INHIBITING HYDROCARBON HYDRATE AGGLOMERATION

Abstract

A process for inhibiting the formation of gas hydrates in a hydrocarbon fluid including adding to the hydrocarbon fluid, a gas hydrate anti-agglomerate which is a biodegradable anti-agglomerant derived from a naturally occurring substance.

Claims

1. A compound comprising at least one non-ionic hydrophilic head group component and at least one lipophilic tail component coupled by at least one linker moiety L, wherein L comprises: (i) a group (chain).sub.b-R*, wherein R* is an amide (NHCO or CONH), an imine (CN or NC), an ester (C(O)O or OC(O)), ether or thioester (C(O)S or SC(O)) linkage between the at least one non-ionic hydrophilic head group component and the at least one lipophilic tail component, wherein b is 0 or 1, and (chain) is an optionally substituted alkyl, an optionally substituted alkenyl or an optionally substituted alkynyl functional group, or (ii) ring system.sup.RS which is a carbocyclic or heterocyclic ring system.sup.RS linking the at least one non-ionic hydrophilic head group component and the at least one lipophilic tail component; and wherein the at least one non-ionic hydrophilic head group component comprises an optionally substituted 5- or 6-membered carbocyclic or heterocyclic ring which is not a difatty ester substituted tetrahydrofuran ring, particularly not a distearate substituted fatty ester tetrahydrofuran ring, and wherein at least one of the lipophilic tail components comprises at least one fatty chain, and wherein the fatty chain is a branched or unbranched C.sub.4-C.sub.20 hydrocarbon chain, a fatty chain derived from a fatty acid, a fatty amine, a fatty ester, a fatty aldehyde, a fatty ether, a fatty nitrile, or a fatty alcohol.

2. A compound according to claim 1, wherein 5- or 6-membered carbocyclic or heterocyclic ring is not a fatty ester derivative of a tetrahydrofuran polyol ring, such that the compound is not an alkyl polyglucoside or a sorbitan fatty acid ester based compound such as sorbitan tristearate or sorbitan mono-oleoate.

3. A compound according to claim 1, having the following general structure: ##STR00153## in which d is 1, 2 or 3, and L represents (i) (chain).sub.b-R*, wherein R* is an amide (NHCO or CONH), an imine (CN or NC), an ester (C(O)O or OC(O)), ether or thioester (C(O)S or SC(O)) linkage between ring.sup.a which is an optionally substituted 5- or 6-membered carbocyclic or heterocyclic ring, and the lipophilic tail component at any one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.7 of ring, wherein b is 0 or 1, and (chain) is an optionally substituted alkyl, an optionally substituted alkenyl or an optionally substituted alkynyl functional group, or (ii) a ring system.sup.RS attached to ring.sup.a as a substituent at any one of R.sup.1, R.sup.1, R.sup.3, R.sup.4, R.sup.5, and R.sup.7, and linking ring.sup.a to the lipophilic tail, or a ring system.sup.RS directly fused to ring.sup.a at any adjacent pair of R.sup.1 and R.sup.2, R.sup.2 and R.sup.3, R.sup.3 and R.sup.4, R.sup.4 and R.sup.5, R.sup.5 and R.sup.7 or R.sup.7 and R.sup.1, wherein the ring system.sup.RS is an aromatic or aliphatic carbocyclic or heterocyclic ring system which may be saturated or unsaturated and which may be optionally substituted; and wherein each of A, Y, Z of ring.sup.a is independently CH, C, N, O, or S, and each instance of R.sup.1, R.sup.2, R.sup.3 is independently a lone pair or R.sup.6, provided that when A, Y and Z are independently O or S, the corresponding R.sup.1, R.sup.2 or R.sup.3 is a lone pair, X is CH, C, or N, and wherein when c is 0, Y is absent, or when c is 1, Y is present, provided that ring.sup.a is not a difatty ester substituted tetrahydrofuran ring, particularly not a distearate substituted fatty ester tetrahydrofuran ring; each instance of R.sup.4, R.sup.5, R.sup.6, and R.sup.7 when not L, is independently selected from hydrogen, halogen, hydroxyl, ether, alkyl hydroxyl, alkyl ether, oxo, thio, carboxylic acid, carboxylic acid ester, carboxylic acid alkyl ester, alkyl carboxylic acid, alkyl carboxylic acid ester, amine, alkyl amine, sulfonic acid, alkyl sulfonic acid, alkyl, aldehyde, ketone, dicarboxyl including oxalate, malonate, succinate, glutarate, adipate, ester, alkyl ester, diester, dicarboxylate ester, guanidine, alkyl guanidine, imine, alkyl imine, imide, alkyl imide, sulfonic acid, sulfhydryl, sulfonyl, sulfinyl, sulfenyl, phosphoryl, diphosphoryl, thioester, alkyl thioester, a 5- or 6-membered carbocyclic or heterocyclic ring, any of which may be optionally substituted where structurally possible; or when not L, each of R.sup.1 and R.sup.2, R.sup.2 and R.sup.3, R.sup.3 and R.sup.4, and R.sup.4 and R.sup.5, when taken together independently form a 5- or 6-membered aromatic carbocyclic, aromatic heterocyclic ring, aliphatic carbocyclic or aliphatic heterocyclic ring which can be optionally substituted; wherein the optional substituents are independently selected from with one or more of H, C.sub.1-C.sub.6 alkyl, acyl, carboxylic acid, carboxylate ester, alkyl carboxylic acid, alkyl carboxylate ester, hydroxyl, alkyl hydroxyl, sulfonic acid, amine, amide or halogen; and wherein the at least one lipophilic tail component comprises at least one fatty chain.

