Energy and the Subsurface: Modeling Hydraulic Fracturing and Geological Carbon Storage

Abstract

Hydraulic fracturing, shale gas, and geological carbon storage are key topics involving subsurface fluid flow that relate to the energy and climate challenge. In this dissertation, I advance the current understanding of these topics using numerical modeling of porous media fluid flow, the development new numerical models, and economic and policy analysis, all supported by a comprehensive collation of data.

In Chapter 2, I investigate the fate of hydraulic fracturing fluids injected into shale formations through numerical modeling of two-phase water and gas flow. My simulations match water and gas production data closely and show that most injected water is imbibed into the shale and retained there by capillary forces. Capillary pressure is a key factor governing the movement of water in shales, and data show that capillary pressure in shales is strongly hysteretic. Therefore, in Chapter 3, I develop a modified numerical capillary pressure hysteresis model that is robust and computationally efficient for simulating flows in shale formations compared with existing models that perform poorly under equivalent conditions.

In Chapter 4, I consider geological carbon storage in shale gas formations. I develop a numerical model of single-phase, two-component flow of methane and carbon dioxide in shales, including adsorption effects, in order to assess geological carbon storage capacity. Application of the model to three major shale gas regions shows that carbon dioxide can only be injected at low rates into individual wells, that individual well capacity is relatively small, and, therefore, that large-scale carbon storage in shales is unlikely to be economically favorable.

Finally, in Chapter 5, I broaden the scope beyond modeling shale gas formations by conducting an integrated engineering, economic, and policy analysis of potential carbon capture, utilization, and storage deployment in the United States as a result of new tax credits enacted in February 2018. I focus on the pipeline infrastructure required to enable the system. I find that a large-scale system capturing carbon dioxide from ethanol biorefineries in the Midwest and delivering it for use in enhanced oil recovery in the Permian Basin, Texas, could be feasible with low-cost government financing of the pipeline network.