WO2016091384A1

WO2016091384A1 - Preparation and use of non-aqueous brines

Info

Publication number: WO2016091384A1
Application number: PCT/EP2015/002480
Authority: WO
Inventors: Olivier Porcherie; Jean-Philippe Caritey; Fabiola ALEXIS
Original assignee: Schlumberger Canada Limited; Schlumberger Technlology B.V.; Schlumberger Holding Limited; Services Petroliers Schlumberger; Prad Research And Development Limited; Schlumberger Technlology Corporation
Priority date: 2014-12-09
Filing date: 2015-12-08
Publication date: 2016-06-16
Also published as: AR102953A1

Abstract

The applications relates to preparation of brines using non-aqueous solvents and methods of use thereof in oilfields.

Description

PREPARATION AND USE OF NON-AQUEOUS BRINES

BACKGROUND

Natural brines are waters with very high to extremely high concentrations of dissolved constituents— elements, ions, and molecules. Brines are commonly considered to be those waters more saline, or more concentrated in dissolved materials, than sea water (35 grams of dissolved constituents per kilogram of sea water). Brine can contain salt concentrations more than five times greater than the salt content of average sea water. Natural mixtures of brines, sea water, and fresh waters occur at various locations.

Owing to high concentrations of dissolved components such as sodium and magnesium, brines are of commercial interest, especially in the production of table salt. Subsurface caverns (especially those used for the mining of table salt), saline lakes (e.g., the Great Salt Lake, the Dead Sea, the Salton Sea), and the saltwater ocean are three principal sources of brine. Despite their economic value in some circumstances, brines may cause considerable trouble where they leak into potable (drinkable) water supplies or contaminate water for animals, crops, gardens, and other landscaped terrains.

Natural brines are commonly found at depth in the Earth, but they also are found at Earth's surface, most notably as a byproduct of oil and gas test wells and production wells; hence they are known as oil-field brines. As petroleum and gas is commercially produced, brines may be produced in large quantities. In oil fields that have been producing for long periods of time, such as in central and west Texas, wells may produce many barrels of brine for every barrel of oil.

Brines, both natural and specifically mixed, are used frequently in oil and gas production, including in drilling fluids, in well completions, workovers, enhanced oil production, and the like. Further, it is usually co-produced along with the oil in many enhanced oil recovery fields.

For example, the emulsified calcium chloride [CaCl₂] solution (or any other saline phase) in an oil mud is referred to as "brine" or "brine phase." The oil/brine ratio, abbreviated OBR, is used to compare solids content and salinities of oil muds. Clear brines are salt solutions that have few or no suspended solids. In well completions, the brine is a water-based solution of inorganic salts used as a well-control fluid during the completion and workover phases of well operations. Clear brines preferred, containing no particles that might plug or damage a producing formation. In addition, the salts in brine can inhibit undesirable formation reactions such as clay swelling. Brines are thus typically formulated and prepared for specific conditions, with a range of salts available to achieve densities ranging from 8.4 to over 20 lbm/gal (ppg) [1.0 to 2.4 g/cm³]. Common salts used in the preparation of simple brine systems include sodium chloride, calcium chloride and potassium chloride. More complex brine systems may contain zinc, bromide or iodine salts. Compared to pure water, brine exhibits different properties. For example, its freezing point is decreased, which find application in thermal fluids or de-icing. Its density is increased, and this finds application in completion fluids as the CLEAR FLUID BRINES commercialized by MI SWACO™.

Brines are always made with water. However, water usage in oil and gas production is quite high, being as much a 7 barrels of water used to produce e.g., one barrel of Texas shale oil. Thus, there is a great need in the art for methods of reducing water consumption. Indeed, some estimate that managing water in the oilfield is a roughly $50 billion-a-year business in the U.S.

One way to reduce water consumption would be to formulate brines with less or without any water. However, it is well known that salts do not dissolve in organic media. The Lange's Handbook of Chemistry (J 6th Edition) [McGraw-Hill Professional Publishing, 2005] presents solubility data of various gases or salts in water. However, in this reference book, no solubility data of salts in organic solvents was found.