4. A compound according to claim 3, wherein d is 1 or 2, preferably having one of the following general structures: ##STR00154##

5. A compound according to claim 3, wherein the alkyl hydroxyl is (CH.sub.2).sub.nOH, where n is from 1 to 10, the carboxylic acid alkyl ester is C(O)O(CH.sub.2).sub.nH, n is from 1 to 10, and the alkyl carboxylic acid is (CH.sub.2).sub.nC(O)OH, wherein n is from 1 to 10.

6. A compound according to claim 1, the optionally substituted 5- or 6-membered carbocyclic or heterocyclic ring (ring.sup.a) comprises a phenyl; a benzoic acid or alkyl esters thereof; an alkylbenzoic acid; an aromatic dicarboxylic acid; an aromatic dicarboxylic acid alkyl ester thereof; morpholinyl; tetrahydrofuranyl; oxopyrrolidnyl; pyrrolidnyl; piperidinyl; furanyl; imidazoyl; pyridinyl; pyrrolyl; benzodioxole; naphthyl; naphthoic acid; pyrrolylphenyl; or phenylsulfonic acid or esters thereof.

7. A compound according to claim 1, wherein R* is NHC(O), C(O)O, O, C(O)S, or NCH.

8. A compound according to claim 1, comprising one of the following general formulas: ##STR00155## wherein the fused ring system.sup.RS has 2 to 10 fused 4, 5 or 6-membered rings.

