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A theory that will enhance our understanding of natural hazards, C02 storage monitoring and better exploit subsurface resources like oil and gas has been proposed by an academic at Heriot-Watt University.
Professor Gary Couples is developing a new model that will change how activity in the earth's subsurface is monitored, and how seismic methods are used to create images of oil and gas reservoirs.
For the first time, the new conceptual and numerical model will account for the real, detailed textures of porous rocks which will impact on how the subsurface is monitored and utilised.
Professor Couples is at the forefront of digital-rock research. Through this highly esteemed award from the Royal Society, he is seeking to transform our understanding of wave motion in porous media and re-write knowledge of the subsurface.
While much is already known about how sound waves propagate through gases, liquids and solids, this is not true for porous solid geomaterials like rocks and soils. Rocks are riddled with connected pores that are filled with water, oil or a gas (such as methane, CO2, or air near the land surface). In porous materials, sound waves create complex interactions between the solids and the pore-filling fluids. It is these micro-scale interactions that will form the basis for the new theory.
The research, which is being funded by the prestigious Theo Murphy Blue Skies Award from the Royal Society, will improve the way we use natural and induced sound waves to extract key information about these geomaterials.
Professor Gary Couples, who leads the geomaterials research group in the Institute of Petroleum Engineering, explains: “We are using this award to re-think our existing ideas about how we monitor and exploit both hazards and resources in the earth's subsurface and how we can gain more value from acoustic data.
“During a volcanic eruption, for example, the mostly molten rock (magma) that is pooled at depth becomes more solid as it moves towards the surface. This also changes its acoustic signature. Seismic investigations use both artificial and natural acoustic data as part of the current eruption-monitoring process, but these models can be improved by understanding how the solid/liquid components jointly affect the sound waves.
“As we increase our reliance on CO2 capture and its subsurface storage, this new model will be important in determining if waste has remained where it was injected, or if it has moved to places that could pose a threat to society.”
“This new theory will improve the quantification and therefore the picture of where injected fluids are moving beneath the subsurface.
“It will also have wide applications in subsurface exploitation, such as the extraction of fossil fuels. Seismic surveys are currently one of the largest geoscience expense costs. There is a continuous effort across all of the industry to improve the cost-effectiveness of operations, and this new theory will play a key role in gaining more value from these expensive surveys.
“Modern seismic methods are often used to derive quantitative estimates of the changing proportions of pore fluids in fossil fuel reservoirs. These pictures play a key role in supporting engineers to make decisions about the operational practices applied to the limited set of wells that reach each reservoir. Our new model will cause a step-change in the precision of the estimates that can be derived, and will have a substantial impact on the overall effectiveness of resource exploitation.”
Professor Dorrik Stow, director of the Institute of Petroleum Engineering at Heriot-Watt University, said: “Professor Couples is at the forefront of digital-rock research. Through this highly esteemed award from the Royal Society, he is seeking to transform our understanding of wave motion in porous media and re-write knowledge of the subsurface.”