Environmentally Friendly Epoxy Compositions

FIELD OF THE INVENTION

The present invention relates to compositions and methods for treating a region of a subterranean formation. In particular, though not exclusively, the present invention relates to epoxy compositions which are environmentally friendly and which exhibit suitable curing properties for treating a region of a subterranean formation.

BACKGROUND TO THE INVENTION

Chemical compositions are used extensively in a number of applications relating to the treatment of subterranean formations.

For example, it is known to use chemical compositions to plug or at least partially plug a high-permeability region of a subterranean formation for subsequent enhanced oil recovery by water, gas, or chemical flooding. This process is known as conformance control.

It is also known to inject chemical compositions into a region of a formation in order to consolidate the formation, for example to reduce production of sand from the formation during production. This process is known as sand control.

It is also known to inject chemical compositions into a region of a formation in order to consolidate proppants in formation fractures. Hydraulic fracturing, also known as fracking, is a known process which allows creation of fractures from a wellbore into a formation or reservoir. This technique consists of pumping hydraulic fluid into a wellbore at a pressure and injection rate such that fractures are created within the formation. These fractures act as channels which facilitate and increase production of hydrocarbons, e.g. oil, from the formation into the wellbore. In order to prevent closure or collapse of these fractures under reservoir conditions when the hydraulic fracture pressure is released, it is known to inject solid particles known as proppants into the created fractures, either during, or after, fracturing. In order to prevent the proppant particles being produced back into the wellbore during subsequent production of the formation, chemical compositions may be injected into the formation fractures in order to consolidate the proppant particles in the fractures. This process is known as proppant consolidation.

It is also known to inject chemical compositions into a region of a formation for a variety of applications, including, for example, cementing of downhole equipment, e.g., casings or liners, well abandonment, etc. For example, when downhole equipment such as a casing, is in need of repair, conventional methods to repair such a casing, for example to minimise of prevent casing leaks, involve either the use of cement or of mechanical patches. However, these methods have encountered limited success when treating small casing leaks, such as "pinhole" or thread leaks. In particular, cement compositions do not tend to penetrate through small leaks easily. Even if cement is able to plug a small hole in a casing, the cement plug may be easily dislodged due to mechanical forces such as shocks or vibrations. Gel treatments can also be used to repair small casing leaks more effectively. Gel compositions can flow easily through the small casing holes and may travel some distance into the formation near the leak. Thus, gel treatments are generally directed at stopping flow in the porous rock around the vicinity of the casing leak, rather than solely attempting to permanently plug the casing leak itself. If the resulting gel is able to withstand the near wellbore pressure conditions, a small amount of gel material may be sufficient to repair the leak. However, greater volumes may be required if flow behind pipe or fractures exist in the vicinity of the casing leak.

Many chemical compositions used during treatment of a subterranean formation may be considered as environmentally unfriendly and/or environmentally harmful. For example, chemicals applied offshore in the North-East Atlantic region are subject to the 'OSPAR' convention for the protection of the marine environment. Under this convention, a colour classification of chemicals is used to indicate their environmental impact, as shown in Table 1 , based on criteria and properties including biodegradation, bioaccumulation and acute toxicity. In order to obtain approval of chemicals for use offshore, OSPAR requirements must be met. A yellow or green classification is desirable for treatment compositions as this indicates that the chemical composition in questions has a relatively low environmental impact.

Table 1

A common family of chemicals used for injections in a subterranean formation is epoxy resins. Most commercially available epoxy systems are based on resin sealants containing the chemical compound Biphenol A. Biphenol A and Biphenol A diglycyl ether are, however, environmentally unfriendly and therefore undesirable. Furthermore, many of the crosslinkers and/or crosslinking systems used to cure or harden conventional epoxy resins are also environmentally unfriendly.

It is amongst the objects of the present invention to obviate and/or mitigate at least one of the aforementioned disadvantages.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a curable composition for treating a region of a formation, the composition comprising:

an epoxy resin; and

a crosslinking or hardening system;

wherein the composition is environmentally friendly, is capable of curing in the region of the formation in situ, and does not flash set.

The terms "hardener" and "crosslinker" will be herein understood as referring to compounds that induce curing of the epoxy resin. Hardeners/crosslinkers are sometimes also referred to as curatives, and may typically react with the epoxy to achieve curing thereof. Thus, the terms "hardener" and "crosslinker", and "hardening" and "crosslinking" will be herein understood as being synonymous and may be used interchangeably.

The composition may be capable of curing in about 1 -15 hours, e.g., in about 1 -

10 hours, e.g., in about 3-8 hours at about 30°C-90°C. The composition may be capable of curing in about 1 -15 hours, e.g., in about 1 -10 hours, e.g., in about 3-8 hours, at about 30°C-50°C and/or at about 50°C-70°C and/or at about 70°C-90°C. The composition may be capable of curing in about 1-15 hours, e.g., in about 1 -10 hours, e.g., in about 3-8 hours at about 30°C.

Advantageously, the curing times of the composition of the present invention may be well suited for injection in a region of a formation. Without wishing to be bound by theory, it is thought that if a composition exhibits an excessively short curing time under the conditions in the formation, e.g. at about 30°C-90°C, premature hardening may occur, leading to hardening of the epoxy composition before it reaches its intended location, thus failing to achieve its intended use and/or potentially causing damage and/or blockage to downhole equipment such as coil tubing. On the other hand, if a composition exhibits an excessively long curing time under the conditions in the formation, e.g. at about 30°C-90°C, delayed hardening may occur, which may also be undesirable for several reasons. Firstly, if the well or formation do not remain entirely still during curing, the epoxy material may flow into areas of the well or formation that were not intended to be treated. Secondly, if the curing process requires a lengthy period of time, the integrity of the cured material, e.g. epoxy plug, may be compromised, for example if formation fluid trickles into or passes through of by the material, potentially causing flow channels through the material.

The composition may have a viscosity which permits injection of the composition at/to the region of the formation. The viscosity may be sufficiently low to permit the composition to flow to the region of the formation. The viscosity may be sufficiently high to maintain integrity of the composition during curing at the region of the formation.

Typically the viscosity of the composition (for example a curable composition according to this invention), e.g., at the time of injection, e.g. at surface, may be at least about 1 cP, e.g. at least about 100 cP, e.g. at least about 500 cP. The viscosity of the composition e.g., at the time of injection, e.g. at surface, may be in the range of about 1 cP to about 2,000 cP, e.g. about 500 cP to about 1 ,500 cP, e.g. about 750 cP to about 1 ,250 cP. The viscosity of the composition e.g., at the time of injection, e.g. at surface, may be about 1 ,000 cP. The viscosity at the time of injection, e.g. at surface, may relate to the viscosity of the composition upon or shortly after mixing, e.g. prior to hardening or shortly after hardening has started. Typically the viscosity of the composition, e.g., at the location where the composition is intended to be injected, e.g., at the region of the formation, may be at least about 1 ,000 cP, e.g. at least about 2,000 cP, e.g. at least about 3,000 cP. The viscosity of the composition e.g., at the location where the composition is intended to be injected, e.g., at the region of the formation, may be in the range of about 1 ,000 cP to about 100,000 cP, e.g. about 3,000 cP to about 10,000 cP.