9. A compound according to claim 1, comprising a ring structure selected from the group consisting of: ##STR00156##

10. A compound according to claim 1, having the following general structure: ##STR00157## wherein when c is 0, Y is absent, or when c is 1, Y is present, and each of A, Y, Z of ring.sup.a is independently CH, C, N, O, or S, and each instance of R.sup.1, R.sup.2, R.sup.3 is independently a lone pair or R.sup.6, provided that when A, Y and Z are independently O or S, the corresponding R.sup.1, R.sup.2 or R.sup.3 is a lone pair, X is CH, C, or N, and each instance of R.sup.6, and R.sup.7 is independently selected from hydrogen, halogen, hydroxyl, ether, alkyl hydroxyl, alkyl ether, oxo, thio, carboxylic acid, carboxylic acid ester, alkyl carboxylic acid, alkyl carboxylic acid ester, amine, alkyl amine, sulfonic acid, alkyl sulfonic acid, alkyl, aldehyde, ketone, dicarboxyl including oxalate, malonate, succinate, glutarate, adipate, ester, alkyl ester, diester, dicarboxylate ester, guanidine, alkyl guanidine, imine, alkyl imine, imide, alkyl imide, sulfhydryl, sulfonyl, sulfinyl, sulfenyl, phosphoryl, diphosphoryl, thioester, alkyl thioester, a 5- or 6-membered carbocyclic or heterocyclic ring, any of which may be optionally substituted where structurally possible; and wherein the optional substituents are independently selected from with one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, amine, amide or halogen, and wherein the fatty chain is a branched or unbranched C.sub.4-C.sub.20 hydrocarbon chain, a fatty chain derived from a fatty acid, a fatty amine, a fatty ester, a fatty aldehyde, a fatty ether, a fatty nitrile, or a fatty alcohol.

11. A compound according to claim 1 having the following general structure: ##STR00158## wherein ring.sup.a and/or ring.sup.b is saturated or unsaturated; when c is 0, Y is absent, or when c is 1, Y is present, and each of A, Y, Z of ring.sup.a is independently C, C, N, O, or S, and each instance of R.sup.1, R.sup.2, R.sup.3 is independently a lone pair or R.sup.6, provided that when A, Y and Z are independently O or S, the corresponding R.sup.1, R.sup.2 or R.sup.3 is a lone pair, X is CH, C, or N, and each instance of R.sup.6, and R.sup.7 is independently selected from hydrogen, halogen, hydroxyl, ether, alkyl hydroxyl, alkyl ether, oxo, thio, carboxylic acid, carboxylic acid ester, alkyl carboxylic acid, alkyl carboxylic acid ester, amine, alkyl amine, sulfonic acid, alkyl sulfonic acid, alkyl, aldehyde, ketone, dicarboxyl including oxalate, malonate, succinate, glutarate, adipate, ester, alkyl ester, diester, dicarboxylate ester, guanidine, alkyl guanidine, imine, alkyl imine, imide, alkyl imide, sulfhydryl, sulfonyl, sulfinyl, sulfenyl, phosphoryl, diphosphoryl, thioester, alkyl thioester, a 5- or 6-membered carbocyclic or heterocyclic ring, any of which may be optionally substituted where structurally possible; or each of R.sup.1 and R.sup.2, R.sup.2 and R.sup.3, R.sup.3 and R.sup.4, and R.sup.4 and R.sup.5, when taken together independently form a 5- or 6-membered aromatic carbocyclic, aromatic heterocyclic ring, aliphatic carbocyclic or aliphatic heterocyclic ring which can be optionally substituted; and wherein the optional substituents are independently selected from with one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, amine, amide or halogen, and wherein the fatty chain is a branched or unbranched C.sub.4-C.sub.20 hydrocarbon chain, a fatty chain derived from a fatty acid, a fatty amine, a fatty ester, a fatty aldehyde, a fatty ether, a fatty nitrile, or a fatty alcohol.

12. A compound according to claim 1, wherein the at least one at least one lipophilic tail component is a C.sub.8, C.sub.9, C.sub.10, C.sub.11, C.sub.12, C.sub.13 and C.sub.16 fatty chains.

13. A compound according to claim 11, having the following general structure: ##STR00159## wherein L* is (CH.sub.2).sub.n alkyl linker and n is 1, 2, 3 or 4, and R.sup.8 is H; and Y is an optionally substituted branched C.sub.7-C.sub.10 alkyl, or an optionally substituted branched C.sub.7-C.sub.10 alkenyl.

