Experience from 3D DAS-VSP acquisition and imaging for assessment of CCS applications

Abstract

Summary In-well Distributed Acoustic Sensing (DAS) has been proposed as a potential cost-effective solution for near-well monitoring of early phase CO2 plume migration. We report here from an experiment at the Johan Sverdrup oil field where in-well DAS-VSP was acquired in a water injection well to prepare for potential future CCS applications. The DAS-VSP was acquired during a regular seismic survey with limited additional acquisition costs both with and without active injection. Robust denoising methods on data acquired during injection periods adds operational flexibility to timing and planning of acquisitions. 3D imaging including down-going multiple reflection increased the imaging area and the potential of using DAS-VSP for CO2 plume monitoring purposes. Initial assessment of repeatability was achieved with denoised signals. However, accurate synchronization of clocks from the source and DAS acquisition system will be essential to monitor small velocity changes due to CO2 injection.