Application of Oil and Gas Technology for Containment of Liquid Contaminants
Authors: Aminian K. , Ameri S. , Bugarski A. , Molnar D. , Overbey W.K. 
Published: December 2007

An innovative barrier technology for preventing the movement of liquid contaminants toward groundwater using commercially available oil and gas technologies and equipments, is discussed in this paper. This technology provides many advantages including non-physical confinement, active monitoring and leak detection, emergency response and rapid deployment capability, and high potential for integration with other remediation technologies.

The concept involves the circulation of dry air through a targeted subsurface zone beneath the zone of contamination to creates a dry zone. Drying of the soil increases its liquid storage capacity so the soil will tend to retain rather than transmit the liquids. If the soil water saturation is lowered below the critical saturation for liquids to flow, it will act as a barrier to liquid contaminants. This type barrier can be installed by a system of air injection and production wells. The air injection process, could in principal be coupled with a vacuum extraction system to recover soil vapors, which would then provide a remediation process if volatile organic compounds were present.

A series of experiments have been designed and conducted to evaluate the feasibility of the concept. Sand-packs have been utilized to study the drying process in porous media. The experimental results have established the necessary baseline information and provided useful information relative to feasibility of the concept.

Introduction

Many contaminated subsurface sites can not be economically remediated because of technological or economical limitations. In such cases, containment becomes the primary technology for environmental protection. Therefore, confinement technologies are needed to retard or prevent the advancement of contaminant plumes to protect the soil and groundwater. For non-excavatible sites, in situ containment is the most viable approach for preventing further spread of contamination. The focus of this study is development of a barrier technology that can prevent or retard the spread and migration of liquid spills in the soil vadose zone thereby protecting the groundwater from liquid contaminants. The concept that is being investigated is an innovative approach referred to here as Circulating Air Barrier (CAB).

The CAB concept involves the circulation of air through a targeted subsurface zone, beneath or adjacent to the zone of contamination. The air circulation is achieved by either vertical or horizontal wells for air injection and extraction. The injected air vaporizes water in the zone and carries the water vapor to extraction well. The produced stream is then processed in the surface facility to remove the water and any contaminants or particulate. The circulation of the dry air lowers the water saturation (moisture content) of the soil. As a soil layer dries, progressively smaller and smaller pores empty and permeability for liquid flow decreases. Eventually, the water saturation decreases below the critical level for liquid flow. Thereafter, the soil layer will retain rather than transmit the liquids. In the event that a leak occurs, the air circulation will remove, through evaporation, liquids that have moved into the swept zone. Therefore, the CAB system can also serve as a tool for early leak detection and provides a means to withdraw volatile contaminants for surface treatment.

The concept of CAB was conceived to solve the subsurface contamination problems through applying directional and horizontal well drilling technology developed by petroleum industry. Similar concept has been discussed by others. However, there are no direct laboratory or field data available to evaluate the Circulating Air Barrier (CAB) concept and develop data needed for scale-up and demonstration to gain regulatory acceptance. The overall objective of this study has been to evaluate the feasibility and applicability of CAB technology. The focus of this paper is the drying of the unconsolidated, unsaturated porous media. Better understanding of the processes involved in drying of unsaturated porous media is critical for the design and field implementation of CAB technology.

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