14. A compound selected from the group consisting of: ##STR00160## ##STR00161## ##STR00162## ##STR00163## ##STR00164## ##STR00165##

15. (canceled)

16. A compound according to claim 1, which is biodegradable meaning it produces a score of >20% biodegradability over 28 days as assessed by OECD 306: Biodegradability in Seawater, the Closed Bottle Test; has an ecotoxicity of LC50/EC50 of greater than 10 mg/L as determined by OECD 203: Fish, Acute Toxicity Test; and/or has a bio-concentration factor (BCF) larger than 100 or Log P.sub.ow3 as determined by OECD 305: Bioaccumulation in Fish: Aqueous and Dietary Exposure.

17-28. (canceled)

29. A process for inhibiting gas hydrate agglomeration in a hydrocarbon phase comprising the steps of: (i) providing at least one oil soluble anti-agglomerant compound as defined in claim 1; (ii) generating repulsive forces between gas hydrates in the hydrocarbon phase by contacting the gas hydrates with the at least one anti-agglomerant to form a plurality of dispersed gas hydrate-anti-agglomerant anti-agglomerant associated particles.

30. A process according to claim 16 involving inhibiting the formation of gas hydrate blockages in a hydrocarbon well, pipeline and/or conduit carrying a hydrocarbon phase, the process comprising the steps of: preventing a gas hydrate of blockage size forming in the hydrocarbon phase by maintaining a dispersion of gas hydrate crystals formed in the hydrocarbon phase by contacting the gas hydrate crystals with at least one oil soluble anti-agglomerant compound as defined in claim 1, thereby forming a plurality of associated gas crystal-anti-agglomerant particles, whereby repulsive forces between the associated gas crystal-anti-agglomerant particles prevent agglomeration of the gas hydrate crystals into a solid blockage size plug.

31. A process according to claim 16 involving for inhibiting gas hydrate agglomeration in a slurry in a transport line comprising a water-in-hydrocarbon phase having a plurality of water droplets dispersed in a continuous hydrocarbon phase, said method comprising the steps of: (i) providing at least one oil soluble anti-agglomerant compound as defined in claim 1, to the water-in-hydrocarbon dispersion in the transport line; (ii) allowing the anti-agglomerant to associate with gas hydrates formed at an interface of the water-hydrocarbon phase to form a slurry comprising a dispersion of gas hydrate-anti-agglomerant associated particles in the hydrocarbon continuous phase, whereby repulsive forces between the gas hydrate-anti-agglomerant associated particles and/or attractive forces between the gas hydrate-anti-agglomerant associated particles and the hydrocarbon continuous phase of the slurry maintain the gas hydrate-anti-agglomerant associated particles in substantially dispersed form.

32-36. (canceled)

32. A compound according to claim 6, the optionally substituted 5- or 6-membered carbocyclic or heterocyclic ring (ringa) comprises a benzoic acid ester; an alkylbenzoic acid; an aromatic dicarboxylic acid; or an aromatic dicarboxylic acid alkyl ester thereof; morpholinyl; tetrahydrofuranyl; oxopyrrolidnyl; pyrrolidnyl; piperidinyl; furanyl; imidazoyl; pyridinyl; pyrrolyl; benzodioxole; naphthyl; naphthoic acid; pyrrolylphenyl; or phenylsulfonic acid or esters thereof.

33. A compound according to claim 32, the optionally substituted 5- or 6-membered carbocyclic or heterocyclic ring (ringa) comprises methylbenzoate, ethyl benzoate, phenylacetic acid, phenylethanoic acid, phenylpropanoic acid, phenylbutanoic acid, phenylmethanoate, phenylethanoate, phenylpropanoate, phenylbutanoate; phthalic acid, terephthalic acid, isophthalic acid; methylphthalate, dimethylterephthalate, or dimethylisophthalate; morpholinyl; tetrahydrofuranyl; oxopyrrolidnyl; pyrrolidnyl; piperidinyl; furanyl; imidazoyl; pyridinyl; pyrrolyl; benzodioxole; naphthyl; naphthoic acid; pyrrolylphenyl; or phenylsulfonic acid or esters thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0508] In the attached drawings:

[0509] FIG. 1 illustrates the chemical structures of a number of commercially available tocopherol samples;

