Evaluating Capillary Threshold pressure in Caprock for Carbon Storage

Abstract

Increased CO₂ emissions have resulted in extreme climatic variations and as the forecast is that the global temperature will hit its highest-ever level in the next five years. This comes at a time when there is an urgent need for effective and smooth means of reducing greenhouse gas emissions. Geological Sequestration of Carbon (GCS) is a new alternative: the effective and safe storage of CO₂ underground. The most critical part of the process is the leakage assessment and geological formation safety as a long-term sink of CO₂. Caprock is important in this process as an efficient long-time sequester for CO₂, as it is more permeable to CO₂ than geological reservoirs. Of all the other processes involved in trapping, the most effective in the immediate phase after the injection of CO₂ is capillary trapping. The CO₂ remains stored under the caprock until the critical pressure that initiates movement is achieved. Traditional methods, such as mercury intrusion porosimetry and core flooding experiments, do not tend to be replicated correctly in situ and often complicate the process. Measurements made in such a manner usually overestimate threshold pressures for one of many reasons, be it late flow signal recognition in the low permeability of caprocks or incompletely saturated cores. For these purposes, in-situ-type novel equipment was developed for easy and direct capillary pressure measurement, core saturation, and effortless reproduction of in-situ conditions at higher pressures. This new technique measures the pressure in the outflow directly, so the values of threshold pressure it gives are very exact.