Lithological displacement of an evaporite mineral stratum

Patent metadata

Field	Value
Publication number	US-2016356140-A1
Application number	US-201314062878-A
Country	US
Kind code	A1
Filing date	Oct 24, 2013
Priority date	Oct 25, 2012
Publication date	Dec 8, 2016
Grant date	—

Abstract

A lithological displacement of an underground evaporite mineral stratum from an underlying non-evaporite stratum comprising the application of a lifting hydraulic pressure of a fluid at a weak interface between the strata, resulting in lifting the overburden above the interface, separating the evaporite stratum from the underlying non-evaporite stratum and thus forming a mineral free-surface. The lifting hydraulic pressure is greater than the overburden pressure. The formed mineral free-surface is accessible for dissolution by a solvent. The fluid used for lifting may comprise a solvent suitable to dissolve the mineral. The evaporite mineral stratum preferably comprises trona, nahcolite, wegscheiderite, or combinations thereof.

First claim

1 . In an underground formation containing an evaporite mineral stratum comprising a mineral selected from the group consisting of trona, nahcolite, wegscheiderite, shortite, northupite, pirssonite, dawsonite, sylvite, carnalite, halite, and combinations thereof, said mineral stratum lying immediately above a non-evaporite stratum of a different composition, said formation comprising a defined weak parting interface between the two strata and above which is defined an overburden up to the ground surface,
a method for solution mining of said evaporite stratum, comprising a lithological displacement of the evaporite mineral stratum, wherein a fluid is injected at the parting interface to lift the evaporite stratum at a lifting hydraulic pressure greater than the overburden pressure, thereby forming a gap at the interface and creating a mineral free-surface, said lifting hydraulic pressure applied being characterized by a fracture gradient between 0.9 psi/ft (20.4 kPa/m) and 1.5 psi/ft (34 kPa/m); wherein the fluid is injected in a directionally drilled well which is cemented and cased; wherein said directionally drilled well comprises at least one horizontal borehole section comprising an in situ injection zone being in fluid communication with the strata interface; and
wherein the fluid injected through the well exits through the in situ injection zone of the horizontal borehole section, thereby lifting the overlying evaporite stratum at the interface so that the gap created at the interface is an extension of the horizontal borehole section.

2 . (canceled)

3 . The method according to claim 1 , wherein the lifting hydraulic pressure is from 0.01% to 50% greater than the overburden pressure at the depth of the interface.

4 . The method according to claim 1 , wherein the injected fluid is a slurry comprising particles suspended in water or an aqueous solution.

5 . The method according to claim 4 , wherein the particles in the fluid comprise tailings used as proppant.

6 . The method according to claim 1 , wherein the injected fluid is a solvent suitable for dissolving the mineral.

7 . The method according to claim 6 , wherein the injected fluid comprises an unsaturated aqueous solution comprising sodium carbonate, sodium bicarbonate, sodium hydroxide, calcium hydroxide, or combinations thereof.

8 . The method according to claim 6 , wherein the injected fluid comprises an aqueous alkaline solution.

9 . The method according to claim 1 , wherein the parting interface is horizontal or near-horizontal with a dip of 5 degrees or less.

10 . The method according to claim 1 , wherein the fluid injection is carried out via a vertical or directionally drilled well which comprises an in situ injection zone which is in fluid communication with the parting strata interface.

11 . The method according to claim 10 , wherein the fluid injection is carried out via a vertical well which is drilled from the ground surface past the depth of the interface, and wherein the vertical well is cased and cemented through its entire length, but comprises an in situ injection zone being in fluid communication with the strata interface, said in situ injection zone of said vertical well comprising a downhole end opening and/or casing perforations.

12 . (canceled)

13 . The method according to claim 1 , wherein the in situ injection zone of the horizontal borehole section comprises at least one casing opening selected from the group consisting of a downhole end opening of said horizontal borehole section, one or more casing perforations of said horizontal borehole section, and combinations thereof.

14 . The method according to claim 1 , wherein the evaporite mineral stratum comprises a water-soluble mineral selected from the group consisting of trona, nahcolite, wegscheiderite, and combinations thereof.

15 . The method according to claim 1 , wherein the evaporite mineral stratum comprises trona; and wherein the underlying stratum comprises oil shale.

16 . The method according to claim 1 , wherein the interface between the two strata is at a shallow depth of 3,000 ft (914 m) or less.

17 . The method according to claim 1 , further comprising dissolving the mineral from the created mineral free-surface into a solvent to form a brine, and to enlarge the gap to form a mineral cavity.

18 . The method according to claim 17 , wherein the mineral cavity comprises a ceiling, and wherein the mineral dissolution is carried out at a hydraulic pressure equal to or less than hydrostatic head pressure in the cavity when a layer of insolubles at the bottom of the cavity provides support for the cavity ceiling.

19 . The method according to claim 17 , wherein the mineral cavity comprises a ceiling, and wherein the method further comprises injecting a blanket medium so as to prevent dissolution of mineral from the ceiling of the cavity.

20 . A manufacturing process for making one or more sodium-based products from an evaporite mineral stratum comprises a water-soluble mineral selected from the group consisting of trona, nahcolite, wegscheiderite, and combinations thereof, which comprises:
carrying out the method for solution mining of said evaporite stratum according to claim 1 to obtain a brine comprising sodium carbonate and/or bicarbonate by dissolution of the mineral free surface by a solvent, and passing at least a portion of said brine through one or more units selected from the group consisting a crystallizer, a reactor, and an electrodialysis unit, to form at least one sodium-based product.

21 . The method according to claim 13 , wherein the in situ injection zone of the horizontal borehole section comprises one or more casing perforations of said horizontal borehole section, and
wherein the casing perforations are either:
on two generatrices of the horizontal borehole section which are aligned with the parting interface to laterally inject the fluid from both sidewalls of the horizontal borehole section; or
on one generatrix of the horizontal borehole section which is aligned with the parting interface to laterally inject the fluid from only one sidewall of the horizontal borehole section.

22 . In an underground formation containing an evaporite mineral stratum comprising a mineral selected from the group consisting of trona, nahcolite, wegscheiderite, and combinations thereof, said mineral stratum lying immediately above a non-evaporite stratum of a different composition, said formation comprising a defined weak parting interface between the two strata and above which is defined an overburden up to the ground surface,
a method for solution mining of said evaporite mineral stratum, comprising a lithological displacement of the evaporite mineral stratum, wherein a fluid is injected at the parting interface to lift the evaporite mineral stratum at a lifting hydraulic pressure greater than the overburden pressure, thereby forming a gap at the interface and creating a mineral free-surface, wherein the fluid injected at the lifting hydraulic pressure is a slurry comprising particles suspended in water or an aqueous solution; and wherein the particles in the fluid injected at the lifting hydraulic pressure comprise tailings used as proppant, said tailings being obtained during refining of mechanically-mined trona.

Assignees

• Solvay

Inventors

• Hughes Ronald O
• Paperini Matteo
• Cuche Herve
• Vendetti Joseph A
• Refsdal Larry
• Detournay Jean-Paul
• Hansen David
• Brichacek Todd
• Patterson Justin T
• Kolesar John
• Schmidt Ryan
• Ortego Beatrice C

Classifications

• C01D7/00

  Carbonates of sodium, potassium or alkali metals in general · CPC title

• C01D1/04

  Hydroxides · CPC title

• C01D7/14

  Preparation of sesquicarbonates · CPC title

• C01D5/14

  Preparation of sulfites (C01D5/04 takes precedence) · CPC title

• E21B43/28 Primary

  Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent (E21B43/241 takes precedence) · CPC title