US2682396A - Method for mining soluble ores - Google Patents

Description

June 29, 1954 R wo l- 2,682,396

METHOD FOR MINING SOLUBLE ORES Filed Sept. 17, 1948 4 Sheets-Sheet l ATTORNEY June 29, 1954 R. G. HAWORTH 8 METHOD FOR MINING SOLUBLE ORES v Filed Sept. 17, 1948 4 Sheets-Sheet 2 JNVENTOR. Rus s|l G. Hclwonh ATTORNEY June 29, 1954 R. cs. HAWORTH METHOD FOR MINING SOLUBLE ORES Filed Sept. 17, 1948 4 Sheets-Sheet 3 Q INVENTOR. RussellG. Haworrh BY v WA f: W

' ATTORN EY June 29, 1954 R. G. HAWQRTH 2,682,395

METHOD FOR MINING SOLUBLE ORES Filed Sept. 17, 1948 4 Sheets-Sheet 4 x xx X! x,

i INVENTOR. W RusseHG. Huworfh kg! y ATTORNEY Patented June 29, 1954 METHOD FOR MINING SOLUBLE ORES Russell G. Haworth, Carlsbad, N. Mex., assignor to Potash Company of America, Denver, 0010., a corporation of Colorado Application September 17, 1948, Serial No. 49,833

12 Claims.

This invention relates, generally, to the art of solution mining of soluble minerals, and it has particular relation to a novel and economical method of solution mining for relatively thin deposits of soluble ores, such as ones including soluble potassium salts.

Solution mining i broadly old. However, insofar as I am aware, solution mining has previously involved operating through holes drilled downwardly from the ground surface into underground deposits of soluble minerals, such as salt. Although such mining methods are practical for working mineral deposits of substantial thickness, they are not practical for working thin deposits (1. e. a few feet thick) located at substantial depths, since, in these latter instances, the amount of mineral that can practically be obtained at the foot of each well or shaft is so small that the cost of driving the wells i prohibitive. Likewise, ordinary mechanical mining methods are not suited to or economical for working such thin layer deposits.

According to the present invention, an economical method for working sub-surface deposits of soluble mineral salts has been provided, which involves a unique combination of mechanical mining methods with a novel technique of solution mining. Thus, I provide as by mechanical mining methods, a main entry down and into such a shallow deposit of soluble mineral, and then 7 provide a number of cross or lateral entries leading off therefrom at suitable intervals. It is from these cross entries or laterals that I employ my novel solution mining technique to leach out the deposit in between adjacent cross entries. As Will appear more fully hereinafter, the areas of the deposit are leached out in such a way that backfill may be introduced into already extracted portions as the leaching progresses in intermediate portions.

An important object of the invention is the provision of an economical method of working subsurface deposits of soluble mineral deposits by solution mining from underground entries without drilling a plurality of vertical wells from the surface.

Another important object of the invention is the provision of an economical method of working sub-surface deposits of soluble mineral deposits by a combination of mechanical and solution mining methods, as well as by solution mining only, and obtaining thereby a reduction in maintenance and operating cost.

Still another object of the invention is the provision of a method of operation from a lateral entry in such a way as to extract or leach out an elongated room in a deposit or bed of soluble mineral, starting with a group of small holes drilled adjacent the top of said deposit and extending for the depth of the room.

Still another object of the invention is the provision of a method of working a deposit of soluble mineral from lateral entries therein, which involves leaching out or extracting a plurality of elongated rooms in the deposit on opposite sides of each lateral entry, leaving intermediate pillars of ore between adjacent rooms, after which the rooms may be hydraulically backfilled with sand for support, after which the intermediate pillars of ore may be leached out.

Certain other objects of the invention will in part be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention, reference may now be had to the following detailed description of an illustrative embodiment thereof, taken in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic plan view illustrating the manner in which a shallow deposit of soluble mineral ore is worked or mined in accordance with the present invention;

Fig. 2 is a diagrammatic sectional view taken on line 22 of Fig. 1;

Fig. 3 is a diagrammatic sectional view taken on line 33 of Fig. 1

Figs. 4, 5, 6 and '7 are diagrammatic sectional views taken on line AA of Fig. 1. showing respectively dilferent stages of the solution mining operation; and

Figs. 8 and 9 are diagrammatic cross sections illustrating a modified form of my invention.

