Enhanced Amendment Delivery to Low Permeability Zones for Chlorinated Solvent Source Area Bioremediation.

摘要

The shear-thinning technology is designed to enhance delivery of remedial amendments to lowpermeability (low-k) zones for which treatment is typically limited when standard amendment delivery processes are utilized. Improved distribution of injected fluids is achieved by exploiting the rheological properties of shear-thinning fluids (STFs) during injection and transport within a formation, such as cross-flow from high-permeability (high-k) to low-k zones. The overall goal of this project was to demonstrate and validate the use of shear-thinning delivery fluid for enhanced delivery of bioremediation amendments at a chlorinated solvent-impacted site and to develop guidance for its use at other sites. The term shear-thinning is applied to fluids to describe their dynamic viscosity-reducing behavior when shear rates are increased. Shear-thinning fluids are non-Newtonian, meaning that their viscosities exhibit a temporary drop when the applied shear rate is increased. A viscositymodifying shear force can be applied using methods as simple as mixing or shaking of the solution, or in the context of subsurface delivery by injecting the fluid through a well screen and into porous media. For the enhanced amendments delivery process, a non-toxic biodegradable polymer, such as xanthan gum, is added to the injection solution to form a non- Newtonian fluid with shear-thinning properties. The shear-thinning behavior causes a more significant viscosity reduction to the fluid flowing through the lower-k zones relative to the viscosity reduction of the fluid flowing in higher permeable zones, i.e., the fluid mobility in the higher-k zone is controlled. Therefore, the preferential flow through the more permeable zones is significantly reduced while the flow into the lower-k zone is increased.