CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part to United States Patent Application Serial No.

12/245,849, which was filed on October 6, 2008, from which filing priority is hereby claimed and the disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention pertains to one or more compositions and methods for inhibiting the formation of hydrate agglomerates in a fluid, e.g. a fluid in an oil or gas pipeline or refinery.

BACKGROUND OF THE INVENTION

Since Hammerschmidt discovered in 1934 that gas hydrates would block gas pipelines, research for the prevention of hydrate formation and agglomeration has become an important matter. Gas hydrates can be easily formed during the transportation of oil and gas in pipelines when the appropriate conditions are present. Water content, low temperatures, and elevated pressure are required for the formation of gas hydrates. The formation of gas hydrates often results in lost oil production, pipeline damage, and safety hazards to field workers.

There are two approaches to prevent or slowdown the formation of gas hydrates, thermodynamic inhibitors and low dosage hydrate inhibitors (LDHIs). Thermodynamic inhibitors are substances that can reduce the temperature at which the hydrates form at a given pressure and water content. Methanol and ethylene glycol are among the most common thermodynamic inhibitors used in the oil industry. Although thermodynamic inhibitors are quite effective, they require large doses to achieve high concentration in the water phase. Thermodynamic inhibitors are regularly dosed at concentrations as high as 50% based on water content during oil and gas production. Therefore, there is a substantial cost associated with the transportation and storage of large quantities of these solvents. A more cost-effective alternative is the use of LDHIs, as they generally require less than a 2% dose based on water content to inhibit the nucleation or growth of gas hydrates. There are two general types of LDHI, kinetic hydrate inhibitors (KHIs) and anti-agglomerants (AAs/AA). KHIs work by delaying the growth of gas hydrate crystals as anti-nucleators. AAs allow the hydrates to form but they prevent them from agglomerating and subsequent accumulation into larger masses capable of causing plugs in oil and gas pipelines. An AA enables gas hydrates to form but in the shape of a fluid slurry dispersed in the liquid hydrocarbon phase. In general, the water cut should be below 50% because otherwise the slurry becomes too viscous to transport.

There is an ongoing need for new and effective methods of inhibiting the formation of hydrate agglomerates, particularly those that are capable of operating under higher water-cuts.

SUMMARY OF THE INVENTION The invention pertains to compositions, e.g. anti-agglomerants, as well as methods for inhibiting the formation of hydrate agglomerates in a fluid comprising water, gas, and optionally liquid hydrocarbon.

In one aspect, the present invention provides for a composition comprising the following formula and optionally salts thereof:

where Ri is C _n H _2n+ !, wherein n=0 to 12; benzyl; or H; where R ₂ is a C ₄ to C ₂₂ alkyl; where R ₃ is C _n H _2n+1 , wherein n~0 to 12; benzyl; or H; where X ^" is an anion or a sulfate and wherein X ^' is only present when both R ₁ and R ₃ are present; where Y = (CH ₂ ) _n , wherein n is 1 to 8; and wherein R ₃ and R ₁ can not be hydrogen at the same time. hi another aspect, the present invention provides for a method of inhibiting the formation of hydrate agglomerates in a fluid comprising water, gas, and optionally liquid hydrocarbon comprising adding to the fluid an effective anti-agglomerant amount of a composition comprising the following formula:

where Ri is C _n H _21VH , wherein n=0 to 12; benzyl; or H and wherein Ri is linear; where R ₂ is a C ₄ to C ₁₂ alkyl; where R ₃ is C _n H _2n+! , wherein n=0 to 12; benzyl; or H and wherein R ₃ is linear; where X ^" is an anion, halogen, sulfate or a carboxylate and wherein X ^" is only present when both R ₁ and R ₃ are present; where Y = (CH ₂ ) _n , wherein n is 1 to 6; and wherein R ₃ and R ₁ can not be hydrogen at the same time.

DETAILED DESCRIPTION OF THE INVENTION

A. COMPOSITIONS As stated above, the compositions contain a generic formula and optionally salts thereof.

In one embodiment, the compositions contain various amounts of different compositions that fall within the claimed formula.

In another embodiment, the alkyl groups of R] and/or R ₂ are linear, branched, cyclic, and/or unsaturated. In another embodiment, R ₃ is a methyl or ethyl group. In a further embodiment, R ₃ has a linear conformation.

