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r~ u ~~ 3,759,328 LATERALLY EXPANDING OR-SHALE PERMEABILIZATION CROSS REFERENCES TO RELATED APPLICATIONS This application is a confmuation-in-pan of copend- ing patent application Ser. No. 57;209 filed July 22, 1970, nou• abandoned. BACF:GROUND OF THE INVENTION The present invention relates to production of hydro- carbons and/or water soluble and/or heat unsitive min- erals from underground oil shale formations by con- trolled circulation of a hot aqueous fluid through said oil shale fotrtta[ion so as to vertically and horizontally expand a permeable zone of nibbled oil shale within said formation by leaching and recovering said miner- als from a relatively deep location within the treated area of the formation and thereafter injecting a pyro- lyzing fluid into the nibbled oil shale to effect pyrolysis and recovery of hydrocarbons therefrom. Various methods have been propoxd (or imparting permeability to underground oil shale formations such as fracturing by hydraulic or explosive means and/or acidization but they have proven [o be ineffective and- /or too expensive to use. Thus, oil shale formations which have been fractured on subxquent pyrolysis with pyrolyzing Fluid to effect oil recoven•, such frac- tures tend to close unless high p}•rolyzing fluid circula- tion pressures at least equal to the overburden pres- sure, are maintained and [his is difficult to do. Acidiza- tion of an oil shale formation is expensive and difficult to control. SUMMARY OF THE INVENTION ' The present invention is directed to an improved me[hod of recovering hydrocarbons and water-soluble carbonates andlor heat sensitive materials from under- ] ground oil shale formations containing substantial amounts of said carbonate andlor minerals b}• forming a cavem therein by leaching with an aqueous fluid said j carbonates andlor minerals and imparting permeability while cfiec[ing nibbling oC the oil shale in said vested area by contacting and flowing a hot aqueous fluid downward from a relatively shallow depth along a verti- cal interval of said treated oil shale to caux horizontal expansion and recovering from a relatively deep depth . an aqueous liquid containing dissolved therein water- : soluble carbonates and/or heat sensitive minerals and subsequently injecting a pyrolyzing fluid or solvent to effect reeovcry• of hydrocarbons from the nibbled oil shalt. 2 nificant amount of heat xnsicive minerals and/or water soluble carbonates a hot aqueous fluid can be caused to Flow along a park that cause a horizontal expansion of the ~a~~rn. >n a Cavem within such an oil shale, the i ra[e at which a hot aqueous fluid is xgregated into lay- ers having increasing densities, has been found to be related to the raze at which heat can be transferred into the walls of the cavem in a manner conducive to the es- ublishing and maintaining of the flow path deuribed 0 above, and the resultant heating and leaching along substantially vertical portions of the walls o(such a cav- em has been found ro caux a horizontal expansion of the cavern. The term "cavem" u uxd to refer to any relatively 5 solids free opening, such as a cave, void, tunnel, bore• hole, or interconnected fracrures, etc., in which the rate of gravity xgregation of Fluids is not significantly impeded by a lack of permeability. !n the presen[ process, the fluid circularion and eau 0 ern expansion operations can be initiated by opening at least a single well into an interval of oil shale that con• rains heat sensitive minerals and/or water soluble car- bonates, inflouing hot fluid into contact with an upper portion of the borehole u~all, Flowing the hot fluid down 5 along the borehole wall, and removing liquid contain- ing dissolved minerals and/or water-soluble carbonates from a lower portion of the borehole. Alternatively, a plurality of wells can be used to provide flow paths into a horizontally extensive cavem in or adjacent to oil 0 shale that contains heat sensitive minerals and/or wa- ter-soluble carbonates and the wells and the cavern can be utilized [o caux a concurzent horizontal and verti- cal expansion of a permeable zone by inflowing hot aqueous Fluid into contact with a upper portion of such 5 oil shale, (lowing fluid downward along a venical inter- val of such oil shalt, Flowing Fluid horizontally along the roof of the cavem, and removing liquid containing dis- solved minerals and/or u•a[er-soluble carbonates from within the tavern. As used herein, the term "heat sensitive and/or wa- ter-soluble carbonate" refers [o materials that decom• pose relatively rapidly at a relatively low temperature, such as one between abou[ 250° F to about 700° F, to yield carbon dioxide and water. Examples of heat xnsi- tive carbonate minerals include.naheolite da+vsonite, trona, and the like minerals which are usually inclusive of-1m'e carbonate and/or bicarbonate molecular _SLfUCNr- C- 5_ O O UeS. !n a pre(c-rr d bodiment of the prexnt invention, a borehole is drilled into a relatively low-lying portion of oil shale which contains or is adjacent to a layer or region that u relatively rich N water soluble mineral. Such water soluble minerals (generally saline minerals) arc frequently encountered in oil shale formations in the United States, such as the Green River formation in Colorado, in the form of beds, lenxs, nodules, nodes, veins or the like. Examples of such water soluble minerals include the alkali metal chloride salts such as halite mineral-s and/or water soluble heat sensitive ear- bonau minerals such az nahcolite, trona, or the like. The locations of portions of subterranean oil shales which contain specific mineral components, such az heat xnsitive carbonate minerals and/or water soluble minerals, can be determined by means o(known geo- logical investigation procedures and equipment In a preferred embodiment of the ~rro-nr in v.nr{nn ono- 2 2 3 3 a0 a5 50 DESCRIPTION OF THE DRAWING ' • FIG. 1 is a vertical section showing a subtertancan oil 55 '. shale and downhole equipment for practicing the pres- ent invention. i FIG. 3 is a schematic illustration of a flow path for circulating Fluid in accordance with the present inven• ~ lion. - FIG. 3 is a vertical section showing an alternative ar- rangement of downhole equipment of the type shown in FIG. 1. DESCRIPTION OF THE INVENTION 65 The present invention is in part premised on a diseov-