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

Patent metadata

Field	Value
Publication number	US-2016356138-A1
Application number	US-201314062875-A
Country	US
Kind code	A1
Filing date	Oct 24, 2013
Priority date	Oct 25, 2012
Publication date	Dec 8, 2016
Grant date	—

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.

First claim

1 . In an underground formation containing an evaporite mineral stratum comprising a water-soluble mineral, said evaporite mineral stratum lying immediately above a water-insoluble stratum of a different composition, said formation comprising a defined parting interface between the two strata and above which is defined an overburden up to the ground,
a method for sealing undesirable fractures in the evaporite stratum during lithological displacement, comprising (a) applying a hydraulic pressure which is greater than the overburden pressure at the interface to lithologically displace the evaporite stratum, thereby forming a gap between the strata and exposing a main mineral free-surface, wherein said application of hydraulic pressure is carried out by injecting a lithological displacement fluid for its flow to further induce formation of new undesirable transverse fractures and/or to intersect natural undesirable transverse fractures in the evaporite stratum, thereby exposing minor mineral free-surfaces in said undesirable fractures; (b) flowing a sealing agent into the gap and into the transverse fractures; and (c) maintaining such sealing agent in said gap and said transverse fractures to form a solidified matter inside said transverse fractures and in said gap.

2 . The method according to claim 1 , wherein the sealing agent is an aqueous solution, a slurry, or a gel, said slurry or gel comprising an aqueous phase in which particles are suspended, wherein said aqueous solution or aqueous phase is saturated in at least one sodium compound selected from the group consisting of sodium carbonate, sodium bicarbonate, and combinations thereof, or said particles comprises at least one compound selected from the group consisting of sodium carbonate, any hydrated form thereof, sodium bicarbonate, sodium sesquicarbonate, and combinations thereof; or both.

3 . The method according to claim 1 , wherein said sealing agent comprises water-insoluble particles, said water-insoluble particles comprising at least one water-insoluble calcium compound, fused or colloidal silica, water-insoluble matter recovered from a mechanically-mined mineral after its dissolution in water or aqueous medium, tailings recovered from a mineral surface refinery, biological solid matter, agricultural solid matter, sand, cement, or combinations thereof.

4 . The method according to claim 1 , wherein the sealing agent comprises a thixotropic gel comprising particles in colloidal suspension in an aqueous phase.

5 . The method according to claim 1 , wherein the solidified matter is formed in step (c) by at least one mechanism selected from the group consisting of crystallization, precipitation, compaction, agglomeration, coagulation, cross-linking, wall-building, cementation, and combinations of two or more thereof.

6 . The method according to claim 1 , wherein the solidified matter is formed in step (c) by at least crystallization or precipitation of the at least one sealing agent component to form at least a portion of the solidified matter.

7 . The method according to claim 1 , wherein the sealing agent comprises a slurry or gel comprising particles in suspension in a liquid phase, and wherein the sealing of the fractures by the solidified matter in step (c) is effected by at least compaction or agglomeration of said particles to form at least a portion of the solidified matter.

8 . The method according to claim 1 , wherein the sealing of the fractures by the solidified matter in step (c) is effected by at least coagulation or cross-linking between various components of the sealing agent under in situ conditions favoring reactions between these various components so as to form ionic or covalent bonds between these components and to form at least a portion of the solidified matter.

9 . The method according to claim 1 , wherein the solidified matter is formed during step (c) by at least binding or bonding of at least one component of the sealing agent with the mineral in the free mineral surfaces created during step (a) to form a wall-building solidified matter in the gap and fractures.

10 . The method according to claim 1 , wherein the steps (a) and (b) are performed at the same time by injecting the sealing agent to apply said hydraulic pressure at the strata interface and for its flowing into said interface gap and said undesirable fractures.

11 . The method according to claim 1 , wherein the steps (a) and (b) are performed sequentially, step (a) being carried out by injecting a lithological displacement fluid comprising water or consisting of water to apply said hydraulic pressure at the strata interface to form said interface gap and said undesirable transverse fractures; and wherein, after evacuating the lithological displacement fluid used in step (a), step (b) is carrying out by flowing the sealing agent into said undesirable transverse fractures and said gap.

12 . The method according to claim 1 , wherein the hydraulic pressure is applied in step (a) by using a fracture gradient between 0.9 psi/ft (20.4 kPa/m) and 1.5 psi/ft (34 kPa/m).

13 . 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.

14 . The method according to claim 1 , wherein step (c) is carried out to seal at least 50% by volume of the transverse fractures.

15 . The method according to claim 1 , wherein the evaporite mineral stratum is at a shallow depth of 2,500 feet or less.

16 . The method according to claim 1 , wherein the defined parting interface is horizontal or near-horizontal.

17 . 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.

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

19 . The method according to claim 1 , further comprising:
(d) releasing the hydraulic pressure to squeeze out a layer of solidified matter formed in the gap and/or any remaining unsolidified sealing agent out of the gap.

20 . The method according to claim 1 , further comprising:
injecting a flushing agent to remove at least a portion of a layer of solidified matter from the gap and/or to flush away any remaining unsolidified sealing agent out of the gap.

21 . The method according to claim 1 , further comprising:
after step (c) or after a flushing step, injecting a propping fluid to maintain free fluid paths inside the gap, wherein said flushing step comprises injecting a flushing agent to remove at least a portion of a layer of solidified matter from the gap and/or to flush away any remaining unsolidified sealing agent out of the gap.

22 . 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 according to claim 1 to solution mine the evaporite stratum and to dissolve mineral from the main mineral free-surface created at the strata interface into an aqueous solvent to obtain a brine comprising sodium carbonate, sodium bicarbonate, or both, and passing at least a portion of said brine through one or more units selected from the group consisting a cry

Assignees

• Solvay

Inventors

• Hughes Ronald O
• Cheese Bradley D
• Paperini Matteo
• Ortego Beatrice C

Classifications

• E21B43/28 Primary

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

• C01D7/14

  Preparation of sesquicarbonates · CPC title

• E21B43/281 Primary

  using heat · CPC title

• C01D5/14

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

• C01D7/24

  Crystallisation · CPC title