US 3601193 A
Description (OCR text may contain errors)
United States Patent Guide 0. Grady Tulsa, Okla.
Apr. 2, 1968 Aug. 24, 1971 Cities Service Oil Co. Tulsa, Okla.
 Inventor [21 1 Appl. No.  Filed  Patented  Assignee [54} IN SITU RETORTING OF OIL SHALE 12 Claims, 2 Drawing Figs.
 11.8. C1 166/245, 166/247, 166/259, 166/269, 166/270, 166/272  Int. Cl. E2lb 43/24, E2 lb 43/26  Fieldofsearch 166/1l,36, 39, 40, 42, 269, 256-262, 268, 270, 271, 272, 302, V 303, 305, 308, 247, 245
 References Cited UNITED STATES PATENTS 1,269,747 6/1918 Rogers 166/39 UX 2,974,937 3/1961 Kiel 166/11 X 2,975,834 3/1961 West et al. 166/38 X 3,017,168 1/1962 Carr 166/11 X 3,024,013 3/1962 Rogers et a1. 166/11 3,223,158 12/1965 Baker 166/11 3,228,468 1/1966 Nichols 166/11 3,233,668 2/1966 Hamilton et a1. 166/11 X 3,270,813 9/1966 Gilchrist 166/38 X 3,342,257 9/1967 Jacobs et a1. 166/36 Primary Examiner-Stephen J. Novosad Attorney-l. Richard Geaman ABSTRACT: Initiation and support of the in situ retorting of oil shale is accomplished by injecting the retorting fluid at a multiplicity of points along a substantially horizontal plane in the chimney created by a nuclear explosion. The retorting fluid is injected through an injection well extending generally horizontally in the chimney, preferably in the uppermost portion thereof. A series of such injection wells may be employed in order to provide for the distribution of the retorting fluid substantially across the cross-sectional area of the chimney.
PATENTED Aus24|97| 3601.193
INVENTOR GUIDO o. GRADY FIG-1 Z ATTORNEY IN SITU RETORTING OF OIL SHADE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the recovery of hydrocarbons from oil shale. More particularly, it relates to the recovery of shale In situ recovery techniques are likewise confronted with significant problems. Such techniques have not been successful in recovering economical amounts of shale-oil from the massive oil shale deposits that often are covered by an appreciable overburden. The very low natural permeability of oil shale has been a significant factor in the relative ineffectiveness 'of in situ retorting techniques. The oil shale must be extensively fractured or broken up into a rubble of relatively high and uniform permeability in order to permit a relatively uniform heat permeation throughout a substantially impervious natural retorting chamber so as to release substantially all of the available shale oil from the area being treated.
The use of a nuclear explosive device placed near the bottom of the oil shale formation has been proposed. Upon detonation of such a device, a large, substantially spherical hollow cavity would be created instantaneously. This cavity would be surrounded by a thick zone of fractured but nevertheless impervious shale or rock. The fractured rock located above the cavity would collapse so as to at least partially fill the cavity. Thus, a substantially cylindrical retortlike zone or chimney filled with crumbled and pervious oil shale would result. Such a technique is described, for example, in the Jacobs et al. patent, U.S. Pat. No. 3,342,257 issued Sept. 19, 1967.
The retorting of the shale in the chimney thus fonned may be initiated and supported by drilling gas inlet and oil recovery wells to connect the chimney with on-surface gas-pumping and shale oil recovery equipment. A hot or heated gas can thereafter be passed through the'chimney of crumbled pervious shale, preferably in a downward direction, so as to decom pose the hydrocarbons existing in the deposit in the form of kerogen and to distill shale oil from the shale in the chimney.
The shale oil is collected and flows to the surface through the production well.
