US3525550A - Apparatus and method for producing sulfur located above a hot aquifer - Google Patents

Description

Aug- 25, 1970 E. M. KNABuscH EVAL 3,525,549

DETCHABLE CHAIR BACK Filed July 19, 1968 2 Sheets-Sheet 2 Aug. 25, 1970 c. E. HoTTMAN APPARATUS AND METHOD FOR PRODUCING SULFUR LOCATED ABOVE A HOT AQUIFER 5 Sheets-Sheet 2 Filed Feb. 5, 1969 614440 HIS ATTORNEY Aug. 25, 1970 c. E. HOTTMAN APPARATUS AND M ETHOD FOR PRODUCING SULFUR LOCATED ABOVE A HOT AQUIFER 5 Sheets-Sheet 5 Filed Feb. 5, 1969 5.53m O DIE mw hm me. E V W BYfaZ-Mb Hls ATTORNEY United States Patent O1 lice 3,525,550 Patented Aug. 25, 1970 Int. Cl. E211) 43/28 U.S. Cl. 299-6 1S Claims ABSTRACT OF THE DISCLOSURE A method for producing sulfur by locating a subterranean region having a sulfur deposit disposed above and adjacent to a salt dome with a geopressured aquifer disposed below the sulfur deposit and adjacent to the salt dome. lFluid communication is established between a surface location and both the sulfur deposit and the aquifer through at least a portion of the salt dome. A portion of the subterranean pressurized heat existing at the depth of the aquifer is transferred to the sulfur deposit through the salt dome, thereby melting sulfur in contact with the fluid from the aquifer and forcing the melted sulfur to the surface of the ground. Also disclosed is apparatus comprising a tubing extending from the surface and ha'vface location and both the sulfur deposit and the aquifer through at least a portion of the salt dome. A portion of perforated areas located between the upper and lower end and in the sulfur deposit, the areas being separated by packer means to form a system for circulating the hot fluid from the aquifer through the sulfur deposit and to the surface of the earth.

BACKGROUND OF THB INVENTION Field of the invention This invention relates to a method for producing sulfur from subterranean sulfur deposits utilizing heat necessary for melting the sulfur from a geopressured aquifer located deeper than the sulfur deposit.

Description of the prior art In recovering sulfur from underground formations, one prior art method involves underground fusion wherein a hole or well is drilled to the bottom of a subterranean sulfur deposit through the strata overlying the deposit. This hole is preferably provided with a suitable casing in which a system of lconcentric pipes is disposed. The sulfur recovery operation is customarily carried out by passing a hot lluid, such as heated water under pressure, down one of the annular spaces formed between the concentric pipes, and into the sulfur-bearing formation. Such diuid is at a temperature such that sulfur is melted and flows in consequence by gravity downwardly to the bottom of the well. The molten sulfur is forced upward through another of the annular spaces a certain distance by lthe hydrostatic pressure on the formation; then it is picked up in the well piping by a stream of compressed air, and raised to a point where it is discharged above the surface of the ground.

sIt has also been suggested to recover sulfur by in situ oxidation. However, the burning of sulfur deposits require extra compressor capacity.

When recovering sulfur by underground fusion from deposits which occur in rock strata over salt domes of the Gulf Coast type, certain difficulties are encountered due to the inherent nature of the geological formation encountered, which result in gradually increasing costs of operation as the mining progresses. The economics of producing sulfur from offshore deposits is presently suffering from the cost of establishing offshore steam-generating, air and/ or gas-compressing facilities for conveying steam to offshore locations. The supply of onshore sulfur deposits is diminishing.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method for producing sulfur from a subterranean sulfur deposit utilizing subterranean heat and pressure energy available at the site of the deposit.

fit is a further object of this invention to pro-vide a method for economically producing sulfur, thereby reducing currently excessive fcosts of externally-generated energy by an amount sutlicient to make the economics attractive.

lt is a still further object of this invention to provide a method of producing sulfur which does not require any external heating means.

