies that were preserved and enhanced by processing including source deghosting. Model building added velocity details and updated the low-frequency model by full-waveform inversion and ensured a good PP-PS tie through joint PP-PS tomography with an event match constraint. AVO QC was extended to PS data and applied during processing to monitor wavelet stability and amplitude compliance for the post-migration workflow. Post-migration processing led to an improvement in wavelet predictability and reduced side lobes that can be advantageous for the inversion. PS AVO QC may also be applied for pre-migration processing steps. PP-PS joint AVO inversion for velocity and density showed improved property estimates and match to well logs when compared to single wavefield inversions. High-quality PS imaging and successful inversion has increased confidence in using PS inversion products beyond imaging, to assist with interpretation between wells.