Simulated recovery of light, nonaqueous phase liquid from unconfined heterogeneous aquifers

• Published in: Ground water 1997-11, Vol.35 (6), p.938-947
• Main Authors: Waddill, D.W, Parker, J.C
• Format: Article
• Language: English
• Subjects: AGUAS SUBTERRANEAS; CAPA FREATICA; CORRIENTES SUBTERRANEAS; COURANT SOUTERRAIN; DEBIT; EAU SOUTERRAINE; FLOW RATE; GASTO; GROUNDWATER; GROUNDWATER EXTRACTION; GROUNDWATER FLOW; GROUNDWATER POLLUTION; GROUNDWATER TABLE; INFILTRACION; INFILTRATION; LOAM SOILS; MATHEMATICAL MODELS; MODELE DE SIMULATION; MODELE MATHEMATIQUE; MODELOS DE SIMULACION; MODELOS MATEMATICOS; MOUVEMENT DE L'EAU DANS LE SOL; MOVIMIENTO DEL AGUA EN EL SUELO; Multiphase flow; NAPPE SOUTERRAINE; Nonaqueous solvents; Oil spills; PETROLE; PETROLEO; PETROLEUM; POLLUTION DE L'EAU SOUTERRAINE; POLUCION DE AGUAS SUBTERRANEAS; POZOS; PROPIEDADES FISICO-QUIMICAS SUELO; PROPRIETE PHYSICOCHIMIQUE DU SOL; PUITS; PURIFICACION DEL AGUA; PURIFICATION DE L'EAU; SANDY SOILS; SATURATED FLOW; SATURATED HYDRAULIC CONDUCTIVITY; SIMULATION MODELS; SOIL CHEMICOPHYSICAL PROPERTIES; Soil permeability; SOIL WATER MOVEMENT; Soils; SOL SABLEUX; SOL SABLOLIMONEUX; SPATIAL VARIATION; SUELO ARENOSO; SUELO FRANCO; UNSATURATED FLOW; WATER PURIFICATION; WELLS
• ISSN: 0017-467X; 1745-6584
• DOI: 10.1111/j.1745-6584.1997.tb00165.x

A multiphase flow model (ARMOS) was used to evaluate the effects of subsurface heterogeneities on the recover of light, nonaqueous phase liquids (LNAPLs or simply "oil"). Stochastic inputs for the model included the saturated hydraulic conductivity (Ksw), van Genuchten alpha and n, the water saturation at field capacity (Sm), and the maximum residual oil saturations in the saturated (Sor) and the unsaturated zones (Sog). The turning bands method was used to generate stochastic soil parameters representing three hypothetical sandy loam soils. Oil recovery in the three heterogeneous cases was compared to an "equivalent" homogeneous soil with effective parameters computed as the geometric means of the stochastic parameters. Distributions of the free oil plumes were described over time using statistical and spatial moment analysis. Due to the smoothing effect of the flow process, the predicted well oil thickness (Ho) and free oil specific volume (Vof) were less variable than the input stochastic parameter ln (Ksw). However, Ho and Vof became more variable as free oil volume diminished and the oil distribution was controlled more by soil variability than gradients in the fluid levels. At the onset of oil recovery, the free oil area was greater in all three heterogeneous soils than the homogeneous soil. Nevertheless, soil heterogeneities did not greatly affect oil recovery or trapping in the saturated and unsaturated zones. Heterogeneities may have had a greater influence on oil recovery if a smaller spill had been studied or if the vertical dimension had been simulated explicitly. The results suggest that the geometric mean soil properties provide a useful estimate of the potential for oil recovery from oil spills that span a large number of correlation scales