System for determining rate of ground water re-contamination due to rock matrix back diffusion

Abstract

The present invention is a low permeability rock matrix back diffusion testing system and method which enables contaminant concentrations and hydraulic pressure values to be independently tested. This system includes specially configured packer components which allow precise placement and maintain test conditions for the duration of a study to accurately measure and predict the rate of back flow diffusion over time in low permeability zones.

What is claimed is: 
     
         1 . A low permeability rock matrix back diffusion testing system comprised of:
 an upper conformable barrier and a lower conformable barrier which form an upper seal and a lower seal when in contact with the inner surface of a borehole;   wherein said upper seal and said lower seal form a plurality of test zones comprised of a lower test zone, a central isolated test zone and an upper test zone wherein each of said test zones has measurable chemical concentration values and hydraulic pressure values;   at least one lower test zone water line coupled with a lower test zone pump to enable the extraction of water from said lower test zone;   an air sparging conduit operatively coupled with a pressurized air source to expel contaminants from said central isolated test zone, wherein said air sparging conduit passes through said upper conformable barrier; and   a sparged contaminant conduit which passes though said upper barrier and said lower barrier to conduct sparged contaminants from said central isolated test zone.   
     
     
         2 . The system of  claim 1  which includes a test zone air line which conducts air to said lower test zone pump, which conducts water through said lower test zone water line and enables testing to obtain the hydraulic pressure values of said lower test zone independently from said central isolated test zone. 
     
     
         3 . The system of  claim 1  which includes a component for adjusting said hydraulic pressure values of said lower test zone while said hydraulic pressure values of said central isolated test zone remain constant. 
     
     
         4 . The system of  claim 1  which further includes an upper test zone water line and a central isolated test zone water line to conduct water independently from said upper test zone and said central isolated test zone. 
     
     
         5 . The system of  claim 1  which further includes chemical concentration sensors which independently measure said chemical concentration values of said upper test zone, said central isolated test zone and said lower test zone. 
     
     
         6 . The system of  claim 5  wherein said chemical concentration sensors are selected from a group consisting of water pressure sensors, water conductivity sensors, temperature sensors, dissolved oxygen sensors, oxidation-reduction potential sensors, turbidity sensors, total dissolved solids sensors, pH sensors, and water velocity sensors. 
     
     
         7 . The system of  claim 1  which further includes hydraulic pressure sensors which independently measure the hydraulic pressure values of said upper test zone, said central isolated test zone and said lower test zone. 
     
     
         8 . The system of  claim 1 , wherein said upper conformable barrier and said lower conformable barrier are comprised of inflatable structures containing a gas. 
     
     
         9 . The system of  claim 8  wherein said inflatable structures are filled with a combination of gas and fluid. 
     
     
         10 . The system of  claim 1 , wherein said upper conformable barrier and said lower conformable barrier are comprised of conformable material which conforms to the inner surface of a borehole to form a seal. 
     
     
         11 . The system of  claim 10 , wherein said upper conformable barrier and said lower conformable barrier are comprised of a material which are disposable after a single testing session. 
     
     
         12 . The system of  claim 1 , wherein said central isolated test zone includes a quantity of a detectible substance which indicates the presence of a leak in one or more of said upper and lower seals formed by said upper and said lower conformable barriers. 
     
     
         13 . The system of  claim 1  which further includes more than one of said upper conformable barriers and more than one of said lower conformable barriers. 
     
     
         14 . The system of  claim 1  which further includes a computer processing component which receives said chemical concentration values from said central isolated test zone. 
     
     
         15 . The system of  claim 14  which further includes a computer processing component which associates a time stamp with each of said chemical concentration values. 
     
     
         16 . The system of  claim 14  which further includes a computer processing component for performing a rock matrix diffusion calculation which calculates the change in said chemical concentration values over time for a given borehole radius. 
     
     
         17 . A method for measuring back diffusion, comprised of the steps of:
 placing a lower conformable barrier and an upper conformable barrier within a borehole to create a seal;   forming a central isolated test zone within a space between said lower conformable barrier and said upper conformable barrier containing a quantity of isolated fluid;   obtaining a first chemical concentration value associated with a first time;   sparging pressurized air into said central isolated test zone;   obtaining a second chemical concentration value associated with a second time; and   calculating the difference between said first contaminant concentration measurement and said second contaminant concentration measurement.   
     
     
         18 . The method of  claim 17  which further includes the step of adjusting lower test zone hydraulic pressure values while hydraulic pressure values of said central isolated test zone remain constant. 
     
     
         19 . The method of  claim 17  which further includes the step of performing a rock matrix diffusion calculation which calculates the change in said first and second chemical concentration values over time for a given borehole radius. 
     
     
         20 . The method of  claim 17  which further includes the step of monitoring for the presence of a detectible substance which indicates the presence of a leak in one or more of said upper and lower seals formed by said upper and said lower conformable barriers.