NO344577B1 - Methods for inhibiting hydrate blockages in oil and gas pipelines using simple quaternary ammonium and phosphonium compounds - Google Patents

Description

Background for the invention

The field of invention

This invention relates to the prevention of gas hydrate blocking in oil and natural gas pipelines containing low-boiling hydrocarbons and water. More specifically, the invention relates to a method for controlling gas hydrate blocking by adding different chemical mixtures.

Background of related art

When hydrocarbon gas molecules dissolve in water, the hydrogen-bonded network of water molecules encapsulates the gas molecules to form a cage-like structure or hydrate. Higher pressures and lower temperatures promote the formation of these structures. These hydrates grow by encapsulating more and more gas molecules to form a crystalline mass. The crystalline mass agglomerates to form a larger mass which can result in a clogged transfer line. The hydrocarbon gases that form most of the hydrates include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane and combinations of these gases.

Thermodynamic hydrate inhibitors, such as methanol or one of the glycols, has traditionally been used to prevent these hydrate formations. These thermodynamic inhibitors are effective by 5 to 30% (or more) based on the amount of water. As oil companies conduct exploratory drilling for new production in deep water, total gas/oil/water production also increases. The use of these thermodynamic inhibitors cannot be used in these applications due to logistics. Kinetic hydrate inhibitors have been identified to be able to prevent these hydrate formations so that the fluids can be pumped out before a catastrophic hydrate formation occurs. The kinetic inhibitors prevent or delay hydrate crystal nucleation and interrupt crystal growth. These kinetic hydrate inhibitors contain units similar to the above-mentioned gas molecules. It is believed that these kinetic inhibitors prevent hydrate crystal growth by being incorporated into the growing hydrate crystals so that further hydrate crystal growth is interrupted. The growing hydrate crystals complete a cage structure by combining with the partial hydrate-like cages around the kinetic hydrate inhibitor units containing gas-like groups. These inhibitors are effective with or without the presence of a liquid hydrocarbon phase, but they are typically less effective in preventing hydrate formation as production pressure increases. Examples of kinetic hydrate inhibitors include poly(N-methylacrylamide), poly(N,N-dimethylacrylamide), poly(N-ethylacrylamide), poly(N,N-diethylacrylamide), poly(N-methyl-N-vinylacetamide), poly (2-ethyloxazoline), poly(N-vinylpyrrolidone) and poly(N-vinylcaprolactam).

Unlike kinetic hydrate inhibitors, anti-agglomerate hydrate inhibitors are effective only in the presence of an oil phase. These inhibitors do not inhibit the formation of gas hydrates to the same extent as kinetic inhibitors, as their primary activity is rather to prevent the agglomeration of hydrate crystals. The oil phase provides a transport medium for the hydrates which are referred to as hydrate slurries so that the overall viscosity of said medium is kept low and it can be transported along a pipeline. As such, the hydrate crystals formed in the water droplets are prevented from agglomerating into a larger crystalline mass.

Examples of several chemicals that act as antiagglomerate hydrate inhibitors are reported in US Patents 5,460,728; 5648 575; 5,879,561 and 6,596,911. These patents teach the use of quaternary ammonium salts having at least three alkyl groups of four or five carbon atoms and a long chain hydrocarbon group containing 8 to 20 atoms. Exemplary mixtures include tributylhexadecylphosphonium bromide and tributylhexadecylammonium bromide.

More specifically, US patent 5460 728 (Klomp) teaches the use of alkylated ammonium, phosphonium or sulfonium compounds with three or four alkyl groups in their molecule, at least three of which are independently selected from the group of normal or branched alkyls with four to six carbon atoms. US patent 5648 575 (Klomp) teaches very similar mixtures with three or four organic groups in their molecule, at least three of which have at least four carbon atoms, i.e. two normal or branched alkyl groups with at least four carbon atoms and with a further organic unit containing a chain with at least four carbon atoms. US Patent 5,879,561 (Klomp) teaches the use of alkylated ammonium or phosphonium compounds having four alkyl groups, two of which independently are normal or branched alkyls of four or five carbon atoms and two or more of which independently represent organic units of at least eight carbon atoms.

US patent 6369 004 B1 (Klug) teaches the kinetic inhibition of gas hydrate formation using polymers based on the reaction of maleic anhydride with one or more amines. These polymers can also be used together with various other substances, called synergists, and which include tetrabutylammonium salts, tetrapentylammonium salts, tributylamine oxide, tripentylamine oxide, zwitterionic compounds with at least one butyl or pentyl group on the quaternary ammonium nitrogen atom, such as Bu3N<+>-CH2-COO-. However, kinetic inhibitors are not effective when pipeline pressure increases.

US patent 6015 929 (Rabeony) teaches the use of zwitterionic compounds such as R(CH3)2N<+>-(CH2)4-SO3<->as antiagglomerate hydrate inhibitor. The synthesis of this product involves the use of butyl sultone.

WO 02/066785 relates to a method and a composition for use therein, to inhibit the formation of hydrocarbon hydrates. The composition comprises an onium compound, an amine salt and optionally a solvent. The method and composition are particularly useful in oil and gas production.

However, there is still a need for hydrate inhibitor compounds. which effectively prevents the agglomeration of hydrates in processes for the transport and handling of oil and gas. It would be desirable to identify hydrate inhibitor compounds that are effective at higher pressures and/or lower temperatures such as e.g. those occurring in deepwater production. It would be even more desirable if the same compounds had increased biodegradability.

