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FEB-21-1999 17-Tr3
<br />portion o! oil shale that contains heat sensitive carbon-
<br />ate mineral and is underlain by a poruon or layer that
<br />contains water soluble mineral. The water soluble mm•
<br />eral is wluhon mined or leached (or example, by means
<br />oC a process of the type desenbed in copending patent
<br />application Ser. No 770,96d; filed [Jct. 28, 1968, now
<br />abandoned, and Ser. Yo. 860,349; filed Scpt. 23, 1969,
<br />now abandoned. Those applications describe proce-
<br />dures for utilizing a wa[rr soluble miner.'d-rich portion
<br />of en oil shalt to form a tavern that can ht expanded
<br />be(ort of during else T[eovery of shale rn1 from the oil
<br />shalt r.xposcd in and aoound the cavcm Such a solu-
<br />tion mined cavern in OT adjacent to an oil Shale that
<br />contains heat scnsitivt carbonate mineral can advanta-
<br />ge0usly be utilized as a horizontally cxtcnsive tavern
<br />that is expanded vertically during the horizontal expan
<br />lion of a vertically extensive eavcrnotu zpne, such as a
<br />scctton of a borehole.
<br />Referring to the drawing, FIG. 1 show[ a portion of
<br />a well borehole 1 which has been drilled through an
<br />overburden 2, comprising sucecssively shallower earth
<br />formations, and opened into an oil abate formation 3
<br />that eontainc a heat sensitive carbonate mineral. The
<br />oil shale Cormation that is placed in nuid communicate
<br />Lion with a portion of the borehole to br used N prat
<br />[icing the present invention, chould be a formation con-
<br />taining a signrfican[proportion, e.g., greater than 5 per
<br />cent by weigh[, of heat sensitive carbonate mineral.
<br />Borehole 1 is equipped with a string oC casing d, which
<br />is bonded to the surrounding earth formations by ce-
<br />ment 5.
<br />Separate conduiu for conveying nuids between a sur-
<br />face location and, mspectivcly, rotatively shallow and
<br />relatively deep depths within the oil shalt are provided
<br />by tubing strings 7 and 8. Alternatively, such conduiu
<br />may comprise two or maze parallel swings of robing
<br />and may be located in two of more well boreholes that
<br />intersect or extend into a Common cavern within [hc
<br />orlshale. Such conduits can be installed and equipped
<br />by means oC known procedures and devices and heat
<br />insulation (not 6hown) rs prctcrably in5tallcd around at
<br />leas[ those o(such conduits that arc used foi nc~ innow-
<br />ing o! hot nuid.
<br />As indicated by F1G~ I, the vertreally extensive cav-
<br />cm or opening that is expanded by the presrnl process
<br />cap comprise the 6orthale of a well that eztt ads into
<br />an in[crral of oil shalt that contain[ heat sensitive car
<br />bonale material. Such an interval pre Cerably hu a vcrti
<br />cal thickness of at least shout 100 fact. ]n the initial
<br />stages, such a borehole may have a generally cylindri-
<br />cal form, such as inditatcd by the dotted line la, and
<br />may comprise a relatively slender, gene ally vertical
<br />cavern within the oil shale. In operating the process
<br />with the equipment shown in F1G. ], a ho[ ayucous
<br />fluid is nowcd into contact with the wall of the cavcm
<br />by innowing hot aqueous gas and/er liquid through the
<br />annulus within pipe B (i.e., the space between pipes 7
<br />and e) end through adjacent pcr(orationt 6 at a rela-
<br />tively shallow depth within the carbonate mincral-
<br />tvntaining portion of the ml shale. The innowing nuid
<br />such ae hot watCr and/Or steam nows downward along
<br />the face Of the vertical intctval of oil shale (along Ne
<br />wall vC the borehole) and dreomposee end diatalves the
<br />heat eertirtive carbonate mistral material. The rlissol v.
<br />ing of water soluble material forms a liquid solution 9.
