Polyamide composition for downhole tools

Abstract

The present invention relates to a polyamide composition for preparing a downhole tool element, a molded body comprising the same, a method of drilling a well using the molded body, and a method of performing a hydraulic fracturing process using the molded body, wherein the composition comprises or consists of: (M) from 40% to 100% by weight of a mixture (M) consisting of (A) from 10% to 89% by weight of a polyamide PA6, PA46, PA56, PA66, PA66 / 6, PA69, PA610 or a mixture thereof, (B) from 10% to 80% by weight of a water-soluble polyamide, (C) from 1% to 10% by weight of a metal hydroxide and a metal oxide of an alkaline earth element or a mixture thereof; and (D) 0% to 55% by weight of a filler and a reinforcing material other than (C) and (E); (E) 0% to 5% by weight of an additive other than (A) to (D).

Description

Technical Field

[0001] The present invention relates to a degradable polyamide composition in the oil and gas industry, more particularly to a degradable polyamide composition for manufacturing downhole tool components. In addition, the present invention relates to a water-degradable polyamide composition for downhole tool components comprising a water-soluble polyamide and an alkaline earth metal oxide or hydroxide, in particular a water-degradable polyamide composition for a hydraulic fracturing process. Background Art

[0002] Hydrocarbon resources such as crude oil or natural gas are extracted by drilling wells (oil wells or gas wells, collectively referred to as "wells") from land with porous and permeable underground formations. In continuously drilled wells, the production layer is stimulated to extract hydrocarbon resources from underground formations whose permeability decreases over time and gradually becomes insufficient. Well-known production stimulation methods include acid treatment methods and crushing methods. In acid treatment, the permeability of the production layer is increased by introducing a strong acid such as hydrochloric acid or hydrofluoric acid to dissolve the reactive components (carbonates, clay minerals, silicates, etc.) in the rock. However, various problems associated with the use of strong acids have been noted. Therefore, methods using fluid pressure to form fractures in the production layer, also known as "crushing" or "hydraulic fracturing", are being used more and more.

[0003] Hydraulic fracturing is a method of using fluid pressure, such as water pressure (hereinafter also referred to as "hydraulic pressure"), to create cracks in production layers. Vertical holes are usually drilled to a certain depth, and then the wells are bent and horizontal wells are created in the underground formations. Fracturing fluids are then injected into these wells under high pressure, resulting in fractures in the deep underground production layers due to the high hydraulic pressure, which improves the recoverability of hydrocarbons from the production layers. Hydraulic fracturing is also applicable to the development of unconventional resources such as shale oil (mature oil in shale) and shale gas.

[0004] Typically, well treatment in the form of hydraulic fracturing, i.e., the creation of fractures and perforations in a production layer of a deep underground formation containing a hydrocarbon resource such as petroleum, shale oil, natural gas or shale gas by hydraulic pressure using a high-pressure fluid (fracture fluid), is carried out as follows: a defined portion of the wellbore is completely or partially blocked by suitable well tool elements, gradually isolating it from the top of the wellbore. Then, fractures or perforations are created by injecting the fracture fluid into the production layer. Then, the next defined portion (usually before the previous portion, i.e., the portion closer to the surface of the ground) is blocked and another fracturing process is carried out, so that cracks and perforations continue to develop in the production formation. The process is repeated until the desired isolation, fracturing, etc. is achieved.

[0005] A borehole is drilled through a soil formation and downhole tools such as plugs and sleeves are positioned along and within the borehole. The plug closes and opens portions of the borehole, and isolating areas of the soil formation. The sleeve opens and closes to provide fluid communication between the borehole and the soil formation. The downhole tool isolates and connects areas for various operations to process and produce hydrocarbons from the soil formation. When work in an area is completed, it may be necessary to remove components of the downhole tool or even the entire downhole tool. For example, a soluble crushing ball that has been inserted into the opening of the downhole tool can be removed by selectively injecting a solvent into the area of ​​the soluble crushing ball so that its ball diameter is reduced or the ball is completely dissolved.

[0006] For example, as described in US2021 / 0254195A1, such a sphere can be made of an alloy based on magnesium and aluminum to which special elements such as Sn, Ga and In are added. These elements are able to break through the oxide layer formed in a humid environment, allowing oxidation in the metal alloy to continue to develop until the entire sphere is eventually dissolved.

[0007] EP3115544B1 discloses a degradable rubber element for a downhole tool, which contains 0.1 to 20 parts by mass of an acidic degradation accelerator, such as methyl p-toluenesulfonic acid.

