3:30 PM - 3:45 PM
[MAG39-07] Development of solute transport modelling for multiple flow paths around the faults in mudstone
★Invited Papers
Keywords:Fault, Mudstone, Tracer migration test, Geological disposal, Horonobe URL
Fault zones have the potential to act as flow paths, and the characterization of solute transport in such zones of mudstone is important for developing the solute transport model required in the safety assessment for the geological disposal of radioactive waste [1-2]. In situ tracer tests are useful for characterizing the solute transport in rock mass, however few tracer tests have been conducted for fault zones of mudstones. Therefore, the methodologies for experimental and modelling on characterizing solute transport in such structures under in situ conditions have not been fully established. This study characterized the solute transport properties of fault-zone fractures in a mudstone by applying the modelling approach, which could be addressed heterogeneity in the fault-zone fractures.
Two boreholes (about 3 m in length) were horizontally drilled from the wall of the 350 m Gallery at the Horonobe Underground Research Labolatory (Horonobe URL). Dipole tests (single packers), one of the tracer-test techniques, for fault-zone fractures were conducted by two kinds of tracer-injection methods, one is pulse injection (uranine, HDO, I, Mo, Cs, Co, Sr, Ni, Eu) and the other is continuous injection (uranine Mo, Cs, Co, Eu), which was aiming for sorbing of the tracers on fractures surfaces. After this set of dipole tests, drill core samples were obtained from the surrounding rock and were employed to evaluate the distributions of fractures and tracer concentrations of Cs and Co sorbed on fractures surfaces. The flow paths contributing the tracer migration was estimated by geological 3D imaging.
Cs and Co are detected in some fractures distributing around the injection and pumping borehole, and it was presumed that at least two or three paths contribute the tracer migration. Breakthrough curves (BTCs) derived from dipole tests were simulated with GoldSim code [3] and the model assuming three flow paths individually consisted in the flow and stagnant domain. This modelling approach gave good agreement with the BTCs of uranine and Mo for pulse injection tests. However, there are some gaps of BTCs trend of uranine, Mo and Cs for continuous tests between in situ and simulation results. These gaps can be caused by larger tracer recovery in simulation results than tests results. We will continue to develope the more realistic model and optimal model parameters that can be appropriately treated to uncertainty of transport paths.
This study was carried out as a part of “The project for validating assessment methodology in geological disposal system” funded by the Ministry of Economy, Trade, and Industry of Japan. (Grant Number: JPJ007597)
Refereneces
[1] Mazurek et al., J. Cont. Hydr 35, 1-17 (1998)
[2] E. Ishii, JGR. 120, 2220-2241 (2015).
[3] GoldSim Technology Group, 2010. GoldSim Version 10.1.
Two boreholes (about 3 m in length) were horizontally drilled from the wall of the 350 m Gallery at the Horonobe Underground Research Labolatory (Horonobe URL). Dipole tests (single packers), one of the tracer-test techniques, for fault-zone fractures were conducted by two kinds of tracer-injection methods, one is pulse injection (uranine, HDO, I, Mo, Cs, Co, Sr, Ni, Eu) and the other is continuous injection (uranine Mo, Cs, Co, Eu), which was aiming for sorbing of the tracers on fractures surfaces. After this set of dipole tests, drill core samples were obtained from the surrounding rock and were employed to evaluate the distributions of fractures and tracer concentrations of Cs and Co sorbed on fractures surfaces. The flow paths contributing the tracer migration was estimated by geological 3D imaging.
Cs and Co are detected in some fractures distributing around the injection and pumping borehole, and it was presumed that at least two or three paths contribute the tracer migration. Breakthrough curves (BTCs) derived from dipole tests were simulated with GoldSim code [3] and the model assuming three flow paths individually consisted in the flow and stagnant domain. This modelling approach gave good agreement with the BTCs of uranine and Mo for pulse injection tests. However, there are some gaps of BTCs trend of uranine, Mo and Cs for continuous tests between in situ and simulation results. These gaps can be caused by larger tracer recovery in simulation results than tests results. We will continue to develope the more realistic model and optimal model parameters that can be appropriately treated to uncertainty of transport paths.
This study was carried out as a part of “The project for validating assessment methodology in geological disposal system” funded by the Ministry of Economy, Trade, and Industry of Japan. (Grant Number: JPJ007597)
Refereneces
[1] Mazurek et al., J. Cont. Hydr 35, 1-17 (1998)
[2] E. Ishii, JGR. 120, 2220-2241 (2015).
[3] GoldSim Technology Group, 2010. GoldSim Version 10.1.