US2969226A - Pendant parting petro pyrolysis process - Google Patents

Description

Jan. 24, 196,1

M. G. HUNTINGTON PENDANT PARTING PETROPYRDLYSIS PROCESS Sheets-Sheet 1 Filed Jan. 19. 1959 MP0. HZ

PRODI/c 11s' *J Mayan GHwzb' Z'om WASTE' GAS Jan. 24, 1961 M. s. HUNTINGTON PENDANT PARTING PETRO PYROLYSIS'PROCESS 2 Sheets-Sheet 2 o c @E A.

INVNTOR Morgan 6'. Hwzfffgofz ATTORNEKS7 PENDANT PARTING PETRO PYROLYSIS PROCESS Morgan G. Huntington, Washington, D.C., assigner to Pyrochenl Corporation Filed Jan. 19, 1959, Ser. No. 787,755

S Claims. (Cl. 262-3) This invention relates to the in situ pyrolysis and recovery of insoluble and/or viscous hydrocarbons from initially impervious and impermeable sedimentary irnpregnations such as the Colorado oil shales, and 1t particularly relates to the method whereby frequently repeated pendant parting of the pyrolyzed rocks insures the ow of thermal carrier fluid close against the impermeable, retreating, unpyrolyzed front.

Oil shales which occur, for example, in Colorado, Utah and Wyoming, contain potentially liquid hydrocarbons many times greater than the known petroleum reserves 1n continental United States. These kerogen-impregnated fresh water marls known as the Green River formation constitute one of the greatest single non-coal deposits of potentially liquid hydrocarbon in the world and have approximately four times the total estimated reserve potential of all the oil pools in the Middle East combined.

Many attempts and known prior proposals have been directed to producing salable petroleum commodities by in situ recovery of oil from the oil shale. However, none of the known prior proposals have been commercially successful.

There are a number of problems involved in the situ recovery of the petroleum products of oil shale which contributed to the failure of the prior attempts at in situ recovery. These problems are created mainly by the nature of the oil shale, which is a kerogen impregnated material that is dense, practically impervious to fluids, and contains only about one percent moisture. Further, formations of oil shale although dense and impervious, contain planes of weakness.

The character of oil shale thus creates problems for in situ recovery by a thermal carrier uid which must be overcome to provide a workable process. First of all, it is necessary to afford free entry and controlled circulation of some thermal carrier uid at requisite temperatures to heat the massive shale formation to above 800 F. Following destructive distillation of the shale when heated by the thermal carrier fiuid, the products carried by the thermal carrier fluid must not be heated too greatly or indiscriminate cracking will occur. Also, initially impervious oil shale formation becomes porous following destructive distillation and therefore can hold and absorb condensed products of pyrolysis. Hence, crude shale oil will tend to recondense and remain in the cooler portion of the porous pyrolyzed rock. This invention relies on a novel process which overcomes all of the aforesaid problems. Among the objects of this invention are the following:

To provide a method whereby initially impervious and impermeable oil shales and other hydrocarbon impregnations may be pyrolyzed in situ and whereby substantially all of the :duid products of pyrolysis may be recovered.

ments may be raised in temperature to above 800 F States Patent O by a lthermal carrier medium which itself is below 1300 F.

To provide a means whereby the kerogen will be pyrolyzed and expelled from the host rocks in the vapor phase and yet which will insure against the indiscriminate cracking of the vaporized products of pyrolyzation.

To provide a means of absolutely preventing the reimpregnation of already calcined porous strata by the products of pyrolysis.

To provide a method whereby the strata may be frequently and repeatedly parted in order that the flow of thermal carrier fluid be always directed close against the retreating, impermeable, unpyrolyzed front.

To provide a means whereby unpyrolyzed strata cannot inadvertently part by becoming pendant due to the development of interplanar pressures.

To provide a means whereby the vaporized products of destructive distillation are promptly driven from the formation and conveyed to the surface at temperatures which still may be above 700 F.

To provide a means whereby partial hydrogenation may be accomplished coincidentally with pyrolysis and whereby practically all of the sulphur will be combined as hydrogen sulphide and part of the nitrogen will be recoverab-le as ammonia and whereby Various unsaturated organic compounds will be hydrogenated in varying degrees. At the same time, and as a result of such mild hydrogenation, normal retort yields of liiquid oil will be increased and the fixed carbon ordinarily remaining upon the inorganic host will substantially diminish.

To pyrolyze and recover distillable hydrocarbons from any selected bed at any depth beneath the surface.

To produce a superior grade of shale oil at approximately half the overall cost of any method which incorporates mining, retorting and calcine disposal.

Other objects of this invention will be pointed out in the following detailed description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principles of this invention and the best mode which has been contemplated of applying these principles.

