Advanced Acquisition and Processing Schemes for Multi-Well and Multi-Fibre Walkaway DAS-VSP Datasets from a CCUS Pilot Field Onshore Japan

As a part of a pilot CCUS project, we acquired walkaway DAS-VSP datasets in a depleted onshore oil field in Japan. Multiple fibre-optic cables were permanently installed in two deviated wells, CCUS-1 and CCUS-2, to enable detailed subsurface delineation and reservoir monitoring during CCUS operations. Despite logistical challenges that resulted in limited and irregular source coverage, the multi-fibre and multi-well walkaway DAS-VSP datasets provided significant insights into the subsurface contexts in the area of interest, aligning with well data and regional geology. We introduced simultaneous source acquisition to our DAS-VSP survey, which doubled operation productivity and delivered repeatable records comparable to conventional single-fleet acquisition. Data processing involved a joint imaging scheme using multi-well and multi-fibre DAS-VSP datasets, including velocity and anisotropy estimation. For further estimating detailed subsurface properties, elastic full waveform inversion was applied. These acquisition and processing strategies successfully handled the complexities inherent in the recorded datasets. This study demonstrates that DAS-VSP technology, when combined with modern acquisition and processing techniques, can significantly enhance the understanding of subsurface contexts in the area of interest. This integration offers a promising avenue for effectively managing production and injection activities, thereby advancing CCUS projects even under operational and budgetary constraints.