Product Summary

INCORPORATING CAPILLARY ENTRY PRESSURE MEASUREMENTS INTO EVALUATIONS OF STORAGE PERMANENCE FOR PERMITTING CLASS VI INJECTION WELLS

The injection of carbon dioxide (CO₂) for permanent geologic storage requires the approval of a Class VI permit application by state or federal regulatory authorities. Among the permitting requirements, data must be provided on the capillary entry pressure of the injection and confining zones. In geologic media, capillary entry pressure is defined as the lowest pressure required to begin to displace in situ formation fluids (the wetting phase) during the injection of a non-wetting-phase fluid (CO₂). For confining zones that immediately overly the injection zone (hereafter "cap rock"), capillary entry pressure provides an indication of the maximum upward CO₂ force that can be held within the injection zone before CO₂ starts to permeate the confining zone. This document i) provides an overview of capillary entry pressure, ii) summarizes laboratory methods for determining capillary entry pressure, and iii) provides examples and interpretations of capillary entry pressure data for evaluating cap rocks and storage permanence for permitting Class VI injection wells.