A person of skill in the art will understand that, due to the curing process beginning when the components of the composition are mixed together, the viscosity of the composition may not remain constant over time, e.g. from the time of mixing and/or injection, to the moment when the composition reaches a desired location, e.g. the region of the formation. Thus, the composition may advantageously have a sufficiently low viscosity to allow injection, e.g. pumping, of the composition, e.g. to the region of the formation. The composition may also advantageously have a sufficiently high viscosity to provide a hardening and/or hardened material having adequate structural integrity in situ, e.g. at the region of the formation. The inventors have discovered that the composition of the present invention possesses a viscosity which permits injection, e.g. pumping, of the composition downhole, e.g., to the region of the formation, and/or effective hardening of the composition in situ, e.g. at the region of the formation. Additionally (and as described above), the composition is environmentally friendly, is capable of curing in the region of the formation in situ, (and under the particular conditions of the formation (temperature, pressure, movement and the like)) and does not flash set.

The viscosity of the composition may be adjusted with one or more additives, e.g., a solvent, a diluent, a viscosifier, a thickener, or the like. The composition may comprise one or more additives capable of altering, modifying and/or adjusting the viscosity of the composition, e.g., a solvent, a diluent, a viscosifier, a thickener, or the like. Advantageously, the composition may not flash set at about 30°C-90°C, e.g. at about 30°C-50°C and/or at about 50°C-70°C and/or at about 70°C-90°C. The composition may not flash set at about 50°C.

Advantageously, the composition may not cause excessive exothermic reactions upon curing.

The epoxy resin may be selected from the group consisting of: 1 ,6-Hexanediol diglycidyl ether (HDDGE), 1 ,4-Butanediol diglycidyl ether (BDDGE), Neopentyl glycol diglycidyl ether (NPGDGE), or 1 ,4-Cyclohexanedimethanol diglycidyl ether (CHDMDGE).

The epoxy resin may comprise, may consist essentially of or may consist of 1 ,6-

Hexanediol diglycidyl ether (HDDGE). The inventors have discovered that HDDGE may represent an epoxy resin having suitable environmental properties, while exhibiting advantageous curing properties for use in subterranean applications as well as excellent mechanical properties such as strength.

The crosslinking/hardening system may comprise a first crosslinker/hardener.

The first crosslinker may comprise, may consist essentially of or may consist of a diamine or a polyamine compound. The first crosslinker may comprise, may consist essentially of or may consist of a polyetheramine compound. The first crosslinker may comprise, may consist essentially of or may consist of a polyetherdiamine compound. The first crosslinker may comprise, may consist essentially of or may consist of a polyoxypropylenediamine compound. The first crosslinker may comprise, may consist essentially of or may consist of a polyetherdiamine compound of formula (I).

H ₂ N-[CH(CH ₃ )CH ₂ 0] _X CH ₂ CH(CH ₃ )-NH ₂ (I)

where x = 2-10, e.g. 3-9, e.g. 4-8, typically 5-7. The first crosslinker may comprise, may consist essentially of or may consist of a Jeffamine® crosslinker. The first crosslinker may comprise, may consist essentially of or may consist of a Jeffamine® D-400 crosslinker. The use of a Jeffamine® crosslinker, e.g., Jeffamine® D-400, as the first crosslinker provides sufficiently long curing time to allow injection and/or delivery of the composition to a desired region of a subterranean formation, as well as being categorized as yellow under the OSPAR classification. This crosslinker also has the advantage of providing swellability in seawater.

Jeffamine® D400 may be represented by formula (II):

H ₂ N-[CH(CH ₃ )CH ₂ 0] _X CH ₂ CH(CH ₃ )-NH ₂ (II)

where x =6.1 .

Jeffamine® D400 may be named Polypropylene glycol bis(2-aminopropyl ether).

The crosslinking/hardening system may comprise a second crosslinker/hardener. The second crosslinker may comprise or may be a crosslinker having faster curing characteristics or properties than the first crosslinker.

The second crosslinker may comprise an alkyldiamine, e.g. hexamethylene diamine (HMDA) and/or 2-Methyl 1 ,5-pentanediamine (also referred to as 2- methylpentamethylenediamine, marketed under the name Dytek® Amine A).

The composition, e.g. the crosslinking/hardening system, may comprise at least one crosslinking/hardening accelerator. The at least one crosslinking accelerator may comprise trietanolamine (TEA), pyridine, 3-aminopropyldimethylamine, N,N- Dimethylaniline (DMA) and/or Ν,Ν-dimethylbutylamine. Advantageously, the at least one crosslinking accelerator may comprise or may be trietanolamine (TEA).

Advantageously, the first crosslinker, second crosslinker and/or crosslinking accelerator may provide for an environmentally friendly crosslinking system, e.g. may allow the crosslinking system to satisfy OSPAR requirements. The crosslinking system may contain about 60%-100%, e.g. about 75-100%, typically about 90-100%, of the first crosslinker.

The crosslinking system may contain about 0-40%, e.g. about 0-25%, typically about 0-10%, of the second crosslinker and/or of the crosslinking accelerator.

The composition may comprise about 25-75 wt %, e.g., about 30-70 wt%, e.g. about 40-60 wt%, e.g. about 45-50 wt % of the epoxy resin.

The composition may comprise about 25-75 wt %, e.g., about 30-70 wt%, e.g. about 40-60 wt%, e.g. about 50-55 wt % of the crosslinking system.

The composition may comprise about 25-75 wt %, e.g., about 30-70 wt%, e.g. about 40-60 wt%, e.g. about 45-55 wt % of the first crosslinker.

The composition may comprise about 0-5 wt %, e.g., about 0-2 wt%, e.g. about 0-1 wt% of the second crosslinker or crosslinking accelerator. Typically, when the composition comprises a crosslinking accelerator, e.g. TEA, the composition may comprise about 0.001 -0.5 wt %, e.g., about 0.01 -0.1 wt% of the crosslinking accelerator.

The crosslinking system may be selected from the group consisting of:

A polyetherdiamine compound, e.g. Jeffamine® D400;

A polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% 2- methylpentamethylenediamine;

A polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% hexamethylene diamine (HMDA); and/or

A polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% triethanolamine (TEA).

The crosslinking system may be selected from the group consisting of:

A polyetherdiamine compound, e.g. Jeffamine® D400;

A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% 2- methylpentamethylenediamine; A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% hexamethylene diamine (HMDA) ; and/or

A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% triethanolamine (TEA).