In order to dissolve salt in a non-aqueous fluid, the non-aqueous fluid must be polar and aprotic. However, this is often not sufficient to dissolve salt. Indeed, dimethylsulfoxide (DMSO) is a common organic solvent having these properties, but as shown in Table 1, below, it does not dissolve simple salts such as sodium chloride or potassium bromide.

Hence, there is a need in the art for a method of making novel brines and novel brine compositions that do not rely on excessive water usage as the universal solvent. Such a novel brine could greatly reduce water consumption, and allow the development of novel oilfield fluids with novels properties and uses. SUMMARY

This disclosure relates to methods of preparing a clear salt brine in a non-aqueous solvent using inorganic or organometallic salts and to methods of use thereof.

The novel brines in the present disclosure exhibit many unique properties including, but not limited to, conductivity of the non-aqueous fluid, control of the brine's density, and preparation of stable suspensions of non-soluble particles and/or polymers within the novel brines.

The novel brines can be used in hydrocarbon recovery as either an injection fluid or as one component of a formulation fluid pumped into subterranean wells. Additionally, the amount of inorganic salt dissolved can be adjusted to alter the density or viscosity of the fluids, alter the conductivity, or induce suspension of polymers, particles and the like in a fluid.

Any inorganic or organometallic salt can be used in the present methods, especially salts with Group 1 , 2 or row 4 transition metals cations and oxide, sulfide or halogen anions. Preferably, salts having sodium, potassium, cesium, rubidium, magnesium, calcium, barium, chromium, iron, nickel, copper, zinc, zirconium, silver, oxygen, sulfide, and/or any halogen are used. Most preferred are sodium, potassium, calcium, iron, and zinc with any halogen.

In some embodiments, one or more inorganic salts are used to form the brine, increase conductive of the base fluid, increase density and/or viscosity, particularly to improve stability of a suspension using a more physical method rather that the chemical methods typically utilized, or decrease sedimentation of additives up to the point when a stable suspension is obtained.

The non-aqueous fluids used as the brine base are polar organic solvents. Preferably, polar, aprotic organic solvents such as dichloromethane, tetrahydrofuran (THF), ethyl acetate, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, hexamethylphosphoric triamide (HMPT), ethers and esters are used. However, polar protic solvents from the glycol ether family, such as polyethyleneglycol and 2-butoxyethanol, can also dissolve inorganic salts. In some embodiments, SURFTREAT 9294 from Clariant Oil Services (Houston, TX) is used as the non-aqueous fluid. SURFTREAT 9294 is an alkoxylated solvent.

The disclosure includes any one or more of the following embodiments, in any combination(s) thereof: — A non-aqueous brine having at least one inorganic salt dissolved in one or more polar organic solvents. The inorganic salt can have a halogen anion and/or an alkali, alkaline earth metal or transition metal cation.

;— A non-aqueous brine having an inorganic salt chosen from NaCl, KC1, NaBr, Nal, KBr, KI, CaCl₂, CaBr₂, Cab, MgCl₂, MgBr₂, Mgl₂, FeCl₂, FeCl₃, and ZnBr₂ dissolved in at least one polar organic solvent.

— A non-aqueous brine comprising at least one organometallic salt dissolved one or more polar organic solvents. The organometallic salt can be a formate, carbonate, acetate, oxide, sulfide or sulfate anion, such as potassium formate, cesium formate, zinc carbonate, zirconium acetate.

— A method of preparing a non-aqueous brine, comprising the steps of stirring a polar organic solvent and adding a salt to a stirring polar organic solvent.

— A method of increasing the density of a non-aqueous fluid comprising adding an inorganic or organometallic salt to said non-aqueous fluid while stirring. — A method of increasing the conductivity of a non-aqueous fluid comprising adding an inorganic or organometallic salt to said non-aqueous fluid while stirring.

—A method of improving the stability of a suspension, said suspension comprising a non-aqueous carrier fluid and at least one particle to be suspended, said improvement comprising adding an inorganic salt to increase the density of said non-aqueous fluid. — A method of improving the stability of a suspension, said suspension comprising a non-aqueous carrier fluid and at least one particle to be suspended, said improvement comprising adding an organometallic salt to increase the density of said non-aqueous fluid.