Referring now to Fig. l of the drawings, the reference numeral Ill designates a main entry into a bed of soluble ore l l (i. e. potash deposits). On centers of 600-650 feet cross entries or lateral entries l2l2 are cut in the deposit H at right angles to the main entry Ill. It will be understood that the dimension of 600-650 feet, although a practical one, is given by way of illustration, and that the invention is not limited either with respect to this dimension or the other specific diproximately thirty feet. Track may be laid in the main entry it and the cross entries l2l2 so as to provide ready access thereto and a means of transporting equipment and men. The entries may each be about eight feet in height and twelve feet in width.

Although the deposit l I may be nearly horizontal, in most instances it will have at least a small pitch or dip in one direction or another. For purposes of more fully illustrating the invention, it will be assumed that the deposit i i has an upward pitch from left to right in Figure 1. As will appear presently in detail below, I employ solution mining technique in such a way as to leach out or extract from the deposit H a plurality of regularly spaced elongated rooms I l-M which slant upwardly from the lower or left-hand cross entry l2 in Figure 1 and a second set of similar rooms I|5 which slant downwardly from the upper or right-hand cross entry 52 in Figure 1. It will also be seen below that, after formation, the rooms l4l4 and l5l5 are hydraulically filled with sand so as to re-establish bearing support areas therein, and then the intermediate pillars of mineral I i-46 and l'l-ll, respectively, Figure l, are leached out or extracted.

Reference may now be had to Figures 2 and 4-7 for a detailed description of the method of formingthe elongated rooms |5|5. Each of the rooms is started by using diamond drills to drill a group of five holes l8l8 (Figure 4.) on six foot centers in, or just above, the ore deposit ll to a distance of approximately 300 feet. The first hole i 8 of each group should be cored to demine proper vertical elevation. After the holes |llls are drilled, the collar of each hole is reamed to a depth of approximately feet and a four inch casing 2e (Figure 2) is placed in the reamed section and cemented in place with concrete 2! to prevent leaching in this zone which will remain as a pillar 22, and also serving as a dam to retain brines or solution in the rooms l5l5.

When the casings 2B are in place, a two inch inner pipe 23, approximately 300 feet long, is inserted through each casing into the corresponding hole l8. Each casing 29 is provided near its outer end with an inlet port 24 and the end of the casing being sealed to the pipe 23, as

at 25. With this arrangement installed, fresh water is introduced through each of the ports 24-24 and allowed to trickle along the bottoms of the holes l8l8 to the lower ends thereof, dissolving the soluble ore.

The resulting brine collecting in the bottom or far end of each hole I 8 is pumped out through the respective pipes 23 which are connected to suitable pumping means. This circulation is continued until a slot 26 (Figure 5) is out under each hole l8 which extends approximately through the thickness of the deposit I l.

The completion of the slots 2626 can be ascertained by a change in the composition of the brine withdrawn from the pipe 23. Thus, if the deposit ll consists of sylvite in a known concentration sandwiched between layers of halite 31, a decrease in the K01 content of the brine and a corresponding increase in the NaCl content, will indicate that the slots 2626 have gone through the deposit Ii.

After the slots 2E26 have thus been cut, which may take approximately forty-eight hours, they are filled with water and the flow or direction of circulation is reversed. That is, fresh water is v 4 introduced through the pipes 23-43 to the bottom of the respective slots 2626, which will fill up with solution and remain filled during leaching. The solution of brine is withdrawn from the upper end of each slot 26 through the casings 2820 and the ports 2424. The rate of flow is regulated so as to produce a brine saturated with respect to KCl. Dissolution or leaching of the ore takes place largely on the opposite sides of each slot and these become increasingly larger as indicated at 2l-2T in Figure 6. Eventually, each group of enlarged holes BI -21 merge to form a room l5 as shown in Figure 7. At this stage, the only ore remaining in the room 15 will probably be in the floor thereof and that forming the barrier or pillar 22 at the side of the cross entry l2.

