Application of a new NMR well logging porosity/permeability calibration to the Arbuckle injection zone of the Wellington CO2 demonstration site

Carbonate reservoirs hold significant potential for carbon capture and storage (CCS) projects. Target formations for carbon dioxide (CO2) storage must have suitable porosity and permeability properties to ensure adequate long term storage. Of these, permeability can be difficult to estimate in carbonate reservoirs due to the orders of magnitude differences in pore sizes, and the complex geometry of existing pore networks or those developed due to reactive CO2 acidified fluids. One of the primary methods for assessing porosity and permeability of reservoirs is down well nuclear magnetic resonance (NMR) logging tools. Our work has been focused on constraining new porosity/permeability relationships in carbonate rocks using micro X-ray computed tomography (µXRCT) to characterize the pore networks to inform on the observed NMR relaxation behavior. This effort has shown that standard NMR methodologies can produce permeability estimates for carbonate rocks that differ by several orders of magnitude from directly measured values. Our new calibrations have rectified these discrepancies by identifying and accounting for the main properties of these rocks that contribute the measured NMR relaxation properties. Properties such as mineralogy, Fe and Mn content, pore geometry, and pore network tortuosity all contribute to the relaxation behavior observed by NMR and are now accomodated in this new calibration procedure. This work has led to new understanding of the properties of these rock types that control the permeability measured by NMR well logging. In this presentation, we apply the results of a lab measured calibration of porosity and permeability to a high resolution NMR well log produced for the Arbucke injection zone of the Wellington CO2 demonstration sites. This application illustrates the applicability of this new calibration method for carbonate reservoirs and helps advance our understanding of the permeability and porosity relationships in these complex rock types. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.