Qinjun Kang

AbstractShale gas is an unconventional fossil energy resource that is already having a profound impact on US energy independence and is projected to last for at least 100 years. Production of methane and other hydrocarbons from low permeability shale involves hydrofracturing of rock, establishing fracture connectivity, and multiphase fluid-flow and reaction processes all of which are poorly understood. The result is inefficient extraction with many environmental concerns. This work uses innovative high-pressure microfluidic and triaxial core flood experiments on shale to explore fracture-permeability relations and the extraction of hydrocarbon. These data are integrated with simulations including lattice Boltzmann modeling of pore-scale processes, finiteelement/ discrete element models of fracture development in the near-well environment, and discrete-fracture network modeling of the reservoir. The ultimate goal is to make the necessary measurements to develop models that can be used to determine the reservoir operating conditions necessary to gain a degree of control over fracture generation and fluid flow.1. INTRODUCTIONShale gas is an unconventional fossil energy resource that is already having a profound impact on US energy sector, with reserves projected to last for nearly 100 years [1]. The increased availability of shale gas (i.e., methane), which produces 50% less CO2 than coal, is primarily responsible for US emissions in 2011 dropping to their lowest levels in 20 years [2]. Production of methane and other hydrocarbons from low permeability shale involves hydrofracturing of rock, establishing fracture connectivity, and multiphase fluid-flow and reaction processes, all of which are poorly understood. The result is inefficient extraction with many environmental concerns [3,4]. Industry is motivated to reduce the 70 to 140 billion gallon per year water demand because there are droughts in the west, a lack of deep injection wells in the east, and possible forthcoming regulations [3]. Our goal is to use unique Los Alamos National Laboratory (LANL) microfluidic and triaxial core flood experiments integrated with stateof- the-art numerical simulation to reveal the fundamental dynamics of fracture-fluid interactions to transform fracking from an ad hoc tool to a safe and predictable approach based on solid scientific understanding. The goal is to develop CO2-based fracturing fluids and fracturing techniques to enhance production, reduce waste-water, while simultaneously sequestering CO2 [4].

Summary Understanding hydrocarbon flow, migration and phase behavior in nanoporous media is critical for the sustainability and continued growth of unconventional oil/gas production. In this work, we combine experimental characterization and observations, particularly using small-angle neutron scattering, with pore-scale modeling using lattice Boltzmann method, to examine the fluid behavior and fluid-solid interactions in nanopores at reservoir pressure- temperature conditions. Integration between laboratory measurements and numerical calculations will facilitate our understanding of nanoscale fluid behavior with the ultimate goal of developing better production strategies for unconventional reservoirs.

The multiphysiochemical transport in electroosmosis of dilute electrolyte solutions (<1mM) through microporous media with granular random structures has been modeled in this work by our numerical framework consisting of three steps. First, the three-dimensional microstructures of porous media are reproduced by a random generation-growth method. Then the effects of chemical adsorption and electrical dissociation at the solid-liquid interfaces are considered to determine the electrical boundary conditions, which vary with the ionic concentration, the pH, and the temperature. Finally the nonlinear governing equations for the electrokinetic transport are solved by a highly efficient lattice Poisson-Boltzmann algorithm. The simulation results indicate that the electroosmotic permeability through the granular microporous media increases monotonically with the porosity, the ionic concentration, the pH and the environmental temperature. When the surface electric potential is higher than 50 mV, the permeability increases with the electric potential exponentially. The electroosmotic permeability increases with the pH exponentially, but with the temperature linearly. The present modeling results may improve our understanding of hydrodynamic and electrokinetic transport in geophysical systems, and help guide the design of porous electrodes in micro energy systems.

High specific surface area structures are used in a variety of applications including production of highly sensitive biosensors, fabrication of separation membranes, manufacturing of high throughput catalytic microreactors, and development of efficient electrodes for batteries and fuel cells. In many electrochemical applications (i.e. sensors and batteries) it's also critical to have good conductive properties of the fabricated high surface area structures. For energy harvesting technologies such as batteries and fuel cells, careful design of surface-to-volume ratio of the electrode surface is important, because while high specific surface area facilitates electrochemical reaction rates, it also increases overall electrode resistance. Thus, it is desirable to construct electrodes with a range of hierarchical features (for example with fractal structures). We invented a novel fabrication technology for creating three-dimensional conductive high surface area structures based on the deposition and subsequent processing of the electroactive polymers (EAP). The proposed fabrication technique is capable of fast and inexpensive production of high surface area structures with the designed geometry, porosity, and conductivity.