If desired, this ore remaining in the bottom of each room [5 may be largely leached out. To do this, each room is emptied of its contents by pumping it almost dry through the pipe 23 which bends downwardly under its own weight as the cut deepens from its former position in drill hole l8 shown in dotted lines in Figure 2. Fresh water is then introduced through each of the casings 20-20 and allowed to trickle down the floor, cutting irregular channels therein so as to expose remaining ore which may be covered with clay. This water is removed through pipe 23 until the irregular channels reach the halite bed 31, when the flow is again reversed so as to refill the room l5 through the pipe 23 and withdraw saturated brine through the casing 20.

A drop in the K01 concentration in each phase of the leaching operation in the formation of room i5 is usually an indication that the particular phase of my process then in operation should be terminated.

It will be seen that each room IE will be upwards of 36 feet wide when the end holes of the group of drill holes [8-4 8 are 30 feet apart. The holes l8-l8 are spaced apart a distance which is determined to a large extent by the thickness of the deposit H. Generally speaking, the drill holes should be so spaced in each instance that by the time the corresponding slots cut through the ore are enlarged to the point of merging together as shown in Figure '7, the deposit H will have been leached through to the bottom.

In the event the overlying bed or root is of salt or other soluble material, proper spacing of the drill holes will also reduce the amount of soluble waste material extracted with the ore, and this factor should be taken into consideration when the spacing of the holes is determined.

In order that the pillars of ore I'I between adjacent rooms [5 may be leached out without causing the upper surface of the mine to cave in, the rooms 15 are first hydraulically filled with sand, thereby restoring bearing support areas therein. After this operation, the pillars Il may be leached out as rooms following the technique above described for the extraction of rooms IS.

The rooms M-M are formed in the same general manner as rooms l5-l5, but the technique is somewhat modified in view of the fact that these rooms 'rise or slant upwardly from the lefthand entry I2, Figure 1. For a description of the method of forming rooms H-M, reference may now be had to Figure 3.

For each room M, a group of say five drill holes are drilled corresponding to those drilled for each room I5. The collar of each drill hole is reamed and a four inch casing 30 is cemented in place so as to leave a barrier or dam of ore 3! thereunder. A 300-foot length of pipe 32 is then inserted in each drill hole and slots corresponding to slots 2626, Figure 5, are cut by circulating fresh water through the pipes 32 to the upper end of each drill hole and allowing it totrickle back along the bottom thereof to a hose 33 inserted through the casing 30 resting on the bottom of the slot.

During this operation the brine or water, which may be either hot or cold, should be held at the lowest practical limit by pumping or siphoning through the hose 33. This tends to prevent saturation of the liquid by the walls of the slot, and concentrates the dissolving action on the bottom of the slot, thus increasing the rate of slot formation. I

When the slot has been formed to the desired depth, I prefer to remove the hose 33 and to connect the pipes 30 and 32 in a manner similar to pipes 20 and 23 (Figure 2). Fresh water or unsaturated brine may then be introduced through pipe 30 and circulated through the slot in contact with the walls at a rate which will substantially saturate the liquid with ore. The slot is therefore filled with liquid under some pressure, and is exhausted through pipe 32 at the desired rate. Obviously the walls expose the greatest area to the action of the liquid, and furnish the greatest majority of the soluble material required to saturate the liquid.

When the concentration of the brine begins to drop, it may be desirable to empty the slot or hole and reverse the flow of fresh water so as to allow it to trickle down the bottom of the hole to the hose 33, which may be reinserted for the purpose, so as to expose more ore, or in some instances the water may be exhausted through the pipe 30. Thereafter, the hole may again be filled and additional ore leached out until each room [4 is completed. Then each room I4 may be hydraulically filled with sand and the intermediate pillars !6 leached out.

The saturated brine withdrawn during the leaching operations may be pumped to a surface refining plant designed to extract the valuable salts, e. g. KCl, therefrom in known manner.