In another embodiment, the halogen is chlorine, bromine, or iodine. The halogen is in ionic form when it is associated with the composition.

In another embodiment, Y = (CH ₂ ) _n , wherein n is 1 to 4, optionally wherein Y is linear or branched.

In another embodiment, Ri is a C ₄ -C ₆ alkyl. In another embodiment, R ₂ is a C ₆ -Ci ₂ alkyl.

In another embodiment, the composition comprises the following formula and optionally salts thereof:

H,C In another embodiment, the composition comprises the following formula:

In another embodiment, the composition comprises the following formula:

Cl ^"

Various synthesis methodologies, which can be appreciated by one of ordinary skill in the art, can be utilized to make the claimed compositions.

In one embodiment, a composition is prepared by reacting an alkyl acrylate with 1- methylpiperazine .

In a further embodiment, the acrylate is a lauryl acrylate.

In another embodiment, the composition contains a quaternary ammonium salt prepared by reacting dodecyl 3-(4-methylpiperazin-l-yl) with an alkyl or a benzyl halide.

The compositions of this invention can contain one or more additional chemistries. Various formulations can be appreciated by one of ordinary skill in the art and can be made without undue experimentation.

In one embodiment, the composition further comprises one or more hydrate inhibitors. In another embodiment, the composition further comprises one or more thermodynamic hydrate inhibitors, one or more kinetic hydrate inhibitors, one or more anti-agglomerants, or a combination thereof.

In another embodiment, the composition further comprises one or more asphaltene inhibitors, paraffin inhibitors, corrosion inhibitors, scale inhibitors, emulsifiers, water clarifiers, dispersants, emulsion breakers, or a combination thereof.

In another embodiment, the composition further comprises one or more polar or nonpolar solvents or a mixture thereof.

In another embodiment, the composition further comprises one or more solvents selected from isopropanol, methanol, ethanol, heavy aromatic naptha, toluene, ethylene glycol, ethylene glycol monobutyl ether (EGMBE), diethylene glycol monoethyl ether, xylene, or a combination thereof.

B. METHODS

As stated above, the present invention provides for a method of inhibiting the formation of hydrate agglomerates in a fluid comprising water, gas, and optionally liquid hydrocarbon comprising adding to the fluid an effective anti-agglomerant amount of a composition comprising the following formula:

where R ₁ is C _n H _2n+1 , wherein n=0 to 12; benzyl; or H and wherein R ₁ is linear; where R ₂ is a C ₄ to C ₁₂ alkyl; where R ₃ is C _n H _2n+ i, wherein n=0 to 12; benzyl; or H and wherein R ₃ is linear; where X ^" is an anion, halogen, sulfate or a carboxylate and wherein X ^" is only present when both R ₁ and R ₃ are present; where Y = (CH ₂ ) _H , wherein n is 1 to 6; and wherein R ₃ and R] can not be hydrogen at the same time.

In one embodiment, the compositions contain various amounts of different compositions that fall within the claimed formula.

In another embodiment, the alkyl groups of R ₂ are linear, branched, cyclic, and/or unsaturated.

In another embodiment, R ₃ is a methyl or ethyl group.

In another embodiment, the halogen is chlorine, bromine, or iodine. The halogen is m ionic form when it is associated with the composition.

In another embodiment, Y = (CH ₂ ) _n , wherein n is 1 to 4, optionally wherein Y is linear or branched.

In another embodiment, R ₁ is a C ₄ -C ₆ alkyl.

In another embodiment, R ₂ is a C ₆ -Ci ₂ alkyl.

In another embodiment, the composition comprises the following formula and optionally salts thereof:

In another embodiment, the composition comprises the following formula:

In another embodiment, the composition comprises the following formula:

CI ^"

The composition is applied to a fluid that contains various levels of salinity.

In one embodiment, the fluid has a salinity of 1% to 20% weight/weight (w/w) total dissolved solids (TDS).

The composition is applied to a fluid that contains various levels of water cut. One of ordinary skill in the art would interpret water cut to mean the % of water in a composition containing an oil and water mixture.

In one embodiment, the water cut is from 1 to 60% volume/volume total dissolved solids.

Various synthesis methodologies, which can be appreciated by one of ordinary skill in the art, can be utilized to make the claimed compositions. These compositions are then utilized in methods of inhibiting the formation of hydrate agglomerates.

