Modification of subsurface strata by in situ replacement reactions for sequestering mobilization of heavy metals, metalloids, radionuclides or other naturally occurring contaminants

Abstract

Methods for in situ formation of a replacement reaction crystalline coating, acting as an impermeable barrier along grain surfaces, pore throats or dissolution cavities of rocks containing a percentage of free reactive cations and/or carbonate-containing compounds. This replacement crystalline coating is comprised of fluoride compounds, such as fluorite (CaF 2 ), fluorapatite (Ca 5 [F(PO 4 ) 3 ]) and sallaite (MgF 2 ). The coating or lining is capable of sequestering mobilization and/or movement of radionuclides, metals, metalloids and other naturally occurring undesirables from the media, rock or strata, while allowing water, fluids and other compounds to pass through pre-existing or induced permeability. The sequestration is achieved by shielding the media, rock or strata grains and/or matrix from interacting with pore fluids, hence greatly reducing solubility, dissolution, geochemical leaching and/or other chemical reactions from proceeding. The crystalline coating will have minimal affect on existing natural or induced permeability of the carbonate-containing rock, formation or strata. The methods can be utilized in subsurface reservoirs and/or aquifers.

1 . A method for sequestering mobilization or movement of naturally occurring contaminants in carbonate-containing rock, formations and/or strata: 
 Artificially inducing fluorine compound growth to create a lining or coating on the surface of a rock extending laterally over a pre-selected area;    A fluorine enriched solution, acid, or base reacts with free ions of carbonate-containing media to chemically replace said media with a fluoride compound;    The creation of fluorine compounds allows the substitution of free ions to be bound in its crystal structure, or contained in voids within its structure;    The fluoride compound acts as a coating or lining to prevent contaminated zones from commingling with zones of interest;    The coating or lining generated will use, but not limited to using, components in the naturally occurring rock as a reactant;    Allows nitric acid to be injected in certain cases to dissolve minerals or compounds that do not react with the replacement fluoride compound;    Allows injection of fluids into treated zones while protecting stratum from direct contact and unwanted reactions with injected fluids.    
   
   
       2 . The method of  claim 1 , wherein the active replacement reaction allows for substitution within the compound to bind and/or sequester undesirable elements.  
   
   
       3 . The method of  claim 1 , wherein the replacement reaction acts as an impermeable liner on the surface of pore throats, dissolution cavities, or rock surface to minimize native rock chemical reactions, dissolution and/or leaching.  
   
   
       4 . The method of  claim 1 , wherein the replacement reaction uses fluorine as a catalyst to form replacement compounds with a phosphate of or a magnesium component.  
   
   
       5 . The method of  claim 1 , wherein the reaction to form a fluoride compound has occurred, leaves a coating that will be non-reactive to nitric acid in some cases, allowing nitric acid to dissolve any non-fluoride compounds or minerals exposed that are soluble to said acid.  
   
   
       6 . The method of  claim 1 , wherein the creation of the desired compounds entails the injection of treatment fluids below the surface of the earth.  
   
   
       7 . The method of  claim 1 , wherein the pH of the solution is in need of buffering, or other pH controls; other acids, fluids, or bases can be employed.  
   
   
       8 . The method of  claim 6 , wherein the treatment requires, said treatment would be injected or pumped with an energized fluid.  
   
   
       9 . The method of  claim 8 , wherein the term ‘energized’ refers to the use of nitrogen, carbon dioxide, or other addition that creates a volume change of treatment fluid after the pump head.  
   
   
       10 . The method of  claim 6 , wherein the desired reaction requires a temperature different from the native subsurface environment, methods can be employed to modify the temperature of the treatment environment.  
   
   
       11 . The method of  claim 10 , wherein the temperature of the subsurface environment must be modified, the use of steam injection, pumping of heated fluids, or other methods designed to achieve a temperature change in the treatment environment.  
   
   
       12 . The method of  claim 5 , wherein many compounds are soluble in nitric acid, many fluoride compounds are not.  
   
   
       13 . The method of  claim 1 , delaying the release of fluorine, for reasons such as delayed replacement reaction.  
   
   
       14 . The method of  claim 13 , wherein a solution, acid, or base has the ability to delay the release of the fluorine ion for replacement reaction treatment, such as due to chemical reactions that have fluorine being released as a product of other reactions.  
   
   
       15 . The method of  claim 6 , wherein a fluorine solution, acid, or base is injected in an effort to open pathways through the rock, strata or formation or through the matrix of a rock, strata, formation or media.  
   
   
       16 . The method of  claim 15 , wherein a fluorine solution, acid, or base can be pumped at pressures below the minimum in-situ pressure of the rock, formation or strata, through natural or induced permeability (matrix rates); or at pressures exceeding the minimum in-situ pressures of a rock (fracturing) with a goal of precipitating a fluoride compound.  
   
   
       17 . A method of cleaning and/or filtering industrial injected waters or fluids that entails injection in one well, and recovering in an adjacent well.  
   
   
       18 . The method of  claim 17 , wherein fluoride enriched waters or fluids are injected below the surface into a confined or unconfined aquifer and recovered in an adjacent well.  
   
   
       19 . A method of protecting a confined zone in a subsurface rock, formation and/or strata from deleterious effects of injection of wastewaters or waste fluids.  
   
   
       20 . The method of  claim 19 , wherein an subsurface zone of rock, formation and/or strata is targeted for use as waste disposal, a treatment is performed before, during or after the injection of waste waters or fluids to protect the disposal zone of rock formation and/or strata from chemical reaction, dissolution or other undesired effects from waste waters or fluids.