Situ co-development of oil shale with mineral recovery

Abstract

A method of producing hydrocarbon fluids from a subsurface organic-rich rock formation, for example an oil shale formation, in which the oil shale formation contains water-soluble minerals, for example nahcolite, is provided. In one embodiment, the method includes the step of heating the organic-rich rock formation in situ. Optionally, this heating step may be performed prior to any substantial removal of water-soluble minerals from the organic-rich rock formation. In accordance with the method, the heating of the organic-rich rock formation both pyrolyzes at least a portion of the formation hydrocarbons, for example kerogen, to create hydrocarbon fluids, and converts at least a portion of the water-soluble minerals, for example, converts nahcolite to soda ash. Thereafter, the hydrocarbon fluids are produced from the formation.

What is claimed is: 
     
         1 . An in situ method of recovering natural resources, comprising:
 (a) heating in situ an organic-rich rock formation that contains both formation hydrocarbons and one or more formation water-soluble minerals,
 wherein the heating of the organic-rich rock formation both pyrolyzes at least a portion of the formation hydrocarbons to create hydrocarbon fluids and makes available one or more migratory contaminant species previously bound in the organic-rich rock formation; 
   (b) producing at least a portion of the hydrocarbon fluids from the organic-rich rock formation, but wherein at least a portion of the one or more migratory contaminant species remain in the organic-rich rock formation;   (c) injecting an aqueous fluid into the organic-rich rock formation, wherein the injected aqueous fluid dissolves at least a portion of one or more water-soluble minerals and the one or more migratory contaminant species to form a first aqueous solution;   (d) producing the first aqueous solution from the organic-rich rock formation;   (e) processing the first aqueous solution in a surface facility to remove a portion of the one or more water-soluble minerals; and   (f) processing the first aqueous solution in the surface facility to remove at least some of the one or more migratory contaminant species.   
     
     
         2 . The method of  claim 1 , wherein the heating step (a) results in at least a portion of the organic-rich rock formation reaching a temperature of 270° C. or greater. 
     
     
         3 . The method of  claim 2 , wherein the formation hydrocarbons include solid hydrocarbons. 
     
     
         4 . The method of  claim 3 , wherein the organic-rich rock formation is an oil shale formation. 
     
     
         5 . The method of  claim 2 , wherein the formation hydrocarbons include heavy hydrocarbons. 
     
     
         6 . The method of  claim 4 , wherein the organic-rich rock formation has an initial total permeability less than 1 millidarcy before the heating step (a). 
     
     
         7 . The method of  claim 6 , wherein the organic-rich rock formation has a post heating total permeability of greater than 10 millidarcies after the heating step (a) and before the injecting step (c). 
     
     
         8 . The method of  claim 4 , wherein the one or more migratory contaminant species include one or more of aromatic hydrocarbons, polyaromatic hydrocarbons, oxygenated hydrocarbons, metal contaminants, and ionic contaminants. 
     
     
         9 . The method of  claim 8 , wherein the one or more migratory contaminant species include one or more of benzene, toluene, xylene, ethylbenzene, tri-methylbenzene, and polyaromatic hydrocarbon species. 
     
     
         10 . The method of  claim 8 , wherein the one or more migratory contaminant species include one or more of metal contaminants containing arsenic, boron, chromium, mercury, selenium, lead, vanadium, nickel, cobalt, molybdenum and zinc. 
     
     
         11 . The method of  claim 4 , wherein the one or more water-soluble minerals include sodium. 
     
     
         12 . The method of  claim 11 , wherein the one or more formation water-soluble minerals comprise nahcolite (sodium bicarbonate), soda ash (sodium carbonate), dawsonite (NaAl(CO 3 )(OH) 2 ), or combinations thereof. 
     
     
         13 . The method of  claim 4 , wherein the heating step (a) is initiated prior to substantial removal of the one or more formation water-soluble minerals from the organic-rich rock formation. 
     
     
         14 . The method of  claim 4 , wherein the heating step (a) is initiated prior to removal of greater than 7 weight percent of the initially present one or more formation water-soluble minerals from the organic-rich rock formation. 
     
     
         15 . The method of  claim 4 , wherein the processing step (e) includes removing the one or more water-soluble minerals by precipitation caused by altering the temperature of the first aqueous solution. 
     
     
         16 . The method of  claim 4 , wherein the one or more formation water-soluble minerals include nahcolite (sodium bicarbonate) and the one or more water-soluble minerals include soda ash (sodium carbonate). 
     
     
         17 . The method of  claim 16 , wherein the heating step (a) includes generating the soda ash by decomposition of the nahcolite. 
     
     
         18 . The method of  claim 4 , wherein the heating step (a) is accomplished through introducing heat into heater wells penetrating at least partially through the organic-rich rock formation. 
     
     
         19 . The method of  claim 18 , wherein the heater wells include electrical resistance heating elements.