Shale hydration inhibitor and its downhole treatment fluid

Abstract

A method of inhibiting shale swelling and / or dispersion during treatment of a subterranean shale formation, the method comprising the steps of: a) providing a subterranean treatment fluid comprising 0.001 wt% to 10 wt% of a polyester obtained by reacting a dicarboxylic acid having 2 to 8 carbon atoms with a specific alkoxylated diamine; b) introducing the treatment fluid into a wellbore at a pressure sufficient to treat the subterranean shale formation.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of inhibiting the swelling and / or dispersion of shale in a subterranean shale formation treatment (i.e. in a subterranean formation containing or releasing shale), wherein the method comprises the use of a polyester obtained by the reaction of an alkoxylated diamine and a dicarboxylic acid.

[0002] Another object of the present invention is a subterranean treatment fluid comprising said polyester. BACKGROUND

[0003] Water-based subterranean treatment fluids contain solid particles suspended in water or brine. Various other components can be added to the water-based subterranean treatment fluid intentionally or otherwise: a) organic or inorganic colloids such as clays for imparting viscosity and filtration properties; b) soluble salts or insoluble inorganic minerals for increasing fluid density; c) other optional components that can be added to impart desired properties such as dispersants, lubricants, corrosion inhibitors, defoamers or surfactants; d) formation solids that can be dispersed into the fluid during subterranean operations. For example, formation solids dispersed in a drilling fluid include cuttings from the drilling and soil and / or solids from the surrounding unstable formation. When the formation produces solids that can swell in water, such as shale, it can potentially impact drilling time and increase costs. Shale is primarily a layered aluminosilicate in which the primary structure consists of layers formed from sheets of silica and alumina that can have exposed oxygen atoms and hydroxyl groups. When atoms with different valencies are located within the layers of the structure, they create a negative potential at the surface of the layers, causing cations to be adsorbed onto them. These adsorbed cations are known as exchangeable cations because they can be exchanged chemically with other cations when the shale crystals are suspended in water. The type of substitution that occurs within the shale layers and the exchangeable cations adsorbed on the surface can affect the swelling of the shale.

[0004] There are different types of water swelling. For example, surface hydration swells by a large number of water molecules being adsorbed on the oxygen atoms exposed on the surface of the layers through hydrogen interactions. All types of shale can swell in this way.

[0005] Another type of swelling is known as osmotic swelling. When the interlayer cation concentration in the shale mineral is higher than the cation concentration in the surrounding water, water is drawn between the unit layers by osmosis. Osmotic swelling results in a greater increase in total volume than surface hydration. Shales that do not produce this interlayer swelling tend to disperse in water.

[0006] All types of shale swelling can cause a range of problems, for example, shale sticking to the drill string and drill bit, increasing the torque and drag forces between the drill string and the borehole side, wellbore sloughing or sloughing off, and causing the viscosity of the treatment fluid to increase uncontrollably.

[0007] This is why it is important to develop effective substances that reduce or block the swelling and / or dispersion of shale, i.e. shale inhibitors, for the oil and gas industry. The present invention aims to solve these difficulties.

[0008] Some patents describe techniques or compounds that can be used to inhibit shale, including inorganic salts, such as potassium chloride, polyalkyloxydiamines and salts thereof (described in US 6484821, US 6609578, US 6247543 and US 2003 / 0106718), oligomeric methylene diamines and salts thereof (described in US 5771971 and US 2002 / 0155956). However, salts flocculate clays, resulting in high fluid loss and almost complete loss of thixotropy. In addition, the increase in salinity tends to reduce the functional properties of the treatment fluid at the subsurface.

[0009] EP 2 061 856 B1 describes a method for inhibiting clay and shale hydration during drilling operations, said method comprising the use of a water-based drilling fluid containing 0.2 to 5% by weight of a condensation product of a dicarboxylic acid having 4 to 10 carbon atoms with an alkanolamine, a diamine or a polyalkyleneamine of the formula R'"R"N-R'-XH, wherein X is O or NR 0 ; R 0 is hydrogen or a linear or branched alkyl group having 1-6 carbon atoms, R' is a linear or branched aliphatic or cycloaliphatic alkylene group having 2-10 carbon atoms, or R' is R""(NH-R"")n, wherein R"" is a n-ethylene group or CH(CH3)CH2, n is a number from 1 to 6, X is NR 0 ; R" and R'" can be the same as or different from each other, are hydrogen or a linear or branched alkyl group having 1-6 carbon atoms optionally substituted with a hydroxyl group, the condensation product being in neutral form or in salt form.

