Modeling of transport contaminants movement in a geothermal reinjection system

• Main Author: Servino, Andrea E.
• Format: text
• Language: English
• Published: Animo Repository 1995
• Subjects: Wastewater; Fluid dynamics; Mathematical models; Waste disposal in the ground; Ground water flow; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/1667
• Institution: De La Salle University

A simulation technique is developed to assess the impact of shallow reinjection of geothermal wastewater at Palinpinon field to the surrounding groundwater resources. The physical model assumes single fracture connecting the reinjection and the groundwater wells. Using the analytical solutions of the resulting coupled dispersion-advection equation for the fracture flow and the diffusion equation for the flow into the rock matrix, relative concentrations of chloride at various points within the fracture and at observation points 4000 and 2000 meters away are calculated. For porosites of 0.03 to 0.1 which is typical for welded tuffs and clay alteration products which are the dominant rocks in the area, matix diffusion was found to be an efficient retardation mechanism for the dispersion of the waste fluids.Boron dispersion was also modeled by taking into account its probable adsorption into clays. Using reasonable estimates for the retardation coefficients for boron, adsorption may delay its breakthrough by up to 100 days. A general program coded in FORTRAN 77 has also been developed to evaluate the general transient solutions of the mass transport equations in fractured porous media. The method employed in the evaluation is the Gauss-Legendre quadrature. The technique provides insights into the gross behavior of reinjected fluids by putting constraints on breakthrough times, relative concentrations of the contaminant along the fracture and within the matrix and matrix retention of contaminants.