— A method of improving the stability of a suspension, said suspension comprising a carrier fluid and at least one particle to be suspended, said improvement comprising adding a non-aqueous fluid and an inorganic salt to increase the density of said carrier fluid.

— In any of the above brines, at least one of the polar organic solvents is aprotic or pro tic.

— In any of the above brines, a salt is dissolved in at least one aprotic polar organic solvent chosen from dichloromethane, tetrahydrofuran (THF), ethyl acetate, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, hexamethylphosphoric triamide (HMPT).

— In any of the above brines, a salt is dissolved in glycol ether and/or another organic solvent.

— In any of the above brines^ a salt is dissolved in polyethyleneglycol and/or 2- butoxyethanol.

— In any of the above suspensions, the non-aqueous fluids is a polar aprotic and/or a polar protic solvent.

— Methods of dissolving one or more inorganic salts in non-aqueous fluids.

-— Dissolving inorganic salt in a non-aqueous fluid to induce or improve conductivity of the non-aqueous fluid.

— Dissolving inorganic salt in a non-aqueous fluid to adjust fluid density.

— Dissolving inorganic salt in a non-aqueous fluid to adjust fluid viscosity.

— Increasing the density of a formulation fluid by dissolving one or more inorganic salt.

— Dissolving an amount of inorganic salt in a formulation fluid having one or more particles or polymers such that the particles or polymers become suspended without unduly increase the viscosity of the formulation fluid.

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

Although brine has typically been defined as salts in an aqueous fluid, we propose to expand the definition herein to include non-aqueous brines that are formulated without significant amounts of water, although there may be trace amounts thereof, e.g., the solvent does not have to be an anhydrous solvent.- Thus, a "non-aqueous brine" as used herein is a mixture of an inorganic salt in a non-aqueous fluid.

By "additives" what is meant is any additive added to a fluid for use in an oil-and-gas reservoir. Hundreds of such additives are known, including retardants, accelerants, surfactants, emulsifiers, dispersants, wetting agents, buffers, fluid loss control agents, anti-settling, anti- corrosion agents, acids, polymers, crosslinkers, viscosifiers, gels, gel breakers, foaming agents, anti-foaming agents, defoamers, biocides, chelating agents, salts, various polymers, migration additives, heavyweight additives, and weight-reducing additives to name a few.

By "oilfield fluid" what is meant is any fluid used in a reservoir.

The following abbreviations are used herein:

The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims or the specification means one or more than one, unless the context dictates otherwise.

The term "about" means the stated value plus or minus the margin of error of measurement or plus or minus 10% if no method of measurement is indicated.

The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or if the alternatives are mutually exclusive.

The terms "comprise", "have", "include" and "contain" (and their variants) are open- ended linking verbs and allow the addition of other elements when used in a claim.

The phrase "consisting of is closed, and excludes all additional elements.

The phrase "consisting essentially of excludes additional material elements, but allows the inclusions of non-material elements that do not substantially change the nature of the invention, such as varying buffers, matrixes, sample dilutions, and the like.

DESCRIPTION OF FIGURES

Embodiments of PREPARATION AND USE OF BRINES are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components.

FIG 1 displays backscattered light collected over four minutes on 10% wt suspension of diutan gum in 2-butoxyethanol adjusted at 1.43 g/cm³.

FIG. 2 displays backscattered light collected over four days on 10% wt suspension of diutan gum in 2-butoxyethanol (d=0.89 g/cm³). DETAILED DESCRIPTION

At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. In addition, the methods, devices, and systems used/disclosed herein can also comprise some components other than those cited. Also, in the summary of the disclosure and this detailed description, it should be understood that a concentration range listed or described as being useful, suitable, or the like, is intended that any and every concentration within the range, including the end points, is to be considered as having been stated. For example, "a range of from 1 to 10" is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific numbers, it is to be understood that any and all data points within the range are to be considered to have been specified.

This disclosure considers using clear non-aqueous brines as unique injection fluid, or as a component of a oilfield fluid, which is pumped into subterranean wells, during drilling, completion, fracturing, workovers, production or enhanced oil recovery operations.

In a first embodiment, this disclosure describes the preparation of clear non-aqueous brines by dissolving one or more inorganic salts into a non-aqueous fluid.