The objects of this invention are attained by locating and utilizing a subterranean region in which a sulfur deposit exists above and adjacent to a salt dome and a geopressured aquifer exists below the sulfur deposit and adjacent to the salt dome. At least one well is drilled into the subterranean region and at least one well conduit is extended through a portion of the salt dome located below the sulfur deposit and opened into fluid communication with the geopressured aquifer. Fluid from the geopressured aquifer, which is relatively hot and high pressured, is flowed from the aquifer, through the intervening portion of the salt dome, and injected intothe sulfur deposit. Sulfur is recovered by connecting at least one well conduit between the sulfur deposit and a surface location and utilizing it torecover sulfur that is melted and displaced by the hot fluid thalt is injected into the deposit.

In a preferred embodiment of the invention, the geopressured aquifer that is utilized is one which contains a significant proportion of gas. The fluid produced from the gas-containing geopressured aquifer is owed up through Ithe salt dome to at least about the depth of the sulfur deposit and then is separated into substantially independent gaseous and liquid fluids. The separated gaseous fluid is injected into the well conduit through which the molten sulfur is llowed to the surface, to provide a gas-lift eifect that facilitates the sulfur recovery, and the separated liquid fluid is injected into the sulfur deposit, to provide heat for melting and sulfur. Gaseous liuid that`-was so used to facilitate the lifting of the molten sulfur is recovered as a by-product of the sulfur production pnocess.

The temperature of subterranean eanth formations increases with increases in the depth below the surface of the earth, usually at rates of about 1 per 100 feet of depth. Salt `domes are relatively good heat conductors and, since they are often vertically extensive along significant depth intervals, they tend to act as chimneys drawing heat toward Ithe surface of the earth. Geopressured reservoir formations are generally encountered at depths of at least several thousands of feet below the surface of the earth and geopressured aquifers often contain water at a itemperature near or above the 250-350 F. range that is commonly used in sulfur-mining processes, such as the Frasch process. When uicl is ilowed from a geopressure aquifer through an intervening portion of a salt dome and into a sulfur deposit, the heat and pressure of the uid are increased, or its loss of heat is reduced, by the subterranean hea-t which has been conducted to that depth interval within the salt dome. The present invention provides a method of utilizing this source off subterranean heat to improve the efliciency of processes such as those described in Pats. 3,258,069 and 3,330,356, relating to locating and utilizing the heat and pressure energy of fluids contained in geopressured aquifers.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional View of a well drilled into both a subterranean sulfur deposit and a geopressured aquifer in accordance with the teachings of this invention;

FIG. 2 is a vertical sectional View of a portion of the well of FIG. 1;

FIG. 3 is a vertical sectional view of a preferred methd for carrying out the concepts of this invention; and

FIGS. 4 and 5 are vertical sectional views of alternate methods for carrying out the concepts of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, FIG. 1 shows a subterranean sulfur deposit in the form of a sulfur-bearing caprock at the top of a salt dome 11. Reference numeral 12 indicates normal pressure duid-bearing sands or reservoirs disposed on the flank of salt dome 11; reference numeral 13 indicates aqueous Huid-bearing sands or reservoirs disposed on the flank of salt dome 11 below normal pressure sands 12. The location of such sulfur deposits, salt domes, and geopressured reservoirs may be determined by conventional geophysical means well known in the art. Preferably, such geopressured reservoir waters should have a temperature of approximately 350 F. and a fluid pressure gradient of approximately 0.70 p.s.i. per foot. The temperature and pressure of the fluids in the geopressured sands required to carry out the method of this invention are, to a large extent, governed by the depth of both the sulfur deposit 10 and the geopressured reservoirs 13. Preferably, such geopressured reservoirs are gas-containing.

After locating the geopressured reservoirs having the desired properties for carrying out the invention, as, for example, reservoirs 13, at least one energy well is drilled through the sulfur dome and into reservoirs 13, all of which are in communication. For example, as shown in FIG. l, a well 14 is drilled through the earth surface 15, through sulfur deposit 10, and into communication with geopressured reservoirs 13. Although only one such well is illustrated in FIG. 1, obviously more than one well may be drilled from earth surface 15 into communication with geopressured reservoirs 13.

Well 14 is drilled in a conventional manner Well known in the art; however, well 14 is preferably drilled through salt dome 11 in such a manner that the greatest portion of the well as possible lies within the salt of the salt dome 11. Well 14 is then cased at casing 16 and the casing 16 is cemented therein at cementing 17 as is also well known in the art.