Thus, in a second aspect of the invention, there is provided a curable composition for treating a region of a formation, the composition comprising:

an epoxy resin comprising, consisting essentially of or consisting of 1 ,6- Hexanediol diglycidyl ether (HDDGE); and

a crosslinking system comprising, consisting essentially of or consisting of

Jeffamine® D400; Jeffamine® D400 with up to 10% 2-methylpentamethylenediamine; Jeffamine® D400 with up to 10% hexamethylene diamine (HMDA) and/or Jeffamine® D400 with up to 10% triethanolamine (TEA).

The crosslinking system may be selected from the group consisting of:

- A polyetherdiamine compound, e.g. Jeffamine® D400;

A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% 2- methylpentamethylenediamine;

A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% hexamethylene diamine (HMDA) and/or

- A polyetherdiamine compound, e.g. Jeffamine® D400 with 0.5-10% triethanolamine (TEA).

The inventors have surprisingly discovered that, by mixing a major amount of a slow-curing first crosslinker, e.g. a polyetherdiamine compound such as Jeffamine® D400, with a minor amount of a fast-curing second crosslinker, e.g. 2- methylpentamethylenediamine or HMDA, and/or with a minor amount of a crosslinking accelerator, e.g. triethanolamine (TEA), a tunable composition may be formed, in which the rate of curing and reactivity may be adjusted based on the expected temperature of the region of the subterranean formation where the composition is to be injected, by adjusting the relative amounts of the first crosslinker and second crosslinker in the crosslinking system and/or in the overall composition.

In the context of the present invention, the term "major amount" may be defined as or may be an amount of about 51 -100%, e.g., 60-100%, e.g., 75-100% e.g., 90- 100%, of the curable composition. The amounts may be expressed by weight.

In the context of the present invention, the term "minor amount" may be defined as or may be an amount of about 0-49%, e.g., 0-40%, e.g., 0-25% e.g., 0-10%, of the curable composition. The amounts may be expressed by weight.

In certain embodiments, the term "major amount" may be defined as or may be an amount of about 51 -99.5% e.g., 60-99.5%, e.g., 75-99.5% e.g., 90-99.5%, of the curable composition. The amounts may be expressed by weight.

In the context of the present invention, the term "minor amount" may be defined as or may be an amount of about 0.5-49%, e.g., 0.5-40%, e.g., 0.5-25% e.g., 0.5-10%, of the curable composition. The amounts may be expressed by weight.

The composition may be suitable for curing at a temperature in the range of 30- 50°C. The composition may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of a polyetherdiamine compound, e.g. Jeffamine® D400, with up to 10% 2- methylpentamethylenediamine, a polyetherdiamine compound, e.g. Jeffamine® D400, with up to 10% hexamethylene diamine (HMDA), and/or a polyetherdiamine compound, e.g. Jeffamine® D400, with up to 10% triethanolamine (TEA). In an embodiment, a composition suitable for curing at a temperature in the range of 30-50°C, may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of about 100 parts by weight of a polyetherdiamine compound, e.g. Jeffamine® D400 and about 3-10 parts by weight triethanolamine (TEA).

The composition may be suitable for curing at a temperature in the range of 50- 70°C. The composition may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of a polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% 2- methylpentamethylenediamine, a polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% hexamethylene diamine (HMDA), and/or a polyetherdiamine compound, e.g. Jeffamine® D400 with up to 10% triethanolamine (TEA). In an embodiment, a composition suitable for curing at a temperature in the range of 50-70°C, may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of about 100 parts by weight of a polyetherdiamine compound, e.g. Jeffamine® D400 and about 0-3 parts by weight triethanolamine (TEA), e,g, about 0.1 - 3 parts by weight triethanolamine (TEA).

The composition may be suitable for curing at a temperature in the range of 70- 90°C. The composition may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of a polyetherdiamine compound, e.g. Jeffamine® D400. The inventors have discovered that a second crosslinker and/or crosslinking accelerator may not be required in addition to the first crosslinker, when the composition is cured at a higher temperature such as at about 70-90°C. In an embodiment, a composition suitable for curing at a temperature in the range of 70-90°C, may comprise an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system consisting essentially of or consisting of a polyetherdiamine compound, e.g. Jeffamine® D400.

Thus, in a third aspect of the invention, there is provided a curable composition for treating a region of a formation, the composition comprising:

an epoxy resin comprising, consisting essentially of or consisting of 1 ,6- Hexanediol diglycidyl ether (HDDGE); and

a crosslinking system comprising, consisting essentially of or consisting of a polyetherdiamine compound, optionally Jeffamine® D400; a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of 2- methylpentamethylenediamine; a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of hexamethylene diamine (HMDA); and/or a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of triethanolamine (TEA),

wherein the composition is capable of curing in approximately 1 -10 hours at about 30-90°C, and the amount or relative amounts of the component(s) of the crosslinking system is/are selected dependent on the temperature of the region of the formation.

The composition may be capable of curing in the formation in situ. The composition may be capable of curing within approximately 15 hours from injection, e.g. within about 10 hours from injection, e.g. within about 8 hours from injection. The composition may be capable of curing within about 1 -15 hours, e.g. within about 1 -10 hours, e.g. within about 2-8 hours, e.g. 3-8 hours, from injection.

The crosslinking system may consist essentially of or may consist of Jeffamine® D400 or Jeffamine® D400 with a minor amount of 10% triethanolamine (TEA), e.g. Jeffamine® D400 with about 0-10 wt% TEA. By such provision composition may be tunable dependent on the temperature of the region of the formation, by modulating the amount of crosslinking accelerator, e.g. TEA, while avoiding the need to use different components at different ranges of temperatures.

Advantageously, the ratio of epoxy resin, e.g. HDDGE, and first crosslinker, e.g. Jeffamine® D400, may be the same or substantially the same in all compositions (e.g., for use at 30-50°C, 50-70°C, and 70-90°C). However, the amount or concentration of the second crosslinker or crosslinking accelerator, e.g. TEA, may vary dependent on the target temperature. For example, the composition may comprise about 0.05-0.2 wt %, e.g. about 0.07-0.1 wt%, of crosslinking accelerator, e.g. triethanolamine (TEA), for use in a composition suitable for curing at a temperature in the range of 30-50°C. The composition may comprise about 0.01 -0.05 wt%, e.g. about 0.02-0.03 wt%, of crosslinking accelerator, e.g. triethanolamine (TEA), for use in a composition suitable for curing at a temperature in the range of 50-70°C. The composition may be substantially free of crosslinking accelerator, e.g. triethanolamine (TEA), for use in a composition suitable for curing at a temperature in the range of 70-90°C. This may allow the formulation of a composition suitable for use in a variety of temperatures, using only two or three components.

According to a fourth aspect of the present invention there is provided a method for treating a region of a formation, comprising:

injecting a curable composition in the region of the formation, wherein the composition comprises or is a composition as described in relation to the first aspect, second aspect or third aspect of the invention.