Summary of the invention

The present invention provides methods for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water as stated in the independent claims 1, 9, 25, 26 and 27.

Certain simple quaternary ammonium and phosphonium compounds are suitable for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, by adding to the mixture an effective amount of at least one hydrate inhibitor compound. A preferred family of hydrate inhibitor compounds has the formula:

in which

R 1 is selected from hydrogen and normal or branched alkyls having from 1 to 3 carbon atoms,

R 2 is selected from normal or branched alkyls having from 1 to 4 carbon atoms, preferably exactly 4 carbon atoms. It should be realized that R1 and R2 can be the same or different, as e.g. where R1 and R2 each have exactly 1 carbon atom;

R 3 is an organic unit of 4 or 5 carbon atoms;

R4 is an organic unit with from 2 to 20 carbon atoms. In certain embodiments, R 4 may be selected from alkyl, alkenyl, aryl, arylalkyl, arylalkenyl, alkylaryl, alkenylaryl, glycol, and combinations thereof. Alternatively, R 4 may include one or more heteroatoms selected from oxygen, nitrogen, sulfur and combinations thereof. Even further, R4 can be chemically bound to a polymer. In one embodiment, R 4 is-[(CH 2 -CHR 5 -O)]n-H, wherein R 5 is selected from hydrogen, a methyl group, and an ethyl group, and n is in the range of 1 to 3;

A is a nitrogen atom (N) or a phosphorus atom (P).

X- is anion. E.g. X- can be selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate and combinations thereof. Suitably, the X anion may be a halide ion selected from bromide, chloride and combinations thereof.

In a preferred embodiment, said at least one compound is the product of a reaction between an organic halide with one of R1, R2, R3 and R4 and an amine or phosphene containing the other three of R1, R2, R3 and R4. E.g. said at least one compound can be the product of the reaction between butyl bromide and N,N-dimethylalkylamine with between 10 and 20 carbon atoms. Suitably, the N,N-dimethylalkylamine may be N,N-dimethylhexadecylamine.

Brief description of the drawings

Fig. 1 is a graph of a temperature and pressure profile used in figures 3-17.

Fig. 2 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for an untreated mixture of hydrocarbon and water.

Fig. 3 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% trimethylhexadecylammonium bromide.

Fig. 4 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dimethylethylhexadecylammonium bromide.

Fig. 5 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dimethylbutylhexadecylammonium bromide.

Fig. 6 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dimethylbutyl octadecylammonium bromide.

Fig. 7 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dipropylbutylhexadecylammonium bromide.

Fig. 8 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dibutylpropylhexadecylammonium bromide.

Figures 9a and 9b are graphs of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% and 1% tributylhexadecylammonium bromide, respectively.

Fig. 10 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% dimethyldihexadecylammonium bromide.

Fig. 11 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% N,N-dibutylcocoamidopropylcarbomethoxybetaine.

Fig. 12 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% N,N-dibutylaminococoamidopropylamine oxide.

Fig. 13 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% N,N,N-tributylcocoamidopropylammonium bromide.

Fig. 14 is a graph of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% N,N-dibutylhexadecylcocoamidopropylammonium bromide.

Figures 15a and 15b are graphs of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% and 1% N,N-dibutylhexadecyltriethoxyammonium bromide, respectively.

Figures 16a and 16b are graphs of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% and 1% tributylhexadecylphosphonium bromide, respectively.

Figures 17a and 17b are graphs of sensor activation time (a measure of hydrate formation and blocking) as a function of time for a mixture of hydrocarbon and water treated with 3% and 1%, respectively, of a mixture of N,N-dibutylcocoamidopropylcarboethoxybetaine and amine salt.

Detailed description

This invention relates to a method and a mixture used therein to inhibit, slow down, remedy, reduce, control and/or delay the formation of hydrocarbon hydrates or agglomerates of hydrates. The procedure can be carried out to prevent or reduce or remedy the plugging of pipelines, pipes, transmission lines, valves and other places or equipment where hydrocarbon hydrate solids can form under the relevant conditions.

The term "inhibition" is used herein in a broad and general sense to denote any improvement in preventing, controlling, delaying, reducing or ameliorating the formation, growth and/or agglomeration of hydrocarbon hydrates, particularly light hydrocarbon gas hydrates on any manner, including but not limited to kinetic, thermodynamic, dissolution, breakdown, other mechanisms, or any combination thereof.

The term "formation" or "formation" relating to the hydrates is used herein in a broad and general manner to include, but is not limited to, any formation of hydrate solids from water and one or more hydrocarbons or one or more hydrocarbon gases, growth of hydrocarbon hydrate solids, agglomeration of hydrocarbon hydrates, accumulation of hydrocarbon hydrates on surfaces, any reduction in hydrate solids plugging or other problems in a system and combinations thereof.

The present method is useful for inhibiting hydrate formation for many hydrocarbons and hydrocarbon mixtures. The method is particularly useful for lighter or low-boiling, C1-C5, hydrocarbon gases or gas mixtures under ambient conditions. Non-limiting examples of such "low boiling" gases include methane, ethane, propane, n-butane, isobutane, isopentane and mixtures thereof. Other examples include various natural gas mixtures present in many gas and/or oil-bearing formations and natural gas liquids (NGLs). The hydrates of all these low-boiling hydrocarbons are also referred to as gas hydrates. The hydrocarbons may also include other compounds including but not limited to CO2, hydrogen sulphide and other compounds commonly found in gas/oil formations or processing facilities, either naturally occurring or used in the extraction/processing of hydrocarbons from the formation or both, and mixtures thereof.