, This technique offers distinct advantages over the methods I heretofore considered. Nevertheless,"the 'efi'ectiv'eness of this technique is dependent on the success with which retorting of the oil shale in the relatively large chimney space can be accomplished. As a retorting gas is injected into the chimney through a gas inlet well connecting the chimney with the gaspumping equipment at the surface, a hot zone of sufficient temperature to support retorting is formed in the vicinity of the injection point. This hot zone can be advanced by the injection of. additional retorting gas through the injection well. Initiating and supporting retorting of the shale in the chimney in this manner is not entirely satisfactory, however, because of the difficulty encountered in initiating and advancing the hot zone throughout the entire chimney volume. In the absence of satisfactory retorting throughout the chimney, the recovery of shale oil from the chimney will be unduly restricted, and the economic feasibility of utilizing this technique will be diminished.
It is an object of the present invention, therefore, to provide an improved process for the in situ retorting of oil shale formations.
It is an object of the present invention to provide a process These and other objects are accomplished by the novel process of the present invention as hereinafter set forth.
SUMMARY OF THE INVENTION mits and facilitates the establishment of a hot zone substantially across the cross-sectional area of the chimney. This is accomplished by injecting the retorting fluid into the chimney space by means of at least one injection well positioned generally horizontally across the chimney. The retorting fluid is injected through perforations in the injection well liner.
The injection of a retorting fluid into the chimney from a multiplicity of points permits the establishment of a hot. zone at a temperature sufficient to support retorting across substantially the entire width of the chimney. By injecting retorting fluid through a series of injection wells thus positioned, the establishment of the desired hot zone substantially across and around the entire cross-sectional area of the chimney may be accomplished.
The support and advancement of thehot zone throughout the chimney face can readily be accomplished by continued injection of the initial retorting fluid or a suitable gas into the injection wells and consequently into and around the crosssectional area of the chimney. The injection wells called for herein may be positioned either in the upper or the lower portion of the chimney, with the distilled shale oil being recovered through production wells in accordance with normal techniques.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully described hereinafter with reference to the attached drawings in which:
FIG. I is a side elevational view, partially in cross section, showing the relative'positions of an injection well and a DETAILED DESCRIPTION OF THE INVENTION In order to initiate and support retorting of the shale across and around the chimney formed by the detonation of a nuclear devicein a subsurface inan oilshale formation,'at least one injection well is positioned so that it extends generally horizontally across the width of the chimney. The injection well liner contains perforations through which the retorting fluid may be injected into the chimney. The retorting fluid is used to establish a hot zone in the chimney at a temperature capable of supporting retorting of the shale. The projectionof the retorting fluid through a series or multiplicity of perforations in the generally horizontally extending injection well liner facilitates the establishment'of a hot zone substantially across the width of the chimney. Injection of the retorting fluid through a generally vertically positioned injection well extending into the chimney would, on the other hand, result in the establishment of a more localized hot zone in the vicinity of the injection well outlet. Even with the use of very high injection volumes. the extending of the hot zone substantially across the width of thechimney would be difficult to uccomplish. The present invention, therefore, permits the establishment and support of a hot zone that enhances the retorting of the shale and the recovery of the shaleoil from the chimney.
The injection well called for by the present invention can be provided by known drilling techniques. The injection well is drilled preferably as a slant well by the so-called slant-hole drilling technique. Details of this drilling technique, which involves tilting the drilling rig, are not included herein as this drilling technique is known and has been employed in conjunction with conventional petroleum-producing methods.
It is also possible to provide one or more injection wellbore holes that extend downward from the earths surface in a generally vertical direction with radially diverging bore hole extensions extending into the chimney and across the chimney in a generally horizontal direction. The so-called directional drilling technique can be employed to provide the deviating bore hole extensions. Since directional drilling is also a well established technique that has been employed in conventional operations, further details of the manner in which the drilling is accomplished are not included herein.
In order to provide means for injecting the retorting fluid generally across the width of the chimney, perforated liner extensions may be employed in the portion of the injection well passing through the chimney. Altemately, plain liner extensions may-he employed and perforations may be-made after the liner leaving been placed. Techniques for perforating the concentrated after it has been positioned in the formation are well known in the, art. For example,'pressure may be employed to blow out plugs in the liner or perforations may be made by chemical action.