[0010] Despite the various shale inhibitors that have been developed, there is still a need in the art for compounds that can be used effectively as shale inhibitors when used in subsurface treatment fluids. SUMMARY

[0011] It is therefore an object of the present invention a method for inhibiting the swelling and / or dispersion of shale during the treatment of subsurface shale formations, said method comprising the steps of:

[0012] a) providing a subsurface treatment fluid comprising from 0.001 to 10% by weight (wt%) of a polyester obtained by reacting a dicarboxylic acid having 2 to 8 carbon atoms with an alkoxylated diamine of formula (I):

[0013]

[0014] wherein:

[0015] R 1 and R 2 are the same or different and are saturated or unsaturated aliphatic C1-C4alkyl chains;

[0016] n is an integer from 1 to 5;

[0017] EO is CH2CH2O;

[0018] PO is CH2CH(CH3)O;

[0019] o, p, q and r are integers from 0 to 10, with the proviso that:

[0020] i) the sum of o, p, q and r is at least 2,

[0021] ii) o and p cannot simultaneously equal 0,

[0022] iii) q and r cannot simultaneously equal 0;

[0023] b) introducing the treatment fluid into a wellbore at a pressure sufficient to treat a subterranean shale formation.

[0024] In another aspect, the present application relates to a subterranean treatment fluid comprising an aqueous continuous phase and from 0.001 to 10 weight percent (wt%) of a polyester obtained by reacting a dicarboxylic acid having from 2 to 8 carbon atoms with an alkoxylated diamine of formula (I):

[0025]

[0026] wherein:

[0027] R1and R2are the same or different and are saturated or unsaturated aliphatic C1-C4alkyl chains;

[0028] n is an integer from 1 to 5;

[0029] EO is CH2CH2O;

[0030] PO is CH2CH(CH3)O;

[0031] o, p, q and r are integers from 0 to 10, with the proviso that:

[0032] i) the sum of o, p, q and r is at least 2,

[0033] ii) o and p cannot simultaneously equal 0,

[0034] iii) q and r cannot simultaneously equal 0.

[0035] As used herein, the term "shale" refers to a common sedimentary rock that has porosity, but very low matrix permeability. Specifically, shale is generally composed of sedimentary rock particles that are finer than sand grade (diameter < 0.0625 mm), and includes clay and silt grade materials.

[0036] As used herein, the term "clay" refers to fine-grained sedimentary rock (diameter < 0.004 mm). The most common clays include montmorillonite (bentonite), illite, kaolinite, and chlorite.

[0037] As used herein, the term "silt" refers to sedimentary rock with a grain size between clay and sand (about 0.002 mm < diameter < 0.074 mm).

[0038] As used herein, the expression "subsurface treatment" refers to any subsurface operation that uses a particular fluid in conjunction with a desired function and / or for a desired purpose. DETAILED DESCRIPTION

[0040] Preferably, the method for inhibiting shale swelling and / or dispersion during subsurface shale formation treatment comprises the following steps:

[0041] a) providing a subsurface treatment fluid comprising from 0.01 to 3% by weight (wt%) of a polyester obtained by reacting a dicarboxylic acid having 6 carbon atoms with an alkoxylated diamine of formula (I):

[0042]

[0043] wherein:

[0044] R1and R2are identical or different and are saturated or unsaturated aliphatic C1-C4alkyl chains;

[0045] n is 3;

[0046] EO is CH2CH2O;

[0047] PO is CH2CH(CH3)O;

[0048] o, p, q and r are integers from 0 to 5, with the proviso that:

[0049] i) the sum of o, p, q and r is at least 2,

[0050] ii) o and p cannot simultaneously equal 0,

[0051] iii) q and r cannot simultaneously equal 0;

[0052] b) introducing the treatment fluid into a wellbore at a pressure sufficient to treat a subsurface shale formation.