In the drawings:

Figure 1 is a sectional elevation view of a rolling oil shale stratum to which the recovery method of this invention has been applied, and a schematic illustration of the above ground apparatus for carrying out the preferred form of the invention.

Figure 2 is a sectional elevation of an oil shale stratum on a larger scale illustrating the retreating unpyrolyzed front, pendant parting, and hot water flood of the calcine.

Figure 3 is a schematic plan of a field showing one possible location of the various wells illustrated in Figures 1 and 2.

In general, this invention consists of a method of in situ pyrolysis of oil shales by introducing through bore holes a pressurized heated fluid, such as steam with hydrogen or oxygen added thereto for hydrogenation and/or combustion purposes, and forcing the heated iluids through a pressure-parted plane of weakness in 'the formation from injection bore holes to production wells. In the passage of the thermal carrier fluids from the injection holes to the production wells, the sensible heat of the fluid is transferred to the surrounding oil shale by conduction whereupon pyrolysis and vaporization of the kerogen occurs, and resulting hydrocarbon vapors being expelled from the host rock are entrained in the carrier tluid. The carrier Huid and the hydrocarbon entrained therein are passed to production wells through the plane of weakness which is held open by the pressure 'of the carrier fluid. Upon emerging from the production wells, the hot carrier fluid and its entrained hydrocarbon vapors are separated and the heat of the carrier uid is partially recovered in a primary thermal circuit. To prevent large sections of the unpyrolyzed oil shale formation from becoming pendant and parting during pyrolyzation, a higher plane of weakness in the formation is vented and the strata of oil shale between the vented and parted planes of weakness is rendered relatively impermeable. Thus, when the hot carrier uid acts upon the lower surface of the formation at the pressure parted plane, no large unpyrolyzed chunks of the stratum will part, as they will be continually held up by the carrier uid at high pressure until they have been pyrolyzed, and, at that time, the porous calcine will become pendant and will part from the unpyrolyzed oil shale and drop to the bottom of the pressured parted plane. In this manner, the unpyrolyzed front of the oil shale continually retreats upwardly toward the vented plane of weakness of the shale. Reimpregnation of the porous parted calcine is prevented by a hot water flood.

Referring to the drawings for an explanation of the process, at the beginning of the exploitation of any oil shale bed, a plurality of production, injection and water flood control wells are first drilled, cased and sealed olf a short distance above the shale oil bed. These wells are designated P (production), I (injection) and W (water flood control) in Figures 1 and 2. Then, all these wells are drilled ten to fifty feet below the shale bed base, and the formation from below the bed at this point to about the same distance above the bed is thoroughly grouted and sealed in order to render the stratum to be exploited and its immediate surroundings impervious at rock pressures. The production, injection and water ood control wells P, I and W, are then cased and cemented or otherwise effectively sealed from the base of the bed of the oil shale to an initial sealing packer, ten to fifty feet above the oil shale bed, and this sealing is accomplished at near rock pressures to insure against any leakage upwardly along the casings.

During the drilling of the injection and production holes, cores are taken and the stratum is carefully logged, particular attention being paid to the natural planes of weakness throughout the oil shale bed. Such planes of weakness are identified in Figures l and 2 as 10 and 12.

Pressure relief holes R are then drilled at Strategic points to within a few feet above the base of the bed or just above the horizon which is to be initially parted. The pressure relief holes are cased and sealed off just above the bed, as are the other wells described above. The relief holes are then perforated 16 at a rst major plane of weakness above a selected initial parting plane of weakness 12 at the basev ofthe bed to be exploited.

The injection and production well casings are then perforated 14 at the base of the oil shale bed on the same selected plane of weakness 12, and a iuid is pumped into each individual well under pressure just slightly below that calculated to cause the base of the bed to part by hydraulically lifting the entire overburden. This maximum hydraulic pressure is equal to the static weight of any column of rock and is termed the rock pressure. The calculated rock pressure may be attained in a hydraulic system by sealing the formation with bentonite mud or some other sealing medium. Any sealing fluid leaking into the next above plane of weakness will be pumped out until sealing becomes effective between the selected parting plane of weakness 12 below and the vented plane of weakness 10 above. The relief holes which are in communication with the selected plane of weakness 10 above the parted plane of weakness 12 will then vent the parted plane of weakness and the stratum therebetween will be suiciently impermeable to, in effect, vbecome a lifting diaphragm.

Upon achieving the sufficient sealing of the intervening layer between the parting plane of Weakness 12 and the vented plane 10 in the stratum, an increase above the calculated rock pressure in uid injected through perforations 14 will then cause the formation to part at the parting plane of weakness 12 and lift the exact selected plane of weakness at the casing perforations 14. Flow may then be proven between any of the injection and production holes I and P in the parting pattern.

