Abstract
As the global demand for effective carbon mitigation strategies intensifies, geological CO₂ storage has emerged as a key solution for supporting decarbonization efforts. However, reservoir heterogeneity and improper rock typing models often limit the accuracy of storage capacity predictions and long-term CO 2 injectivity assessments. This study addresses this gap by applying an integrated sedimentological, mineralogical and petrophysical rock typing analysis of the Farewell F Formation in the Maui Field, New Zealand with regional relevance for subsurface CO₂ storage. Maui Field in the Taranaki Basin hosts extensive, largely depleted gas-bearing reservoirs that represent promising candidates for long-term geological CO₂ storage. However, the storage potential of the Maui reservoir intervals remains insufficiently constrained. Farewell F consists mainly of mounded and onlapping wedge seismic facies corresponding to a prograding fluvio-deltaic sandstones. Mineralogically, Farewell F sandstone is classified as glauconitic, and argillaceous arkose arenite with heterogeneous porosity and permeability. Farewell F succession is subdivided into three distinct reservoir rock types (RRT 1 –RRT 3 ). RRT 1 demonstrates optimal storage properties with porosity exceeding 15%, permeability ranging from 100 to 500 mD, and favorable capillary behavior, while RRT 2 and RRT 3 show tighter pore networks and higher capillary entry pressures, functioning as internal baffles and potential mineral trapping zones. The present results reveal a vertically organized architecture, offering a self-contained and stratigraphically governed storage system. Additionally, the glauconitic composition of Farewell sandstones may offer additional CO 2 storage capacity through mineral trapping. These findings underscore the potential of the Farewell Formation to support both physical and geochemical trapping mechanisms.