Project funding: BGE -Bundesgesellschaft für Endlagerung, BMWi
Project duration: 2021-2025
Project partners: LEK, BGR
Influence of thermal maturity on petrophysical and coupled hydro-mechanical properties of low-permeability clay rocks - Field & laboratory scale
The MATURITY project is concerned with the exploration and evaluation of the long-term storage properties of clay-rich formations of different thermal maturity, which significantly affects rock strength, stiffness, porosity, swelling behavior, and hydraulic properties. In addition to depth and regional stress regimes, these properties influence the size and permeability of the excavation zone around a storage tunnel, the construction feasibility, and the self-sealing potential. In the context of various past research projects, basic aspects of the sealing behavior could be investigated, however, the diagenetic evolution, i.e., geological burial history, has not been taken into account in a systematic way so far.
The relationship between thermal maturity and compaction is known in principle, but to date, there are no systematic scientific studies on potential host rocks in Europe that allow quantitatively transfer between sites of higher and lower thermal maturities. Such investigations fail in particular because drill cores with different degrees of maturity would have to be obtained from various depths and thus very costly boreholes. The study area of the Hilsmulde south of Hanover, however, provides favorable conditions, since relevant clay rock formations are present at shallow depths and with varying degrees of thermal maturity.
The project includes both extensive in-situ and an extensive laboratory test program. A total of eight boreholes, up to 99 meters deep, will be drilled into the target clay shale formation of Pliensbachian age (191-183 Ma). After a borehole logging program, short-term hydraulic measurements will be conducted, which will then be supplemented by long-term measurements of hydraulic properties after borehole completion. On the laboratory scale, a series of partly complex petrophysical (LEK RWTH) as well as coupled hydromechanical tests (LIH RWTH) are performed. Among other characteristics, porosity and permeability, sorption capacity, stiffness and strength, poroelastic properties as well as swelling behavior of the claystone as a function of thermal maturity will be determined. Furthermore, stratigraphic analyses including micro- and macro-paleontological studies will enable the correlation of the boreholes (BGR).
Funding Agency and Project Partners