[0008] WO2017 / 106077A1 discloses particulate phthalic acid or terephthalic acid as a temporary capping agent, the solubility of which is controlled by feeding an alkaline degradation accelerator into the wellbore fluid.

[0009] US2018 / 0252082A1 describes a method in which a polymer is contacted with a downhole fluid containing a Lewis acid at high temperature. In one example, polyamide 6 is fully degraded with zinc chloride or aluminum chloride in water at 150°C for 7 days.

[0010] US2018 / 0346800A1 describes a sealing element made of an aggregate of polylactic acid spheres and polylactic acid powder in a polyvinyl alcohol shell. After the shell is dissolved, the aggregate can be flushed with wellbore fluid.

[0011] US9856411B2 discloses a downhole tool made of polyhexahydrotriazine, which can be dissolved by hydrochloric acid. The polymer of 4,4'-oxydiphenylamine and formaldehyde is stable at a pH value greater than 3, but depolymerizes at a pH value less than 2.

[0012] US8231947B2 and US8567494B2 describe downhole tools, such as so-called "flow guide balls", made of materials having a water-soluble core and a water-insoluble shell, the core being accessible through an opening for the well fluid. Embodiments based on two different metals as well as embodiments with two different polymers are described.

[0013] US2010 / 0200235A1 discloses sealing balls made of carboxylic acids, fatty alcohols, fatty acid esters and / or fatty acid salts as drilling tool elements. These sealants are dissolved by increasing the temperature of the downhole fluid so that the balls soften and eventually melt when the melting point is exceeded. In this example, solid balls of sebacic acid are mentioned.

[0014] Oil and gas production can involve a wide range of conditions with very different temperatures, pressures, and fluid environments.

[0015] For temporary sealing of wells, there is a particular need for sealants that can keep a defined portion of the well sealed for a period of 2 to 10 days, after which they ideally dissolve without leaving any residue. Since conditions in oil and gas production can vary over a wide range in terms of temperature, pressure and fluid environment, different drilling tool closures (e.g., breaking balls) are required to achieve a defined sealing time.

[0016] In particular, at temperatures below 120° C., many known materials used to manufacture downhole tool closures do not degrade fast enough, making the processing time of the corresponding drilling section inefficiently long. On the other hand, some downhole tool closures require the use of special downhole fluids, some of which are aggressive and environmentally harmful, or the addition of such additives to the downhole fluids in order to dissolve the corresponding closure material. Ideally, however, it should be possible to dissolve the downhole tool closures by using water, groundwater or seawater. Summary of the invention

[0017] The object of the present invention is therefore to provide a degradable polyamide composition for producing downhole tool elements which can be degraded by water sufficiently quickly, in particular at temperatures below 120° C., preferably up to a maximum of 100° C. In particular, it is preferred if the polyamide composition is degradable within 2 to 10 days in an aqueous medium at a pH value in the range from 4 to 8 and a maximum temperature of 120° C., preferably up to 100° C. In this context, "degradable" means that the polyamide composition can be completely dissolved in an aqueous medium, or that the breaking strength of the polyamide composition is reduced to such an extent that a molding disintegrates from the polyamide composition under pressure or mechanical influence. The latter is achieved when the breaking strength is reduced to less than 30%, preferably less than 20%, of the initial value before storage.

[0018] Another object of the present invention is to provide downhole tool elements based on degradable polyamide compositions. Said object is to be able to release the structural integrity of these elements, especially sealing elements (such as plug balls, flow guides, sealant balls) within 2 to 10 days with the aid of water and temperatures up to 120°C, which is the point at which temporary sealing can be reopened.

[0019] The object is therefore also to provide a method in which an opening in a drilling line system can be temporarily sealed by a component of a drilling tool, in particular the sealing component made of the polyamide composition according to the invention is degraded within the drilling line.

[0020] When referring to "degradable" in the context of the present invention, the term is considered to be very broad. For example, the term may include a chemical reaction of a polymer in an aqueous solution whereby the polymer depolymerizes and thus degrades. However, degradable primarily refers to disintegration, melting, external softening or reduction in diameter.

[0021] Definition of terms

[0022] For the purposes of the present invention, the term "polyamide" (abbreviation PA) is understood as a generic term including homopolyamides and copolyamides. The spellings and abbreviations selected for polyamides and their monomers correspond to those specified in ISO standard 16396-1 (2015). The abbreviations used therein are used synonymously with the IUPAC names of the monomers hereinafter.