In one embodiment, a composition is prepared by reacting an alkyl acrylate with 1- methy lpiperazine .

In a further embodiment, the acrylate is a lauryl acrylate.

In another embodiment, the composition contains a quaternary ammonium salt prepared by reacting dodecyl 3-(4-methylpiperazin-l-yl) with an alkyl or a benzyl halide. The compositions of this invention can contain one or more additional chemistries. Various formulations can be appreciated by one of ordinary skill in the art and can be made without undue experimentation.

In one embodiment, the composition further comprises one or more hydrate inhibitors. In another embodiment, the composition further comprises one or more thermodynamic hydrate inhibitors, one or more kinetic hydrate inhibitors, one or more anti-agglomerants, or a combination thereof.

In another embodiment, the composition further comprises one or more asphaltene inhibitors, paraffin inhibitors, corrosion inhibitors, scale inhibitors, emulsifiers, water clarifiers, dispersants, emulsion breakers, or a combination thereof.

In another embodiment, the composition further comprises one or more polar or nonpolar solvents or a mixture thereof.

In another embodiment, the composition further comprises one or more solvents selected from isopropanol, methanol, ethanol, heavy aromatic naptha, toluene, ethylene glycol, EGMBE, diethylene glycol monoethyl ether, xylene, or a combination thereof.

The fluid in which the compositions and/or formulations are applied to can be contained in many different types of apparatuses, especially those that transport a fluid from one point to another point, e.g. in one embodiment, the fluid is contained in an oil and gas pipeline.

In another embodiment, the fluid is contained in refineries, e.g. separation vessels, dehydration units, gas lines, and pipelines.

The compositions of the present disclosure and/or formulations thereof can be applied to a fluid in various ways that would be appreciated by of ordinary skill in the art. One of ordinary skill in the art would appreciate these techniques and the various locations to which the compositions or chemistries can be applied. In one embodiment, the compositions and/or formulations are pumped into the oil/gas pipeline by using an umbilical line. In a further embodiment, capillary injection systems can be utilized to deliver the surfactants, hi this case anti-agglomerants. U.S. Patent No. 7,311,144 provides a description of an apparatus and methods relating to capillary injection, which is herein incorporated by reference. Various dosage amounts of a composition and/or formulation can be applied to the fluid to inhibit the formation of hydrate agglomerates. One of ordinary skill in the art would be able to calculate the amount of anti-agglomerant for a given situation, e.g. content of fluid could be a factor, without undue experimentation. In one embodiment, the dose range for the hydrate inhibitor that is applied to a fluid, e.g. fluid contained in an oil/gas pipeline, is between 0.1% volume to 2% volume based on water cut.

The methodologies described in the present invention may be utilized with other compositions that are commensurate in scope with this application's disclosure. Other chemistries used for inhibiting the formation of agglomerants in fluids, which are outside the specific generic formula described above, but are commensurate in scope with the claimed compositions generic formula, may be utilized if the system conditions permit the compositions to inhibit the formation of agglomerants (hydrate agglomerates); this protocol can be achieved without undue experimentation, specifically, e.g. the rocking test described below can be utilized in determining whether a chemistry works or not.

EXAMPLES

I. Synthesis of Compositions/ AA chemicals

A, Synthesis of dodecyl 3-f4-methylpiperazin-l-yl)propanoate:

In a 40-mL scintillation vial, 12.Og (0.05 moles) of lauryl acrylate is charged followed by the slow addition of 5,0g (0.05 moles) of 1-methyl piperazine. The mixture is agitated using a magnetic stirrer bar and heated to 85 ⁰ C for at least 16 hours using a heating block. The final product is a light brown liquid at ambient temperature. Complete conversion is apparent from the lack of olefin protons in the ¹ H-NMR spectra. ¹ H-NMR (300 MHz ₅ CDC13): δ 3.83 (t, 6.6Hz,

2H), 2.45 (t, 7.3Hz, 2H), 2.24 (m, 10H), 2.02 (s, 3H) ₅ 1.38 (t, 6.8Hz, 2H), 1.03 (m, 18H), 0.65 (t, 7.1Hz, 3H). ¹³ C-NMR (75MHz, CDC13): δ 171.78, 63.92, 54.64, 53.12, 52.39, 45.53, 31.93,

31.45, 29.19, 21.17, 29.12, 29.08, 28.89, 28.80, 28.20, 25.47, 22.20, 13.63.