In a second embodiment, this disclosure describes the usage of dissolving inorganic salt in non-aqueous fluid to obtain conductive non-aqueous fluids. In a third embodiment, this disclosure describes the usage of dissolving inorganic salts in a non-aqueous fluid to adjust fluid density. It is known that dissolving salt in water will affect its density. For example, seawater has higher density than deionized water. This property is also used in engineering to adjust the density of brines, as for example the CLEAR BRINE FLUIDS used as completions fluids by M-I SWACO. However, to our knowledge, no density-adjusted non-aqueous brine is described in the public literature. In a further embodiment, this disclosure describes the usage non-aqueous brines to prepare stable and homogeneous liquid suspensions. Indeed, due to gravity, suspended particles in a liquid tend to settle. In the present embodiment, particles can be either inorganic particles or organic particles or hybrid organic-inorganic particles, including polymers, and must not solubilize in the carrier fluid or the brine. To avoid sedimentation, people of the art usually increase viscosity of the carrier fluid at low-end shear rates to leverage carrying capabilities. For dense particles, higher amount of a viscosifier is required to stabilize the suspension, which can limit the suspension's usage in some cases because the viscous suspension is unable to flow and reduces pump efficiency or even stop the pumps. The following examples describe applications of the methods and systems of the current application for making and using non-aqueous brines in various oilfield applications. However, people skilled in the art should understand the methods, compositions, and systems of the current application can also be applied to other technologies.

NON-AQUEOUS BRINES The preparation of clear non-aqueous brines relies on determining the appropriate nonaqueous fluid with the appropriate inorganic salt or combination of inorganic salts.

It is well-known that inorganic salts can be dissolved in water. This property is relied on in liquid-liquid extractions to improve separation of the two immiscible fluids in organic chemistry, wherein the addition of inorganic salts to the aqueous phase improves the separation between the two phases and thus molecule extraction.

However, most non-aqueous fluids do not dissolve inorganic salts. The is evidenced by Lange's Handbook of Chemistry (16th Edition), edited by McGraw-Hill Professional Publishing in 2005, which presents solubility data of various gases or salts in water, but no solubility data of salts in organic solvents was found. In theory, only aprotic and polar fluids, such as dimethylsulfoxide (DMSO), have the ability to dissolve salts. However, as illustrated in Table 1, even in DMSO, simple inorganic salts such as sodium or potassium chloride or sodium bromide are not dissolved by DMSO. Only small amounts of potassium bromide can be dissolved in polyethyleneglycol (Mw) or 2- butoxyethanol. Other salts, such as cesium formate, were more successfully dissolved in 2- butoxyethanol. However, none of these examples were concentrated enough to be considered a brine.

Furthermore, despite the presence of organic moieties, organic salts such as organic carbonate can also not be dissolved in the selected polar and aprotic solvents.

Thus, it is not obvious to dissolve salts in polar and aprotic non-aqueous fluids. Yet, as shown herein, we have taught how to dissolve inorganic salts in e.g., various polar aprotic and protic solvents.

Table 2 shows some examples where inorganic salts were dissolved in non-aqueous fluid, leading to "non-aqueous brines". For example, it was possible to add up to 1000 g of calcium iodide in 1 L of 2-butoxyethanol, simply by pouring the salt into a stirring solvent.

Table 2: Solubility of different salts in various non-aqueous fluids at 23°C [g/L]

Solvent / . E 1 F

Salt ηΒΓ2 aCl₂ aBr2 ah aCl₂ eCl₂ eCb

DMSO - -

80 10 50

Polyethyl - - eneglycol 25· 5 00

2- 1 - 1 butoxyethanol 00 50 50 000 00 50

SURFTR - -

EAT 9294 00

While Tables 1 and 2 provide a few examples of salt solubility in different non-aqueous fluids, they were not intended to measure solubility of all salts in all solvents, but only to show that it is not obvious to dissolve salt in such non-aqueous fluids, even if they fill the requirements of being polar and aprotic. These tables, especially Table 2, show that it is possible to prepare clear non-aqueous brines by finding the appropriate inorganic salts and fluid combination. It is also possible to dissolve different salts in a high enough quantity to prepare a non-aqueous brine.