1 injection of the retorting fluid into the chimney space may be accomplished through one or more injection wells. Each well, of course, preferably will have a generally horizontally extending portion in the chimney. While one such injection well provides a series of injection ports across the width of the chimney, it may be desirable to employ two or more of such injection wells in order to more fully cover the cross-sectional area of the chimney. From about two to about six injection wells would normally be sufficient for this purpose although additional injection wells could also be employed. Coverage across and around the cross-sectional area of the chimney can conveniently be achieved by positioning four injection wells at intervals at about 45 around the circumference ofthe chimney. By extending each of these wells substantially across the width of the chimney, thus crossing at the center portion of the chimney, a multiplicity of injection ports can be provided around the cross-sectional area of the chimney.
The various injection wells waste be positioned across the chimney at various elevations if desired. Generally, however, the injection well or wells will be positioned near the top of the chimney. The injection wells can, however, be positioned near v the bottom of the chimney or at some intermediate position in either the upper or lower portion of the chimney. it is also within the scope of'the present invention to inject the retorting fluid sequentially through injection wells positioned at more than one elevation in the chimney in order to facilitate the recovery of shale oil from the chimney space.
In FIG. 1 of the drawing, the chimney of fractured and crumbled shale of high permeability is represented by the numetal 1. This chimney is formed by the detonation of a nuclear device generally positioned at the bottom of oil shale formation 2. Access well 3, which is drilled from surface 4 through overburden S and into oil shale formation 2 is employed initially in order to place the nuclear device in position for detonation. Tilted drilling rig 6 may be employed for the drilling of production well 7 positioned at the base of chimney 1. This drilling rig may also be employed in the drilling slant injection well 8 that is positioned in the upper portion and near the top of chimney 2. As can be readily seen from the drawing, injection well 8 is drilled so that tn that extends across chimney 2 is positioned generally horizontally. Perforations generally represented by the numeral 9 are provided in the portion of injection well 8 extending across the chimney to provide suitable injection ports for the injection of retorting fluid substantially across the width of the chimney.
FlG. concentrated illustrates an embodiment of the present invention in which four injection wells are positioned in a radial pattern around chimney 2. The four wells are positioned at 45 intervals around the chimney, Each well extends across the width of the chimney and is provided with perforations on substantially the entire portion crossing said chimney. This arrangement provides for a multiplicity of injection ports substantially around and across the cross-sectional area of the insufficient to retort any appreciable portion of the available and recoverable oil in the chimney. The retorting fluid, therefore, is injected into the chimney in order to heat the chimney space to a sufiicient temperature to support combustion. The retorting fluid may be any suitable material or combination of materials that will provide the necessary heat to establish retorting conditions in the chimney. The retorting fluid may conveniently comprise a combustion gas formed by burning a combustible-containing gas, such as methane or natural gas, with air or some other oxygen-containing gas. it is within the scope of the present invention to burn a combustible gas or liquid aboveground to form the combustion gas or to inject the combustible gas or liquid together with an oxygen-containing gas into the formation through the injection well so as to form the combustion gas underground. It is also within the scope of the invention to employ some other gas, such as a heated oxygen-free gas or steam as the retorting fluid.
The retorting fluid injected through the perforations in the generally horizontally extending injection well supports the hot zone formed across the width of the chimney, by'conventionai ignition or burning at the injection points, i.e. at the perforations, along the generally horizontally extending portion of the injection well in the chimney. While the temperature required in the hot zone in order to support combustion varies with the pressure in the chimney space, at temperature of at least about 600 F. is ordinarily required at atmospheric pressure. Hot zone temperatures between about 700 F. and about 2500 F. may conveniently be employed.
The amount of retorting fluid employed in the practice of the present invention is not critical and will vary depending on a number of factors, such as the retorting temperature employed, the extend of oil recovered, the initial shale temperature and the like. Retorting gas quantities of from about 20 to about 5,000 standard cubic feet into the relatively cool shale formation per cubic foot of crumbled shale in the chimney have been proposed although the size of the chimney developed will greatly influence the actual amount employed.
