Multiscale Investigation Of Fluid Transport In Gas Shales

This thesis focuses on developing an improved understanding of fluid flow in gas shales. The problem is studied at multiple scales, and using a variety of approaches spanning several disciplines. In Chapter 2, Adsorption of Methane and Carbon Dioxide on Gas Shale and Pure Mineral Samples, we present measurements of methane and carbon dioxide adsorption isotherms at 40°C on gas shale samples from the Barnett, Eagle Ford, Marcellus and Montney reservoirs. Carbon dioxide isotherms were included to assess its potential for preferential adsorption, with implications for its use as a fracturing fluid and/or storage in depleted shale reservoirs. To better understand how the individual mineral constituents that comprise shales contribute to adsorption, measurements were made on samples of pure carbon, illite and kaolinite as well. The resultant volumetric swelling strain was also measured as a function of pressure/adsorption. In Chapter 3, Experimental Investigation of Matrix Permeability of Gas Shales, we present laboratory experiments examining the effects of confining stress and pore pressure on permeability. Experiments were carried out on intact core samples from the Barnett, Eagle Ford, Marcellus and Montney shale reservoirs. The methodology we used to measure permeability allows us to separate the reduction of permeability with depletion (due to the resultant increase in effective confining stress) and the increase in permeability associated with Knudsen diffusion and molecular slippage (also known as Klinkenberg) effects at very low pore pressure. By separating these effects, we are able to estimate the relative contribution of both Darcy and diffusive fluxes to total flow in depleted reservoirs. Our data show that the effective permeability of the rock is significantly enhanced at very low pore pressures (