[0023] For the purposes of the present invention, water-soluble polyamides are those polyamides which have only carbon atoms and nitrogen atoms in the polymer backbone and which optionally carry functional groups bonded to the backbone which promote sufficient water solubility. In the context of the present invention, sufficient water solubility is present when at least 50% by weight, preferably at least 70% by weight, of the polyamide is soluble in distilled water at 80° C. (weight ratio of polyamide to water is 1 to 100) within 24 hours. Specifically, determining whether a polyamide is a water-soluble polyamide (B) is carried out as follows: In a sealed glass container, 1 g of polyamide particles (diameter: 2 mm to 3 mm, length: 3 mm to 5 mm) having a water content of less than 0.5% is stirred in 100 g of deionized or distilled water at 80° C. for 24 hours. This is then filtered through a filter element (e.g. filter paper, filter cloth, glass frit). The filtrate obtained is dried in a vacuum (30 mbar, 80° C., 72 hours) and the mass of dissolved polyamide is determined. A polyamide is defined as a water-soluble polyamide if at least 50% by weight, preferably at least 70% by weight, of the polyamide in question is dissolved, ie present in the filtrate.

[0024] Polyamide composition

[0025] This object is achieved with a molding composition having the features of claim 1, with a molding having the features of claim 9 and with a method having the features of claim 12. The dependent claims indicate advantageous further embodiments.

[0026] According to the invention, this object is achieved on the one hand by a polyamide composition according to claim 1, wherein the polyamide composition comprises the following components or consists of the following components:

[0027] 40 to 100 wt. % of a mixture (M) consisting of:

[0028] 10 to 89% by weight of polyamide PA6, PA46, PA56, PA66, PA66 / 6, PA69, PA610 or mixtures thereof;

[0029] 10 to 80 wt. % of a water-soluble polyamide;

[0030] 1 to 10 wt % of metal hydroxides and metal oxides of alkaline earth elements or mixtures thereof;

[0031] and

[0032] 0 to 55 wt% of fillers and reinforcing materials other than (C) and (E);

[0033] 0 to 5% by weight of additives other than (A) to (D);

[0034] Components (A) to (C) thus add up to 100% by weight of the mixture (M), and the sum of components (M), (D) and (E) thus adds up to 100% by weight.

[0035] Preferably, the polyamide composition according to the invention comprises component (M) as a mixture of component (A), component (B) and component (C) in an amount in the range of 47% to 90% by weight, component (D) in an amount in the range of 10% to 50% by weight, and component (E) in an amount in the range of 0% to 3% by weight, in each case based on the sum of component (M), component (D) and component (E).

[0036] Preferably, the mixture (M) comprises 30% to 69% by weight of component (A), 30% to 64% by weight of component (B) and 1% to 6% by weight of component (C).

[0037] Preferably, the water-soluble polyamide (B) is an N-alkoxymethylated polyamide.

[0038] Preferably, the polyamide composition consists only of the blend (M) plus optional fillers and reinforcing agents (D) and additives (E).

[0039] The metal hydroxides and metal oxides of component (C) are different from the fillers and reinforcing materials (D) and additives (E).

[0040] Component (A)

[0041] According to the present invention, component (A) comprises polyamide PA6, PA46, PA56, PA66, PA66 / 6, PA69, PA610 and mixtures thereof. In the blend (M), the content of component (A) is 10 to 89% by weight, preferably 30 to 69% by weight.

[0042] Within the meaning of the present invention, polyamide (A) is insoluble in water.

[0043] The solution viscosity RV of the polyamide (A), measured in accordance with ISO 307 (2007) on a solution of 0.5 g of polymer in 100 ml of m-cresol at 20° C., is preferably in the range of 1.3 to 3.0, particularly preferably in the range of 1.5 to 2.7 and especially preferably in the range of 1.6 to 2.5.

[0044] Component (B) - Water-soluble polyamide

[0045] A key property of the polyamide (B) is its water solubility. As defined above, the polyamide (B) must have sufficient water solubility. In the context of the present invention, sufficient water solubility exists when at least 50% by weight, preferably at least 70% by weight of the polyamide is soluble in distilled water at 80° C. (weight ratio of polyamide to water is 1 to 100) within 24 hours.