[0053] Preferably, the subterranean treatment fluid comprises an aqueous continuous phase and from 0.01 to 3 weight percent (wt%) of a polyester obtained by reacting a dicarboxylic acid having 6 carbon atoms with an alkoxylated diamine of formula (I):

[0054]

[0055] wherein:

[0056] R1and R2are identical or different and are saturated or unsaturated aliphatic C1-C4alkyl chains;

[0057] n is 3;

[0058] EO is CH2CH2O;

[0059] PO is CH2CH(CH3)O;

[0060] o, p, q and r are integers from 0 to 5, with the proviso that:

[0061] i) the sum of o, p, q and r is at least 2,

[0062] ii) o and p cannot simultaneously equal 0,

[0063] iii) q and r cannot simultaneously equal 0.

[0064] The polyester of the present application can be prepared by a two-step synthesis. In the first step, N,N-dialkylalkylene diamine is reacted with 2 to 20 moles, preferably 2 to 10 moles, of at least one alkylene oxide under a nitrogen atmosphere at a temperature of 110 to 140°C to obtain an alkoxylated diamine of formula (I). The at least one alkylene oxide can be added in a single stage or in different subsequent additions. In the second step, the alkoxylated diamine of formula (I) is reacted with a dicarboxylic acid in the presence of a suitable catalyst under stirring without any solvent at a temperature of 100-180°C and the water formed during the reaction is removed by distillation.

[0065] The alkoxylated diamine of formula (I) and the dicarboxylic acid are preferably reacted in a molar ratio of 0.8:1 to 1 :0.8. More preferably, it is reacted in a molar ratio of 1 :1.

[0066] Generally, the acid value of the polyester of the present application is from 10-150 mg OH / g.

[0067] The N,N-dialkylalkylenediamine suitable for preparing the alkoxylated diamine of formula (I) is preferably an N,N-dialkylpropylenediamine of formula R1R2N-CH2CH2CH2-NH2, wherein R1and R2are independently of each other a saturated or unsaturated aliphatic C1-C4alkyl chain. According to the present application, the most preferred N,N-dialkylalkylenediamine is N,N-dimethylpropane-1,3-diamine (also known as dimethylaminopropylamine (DMAPA)) or N,N-dibutylpropane-1,3-diamine (also known as dibutylaminopropylamine (DBAPA)).

[0068] According to the present application, the at least one alkylene oxide suitable for preparing the alkoxylated diamine of formula (I) is preferably ethylene oxide and / or propylene oxide.

[0069] According to the present application, the dicarboxylic acid is an aliphatic or cycloaliphatic dicarboxylic acid. Preferably, the dicarboxylic acid is a saturated or unsaturated aliphatic dicarboxylic acid having 2 to 8 carbon atoms. Suitable dicarboxylic acids include oxalic acid, succinic acid, adipic acid, sebacic acid, fumaric acid and maleic acid. The corresponding anhydrides are also suitable. According to a preferred embodiment, the dicarboxylic acid is adipic acid.

[0070] The subterranean treatment fluid of the present application is suitable for any subterranean formation treatment wherein shale inhibitors can be necessary.

[0071] The fluids disclosed herein can be used for drilling, completion and workover of oil and gas wells, as well as for stimulation jobs (such as fracturing), gravel packing, cementing, maintenance, reactivation, cuttings backflushing, etc.

[0072] Preferably, the subterranean treatment fluid is a drilling fluid or an aqueous hydraulic fracturing fluid.

[0073] When the subterranean treatment fluid of the present application is a drilling fluid, the subterranean treatment fluid comprises conventional additives well known to the person skilled in the art, such as viscosifying agents, dispersants, lubricants, fluid loss control agents, corrosion inhibitors, defoamers and surfactants.

[0074] The drilling fluid can further comprise an aqueous continuous phase and a weighting material, which can be selected from the group consisting of barite, hematite, ilmenite, iron oxide, calcium carbonate, magnesium carbonate, magnesium organic and inorganic salts, calcium chloride, calcium bromide, magnesium chloride, zinc halides, alkali metal halides, alkali metal formates, alkali metal nitrates and combinations thereof. Typically, the subterranean treatment fluid can comprise from 1 to 70 wt.% of the weighting material, depending on the desired density. The aqueous continuous phase can be selected from the group consisting of fresh water, seawater, brine, mixtures of water and water-soluble organic compounds and mixtures thereof.