The method may comprise curing the composition. The method may comprise curing the composition in situ. The method may comprise curing the composition within approximately 15 hours from injection, e.g. within about 10 hours from injection, e.g. within about 8 hours from injection. The method may comprise curing the composition within about 1 -15 hours, e.g., within about 1 -10 hours, e.g. within about 2- 8 hours, e.g. 3-8 hours, from injection.

The method may comprise plugging or at least partially plugging a high- permeability region of a subterranean formation, e.g. the region of the formation. The method may comprise plugging or at least partially plugging the region of the formation with the composition. This may be useful for subsequent enhanced oil recovery by water, gas, or chemical flooding. The method may comprise performing conformance control.

The method may comprise consolidating the formation, e.g. consolidating the region of the formation. The method may comprise consolidating the region of the formation with the composition. This may help reduce production of sand from the formation during production. The method may comprise performing sand control.

The method may comprise consolidating proppants, e.g. proppant particles, in the formation, e.g. in the region of the formation. The method may comprise consolidating proppants, e.g. proppant particles, in the region of the formation with the composition. This may help prevent the proppant particles being produced back into the wellbore during subsequent production of the formation. The method may comprise performing proppant consolidation.

The method may comprise treating, e.g. cementing and/or repairing, downhole equipment, e.g., casings or liners, with the composition.

The method may comprise abandoning a well.

According to a fifth aspect of the present invention there is provided the use of a curable composition according the first aspect, second aspect or third aspect of the invention for treating a region of a formation.

The composition may be used for plugging or at least partially plugging a high- permeability region of a subterranean formation, e.g. the region of the formation. This may be useful for subsequent enhanced oil recovery by water, gas, or chemical flooding. The composition may be used for performing conformance control.

The composition may be used for consolidating the formation, e.g. consolidating the region of the formation. This may help reduce production of sand from the formation during production. The composition may be used for performing sand control.

The composition may be used for consolidating proppants, e.g. proppant particles, in the formation, e.g. in the region of the formation. This may help prevent the proppant particles being produced back into the wellbore during subsequent production of the formation. The composition may be used for performing proppant consolidation.

The composition may be used for treating, e.g. cementing and/or repairing, downhole equipment, e.g., casings or liners, with the composition.

The composition may be used for abandoning a well.

According to a sixth aspect of the invention, there is provided a method for treating a region of a formation, the method comprising:

determining at least one parameter of the region of a formation; and

selecting a composition suitable for treatment of the region of a formation, the composition comprising:

an epoxy resin comprising, consisting essentially of or consisting of 1 ,6- Hexanediol diglycidyl ether (HDDGE); and

a crosslinking system comprising, consisting essentially of or consisting of a polyetherdiamine compound, optionally Jeffamine® D400; a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of 2-methylpentamethylenediamine; a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of hexamethylene diamine (HMDA); and/or a polyetherdiamine compound, optionally Jeffamine® D400, with a minor amount of triethanolamine (TEA),

wherein the amount or relative amounts of the component(s) of the composition, e.g. of the crosslinking system, is/are selected dependent on the parameter of the region of the formation.

The method may comprise determining a/the temperature of the region of a formation. The amount or relative amounts of the component(s) of the composition, e.g. of the crosslinking system, may be selected dependent on the temperature of the region of the formation.

When the temperature in the region of the formation is in the range of 30-50°C, the method may comprise selecting a composition comprising: an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of about 100 parts by weight of a polyetherdiamine compound, e.g. Jeffamine® D400 and about 3-10 parts by weight triethanolamine (TEA).

When the temperature in the region of the formation is in the range of 30-50°C, the method may comprise selecting a composition comprising: an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system comprising, consisting essentially of or consisting of about 100 parts by weight of a polyetherdiamine compound, e.g. Jeffamine® D400 and about 0-3 parts by weight triethanolamine (TEA), e,g, about 0.1 -3 parts by weight triethanolamine (TEA).

When the temperature in the region of the formation is in the range of 30-50°C, the method may comprise selecting a composition comprising: an epoxy resin comprising, consisting essentially of or consisting of 1 ,6-Hexanediol diglycidyl ether (HDDGE); and a crosslinking system consisting essentially of or consisting of a polyetherdiamine compound, e.g. Jeffamine® D400. The method may comprise (or further comprise) selecting a composition having a viscosity which permits injection of the composition at/to the region of the formation. The viscosity may be sufficiently low to permit the composition to flow to the region of the formation. The viscosity may be sufficiently high to maintain integrity of the composition during curing at the region of the formation. The selected viscosity may be dependent on one or more paramaters of the formation (for example, one or more physical paramaters, including porosity, temperature, pressure, movement and the like).

Typically the viscosity of the composition, e.g., at the time of injection, e.g. at surface, may be at least about 1 cP, e.g. at least about 100 cP, e.g. at least about 500 cP. The viscosity of the composition e.g., at the time of injection, e.g. at surface, may be in the range of about 1 cP to about 2,000 cP, e.g. about 500 cP to about 1 ,500 cP. The viscosity of the composition e.g., at the time of injection, e.g. at surface, may be about 1 ,000 cP. The viscosity at the time of injection, e.g. at surface, at surface may relate to the viscosity of the composition upon or shortly after mixing, e.g. prior to hardening or shortly after hardening has started.

Typically the viscosity of the composition, e.g., at the location where the composition is intended to be injected, e.g., at the region of the formation, may be at least about 1 ,000 cP, e.g. at least about 2,000 cP, e.g. at least about 3,000 cP. The viscosity of the composition e.g., at the location where the composition is intended to be injected, e.g., at the region of the formation, may be in the range of about 1 ,000 cP to about 100,000 cP, e.g. about 3,000 cP to about 10,000 cP.

The method may comprise preparing the composition. The method may comprise mixing one or more components of the composition, e.g., prior to injection.

The method may comprise adding one or more additives to the composition, one or more additives capable of altering, modifying and/or adjusting the viscosity of the composition, such as a solvent, a diluent, a viscosifier, a thickener, or the like. The method may comprise injecting the composition in the region of the formation.

The features described in connection with any aspect of the invention may apply to any other aspect of the invention, and are therefore not repeated in each aspect merely for reasons of brevity.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows photographs of epoxy resin plugs cured with (a) Jeffamine® D400 at 80°C, (b) HMDA at 80°C, and (c) 2-methylpentamethylenediamine (Dytek® A) at 30°C;

Figure 2 shows a photograph of an epoxy resin formulation based on 300g HDDGE and a crosslinking system containing 100% HMDA, cured at 50°C;

Figure 3 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and HMDA or Dytek® as sole crosslinker;

Figure 4 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and a combination of Jeffamine® D-400 as primary crosslinker with either Dytek® A or TEA as additional crosslinker/accelerator;

Figure 5 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and a combination of HHPA maleic anhydride as primary crosslinker with various amounts of pyridine as accelerator;

Figure 6 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and a combination of 130 pbw Jeffamine® D-400 as primary crosslinker with 10 pbw TEA as accelerator, cured at 30°C; Figure 7 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and a combination of 100 pbw Jeffamine® D-400 as primary crosslinker with 3 pbw TEA as accelerator, cured at 50°C;