[0510] FIG. 2 illustrates the chemical structure of one green anti-agglomerant, tocopherol succinate, of the invention (anti-agglomerant1) and chemical structure of a conventional anti-agglomerant, dodecyltrimethylammonium bromide;

[0511] FIG. 3 illustrates a comparison by overlay of the change in hydrate volume fraction over time in each of the pure water, anti-agglomerant and commercial AA systems averaged over 10 runs;

[0512] FIG. 4 illustrates an overlay of a representative cycle of the hydrate fraction against relative torque for each of the pure water, anti-agglomerant and commercial AA systems;

[0513] FIG. 5(a) illustrates a representative plot of hydrate growth rate in pure water (system 1) for one experimental cycle in which the hydrate volume fraction is plotted as a function of time; FIG. 5(b) illustrates the average hydrate growth rate for each stage of the experiment run in pure water, whereby the representative rate is represented by a triangle symbol:

[0514] FIG. 6 illustrates the hydrate formation kinetic data collected in pure water (system 1) over the 10 experiments carried out, as well as the calculated average data for all experiments;

[0515] FIG. 7 illustrates the hydrate characteristics of gas consumption, hydrate volume fraction and water conversion for each experiment in pure water (system 1);

[0516] FIG. 8 illustrates the hydrate growth rate per stage for each experiment in pure water (system 1), as well as the calculated average for all experiments;

[0517] FIG. 9 illustrates a representative plot of hydrate growth rate in water and anti-agglomerant (system 2) for one experimental cycle in which the hydrate volume fraction is plotted as a function of time;

[0518] FIG. 9(b) illustrates the average hydrate growth rate for each stage of the experiment run in water and anti-agglomerant (system 2), whereby the representative rate is represented by a triangle symbol:

[0519] FIG. 10 illustrates the hydrate formation kinetic data collected in water and anti-agglomerant (system 2) over the 10 experiments carried out, as well as the calculated average data for all experiments;

[0520] FIG. 11 illustrates the hydrate characteristics of gas consumption, hydrate volume fraction and water conversion for each experiment in water and anti-agglomerant (system 2);

[0521] FIG. 12 illustrates the hydrate growth rate per stage for each experiment in water and anti-agglomerant (system 2) as well as the calculated average for all experiments;

[0522] FIG. 13 illustrates a representative plot of hydrate growth rate in water and conventional AA (system 3) for one experimental cycle in which the hydrate volume fraction is plotted as a function of time;

[0523] FIG. 13(b) illustrates the average hydrate growth rate for each stage of the experiment run in water and conventional AA (system 3), whereby the representative rate is represented by a triangle symbol;

[0524] FIG. 14 illustrates the hydrate formation kinetic data collected in water and conventional AA (system 3)) over the 10 experiments carried out, as well as the calculated average data for all experiments;

[0525] FIG. 15 illustrates the hydrate characteristics of gas consumption, hydrate volume fraction and water conversion for each experiment in water and conventional AA (system 3);

[0526] FIG. 16 illustrates the hydrate growth rate per stage for each experiment in water and anti-agglomerant (system 3) as well as the calculated average for all experiments;

[0527] FIG. 17(a) illustrates the X-ray diffraction pattern of the gas hydrates formed in systems 1-3. FIG. 17(b) represents an overlay of the respective X-ray diffraction patterns of FIG. 17(a) demonstrating the similarly in gas hydrate structure formed in each of system 1-3;

[0528] FIG. 18 illustrates the X-ray diffraction peaks identifying the presence of the solid decane phase, the SI and SII hydrate phases and small levels of hexagonal ice phase in the hydrates formed in system 1;

[0529] FIG. 19 illustrates the X-ray diffraction peaks identifying the presence of the solid decane phase, the SI and SII hydrate phases in the hydrates formed in system 2; and

[0530] FIG. 20 illustrates the X-ray diffraction peaks identifying the presence of the solid decane phase, the SI and SII hydrate phases in the hydrates formed in system 2.