[0046] In the case of water-soluble polyamides, N-alkoxymethylated polyamides are particularly preferred. Thus, it is further preferred if 20 mol % to 60 mol % of the nitrogen atoms in the N-alkoxymethylated polyamide are alkoxymethylated. N-alkoxymethylated polyamides can be obtained by polymer-analogous reaction of polyamides with formaldehyde, paraformaldehyde and alcohols, in particular methanol.

[0047] Optionally, the hydrophilicity of component (B) can be further enhanced if the N-alkoxymethylated polyamide is grafted with a hydrophilic vinyl monomer. For this purpose, the following vinyl monomers are preferred: hydroxyethyl acrylate, hydroxyethyl methacrylate, ethylene glycol monomethacrylate, acrylic acid, methacrylic acid, itaconic acid, acrylamide, N-hydroxymethyl acrylamide.

[0048] It is particularly preferred that the water-soluble polyamide (A) is selected from N-methoxymethylated polyamide 6, N-methoxymethylated polyamide 66, N-methoxymethylated polyamide 610, N-ethoxymethylated polyamide 6, N-ethoxymethylated polyamide 66, N-ethoxymethylated polyamide 610, N-butoxymethylated polyamide 6, N-butoxymethylated polyamide 66, and N-butoxymethylated polyamide 610. In particular, N-methoxymethylated polyamide 66 is preferred.

[0049] The solution viscosity RV of the polyamide (B), measured in accordance with ISO 307 (2007) on a solution of 0.5 g of polymer in 100 ml of m-cresol at 20° C., is preferably in the range of 1.3 to 2.7, particularly preferably in the range of 1.4 to 2.3 and especially preferably in the range of 1.5 to 2.0.

[0050] Component (C)

[0051] Component (C) is an alkaline earth metal oxide or alkaline earth metal hydroxide or a mixture thereof. Preferably, the alkaline earth metal oxide or alkaline earth metal hydroxide is selected from magnesium hydroxide, calcium hydroxide, calcium oxide, magnesium oxide or a mixture thereof. Magnesium oxide and calcium oxide are particularly preferred, and calcium oxide is particularly preferred.

[0052] The content of component (C) in the mixture (M) is 1% to 10% by weight, preferably 1% to 6% by weight, and particularly preferably 2% to 5% by weight.

[0053] Component (C) is particularly different from component (D) and component (E).

[0054] Component (D)

[0055] The molding mixture may also contain particulate fillers and / or reinforcing fibers in an amount of 0 to 55% by weight, in particular in an amount of 10 to 50% by weight, based on the sum of component (M), component (D) and component (E).

[0056] Component (D) can be water-soluble or water-insoluble. For the purposes of the present invention, component (D) is water-soluble if more than 50% by weight, preferably more than 70% by weight, of (D) dissolves in distilled water at 80° C. within 24 hours. In this case, the weight ratio of (D) to distilled water is 1:100. In the context of the present invention, (D) is referred to as water-insoluble if less than 50% by weight dissolves.

[0057] Examples of suitable particulate fillers (B) are calcium carbonate, talc, mica, silicates, quartz, titanium dioxide, wollastonite, kaolin, amorphous silica, magnesium carbonate, chalk, lime, feldspar, barium sulfate, ground glass fibers, glass flakes or glass beads.

[0058] The example of suitable reinforcing fiber includes glass fiber, especially E-glass fiber; carbon fiber; metal fiber; potassium titanate whisker; aramid fiber; or plastic fiber, such as polyamide fiber. Preferably, the reinforcing fiber has a circular cross section and a diameter in the range of 5 microns to 20 microns, particularly 6 microns to 13 microns. Preferably, glass fiber is used as reinforcing fiber. Preferably, glass fiber is incorporated into the polyamide composition in the form of short glass fiber (i.e., short chopped glass fiber with a length of 2mm to 12mm, preferably 3mm to 5mm).

[0059] Preferably, the polyamide composition according to the invention comprises as component (B) fillers and / or reinforcing materials selected from the group consisting of calcium carbonate, talc, mica, silicates, quartz, titanium dioxide, wollastonite, kaolin, amorphous silica, magnesium carbonate, chalk, lime, feldspar, barium sulfate, ground glass fibers, glass flakes, glass beads, glass fibers, carbon fibers, metal fibers, potassium titanate whiskers, aramid fibers or plastic fibers. For the purposes of the present invention, the plastic fibers may be water-soluble.

[0060] Component (E) - Additives

[0061] Furthermore, the polyamide composition may comprise up to 5% by weight of additives as component (E), based on the sum of component (M), component (D) and component (E). According to a preferred embodiment, the molding composition according to the invention comprises, as component (E), 0% to 3% by weight, particularly preferably 0.1% to 3% by weight, of at least one additive, based on the sum of component (M), component (D) and component (E).