The method according to the present invention involves bringing a hydrocarbon and water mixture into contact with a suitable compound or mixture. When an effective amount of the compound is used, hydrate blocking is inhibited. In the absence of such an effective amount, hydrate blocking is not inhibited.

The contact can be achieved in a number of different ways, including mixing, mixing with mechanical equipment or devices for mixing, stationary mixing assemblies or equipment, magnetic mixing or other suitable methods, other equipment and devices known to those skilled in the art, and combinations thereof to provide good contact and/or dispersing the composition in the mixture. The contact can take place in the production line or outside the production line or both. The different components of the mixture can be premixed or in contact, or both. As discussed, if necessary or desired, the mixture or any of its components can possibly be removed or separated mechanically, chemically or by means of other methods known to the person skilled in the art, or by a combination of these methods after the hydrate formation conditions are no longer present.

Because the present invention is particularly suitable for lower boiling hydrocarbons or hydrocarbon gases at ambient conditions, the pressure conditions are usually at or greater than atmospheric pressure (ie, about 101 kPa), preferably above about 1 MPa, and more preferably greater than about 5 MPa . The pressure in certain formations or processing plants or units can be much higher, e.g. higher than about 20 MPa. There is no specific high pressure limit. The present method can be used at any pressure that allows the formation of hydrocarbon gas hydrates.

The temperature condition for the contact is usually lower than, the same as, or not much higher than the ambient temperature or the room temperature. Lower temperatures will likely favor hydrate formation so that the treatment with the mixture according to the present invention is necessary. At much higher temperatures, however, hydrocarbon hydrates will be less likely to form so that the need to carry out any treatments is avoided.

The ammonium, phosphonium and sulfonium compound according to the present invention can also be connected through one of the organic side chains, which e.g. represented by -R4, to become a pendant group to many oxygen-containing polymers. Such polymers include, but are not limited to, polyacrylate, polymethacrylate, copolymers of acrylate and methacrylate, polyacrylamide, polymethacrylamide, copolymers of acrylamide and methacrylamide, and polymers and copolymers of N-vinyl caprictam.

The ammonium, phosphonium and sulfonium compound according to the present invention can also be connected through one of the organic side chains, which e.g. represented by -R 4 , to become a pendant group to nitrogen-containing polymers in which the nitrogen is on the polymer backbone. Such nitrogen-containing polymers and copolymers can be obtained by means of the Michael addition reaction between polyethyleneimine and acrylic acid or methacrylic acid. The copolymers may also include N-vinylcaprolactan, N,N-dimethylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide or N-tert-butylacrylamide. The suitable onium compounds can be attached through the acid moiety using suitable diamino or aminoalcohol chemicals followed by the salt forming reactions.

Based on the total weight of the mixture, the concentration of the onium compound in a solvent is preferably in the range of from about 5% by weight to about 75% by weight, preferably from about 10% by weight to about 65% by weight.

In addition to the ammonium, phosphonium and sulfonium compounds, the mixture may also include liquids. These liquids are generally solvents for the original solid form of the compounds. Such solvents include but are not limited to water, simple alcohols such as methanol, ethanol, isopropanol, n-butanol, isobutanol, 2-ethylhexanol; glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and hexylene glycol; ether solvents such as ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dibutyl ether and tetrahydrofuran; ketone solvents such as methyl ethyl ketone, diisobutyl ketone, N-methylpyrrolidone, cyclohexanol; aromatic hydrocarbons such as xylene and toluene; and mixtures thereof. The selection of the appropriate solvent or combination of solvents is important to maintain a stable solution of the compound during storage and to provide stability and reduced viscosity of the inhibitor solutions when injected against a pressure of ~15 to 1750 kg/cm<2>, preferably from 20 wt% to about 95 wt%, more preferably from 50 wt% to about 95 wt% of the total mixture, based on volume.

The compounds of the present invention are added to the mixture of hydrocarbons and water at any concentration effective to inhibit the formation of hydrates under the given conditions. Preferably, the concentration of the active inhibitor compound is about 0.01% by weight and about 5% by weight based on the water content of the mixture. More preferably, the inhibitor compound concentration is between about 0.1% by weight and about 3% by weight.

The present invention can also be used in combination with other agents for hydrate inhibition such as e.g. the use of thermodynamic or kinetic inhibitors discussed in the section on background of the invention. These other hydrate inhibitors can be of the same or a different type of the hydrate inhibitor used in the mixture. If mixtures of hydrate inhibitors are used, the mixture can be added to the process stream containing the hydrocarbon and water through one or more ports. Alternatively, individual hydrate inhibitors can be added at separate ports to the process stream.

The present invention can also be used in combination with other oil field flow securing compounds such as e.g. but not limited to corrosion inhibitors, scale inhibitors, paraffin inhibitors, and asphaltene inhibitors. The hydrate inhibitors can also be used in combination with emulsion breakers or water clarifying agents.