Choice of the non-aqueous fluid and of the salt should be based not only on their compatibility, but also on Health, Safety and Environment (HSE) requirements, such as environmental regulation, non-flammable liquids, and the like.

These non-aqueous brines have many of the same properties of aqueous brines such as increases in the electrical conductivity, increases in density, and decreases in freezing points. However, in testing the clear non-aqueous brines provided in Table 2, it was discovered that the non-aqueous brines exhibit some unusual properties when compared to aqueous brines. Among these unique properties are the ability to control the brine density and viscosity by augmenting the amount of salt added and ability to suspend undissolved additives with minimal increases in viscosity. Furthermore, these unique properties could be exploited to expand the use of the nonaqueous brines in oil and gas applications. Exploitation of these properties is discussed below.

CONDUCTIVITY OF NON-AQUEOUS FLUIDS

The electrical conductivity of fluids is associated to the mobility of charged molecules in the media. For very pure water, due to very low concentration of ions, conductivity is very low and equal to 0.04205 μΒ.αη^"1 [Lange's Handbook of Chemistry (16th Edition), McGraw-Hill Professional Publishing, 2005, p. 1.417]. Conductivity of water can be increased by dissolving salts.

For non-aqueous fluids, electrical conductivity is also very low (except for ionic liquids). For example, electrical conductivity of 2-butoxyethanol is 0.1 μΒ πι^"1 at 23°C measured with a SevenMulti conductimeter from Mettler-Toledo.

Like aqueous brines, the electrical conductivity of non-aqueous fluids can be increased by dissolving inorganic salts. Table 3 shows that dissolution of ZnBr₂ in 2-butoxyethanol leads to a conductivity increase, which depends on the salt concentration. However, the conductivity does not evolve linearly with the concentration of dissolved salt.

This increase in conductivity is experienced in non-aqueous fluids with suspended compounds. In one example, the dissolution of 14 g of ZnBr₂ in 20 mL of a 10%-wt suspension of acrylamide/2-Acrylamido-2-methylpropane sulfonic acid, sodium salt copolymer in 2- butoxyethanol increases the conductivity from 0.1 μβ.ατι^"1 to 60.0 μ8 Γη^"' at 21.8°C.

In yet another example, the dissolution of 1 g of ZnBr₂ in 20 mL of a 10%-wt of diutan in 2-butoxyethanol, increases the ^' electrical conductivity of the suspension from 4.8 to 72.9 μΒ ηι^"1 at 23°C. An increase in conductivity is expected with increasing the amount of ZnBr₂. Thus, the dissolution of a suitable salt in 2-butoxyethanol suspensions of synthetic or bio-based copolymers allows increasing the conductivity of such suspensions.

These examples illustrate that an increase in the conductivity of pure non-aqueous fluid or non-aqueous suspensions can be seen by dissolution of an appropriate salt.

DENSITY OF NON-AQUEOUS FLUIDS

Table 2, above, shows that salt can be selected to be dissolved in the appropriate nonaqueous fluids. However, we have found that, much like aqueous brines, the concentration of salts dissolved in the non-aqueous brine can control the density of the fluid. Table 4 provides some examples of maximal density obtained by dissolving the appropriate salt in the corresponding non-aqueous fluid.

Table 4: Maximal density (g/cm i^:3) of clear non-aqueous brines at 23°C

Solvent / F

Salt one nBr2 aCl₂ aBr₂ al₂ eCl₂ eCl₃

DMSO -

.09 .58 .18 .41

Polyethyl - - eneglycol .1 1 .42 .1 1 .37

2- - 1 butoxyethanol .89 .58 .01 .24 .47

SURFTR

EAT 9294 .44

This table illustrates the principle of increasing density of non-aqueous brines by dissolving salts in the fluid, but it is not intended to show all the possible combinations. Thus, for a desired density, the amount of salt can be adjusted or more than one salt can be combined.

PREPARING STABLE SUSPENSIONS In addition to conductivity and density control, the salts can be used to improve liquid suspensions. We have already shown above that dissolving salt in a liquid suspension can increase conductivity of the non-aqueous base fluid. However, salt can also improve the stability and homogeneity of the suspension and reduce sedimentation.