Examples 1 to 5 are products of the reaction of commercially available alkyl acrylates with 1-methylpiperazine. The chain length of the hydrophobe portion of the surfactants ranges from butyl to behenyl (C ₂₂ )- Examples 1 to 3 are soluble in methanol while examples 4 and 5 dissolve in ethylene glycol monobutyl ether (EGMBE). Examples 1 to 6 were dissolved to 20% w/w based on active ingredient for the anti-agglomeration test

B, Synthesis of l-butyl-4-(3-( ^' dodecyloxy)-3-oxopropyl ^' )-l-methylpiperazin-l-ium bromide:

In a 100-mL round bottom flask, 5.Og (0.015 moles) of dodecyl 3-(4-methylpiperazin-l- yl)propanoate and 7.3g (0.044 moles) of butyl bromide are combined with 10 mL of isopropyl alcohol. This solution is heated to reflux overnight. Thin layer chromatography (TLC) was used to monitor the progress of the reaction with 1 : 1 methanol/toluene as a mobile phase and iodine to reveal the components on the plate. After the reaction is complete, the solvent and excess of butyl bromide are evaporated under vacuum. Finally, the resulting solid is dried under vacuum at 120 ⁰ C. ¹ H-NMR (300 MHz, CDC13): δ 3.92 (t, 5.9Hz, 2H), 3.76 (m, 2H), 3.56 (m, 4H), 3.35 (s, 3H), 2.91 (m, 6H), 2.46 (t, 6.6Hz, 2H), 1.67 (m, 2H), 1.47 (m, 2H), 1.12 (m, 24H), 0.74 (m, 6H). ¹³ C-NMR (75MHz, CDC13): δ 170.98, 64.61, 59.14, 51.84, 45.88, 31.44, 31.28, 30.81, 29.18, 29.16, 29.13, 29.08, 28.87, 28.81, 28.11, 25.50, 25.43, 22.21, 21.96, 21.60, 13.66, 13.49.

Examples 6 to 12 are the quaternary ammonium salts of dodecyl 3-(4-methylpiperazin-l- yl)propanoate prepared from reactions with alky or benzyl halides. The chain length of the hydrophobe portion of the surfactants ranges from butyl to behenyl (e.g. mixture Of C ₁₈ , C ₂ o and C ₂₂ ). Examples 6 to 8 are soluble in methanol while examples 11 and 12 are dissolved in ethylene glycol monobutyl ether (EGMBE). Example 18 is not soluble enough to make 20% w/w (based on active ingredient) solutions in conventional organic solvents, however, other solvents may be utilized/different conditions may affect the K _sp to allow solubility. All other examples were dissolved to 60% w/w (based on active ingredient) in their respective solvents prior to their anti-agglomeration performance evaluation. "IPA" is isopropyl alcohol.

Examples 21-22 were prepared by reacting 1 -ethyl piperazine with various alkyl acrylates. Specifically, Examples 21-22 are quaternary ammonium salts prepared from the reaction of the tertiary amine and 1 -bromobutane in IPA at a concentration of 80% w/w solids based upon active ingredients. After the reactions are completed, as determined by TLC, the final product is diluted to 60% w/w active ingredient with methanol.

II. Anti-agglomerate (AA) Testing A. Rocking Cell Procedure for Anti-Agglomeration Testing on Magnolia Crude Oil A Rocking cell has two parts, a manifold and a cell body. The manifold is made up of stainless steel fittings that are welded together. It has three stems. An inlet stem is used to charge gas into the cell. An outlet stem is used to release the gas out of the cell. The third stem connects to a transducer, which measures the pressure inside of the cell. The cell body has three layers. The outer layer is a polycarbonate tube, with a thickness that is 0.7 cm. The middle layer is made of a stainless steel metal and is connected to the manifold. The inner layer contains a high-pressure sapphire tube, which has an outer diameter that is 2.8 cm, an inner diameter that is 1.85 cm, and a length that is 5 cm. This sapphire tube can handle up to 3000 psi. A stainless steel ball, which has a 1.6 cm diameter is located inside a sapphire tube to induce turbulence and mix the fluids during the rocking process. The fluid usually contains three different components. For this Anti-Agglomerant test, 7.2 mL of warm magnolia crude oil is first injected into the cell. Next, 4.8 mL of a solution containing 7% by weight based upon actives of NaCl and deionized (DI) water was injected into the cell to make a 40% water cut mixture. AA chemicals are then put into the cell. The dosage of the AA chemical is based on the amount of fluid. The initial condition for the test had a temperature of 21 ⁰ C. Each cell is charged by Green Canyon gas and pressurized up to 2500 psi. The cells were rocked for at least 1.5 to 2 hours until the fluid was saturated and the pressure became stable; then the temperature was set at 4 ⁰ C. The rocking sequence was the following: cells were rocked for 16 hours (simulating steady state flowing); stayed static for 6 hours; and then rocked back for 2 hours. Pressure data was recorded during this time. Observations were taken every two or three hours before the rocking was stopped and right after the start up of the rocking test.