[0075] When the subterranean treatment fluid of the present application is an aqueous hydraulic fracturing fluid, the fluid can be, for example, a gelled fluid, including linear or crosslinked gels, or a foamed gel, wherein the foam bubbles aid in the transport of proppant and placement of the proppant in the fracture. The aqueous hydraulic fracturing fluid can comprise an aqueous component, which can be selected from fresh water, salt water, seawater, natural or synthetic brines, mixtures of water and water-soluble organic compounds, any other aqueous liquid that will not interact with the other components of the aqueous hydraulic fracturing fluid to adversely affect its performance, and mixtures thereof.

[0076] The aqueous fracturing fluid generally comprises a viscosifying agent, a crosslinker system, and additives well known to those skilled in the art, such as proppant, gel stabilizer, gel breaker, surfactant, alcohol, scale inhibitor, corrosion inhibitor, fluid loss additive, buffer, bactericide, and the like.

[0077] Useful proppants include, but are not limited to, gravel, sand, resin-coated sand, ceramic beads, bauxite, glass, glass beads, and mixtures thereof.

[0078] Gel stabilizers are oxygen inhibitors or free radical scavengers that remove dissolved oxygen from the water. Dissolved oxygen is the primary cause of oxidative free radical polymer breakdown of water-soluble natural polymers or their derivatives used as viscosifying agents. Examples of suitable gel stabilizers are sodium thiosulfate, substituted benzofuranones, hydroxylamines in the form of their salts and alkyl derivatives, trivalent phosphorus compounds, hydroquinone and hydroquinone formulated with amines, natural antioxidants such as ascorbic acid and vitamin C, and methyl ethyl ketoxime. Useful gel breakers include, but are not limited to, ammonium persulfate, sodium persulfate, sodium bromate, and sodium chlorite, enzymes.

[0079] The present application will be further illustrated by the following examples. Example

[0080] Example 1 (comparative example)

[0081] Preparation of amino ester from adipic acid and triethanolamine (as described in prior art patent EP 2 061 856 B1)

[0082] In a 1 liter reaction vessel equipped with a stirrer, thermometer, and distillation head, 204.8 grams (1.37 moles) of triethanolamine were charged, heat was applied to 120°C, and 95.6 grams (0.65 moles) of adipic acid were added. Vacuum was applied to the reaction vessel to reach a residual pressure of about 20 mm Hg. Heat was applied to reach 175°C over about 1 hour. After 3 hours, 23 grams of water were distilled off, and the acid value was 3.5 mg KOH / g.

[0083] Example 2 (comparative example)

[0084] Preparation of polyester from oxalic acid with methyldiethanolamine

[0085] In a reaction vessel equipped with heating, stirring, temperature control, reagent introduction system (the reaction vessel is connected to a cooler with water collector), dimethylaminopropylamine (1945 g) was added. The reactor was pressurized and then vented three times to remove atmospheric oxygen. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120 °C. Then ethylene oxide (1555 g) was added while maintaining the temperature at 120-130 °C. After 30 minutes at the reaction temperature, the reaction mixture was cooled to 60 °C.

[0086] Example 3

[0087] i) Preparation of ethoxylated (2 moles) dimethylaminopropylamine

[0088] In a reaction vessel equipped with temperature measurement and control, pressure measurement, vacuum and inert gas purging, sampling and equipment for the introduction of ethylene oxide (as a liquid), dimethylaminopropylamine (1945 g) was added. The reactor was pressurized and then vented three times to remove atmospheric oxygen. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120 °C. Then ethylene oxide (1555 g) was added while maintaining the temperature at 120-130 °C. After 30 minutes at the reaction temperature, the reaction mixture was cooled to 60 °C.

[0089] ii) Preparation of a polyester from adipic acid and ethoxylated (2 moles) dimethylaminopropylamine

[0090] In a reaction vessel equipped with heating, stirring, temperature control, reagent introduction system (the reaction vessel is connected to a cooler with water collector), ethoxylated (2 moles) dimethylaminopropylamine (364.37 g), adipic acid (236.01 g) and zirconium acetylacetonate (0.30 g) were added. The reaction mixture was slowly heated to 165 °C under stirring and nitrogen flow. The reaction mixture was maintained at 165-175 °C until the acid value reached a value of about 47 mg KOH / g.