In places where the deposit H is horizontal, the ore may be leached out either according to the method described above for forming rooms -!5, or by that for forming rooms I4|4. If desired, a combination of both methods can be used.

In certain instances, the main entry Ill and the cross entries l2l2 may be more economically formed by following the techniques described above for the formation of rooms |5l5. The resulting elongated entries would require only a minimum amount of trimming by usual mechanical mining methods to make them suitable for haulage entries.

The invention hereinfore described course, particularly advantageous in mining thin beds of water soluble ore, which usually consist principally of the various salts or salt'combinations of the alkali metals. From a cost standpoint, the comparison in cost between my method of mining and the conventional mechanical methods of mining will be most marked when employed in the mining of beds having a height or depth of less than approximately six feet, but is oftentimes cheaper than mining methods even I in beds twelve feet or more in depth.

In most instances it will be found preferable to employ the system hereinbefore described which incorporates the forming of a slot by proper manipulation of the liquid prior to theis, of

6 major solution mining operation. For example, beds of sylvinite are often found between beds of salt and it is obviously desirable to minimize the solution of the salt to the greatest possible extent. Forming a vertical slot through a bed, say four feet thick and three hundred feet long will expose twelve-hundred square feet of ore on each side of the out, while the top of say a two inch slot will expose only fifty square feet of the salts in the overlying bed. The bottom of the slot is usually filled with slimes and does not present a serious problem. Because of the large area exposed, solution proceeds at a relatively rapid. rate, particularly when compared to a vertical hole of say six inch diameter, which would expose an areaof only approximately six square feet in a four foot bed.

It is not in each instance necessary that the drill holes be disposed at or near the level of the overhang bed, since in some instances it will be advantageous to form these openings along the line midway between the upper and lower beds, thus as shown in Figures 8 and 9, I may form a plurality of spaced drill holes t2 in a bed 43 of soluble ore disposed in upper and lower beds 44 and 46 respectively. Hot or cold water or unsaturated brine may be pumped through these holes, preferably under pressure, until the walls have dissolved to the extent necessary to form enlarged interconnected cavities 41 indicated at an intermediate stage in Figure 9. This system might be utilized, for example, where the upper and lower beds were of a substantially water-soluble material.

It should also be understood that in many instances cross entries, drifts, and the like may be formed by properly utilizing my mining method at a lower cost than the same operation could be formed by mechanical mining methods, this being true, of course, only in instances where the operations are to be formed in water-soluble deposits such as halite.

Since certain further changes or modifications may be made in the foregoing methods and different embodiments of the invention may be practiced without departing from the spirit and scope thereof, all matter described above in connection with the accompanying drawings, is intended as illustrative and not in a limiting sense.

I claim:

l. The method of mining an inclined watersoluble mineral deposit from two parallel, widely spaced, lateral entries therein, which comprises, drilling from the upper entry a plurality of spaced groups of parallel small diameter drill holes downwardly from said upper entry to approximately one-half the distance between said entries, and on a plane adjacent to the top of said deposit, inserting a pipe into each drill hole to approximately the remote end thereof, introducing fresh water into said hole on the outside of said pipe and withdrawing the resulting brine from the bottom of said hole through said pipe and continuing such circulation until a slot is cut underneath each drill hole to a level near the bottom of said deposit, filling each slot with water, introducing unsaturated water through said pipes into the bottom of each slot and withdrawing saturated brine from the upper end thereof after it has circulated along the bottom of the slot thereby dissolving away the sides and bottom of each slot sufiiciently to leach away the ore separating adjacent slots so as to form for each group of drill holes an elongated room in said deposit approximately equal in width to the width of said group of drill holes, drilling a plurality of spaced groups of parallel small diameter drill holes upwardly from the lower entry to approximately half the distance between said entries and on a plane adjacent to the top of said deposit, inserting a pipe into each of said upward drill holes approximately to the remote end thereof, introducing fresh water into the upper end of each upward drill hole through said pipe therein and allowing it to run back down the bottom of said hole and continuing such circulation until a slot is cut underneath each drill hole nearly through to the bottom of said deposit, filling each said slot with water, introducing unsaturated Water into the lower end of each said slot and withdrawing saturated brine from the upper end thereof through the pipe therein after it has circulated along the bottom of each said slot thereby dissolving away the sides and bottom thereoi suificiently to leach away the ore separating adjacent slots so as to form for each group of said drill holes from said lower entry an upwardly sloping elongated room in said deposit approximately equal in width to the width of the corresponding group of drill holes drilled from said lower entry, said drill holes drilled from said upper and lower entries being so spaced apart relative to the thickness of said deposit that by the time said adjacent elongated slots have become interconnected into an elongated room said deposit will be approximately leached through to the bottom thereof.