Figure 8 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and Jeffamine® D-400 as sole crosslinker, cured at 80°C;

Figure 9 is a graph showing curing characteristics for a composition containing a HDDGE epoxy resin and a combination of 100 pbw Jeffamine® D-400 as primary crosslinker with 3 pbw TEA as accelerator, cured at 50°C;

Figure 10 shows a schematic view of an embodiment of an assembly for mixing and injecting a composition of the present invention;

Figure 1 1 shows a schematic view of another embodiment of an assembly for mixing and injecting a composition of the present invention;

Figure 12 shows DSC data for 30-50°C, 50-70°C and 70-90°C formulations according to embodiments of the present invention;

Figures 13(a) to 13(c) are schematic representations illustrating the effect of curing times on the intended treatment;

Figures 14 (a) and 14(b) are schematic representations illustrating the effect of the viscosity of the composition on the intended treatment. DETAILED DESCRIPTION OF THE DRAWINGS

Experimental

Materials

The following materials were used during investigation of the curing compositions according to the present invention.

Name 1 ,6-Hexanediol Diglycidyl Ether (HDDGE) Epoxy sealant Tradenames ARALDITE® DY-H /CH

ARALDITE® GY 764 CH

D.E.R. 734 Epoxy Diluent

Epilox P 13-20

EPOTEC RD 107

GRILONIT RV 1812

Hexanediol Diglycidyl Ether

CAS number 933999-84-9

Registrants (ACTIVE REACH)

Blue Cube Chemicals Italy S.r.l. via F.AIbani 65 2018 Milano Italy

Harke Services GmbH-OR3 Xantener Str.1 45479 Miilheim an der Ruhr Germany

Hexion GmbH Gennaer Strasse 2-4 D-58642 Iserlohn North Rhine-Westphalia Germany

Huntsman Advanced Materials (Europe) BVBA Everslaan 45 B-3078 Everberg Belgium

Huntsman Advanced Materials (Europe) BVBA OR-C Everslaan 45 B-3078 Everberg Belgium

ITS Testing Services (UK) Ltd 9 Caleb Brett House 734 London Road RM20 3NL West Thurrock, Grays Essex United Kingdom

LEUNA-Harze GmbH Am Haupttor, Bau 6619 D-06237 Leuna Germany Germany

Sir Industriale Spa Via Bellini 35 20050 Macherio MONZA-Brianza Italy

Name Jeffamine® D400 Amine Hardener

Tradenames Jeffamine® D400

CAS number 9046-10-0

Registrants (ACTIVE REACH)

BASF SE Carl-Bosch-Str. 38 67056 Ludwiqshafen am Rhein Rheinland-Pfalz Germany

Huntsman (Europe) BVBA - OR1 Everslaan 45 B-3078 Everberg Belgium

Name Hexamethylenediamine Amine Hardener

Tradenames 1 ,6-Diamino-n-hexane 1 ,6-Diamino-n- hexane 1 ,6-Diaminohexane 1 ,6-Diaminohexane

1 ,6-Hexandiamin

CAS number 9046-10-0

Registrants (ACTIVE REACH)

A.Schulman GmbH Huttenstrasse, 21 1 D 50170 Kerpen Germany

Arizona Chemical AB OR1 Massvagen 15 P.O. Box 66 SE-820 22 Sandarne

Sweden

ARKEMA FRANCE 420 rue d'Estienne d'Orves 92700 COLOMBES France

Ascend Performance Materials srpl/bvba Watson & Crick Hill Park 1 1 , rue

Granbonpre - Batiment H B-1348 Louvain-la-Neuve Walloon Brabant Belgium

BASF SE Carl-Bosch-Str. 38 67056 Ludwigshafen am Rhein Rheinland-Pfalz

Germany

BorsodChem Zrt. - OR Bolyai ter 1. H-3700 Kazincbarcika Hungary

BUTACHIMIE Immeuble Le Forum 29 RUE MAURICE FLANDIN 69003 LYON

France

Celanese Europe BV Daalwijkdreef 25 1 103 AD Amsterdam Netherlands

Covestro Deutschland AG Kaiser-Wilhelm-Allee 60 51373 Leverkusen Germany Envigo Consulting Limited Woolley Road Alconbury PE28 4HS Huntingdon Cambridgeshire United Kingdom

Envigo Research Limited 24 Shardlow Business Park London Road DE72 2GD Shardlow Derbyshire United Kingdom

Evonik Resource Efficiency GmbH Rellinghauser Strasse 1-1 1 45128 Essen Germany

Fista 't Ven 35 5091 BN Middelbeers Netherlands

INEOS Nitriles (UK) Ltd (M & I) PO Box 62 Seal Sands TS2 1 TX Middlesbrough United Kingdom

INVISTA Textiles (U.K.) Limited 100 Barbirolli Square M2 3AB Manchester United Kingdom

Radici Chimica S.p.A. via Fauser 50 28100 Novara Italy

REACH24H CONSULTING GROUP Suite 1 E, Paramount Court, Corrig Road, Sandyford Dublin 18 Dublin Ireland

RHODIA IBERIA SL Calle de Capitan Haya, 1-6° 28020 MADRID Spain

RHODIA OPERATIONS 40 rue de la Haie Coq 93306 AUBERVILLIERS France

RHODIA OPERATIONS - 1 40 rue de la Haie Coq 93306 Aubervilliers France

SABIC Innovative Plastics BV Plasticslaan 1 4612 PX Bergen op Zoom Netherlands Netherlands

Shakespeare Monofilament UK Ltd. Enterprise Way FY7 8RY Fleetwood Lancashire United Kingdom

SOLVAY ENGINEERING PLASTICS POLAND Sp.zo.o ul. Walczaka 25 66-407 Gorzow Wielkopolski Poland

Solvay Specialty Polymers Italy S.p.A. Viale Lombardia 20 20021 BOLLATE Italy

YF International b.v. Burg, van Dorth tot Medlerstraat 34 6921 AZ Duiven Netherlands

Name 2-methylpentamethylenediamine \m;>7e Hardener

Tradenames Dytek® Amine A

CAS number 15520-10-20

Registrants (ACTIVE REACH)

Sigma Aldrich

Name Triethanolamine (TEA) Crosslinking Hardener

Tradenames 2,2',2"-Nitrilotriethanol

2,2',2"-Nitrilotris[ethanol]

Alkanolamine 244

Daltogen

Ethanol, 2,2',2"-nitrilotri- (8CI)

Ethanol, 2,2',2"-nitrilotris- (9CI)

Nitrilotriethanol

Sterolamide

Sting-Kill

TEA

TEA (amino alcohol)

TEOA

Thiofaco T 35

Thiofaco T35

Trietanolamina 85% Trietanolamina 99%

Trietanolamina 99% D85

Trietanolamina 99% D95

Trietanolamina grado aditivo

Triethanolamin

TRIETHANOLAMINE TRIETHANOLAMINE 80%

Triethanolamine 85

Triethanolamine 99

TRIETHANOLAMINE COMMERCIAL LOW FREEZING

GRADE (PM-4447)