To provide a stable suspension, the density of the carrier fluid must be adjusted to match to the density of the particles to be suspended to avoid sedimentation or creaming of the particles in the carrier fluid. This methodology is applicable to aqueous and non-aqueous fluids and brines. The particle to be suspended can be an inorganic particle or an organic particle such as a polymer or a mixture of them, but it must not be soluble in the base fluid. This approach is not limited to a given particle size, although this parameter can be tuned for the application. Additionally, this method of improving suspension stability is applicable to very low or very high active content, between 0.5 to 65% by weight (or by volume). Although, the 1-40% or 2- 30% wt range of active content is preferred.

In the simplest method, the carrier fluid is a non-aqueous fluid with a density equal to the particle to suspend. For instance, hollow sphere particles having a density of 0.89 g/cm³ can be mixed in 2-butoxyethanol, which has the same density. This simple route is applicable for density lower or higher than that of water, and for non-aqueous fluids that do not dissolve the particle to suspend. However, this approach is only applicable in a given density range, since the use of higher density non-aqueous fluid is limited in oil and gas applications due to cost, limit supply and the like. Furthermore, finding a cost effective carrier fluid for each particle to suspend under given conditions (temperature) can be difficult. In one embodiment of the present disclosure, the density of the non-aqueous fluid is adjusted by dissolving the appropriate amount and nature of an inorganic salt to form a brine that is capable of suspending a desired insoluble particle. Then, this non-aqueous brine is mixed with the particle to be suspended, and/or other co-additives such as rheology modifiers or biocides either successively or simultaneously while stirring the brine. Additional salt or base fluid can be added to increase/decrease the density of the suspension after it is made.

Particles to suspend can be inorganic such as silica, barite, bentonite, sepiolite, cement, etc. or organic, such as cellulosic-based polymer, guar, xantham gum, welan gum, diutan gum, acrylic-based derivatives, any other polymers or combinations thereof. The polymer particles can be coated or agglomerated. They can have various particle sizes. The concentration of particles to suspend varies between 0.5 and 65% by volume.

As an example, suspensions of Diutan gum were made. Diutan gum is a biopolymer manufactured by Kelco CP. When dissolved in water, it imparts viscosity to the solution, even at very low concentrations, and for low-end shear rates. It is therefore not possible to prepare a liquid version of this additive in water at relatively high concentration without negatively impacting the flowability of the liquid or forming a gel. However, diutan gum is not soluble in 2-butoxyethanol. The density of the batch of diutan gum used in this example was measured with a Helium pycnometer AccuPyc II 1340 supplied by Micromeritics and was found equal to is 1.43 g/cm³.

A clear non-aqueous brine was prepared by dissolving 14.5 g of ZnBr₂ in 20 mL of 2- butoxyethanol. The densities of 2-butoxyethanol and of the brine were 0.89 g/cm³ and 1.43 g/cm³ at 25°C, respectively.

Two suspensions of diutan gum in 2-butoxyethanol were prepared. Suspension 1 was prepared by mixing 10%-wt of diutan gum in pure 2-butoxyethanol (carrier fluid density is equal to 0.89 g/cm³). Suspension 2 was prepared by mixing 10%-wt of diutan gum in the brine 2- butoxyethanol/ZnBr₂ (adjusted density of 1.43 g/cm³). The turbidity of the suspensions were measured with a Turbiscan™ LAB manufactured by Formulation at 25°C.

FIG. 1 and FIG. 2. display the backscattered light collected for suspension 1 after four minutes and 4 days. The diutan gum in suspension 1 immediately settled to the bottom of the tube. This example illustrates that it is possible to prepare suspensions in non-aqueous brine having comparable density, without adding viscosifiers. Furthermore, the stability of the suspension is not dependent on the amount of diutan gum added in the brine because the density of the carrier fluid matches that of the suspended diutan gum.

Similar results are expected for suspensions of various natural, synthetic polymers, and inorganic particles in non-aqueous and aqueous brines.