Simple quaternary ammonium and phosphonium compounds

Certain simple quaternary ammonium and phosphonium compounds are suitable for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, by adding to the mixture an effective amount of at least one hydrate inhibitor compound. A preferred family of hydrate inhibitor compounds has the formula:

in which

R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms;

R 2 is selected from straight chain or branched alkyls having from 1 to 4 carbon atoms, preferably exactly 4 carbon atoms. It should be realized that R1 and R2 can be the same or different, as e.g. where R1 and R2 each have exactly 1 carbon atom;

R 3 is an organic unit of 4 or 5 carbon atoms;

R4 is an organic unit with from 2 to 20 carbon atoms. In certain embodiments, R 4 may be selected from alkyl, alkenyl, aryl, arylalkyl, arylalkenyl, alkylaryl, alkenylaryl, glycol, and combinations thereof. Alternatively, R 4 may include one or more heteroatoms selected from oxygen, nitrogen, sulfur and combinations thereof. Even further, R4 can be chemically bound to a polymer. In one embodiment, R 4 is-[(CH 2 -CHR 5 -O)]n-H, wherein R 5 is selected from hydrogen, a methyl group, and an ethyl group, and n is in the range of 1 to 3;

A is a nitrogen atom (N) or a phosphorus atom (P);

X- is anion. E.g. X- can be selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate, and combinations thereof. Suitably, the X anion may be a halide ion selected from bromide, chloride, and combinations thereof.

In a preferred embodiment, said at least one compound is the product of a reaction between an organic halide with one of R1, R2, R3 and R4 and an amine or phosphene with the other three of R1, R2, R3 and R4. E.g. said at least one compound can be the product of the reaction between butyl bromide and an N,N-dimethylalkylamine with between 10 and 20 carbon atoms. Suitably, the N,N-dimethylalkylamine may be N,N-dimethylhexadecylamine.

The method can be carried out at any pressure, such as e.g. between ~7 and 700 kg/cm<2> or even more than ~700 kg/cm<2>.

Independently, the method may include adding at least one amine salt to the mixture along with said at least one compound. E.g. the amine salt may include a cation moiety which is an amine selected from ammonia, dimethylamine, diethylamine, dienpropylamine, trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, ethanolamine, diethylethanolamine, triethanolamine, methylethanolamine, ethylethanolamine, propylethanolamine, methyldiethanolamine, ethyldiethanolamine , dimethylethanolamine, diethanolamine, dibutylethanolamine, dipropylethanolamine, dibutylpropanolamine, dipropylpropanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, dibutylethanolamine, N,N-dibutylcocoamidopropylamine, and combinations thereof. Alternatively, the amine salt may include an anionic moiety which is an acid selected from carboxylic acids and inorganic acids. Such carboxylic acids include, without limitation, formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, malonic acid, succinic acid, acrylic acid, methacrylic acid, trifluoroacetic acid, methanesulfonic acid, and mixtures thereof. Suitable inorganic acids include, without limitation, nitric acid, hydrogen chloride, hydrogen bromide and mixtures thereof.

Consequently, said at least one connection can e.g. include at least one of the following: dimethylbutylhexadecylammonium salt; dimethylbutyloctadecylammonium bromide, dimethylbutyldodecylammonium salt; at least one ammonium salt with an ammonium compound selected from trimethylhexadecylammonium, dimethylethylhexadecylammonium, dimethylbutyloctadecylammonium, dimethylbutylhexadecylammonium, dimethylbutyldodecylammonium, dimethylbutyltetradecylammonium, propyldibutylhexadecylammonium, dipropylbutylhexadecylammonium, and mixtures thereof; or at least one phosphonium salt with a phosphonium compound selected from trimethylhexadecylphosphonium, dimethylethylhexadecylphosphonium, dimethylbutyloctadecylphosphonium, dimethylbutylhexadecylphosphonium, dimethylbutyldodecylphosphonium, dimethylbutyltetradecylphosphonium, propyldibutylhexadecylphosphonium, dipropylbutylhexadecylphosphonium, and mixtures thereof.

The hydrate inhibitor compound is preferably mixed with a solvent, e.g. water, simple alcohols, glycols, ethers, ketone liquids, aromatic hydrocarbons, and combinations thereof. More specifically, preferred solvents include water, methanol, ethanol, isopropanol, n-butanol, isobutanol, 2-ethylhexanol, ethylene glycol, 1,2-propylene glycols, 1,3-propylene glycol, hexylene glycol, ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol dibutyl ether, tetrahydrofuran, methyl ethyl ketone , methyl isobutyl ketone, diisobutyl ketone, N-methylpyrrolidine, cyclohexanone, xylene, toluene and combinations thereof.

Betaine and amine oxides

Other quaternary ammonium and phosphonium compounds, known as betaines and amine oxides, have also been found to be suitable for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, by adding to the mixture an effective amount of at least one hydrate inhibitor compound of the formula :

(R1)(R2)(R3)A<+>-[R4-(C=O)]m-O-

In accordance with the invention, R1, R2, R3 and R4 are organic units, in which R1 is an alkyl with 4 or 5 carbon atoms, in which R2 is hydrogen or an alkyl with from 1 to 4 carbon atoms, and in which R3 has 2 to 20 carbon atoms. Optionally, R3 has an amide functionality. In one embodiment, R3-[(CH2-CH3-O)]n-H, R5 is selected from hydrogen, a methyl group, and an ethyl group, and n is in the range from 1 to 3. R4 is preferably a straight-chain or branched alkyl group, such as e.g. where R4 is selected from -(CH2)n-, -[CH2-(CHR5)n]- and combinations thereof, wherein n is an integer of 1 or greater, and R5 is an alkyl having from 1 to 3 carbon atoms.

A is N or P; and m is an integer 0 or 1.