[0091] Example 4

[0092] i) Preparation of ethoxylated (5 moles) dimethylaminopropylamine

[0093] In a stirred stainless steel reactor equipped with temperature measurement and control, pressure measurement, vacuum and inert gas purging, sampling and means for introduction of ethylene oxide (as a liquid), dimethylaminopropylamine (1320 g) was added. The reactor was pressurized and then vented three times to remove atmospheric oxygen. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120 °C. Ethylene oxide was then added (first addition, 1112 g) while maintaining the temperature at 120-130 °C. After 30 minutes at reaction temperature, the reaction mixture was allowed to cool to 80 °C and sodium methoxide solution (30% in methanol) (10 g) was added. The reactor was pressurized and then vented three times to remove atmospheric oxygen. The reactor was kept under vacuum and nitrogen flow for 15 minutes to remove methanol. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120 °C. Ethylene oxide was then added (second addition, 1560 g) while maintaining the temperature at 120-130 °C. After 30 minutes at reaction temperature, the reaction mixture was allowed to cool to 80 °C and 80% acetic acid aqueous solution (5.0 g) was added.

[0094] ii) Preparation of a polyester from adipic acid and ethoxylated (5 moles) dimethylaminopropylamine

[0095] In a reaction vessel equipped with heating means, stirrer, thermometer, reagent introduction system (the reaction vessel was connected to a cooler with water collector), ethoxylated (5 moles) dimethylaminopropylamine (172 g), adipic acid (78 g) and zirconium acetylacetonate (0.125 g) were added. The reaction mixture was slowly heated to 155 °C under stirring and nitrogen flow. The reaction mixture was maintained at 155-165 °C until the acid value reached a value of about 66 mg KOH / g.

[0096] Example 5

[0097] i) Preparation of propoxylated (2 moles) dimethylaminopropylamine

[0098] In a stirred stainless steel reactor equipped with temperature measurement and control, pressure measurement, vacuum and inert gas purging, sampling and means for introduction of propylene oxide (as a liquid), dimethylaminopropylamine (2,060.6 g) was added. The reactor was pressurized and then vented three times to remove atmospheric oxygen. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120 °C. Propylene oxide was then added (2,343.1 g) while maintaining the temperature at 120-130 °C. After 120 minutes at reaction temperature, the reaction mixture was allowed to cool to 60 °C.

[0099] ii) Preparation of a polyester from adipic acid and propoxylated (2 moles) dimethylaminopropylamine

[0100] In a reaction vessel equipped with heating, stirring, temperature control, pressure measurement, vacuum and inert gas purging, sampling and means for introducing reagents, a mixture of dimethylaminopropylamine (100.0 g), adipic acid (40.0 g) and zirconium acetylacetonate (0.125 g) was introduced. The reaction mixture was slowly heated to 165°C under stirring and nitrogen flow. The reaction mixture was maintained at 165-175°C until the acid value reached a value of about 42 mg KOH / g.

[0101] Example 6

[0102] i) Preparation of propoxylated (5 moles) dimethylaminopropylamine

[0103] In a stirred stainless steel reactor equipped with temperature measurement and control, pressure measurement, vacuum and inert gas purging, sampling and means for introducing propylene oxide (as a liquid), propoxylated (2 moles) dimethylaminopropylamine (1400.7 g) and sodium methoxide solution (30% in methanol) (6.26 g) were introduced. The reactor was heated to 85°C, pressurized and then vented three times to remove atmospheric oxygen. The reactor was kept under vacuum and nitrogen flow for 15 minutes to remove methanol. The reactor was pressurized with nitrogen to 110-140 kPa and heated to 120°C. Then propylene oxide (1118.1 g) was added while maintaining the temperature at 120-130°C. After 30 minutes at the reaction temperature, the reaction mixture was allowed to cool to 60°C and 80% aqueous acetic acid (3.0 g) was added.

