Experimental study about estimating the permeability and storativity properties of CO2 in low permeable rocks under the CO2 injection by flow-pump method.

Recently, it is generally believed that the increase of atmospheric carbon dioxide (CO₂) emission has become a major contributing factor of a global warming. Carbon dioxide capture and storage (CCS) is an emerging technology and considered as the promising method to reduce greenhouse gas emissions in the atmosphere. Generally, CCS is intended to apply in oil or natural gas reservoir layers with overlying cap rock. However, in Japan, few proper sites are available for CCS. Therefore, low-permeable rock mass without cap rock is suggested as alternative option. It is required to clarify behavior of CO₂ in rock for longitudinal and stable storage of CO₂.

In order to clarify the properties of permeability and storativity of low permeable rocks, Ainoura sandstone, saturated with water injected with a constant and appropriate flow rate of supercritical CO₂, flow pump permeability test under the condition of temperature and pressure of in-situ CO₂ reservoir has been conducted. In this experiment, the differential pressure between both ends of specimen changed in 4 stages and finally in stable condition. Furthermore, relative permeability of water and CO₂, and specific storage of specimen during CO₂ injection has been calculated with theoretical analysis of flow pump permeability test for two phase flow. Using the results of the experiment, 3D core-scale flow-simulation by using TOUGH2 (ECO2N module) has been conducted due to confirm the flow of fluid and CO₂ distribution in the specimen. To compare the results of simulation and experimental results, the permeability and storativity properties of carbon dioxide in low permeable rock has been estimated. As a result, low permeable rocks could become an effective storage of supercritical CO₂.