The method may optionally include the addition of at least one amine salt to the mixture together with said at least one compound. Suitable amine salts include those previously described herein.

Preferred betaines may be derived from an amine and an acid, wherein the amine is selected from dibutylhexadecylamine, dibutyltetradecylamine, dibutyloctadecylamine, dibutyloleylamine, butyldicocoylamine, and mixtures and the acid is selected from chloroacetic acid, acrylic acid, methacrylic acid, and mixtures thereof. Uansett om de er avledet på denne eller en annen måte inkluderer egnede betainer uten begrensning dibutylheksadecylkarboksypropyl, dibutyltetradecylkarboksypropyl, dibutyloktadecyl, karboksypropyl, dibutyloleylkarboksypropyl, dibutyldikokoylkarboksypropyl, dibutylheksadecylkarboksyetyl, dibutyltetradecylkarboksyetyl, dibutyloktadecylkarboksyetyl, dibutyloleylkarboksyetyl, butyldikokoylkarboksyetyl, dibutylheksadecylkarboksymetyl, dibutyltetradecylkarboksymetyl, dibutyloktadecylkarboksymetyl, dibutyloleylkarboksymetyl, butyldikokoylkarboksymetyl og blandinger derav . Suitable amine oxides include, without limitation, butylmethylhexadecylamine, butylmethyltetradecylamine, butylmethyloctadecylamine, butylethylhexadecylamine, butylethyltetradecylamine, butylethyloctadecylamine, dibutylhexadecylamine, dibutyltetradecylamine, dibutyloctadecylamine, dibutyloleylamine, dibutylcocoylamine, butylpropylhexadecylamine, butylpropyltetradecylamine, butylpropyloctadecylamine, butylpropyldeylamine, and butyldicocoylamine.

In one embodiment, R3 is the amide group -[(R5-NH-(C=O)-R6)], R5 is selected from -(CH2)t-, -[CH2-(CHR7)t]-, -(CH2-CHR7O)u -(CH2)t- and combinations thereof, wherein t is an integer from 2 to 4, u is 0 or an integer (1 or greater), R7 is hydrogen or an alkyl having from 1 to 3 carbon atoms, and R6 is an alkyl- or alkenyl group with 4 to 20 carbon atoms. Most preferred is R5-(CH2-CHR7O)u-(CH2)t-.

A preferred method comprises adding to the mixture an effective amount of at least one compound of formula:

(R1)(R2)(R3)A<+>-[R4-(C=O)]m-O-

wherein: A is N or P; R 1 is an alkyl of 4 or 5 carbon atoms; R 2 is hydrogen or an alkyl having from 1 to 4 carbon atoms; R3 is the amide group -[(R5-NH-(C=O)-R6)], wherein R5 is selected from -(CH2)t-, -[CH2-(CHR7)t]-, -(CH2-CHR7O)u-( CH2)t and combinations thereof, wherein t is an integer from 2 to 4, u is 0 or an integer (1 or greater), R7 is hydrogen or an alkyl having from 1 to 3 carbon atoms, and R6 is an alkyl or alkenyl group of 4 to 20 carbon atoms; R4 is selected from -(CH2)n-, -[CH2-(CHR8)n]- and combinations thereof, wherein n is an integer of 1 or greater, and R8 is an alkyl having from 1 to 3 carbon atoms; and m is an integer 0 or 1. In one embodiment of this preferred method, m is equal to 1 and R 4 is -(CH 2 ) n -. When n is an integer 1 or greater, n is preferably an integer from 1 to 10, more preferably from 2 to 4, most preferably 2. R5 is preferably -(CH2-CHR7O)u-(CH2)t-, u is 0 or an integer (1 or greater), R 7 is 1 and t is most preferably 3. In one embodiment, R 1 and R 2 are butyl groups.

Amides

Still further, the method may include adding to the mixture an effective amount of at least one amide compound of the formula:

wherein R 1 , R 2 , R 4 and R 5 are organic moieties; R 1 is an alkyl with 4 or 5 carbon atoms, R 2 is hydrogen or an alkyl with from 1 to 4 carbon atoms; R4 is selected from -(CH2)t-, -[CH2-(CHR6)t]-, -(CH2-CHR6O)u-(CH2)t-, and combinations thereof, wherein t is an integer 2 to 4, u is 0 or an integer (1 or higher) and R 6 is hydrogen or an alkyl having from 1 to 3 carbon atoms; R 5 is an alkyl or alkenyl group of 4 to 20 carbon atoms; A is N or P; X<-> is an anion; and a is 0 or 1. - When a is 0, R3 is selected from [(CH2)(CHR6)b(C=O)]c-O-, -[(CH2CH2)-(SO2)]-O-, [(CH2CH( OH)CH2)-(SO2)]-O-, [(CH2)n-(C=S)]-S<->and combinations thereof, wherein C is 0 or 1, b is 0 or 1, n is 2 or 3, and R 6 is selected from hydrogen and methyl. When a is 1, R 3 is selected from hydrogen, an organic entity having from 1 to 20 carbon atoms and combinations thereof. Preferably, R3 is the same as the group containing amide functionality.

The X anion is preferably selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate, and combinations thereof. Suitable halide ions include without limitation bromide, chloride and combinations thereof.

In one embodiment, R3 is hydrogen, a is 1, and the anion X<-> is selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate, and combinations thereof. In an even further embodiment, said at least one amide compound is the reaction product of an N,N-dialkylaminoalkylamine with an ester or a glyceride. Preferably, the ester or glyceride is derived from a plant source or animal source selected from coconut oil, tallow oil, vegetable oil, and combinations thereof.

