PRODUCING HYDROCARBONS FROM OIL SHALE BASED ON CONDITIONS UNDER WHICH PRODUCTION OF OIL AND BITUMEN ARE OPTIMIZED
Kerogen in oil shale is converted to bitumen, oil, gases and coke via a retorting process. The vaporizable oil and gases are then recovered. Following the retorting process, bitumen is recovered via solvent extraction. The overall conversion process is enhanced by calculating conditions to optimize recovery of both oil and bitumen. This can be accomplished by either separately calculating conditions for which production of vaporizable oil and production of bitumen are optimized, or calculating conditions for which production of vaporizable oil and production of bitumen are optimized by applying a maximizing function to combined vaporizable oil and bitumen data. An advantage of this technique is that greater efficiency is achieved because the time duration of heating associated with the retorting process can be reduced and product yields increased.
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The present invention is generally related to development of energy resources, and more particularly to producing hydrocarbons from oil shale.
One kind of oil shale is sedimentary rock that contains little liquid hydrocarbon, but includes a significant amount of a solid organic phase known as kerogen. Kerogen has not been exposed to the temperatures and pressures required to completely convert it into oil and gas. Kerogen cannot be pumped directly out of the ground because it is solid. Further, kerogen is insoluble in common organic solvents. However, kerogen can be mined and processed to generate a liquid hydrocarbon similar to conventional oil. For example, mined oil shale can be crushed and then heated in a process known as retorting in order to convert the kerogen into various useful products.
Retorting mined oil shale has certain drawbacks including being costly and environmentally problematic. Mining generally requires movement of large quantities of material to a treatment facility. Further, a byproduct of the process is large quantities of spent shale, the disposal of which is environmentally problematic. Surface mining can be less costly than underground mining, but tends to alter the site of the mine in an environmentally problematic manner and still produces spent shale. An alternative technique known as “in situ retorting” is currently being studied because it helps to mitigate these problems. The in situ retorting technique involves heating the oil shale in the subterranean reservoir in order to produce a fluid product which can be produced to the surface, thereby leaving the spent shale in place. However, heating a reservoir to a sufficiently high temperature, e.g., greater than 325° C., in order to convert the kerogen requires considerable energy input relative to the amount of liquid product returned.
SUMMARY OF THE INVENTIONA method in accordance with one aspect of the invention includes the steps of: calculating input conditions under which production of vaporizable oil and production of bitumen are optimized; and recovering vaporizable oil and bitumen using the calculated input conditions.
Apparatus in accordance with one aspect of the invention includes an analyzer which calculates input conditions under which production of vaporizable oil and production of bitumen are optimized; and production equipment which recovers vaporizable oil and bitumen using the calculated input conditions.
In contrast with prior art techniques based simply on recovery of vaporizable oil, oil shale conversion is enhanced by calculating conditions to optimize recovery of both oil and bitumen. This can be accomplished by either separately calculating a program of heating times, temperatures, pressures, and additives for which production of vaporizable oil and production of bitumen are optimized, or calculating a program of heating times, temperatures, pressures, and additives for which production of vaporizable oil and production of bitumen are optimized by applying a weighted maximizing function to combined vaporizable oil and bitumen data. An advantage of this technique is that greater efficiency is achieved because the amount of heating associated with the retorting process can be reduced and the yield of valuable products can be increased.
Substances associated with recovery of hydrocarbons from oil shale include kerogen, bitumen, oil, hydrocarbon gas, nonhydrocarbon gas, and coke. In the description that follows the terms are used with the following meanings. Kerogen is a native state component of oil shale which is a solid, organic in origin, and insoluble in common organic solvents. Bitumen is a hydrocarbon which does not migrate out of the heated reservoir and is soluble in one or more organic solvents. Oil is a hydrocarbon product which does migrate out of the heated reservoir (this includes wax, which is solid at room temperature but melts below 100° C.). Hydrocarbon gas is a mixture of noncondensable (at standard temperature and pressure) products such as methane, ethane and propane. Nonhydrocarbon gas includes carbon dioxide. Coke is solid residuum, insoluble in common organic solvents, mainly composed of carbon.
The general characteristics of oil shale conversion have been described by R. L. Braun and A. K. Burnham, Chemical Reaction Model for Oil and Gas Generation from Type I and Type II Kerogen, Lawrence Livermore National Laboratory Report UCRL-ID-114143, June 1993, which is hereby incorporated by reference. Braun and Burnham describe ten transformations associated with the pyrolysis of Type I kerogen. In accordance with an aspect of this invention, oil shale conversion includes the following two steps: (1) kerogen is converted to bitumen, oil, gases and coke; and (2) bitumen is converted to oil, gases and coke. These steps are described in greater detail below.