In another embodiment, the brine can also be combined with other stabilizing agents, such as viscosifiers, fibers, fine particles such as silica fume or nanocellulose, clays and all other additives known in the art to stabilize the suspensions. The combination of brine (aqueous or non-aqueous) with these commonly used stabilizing agents provides control of the suspension stability and of the rheological properties of the suspension independently.

For very dense particles, the density difference between the suspended particle and the carrier fluid can first be reduced using the dissolved salt. This means less stabilizing agent is necessary to obtain a more stable suspension, which will result in thinner suspensions. POLYMER HYDRATION

Some polymers have the property of viscosifying water, but they need to be hydrated and above a critical concentration. Hydration kinetics depends on the temperature, the nature and the size of the polymer aggregate and the environment (pH, ion concentration, etc.). Some salts such as LiCl based ionic liquids, NaOH/Urea combination are known to accelerate the hydration of the polymer. Additionally, a non-aqueous brine according to some embodiments of the present disclosure can be admixed with polymers to accelerate polymer hydration and viscosity increase.

In one example, the admixture contains the carrier fluid, one or several salts to prepare a clear non-aqueous brine, and the particle(s) to suspend. It can also contain a rheology modifier, such as a viscosifier and/or a dispersant, a biocide, an additional salt to improve hydration rate of the viscosifier, and any other additives required. The carrier fluid can be water and/or a nonaqueous fluid. Any polymer that viscosifies water but is not soluble in the choses non-aqueous fluid can be used such as cellulosic-based polymer, guar, xantham gum, welan gum, diutan gum, and/or acrylic-based derivatives. The polymer particles can be coated or agglomerated and can have various particle sizes. The concentration of particles to suspend varies between 0.5 and 65% by volume, depending on the desired final viscosity of the water.

In one example, the clear non-aqueous brine is made using a polar aprotic solvent and one or more inorganic salts having alkali earth metals and a halogen. This non-aqueous brine is then added simultaneous with the polymer into water under stirring conditions.

The examples showed in this section can be used to provide one or several properties to the resulting fluid or suspension. For example, such fluid can be prepared only to adjust conductivity or density of the fluid. But they can also be combined to adjust several properties to the same fluids, as for example, adjust the density and the conductivity of the resulting fluid. The remaining sections will discuss reservoir use of the disclosed fluids.

RESERVOIR USE - VISCOSIFIER

In a special case of the suspension described above, the non-aqueous brines can be used to prepare liquid forms of viscosifiers to be mixed with other formulation fluids. Viscosifiers are molecules or particles that increases the yield stress or the viscosity or both of the fluid in which they are mixed. Such components are used to increase the viscosity of the fluid, usually water, in which they are added. Furthermore, if the viscosifying component is chosen in liquid form, it needs to remain flowable, or in another form that is not too viscous so as to prevent injection of the final fluid down hole.

For some applications, a first route consists of dissolving the viscosifier at low concentration (below a viscosity limit compatible with application), and adding it to the final fluid. However, obviously, -the active content in this admixture is very low, which limits the application and requires high amount of admixtures to be transported, which increases the cost.

These non-aqueous brine and additives can be pumped as such in subterranean zone, or can be used as admixtures for different formulation (cement slurry, spacer, drilling fluids, etc.). Alternative, they can be used as "reactive fluid" (to react upon a stimuli such as water for water shut-off, etc.). In this context, the "reactive fluid" remains thin during pumping or placement, and viscosifies and/or gels only when it is in contact with water".

RESERVOIR USE

Any of the fluids described above can be injected as such in subterranean areas, or can be mixed with other fluids (including water-based ones) before being pumped into subterranean zones. For example, the non-aqueous brines can be used to prepare a variety of oilfield fluids that can be used e.g., in the composition of drilling fluids, spacers, cement slurries, fracturing fluids, acidizing fluids, fluids for Enhanced Oil Recovery, workover fluids, and any other fluids which are pumped into subterranean zones.

The clear non-aqueous brines can be used as completion fluids alone or in combination with other additives, including but not limited to retardants, accelerants, surfactants, emulsifiers, dispersants, wetting agents, buffers, fluid loss control agent, anti-corrosion agents, anti-settling agent, acids, polymers, crosslinkers, viscosifiers, gels, gel breakers, foaming agents, anti- foaming agents, defoamers, biocides, chelating agents, organic salts, heavyweight additives, weight-reducing additives and the like. The non-aqueous brines described above are stable and can be prepared offsite and transported to the area of interest. Such brines can also be made on site. ,

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 1 12, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words 'means for' together with an associated function.

