METHODS OF IMPROVED CAVERN RUBBLIZATION FOR ENHANCED POTASH RECOVERY

Abstract

Methods for cavern rubblization for enhanced potash recovery are disclosed. In embodiments, such a method includes pressure cycling. The method can include pressurizing a cavity to maximum flow capacity followed by rapid relief of the cavity pressure. In this embodiment, this cycle of pressurization and rapid relief is repeated several times. Other embodiments of cavern rubblization and methods for enhanced potash recovery, a technique of fluid pulsing is used. According to embodiments, a tool can be used to pulse pressure through clay seams to be wetted. According to both embodiments, these methods increase potash recovery during mining.

Claims

1. A method for recovery of potash from sedimentary rock, the method comprising: providing first and second bore holes in fluid communication with a cavity defined by walls containing ore; injecting a fluid into the first and second bore holes and cavity to pressurize the cavity to produce an operating pressure, wherein the ore is soluble in the fluid; increasing a pressure of the bore hole and cavity above the operating pressure by injecting fluid until the cavity cannot take on any more fluid; and rapidly relieving the pressure in cavity via the first and second bore holes, thereby causing the cavity to collapse inwardly.

2. The method of claim 1, wherein the fluid is water or brine.

3. The method of claim 1, wherein increasing the pressure of the bore hold and cavity causes the cavity to expand.

4. The method of claim 1, the method further comprising removing the fluid from the first and second boreholes and cavity, and recovering potash in solution from the fluid.

5. The method of claim 1, further comprising: repeating the steps of injection of the fluid, increasing the pressure of the bore hole and cavity, and rapidly relieving the pressure, at least two times.

6. The method of claim 1, further comprising: before the first and second boreholes cavity are pressurized to the operating pressure, subjecting the fluid to fluid pulsing.

7. The method of claim 6, wherein subjecting the fluid to fluid pulsing comprises inserting a tool configured to generate mechanical pulses into one of the first and second boreholes at a location proximate a clay seam in the sedimentary rock, and generating fluid pulses, wherein the fluid penetrates a wall of the first or second borehole to wet the clay seam.

8. The method of claim 1, wherein the recovery of potash increases by at least 10%.

9. A method for recovery of potash from sedimentary rock, the method comprising: providing first and second bore holes in fluid communication with a cavity containing ore; injecting a fluid into the first and second bore holes and cavity; and subjecting the fluid to fluid pulsing before removing the fluid.

10. The method of claim 9, wherein subjecting the fluid to fluid pulsing comprises: inserting a tool configured to generate mechanical pulses into one of the first and second boreholes at a location proximate a clay seam in the sedimentary rock; and generating fluid pulses, wherein the fluid penetrates a wall of the first or second borehole to wet the clay seam.

11. The method of claim 9, wherein the fluid is water or brine.

12. The method of claim 9, further comprising: after fluid pulsing, pressurizing the cavity to an operating pressure to fracture the clay seam.

13. The method of claim 12, further comprising: removing the fluid from the first and second boreholes and cavity, and recovering potash in solution from the fluid.

14. The method of claim 11, further comprising: after subjecting the fluid to fluid pulsing, subjecting the cavity to pressure cycling.

15. The method of claim 14, wherein subjecting the cavity to pressure cycling comprises: increasing a pressure of the bore hole and cavity above the operating pressure by injecting fluid until the cavity cannot take on any more fluid; and rapidly relieving the pressure in cavity via the first and second bore holes, thereby causing the cavity to collapse inwardly.

16. The method of claim 15, wherein increasing the pressure and rapidly relieving the pressure is repeated at least two times.

17. The method of claim 9, wherein the recovery of potash increases by at least 10%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which:

[0018] FIG. 1 is a diagram depicting depth comparisons of potash ore.

[0019] FIG. 2 is a diagram depicting cavity development configuration in solution mining.

[0020] FIG. 3 is a diagram depicting cavity configuration before rubble fracturing.

[0021] FIG. 4 is a depicting cavity configuration after rubble fracturing.

[0022] FIG. 5 is a diagram depicting cavity configuration before and after pressure is applied to clay seams to achieve rubble fracturing with the cavity.

[0023] FIG. 6 is a diagram depicting a cavity subjected to pressure expansion according to a method of the present invention.

[0024] FIG. 7 is a table depicting a potash recovery in grams per liter according to a method of the present invention.

[0025] FIG. 8 is a diagram depicting a cavity subjected to fluid pulsing according to a method of the present invention.