The completed cased well 14 is next perforated at perforations 18 at one or more depths opposite the geopressured reservoirs 13. Well 14 is also perforated at one or more depth intervals, preferably in communication with the upper portion of the sulfur deposit 10 (indicated by perforations 19 in FIG. l) and at one or more depths opposite the lower portion of sul-fur deposit 10 (indicated by perforations 20 in FIG. l). All such perforations may be made by conventional means well known in the art,

such as by lowering bullet perforating devices into well 14 into the desired position. FIG. 2 illustrates a perforating means whereby a perforating device 21 is lowered by wireline 22 into a desired position in the sulfur deposit 10. Upon actuation of device 21, perforations 19 are formed in the well casing 16, cementing 17 and the surrounding formations. In like manner, one or more perforations 18 and 20 may be formed in Well 14.

In FIG. 3, a fluid flow directive system is shown which may include a tubing string 24 and packers 25, 26 and 27 disposed, respectively, above, between and below perforations 19 and 20. An aperture 28 is disposed in tubing string 24 between packers 25 and 26 and in communication with perforations 19. If desired, the portion of tubing string 24 above packer 25 may be removed, such as by backing olf the upper portion of the tubing string as is well known in the art. Preferably, however, tubing string 24 may be valve controlled by means of normally-closed valve means 29. A relatively short section of tubing string, such as tubing string 31, is disposed in well 14 and extends through packers 25 and 26, thereby communicating, at its lowermost end, with perforations 20, and at its topmost end with the annulus formed between tubing string 24 and casing 16 and above packer 25. Although other iluid ow control or Huid ow directing systems may be used in the arrangement disclosed hereinabove, iluid circulates from geopressured reservoirs 13, through perforations 18, up tubing string 24, out aperture 28 and into sulfur formation 10 through perforations 19. As indicated by the arrows in FIG. 3, the fluid then circulates down through the sulfur formation 10 and back into the well 14 through perforations 20 and up tubing string 31. In this manner, a signicant portion of sulfur deposit 10 is contacted by the circulating Huid. Gas may be supplied below the lower end of tubing string 31 by injecting gas Ifrom an external gas supply (not shown) down tubing string 31a so as to gas-lift the fluid circulating out of sulfur deposit 10` to the surface.

Alternatively, as illustrated in FIG. 4, a packer 30 may be installed in well 14 between perforations 19 and 20. As indicated by the direction of the arrows, fluid flows from geopressured reservoirs 13, through perforations 19, up well 14, through normally open valve 30b in packer 30a, out perforations 20 and into sulfur deposit 10. The ui'd then circulates through the sul-fur deposit 10, back into well 14 through perforations 19 and out of the well 15.

In either case, because of the greater fluid pressures in geopressured reservoirs 13, hot high-pressure uid flows from reservoirs 13 through perforations 18, up well 14, through the respective perforations as indicated and into the sulfur-bearing rock deposit 10.

This injection of hot water into the sulfur-bearing deposit 10 causes a rise in temperature of deposit 10. Once the temperature of the deposit 10 is raised above the melting point of sulfur, the solid sulfur present in deposit 10 melts and becomes mobile or liquid. The density of the resultant mixture of fluid and molten sulfur is decreased by reducing the pressure on the lluid from the aquifer, and gas released therefrom or from another source is mixed with the mixture. This may be accomplished, in the case of the embodiment of FIG. 3, by providing conventional pressure control valve means 24ain tubing string 24 before aperture 28. In the case of the embodiment of FIG. 4, packer 30a and conventional pressure control valve means 30b must be installed below perforations 20.

As can be seen in both FIGS. 3 and 4, in the step of transferring heat energy from the geopressured reservoirs 13 to the sulfur deposit 10, the amount of heat that is transferred to the sulfur deposit is supplemented by owing the uid released from reservoirs 13 into a heat exchange relationship with the interior of salt dome 11. This heats or thermally insulates the released uid by transferring to it or surrounding it by the subterranean heat that is conveyed preferentially through the salt in the salt dome from a subterranean depth that may be greater than that of the geopressured reservoirs 13.