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<br />GENERF+L CHEMIC.HI_
<br />• •
<br />3,759,328
<br />FF . 01 i0f3
<br />4
<br />is out-flowed through prpe 7, which extends to a rela-
<br />tively low Icvel within the borehole. The decomposing
<br />and dissolving of carbonate mineral components Of the
<br />vii shale causes the spalling and caving in of parUCles
<br />S ] 0 oC the oq shale and causes a generally horizontal a:-
<br />pansion of a rubblttontaining r2vernnus zone of per-
<br />meabtliri within the oil shale.
<br />Where the oil shale being treated contains a signifi-
<br />cant proportipn of a mineral, ouch as a halite, which is
<br />10 water soluble in its natural form, the infowing of hat
<br />aqueous fluid can advantageously be preceded by a cir-
<br />culatiOn of aqueous liqutd at a relatively low tempera-
<br />ture, such as the wellhead temperature, the tempera-
<br />ture of the source Of the Itquid or the like. In such a pre-
<br />15 trcatrnent, the eircWating Itquid may leach out signifi-
<br />cant portions of distfibuted layers or particles Of [he
<br />soluble mineral. This inereascs the surface arcs of ex-
<br />pos<d oil shale and(or weakens the cupport fpT layers
<br />or chunks of the oil shale. such a pret[catment cireula-
<br />2U Lion can advantageously be Continued while the rate of
<br />d'tssolunon is hrgh, e.g , as inditatcd by the proportion
<br />of solute in nc~ ourflowrng liquid. Tht 6o-eireuld[ed
<br />aqueous liqutd can then be gradually or Sapidly heated
<br />In the temperature selected far the innowing hot aquc-
<br />~5 ous liquid used to decompose heat aensitlvc carbenatc
<br />material, with or without an interruption of the Oow
<br />through the cavern.
<br />When necessary O[ desirab(c the vertical expansion
<br />of [he cavern can be inhibitr.d by spotting and main-
<br />10 taining n relati vcl ylight 8nd cool awed 13 along the roof
<br />of the cavern. Such a fluid is preferably a gas and can
<br />in inflowed, or maintained substantially stationary, in
<br />and around the annulus within casing 4 (i e., the space
<br />between pipe 8 and casing 4) and the upper portion Of
<br />35 borehole I (below cement 5) to extend along [he roof
<br />of the horzontally capanding tavern as the walls of [he
<br />cavcm more radially outward to and beyond the loca-
<br />tion shown at lb.
<br />Thc hoc aqueous fluid uxd in the present cavern.
<br />40 cnlargtng procedure is preferably steam, hot aqueous
<br />IiquiA shot water) or a mixtum of such Ouida, Thc hot
<br />^uid is prefenhly inflewcd at a tempereture, e.g., at
<br />leas[ about 250° F, that is cigni[cantly higher than the
<br />d5 norms! temperature of the subterranean oil shale for-
<br />mation. The heat transported by such a hot (laid con-
<br />vcru Thc heat scnsitivt carbonate material to carbon
<br />dipxidc and water vapor within portions of the nor-
<br />mally impermcablc oil shale matrix. Such a generation
<br />50 of gas causes localized fracturing and/Ot spalling Of the
<br />oil shale.
<br />Thc aqueous liquid component of the innowing hp[
<br />Ouid dissolves water soluble mineral material and cre-
<br />ates additional solid-free void space. T'bis occurs slang
<br />SS most, if not all, of the vertical extent of the ^ew path
<br />used in the present process. Thc spalling and dissolu-
<br />tion causes a horizontal expansion of a rubble-
<br />containing cavcm. Thc innowing hvt aqueous nuid can
<br />comprise super heated, dry, nr war Stearn, or a mixture
<br />~ of sur.h a steam with substantially any gas vapor or liq-
<br />uid, such as carbon dioaidt, phenols, hydrocarbons, al-
<br />cohols, halogenated hydrocubons, acids, or the like, or
<br />with substantially any aq~~<ous selut;on, such as an
<br />aqueous acid or bast or solution or neutral salt. Where
<br />65 the tn0pwutg Ouirt is substantially completely gaseous
<br />tt Should contain stsffjtien[ steam to provide a signdl-
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