TRIETHANOLAMINE, 99%

TRIETHANOLAMINE, Commercial Grade

Tris(.beta.-hydroxyethyl)amine

Tris(2-hydroxyethyl)amine

Trolamine

CAS number 102-71-6

Registrants (ACTIVE REACH)

Sigma Aldrich

Name Cyclohexane-1 ,2-dicarboxylic anhydride (HHPA)

Anhydride hardener

Tradenames Hexahydrophthalic anhydride

HHPA

CAS number 85-42-7

Registrants (ACTIVE REACH)

Envigo Consulting Limited Woolley Road Alconbury PE28 4HS Huntingdon Cambridgeshire United Kingdom

POLYNT S.p.A. via Enrico Fermi, 51 I-24020 Scanzorosciate BG Italy

REACh ChemAdvice GmbH Am Marktplatz 5 65779 Kelkheim (Taunus) Germany

Τϋν SOD Iberia S.A.U. (051) C/ Frederic Mompou 4A, 1 ° 4° 08960 Sant Just Desvern (BCN) Barcelona Spain

Experiments and Results

Curing of compositions using different crosslinking systems was investigated.

1 ) Visual assessment of single-compound crosslinking systems

Plugs using 1 ,6-Hexanediol Diglycidyl Ether (HDDGE) and each of Jeffamine® D400, 2-methylpentamethylenediamine (Dytek® A), and hexamethylene diamine (HMDA) were cured at the following temperature:

- Jeffamine® D400 at 80°C, - HMDA at 80°C, and

2-methylpentamethylenediamine (Dytek® A) at 30°C.

The resulting cured plugs are shown on Figure 1. It can be seen that the appearance of the cured plugged can vary greatly depending on the curing agent, from (a) opaque (Jeffamine® D-400), to (b) translucent (HMDA), to (c) transparent/clear (Dytek® A).

2) Investigation of single compound crosslinking systems

Dytek® A and HMDA constituted potentially suitable crosslinkers, and were investigated individually.

An epoxy resin formulation based on 300g HDDGE and a crosslinking system containing 100% HMDA was tested at 50°C. As shown in Figure 2, this resulted in a flash set reaction. The curing reaction of the 300 g epoxy resin was found to be vastly exothermic with production of heat and smoke. Without wising to be bound by theory, it is believed that the reason for this behaviour is the highly exothermic nature of the HMDA hardener.

This highlights the following two important points:

1 ) The exothermic properties of the hardeners must be understood before any upscaling is done; and

2) An exothermic hardener should not be used for large volumes or for applications where the heat generated from the reaction cannot escape to the surroundings.

As such, it was concluded that Dytek® A and HMDA were not suitable as sole crosslinkers in curing compositions suitable for upscaling in subterranean environments. 3) Investigation of Jeffamine®-crosslinking systems

Jeffamines have relatively low exothermic curing properties. Table 1 provides an overview of curing tests using HDDGE as epoxy resin, Jeffamine® D-400 as crosslinker, and a number of compounds used an additional crosslinkers or crosslinking accelerators.

Table 1

Chemical Accelerator Cure @30 C Cure @50 C Feasible as suitable epoxy formulation?

HMDA None Full cure (3 hours) No, reaction is strongly exothermic!

Dytek® Amine A None Full cure (3 hours) No, reaction is strongly exothermic!

Jeffamine® D400 3% Pyridine No cure (16 hours) No cure (5 hours) No

Jeffamine® D400 3% DMAPA No cure (16 hours) No cure (5 hours) No

Jeffamine® D400 3% TEA No cure (16 hours) Partly cured No

(5hours)

Jeffamine® D400 6% TEA No cure (16 hours) Full cure (6 hours) No

Jeffamine® D400 6% Salicylic No cure (16 hours) No

acid/methanol

Jeffamine® D400 6 % Glycerin No cure (16 hours) Full cure (6 hours) No

Jeffamine® D400 10 % TEA Partly cured (24 Full cure (6 hours) No

hours)

Jeffamine® D400 10 % Glycerin Partly cured (24 Full cure (6 hours) No

hours)

Jeffamine® No cure (24 hours) No

D400/ 10%

Dytek®

Jeffamine® No cure (24 hours) No

D400/ 25%

Dytek®

Jeffamine® Full cure (24 hours) No

D400/ 50%

Dytek®

Jeffamine®D400 +30% D400 Full cured (12 hours) Yes

+10% TEA

Jeffamine®D400 +50% D400 Full cure (24 hours) No

+10% TEA

The results shown in Table 1 show that the behaviour of the choice of crosslinker(s), crosslinking accelerator(s), and amounts thereof, greatly affects the speed and exothermic properties of the crosslinking reaction, and that careful selection is required to obtain a curing composition suitable for application in subterranean environments, particularly in a range of temperatures of 30-90°C, when the desired curing time is about 1 -10 hours, e.g. within about 2-8 hours, e.g. 3-8 hours, from injection. From the results shown in Table 1 , the most promising results were obtained with a crosslinking system containing 130 parts by weight Jeffamine® D-400 and 10 parts by weight TEA.

4) Investigation of possible hardening systems potentially suitable for scale up in 10-gram curing tests

The purpose of these tests was to determine which hardeners, and in what proportions, can be scaled-up in amounts without showing a tendency to exothermic curing. The tests were performed at 30°C, 50°C and 70°C, and are shown in Table 2.

Table 2

Primary Hardener Tested for Accelerator/2nd Curing time Peak T increase hardener

Dytek® A 30-50C form - 85 min 120 C

HDMA 30-50C form - 92 min 100 C

Jeffamine® D400 50-70C form 6 % TEA 65 min 18 C

Jeffamine® D400 50-70C form 10 % Dytek® 128 min 5 C

HHP A/ma I 70-90C form 1.5 % pyridine 33 min 85 C

HHPA/mal 70-90C form 1.0% pyridine 45 min 72 C

HHPA/mal 70-90C form 0.25 % pyridine 180 min 5 C

HHPA/mal 70-90C form 0.1 % pyridine 300 min 2 C

As shown in Figure 3, both HMDA and Dytek® exhibited very exothermic curing with large increases in temperature during curing. Both these hardeners were therefore considered unsuitable alone or in high ratios in the crosslinking system.

Jeffamine® D-400 tests are shown in Figure 4. A test with 6% TEA accelerator revealed an increase in temperature of 18°C which was considered acceptable. Also tested was a Jeffamine® D-400 sample with 10% Dytek® Amine A crosslinker which produced a temperature increase of only 5°C. The use of Dytek® Amine A in small concentrations below 10 % therefore appeared to be acceptable.

