In situ thermal processing of an oil shale formation using a controlled heating rate
An oil shale formation may be treated using an in situ thermal process. A mixture of hydrocarbons, H 2 , and/or other formation fluids may be produced from the formation. Heat may be applied to the formation to raise a temperature of a portion of the formation to a desired temperature. A heating rate for a selected volume of the formation may be controlled by altering an amount of heating energy per day that is provided to the selected volume.
1. A method of treating an oil shale formation in situ, comprising:
heating a selected volume (V) of the oil shale formation, wherein the formation has an average heat capacity (C v ), wherein heating the selected volume comprises transferring heat substantially by conduction, and wherein the heating pyrolyzes at least some hydrocarbons within the selected volume of the formation; and
wherein heating energy/day (Pwr) provided to the selected volume is equal to or less than h*V*C v *ρ B , wherein ρ B is formation bulk density, and wherein an average heating rate (h) of the selected volume is about 10° C./day.
2. The method of claim 1 , wherein heating a selected volume comprises heating with an electrical heater.
3. The method of claim 1 , wherein heating the selected volume comprises heating with a surface burner.
4. The method of claim 1 , wherein heating the selected volume comprises heating with a flameless distributed combustor.
5. The method of claim 1 , wherein heating the selected volume comprises heating with at least one natural distributed combustor.
6. The method of claim 1 , further comprising controlling a pressure and a temperature within at least a majority of the selected volume of the formation, wherein the pressure is controlled as a function of temperature, or the temperature is controlled as a function of pressure.
7. The method of claim 1 , wherein a value for C v is determined as an average heat capacity of two or more samples taken from the oil shale formation.
8. The method of claim 1 , wherein heating the selected volume comprises heating the selected volume such that a thermal conductivity of at least a portion of the selected section is greater than about 0.5 W/(m° C.).
9. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons having an API gravity of at least about 25°.
10. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein about 0.1% by weight to about 15% by weight of the condensable hydrocarbons are olefins.
11. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises non-condensable hydrocarbons, and wherein about 0.1% by weight to about 15% by weight of the non-condensable hydrocarbons are olefins.
12. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises non-condensable hydrocarbons, and wherein a molar ratio of ethene to ethane in the non-condensable hydrocarbons ranges from about 0.001 to about 0.15.
13. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein less than about 1% by weight, when calculated on an atomic basis, of the condensable hydrocarbons is nitrogen.
14. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein less than about 1% by weight, when calculated on an atomic basis, of the condensable hydrocarbons is oxygen.
15. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein less than about 1% by weight, when calculated on an atomic basis, of the condensable hydrocarbons is sulfur.
16. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, wherein about 5% by weight to about 30% by weight of the condensable hydrocarbons comprise oxygen containing compounds, and wherein the oxygen containing compounds comprise phenols.
17. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein greater than about 20% by weight of the condensable hydrocarbons are aromatic compounds.
18. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein less than about 5% by weight of the condensable hydrocarbons comprises multi-ring aromatics with more than two rings.
19. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein less than about 0.3% by weight of the condensable hydrocarbons are asphaltenes.
20. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises condensable hydrocarbons, and wherein about 5% by weight to about 30% by weight of the condensable hydrocarbons are cycloalkanes.
21. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises a non-condensable component, wherein the non-condensable component comprises molecular hydrogen, wherein the molecular hydrogen is greater than about 10% by volume of the non-condensable component, and wherein the molecular hydrogen is less than about 80% by volume of the non-condensable component at 25° C. and one atmospheric absolute pressure.
22. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises ammonia, and wherein greater than about 0.05% by weight of the produced mixture is ammonia.
23. The method of claim 1 , further comprising producing a mixture, wherein the produced mixture comprises ammonia, and wherein the ammonia is used to produce fertilizer.
24. The method of claim 1 , further comprising controlling a pressure within at least a majority of the selected volume of the formation, wherein the controlled pressure is at least about 2.0 bars absolute.
25. The method of claim 1 , further comprising controlling formation conditions to produce a mixture from the formation comprising condensable hydrocarbons and H 2 , wherein a partial pressure of H 2 within the mixture is greater than about 0.5 bars.
26. The method of claim 1 , wherein a partial pressure of H 2 is measured when the mixture is at a production well.
27. The method of claim 1 , further comprising altering a pressure within the formation to inhibit production of hydrocarbons from the formation having carbon numbers greater than about 25.
28. The method of claim 1 , further comprising controlling formation conditions, wherein controlling formation conditions comprises recirculating a portion of hydrogen from the mixture into the formation.
29. The method of claim 1 , further comprising:
providing hydrogen (H 2 ) to the selected volume to hydrogenate hydrocarbons within the selected volume; and
heating a portion of the selected volume with heat from hydrogenation.
30. The method of claim 1 , wherein the produced mixture comprises hydrogen and condensable hydrocarbons, the method further comprising hydrogenating a portion of the produced condensable hydrocarbons with at least a portion of the produced hydrogen.
31. The method of claim 1 , further comprising increasing a permeability of a majority of the selected volume to greater than about 100 millidarcy.
32. The method of claim 1 , further comprising substantially uniformly increasing a permeability of a majority of the selected volume.
33. The method of claim 1 , further comprising controlling the heat to yield greater than about 60% by weight of condensable hydrocarbons, as measured by Fischer Assay.
34. The method of claim 1 , wherein producing the mixture comprises producing the mixture in a production well, and wherein at least about 7 heat sources are disposed in the formation for each production well.
35. The method of claim 34 , wherein at least about 20 heat sources are disposed in the formation for each production well.
36. The method of claim 1 , further comprising providing heat from three or more heat sources to at least a portion of the formation, wherein three or more of the heat sources are located in the formation in a unit of heat sources, and wherein the unit of heat sources comprises a triangular pattern.
37. The method of claim 1 , further comprising providing heat from three or more heat sources to at least a portion of the formation, wherein three or more of the heat sources are located in the formation in a unit of heat sources, wherein the unit of heat sources comprises a triangular pattern, and wherein a plurality of the units are repeated over an area of the formation to form a repetitive pattern of units.