Site Reclamation Technology
Cleaning and reclaiming mature producing locations are major and increasingly costly obligations of producers. The prevailing methodology for “remediation” simply involves collecting contaminated soil and moving it to another location such as a landfill, and replacing it with clean material.
Original Design for Kuwait Application
Winterhawk’s location-based site reclamation technology was originally developed for use in the Kuwait Bergan oil field, and is based on Canada’s oil sands extraction industry. Our “near-situ” process will increase soil cleaning performance and reduce costs, and not simply move the problem from one area to another.
The Winterhawk soil-reclamation process is based on well-understood organic chemistry and principles of thermodynamics. The process patent describes these principles in a contained, thermally accelerated, two-stage batch process within a “treatment cell.”
This process is contained in a lined treatment cell, in this example 100 by 100 meters square (one hectare) in area to a depth of approximately three meters. The pit is lined with a fabric that is high-temperature-tolerant, flame-resistant, and impermeable to hydrocarbons and water.
In the first stage, the oily soil is saturated with a heated solvent that has a high affinity for the hydrocarbon molecules. The solvent dissolves all the heavier hydrocarbons and suspends them in solution so they can be removed with the solvent. This solvent/hydrocarbon mixture is then pumped out and processed in a normal crude-gathering/processing system and delivered to a refinery gate or tanker.
In the second stage, a hot-water-and-surfactant solution is used to remove the residual solvent and salt contaminants from the soil. Here water and surfactant is contacted with the solvent- saturated soil. This process stage also efficiently recovers heat from the soil, which serves to reduce costs. The salt contaminants are dissolved and removed in solution with the water. The water/surfactant solution removes the solvent by suspending it as an emulsion. This emulsion is drawn off of the soil and put into skim tanks. The emulsion breaks down, and the solvent is separated from the water/surfactant solution by gravity. The water/surfactant solution can be reused repeatedly. When the salt concentration reaches a specific point, the solution is processed in a reverse osmosis (RO) plant to remove the salt content. The rich saline solution from the RO plant is injected into existing deep salt-water disposal wells.
The heat to the fabric-lined pit is provided by electrical resistance heaters placed above the fabric. The addition of heat speeds the process significantly by increasing the solubility of the heavy-oil components in the solvent, and by increasing the cleaning action of the water/surfactant solution. Where available, Winterhawk will utilize power from the existing electricity grid for heating. For more remote locations, electrical generators will be employed.
Fugitive emissions from the process will be eliminated though a simple vapour-recovery system that utilizes a cap for the pit made of the same fabric as the pit liner, but in a lighter weight.
The process design minimizes the transportation of the contaminated soil, as the equipment is modularized and easily transportable. Each commercial plant is designed to be placed in a location, where it is used to clean the region immediately surrounding it. The plant is then moved to the next location.
The patent plant design will process approximately 30,000 cubic meters of oil-soaked soil per month.
Modifications for Canadian Application
Canadian oilfield contamination is normally caused by the indiscriminate use of drilling fluids and or the leakage of produced water on drilling sites or along produced-fluid pipeline gathering systems. It can contain small amounts of crude oil contaminants, but the more serious contaminant is salt.
For Canadian use, the Winterhawk process will be reduced in size and complexity.
The salt will be washed from the soil with a heated freshwater bath, and where oil contaminants exist (tri sodium phosphate) (TSP) surfactant will be added to the water to emulsify and remove the oil. The wash water will be pumped to portable tanks from where it can be directed to an evaporative desalination process. This will increase the salinity of the water to the saturation point. Heat will be supplied by a low-pressure steam generated in a standard oilfield boiler. Distillate water will be condensed in aerial coolers and reused in the wash process. The saturated salt solution will be trucked to and disposed of in the nearest wastewater disposal well.
The treatment cell will be built with an above-ground containment area made of a straw bale exterior wall lined with a leak-proof high-service-temperature liner. The contaminated soil will be excavated from the site and moved just a few meters to the treatment cell. Once the soil is cleaned it can be transferred back to its original location.
The straw bales will be used repeatedly until they lose their compressive strength and then will be broken up and land farmed into the cleaned soil when it is replaced. This will improve the quality of the soil by the addition of compostable material.
The size of the treatment cell will be determined by the area/volume of the contaminated site. Portable tanks will be used for storage of fresh and dirty wash water. Dependent on availability of grid power, the boiler may be electric or natural gas fired. Portable skid-mounted pump and valve assemblies will be used for the transfer of wash water.