After these preliminary operations, the in situ pyrolysis and pendant parting of the impermeable hydrocarbon impregnations may begin by continuously introducing a thermal carrier uid such as steam at a temperature suicient to cause pyrolysis, Le., 700 to 1400" F., and a pressure above the rock pressure into the injection holes through perforationsV 14.

The introduction of the thermal carrier uid, which in the preferred embodiment is steam, causes the pyrolysis of the formation at the pressure-parted plane 12 of the formation, and the hydrocarbon vapors are entrained in the thermal carrier lluid and passed out the production wells P. The ow out of the production wells P is controlled by valving 18 such that there will be an equal distribution of flow from the production wells P which may be supplied from the same injection well I. As the pyrolysis proceeds upward and the shale becomes somewhat pervious, the pressure exerted by the thermal carrier fluid, which is at rock pressure, is transferred progressively upwards always against the impervious stratum; hence, as the hydrocarbon of the impregnation is forced out, the calcined host rock 22 becomes pendant and automatically and repeatedly parts or falls from the upward retreating unpyrolyzed front 20. Thus, the thermal carrier uid is continually directed against the fresh, cold oil shale and the heat transfer by conduction is rapidly effected.

The calcine 22 which has fallen from the unpyrolyzed front is continually covered by hot water flood 24 which is introduced through the water ood control well W. This well is perforated 21 at the bottom of the stratum and water is introduced therein at a controlled rate so that the calcine will almost be covered. This prevents re-impregnation of the already calcined porous strata by the products of pyrolysis. To accomplish this hot water ood it is desirable to occasionally reperforate 25 at the level of the unpyrolyzed front 20. Y

Because the plane of weakness 10 above the unpyrolyzed front 20 is vented, no pressure can build up above the unprolyzed front 20 or the selected plane of parting 12, and therefore, no large slab or chunk of the unpyrolyzed oil shale can indavertently become pendant and part from the pressure-supported mass. However, as the pyrolysis advances upward, the relief holes R will bleed an increasing amount as the thermal carrier fluid at rock pressure gets closer and closer to the ven-ted plane of weakness 10. When the advancing front of pyrolysis 20 has reached the vented plane of weakness and ow through the relief vholes R becomes excessive, the pressure of the thermal carrier fluid is dropped to the point where there is no ow through the relief holes and the relief holes are then cemented to the next higher plane of weakness (not shown) and the relief hole casing is then reperforated at this next higher plane of weakness to insure adequate venting. This may be accomplished in successive steps to as many planes of weakness as are necessary and occur in the stratum. If it is necessary to insure adequate venting of the Vented planes of weakness, each succeeding plane of weakness may be pressure-parted to some extent from the relief holes R.

vIt is desirable that an oil shale recovery process in corporate hydrogenation, and the process of this invention may incorporate mild hydrogenation coincidental with the situ pyrolysis to increase the total amount of organic soluble products, and to remove most of the sulphur as hydrogen sulphide and part of the nitrogen as ammonium. The hydrogenation may be accomplished by introducing manufactured hydrogen into the superheater tubes of the boiler and passing these gases with the steam at rock pressure into the formation through the injection wells I; see Figure l. Mild in situ hydrogenation may also be accomplished by manufacturing hydrogen in situ by injecting oxygen into the steam and oxidizing residual carbon on the pyrolyzed shale and using this hydrogen for hydrogenation as explained above. The hydrogenation may be aided by the introduction of a catalyst of the metallic fume or soluble salt type into the carrier gas Ias indicated in Figure l.

The choice of whether to inject hydrogen into the boiler super-heater tubes with the steam and thus provide a hydrogen-rich carrier gas from an outside source, or whether to inject oxygen with the steam to provide a means of oxidizing a residual carbon on the pyrolyzed shale and thus to manufacture hydrogen in situ, or whether to do neither, is a matter of economic decision. In the preferred embodiment of this invention, any one of these three operations or none of them may be done.

The hot carrier -uid and its entrained hydrocarbon vapors and oil shale mists are passed out of the formation and upward from the production wells P through a heat exchanger or condenser 26 and the condensates are led through pipes 2S to fractionating towers 30 where the products of pyrolyzation and coincidental hydrogenation are conveniently fractionated according to the boiling ranges. Ammonium and hydrogen sulphide and carbon dioxide may be removed from the uncondensable gases. The fuel gas is passed to the boiler to be burned to supply energy for the process. In condenser 26, the cold fluid may be water which is being supplied to the boiler. A large portion of the heat of the carrier gases and entrained hydrocarbons is transferred to the boiler feed water during this opera-tion, thus effecting a considerable heat economy.