The references made herein merely provide information related to the present disclosure and may not constitute prior art. The following references are hereby incorporated by reference herein in their entireties for all purposes:

Brine Fluids, available online at http://www.geodf.com/store/files/24.pdf

CHEMISTRY AND ORIGIN OF OIL AND GAS WELL BRINES IN WESTERN PENNSYLVANIA (2010), available online at http://www.marcellus.psu.edu/resources/PDFs/brines.pdf

Claims

CLAIMS What is claimed is:

1. A non-aqueous brine comprising at least one inorganic salt and one or more polar organic solvents, wherein said inorganic salt is dissolved in said polar organic solvent.

2. A non-aqueous brine comprising at least one organometallic salt and one or more polar organic solvents, wherein said organometallic salt is dissolved in said polar organic solvent.

3. The non-aqueous brine of any of the above claims, wherein at least one of said polar organic solvents is aprotic.

4. The non-aqueous brine of any of the above claims, wherein at least one of said polar organic solvents is protic.

5. The non-aqueous brine of any of the above claims, wherein at least one of said polar organic solvent is chosen from dichloromethane, tetrahydrofuran (THF), ethyl acetate, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, hexamethylphosphoric triamide (HMPT), glycol ether, polyethyleneglycol and/or 2- butoxyethanol.

6. The non-aqueous brine of claims Error! Reference source not found, and 3-

5, wherein said inorganic salt has a halogen anion and/or an alkali or alkaline earth metal or transition metal cation.

7. The non-aqueous brine of claims Error! Reference source not found, and

3-6, wherein said inorganic salt is chosen from NaCl, KCl, NaBr, Nal, KBr, KI, CaCb, CaBr₂, Cab, MgCl₂, MgBr₂, Mgl₂, FeCl , FeCl₃, and ZnBr₂.

8. The non-aqueous brine of claims 2 and 3-5, wherein said organometallic salt has a formate, carbonate, acetate, oxide, sulfide or sulfate anion.

9. The non-aqueous brine of claims 2 and 3-5, wherein said organometallic salt is chosen from potassium formate, cesium formate, zinc carbonate, zirconium acetate.

10. A method of preparing a non-aqueous brine, comprising a. stirring a polar organic solvent; and b. adding a salt to a stirring polar organic solvent.

1 1. A method of improving the stability of a suspension, said suspension comprising a non-aqueous carrier fluid and at least one particle to be suspended, said improvement comprising adding a salt to increase the density of said non-aqueous fluid.

12. A method of improving the stability of a suspension, said suspension comprising a carrier fluid and at least one particle to be suspended, said improvement comprising adding a non-aqueous fluid and a salt to increase the density of said carrier fluid.

13. Any of the methods in claims 1 1-12, wherein said non-aqueous fluid has at least on polar aprotic or polar protic organic solvent.

14. Any of the methods in claims 1 1 -13, wherein said non-aqueous fluid is one or more of the following: dichloromethane, tetrahydrofuran (THF), ethyl acetate, acetonitrile, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, hexamethylphosphoric triamide (HMPT), glycol ether, polyethyleneglycol and/or 2-butoxyethanol.

15. Any of the methods in claims 11-14, wherein said salt is an inorganic or organometallic salt.

16. Any of the methods in claims 1 1-15, wherein said inorganic salt has a halogen anion and/or an alkali or alkaline earth metal or transition metal cation.

17. The method of claim 16* wherein said inorganic salt is chosen from NaCl, KC1, NaBr, Nal, KBr, KI, CaCl₂, CaBr₂, Cal₂, MgCl , MgBr₂, Mgl₂, FeCl₂, FeCl₃, and ZnBr₂.

18. Any of the methods in claims 1 1-15, wherein said organometallic salt has a formate, carbonate, acetate, oxide, sulfide or sulfate anion.

19. The method of claim 18, wherein said organometallic salt is chosen from potassium formate, cesium formate, zinc carbonate, zirconium acetate.