Coupled Geomechanics Processes

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Reliable decarbonized energy for Canada's future requires C-free sources and grid-scale storage. The two grid-scale storage options that can incorporate stochastic renewables (wind, solar) are pumped hydro and compressed air geostorage (CAES). I will develop thinly bedded salt cavern CAES in Canada, using long galleries to attain suitable volumes (e.g. 20x30x750 m). Provinces that can benefit from this approach, coincidentally, are those that have little pumped hydro potential (AB, SK, ON, NB, NS)! Novel ideas for consistent solutioning of thin-bed salt galleries are needed (horizontal wells , sliding sleeve and port methods), as well as analysis and design methods to optimize span choice and gallery array spacing. Roof rocks tend to be horizontally stratified non-salt rocks that can delaminate and slough when exposed to numerous pressurization cycles, and material behavior laws needed for this type of analysis have to be clarified and incorporated into the calculation procedure. The entry of air into partially delaminated roof strata, followed by the pressure loads during depressurization, leads to roof deterioration and potential large-scale sloughing which can impair cavern integrity if overburden conditions are unfavorable. Combining the viscous salt response with the elasto-plastic response of the roof through thousands of pressure cycles is a computationally demanding exercise. My students will also have some opportunity to work on a CAES pilot project in Ontario that will use an existing cavern at a 5-10 MW scale, incorporating heat stripping and recovery to achieve elevated efficiencies. Intermediate grade geothermal energy (IGGE) is accessible at depth (kms) throughout Canada, but without C-pricing and with cheap CH4, commercialization is challenging. To help make it commercial, we need more efficient horizontal drilling and hydraulic fracturing methods for low permeability igneous rocks, use of district heating and new binary cycle cogeneration, and coupled geomechanical models that can simulate the transfer of stresses and roughly predict seismic potential so that risks can be properly managed. I am working with a broad multiple-discipline engineering team to address integrated IGGE systems, focusing on 3D stress modeling of fractured systems undergoing convective and conductive heat transfer with circulating fluids (not necessarily water!). Stresses in such a system are massively shifted as the rock cools, and the flow system is very non-linear because during cooling, the joints open and even propagate, greatly changing flow behavior. Stress transfer means regions of high stress gradients (high shear stresses) are generated, and this is what triggers seismic events. If these can be modeled, it opens the door for their management through pressure, temperature and geometry factors, an exciting area to explore in research.