The method may further comprise adding said at least one amine salt to the mixture together with said at least one compound. Suitable amine salts include those described hereinbefore. Furthermore, said at least one compound can be mixed with the solvents previously described herein.

In a further embodiment, said at least one compound includes a product prepared by the reaction of an amine selected from (3-dialkylamino)propylamine and (3-dialkylamino)ethylamine with vegetable oil or tallow oil followed by reaction with a reaction component selected from an alkyl halide with from 4 to 20 carbon atoms, hydrogen peroxide, and an acid, wherein the acid is selected from mineral acid, formic acid, acetic acid, chloroacetic acid, propionic acid, acrylic acid, and methacrylic acid, and wherein the dialkyl group in the (3-dialkylamino)propylamine includes two alkyl groups independently selected from methyl, ethyl, propyl, butyl, morpholine, piperidine and combinations thereof.

Amino alcohols and ester-1 compounds

The present invention provides yet another method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water. This method comprises adding to the mixture an effective amount of at least one compound of formula:

wherein: A is N or P; R 1 is a straight-chain or branched alkyl group containing at least 4 carbon atoms; R 2 is hydrogen or an alkyl group containing from 1 to 4 carbon atoms; R 4 is selected from hydrogen, methyl and ethyl; R 5 is either H or an organic unit, e.g. an alkyl chain, containing from 4 to 20 carbon atoms; (X-)a is an anion; a is 0 or 1; n is from 1 to 3; and m is 0 or 1. When a is 0, then R3 is selected from -[(CH2)(CHR6)b(C=O)]c-O-, -[(CH2CH2)-(SO2)]-O-, [(CH2CH (OH)CH2)-(SO2)]-O-, and combinations thereof, wherein C is 0 or 1; b is 0 or 1; and R 6 is selected from hydrogen and a methyl group. When a is 1, then R3 is selected from hydrogen, an organic unit, e.g. an alkyl or alkenyl group, having from 2 to 20 carbon atoms, and combinations thereof. The X anion is preferably selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate, and combinations thereof. The preferred halide ions include without limitation bromide, chloride and combinations thereof.

The method may further comprise the addition of at least one amine salt to the mixture together with said at least one compound. Suitable amine salts include those previously described herein. Furthermore, said at least one compound can be mixed with the solvents previously described herein.

In one embodiment, said at least one compound includes a product of the reaction of N-alkylamine or N,N-dialkylamine with ethylene oxide, propylene oxide or combinations thereof, followed by reaction with at least one alkyl halide having from 1 to 20 carbon atoms.

In a further embodiment, the method comprises the introduction of ester units by transesterification of hydroxy terminals in the alkoxy chains using methyl esters of fatty acids.

Ester-2 compounds

The present invention provides yet another method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water. This method comprises adding to the mixture an effective amount of at least one compound of formula:

wherein: A is N or P; R 1 is an alkyl group containing at least 4 carbon atoms; R 2 is hydrogen or an alkyl group containing from 1 to 4 carbon atoms; R4 is an organic unit, such as e.g. an alkyl, alkenyl or aryl group, containing from 4 to 20 carbon atoms; (X-) is an anion selected from hydroxide, chloride, bromide, sulfate, sulfonate, or carboxylate; and a is 0 or 1. When a is 0, then R3 is selected from -[(CH2)(CHR6)b(C=O)]c-O-, -[(CH2CH2)-(SO2)]-O-, [(CH2CH (OH)CH2)-(SO2)]-O-, and combinations thereof, wherein b is 0 or 1; c is 0 or 1; and R 6 is selected from hydrogen, a methyl group, an ethyl group, and combinations thereof. When a is 1, then R3 is selected from hydrogen, an organic unit, such as e.g. an alkyl or alkenyl group, having from 4 to 20 carbon atoms, and combinations thereof.

In one embodiment, said at least one compound includes a product of Michael addition reaction of alkyl- or N,N-dialkylamine with an acrylate, followed by reaction with at least one organic halide, such as e.g. an alkyl halide, having from 1 to 20 carbon atoms.

R4 is preferably an organic unit, e.g. an alkyl, alkenyl or aryl group, containing from 8 to 20 carbon atoms, preferably from 8 to 16 carbon atoms. Optionally, said at least one compound includes a product from the reaction of a tertiary amine containing the ester unit with chloroacetic acid, acrylic acid or methacrylic acid. In accordance with a similar eventuality, said at least one compound includes a product of reaction between a tertiary amine containing the ester moiety with hydrogen peroxide.

Example 1 - Test procedure for evaluation of hydrate inhibitor compounds The "Rocking Arm" test apparatus used for these evaluations contains "pressure cells" made of sapphire tubes containing a stainless steel ball. The cells are placed in a stand and the stand is carefully tilted back and forth. The cells are filled with liquids before being placed in the rack and then immersed in an insulated tank containing water. As soon as the cells are immersed in the bath, they can then be filled with gas and the experiment started. Sensors are used to monitor the ball movement inside the cells, with a sensor placed near each end of the cell. The bullet drop time is recorded. This data is referred to as "sensor activation time" and they are noted as "sensor 1" and "sensor 2".