2. The method called for in claim 1 wherein said elongated rooms are hydraulically filled in with sand to restore bearing support areas therein, and the ore remaining between said adjacent rooms is then leached out.

3. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a lateral entry extending past a portion of said mineral deposit for a substantial distance, drilling a plurality of holes near the top of said deposit extending from said entry in a substantiall parallel arrangement following the contour of said deposit and penetrating same for a substantial distance, introducing water into said drill holes throughout their lengthwise extent through an inlet conduit directed lengthwise of said drill holes toward the remote end thereof so as to progressively produce vertical slots by dissolution extending substantially throughout the depth of said deposit, withdrawing solution formed by dissolution of soluble material in said slot-forming operation at a point near, but spaced from, the entry end of said drill holes, and then introducing additional water into the slotted area at a high point therein, and simultaneously withdrawing the resulting solution from a low point therein so as to leach out the soluble material between said slots and thereby form a single room in said deposit within the drilled area.

4. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a lateral entry extending past a portion of said mineral deposit for a substantial distance, drilling a plurality of holes near the top of said deposit extending from said entry in a substantially parallel arrangement following the contour of said deposit and penetrating same for a substantial distance at an elevation above the bottom of the deposit, introducing water into said drill holes throughout their lengthwise extent through an inlet conduit directed lengthwise of said drill holes toward the remote end thereof so as to progressively produce vertical slots by dissolution extending substantially throughout the depth of said deposit, withdrawing solution formed by dissolution of soluble material in said slot-forming operation at a point near, but spaced from, the entry end of said drill holes, and then introducing additional Water into the slotted area at a high point therein, and simultaneously withdrawing the resulting solution from a low point therein promptly after its formation so as to leach out the soluble material between said slots and thereby form' a single room in said deposit within the drilled area.

5. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a lateral entry extending past a portion of said mineral deposit for a substantial distance, drilling a plurality of horizontally ranging holes near the top of said deposit extending from said entry in a substantially parallel arrangement following the contour of said deposit and penetrating same for a substantial distance, introducing water into said drill holes throughout their lengthwiv e extent through an inlet conduit directed lengthwise of said drill hole toward the remote end thereof so as to progressively produce vertical slots by dissolution extending substantially throughout the depth of said deposit, then filling said slots with water introduced through a conduit having its outlet near a high point in each slot so as to leach out the remaining portions of said drilled deposit, and simultaneously withdrawing the resulting solution through another conduit having its intake at a low point therein, promptly after formation of said solu tion so as to prevent dissolution of material from the underlying soluble layer.

6. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a lateral entry extending past a portion of said mineral deposit for a substantial distance, drilling a plurality of horizontally ranging holes near the top of said deposit extending from said entry in a substantially parallel arrangement following the contour of said deposit and penetrating same for a substantial distance, sealing the deposits around said holes from said entry for a short distance interiorly thereof to prevent dissolution thereof, introducing water into said drill holes throughout their lengthwise extent through an inlet conduit directed lengthwise of said drill hole toward the remote end thereof so as to produce vertical slots by dissolution extending substantially throughout the depth of said deposit, then filling said slots with water introduced through a conduit having its outlet near a high point in each slot so as to leach out the remaining portions of said drilled deposit, and simultaneously withdrawing the resulting solution through another conduit having its intake at a low point therein, promptly after forrna tion of said solution so as to prevent dissolution of material from the underlying soluble layer.