HHPA/maleic anhydride tests are shown in Figure 5 with different accelerator concentrations of 1.5%, 1 .0%, 0.25% and 0.1 % pyridine accelerator. It can be seen that HHPA/malic produce extensive heat when the concentration of pyridine accelerator is 1 % or above. At concentrations of 0.25 % or below the heat release was considered to be acceptable.

5) Investigation of first level scale up in 300-gram curing tests

The results of curing tests performed on 300g samples are shown in Table 3.

Table 3

Target T Formulation Curing time Cured Avg. T Suitable for

Range at temp. increase upscaling?

30-50C 130% Jeff >7 hours 30 C 31 ,5 C 2.5 C Yes

D400, 10 %

TEA

50-70C Jeff D400, 6 hours 50 C 50 C 4 C Yes

3 % TEA

70-90C HHPA/maleic, Partly cured after 80 C 80 C - No

0.2 % Pyridine 24 hours (water

degradation

suspected)

70-90C Jeff D400, 1 hour 45min 80 C 86 C 12 C Yes

0% TEA

As shown in Table 3, and in Figures 6 and 7, respectively, both the 30-50°C and 50-70°C formulations cured in a controllable way. In both cases the temperature of the epoxy increased slightly by a few degrees to temperatures above the temperature of the heat bath.

The first 70-90°C formulation to be tested was based on HHPA maleic anhydride with 0.2% pyridine. This formulation did, however, not cure even after 12 hours. The sample was seen to be discoloured and it is suspected that the hardener had been contaminated by water. As an alternative to HHPA maleic anhydride, Jeffamine® D400 without accelerator was tested for high temperature curing (see Figure 8). A formulation with no added accelerator was measured and found to cure in 1 hour and 45 minutes. This demonstrates that Jeffamine® D-400 is a suitable crosslinker for high temperature applications.

6) Investigation of first level scale up in 1.8-kg curing tests

The results of curing tests performed on 1.8kg samples are shown in Table 4. Both the 30-50°C formulation and the 50-70°C formulation (see Figure 9) were found to be suitable for further upscaling, with adequate curing times and increase in temperature during cure.

Table 4

Target T Formulation Curing time Cured at Avg. T Suitable for

Range (crosslinking temp. increase upscaling? composition)

30-50C 130% Jeff D400, 13.7 hours 30 C 32 C 3.5 C Yes

10 % TEA

50-70C Jeff D400, 5 hours 50 C 55 C 7.5 C Yes

3 % TEA

7) Investigation of second level scale up in 10-kg and 25-kg curing tests

The results of curing tests performed on 10kg and 25kg samples are shown in Table 5. All formulations were found to have adequate curing times and increase in temperature during cure.

Table 5

Target T Formulation Batch size Curing time Cured at Avg. Peak T

Range (crosslinking temp. increase composition)

30-50°C 130% Jeff D400, 10 kg ~3 hours 30°C 43°C 24°C

10 % TEA

50-70°C Jeff D400, 25 kg 10 hours 30°C 41 °C 15°C

3 % TEA 30min

70-90°C Jeff D400 25 kg 10 hours 40°C 48°C 13°C

(0 % TEA )

30-50°C 130% Jeff D400, 25 kg 5 hours 50 30°C 39°C 15°C

10 % TEA min 8) Relative amounts in example formulations

Typical amounts used in compositions for use at three different ranges of temperature are shown in Table 6.

Table 6

Hardener Resin Accelerator Sum

Jeffamine® D400 HDDGE Triethanolamine

30-50°C 0,466 bbl 0,456 bbl 0,084 bbl 1 ,00 bbl

50-70°C 0,493 bbl 0,482 bbl 0,027 bbl 1 ,00 bbl

70-90°C 0,507 bbl 0,496 bbl 0,0 bbl 1 ,00 bbl

9) Closed bottle test

To simulate a worst-case scenario where the epoxy formulation is mixed at room temperature without allowing any heat escape, closed bottle tests were conducted. The experiment involves mixing the resin, hardener and accelerator (if applicable) in a thermally isolated container and track the temperature rise. The tests were expected to give an indication of the likelihood for any of the formulations to flash- set at room temperature.

Four environmentally friendly epoxy formulations were tested, i.e. the 3 conventional formulations tested in the upscaling (130% D400 + 10% TEA (30-50°C), 100% D400 + 3% TEA (50-70°C) and 100% D400 (70-90°C)) along with one formulation using Dytek® A to decrease curing time at 30°C (100% D400 + 30% Dytek® + 10% TEA). All the tests were conducted using a total mass of 25 g. The results are presented in Table 7.

The results show that none of the formulations produce enough heat at room temperature to cause a flash-set of the epoxy mixture. These results should be taken with caution since the data assumed that the closed bottle setup is thermally isolated, which is not strictly true. This is seen by the fact that the temperature the conventional formulations (that were measured for 3 days) shows an obvious correlation to the room temperature. Additionally, it is seen that the curing at room temperature also generates heat leading to a temperature increase of the epoxy mixture. This shows that after mixing the epoxy formulations the mixture has to be pumped and placed where it is intended to be injected and cured within a relatively short period of time.

The main results of the closed bottle tests are summarized in Table 7. Evidently there is a certain enthalpy of mixing in these system since the initial temperature measured right after mixing the chemicals is considerable higher than room temperature, ~4°C for all formulations. All the formulations show a gradual increase in temperature above room temperature that peaks before dropping slowly back to room temperature. For the formulations without Dytek®, the peak temperature is highest for the 30-50°C formulation and it occurs fastest. This is not unexpected since the low temperature formulation is designed to work at temperatures slightly above room temperature while the higher temperature formulations need higher temperature to cure optimally. The new 30°C with Dytek® formulation shows the highest and fastest temperature peak by far compared to the other formulations. This indicates that care should be taken in mixing large batches of epoxy formulations that contain Dytek® A.

Table 7

50-70°C 30°C_new

30-50°C

100% 70-90°C 100%D400+

130%

D400+3%TEA 100% D400 10%TEA+ D400+10%TEA

30%Dytek®

Initial 28°C 28°C 27.5°C 29°C temp

T peak 27.9°C 27.6°C 26.2°C 36.2°C

Time to 6 hours 17 min 8 hours 9 hours 3 hours 4 min peak T 10) Differential Scanning Calorimetrv

Differential scanning calorimetry (DSC) measurements were performed for the formulations tested in the upscaling (130% D400 + 10% TEA (30-50°C), 100% D400 + 3% TEA (50-70°C) and 100% D400 (70-90°C). The DSC data can give more quantitative results about the heat released during the curing as opposed to the more qualitative results obtained in the closed bottle tests. Here the data can be analysed to obtain onset temperature of the curing process, the temperature where most heat is released during curing, the total heat release during curing along with the onset temperature of the flash-set.

