Project Description
Shales have recently attracted significant attention as a viable alternative or complementary source to conventional natural gas, as well as a promising medium for subsurface gas storage. Whether considered for gas production, storage, or the integration of both applications, a comprehensive understanding of the formation’s storage capacity is essential for successful and secure operation. In addition to their potential as storage formations, shales are widely recognized as effective sealing materials. The security of subsurface gas storage depends primarily on two interrelated properties: sealing integrity and sealing capacity. Sealing integrity is governed by the geomechanical properties and mechanical strength of the shale caprock. These properties may be altered by changes in the in-situ stress state resulting from gas or CO₂ injection, as well as by geochemical reactions between the injected fluids and the mineral constituents of the caprock. Such interactions may modify the mechanical properties of the shale and, under unfavorable conditions, promote deformation, fracture development, or caprock failure.In contrast, sealing capacity is largely controlled by capillary processes, particularly capillary entry pressure, which depends on the interfacial tension between the participating fluids and the wettability characteristics of the shale–fluid system. A detailed understanding of these multiphase flow properties is therefore essential for assessing the ability of shale formations to retain the injected gas over long timescales. Another important aspect of storage security is the quantification of permeability and diffusivity in shales which are controlled by multiple mechanisms that may vary with pressure, temperature, stress state, and fluid composition. Characterizing these transport properties is therefore critical for predicting gas migration, evaluating storage efficiency, and assessing the potential for leakage. An integrated understanding of these processes will contribute to more reliable assessments of the feasibility, efficiency, and long-term security of shale-based gas storage and CO₂ storage applications.
Funding
Young Scientist Funding Program – TU Clausthal