In a typical experiment, the cells were filled with ratios of oil to saline ranging from 10:1 to 1:10. A typical ratio of oil to saline solution is about 2:1. The hydrate inhibitors were mixed with the solutions in the cells. The cells were flushed with a synthetic natural gas mixture and then filled with gas to the desired pressure and allowed to equilibrate at the predetermined temperature. The bath was then cooled to a lower predetermined temperature at a specified rate. The following parameters were recorded: (1) bath temperature, (2) individual cell pressure, (3) sensor activation time, and (4) visual observations. Hydrate formation or blockage is indicated by either an increase in sensor activation time ("sensor activation time" - SAT) or visual observation of hydrate particles sticking to the walls. When sensor data is evaluated, the results may indicate: (1) a viscosity increase due to the formation of hydrates, which may also be partly due to oil effects; (2) a partial block; and (3) a complete blockage.

The inhibitor evaluations were carried out using a synthetic natural gas mixture shown in table 1. The composition of the synthetic salt solution (brine) used for the inhibitor evaluations is reproduced in table 2. The typical temperature - pressure profile is shown in fig.1. A list of inhibitor compounds that were evaluated and the results of these evaluations are summarized in Table 3 and Figures 2 through 17. Each of these inhibitor compounds was tested as an inhibitor solution at a 3% by volume dosage rate based on water content. Each inhibitor solution consisted of 40% by weight inhibitor compound and 60% by weight solvent, with the solvent itself being a mixture of half xylene and half n-butanol.

Table 1: Gas mixture

Table 2: Composition of synthetic brine

Table 3: Evaluated inhibitor compounds

The preceding examples are intended to illustrate the performance of the new inhibitors. These examples are not intended and should not be construed to limit their applicability under any other conditions such as pressure, gas composition, amount and type of oil, amount and type of water (salt content). Please also note that the performance ranking of the inhibitors listed here may change or reverse under a different set of conditions.

The terms "comprehensive", "inclusive" and "with" as used in the patent claims and the description herein shall be regarded as indicative of an open group which may include other unspecified elements. The term "mainly consisting of" as used in the patent claims and the description herein shall be considered as indicating a partially open group which may include other elements that are not specified, as long as these other elements do not materially change the basic and novel characteristics of the stated invention . The designation "one", "one" and singular forms of designations shall be understood to include the plural forms of the same words, such as e.g. that the designation indicates that one or more of one or the other is provided. E.g. the term "a solution comprising a phosphorus-containing compound" shall be understood to describe a solution with one or more phosphorus-containing compounds. The terms "at least one" and "one or more" are used interchangeably. The designation "one" or "a single" shall be used to indicate that one and only one of something is intended. In a similar way, other specific whole number values such as "two" are used when a specific number of something is meant. The terms "preferably", "preferred", "prefer", "optionally" and "can" and similar terms are used to indicate that a subject, condition or step to which it is referred is an optional (not necessary) feature of the invention.

The indication of a range of values, such as a statement of a compound with an alkyl of from 6 to 20 carbon atoms shall be further understood to specifically state each and every individual value in between, such as 7, 8, 9... 18, 19. Even further, the statement of lists of alternative components shall, conditions, steps or aspects of the invention are understood to specifically show each and every combination of these options, unless the combination is specifically excluded or mutually exclusive.

It is to be understood from the foregoing description that various modifications and changes may be made in the preferred embodiments of the present invention without departing from its true idea. It is intended that the foregoing description is for illustrative purposes only and should not be construed in a limiting sense. Only the wording of the subsequent patent claims shall limit the scope of the invention.

Claims (27)

