Recovery of shale oil and magnesia from oil shale

Claim 1

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent containing dissolved purgeable acid-forming gas for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 2

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent containing dissolved purgeable acid-forming gas for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 17

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; controlling the maximum temperature of particles in the fragmented mass in the range of from about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 18

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; controlling the maximum temperature of particles in the fragmented mass in the range of from about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 20

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; cooling particles in the fragmented mass before leaching by introducing carbon dioxide containing gas to the fragmented mass and withdrawing gas from the fragmented mass having a lower content of carbon dioxide than the introduced gas; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 21

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; cooling particles in the fragmented mass before leaching by introducing carbon dioxide containing gas to the fragmented mass and withdrawing gas from the fragmented mass having a lower content of carbon dioxide than the introduced gas; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 22

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; cooling particles in the fragmented mass before leaching by flowing carbon dioxide containing gas through the fragmented mass in a direction opposite to the direction of advancement of the combustion zone; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 23

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting oil shale to a form from which magnesium values can be selectively leached; cooling particles in the fragmented mass before leaching by flowing carbon dioxide containing gas through the fragmented mass in a direction opposite to the direction of advancement of the combustion zone; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 24

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling the maximum temperature of particles in the fragmented mass in the range of about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 25

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling the maximum temperature of particles in the fragmented mass in the range of about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 32

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting at least a portion of the carbonate of magnesium ion the fragmented mass to magnesium oxide; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an acidic aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved magnesium bicarbonate; withdrawing enriched solution containing dissolved magnesium bicarbonate from the fragmented mass; and recovering basic magnesium carbonate from such enriched solution.

Claim 33

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting at least a portion of the carbonate of magnesium ion the fragmented mass to magnesium oxide; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an acidic aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved magnesium bicarbonate; withdrawing enriched solution containing dissolved magnesium bicarbonate from the fragmented mass; and recovering basic magnesium carbonate from such enriched solution.

Claim 40

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting at least a portion of the oil shale in the fragmented mass to a form from which magnesium values can be leached, particles in the fragmented mass after advancement of the combustion zone therethrough containing combusted oil shale; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the combusted oil shale in the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide and introducing carbon dioxide containing gas at a partial pressure of carbon dioxide of at least about one atmosphere to the portion of the fragmented mass in contact with the leaching agent for forming an enriched solution containing dissolved magnesium bicarbonate; withdrawing enriched solution containing dissolved magnesium bicarbonate from the fragmented mass; and recovering basic magnesium carbonate from such enriched solution.

Claim 41

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for converting at least a portion of the oil shale in the fragmented mass to a form from which magnesium values can be leached, particles in the fragmented mass after advancement of the combustion zone therethrough containing combusted oil shale; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the combusted oil shale in the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide and introducing carbon dioxide containing gas at a partial pressure of carbon dioxide of at least about one atmosphere to the portion of the fragmented mass in contact with the leaching agent for forming an enriched solution containing dissolved magnesium bicarbonate; withdrawing enriched solution containing dissolved magnesium bicarbonate from the fragmented mass; and recovering basic magnesium carbonate from such enriched solution.

Claim 46

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for calcining at least a portion of the carbonate of magnesium in the fragmented mass to magnesium oxide; cooling the fragmented mass after advancement of the combustion zone therethrough; flooding at least a portion of the cooled fragmented mass with aqueous leaching agent containing sufficient dissolved carbon dioxide for dissolving magnesium oxide and forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 47

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone at sufficient temperatures for calcining at least a portion of the carbonate of magnesium in the fragmented mass to magnesium oxide; cooling the fragmented mass after advancement of the combustion zone therethrough; flooding at least a portion of the cooled fragmented mass with aqueous leaching agent containing sufficient dissolved carbon dioxide for dissolving magnesium oxide and forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 53

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in the oil shale in the retorting zone in decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling the maximum temperature of particles in the fragmented mass in the range of about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass for calcining at least a portion of the carbonate of magnesium in the fragmented mass to magnesium oxide; flooding at least a portion of the fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide at temperatures in the range of about 10° C. to 60° C. for dissolving magnesium oxide and forming enriched solution containing magnesium values; flowing carbon dioxide containing gas upwardly through the flooded portion of the fragmented mass, the partial pressure of carbon dioxide being at least about one atmosphere near the bottom of the fragmented mass; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 54

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of particles containing oil shale and carbonate of magnesium in an in situ oil shale retort by introducing an oxygen-containing gas into the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in the oil shale in the retorting zone in decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling the maximum temperature of particles in the fragmented mass in the range of about 600° C. to 800° C. during advancement of the combustion zone through the fragmented mass for calcining at least a portion of the carbonate of magnesium in the fragmented mass to magnesium oxide; flooding at least a portion of the fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide at temperatures in the range of about 10° C. to 60° C. for dissolving magnesium oxide and forming enriched solution containing magnesium values; flowing carbon dioxide containing gas upwardly through the flooded portion of the fragmented mass, the partial pressure of carbon dioxide being at least about one atmosphere near the bottom of the fragmented mass; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 57

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a first fragmented permeable mass of formation particles containing oil shale and magnesium values in a first in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zones at sufficient temperatures for converting at least a portion of the oil shale in the first fragmented mass to a form from which magnesium values can be leached; advancing a combustion zone through a second fragmented permeable mass of formation particles containing oil shale in a second in situ oil shale retort by introducing an oxygen-containing gas into the second fragmented mass on a trailing side of the combustion zone and withdrawing a carbon dioxide containing off gas from the second fragmented mass on an advancing side of the combustion zone; cooling the first fragmented mass after advancement of the combustion zone therethrough; selectively leaching magnesium values from such a cooled first fragmented mass by contacting at least a portion of such cooled first fragmented mass with aqueous leaching agent comprising dissolved carbon dioxide and introducing at least a portion of such off gas from such a second in situ oil shale retort into such a portion of such a first cooled fragmented mass for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the first retort; and recovering magnesium values from such enriched solution.

