In-situ retorting of carbonaceous deposits

United States Patent D9]

Kvapil et al.

[ii] 4,162,808 [45] Jul. 31,1979

[54] IN-SITU RETORTING OF CARBONACEOUS DEPOSITS

[75] Inventors: Rudolph Kvapil, Denver; K. Malcolm Clews, Littleton, both of Colo.

[73] Assignees: Gulf Oil Corporation, Pittsburgh, Pa.;

Standard Oil Company (Indiana),
Chicago, 111.

[21] Appl. No.: 908,798

[22] Filed: May 23,1978

[51] Int. CI.* E21C 41/12

[52] U.S. CI 299/2; 166/259

[58] Field of Search 299/2; 166/259; 175/12

[56] References Cited

U.S. PATENT DOCUMENTS

3,349,848 10/1967 Burgh 166/259

3,917,344 11/1975 Janssen et al 299/2

3,950,029 4/1976 Timmins 299/2

Primary Examiner—Ernest R. Purser

[57] ABSTRACT

A method of producing fluid fuels from carbonaceous deposits such as oil shale, heavy oils and coal by in-situ retorting of the carbonaceous deposit in rubblized insitu retorts utilizes a plurality of such retorts. The retorts are subjected to a sequence of preparation for rubblization, rubblization and combustion of carbonaceous material to supply heat to produce a fluid fuel from kerogen in the carbonaceous deposit. At least one completely rubblized retort is maintained throughout its entire volume under the inlet pressure of the combustion air between retorts in which rubblization or stopping is taking place and retorts in which the combustion of the carbonaceous deposit is proceeding to prevent flow of toxic gases from the retort in which combustion is proceeding to a retort in which preparation for rubblization and rubblization are occurring. The invention is described in detail for the recovery of shale oil from oil shale deposits.

13 Claims, 3 Drawings

1

IN-SITU RETORTING OF CARBONACEOUS
DEPOSITS

BACKGROUND OF THE INVENTION 5

1. Field of the Invention

This invention relates to the in-situ retorting of carbonaceous deposits to produce fluid fuels, and more particularly to an improved method of producing such fuels in which danger of exposing workers to toxic ^ gases is minimized.

2. Description of the Prior Art

Immense potential sources of carbon-containing compounds suitable as fluid fuels exist in subsurface carbonaceous deposits of oil shale, coal, and heavy, highly 15 viscous petroleum oils. The highly viscous petroleum oil deposits are frequently referred to as tar sands. Because the carbonaceous material in the deposits is either solid as in oil shale and coal or highly viscous as in tar sands, treatment of the carbonaceous deposit to make 20 the carbon-containing compounds fluid is necessary to deliver them from the deposit to the surface. A method of treatment that has been used is to heat the deposit to a temperature at which fluid carbon-containing compounds are formed or the viscosity of heavy oils is dras- 25 tically reduced. One method of heating the deposit is by in-situ combustion in which a portion of the carboniferous material in the deposit is burned in place by igniting the deposit and injecting air into the deposit to heat oil shale or tar sands to a temperature at which oils of low 30 viscosity are produced or to produce combustible gaseous products from coal.

The very low permeability of oil shale to the flow of fluids makes it necessary to rubblize the shale to form an in-situ retort through which fluids for heating the shale 35 to a temperature high enough to convert the kerogen to shale oil can be circulated. While sometimes coal and tar sands may be sufficiently permeable for an in-situ combustion process, rubblization of those deposits can be advantageous in reducing channeling through the 40 deposits. One of the methods of forming an in-situ retort is described in U.S. Pat. No. 1,919,636 of Karrick. In the process described in that patent, a vertical central shaft is driven through the oil shale to provide the desired void space necessary for permeability and the oil shale 45 is blasted from the walls of the shaft to fill the shaft with broken oil shale. Other mining procedures for forming a rubblized in-situ retort are described in U.S. Pat. Nos. 2,481,051 of Uren, 3,001,776 of Van Poollen and 3,661,423 of Garrett. Those patents suggest using van- 50 ous mining techniques such as sublevel stoping, sublevel caving, block caving and shrinkage stoping to form the in-situ retort.

It is necessary during the in-situ retorting of oil shale to introduce the combustion air into the retort at a pres- 55 sure substantially above atmospheric pressure to force the air through the retort at a rate high enough to maintain combustion of oil shale in the retort. The large volume of gases that must pass through the retort and the height of the retort cause a substantial pressure drop 60 in the gases as they travel from the combustion air inlet preferably at the top of the retort to the outlet of the retort at its lower end. If it were attempted to maintain subatmospheric pressure in retorts during the burning of oil shale, the volume of the gases drawn from the 65 retort would be excessive.

It is likely that there will be fractures in the oil shale formation that extend outwardly from rubblized retorts.

2

The fractures will in many instances be naturally occurring fractures in the formation that existed before the retort was constructed but may also be fractures formed during the rubblization. Since retorts are maintained at substantially atmospheric pressure while being prepared for rubblization and during the rubblization, there is danger of flow of gases from a retort that is in the process of retorting oil shale to retorts that are being prepared for rubblization or are in the process of being rubblized. Gases developed during the retorting are highly toxic and may develop explosive mixtures when mixed with air.

SUMMARY OF THE INVENTION

This invention resides in a method of producing fluid fuels by in-situ retorting of carbonaceous deposits in rubblized subsurface retorts in which a row of retorts is formed and the carbonaceous deposit is ignited successively in the retorts beginning in the retort at one end of the row and progressing toward the other end of the row. At least one completely rubblized retort exists at all times between a retort in which combustion is occurring and a retort in which rubblization or preparation of a retort for rubblization is occurring. The intervening rubblized retort is maintained at a pressure at least as high as the pressure at the inlet end of retorts in which combustion is proceeding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a portion of an array of retorts in a subsurface oil shale deposit.

FIG. 2 is a transverse vertical sectional view taken along section line II—II in FIG. 1.

FIG.. 3 is a longitudinal vertical sectional view taken along section line III—III in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT

For purposes of illustration, a preferred embodiment of this invention is described for the recovery of shale oil from oil shale deposits.

Referring to FIG. 1 of the drawings, a plurality of retorts 10,12,14 and 16 in a subsurface oil shale deposit are arranged in a row designated as row A. The retorts shown are of rectangular shape and horizontal cross section and are arranged end to end with the adjacent retorts separated by end pillars 18, 20 and 22. While only four retorts have been shown in row A in FIG. 1 to simplify the drawings, it is contemplated that a row of retorts will include more than four retorts, four retorts being adequate for a description of this invention.

As is shown in FIG. 2, the retorts may have a height that substantially exceeds their lateral dimensions. The height will depend upon the thickness of the shale deposits in which the retorts are constructed. In a typical installation in the shale deposits in Rio Blanco County, Colo., the retorts may have a width of 100 to 150 feet, a length of 100 to 300 feet, and a height of 400 to 750 feet. The end pillars will have a thickness in the range of 60 to 125 feet. The dimensions given are merely typical of a suitable retort design in a particular formation. This invention is not restricted to use in retorts of rectangular cross section or to retorts having any particular ratio of height to width or length.

Again referring to FIG. 2, a preferred retort structure is shown in which the ceiling 24 of the retort slopes downwardly from a peak 26 at an angle preferably in the range of 40° to 55° to intersect sidewalls 28 and 30