'7. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a lateral entry extending past a portion of said mineral deposit for a substantial distance, drilling a plurality of horizontally ranging holes near the top of said deposit extending from said entry in a substantially parallel arrangement following the contour of said deposit and penetrating same for a substantial distance, introducing water into said drill holes throughout their lengthwise extent through an inlet conduit directed lengthwise of said drill hole toward the remote end thereof so as to produce vertical slots by dissolution extending substantially throughout the depth of said deposit, then filling said slots with water introduced through a conduit having its outlet near a high point in each slot so as to leach out the remaining portions of said drilled deposit, said drill holes being so spaced apart relative to the thickness of said deposit that by the time said adjacent slots have becomeinterconnected. to form a single room the drilled portion of said deposit will be substantially leached through to the bottom thereof, and simultaneously withdrawing the resulting solution through another conduit having its intake at a low point therein, promptly after formation of said solution so as to prevent dissolution of material from the underlying soluble layer.

8. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition which dip from the horizontal, which comprises forming a lateral entry extending past a high portion of said mineral deposit for a substantial distance, drilling a plurality of holes extending downwardly from said entry to a substantial distance into said deposit on a plane adjacent the top thereof, discharging water into said holes through a conduit having its outlet adjacent the upper end thereof, withdrawing resulting solution through another conduit having its intake at a low point in the deposit adjacent the lower end of each hole, and continuing the introduction of water at said upper end until substantially all the soluble content within the drilled area has been dissolved.

9. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition which rise from the horizontal, which comprises forming a lateral entry extending past a low portion of said mineral deposit for a substantial distance, drilling a plurality of holes extending upwardly from said entry to a substantial distance into said deposit on a plane adjacent the top thereof, discharging water into said holes through a conduit having its outlet adjacent the upper end thereof, withdrawing resulting solution through another conduit having its intake at a low point in the deposit adjacent the lower end of each hole, and continuing the introduction of water at said upper end until substantially all the soluble content within the drilled area has been dissolved.

10. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of dif- 6 ferent composition, which comprises forming a small opening into such a soluble deposit from a breast near the upper boundary of the bed and approximately parallel thereto, circulating water through a conduit extending through the opening and having its outlet at the end thereof remote from the breast, removing resulting solution from another conduit having its intake at a point near the breast in an action in which a vertically ranging slot is formed in the deposit, and then reversing the circulation of water into the opening through said conduits so as to leach out soluble material of the deposit from the area adjoining said slot.

11. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a small opening into such a soluble deposit from a breast near the upper boundary of the bed and approximately parallel thereto, circulating water through a conduit extending through the opening and having its outlet at the end thereof remote from the breast, removing resulting solution from another conduit having its intake at a point near the breast in an action in which a vertically ranging slot is formed in the deposit, reversing the circulation of Water into the opening through said conduits so as to leach out soluble material of the deposit from the area adjoining said slot, and finally reversing the circulation through said conduits a second time when the dissolved content drops below a predetermined minimum value.

12. The method of mining a water-soluble mineral from an underground deposit lying between layers of other water-soluble material of different composition, which comprises forming a small opening into such a soluble deposit from a breast near the upper boundary of the bed and approximately parallel thereto, circulating water through a conduit extending through the opening and having its outlet at the end thereof remote from the breast, removing resulting solution from another conduit having its intake at a point near the breast in an action in which a vertically ranging slot is formed in the deposit, and thereafter periodically reversing the direction of circulation through said conduits as the solubility of the resulting solution falls below a predetermined minimum value.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 508,523 Mitchell Nov. 14, 1893 2,161,800 Cross June 13, 1939 2,200,665 Bolton May 14, 1940 2,365,591 Ranney Dec. 19, 1944 FOREIGN PATENTS Number Country Date 89,840 Austria Oct. 25, 1922 135,722 Germany Nov. 4, 1902 235,723 Germany June 20, 1911 445,977 Germany June 20, 1927

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