There has been extensive interest in the role of faults as conduits and barriers to fluid flow in sedimentary basins. Much of the interest has been generated by the attempt to understand the role of faults in the migration and entrapment of hydrocarbons, the leakage of carbon dioxide during sequestration, and as conduits and barriers to flow in both shallow aquifer systems and in deep basinal settings. The project will study a fault as a conduit-barrier to fluid flow and groundwater salinization in a siliciclastic aquifer system under the context of a rigorous analysis of epistemic uncertainty. The Baton Rouge fault in Louisiana provides an ideal field area to investigate and test the concept of anisotropic fault permeability because of the large amount of historical and field data which exists for the area. In addition, the fault is playing an incompletely understood role in the salinization of a major municipal and industrial source of fresh water north of the fault. The project will test four hypotheses: (1) that the Bense and Person (2006) fault permeability method can be used to characterize the hydraulic properties of the fault, (2) that it is possible to determine whether vertical leakage up the fault plane from the deep saltwater aquifers or lateral leakage across the fault is the dominant cause of salinization, (3) that the Bayesian model averaging (BMA) is a valid method for quantifying salinity prediction uncertainties under a variety of sources of epistemic uncertainty in model parameters and model structure, and (4) that the proposed experimental designs are a valid approach in reducing epistemic uncertainties in salinization predictions. The project outcomes will significantly increase the understanding of the effectiveness of BMA-based experimental designs for reducing epistemic uncertainties in salinization models. The project will also improve the understanding of the Baton Rouge fault in groundwater salinization in a siliciclastic aquifer system.
The project provides a means for characterizing the permeability of faults in siliciclastic sequences and for developing techniques for quantifying and reducing uncertainties in the modeling of fluid flow and transport of contaminants across and along faults. The BMA analysis will advance the study of sources of uncertainty in such studies. In particular, the project will significantly advance techniques in the numerical modeling and uncertainty analysis of fluid flow and salinization of the Southern Hills aquifer system and will provide detailed knowledge of the subsurface geology, hydrogeology, and hydrogeochemistry of the region. Saltwater intrusion in the Southern Hills aquifer system is currently an urgent issue for the Louisiana state government, local water utility companies, and industry. The aquifer system currently provides high-quality groundwater that is utilized by the citizens of a four-parish area, but is in danger of being compromised by the introduction of saline waters. The results of project will help guide future salinization modeling and remediation efforts both in the Baton Rouge area and in other similar faulted and unconsolidated siliciclastic aquifer systems. One very practical benefit of the proposed research to society as a whole will be a better understanding of the processes and rates of salinization and the development of a means of remediation of the Southern Hills aquifer system in the greater Baton Rouge area.
