In situ method for sealing undesirable transverse fractures under hydraulic pressure during lithological displacement of an evaporite deposit

a technology of lithological displacement and in situ method, which is applied in the preparation of alkali metal sulfite, alkali metal carbonates, borehole/well accessories, etc., can solve the problems of increasing the difficulty of recovering trona by mechanical mining methods, affecting the production cost of soda ash, and affecting the quality of trona

Inactive Publication Date: 2016-12-08
SOLVAY SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0043]To allow for the development of a bottom-up solution mining approach of shallow-depth evaporite beds (e.g., trona beds) to dissolve the desired solute (e.g., sod

Problems solved by technology

The cost of the mechanical mining methods for trona is high, representing as much as 40 percent of the production costs for soda ash.
Furthermore, recovering trona by these methods becomes more difficult as the thickest beds (more readily accessible reserves) of trona deposits with a high quality (less contaminants) were exploited first and are now being depleted.
Thus the production of sodium carbonate using the combination of mechanical mining techniques followed by the monohydrate process becoming more expensive, as the higher quality trona deposits become depleted and labor and energy costs increase.
Furthermore, development of new reserves is expensive, requiring a capital investment of as much as hundreds of million dollars to sink new mining shafts and to install related mining and safety (ventilation) equipment.
These insoluble contaminants not only cost a great deal of money to mine, remove, and handle, they provide very little value back to the mine and refinery operator.
Implementing a solution mining technique to exploit sodium (bi)carbonate-containing ores like trona ore, especially those ores whose thin beds and/or deep beds of depth greater than 2,000 ft (610 m) which are currently not economically viable via mechanical mining techniques, has proven to be quite challenging.
This method however proved unsuccessful and currently there are two approaches to trona solution mining that are being pursued.
Even though solution mining of remnant mechanically mined trona is one of the preferred mining methods in terms of both safety and productivity, there are several problems to be addressed, not the least of which is the resource itself.
When current trona target beds will be completely mechanically mined, the operators will eventually b

Method used

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  • In situ method for sealing undesirable transverse fractures under hydraulic pressure during lithological displacement of an evaporite deposit
  • In situ method for sealing undesirable transverse fractures under hydraulic pressure during lithological displacement of an evaporite deposit
  • In situ method for sealing undesirable transverse fractures under hydraulic pressure during lithological displacement of an evaporite deposit

Examples

Experimental program
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Effect test

example 1

[0358]A solution saturated in sodium bicarbonate was made by dissolving 425 g NaHCO3 in 2.5 liters of water. The solution was heated to 65° C. and decanted to remove excess sodium bicarbonate crystals. This saturated solution was used as a sealing agent in a sealing test performed on a solid 1.7-kg trona block from bed No. 17 in Green River, Wyo. One hole of ¼-inch in diameter and 1.5-inch in depth and a second hole of ⅛-inch in diameter and 1.125-inch in depth were drilled into the trona block. The block was submerged into the saturated solution at 65° C. The solution was allowed to cool at room temperature (19° C.) to precipitate sodium bicarbonate. Aliquots of the solution were taken out for a double endpoint titration measuring sodium carbonate and bicarbonate in the remaining solution were performed over time. At the same time, temperature of the remaining solution was measured. When the solution temperature dropped to about 36° C., crystals started to form and covered the tron...

examples 2 to 7

[0361]Six sealing tests were performed on another solid trona block from bed No. 17 in Green River, Wyo. Six holes of ⅛-inch in diameter and 2-inch in depth were drilled into the trona block.

[0362]A solution saturated in sodium carbonate and a supersaturated sodium carbonate slurry were made. Solid sodium carbonate was added to water heated at 65° C. in an amount exceeding the solubility limit of sodium carbonate at 65° C. The mixture was allowed to settle; the supernate provided the saturated solution of sodium carbonate while the settled solids with some of saturated solution provided the slurry of sodium carbonate. Similar saturated solutions and slurries were made for sodium sesquicarbonate and sodium bicarbonate.

[0363]An aliquot for each saturated solution / slurry was added to one of the six holes. The solutions / slurries were left to cool for 24 hours, and the openings of the holes were observed for presence of crystals formation.

[0364]All three holes which received slurries wer...

example 8

[0368]Several small (¼-inch diameter) holes were drilled in a block of trona, and trona insolubles (tailings) were injected into the holes. The insolubles used in this example were taken from a thickener underflow in a soda ash refinery, and had around 12% by Total Alkalinity as Na2CO3; about ⅓ of the volume are insoluble fines. This material set up much slower than previously tested materials and did not bond to the trona walls. The resulting plug was brittle.

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Abstract

Methods for sealing undesirable transverse fractures enlarged and/or created during lithological displacement of an underground water-soluble evaporite stratum by hydraulic pressure greater than overburden pressure at an evaporite/non-evaporite strata interface, comprising injecting and maintaining a sealing agent into these undesirable fractures to form a solidified matter in situ and ultimately seal them, while forming a main free surface at the interface suitable for initiating solution mining of the evaporite stratum. The solidified matter may be crystallized, precipitated, compacted, agglomerated, cross-linked, coagulated, water-swollen, and/or cemented matter, or may include a wall-building matter with the mineral on fracture faces. The sealing agent may comprise at least one component of the mineral and/or the non-evaporite. The evaporite stratum is preferably a trona stratum overlying an oil shale stratum. The sealing agent may comprise dissolved and/or solid trona, trona tailings particles, and/or water-swelling particles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims priority benefit to U.S. provisional application No. 61 / 718,212 filed on Oct. 25, 2012, this application being herein incorporated by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.TECHNICAL FIELD OF THE INVENTION[0003]The present invention relates to a sealing agent composition, methods for lithological displacement of an underground evaporite mineral deposit using such sealing agent to seal undesirable pre-exiting fractures and / or fractures created during application of hydraulic pressure, and methods for in situ solution mining of the lithologically-displaced evaporite mineral deposit. In particular, the present invention relates to a method for sealing undesirable pre-existing fractures and / or fractures created in a trona bed during application of hydraulic pressure at a trona / shale interface using such sealing agent in order to form a prefer...

Claims

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Application Information

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IPC IPC(8): E21B43/28
CPCE21B43/28C01D7/14E21B43/281C01D5/14C01D7/24
Inventor HUGHES, RONALD O.CHEESE, BRADLEY D.PAPERINI, MATTEOORTEGO, BEATRICE C.
Owner SOLVAY SA
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