Referring to
In the second step bitumen is recovered from the partially spent oil shale after the oil and gases produced by the retorting process have been recovered. Active or passive cooling of the reservoir at this stage may be desirable. In the illustrated embodiment a solvent from a storage tank (108) is introduced to the reservoir via the borehole 102 to facilitate bitumen recovery. Generally, bitumen is too viscous to be recovered via the pipes. However, mixing of the solvent with the bitumen results in a product characterized by a viscosity that permits recovery via the pipes. The solvent based extraction process could be somewhat similar to the technique known as VAPEX which is used for heavy oil production (see e.g. Oliveira et al., SPE 122040 (2009), which is hereby incorporated by reference). The bitumen is also processed at the surface processing facility to produce oil and other residual materials.
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In view of the description above it will be appreciated that aspects of the invention are not limited to use in association with in situ retorting. For example, aspects of the invention could be utilized to enhance recovery techniques based on mining, such as where mined oil shale is crushed and treated at the surface, or where oil shale is reburied in a treatment tunnel.
While the invention is described through the above exemplary embodiments, it will be understood by those of ordinary skill in the art that modification to and variation of the illustrated embodiments may be made without departing from the inventive concepts herein disclosed. Moreover, while the preferred embodiments are described in connection with various illustrative structures, one skilled in the art will recognize that the system may be embodied using a variety of specific structures. Accordingly, the invention should not be viewed as limited except by the scope and spirit of the appended claims.
Claims
1. A method comprising the steps of:
- calculating input conditions under which production of vaporizable oil and production of bitumen are optimized; and
- recovering vaporizable oil and bitumen using the calculated input conditions.
2. The method of claim 1 including recovering the vaporizable oil with a retorting process and recovering the bitumen with a solvent extraction process.
3. The method of claim 1 including separately calculating a program of heating times, temperatures, pressures, and/or additives for which production of vaporizable oil and production of bitumen are optimized.
4. The method of claim 1 including calculating a program of heating times, temperatures, pressures, and/or additives for which production of vaporizable oil and production of bitumen are optimized by applying a maximizing function to combined vaporizable oil and bitumen data.
5. The method of claim 1 including obtaining samples of oil shale from the reservoir interval or intervals of interest.
6. The method of claim 5 including performing pyrolysis experiments to determine effects of temperature, pressure, heating rate, heating duration, and/or additives.
7. The method of claim 5 including quantifying vaporizable oil and gas.
8. The method of claim 7 including quantifying the bitumen.
9. The method of claim 8 including quantifying the bitumen using nuclear magnetic resonance.
10. Apparatus comprising:
- an analyzer which calculates input conditions under which production of vaporizable oil and production of bitumen are optimized; and
- production equipment which recovers vaporizable oil and bitumen using the calculated input conditions.
11. The apparatus of claim 10 equipment that retorts oil shale to recover the vaporizable oil and solvent extraction equipment to recover the bitumen.
12. The apparatus of claim 10 wherein the analyzer separately calculates a program of heating times, temperatures, pressures, and/or additives for which production of vaporizable oil and production of bitumen are optimized.
13. The apparatus of claim 10 wherein the analyzer calculates a program of heating times, temperatures, pressures, and/or additives for which production of vaporizable oil and production of bitumen are optimized by applying a maximizing function to combined vaporizable oil and bitumen data.
14. The apparatus of claim 10 wherein the analyzer operates upon samples of oil shale from the reservoir interval or intervals of interest.
15. The apparatus of claim 14 wherein the analyzer performs pyrolysis experiments to determine effects of temperature, pressure, heating rate, heating duration and/or additives.
16. The apparatus of claim 14 wherein the analyzer quantifies vaporizable oil and gas.
17. The apparatus of claim 16 wherein the analyzer quantifies the bitumen.
18. The method of claim 17 wherein the analyzer quantifies the bitumen using nuclear magnetic resonance.
Type: Application
Filed: Jan 15, 2010
Publication Date: Jul 21, 2011
Applicant: Schlumberger Technology Corporation (Cambridge, MA)
Inventors: Neil Bostrom (Belmont, MA), Gabriela Leu (Cambridge, MA), Andrew E. Pomerantz (Lexington, MA), Robert Kleinberg (Cambridge, MA)
Application Number: 12/688,398
International Classification: C10G 1/04 (20060101); C10C 3/08 (20060101);