Method for removing a contaminant from a contaminated surface soil

Contaminants are removed from a contaminated surface soil by contacting the soil with a solvent in which the contaminate is soluble and then vacuuming the solvent with the contaminants dissolved therein from the soil.

BACKGROUND OF THE INVENTION 
Hydrocarbon production operations often involve the handling of high saline 
water recovered from a subsurface oil or gas reservoir along with the oil 
or gas. Typically such saline water is separated from the particular 
hydrocarbon and disposed of by surface ponding or by reinjection into the 
formation. With surface disposal, the soil will become contaminated with 
salt and/or other materials and rendered unsuitable for plants and 
vegetation. With subsurface disposal, piping leaks, breaks or operational 
upsets at the surface could cause the surface soil to become contaminated 
by the saline water. 
Current technologies available for the treatment of surface soils 
contaminated with organic or inorganic pollutants can be classified as 
in-situ and ex-situ techniques. In the in-situ process, solvent is sprayed 
on the surface of the contaminated soil. The solvent, after contacting the 
soil and dissolving the organic or inorganic materials, is collected via a 
pump or perforated pipe located below the soil's surface. In the ex-situ 
process, the contaminated soil is excavated and moved to a central 
location where soil is performed. 
SUMMARY OF THE INVENTION 
In accordance with the present invention there is provided a method for 
removing a contaminant from a surface formation by contacting the surface 
formation with a solvent in which the contaminant is soluble and then 
vacuuming the solvent with the contaminant dissolved therein from the 
surface formation. The solvent may be sprayed onto the surface of the 
formation or injected into the formation. The method may be enhanced by 
increasing the permeability of the formation to the solvent prior to the 
solvent contacting treatment. Such contacting, vacuuming and permeability 
enhancing steps may be repeated as necessary to provide a desired degree 
of contaminant removal. 
In a further aspect, the contaminant may be separated from the 
contaminant-saturated solvent vacuumed from the surface formation to 
recover the solvent for use in further treatments of the formation. 
BRIEF DESCRIPTION OF THE DRAWING 
The sole figure is a pictorial illustration of the carrying out of the soil 
contamination removal steps of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing, there is illustrated a surface formation 10 
containing a contaminate that is to be removed. A soil washing machine 11 
is moved into position above the formation 10. A solvent in which the 
contaminate is soluble is contained within a solvent supply 12. For 
example, should formation 10 have been used as a depository of high saline 
water such as might have been recovered from hydrocarbon production 
operations, the solvent in supply 12 would preferably be clean water. 
Using this as one example in describing the present invention, the clean 
water from supply 11 is applied by the spray or injection means 13 to the 
surface of formation 10. 
After the elapse of a predetermined time period during which the water 
reacts with and dissolves the salt deposited within the formation 10, a 
vacuum means 14 is operated to remove the salt-containing water from the 
formation for collection in the contaminated solvent container 15. Each 
soil washing treatment may be repeated as many times as required until the 
soil becomes suitable for agriculture or other intended uses. 
The time period for each soil washing treatment will vary in accordance 
with the contaminate to be removed and the solvent to be used in the 
treatment. For the above described example of washing the soil with water 
to remove salt contaminates, an effective soak period would be in the 
order of less than a minute before vacuuming. Surfactants or other 
additives may be added to the solvent to enhance the removal of salt or 
other contaminants, such as organic hydrocarbons. 
Efficiency of the contaminate removal during the soil washing treatment can 
be further improved by heating the particular solvent prior to spraying or 
injection into the formation so as to increase its reaction with the 
particular contaminate to be removed. The soil washing treatment may 
further be improved by increasing formation permeability either before or 
during the treatment. For example, the formation may be treated with a 
suitable additive, such as calcium chloride. Also the formation might be 
plowed and leveled prior to treatment. 
After vacuuming the contaminate-saturated solvent from the formation, the 
contaminate may be separated from the solvent so that the solvent may be 
used in further formation treatments. 
While the foregoing preferred embodiment of the present invention has been 
described and illustrated, numerous modifications or alterations maybe 
made without departing from the spirit and scope of the invention as set 
forth in the appended claims.