[0026] While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027] According to embodiments of a method for increased cavern rubblization for enhanced potash recovery illustrated in FIGS. 6 and 8, a well 108 is connected to a cavity 112 containing ore. According to some embodiments, clay seams 104 are present in cavity 112. According to embodiments of the invention, cavern rubblization for enhanced potash recovery can comprise pressure cycling 100, as depicted in FIG. 6, and/or fluid pulsing 200, as depicted in FIG. 8.

[0028] According to one embodiment of a method of cavern rubblization for enhanced potash recovery as depicted in FIG. 6, a technique of pressure cycling 100 can be used. According to one embodiment of this method, a well 108 is pressurized to above typical operating pressures using available production streams. Pressurization of well 108 causes cavity 112 to expand as depicted in FIG. 6. According to an embodiment of the method, pressure of cavity 112 is then stabilized. After pressure stabilization, pressure in cavity 112 is relieved out of well 108 as quickly as possible, allowing cavity 112 to collapse inward as the pressure holding cavity 112 in expansion is removed. According to an embodiment of the method, the rapid collapse of cavity 112 destabilizes clay seams 104, allowing additional ore 114 to fall into a void below. According to embodiments of this method, several cycles of pressurizing and depressurizing well 108 can be performed to achieve desired ore rubblization.

[0029] FIG. 7 depicts potash recovery amounts in % grams per liter according to embodiments. This figure illustrates the results of potash recovery using pressure cycling according to embodiments of the method. Pressure cycling was experimentally performed on four wells currently in production, A, B, C, D, and on three new wells, E, F, and G. Results of using pressure cycling according to embodiments of the method indicate that on wells currently in potash production, the use of pressure cycling increased potash recovery. Potash recovery on new potash wells was also increased in caverns E and F (based on average of A-D before pressure cycling), and potash recovery in cavern G was a confirmed wipe liner.

[0030] According to embodiments, the method of pressure cycling may be used in combination with methods of traditional rubblization fracturing practices described above. In alternative embodiments, the method of pressure cycling is not used in combination with methods of traditional rubblization fracturing practices.

[0031] According to an embodiment of a method of cavern rubblization for enhanced potash recovery as depicted in FIG. 8, a technique of fluid pulsing 200 may be used. The method of fluid pulsing 200 uses tool 202 capable of generating mechanical pulses to aid in wetting of clay seams 104 according to embodiments. According to one embodiment of the technique depicted in FIG. 8, the method comprises a technique of fluid pulsing 200 using a tool 202 that allows clay seams 104 to be wetted out further past injection point 206.

[0032] In this embodiment, a cavity is first developed according to traditional solution mining cavity development methods as described above. According to embodiments various techniques and equipment are used to enable the flow of fluids into and out of cavity 112 at different elevations to create the desired cavity configuration as depicted in FIG. 2. The final stage of cavity development is rubble fracturing.

[0033] In the method of rubble fracturing according to embodiments of the invention depicted in FIG. 8, tool 202 is lowered into well 108 to the targeted clay seam and is supplied with full system pressure. Tool 202 provides a pulsing of pressure that ripples through clay seams 104 that is to be wetted. According to embodiments, wetting clay seam 104 is achieved by modifying downhole piping to allow liquid or fluid at a constant pressure to come into contact with clay seams 104. In the most preferred embodiment, targeted pressure exerted from tool 202 ceases after clay seam 104 is wetted to the point of fracture. In other embodiments pressure exerted from 102 may apply pressure to clay seam 104 until fracture occurs. In yet even other embodiments, targeted pressure exerted from tool 202 may cease prior to clay seam 104 reaching point of fracture.

[0034] According to the embodiment depicted in FIG. 8, water migrates outward from injection site 210 and is absorbed by clay seam 104. Increased absorption of water by clay seam 104 reduces the clay's strength by dissolving any salts within the clay and by the swelling effect of water saturated clay. After water migration has wetted the clay seam, cavity 112 is pressurized to typical operating pressures for clay seam 104 fracturing to occur.

[0035] According to some embodiments of methods of cavern rubblization for enhanced potash recovery, fluid pulsing 200 may be used in combination with pressure cycling 100. In an alternative embodiment, fluid pulsing 200 is not used in combination with pressure cycling 100. In even other embodiments fluid pulsing 200 is used with traditional methods of cavern pressurization.

[0036] Success of this tool has also been measured as above normal potash mining immediately after and over the remaining life of the cavity, signifying that an increased amount of potash was fractured into the lower zone of the cavity where the mining occurs.

[0037] Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

[0038] Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted.

[0039] Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended.

[0040] Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein.

[0041] For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. ? 112(f) are not to be invoked unless the specific terms means for or step for are recited in a claim.