Fracture and Transport Problems for Inhomogeneous Brittle Materials

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NONTECHNICAL SUMMARYThis award supports theoretical and computational research, and education that brings theoretical materials research to bear on understanding the physical processes that lead to materials fracture under extreme conditions in the context of hydrofracturing and to contribute to understanding the production of gas and oil.The technology called hydrofracturing or fracking has been used for decades, but in its current form it is just over ten years old. The impact of this technological development upon the US has been enormous. The benefit to the US economy in the last 5 years has been well over a trillion dollars, and the US has become the world's largest oil and gas producer.Producing oil and gas from shales appears to be paradoxical. Shales are some of the most impermeable materials known. Nothing should flow through them. So how can they produce revolutionary quantities of gas and oil? The answer is that the hydrofracture process stimulates them, creating networks of cracks, and these cracks must be distributed with fine enough spacing to make production possible.This project will study the physical processes leading to the network of cracks. Part of the study will concern how the cracks form. Part of the study will concern how the network of cracks can be understood using clues from the time history of gas produced at the surface. And part of the study will concern how oil and water flow through very nonuniform rock.To obtain broad impacts from this work, the PI will investigate ways to make the research actionable by examining factors that lead to the most productive wells, and developing methods to predict performance of wells, and gas and oil fields. The PI will also examine the implications of these findings for transitions to renewable energy sources. The PI has numerous opportunities to integrate the research with education and outreach. The PI oversees a network of university programs that prepares over 600 high school STEM teachers a year, oversees summer STEM camps serving hundreds of youth from under-represented groups, and teaches a dual-enrollment physics class to over 5000 high school students.TECHNICAL SUMMARYThis award supports theoretical and computational research, and education to bear on understanding the physical processes that lead to materials fracture under extreme conditions in the context of hydrofracturing. The shale revolution, which has propelled the US to the top of gas and oil-producing countries, was built on largely empirical findings. The shale layers from which gas and oil are produced have nanodarcy permeability, making it seem impossible to produce economical quantities of hydrocarbons. The resolution of this problem is that the hydrofracture stimulation process creates a fracture network where the fractures have sufficient density to make transport possible.The PI will investigate three areas in particular. First, he will use a discrete element model coupling rock and fluid to study the hydrofracture process, and study how fluid pressure leads to the creation of a fracture network. Second, he will make use of Green's function techniques familiar from the electron theory of solids to study the diffusion of gas to complex networks, and thereby examine the connection between shape of the network and the time history of production. Finally, he will use fluid finite element modeling to study the flow of oil and water through highly inhomogeneous geological environments.To obtain broad impacts from this work, the PI will investigate ways to make the research actionable by examining factors that lead to the most productive wells, and developing methods to predict performance of wells and gas and oil fields. The PI will also examine the implications of these findings for transitions to renewable energy sources. The PI has numerous opportunities to integrate the research with education and outreach. The PI oversees a network of university programs that prepares over 600 high school STEM teachers a year, oversees summer STEM camps serving hundreds of youth from under-represented groups, and teaches a dual-enrollment physics class to over 5000 high school students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.