In actual practice, the production and injection wells P and I may be drilled on a hexagonal pattern as shown in Figure 3, such that the spacing along the legs between the wells will range from fifty to two hundred feet or farther, depending upon the character of the oil shale stratum. The water flood control wells W are drilled near the lowest point of the stratum so that the water may be always introduced from below the pyrolyzed front. The relief holes R may be drilled between the injection and production wells as needed. Each injection well I will occupy the relative center of each hexagon, and six production wells form the periphery. If drilled according to this embodiment, one injection well would force the thermal gas to as many as six production wells, and flow from the individu-al production well may be controlled by suitable valves 18 at the surface.

As shown in Figure l in rolling strata and having planes of weakness which deviate markedly from the horizontal, the injection wells must be down-slope from the production wells, because a static pressure of the rock must necessarily increase down slope with increasing rock depth. To exploit folded and/or rolling strata, the injection holes are always drilled in the troughs of the synclines and the production holes are always o-n the crest of the anticlines. The thermal carrier fluid, in general, is readily forced from the injection wells to production wells in the direction of descreasing rock pressures.

While there has been shown and described and pointed out the fundamental novel features of this invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and change in the form and details of the process illustrated and described may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims and reasonable equivalents thereof.

What is claimed is:

l. An in situ method :of winning shale oil from oil shale that comprises: fracturing the impermeable formation of oil shale at a plane of weakness therein, venting a higher level natural plane of weakness in the formation, introducing a fluid into the formation along the parted plane of weakness, said uid being at a temperature sufficient to pyrolyze the oil shale and at a pressure equal to or slightly greater than the rock pressure, whereby the sensible heat of the fluid is tranferred to the surrounding oil shale formation and pyrolysis and vaporization of the oil shale occurs, and recovering the uid with hydrocarbon vapor products of pyrolysis entrained therein.

2. A process for the recovery of shale oil from a subsurface oil shale formation that comprises: pressureparting an initially impervious and impermeable for mation of oil shale in situ near the lower portion thereof, venting a higher plane of weakness in the formation,

l introducing a thermal carrier fluid into the formation at the parted plane of weakness, the carrier fluid being at a temperature between 700 and 1400" F. to pyrolyze the oil shale and a pressure above the rock pressure, to support the layer of oil shale between the parted plane and the vented plane of Weakness and prevent any large piece thereof from parting therefrom before it is pyrolyzed, whereby the initially impervious and impermeable oil shale will be pyrolyzed and lthe hydrocarbon products thereof will be entrained in the carrier fluid, thereby causing an unpyrolyzed front of the oil shale to retreat upwardly and the calcine of the pyrolyzed shale to become pendant and repeatedly part from the unpyrolyzed front, and passing rthe thermal fluid and entrained hydrocarbons to the surface and separating the same.

3. A process for in situ pyrolysis and pendant parting of impermeable hydrocarbon impregnations, the process comprising: drilling at least one injection well and one production well to provide access to a formation of an impermeable hydrocarbon impregnation, pressure-parting the formation at a plane of weakness along the lower portion thereof, Venting a natural plane of weakness in the impermeable hydrocarbon impregnation formation above the pressure-parted plane, introducing a thermal carrier fluid into the injection well, the thermal carrier fluid being above rock pressure and at a temperature sufficient to pyrolyze the impermeable formation, passing the thermal carrier fluid through the pressure-parted plane of weakness to pyrolyze the impermeable formation and entrain hydrocarbons therein and thereby causing an unpyrolyzed front of the formation to retreat upwardly, thus causing pyrolyzed porous calcine to become pendant and repeatedly part from the unpyrolyzed front, and recovering the carrier fluid entrained with the hydrocarbons at the production well.

4. A process as defined in claim 3 further comprising: preventing re-impregnation of the pendant-parted porous calcine by the products of pyrolysis by partially covering the porous calcine by a hot water flood.

5. A process as defined in claim 3 further comprising: mildly hydrogenating the impermeable hydrocarbon impregnation formation in situ coincidental with the recovery of the hydrocarbon vapors from the formation by injectilng manufactured hydrogen into the thermal carrier 6. A process as defined in claim 3 further comprising mildly hydrogenating the impermeable hydrocarbon impregnation by injecting manufactured oxygen into the carrier gas, whereby the oxygen will produce hydrogen in situ for the mild hydrogenation operation.

7. A process as defined in claim 5 further comprising: catalyzing the hydrogenation by injecting a catalyst into the carrier fluid.

8. A process as defined in claim 3 wherein the in situ pyrolysis is accomplished in a rolling formation, the process further comprising: drilling the injection wells at the troughs of the synclines of the formation and drill- -7 ing the production wells at the crests of the antiolines 2,825,408 of the formation. 2,838,117

References Cited in the le of this patent UNITED STATES PATENTS 5 FH6520 1,422,204 Hoover et al. July 11, 1922 `S Watson Mar. 4, 1958 Clark et a1. June 10, 1958 FUREIGN PATENTS Great Britain Oct. 13, 1954

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