2015 - Physique des roches - Master 2 - Wang Fei
Diplôme préparé : Master 2
Sujet de stage : Permeability anisotropy of the Triassic sediments at Soultz/Rittershoffen : a combined field and laboratory study
Tuteur : M.Heap
Abstract : The Soultz-sous-Forets(Upper Rhine Graben) is a particularly interesting region for the geothermal energy. Many research about the geothermal reservoir in this place have been published. The lower Trias Buntsandstein sandstone over the granite basement are widespread distributed in this region. As a potential geothermal reservoir, these Triassic sediments have some properties are as yet undetermined. For example, the effect of fracture healing in the reservoir in permeability. Here we present an experimental study about the gas permeability and porosity of the Buntsandstein sandstone combined with a Scanning Electron Microscopy (SEM) analysis to characterize the micro-structure of the healed fractures and the precipitated minerals. We made 39 cylindrical cores and 5 representative thin sections from the borehole samples in ESP-1, including the intact samples and the samples have the healed fractures. The results illustrated that the permeability of the samples is much lower than we thought and the healed fracture can play both as a conduit or a barriers in our samples. Compare with the intact samples, healed fracture obviously modified the permeability characters. The SEM analysis confirmed our experience data and suggests that the clay filling in the pores and void space in the fracture can explain the low permeability. As a result, the permeability anisotropy of Buntsandstein sandstone may change over time. The healed fracture may influence the local fluid circulation. To better understand the geothermal convection system in this area, a numerical model with the healed fractures’ permeability evolution may be very useful.
2 juillet 2015