applications


conditions and meshes for the model, the analysis is ready to run. Extracting measurements such as efficiency and energy flux can be determined during simulation, or via post-processing aſter simulation.’ When investigating a potential fracking site,


geophysicists characterise the underground formations by detecting and analysing acoustic waves from seismic activity, such as earthquakes. While the acoustic waves can travel long distances, they do not provide the level of detail required about the formation’s properties, or track the water (known as pore water) travelling through the formation. Research from the Colorado School of Mines suggests that electromagnetic disturbances associated with seismic activities could provide this missing information. However, electromagnetic waves do not propagate as far as acoustic waves, so theoretical models and lab experiments complemented by multiphysics simulations can identify and track pore water.


SEISMIC


INTERPRETATION IS OFTEN THE FIRST SIMULATION THAT TAKES PLACE IN GEOTHERMAL OIL OR GAS EXPLORATION


Te team at the Colorado School of Mines


simulators are able to access tremendous amounts of compute when they need them (as long as the input data can be provided to the data centre economically),’ he added. Tis capability to link simulations with the


computational power required to investigate potential geothermal-rich sites, and then use further modelling to optimise the extraction of these resources, has opened the door to more cost and time effective geothermal energy production in the field.


Hydraulic fracturing Hydraulic fracturing, more commonly known as fracking, is a method to increase the production of oil and gas from certain types of geological structures. Te process involves drilling down into the rock and injecting a high-pressure water,


www.scientific-computing.com l


sand and chemical mixture to release the oil or gas held inside shale rock. While this process is easy to describe, the


mechanics involved are more complicated. Andy Cai, applications engineer at Comsol, explained: ‘Given the multiphysics nature of fracturing involved when there is fluid flow through formations within the earth, many companies and researchers have turned to multiphysics simulation to study this phenomenon. Tere is a need to couple fluid flow, heat transfer, structure mechanics, as well as acoustics.’ Simulation oſten serves as the basis of analysis


in this area because the physical structures involved are hundreds or thousands of metres under the earth’s surface, making them difficult to test in the real world environment. Cai said: ‘Aſter setting up the physics properties, boundary


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created a system to locate fracking fluids by investigating these electromagnetic disturbances. Tey simulated fracking events and produced synthetic seismograms and electrograms by linking COMSOL Multiphysics and MATLAB. Te research involved a physical experiment in which saline water was pumped into a hydraulically-fractured porous cement cube under high pressure. Te underlying physics, such as the


hydromechanical equations, were well-defined in the soſtware, so time-consuming calculations were not necessary. Te team could iterate and develop a way to track underground fluid flows to better map and understand subsurface formations and dynamics. An obvious application here is to track the fracking fluids used in this oil and gas extraction technique. Not only does a well-benchmarked numerical


model such as this bring down the upfront cost of site planning, development, and monitoring, you can also run the tests on a computer in a much shorter time scale than in an on-site experiment, according to Cai, who added: ‘Te results of the simulation are also a great resource for marketing and collaboration, as one can compare all


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