Claims
- 1. In an in situ oil shale retort for recovering carbonaceous materials from oil shale wherein a subterranean cavity is formed above an access tunnel in a formation containing oil shale, the cavity containing a fragmented permeable mass of formation particles substantially filling the cavity, apparatus comprising gas pumping means having an input and output, means connecting the input of the gas pumping means to the bottom region of the retort cavity through the access tunnel for pumping gas from the cavity, and means for blocking the tunnel adjacent the cavity, the improvement comprising the gas pumping means having sufficient capacity for reducing the gas pressure within the bottom region of the cavity to a pressure below the pressure in the access tunnel to prevent leakage from the cavity into the access tunnel.
- 2. In the apparatus of claim 1, the further improvement comprising inlet means connecting the upper portion of the cavity to the atmosphere such that the pressure in the cavity will cause air to flow from the atmosphere into the upper region of the cavity through said inlet means.
- 3. In the apparatus of claim 1, the further improvement comprising inlet means connecting the upper portion of the cavity to the atmosphere and blower means for forcing air into said inlet means with sufficient pressure to balance the pressure drop through the inlet means while maintaining the bottom of the cavity at subatmospheric pressure.
- 4. In a process for retorting oil shale in situ wherein a subterranean cavity is formed in a formation containing oil shale, the formation contains underground workings, the cavity contains a fragmented permeable mass of formation particles containing oil shale and the particles containing oil shale in the cavity are burned and produce product gases wherein the improvement comprises pumping gases from the bottom of the cavity at a rate sufficient to reduce the pressure within all parts of the cavity to a pressure below the ambient pressure within underground workings adjacent the cavity for preventing leakage of product gases from the cavity into such underground workings.
- 5. In a process for retorting oil shale in situ by forming a subterranean cavity in a formation containing oil shale, the cavity containing a fragmented permeable mass of formation particles containing oil shale and burning the oil shale particles in an upper region of the cavity and producing product gases, an improved method of preventing leakage of product gases comprising pumping gases from the bottom of the cavity at a rate sufficient to reduce the pressure within all parts of the cavity to subambient levels, and pumping fresh air into the upper region of the cavity in combination with pumping out of the product gases at a rate sufficient to maintain the pressure at the top of the cavity at or slightly below ambient pressure.
- 6. In a process for retorting oil shale in situ wherein a subterranean cavity containing particles of oil shale is formed in an oil shale deposit adjacent at least one tunnel in the deposit and carbonaceous material in the oil shale is burned and produces product gases, wherein the improvement in the process is for preventing leakage of product gases into such an adjacent tunnel and comprises the step of pumping product gases from the cavity at a rate sufficient to reduce the pressure in the cavity adjacent to such tunnel to a pressure below the ambient pressure within such tunnel.
- 7. A process as recited in claim 6 wherein the tunnel is adjacent the bottom of the cavity and the pumping step comprises pumping product gases from the bottom of the cavity.
- 8. A process as recited in claim 7 wherein the pumping is at a sufficient rate to reduce the pressure within all parts of the cavity to less than ambient pressure in such a tunnel.
- 9. A process as recited in claim 7 wherein the top of the cavity is in fluid communication with the atmosphere and the pumping is at a sufficient rate to cause air to flow from the atmosphere into the top of the cavity.
- 10. In an in situ oil shale retort in a subterranean formation containing oil shale for retorting carbonaceous materials from oil shale wherein the retort is formed adjacent at least one tunnel in the formation, the retort containing a fragmented permeable mass of formation particles containing oil shale, wherein the improvement comprises gas withdrawing means connected to the retort for withdrawing gas from the retort, the withdrawing means having sufficient capacity for reducing the gas pressure within at least a portion of the retort adjacent such a tunnel to a pressure less than the pressure in the tunnel to prevent leakage of gas from the retort into the tunnel.
- 11. The apparatus of claim 10 further including inlet means for communicating with the retort remote from the gas withdrawing means for introducing an inlet gas into the retort.
- 12. The apparatus of claim 11 in which the withdrawing means has sufficient capacity for reducing pressure in the retort enough to cause air to flow from the atmosphere into the retort through said inlet means.
- 13. The apparatus of claim 11 further including blower means connected to the inlet means for introducing gas into said inlet means.
- 14. In a process for retorting oil shale in an situ oil shale retort in a subterranean formation containing oil shale, the retort containing a fragmented permeable mass of formation particles containing oil shale, comprising igniting a portion of the fragmented mass for establishing a combustion zone therein, introducing an oxygen supplying gas at a gas inlet to the fragmented mass on a trailing side of the combustion zone for sustaining the combustion zone and advancing the combustion zone through the fragmented mass, whereby a retorting zone is sustained and advanced through the fragmented mass on the advancing side of the combustion zone for producing liquid and gaseous products, and withdrawing off gas containing the gaseous products from the fragmented mass on the advancing side of the retorting zone, said formation having at least one tunnel adjacent the retort, the improvement comprising a method of preventing leakage of gas from the in situ oil shale retort to such a tunnel by withdrawing off gas from the fragmented mass on the advancing side of the retorting zone at a rate sufficient to reduce pressure within the in situ oil shale retort on the advancing side of the combustion zone to less than the ambient pressure in such a tunnel.
- 15. In a process as recited in claim 14 wherein off gas is withdrawn from the retort at a rate sufficient to reduce the pressure in all parts of the retort to less than the ambient pressure in such a tunnel adjacent the retort.
- 16. In a process as recited in claim 14, the further improvement comprising the step of introducing air into the retort while withdrawing off gas at a rate sufficient to maintain pressure at the gas inlet to the retort at or slightly below the ambient pressure in such a tunnel adjacent the retort.
CROSS-REFERENCES
This application is a continuation-in-part of U.S. patent application Ser. No. 492,823, now abandoned filed July 29, 1974, and assigned to the assignee of this application.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
812,573 |
Sep 1951 |
DT |
Continuation in Parts (1)
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Number |
Date |
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Parent |
492823 |
Jul 1974 |
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