PATENT CLAIMS 1. Method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, the method comprising: adding to the mixture an effective amount of at least one compound of formula: in which: R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms; R 2 is selected from straight or branched chain alkyls having from 1 to 4 carbon atoms; R 3 is an organic unit of 4 or 5 carbon atoms; R 4 is an organic unit having from 2 to 20 carbon atoms; A is N or P; and X<->is anion, in which the at least one compound is the product of the reaction between butyl bromide with one of R1, R2, R3 and R4 and N,N-dimethylalkylamine with between 10 and 20 carbon atoms giving the other three of R1, R2, R3 and R4 . 2. Method according to claim 1, in which R2 has exactly 4 carbon atoms. 3. Method according to claim 1, wherein R4 is selected from alkyl, alkenyl, aryl, arylalkyl, arylalkenyl, alkylaryl, alkenylaryl, glycol and combinations thereof. 4. Method according to claim 1, wherein R4 includes one or more heteroatoms selected from oxygen, nitrogen, sulfur and combinations thereof. 5. Process according to claim 1, in which the N,N-dimethylalkylamine is N,N-dimethylhexadecylamine. 6. Method according to claim 1, in which the at least one compound is mixed with a solvent selected from water, simple alcohols, glycols, ethers, ketone liquids, aromatic hydrocarbons, and combinations thereof. 7. Method according to claim 1, in which the at least one compound is mixed with a solvent selected from water, methanol, ethanol, isopropanol, n-butanol, isobutanol, 2-ethylhexanol, ethylene glycol, 1,2-propylene glycols, 1,3-propylene glycol, hexylene glycol, ethylene glycol monobutyl ether (butyl Cellosolve), ethylene glycol dibutyl ether, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, N-methylpyrrolidone, cyclohexanone, xylene, toluene and combinations thereof. 8. Method according to claim 1, which further comprises pumping the mixture through a pipeline at a pressure greater than 700 kg/cm<2> (10000 psi). 9. Method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, the method comprising: adding to the mixture an effective amount of at least one compound of formula: where: R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms; R 2 is selected from straight or branched chain alkyls having from 1 to 4 carbon atoms; R 3 is an organic unit of 4 or 5 carbon atoms; R4 is -[(CH2-CHR5-O)]n-H having from 2 to 20 carbon atoms, wherein R5 is selected from hydrogen, a methyl group, and an ethyl group, and n is in the range from 1 to 3; A is N or P; and X- is anion. 10. Method according to claim 9, in which the anion X- is selected from hydroxide, carboxylate, halide, sulfate, organic sulfonate and combinations thereof. 11. Method according to claim 9, in which the anion X<-> is a halide ion selected from bromide, chloride and combinations thereof, sulphate, organic sulphonate and combinations thereof. 12. Method according to claim 9, in which R1 and R2 are different. 13. Method according to claim 9, wherein said at least one compound is the product of a reaction between an organic halide with one of R1, R2, R3 and R4 and an amine or phosphene with the other three of R1, R2, R3 and R4. 14. A method according to claim 9, which further comprises pumping the mixture through a pipeline at a pressure greater than 700 kg/cm<2> (10000 psi). 15. Method according to claim 9, wherein R1 and R2 each have exactly one carbon atom. 16. Method according to claim 9, which further comprises adding at least one amine salt to the mixture together with said at least one compound. 17. The method according to claim 16, wherein the amine salt includes a cation unit which is an amine selected from ammonia, dimethylamine, diethylamine, di-n-propylamine, trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, ethanolamine, diethylethanolamine, triethanolamine , methylethanolamine, ethylethanolamine, propylethanolamine, methyldiethanolamine, ethyldiethanolamine, dimethylethanolamine, diethanolamine, dibutylethanolamine, dipropylethanolamine, dibutylpropanolamine, dipropylpropanolamine, morpholine, N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, dibutylethanolamine, N,N-dibutylcocoamidopropylamine, and combinations thereof. 18. Method according to claim 16, wherein the amine salt includes an anionic unit which is an acid selected from carboxylic acid, sulphonic acids and inorganic acids. 19. Method according to claim 16, wherein the amine salt includes an anionic unit which is a carboxylic acid selected from formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, malonic acid, succinic acid, acrylic acid, methacrylic acid, trifluoroacetic acid, methanesulfonic acid, and mixtures thereof. 20. Method according to claim 16, wherein the amine salt includes an anionic unit which is an inorganic acid selected from nitric acid, hydrogen chloride, hydrogen bromide, and mixtures thereof. 21. Method according to claim 9, wherein said at least one compound includes at least one ammonium salt with an ammonium compound selected from trimethylhexadecylammonium, dimethylethylhexadecylammonium, dimethylbutyloctadecylammonium, dimethylbutylhexadecylammonium, dimethylbutyldodecylammonium, dimethylbutyltetradecylammonium, propyldibutylhexadecylammonium, dipropylbutylhexadecylammonium, and mixtures thereof. 22. Method according to claim 9, wherein said at least one compound includes at least one phosphonium salt of a phosphonium compound selected from trimethylhexadecylphosphonium, dimethylethylhexadecylphosphonium, dimethylbutyloctadecylphosphonium, dimethylbutylhexadecylphosphonium, dimethylbutyldodecylphosphonium, dimethylbutyltetradecylphosphonium, propyldibutylhexadecylphosphonium, dipropylbutylhexadecylphosphonium, and mixtures thereof. 23. Method according to claim 9, which further comprises pumping the mixture through a pipeline at a pressure between 7 and 700 kg/cm<2>. 24. Method according to claim 9, in which the at least one compound is mixed with a solvent selected from water, methanol, ethanol, isopropanol, n-butanol, isobutanol, 2-ethylhexanol, ethylene glycol, 1,2-propylene glycols, 1,3-propylene glycol, hexylene glycol, ethylene glycol monobutyl ether (butyl Cellosolve), ethylene glycol dibutyl ether, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, N-methylpyrrolidone, cyclohexanone, xylene, toluene and combinations thereof. 25. Method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, the method comprising: adding to the mixture an effective amount of at least one compound of formula: in which: R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms; R 2 is selected from straight or branched chain alkyls having from 1 to 4 carbon atoms; R 3 is an organic unit of 4 or 5 carbon atoms; R 4 is an organic unit having from 2 to 20 carbon atoms; A is N or P; and X<->is anion, wherein the at least one compound includes at least one dimethylbutylhexadecylammonium salt. 26. Method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, the method comprising: adding to the mixture an effective amount of at least one compound of formula: in which: R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms; R 2 is selected from straight or branched chain alkyls having from 1 to 4 carbon atoms; R 3 is an organic unit of 4 or 5 carbon atoms; R 4 is an organic unit having from 2 to 20 carbon atoms; A is N or P; and X- is anion, wherein at least one compound includes dimethylbutyl octadecylammonium bromide. 27. Method for inhibiting the formation of gas hydrate plugs in pipelines containing a mixture of hydrocarbons and water, where the method comprises: adding to the mixture an effective amount of at least one compound of formula: in which: R 1 is selected from hydrogen and straight or branched chain alkyls having from 1 to 3 carbon atoms; R 2 is selected from straight or branched chain alkyls having from 1 to 4 carbon atoms; R 3 is an organic unit of 4 or 5 carbon atoms; R 4 is an organic unit having from 2 to 20 carbon atoms; A is N or P; and X- is anion, wherein the at least one compound includes at least one dimethylbutyldodecylammonium salt.