A preferred arrangement for producing sulfur from a subterranean deposit in accordance with the teachings of this invention is illustrated in FIG. 5. A sulfur-bearing zone is indicated in sulfur deposit 10. An energy well 31 is shown extending into the sulfur-bearing zone. The well 31 continues down through the sulfur-bearing zone, through salt dome 11 and into the geopressured formation or formations (not shown in FIG. in the manner discussed hereinabove with respect to FIGS. 1 through 4.

Well 31 is preferably surrounded by at least a pair of spaced producing wells 32 and 33. Wells 32 and 33 preferably terminate at the bottom of the sulfur-bearing zone. All the wells 31 through 33 are preferably cased (as at casings 34 through 36, respectively) with the casings cemented therein (as at cementings 37 through 39, respectively). Thus, wells 32 and 33 are preferably cemented below the base of the sulfur-bearing zone.

Wells 32 and 33 include perforations 40 and 41, respectively, preferably at their lower ends in communication with the bottom portion of the sulfur-bearing zone. Wells 32 and 33 also include tubing strings 42 and 43, respectively, extending through the appropriate well and into position adjacent their respective perforations.

Referring now to energy well 31, casing 34 is preferably a large-diameter casing perforated both at perforations 44 in the upper part of the sulfur-bearing zone and at perforations 45 in the lower part of the sulfur-bearing zone. Perforations 44 and 45 are packed olf from one another by installing packers 46, 47 and 48 above perforations 44, between perforations 44 and 45 and below perforations 45, respectively. A gas tubing string 49 is installed in well 31 below packer 48 as illustrated in FIG. 5. A slotted liner 50 having downhole valve means 51 at its lower end is set in well 31 through packers 46, 47 and 48 in such a manner that its apertures, as for example slots 52, are disposed in the portion of well 31 between packers 46 and 47 opposite perforations 44 and valve means 51 is disposed below packer 48. The upper end of liner 50, extending out of Well 31, is preferably controlled by valve means 53.

A second slotted liner 54 having downhole valve means 55 at its lower end is also set in well 31 through packers 46, 47 and 48 in such a manner that its apertures, as for example slots 56, are disposed in the portion of the well 31 between packers 47 and 4S opposite perforations 45 and valve means 55 is disposed below packer 48.

A suitable control valve means 57 is disposed at the upper end of tubing string 42 of producing well 32. Tubing string 42 passes into a conventional separator 58 and through a branch portion 59 controlled by conventional valve means 60 where undesirable gases may be flared oif at 61. Branch portion 59 passes through second control valve means 62 and meets a tubing string 63 disposed in liner 54 in energy well 31. Tubing string 63 extends down through and is concentric with liner 54. Tubing string 63 is imperforate and open at its bottom, which terminates below packer 48 and above valve means 55.

At its junction with tubing string 63, branch portion 59 also passes through control valve means 64 and either forms, or comes into Contact with, tubing string 43 of producing well 33. An external gas supply line 65, controlled by valve means 66, is preferably disposed between valve means 64 and tubing string 43.

Tubing string 49 of energy well 31 also passes into separator 58 and is controlled by valve means 66. Liquid sulfur may be withdrawn from liner 54 through a suitable sulfur outlet 67, controlled by valve means 68. Sulfur and gas may be withdrawn from producing wells 32 and 33 through gas and sulfur outlets 69 and 70, respectively, controlled by valve means 71 and 72, respectively. From outlets 67, 69 and 70, the withdrawn mixtures are passed into suitable separators 73 through 75 respectively,

where the mixtures are separated into sulfur, fluid and gas.

In operation, the following method for producing sulfur from sulfur-bearing zone may be employed.

Valve means 51 of liner 50 is opened and valve means 53 is closed. Hot fluid flows from the geopressured reservoirs 13 (FIGS. l, 3 and 4), in the manner discussed hereinabove, up well 31 through salt dome 11 and into the portion of casing 34 below packer 48. Fluid flows into liner 50 through valve means 51 and out through the slots 52 into the annular space between packers 46 and 47. The hot uid then flows through perforations 44 into the sulfur-bearing zone. The fluids continue to flow from geopressured reservoirs 13 (FIG. 3) into the sulfur-bearing zone continually heating the solid sulfur until it melts and becomes a liquid. Since the density of liquid sulfur is approximately twice that of Water, the liquid sulfur ows to the base of the sulfur-bearing zone. As more and more liquid sulfur accumulates at this base, liquid sulfur enters perforations 45 of the energy well 31 and the perforations 40 and 41, of production wells 32 and 33, respectively.

