The Method
Hydraulic fracturing (HF) enhanced remediation is an in-situ method for remediation of contaminated environment. It uses high-pressure injection of reagents into the geological subsoil, thus enabling interaction between the reagent and contaminants even in places that cannot be reached using standard injection techniques. This concerns, in particular, impermeable geological layers where contamination is fixed in the long term, and from which it is slowly released into the surrounding environment. HF enhanced remediation disturbs the geological environment, thus making the contamination more accessible and allowing also its quicker removal.
The project will aim on development of complex technology of HF enhanced remediation. The technology will include the direct push set-up for HF as well as alternative remediation suspensions that will serve as HF material (fracturing fluid with proper proppant material and thickening agent) and remediation agent in one time.
The technology developed will provide a suitable technique for application of suspensions of solid remedial agents via direct push in to geologic environments which are difficult to access by conventional methods. For example the contaminated sites with low hydraulic permeability (low permeable soils with 10e-5 m/s Hydraulic Conductivity, e.g. clays, silts, silty/clayey fine grained sands) and/or heterogeneous geological conditions. The direct push delivery method is an effective way to deliver remediation agents to the contaminated zones. The main advantages of DP application are simple applicability, low cost and flexibility. One of the main limitations of this technology is its small effectivity in low permeable geological formations. There are a number of technologies to increase the permeability of geological formations which leads to a significant increase of the effectivity of injected remediation agents (conventional hydraulic fracturing, pneumatic fracturing, blasting). Although all these methods have promising potential to improve migration and distribution of injected remediation agents, application of these methods is time consuming and needs greater technical demands (cased wells, additional liquids: proppants, slurries, surfactants).
Combination of DP with HF is a suitable method for the application of alternative remediation agents that can serve as a fracturing material as well as remediation agent in one time. Formation of newly induced fractures will provide preferential flow paths for contaminated groundwater that will react with the fracturing material/remediation agent present in the fractures. Created fractures can also be used for subsequent injection of remedial agents, or the application of other remediation techniques. Two new fracturing materials/remediation agents are to be developed. And at least one of them will be prepared and tested in a pilot scale.
The first innovative remediation agent will be based on a mixture of different scale zero valent iron (ZVI) materials with carbon sources, nutrients and suitable thickening agents. This material should serve for remediation of chlorinated hydrocarbons via combination of in situ chemical reduction (ISCR) and enhanced reductive dechlorination (ERD). It was proven earlier that these methods are complementary and applying them together provides significant increase in their efficiency.
The second innovative remediation agent will be based on a mixture of bio-preparation (consisting of suitable bacteria, nutrients and surfactants), oxygen release compounds, slow release nutrients, proppants and suitable thickening agents. This material should serve for remediation of petroleum derived contaminants mainly via stimulation of their biodegradation, although in situ chemical oxidation (ISCO) can also contribute to their degradation.