1. Finite element transport modeling of biodegradable contaminant in heterogeneous porous media, and 2. Geostatistical methods for the study of pressure compartments: A case study in the Hilight oil field, Powder River Basin, Wyoming

1. This study presents a two-dimensional numerical solute transport model for the investigation of biodegradable contaminant transport and biomass growth in saturated porous media. The transport of contaminants and added electron acceptors are assumed to be governed by advection-dispersion equations. The dual-Monod expressions were used to describe the rates of microbial growth and the consumption of organic contaminants. An operator-splitting method was selected as a solution algorithm. This algorithm, which separates the advection-dispersion equation from the bioreaction expression, involves a two-step procedure: (1) Solve one time step of the advection-dispersion equations for contaminants and electron acceptors using appropriate numerical techniques, and (2) Solve the dual-Monod equation for the microbial growth and subsequent utilization of organic contaminants. The Galerkin finite element method was chosen for the solution of advection-dispersion equations. The quadratic basis functions are used as the weighting functions in the formulation of the weighted residual equations. The fourth-order Runge-Kutta method was used to solve the microbial reaction equations. The steady-state groundwater flow equation was also solved using the Galerkin finite element method, and the groundwater flow velocity was estimated using Darcy's Law. The results of this numerical model were very close to the analytical results for a simplified problem. Conditional simulation method was used to characterize the spatial variation of aquifer properties, and the impacts of hydraulic conductivity distribution on groundwater flow and transport in subsurface were simulated using the developed numerical models. This model is able to evaluate the designs and performance of injection well networks for in situ bioremediation systems, and an optimal in situ bioremediation system in heterogeneous aquifers can be obtained.;2. This study introduces the variogram method for analyzing the geometry of pressure compartments. Pressure and hydraulic head data from 192 wells in the Hilight oil field, Powder River Basin, Wyoming, were used in this study. Variograms were calculated for various directions. Results indicate that hydraulic head and pressure are spatially correlated, especially in directions parallel to the axes of elongation of compartment cells. The average pressure compartment was estimated via the variogram method to be an ellipse with major and minor axes of 5.3 and 2.7 miles. The major axis trends 15...