Claim 58

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a first fragmented permeable mass of formation particles containing oil shale and magnesium values in a first in situ oil shale retort by introducing an oxygen containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zones at sufficient temperatures for converting at least a portion of the oil shale in the first fragmented mass to a form from which magnesium values can be leached; advancing a combustion zone through a second fragmented permeable mass of formation particles containing oil shale in a second in situ oil shale retort by introducing an oxygen-containing gas into the second fragmented mass on a trailing side of the combustion zone and withdrawing a carbon dioxide containing off gas from the second fragmented mass on an advancing side of the combustion zone; cooling the first fragmented mass after advancement of the combustion zone therethrough; selectively leaching magnesium values from such a cooled first fragmented mass by contacting at least a portion of such cooled first fragmented mass with aqueous leaching agent comprising dissolved carbon dioxide and introducing at least a portion of such off gas from such a second in situ oil shale retort into such a portion of such a first cooled fragmented mass for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the first retort; and recovering magnesium values from such enriched solution.

Claim 66

A method for recovering shale oil and leaching magnesium values from particles containing oil shale and carbonated magnesium which comprises: retorting such particles for decomposing kerogen in oil shale to produce gaseous and liquid products including shale oil and heating retorted particles at a maximum temperature sufficient for converting oil shale to a form from which magnesium values can be leached; contacting such retorted heat particles with an aqueous solution containing sufficient dissolved carbon dioxide for selectively leaching magnesium values from the particles and for forming an enriched solution containing dissolved carbon dioxide and such magnesium values; separating such enriched solution from the particles; and recovering magnesium values from such enriched solution.

Claim 67

A method for recovering shale oil and leaching magnesium values from particles containing oil shale and carbonated magnesium which comprises: retorting such particles for decomposing kerogen in oil shale to produce gaseous and liquid products including shale oil and heating retorted particles at a maximum temperature sufficient for converting oil shale to a form from which magnesium values can be leached; contacting such retorted heat particles with an aqueous solution containing sufficient dissolved carbon dioxide for selectively leaching magnesium values from the particles and for forming an enriched solution containing dissolved carbon dioxide and such magnesium values; separating such enriched solution from the particles; and recovering magnesium values from such enriched solution.

Claim 71

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at a maximum temperature below a temperature which promotes formation of a mineral crystal barrier on the particles during leaching; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent containing dissolved purgeable acid-forming gas for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 72

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale and magnesium values which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and magnesium values in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on the trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on the advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, such carbonaceous residue supporting combustion in the combustion zone at a maximum temperature below a temperature which promotes formation of a mineral crystal barrier on the particles during leaching; selectively leaching magnesium values from at least a portion of the fragmented mass by contacting particles in the fragmented mass with an acidic aqueous leaching agent containing dissolved purgeable acid-forming gas for forming enriched solution containing magnesium values; withdrawing enriched solution containing magnesium values from the retort; and recovering magnesium values from such enriched solution.

Claim 76

A method for recovering shale oil and magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonates of magnesium and calcium in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling conditions in the retort during retorting for converting oil shale in the retort to a form that is permeable to aqueous liquid and that substantially retains it permeability during leaching with acidic aqueous leaching agent; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 77

A method for recovering shale oil and magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonates of magnesium and calcium in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling conditions in the retort during retorting for converting oil shale in the retort to a form that is permeable to aqueous liquid and that substantially retains it permeability during leaching with acidic aqueous leaching agent; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 81

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonates of magnesium and calcium in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling conditions in the retort during retorting for limiting the decomposition of calcium carbonate and preferentially converting magnesium carbonate to magnesium oxide, the decomposition of calcium carbonate being limited sufficiently for retarding or avoiding the growth of calcium mineral crystals on the particles during leaching; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.

Claim 82

A method for recovering shale oil and leaching magnesium values from formation particles in an in situ oil shale retort in a subterranean formation containing oil shale which comprises: advancing a combustion zone through a fragmented permeable mass of formation particles containing oil shale and carbonates of magnesium and calcium in an in situ oil shale retort by introducing an oxygen-containing gas to the fragmented mass on a trailing side of the combustion zone and withdrawing an off gas from the fragmented mass on an advancing side of the combustion zone, whereby gas flowing through the combustion zone transfers heat of combustion to a retorting zone in the fragmented mass on the advancing side of the combustion zone and wherein kerogen in oil shale in the retorting zone is decomposed to produce gaseous and liquid products including shale oil and carbonaceous residue, said carbonaceous residue supporting combustion in the combustion zone; controlling conditions in the retort during retorting for limiting the decomposition of calcium carbonate and preferentially converting magnesium carbonate to magnesium oxide, the decomposition of calcium carbonate being limited sufficiently for retarding or avoiding the growth of calcium mineral crystals on the particles during leaching; cooling the fragmented mass after advancement of the combustion zone therethrough; contacting at least a portion of the cooled fragmented mass with an aqueous leaching agent containing sufficient dissolved carbon dioxide for forming enriched solution containing dissolved carbon dioxide and magnesium values; withdrawing enriched solution containing magnesium values from the fragmented mass; and recovering magnesium values from such enriched solution.