[0104] ii) Preparation of a polyester from adipic acid and propoxylated (5 moles) dimethylaminopropylamine

[0105] In a reaction vessel equipped with heating, stirring, temperature control, pressure measurement, vacuum and inert gas purging, sampling and means for introducing reagents, a mixture of dimethylaminopropylamine (100.0 g), adipic acid (40.0 g) and zirconium acetylacetonate (0.125 g) was introduced. The reaction mixture was slowly heated to 165°C under stirring and nitrogen flow. The reaction mixture was maintained at 165-175°C until the acid value reached a value of about 42 mg KOH / g.

[0106] Example 7

[0107] i) Preparation of ethoxylated (2 moles) dibutylaminopropylamine

[0108] In a stirred stainless steel reactor equipped with temperature measurement and control, pressure measurement, vacuum and inert gas purging, sampling and means for introduction of ethylene oxide (as a liquid), N,N-dibutylaminopropylamine (1,557.2 g) was added. The reactor was pressurized with nitrogen and then vented three times to remove atmospheric oxygen. The reactor was pressurized to 110-140 kPa with nitrogen and heated to 130 °C.

[0109] Ethylene oxide (755.0 g) was then added while maintaining the temperature at 130-140 °C. After 60 minutes at the reaction temperature, the reaction mixture was cooled to 60 °C.

[0110] ii) Preparation of the polyester from adipic acid and ethoxylated (2 moles) dibutylaminopropylamine

[0111] In a reaction vessel equipped with heating means, stirrer, thermometer, reagent introduction system (the reaction vessel was connected to a cooler with a water collector), ethoxylated (2 moles) dibutylaminopropylamine (1023.0 g), adipic acid (545.0 g) and zirconium acetylacetonate (0.8 g) were added. The reaction mixture was slowly heated to 190 °C under stirring and nitrogen flow. The reaction mixture was maintained at 190-195 °C until the acid value reached a value of about 45 mg KOH / g.

[0112] Performance evaluation

[0113] The shale inhibition performance was evaluated using the "Shale Particle Disintegration Test".

[0114] Before the test was performed, the shale was dried at 70 °C for 3 hours.

[0115] Then, the dried shale was ground and sieved through a 5 mesh (4 mm) sieve and a 10 mesh (2 mm) sieve.

[0116] Shale particles having a size smaller than 4 mm but larger than 2 mm were used in the test.

[0117] The shale particles used in the test had the following composition: 72% of illite / montmorillonite, 19% of illite, 8% of kaolinite, 2% of chlorite. The relative percentages refer to the amount of mineral present in the fraction having a particle size smaller than 2 pm.

[0118] Shale Particle Disintegration Test

[0119] The test was performed following the protocol described in section 22 of the standard method ISO 10416 with some modifications.

[0120] To 350 ml of synthetic seawater, 5 g of 40% shale inhibitor aqueous solution was added and the fluid was mixed for 15 minutes using a Hamilton Beach shaker. All samples were adjusted to pH 9.

[0121] To the fluid in the stainless steel aging cell, 100 g of size conditioned shale sample was added, which was then closed and shaken vigorously to disperse the shale particles. The cell was placed in a preheated oven and hot rolled at 70°C for 16 hours. When the 16 hour hot roll was complete, the sample was cooled to room temperature.

[0122] The contents of the sample cell were then poured onto two sieves: 10 mesh (2 mm) and 35 mesh (0.5 mm).

[0123] The residual shale in the cell was recovered by washing with a KCI solution (42.75 g / l).

[0124] The sieves were transferred to a bath containing tap water and immersed quickly but gently to rinse the sieves and shale.

[0125] The recovered shale was then placed into a pre-weighed pan and dried in an oven at 105°C to a constant weight.

[0126] After drying, the shale was cooled in the desiccator and weighed. The percent shale recovery for each mud was calculated using the following formula:

[0127] Recovery % = (weight of recovered shale in grams) / (100 - w h ) x 100

[0128] where w h is the initial moisture content in weight percent of the size conditioned shale. The initial moisture content of the shale was determined by weight loss at 105°C.

[0129] The results (percent recovery) are recorded in Table 1.

[0130] The higher the percent recovery, the better the performance of the shale inhibitor.

[0131] The results recorded in Table 1 show that the polyester of the present invention exhibits improved shale inhibition performance compared to the shale inhibitor of the prior art (Example 1).