In another embodiment of the present invention, the hot zone may be established by the reaction of chemicals in the chimney, other than by combustion, so as to generate the desired quantity of heat. For example, magnesium pellets may be injected into the chimney, together with water or other suitable carrying medium, through the perforations in the generally horizontally extending injection wells. HCl may then be injected into the chimney through the same perforations so as to contact and react with the pellets. Such a technique would not only furnish the resultant heat of reaction, but would have an additional advantage as well. The reaction would result in the evolution of hydrogen that would tend to hydrogenate the kerogen in the chimney, thus tending to upgrade the shale oil recovered from the chimney. Numerous other reactants will readily occur to those skilled in the art as suitable for injection into the chimney to provide, by means of their heat of reaction, the heat necessary to support tants employed, the injection of the reactants through the perforations of the generally .horizontally extending injection wells of the present invention permits the establishment of the hot zone substantially across and around the cross-sectional area of the chimney.
After the hot zone has been established, it may be advanced in the desired direction by continuous or intermittent injection of a gas that advances the heat front through the chimney. Air or another oxygen-containing gas can conveniently be employed for this purpose. The oxygen content and rate of flow of the gas, together with the amount of residual combustibles in the formation, will determine the temperature and the rate at which the heat wave is propogated through the chimney.
It has been suggested that a nuclear detonation may be used in the recovery of oil from Athabasca tar sands and similar formations as well as from oil shale formations as disclosed herein. Recovery procedures would follow essentially the same pattern as in the recovery of shale oil. The present invention could also be employed in this procedure in a similar manner as set forth herein.
In yet another embodiment, the horizontally extending injection wells disclosed herein may be employed in the retorting of oil shale substantially across an area of fractured and crumbled shale formed by the detonation of conventional explosive device.
While the present invention has been described with reference to particular embodiments thereof, it will be appreciated that various changes and modifications can be made therein without departing from the scope of the invention as set forth in the appended claims.
1. In the recovery of shale oil from a subsurface oil formation by means of a nuclear explosion that creates a cavity in the formation that fills with collapsing oil shale to form a chimney of fractured and crumbled shale of high permeability from which shale oil is recovered through a production well, an improved means of initiating and supporting in situ retorting of the oil shale comprising injecting the retorting fluid into the chimney through perforations in the liner of four injection wells positioned at approximately 45 intervals along the periphery of the chimney area and extending generally horizontally in the chimney and recovering the shale oil through at least one production well positioned in the chimney, whereby the retorting fluid is injected substantially across the width of the chimney so as to facilitate in situ retorting throughout the chimney.
2. The method of claim 1 in which said retorting fluid is injected into the upper portion of the chimney and shale oil is recovered from the lower portion of the chimney.
3. The method of claim 1 in which the injection wells are positioned in a parallel configuration across the width of the chimney.
4. The method of claim 1 in which said generally horizontally extending injection wells cross one another so as to provide a multiplicity of injection points throughout the crosssectional area of the chimney.
5. The method of claim 1 in which the retorting fluid comprises the hot combustion products obtained by burning a combustible fluid with an oxygen-containing gas.
6. The method of claim 5 in which said combustion products are formed above ground and are injected into the chimney through said injection wells.
7. The method of claim 5 in which said combustion products are formed below ground by burning the combustible fluid with an oxygen-containing gas after injection into said injection wells.
8. The method of claim 1 in which the retorting fluid comprises steam.
9. The method of claim 1 in which the retorting fluid comprises a gas heated to at least retorting temperature.
10. The method of claim 1 in which saidretorting fluid is injected into the chimney until a hot zone is established therein of sufficient temperature to support combustion and including the subsequent injection of an oxygen-containing gas through said injection wells to advance the hot zone through the chimney.
11. The method of claim 1 in which the retorting fluid comprises chemical reactants injected into the chimney, said reactants being such that upon contact in the chimney a heat of reaction will be generated so as to furnish the heat necessary for retorting the fractured and crumbled shale in the chimney.
12. The method of claim 1 in which the retorting fluid is injected sequentially through said injections wells positioned at more than one elevation in the chimney space.