The DSC data is presented in Figure 12 and shows how much heat is consumed or released while the epoxy formulations are heated from room temperature to ~120°C. A peak pointing upward represents a heat release (exothermic reaction) while a downward pointing peak (valley) represents a consumption of heat (endothermic reaction). All the formulations show the same general trend in the heat release in this temperature range. A broad and relatively weak exothermic peak appears from room temperature to ~70-80°C. This peak represents the curing process of the epoxy formulation. At higher temperatures another, more intense, exothermic peak appears. Without wishing to be bound by theory, it is thought that this peak may represent the flash-set process where so much heat is released that the temperature of the epoxy mixture increases uncontrollably if the heat is not removed efficiently.

The results of the DSC measurements are summarized in Table 8. The onset temperature for the curing process is very close to room temperature for all the formulations indicating that the curing process starts already at room temperature even though the formulations are designed to cure at higher temperatures. The exothermic peak temperature is also very similar for all formulations, ~40-45°C. This means the maximum rate of heat release happens at this temperature for all formulations. This was not unexpected since all the formulations utilize the same chemistry, i.e. curing HDDGE with Jeffamine® D400 and the only difference is the concentration of the accelerator, triethanolamine. The accelerator works as a catalyst during the curing and therefore only affects the reaction kinetics and not the thermodynamics. The unchanged thermodynamics are also nicely illustrated in the total heat release during curing. It increases going from the low to high temperature formulations. This is because the accelerator does not produce any heat but contributes to the total mass of the formulation. Therefore, some of the heat produced by the reaction between the resin and hardener must be utilized to heat up the accelerator giving less heat released per unit mass of the epoxy formulation. The DSC results lastly show that the lowering of accelerator concentration going to higher temperature formulations is efficient in increasing the onset temperature of the flash-set process. This is of importance since the high temperature (70-90°C) formulation is supposed to work close to the flash-set onset temperature and having it as high as possible decreases the risk of flash-setting if the heat is not removed efficiently.

Table 8

30-50°C 50-70°C 70-90°C

Curing onset T 24°C 23°C 25°C

Curing peak T 41 °C 41 °C 45°C

Peak area (heat release) 3.0 J/g 7.0 J/g 8.5 J/g

Flash -set onset T 70°C 75°C 90°C

1 1 ) Considerations regarding field application

For the environmental epoxy resins of the present invention to be used successfully and safely applied in the field, the mixing step where resin and hardener is important. In particular the inventors observed the following

• As soon as the hardener and resin are mixed, curing starts and thus heat starts to be generated. If the heat is not conducted away from the epoxy it could result in flash setting of the epoxy. • The amount of mixed epoxy at surface should be as low as possible to limit the risk of flash setting and to limit the damages if it occurs. Once the epoxy is injected in the well, heat is expected to be transported effectively away from the epoxy to the near wellbore section. For this reason, an "on-the-fly" type of mixing may be preferable over batch mixing as the amount of mixed epoxy at surface in that instance is kept to a minimum (see Figures 10 and 1 1 ).

• In the event that the pumping job needs to be stopped, for example because of an increase in backpressure, power cut, etc., the present environmental epoxy resins can be discarded, for example at sea.

· The hardener and the resin may be cooled prior to mixing to reduce the risk of flash setting. This could be done by cooling the chemicals with cold sea water through a coil immersed in the epoxy tanks (see Figures 10 and 1 1 ).

• The temperature of the epoxy should be monitored at critical locations such at the inlet to the pump and inside the batch mixer to ensure that it stays low throughout the pumping job.

Embodiments of set-ups for preparation of the composition of the present invention are shown in Figures 10 and 11.

Figure 10 shows a schematic view of an embodiment of an assembly for mixing and injecting a composition of the present invention. In this embodiment, the resin is stored in a resin container 10a and the crosslinking composition is stored in a crosslinker container 20a. Resin and crosslinker are mixed as a batch in a batch container 30a, which is kept cooled by a cooling device 40a. When required, the mixed composition 35a is pumped via pump 50a into tubing 60a for injection in a well.

Figure 1 1 shows a schematic view of another embodiment of an assembly for mixing and injecting a composition of the present invention. In this embodiment, the resin is stored in a resin container 10b and the crosslinking composition is stored in a crosslinker container 20b. Resin and crosslinker are each kept cooled by cooling devices 41 b and 42b. When required each of the resin and crosslinker can be pumped via respective pumps 51 b and 52b into and mixed in container 30b. The mixed composition 35b can then be pumped via pump 53b into tubing 60b for injection in a well.

Effects of curing times and viscosity

Figure 13 is a schematic representation illustrating the effect of curing times on the intended treatment. As shown in Figure 13(c), in the event of premature hardening, i.e. when the curing time of the composition is too short, the composition 135 hardens before it can reach the location intended to be treated (here a region 180 of a channel). Conversely, as shown in Figure 13(c), in the event of delayed hardening, i.e. when the curing time of the composition is too long, the composition does not form an effective plug within the channel 180, and a fluid, e.g. formation fluid, may still be able to trickle or pass through or around the plug 135. As shown in Figure 13(b), in order to achieve an effective plug 135 at a desired location 180 of the channel, the composition was selected to exhibit an adequate curing time under the conditions in the formation, e.g. at about 30°C-90°C.

Figure 14 is a schematic representation illustrating the effect of the viscosity of the composition on the intended treatment. In the present embodiment, a composition 235 is injected into a liner 270 having perforations 272, for creating an annular plug around the liner 270. As shown in Figure 14(a), a 7" liner 270 was sealed off with two inflatable packers 274, 275, inside the liner 270. The liner 270 is placed inside a 8.5" open hole and the aim is to create a solid plug that closes the void spacing between the liner 270 and the formation. An epoxy composition was injected from an upper packer (not shown) via an attached coil tubing 278. The injected epoxy 235 flows towards the perforation holes 272 of the liner 270. Figure 14(b) illustrates the shape and the integrity of the formed plug using a computational model, based on different viscosities of the epoxy composition. In Figures 14(a) to 14(c), the indicated values relate to the viscosities of the composition in situ at the point of delivery, that is, when the composition reaches the perforations 272 and/or enters the surrounding annulus. A person of skill in the art will appreciate the corresponding viscosities at the time of injection, e.g. at surface, will be significantly lower, as the composition starts hardening upon or shortly after mixing. With an in situ viscosity of about 100 cP (bottom), the resulting plug slumps into the lower part of the annulus before it can fully harden. With a viscosity of about 3,000 cP (middle), the resulting composition forms an annular plug around the liner 270, with more material near a lower region of the annulus than near an upper region of the annulus. With a viscosity of about 10,000 cP (top), the resulting composition forms a relatively uniform annular plug 235 around the liner 270.

Conclusions

In formulations for use in low temperature environments (30-50°C or 50-70°C), optimum results were found for curing systems using TEA and/or Dytek® A in concentrations below 10%. These were found to be most effective when used in combination with a major amount of Jeffamine® D-400 as the main crosslinker.

In formulations for use in high temperature environment (70-90°C), optimum results were found for curing systems using Jeffamine® D400. This selection also reduces the number of chemicals compared with the previously contemplated option of HHPA/maleic anhydride, thus reducing costs and delivery times.