LIGHT HYDROCARBON RECOVERY USING A COMBINATION OF THERMAL AUGMENTATION AND BIOSLURPING

A technology for in situ soil heating combined with vacuum enhanced recovery (VER) has been developed by Golder Associates. The heating system developed is unique in its simple design, low cost and efficiency. Steel tubes (heating elements) of 6 in. diameter are inserted into the soil using standard environmental drilling equipment. The tubes heat the soils and groundwater by surface contact (conduction heating). At first, laboratory tests were performed at different scales and revealed significant increase in extraction rates for BTEX contaminated soils. In situ experiments were also performed on a gas station where a BTEX contamination was present in the soils and groundwater. Three extraction wells, seven heating elements and four monitoring points were used at this experimental site. Numerical modeling was performed using CompFlow to simulate and predict heat dispersion and multiphase flow of hydrocarbons. The temperatures reached in the soil were greater than 80oC and the recovery rates increased by 135 % compared to the extraction without heating. The soils and groundwater were remediated below target levels after 5 months of heating. The spread of heat in the subsurface is not dependent on soil permeability and therefore this technology is particularly appropriate for low permeability soils such as silts and clays that are difficult to treat with other conventional technologies. To date 5 to 6 months are required to reach the desired temperature in the subsurface and a typical remediation time frame is 6 to 18 months