The AAs utilized above were diluted in the appropriate solvent (See LA. and LB.) to a final concentration of 60% actives. The only exception is comparative example B that has a concentration of 40% actives in methanol. The solutions are then dosed to obtain a final concentration of 0.6% vol. of AA (based upon actives) in the fluid. For example, a typical experiment at 40% water cut and a total volume of 12 mL will require 4.8 mL of brine, 7.2 mL of oil, and 29 μL of surfactant solution. The mixture is charged into the Rocking Cell, as described above, and a stainless steel ball is added to promote mixing during the rocking part of the experiment. B. Anti-Agglomeration Results

The primary function of AA chemicals is to disperse hydrate particles in the oil phase while preventing them from coagulating and causing plugs. Since the hydrates are dispersed in the oil phase, as the water cut increases it becomes more difficult to achieve anti-agglomeration performance.

The AAs are diluted in the appropriate solvent (See LA. and LB.) to a final concentration of 60% actives. The only exception is comparative example B that has a concentration of 40% actives in methanol. The solutions are then dosed to obtain a final concentration of 0.6%vol. of AA (based upon actives) in the fluid. For example, a typical experiment at 40% water cut and a total volume of 12 mL will require 4.8 niL of brine, 7.2 mL of oil, and 29 μL of surfactant (AA containing) solution. The mixture is charged into the rocking cell and a stainless steel ball is then added to promote mixing during the rocking part of the experiment. Then, the cells are placed inside a temperature-controlled tank at 21 ⁰ C and pressurized to 2500 psi with methane gas. The temperature of the rocking cell tank is gradually adjusted to 4 ⁰ C while rocking. The cells are rocked for 16 hours (simulating steady-state flowing) followed by a 6-hour shut-in, then 2 more hours of rocking.

The table below shows that the maximum water cuts that each Example or Comparative Example can handle while preventing hydrate plug formation inside the rocking cells. Comparative Example A contains no AA protection and hydrate plugs form at any water cut. Comparative Examples B and C are incumbent products used for AA applications and both of them can handle up to 40% water cut under the testing condition. Examples 1 and 2 demonstrate effectiveness similar to that of Comparative Examples B and C. It is interesting to notice that Examples 1 and 2 contain relatively short hydrophobic groups and that the hydrophilic groups are tertiary amines. Examples 3, 4, 5, and 10 failed the AA test at water cuts as low as 35%. These four Examples present long hydrophobic tails, which may cause limited solubility of the active component in the fluid. Example 6 also failed at 35% water cut but the reason for the poor performance may be attributed to the combination of a short hydrophobic tail and a highly polar quaternary ammonium salt that makes the compound too soluble in the fluid. Examples 7, 8, 11, and 12 demonstrated better AA performance than Comparative Examples B and C. The best overall performance is obtained with Example 8, which can handle up to 60% water cut in the rocking cells. Example 8 shows a significant improvement in water cut tolerance when compared against Comparative Examples B and C. Examples 15, 16, and 20 demonstrate good performance as anti-agglomeration LDHI (See R Rating System Table) at water cuts up to 45- 50%. All other examples were tested at 40% water cut but were not able to prevent the agglomeration of gas hydrates in the rocking cells. The following table lays out when a failure/pass occurs for the experiments. Failures do not necessarily mean an absolute failure because other system conditions may result in a pass for currently failed experiments. LDHI Rating System

Examples 21 and 22 demonstrated anti-agglomeration effects similar to that of Comparative Examples B and C.