[0062] According to a preferred embodiment, the additives of component (E) are selected from stabilizers; antioxidants; antiozonants; processing stabilizers; processing aids; viscosity regulators; light stabilizers; UV stabilizers; UV absorbers; inorganic heat stabilizers, in particular inorganic heat stabilizers based on copper halides and alkali metal halides; organic heat stabilizers; optical brighteners; crystallization promoters; crystallization retarders; flow aids; lubricants; slip agents; release agents; colorants, in particular dyes, inorganic pigments, organic pigments; marking agents; and mixtures thereof.

[0063] According to a further preferred embodiment, the molding composition according to the invention comprises as component (E) at least one heat stabilizer, which is preferably present in a proportion of 0.1 to 3% by weight, based on the sum of component (M), component (D) and component (E).

[0064] Furthermore, the invention comprises a molded body of the polyamide composition or a molded body comprising at least one region or coating of the polyamide composition, preferably produced by injection molding, extrusion or pressing. Preferably, the molded body is a component of a drilling tool comprising or consisting of the polyamide composition.

[0065] Preferably, the downhole tool element is a plug, a ball, a valve, a downhole plug, an insertion aid, a connection and a coupling, or a guiding aid (centralizing aid).

[0066] The invention also relates to a method for drilling a well, said method comprising using said element for a well tool.

[0067] Preferred is a method for performing a hydraulic fracturing process, wherein said method comprises using said element for a downhole tool.

[0068] Further preferred is a method for drilling a well, the method comprising sealing a wellbore or a perforation using a downhole tool element in a drilling tool, whereafter the element comprising the polyamide composition is degraded within the wellbore.

[0069] Particularly preferred is a method of performing a hydraulic fracturing process comprising sealing a wellbore or a perforation in a well tool using a downhole tool element, whereafter the element comprising or consisting of the polyamide composition is degraded within the wellbore. DETAILED DESCRIPTION

[0070] The present invention is explained in more detail below with reference to the following examples.

[0071] Relative viscosity

[0072] The relative viscosity (RV) is determined according to ISO 307 (2007) at 20° C. For this purpose, 0.5 g of polymer particles are weighed into 100 ml of m-cresol and the relative viscosity (RV) is calculated according to RV=t / t0 following section 11 of the standard.

[0073] Glass transition temperature (Tg) and melting point (Tm)

[0074] According to ISO 11357-2 and ISO 11357-3 (2013), the particles were subjected to the determination of glass transition temperature and melting point. For each of the three heatings, differential scanning calorimetry (DSC) was performed at a heating rate of 20K / min. After the first heating, the sample was cooled at a rate of 20K / min, and the melting point was determined during the subsequent heating (second heating). The sample was then quenched in dry ice, and the glass transition temperature (Tg) was determined during the third heating. The temperature at the peak maximum was considered as the melting point. The midpoint of the glass transition region given as the glass transition temperature (Tg) was determined by the "half-height" method.

[0075] Storage test

[0076] According to DIN EN ISO 3167:2014-11, 5 test specimens of type B (B1) with dimensions of 80 mm×10 mm×4 mm were stored in a solution of 200 g of distilled water and 1.8 g of sodium chloride at 93.3° C. for 10 days. The test specimens were then tested for their glass transition temperature. After storage, the condition of the test specimens was checked. If the test specimens completely dissolved or disintegrated into several individual parts, they received a rating of "D", otherwise "ND".

[0077] Preparation of polyamide molding compounds

[0078] For Examples E1 to E6 according to the invention and Comparative Examples CE1 to CE3, the respective amounts of component (A), component (B), component (C) and component (E) were metered into the feed zone of a twin-screw extruder of the Werner & Pfleiderer ZSK 25 type according to Table 2, and if necessary, glass fibers (D) were introduced into the melt before discharge through a side feeder 6 barrel zone. The temperature of the first shell was set to 70° C. and the temperatures of the remaining shells were set to 260° C. to 290° C. A speed of 250 rpm and a throughput of 7 kg / hour were used, and atmospheric degassing was applied. The wire was cooled on a cooling belt (air cooling), cut, and the pellets obtained were dried at 100° C. under vacuum (30 mbar) for 24 hours to a moisture content of less than 0.1% by weight.