[0132] Furthermore, the polyester of the present invention exhibits significantly better shale inhibition performance than ordinary shale inhibitors such as potassium chloride (KCI).

[0133] Table 1

[0134] % Recovery (10 mesh) % Recovery (35 mesh) % Total Recovery KCl 3.0 5.0 8.0 Example 1 6.2 12.1 18.4 Example 2 3.3 7.5 10.8 Example 3 4.1 25.9 30.0 Example 4 6.4 15.7 22.1 Example 5 9.8 16.2 26.0 Example 6 8.6 14.0 22.6 Example 7 8.6 11.6 20.2

[0135] * Comparative Example.

Claims

1. A method for inhibiting shale swelling and / or dispersion during treatment of a subterranean shale formation, the method comprising the steps of: a) providing a subterranean treatment fluid comprising 0.001 to 10 weight percent (wt%) of a polyester obtained by reacting a dicarboxylic acid having 2 to 8 carbon atoms with an alkoxylated diamine of formula (I): wherein: R1 and R2 are the same or different and are saturated or unsaturated aliphatic C1-C4 alkyl chains; n is an integer from 1 to 5; EO is CH2CH2O; PO is CH2CH(CH3)O; o, p, q and r are integers from 0 to 10, with the provisos that: i) the sum of o, p, q and r is at least 2, ii) o and p cannot simultaneously equal 0, iii) q and r cannot simultaneously equal 0; b) introducing the treatment fluid into a wellbore at a pressure sufficient to treat a subterranean shale formation. In formula (I), n is 3.

2. The method of claim 1, wherein, In formula (I), o, p, q and r are integers from 0 to 5.

3. The method of claim 2, wherein, In formula (I), R1 and R2 are both methyl or both butyl.

4. The method of claim 3, wherein, In formula (I), R1 and R2 are both methyl.

5. The method of claim 4, wherein, The polyester is obtained by reacting the dicarboxylic acid and the alkoxylated diamine of formula (I) in a molar ratio of 0.8:1 to 1:0.

8.

6. The method of claim 1, wherein, The polyester has an acid value of 10-150 mg OH / g.

7. The method of claim 1, wherein, The dicarboxylic acid is adipic acid.

8. The method of claim 1, wherein, The dicarboxylic acid is adipic acid.

9. The method of claim 4, wherein, The subterranean treatment fluid comprises 0.01 to 3 weight percent (wt%) of the polyester.

10. The method of claim 1, wherein, 11. A subterranean treatment fluid comprising an aqueous continuous phase and 0.001 to 10 weight percent (wt%) of a polyester obtained by reacting a dicarboxylic acid having 2 to 8 carbon atoms with an alkoxylated diamine of formula (I): wherein: R1 and R2 are the same or different and are saturated or unsaturated aliphatic C1-C4 alkyl chains; n is an integer from 1 to 5; EO is CH2CH2O; PO is CH2CH(CH3)O; o, p, q and r are integers from 0 to 10, with the provisos that: i) the sum of o, p, q and r is at least 2, ii) o and p cannot simultaneously equal 0, iii) q and r cannot simultaneously equal 0. In formula (I), n is 3. In formula (I), o, p, q and r are integers from 0 to 5.

12. The subterranean treatment fluid of claim 11, wherein, In formula (I), R1 and R2 are both methyl or both butyl.

13. The subterranean treatment fluid of claim 12, wherein, In formula (I), R1 and R2 are both methyl.

14. The subterranean treatment fluid of claim 13, wherein, The polyester is obtained by reacting the dicarboxylic acid and the alkoxylated diamine of formula (I) in a molar ratio of 0.8:1 to 1:0.

8.

15. The subterranean treatment fluid of claim 14, wherein, The polyester has an acid value of 10-150 mg OH / g.

16. The subterranean treatment fluid of claim 11, wherein, The dicarboxylic acid is adipic acid.

17. The subterranean treatment fluid of claim 11, wherein, The dicarboxylic acid is adipic acid.

18. The subterranean treatment fluid of claim 11, wherein, The subterranean treatment fluid comprises 0.01 to 3 weight percent (wt%) of the polyester.

19. The subterranean treatment fluid of claim 14, wherein, ​ 20. The subterranean treatment fluid of claim 11, wherein, ​

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