Injection risk assessment for intra‐formational seal geological model in a carbon sequestration application in Taiwan

As a deep saline aquifer, the Tai‐hsi Foreland Basin in western Taiwan is regarded as an excellent locality to sequester the huge carbon emission from domestic coal‐fired power plants. Existing geological data show that an intra‐formational seal capability characterized by multilayered shale baffles can act as the primary or ultimate cap system. In this study, the relevant ranges of rock parameter of porosity (20∼35%) and permeability (0.0001∼1300 mD), respectively, for the storage layers (sandstone) and seals (shale) have been selected according to large amount of laboratory core test from a nearby pioneering 3000 m drilling and sampling within the southern flank of the Tai‐hsi Basin. Comprehensive geological models considering both homogeneous and heterogeneous cases, and a typical plume migration scenario under a single‐well injection were simulated under a 20‐year continuous injection (1 MtCO 2 per year) followed by post‐injection monitoring up to 1000 years. Corresponding 2D maximum horizontal migration distances (MHMD) of CO 2 plume in the storage reservoir were calculated with respect to a homogeneous reservoir model and its heterogeneous counterparts. In addition, the induced pressures at critical monitoring points were also evaluated and compared. As a consequence, the ubiquitous shale baffles of intra‐formational seal in a heterogeneous saline aquifers were proven to be a successful trapping mechanism controlling the migration distances of lateral and upward movement. Furthermore, safe carbon storage operation within Tai‐hsi Basin with formation depth range about 2135 to 2450 mRT can be ensured by checking statistically the calculated maximum MHMD and the induced pressure magnitude. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.