oa Toward Reducing Uncertainty in Caprock Assessment: Insights from an Outcrop Analogue

Uncertainty in caprock assessment is one of the concerns in geologic carbon storage. It is especially caused in an area where an available geological dataset is lacking or limited. In such a case, a detailed database from a geological analogue can be utilized to reduce the uncertainty. This study investigated spatial changes in seal capacity of mudstones from onshore outcrops of the Pleistocene Kazusa Group near the Tokyo Bay area, to establish a geological analogue of caprock property in an active margin sedimentary basin. Seal capacity of the mudstones shows a distinct decrease landward in a relatively short distance from lower-slope to shelf-margin deposits, whares it is the highest and nearly constant in the basin-floor deposits. The findings can be utilized as a geological analogue for the caprock assessment in subsurface successions of this sedimentary basin as well as in other sedimentary basins with similar geological settings, such as high sedimentation rates and siliciclastic-dominated sedimentary successions formed in active margins.