[0079] Production of test specimens

[0080] The test specimens were produced on an injection molding machine of the type Allrounder 420C 1000-250 from Arburg. A cylinder temperature of 260° C. to 280° C. and a molding temperature of 80° C. were used. Unless otherwise stated, the test specimens were used under dry conditions; for this purpose, they were stored at room temperature in a dry environment (ie above silica gel) for at least 48 hours after injection molding.

[0081] Table 1: Materials used in Examples and Comparative Examples

[0082]

[0083] Table 2: Example (E) and Comparative Example (CE); the composition is given below in weight percentage (wt%)

[0084]

Claims

1. A polyamide composition for preparing a downhole tool element, comprising or consisting of: (M) 40% to 100% by weight of a mixture (M) consisting of: (A) 10 to 89% by weight of polyamide PA6, PA46, PA56, PA66, PA66 / 6, PA69, PA610 or mixtures thereof; (B) 10 to 80 wt % of a water-soluble polyamide; (C) 1 to 10 wt % of a metal hydroxide or metal oxide of an alkaline earth element or a mixture thereof; and (D) 0 to 55 wt% of fillers and reinforcing materials other than (C) and (E); (E) 0 to 5 wt% of additives other than (A) to (D); Components (A) to (C) total 100% by weight of the mixture (M), and component (M), component (D) and component (E) total 100% by weight. 2 . The polyamide composition according to claim 1 , wherein the water-soluble polyamide (A) is an N-alkoxymethylated polyamide. 3 . The polyamide composition according to claim 2 , wherein 20 mol % to 60 mol % of nitrogen atoms in the N-alkoxymethylated polyamide are alkoxymethylated.

4. The polyamide composition according to claim 1, wherein the water-soluble polyamide (A) is selected from N-methoxymethylated polyamide 6, N-methoxymethylated polyamide 66, N-methoxymethylated polyamide 610, N-ethoxymethylated polyamide 6, N-ethoxymethylated polyamide 66, N-ethoxymethylated polyamide 610, N-butoxymethylated polyamide 6, N-butoxymethylated polyamide 66, N-butoxymethylated polyamide 610, or a mixture thereof.

5. The polyamide composition according to claim 1, wherein the metal hydroxide and metal oxide (C) are magnesium hydroxide, calcium hydroxide, calcium oxide, magnesium oxide or a mixture thereof. The polyamide composition according to claim 1 , wherein the component (C) is calcium oxide.

7. The polyamide composition according to claim 1, wherein the filler and / or reinforcing agent (D) is selected from calcium carbonate, magnesium hydroxide, calcium hydroxide, calcium oxide, magnesium oxide, talc, mica, silicates, quartz, titanium dioxide, wollastonite, kaolin, amorphous silica, magnesium carbonate, chalk, lime, feldspar, barium sulfate, ground glass fibers, glass flakes, glass beads, glass fibers, carbon fibers, metal fibers, potassium titanate whiskers, aramid fibers or plastic fibers.

8. The polyamide composition according to claim 1, wherein the component (E) is selected from stabilizers; anti-aging agents; antioxidants; antiozonants; processing stabilizers; processing aids; viscosity modifiers; light stabilizers; UV stabilizers; UV absorbers; inorganic heat stabilizers, especially inorganic heat stabilizers based on copper halides and alkali metal halides; organic heat stabilizers; optical brighteners; crystallization promoters; crystallization retarders; flow aids; lubricants; slip agents; release agents; colorants, especially dyes, inorganic pigments, organic pigments; marking agents; and mixtures thereof.

9. A molded body comprising or consisting of the degradable polyamide composition according to any one of claims 1 to 8.

10. The molded body according to claim 9, wherein the molded body is a downhole tool element.

11. A downhole tool element according to claim 10, wherein the element is a plug, a ball, a valve, a downhole plug, an insertion aid, a connector and a coupling, or a guide aid (centralising aid).

12. A method of drilling a well, the method comprising using a downhole tool element according to any one of claims 10 and 11.

13. A method of performing a hydraulic fracturing process, the method comprising using a downhole tool element according to any one of claims 10 and 11.

14. A method of drilling a well according to claim 12, comprising sealing a wellbore or perforation using a downhole tool element in a drilling tool, whereafter the element comprising a polyamide composition degrades within the wellbore.

15. The hydraulic fracturing process of claim 13, wherein the process comprises sealing a wellbore or perforation in a well tool using a downhole tool element, thereafter the element comprising a polyamide composition degrades within the wellbore.

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