At this point, gas, essentially methane, is injected down tubing strings 42 and 43 of the production Wells 32 and 33 through external gas supply line 65 and the liquid sulfur is gas-lifted up the annulus space between casings 35 and 36 of production wells 32 and 33 and out of outlets 70 and 69, respectively. Although two such production wells are illustrated in FIG. 5, obviously one or more production wells may be used such as several similar production Wells simultaneously producing liquid sulfur.

Gas-lifting operations may also be carried out in energy well 31 simultaneously with fluid displacement from the energy well 3-1 into the sulfur-bearing zone. The liquid sulfur entering casing 34 through perforations 45 passes through slots 56 and into liner 54. Gas may then be injected down tubing string 63 into liner 54 and liquid sulfur is gas-lifted up the annular space of liner 54 and out of outlet 6.7. iIn the foregoing steps, it is assumed that the suitable valve means are opened or closed, as desired. A valve 63a may be disposed at the top of tubing string 63 so that string 63 may be by-passed when injecting gas into well 32. Also, a control valve 58a may be disposed at the top of separator 58 so as to bypass the separator 58, if desired.

Alternatively to the method discussed hereinabove, valve means 55 of liner 54 may be opened and hot Iwater injected into the lower portion of the sulfur-bearing zone when it contains liquid sulfur. Thus, hot water from the geopressured reservoirs 13 passes through valve means 55, out slots 56 and through perforations 45 into the lower portion of the sulfur-bearing zone. This hot injected fluid displaces the liquid sulfur through perforations 40 and 41 into production wells 32 and 33, respectively. In this manner, gas lift may not be necessary -with the sulfur and gas created by the mixture of the hot fluid and liquid sulfur produced out of wells 32 and 33 through outlets 70 and 69, respectively. In this feature of the invention, it may be necessary to close valve means 51 and 53 of liner 50. This feature of the invention may be alternated with the foregoing steps to produce sulfur.

As a preferred feature of this invention, the hot, highlypressurized uids contained in many geopressured aquifers are saturated with or contain dissolved hydrocarbon compounds such as methane. Upon producing such fluids, the pressure and temperature is reduced and these dissolved hydrocarbons come out of solution, and the fluids separate into a mixture of a gaseous uid and a liquid lluid.

The gaseous iluid may be utilized in the gas lift portion of the present invention. Accordingly, much of the dissolved gas is separated in the annular space of casing 34 below packer 48 and above the bottom of liners 50y and 54. This separated gas (containing water) is produced up tubing string 49 and into separator 58. The pressure of separator 58 is preferably maintained at a suiiicient pressure such that no additional energy is required to inject the gas into the tubing strings 42 and 43 of producing wells 32 and 33, respectively and/or the tubing string 63 of energy well 31 as disclosed in the foregoing steps.

I claim as my invention:

1. In a method of producing sulfur comprising:

locating a subterranean region having a sulfur deposit disposed above and adjacent to a salt dome with with a geopressured aquifer disposed below the sulfur deposit and adjacent to the salt dome; establishing fluid communication between a surface location and both said sulfur deposit and said aquifer through at least a portion of said salt dome;

transferring a portion of the subterranean pressurized heat existing at the depth of the aquifer to the sulfur deposit by iiowing the pressurized fluid in the aquifer from the aquifer through said portion of said salt dome into the sulfur deposit thereby melting sulfur in contact with the uid from the aquifer; and

flowing the mixture of fluid and molten sulfur from the sulfur deposit to said surface location.

2. The method of claim 1 including the step of recovering sulfur from the mixture of iiuid and molten sulfur tiowing to said surface location.

3. The method of claim 1 including the step of locating said subterranean region adjacent to a gas-containing geopressured aquifer and separating the fluid produced from said aquifer into substantially independent gaseous and liquid iiuids; and

flowing said separated gaseous fluids to said surface location, thereby providing a gas-lift to said molten sulfur while injecting the separated liquid fluid into said sulfur deposit thereby providing heat for melting said sulfur.

4. The method of claim 3 including the step of recovering said gaseous fluid as a by-product.

5. Apparatus for producing sulfur from a subterranean sulfur deposit located at the top of a salt dome and a gas-containing geopressured aquifer that is located deeper than the sulfur deposit but higher than the bottom of the salt dome, said apparatus comprising:

at least one `well extending from a surface location through both said sulfur deposit and said salt dome and into said aquifer;

a well casing permanently iixed in said well;

rirst perforations extending through said well casing and into said aquifer;

second perforations extending through said well casing and into the upper portion of said sulfur deposit; third perforations extending through said well casing and into the lower portion of said sulfur deposit; and packer means disposed in said well below the second perforations and above the third perforations for sealing said second perforations from said third perforations.

6. The apparatus of claim 5 wherein the greater portion of said well extends through said salt dome.

7. The apparatus of claim 5 including packer means having a pressure control valve therein disposed below said third perforations and above said first perforations.

8. The apparatus of claim 5 including second and third packer means disposed both above said second perforations and below said third perforations, respectively, for sealing said perforations;

a iirst tubing string disposed in said well and extending through all of said packer means;

aperture means disposed in said tubing string between said iirst and second packer means thereby communicating said aperture means with said second perforations; and

a second tubing string extending through said iirst and second packer means having its lower end in communication with said third perforations.

9. The apparatus of claim 8 including valve control means disposed in said iirst tubing string below said aperture means for controlling flow through said tubing string.

10. The apparatus of claim 5 including at least one cased producing well spaced from said first mentioned well, said producing well extending toV at least the bottom of said sulfur deposit and having perforations communicating said producing well with said sulfur deposit;

packer means disposed in said first-mentioned well both above and below said second and third perforations, respectively, for sealing said perforations;

a first tubing string disposed in said first-mentioned well and extending through all of said packer means in said lirst-mentioned well so that the lower end of said first tubing string is disposed below said third packer means;

aperture means disposed in said first tubing string between said first and second packer means thereby communicating said aperture means with said second perforations;

valve means disposed at both the upper and lower ends of said rst tubing string for selectively opening and closing the upper and lower ends of said first tubing string;

a second tubing string disposed in said first-mentioned well and extending through all of said packer means in said first-mentioned well so that the lower end of said second tubing string is disposed below said third packer means;

aperture means disposed in said second tubing string between said first and third packer means thereby communicating said aperture means in said second tubing string rwith said third perforations; and

normally closed valve control means disposed at the lower end of said second tubing string for controlling tluid iiow therethrough.

11. The apparatus of claim 10 including:

a tubing string disposed in said producing well opening below said perforations in said producing well; and

external gas supply means coupled to said last-mentioned tubing string for supplying gas thereto.

12. The apparatus of claim 11 wherein at least two cased, producing wells are spaced from said `first-mentioned well;

each of said producing wells having perforations substantially adjacent to the bottom of said sulfur deposit, tubing strings disposed therein extending below said perforations in said producing wells and external gas supply means coupled to each of said producing well tubing strings for supplying gas thereto.

13. The apparatus of claim 11 including gas outlet means disposed in said iirst-mentioned well, said gas outlet means extending through all of said packer means and opening below said third packer means;

said gas outlet means being adapted to remove gases dissolved in said aquifer;

gas separator means coupled to said gas outlet means for separating gas from said gases dissolved in said aquifer; and

coupling means for coupling said gas separator to said external gas supply means for providing the gas supplied to said tubing string disposed in said producing well.

14. The apparatus of claim 1() including a third tubing string disposed in said iirst-mentioned well and extending through said second tubing string below said aperture means therein so that the lower end of said third tubing string is in communication lwith the aperture means in said second tubing string; and

external gas supply means coupled to said third tubing string for supplying gas thereto.

9 10 15. The apparatus of claim 14 including gas outlet to said external gas supply means for providing the means disposed in said first-mentioned Well, said gas outgas supplied to both tubing string disposed in said let means extending through all of said packer means and producing Well and said third tubing string disposed opening below said third packer means; in said first-mentioned well.

said gas outlet means being adapted to remove gases 5 dissolved in said aquifer; References Cited gas separator means coupled to said gas outlet means UNITED STATES PATENTS for separating gas from said gases dissolved in said 3,432,205 3/1969 Hottman etal 299 6 aquifer; and coupling means for coupling said gas separator means 10 ERNEST R. PURSER, Primary Examiner

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