DETAILED DESCRIPTION OF THE INVENTION

[0531] The invention will now be described with reference to the following examples. It is to be understood that the examples are provided by way of illustration of the invention and that they are in no way limiting to the scope of the invention.

Examples

[0532] The following anti-agglomerants have been synthesised and characterised:

##STR00146##

Exemplary Synthesis Involving Amine and Fatty Carboxyl Coupling

[0533] Alkanoic acid (1 molar equivalence) was dissolved into anhydrous ethyl acetate under inert atmosphere at room temperature. N,N-carbonyl diimidazole (CDI) (1 molar equivalence) was added to the alkanoic acid and stirred for 1-2 hours. Then the amine (1.1-1.2 molar equivalence) was added and the reaction was heated to 80 C., under reflux. The reaction was allowed to react for 24 hours at 80 C. before cooling to room temperature. Work-up involved washing the reaction mixture with 1M hydrochloric acid (50 mL, 3 times), 1M sodium hydrogen carbonate (50 mL, twice) and finally saturated sodium chloride. Ethyl acetate was taken off under vacuum to afford the purified product.

Gas Hydrate Testing

[0534] A high pressure autoclave equipped with a magnetic stirrer coupling was used to study hydrate formation. This provides information regarding the hydrate onset time, growth rate, and hydrate fraction by measuring pressure, temperature, and torque changes during hydrate formation. A synthetic natural gas mixture was used in all of the experiments according to Table 3.

TABLE-US-00002 TABLE 3 Composition of synthetic natural gas Components Composition (mol %) CH.sub.4 90 C.sub.2H.sub.6 6 C.sub.3H.sub.8 3 n-C.sub.4H.sub.10 1

[0535] Decane is added to the test as a continuous phase, the gas mixture does not contain a liquid condensate.

Conditions

[0536] Total liquid of 80 ml (0.5 wt % tocopherol AA and commercial AA solution), and pure water in 360 ml internal volume autoclave under watercut 30 environment [0537] 120 bar natural gas saturation (methane: 90 mol %, ethane: 6 mol %, propane: 3 mol %, n-butane: 1 mol %) at 24 C., with 600 rpm stirring [0538] Cooling rate: 0.25 Kmin.sup.1 (24.fwdarw.4 C.), 4 C., for 10 hrs followed by 28 OC dissociation due to elimination of residual hydrate structure [0539] Total 10 cycles hydrate formation and dissociation

[0540] The initial testing involved use of commercially available tocopherol moieties as lipophilic portion of the anti-agglomerant molecules of the invention. The commercially available tocopherol products are shown in FIG. 1.

[0541] The experiments compare hydration formation and agglomeration in three systems comprising pure water (system 1), anti-agglomerant, tocopherol succinate (system 2), and commercial AA, dodecytrimethylammonium bromide DTAB (system 3).

[0542] The structures of the comparative AAs used are shown in FIG. 2.

Experimental Method

[0543] For each system considered, a total liquid volume of 80 mL of 0.5 wt % anti-agglomerant (system 2) or 0.5 wt % of commercial DTAB AA solution (system 3) or pure water (system 1) was loaded into the autoclave cell which had an internal volume of 360 mL under a watercut 30 environment. The cell was immersed in a temperature-controlled liquid bath connected to an external refrigerated heater. A platinum resistance thermometer monitored the temperature of the liquid phase inside of the autoclave with an uncertainty of 0.15 C. The pressure was measured by a pressure transducer with an uncertainty of 0.1 bar in a range of 0-200 bar. Temperature and pressure were recorded using a data acquisition system.

[0544] The experiment was commenced by loading the 80 ml of liquid phase into the autoclave cell.

[0545] After purging the cell three times with the natural gas, the autoclave was pressurized to 120 bar at 24 C., while stirring at 600 rpm to saturate the liquid phase with gas. Once the pressure and temperature reached steady-state, the cell was cooled to 4 C., within 2 hours (0.25 Kmin.sup.1) and kept for 10 hours at the temperature. During this time, torque, pressure and temperature were continuously monitored. The dissociation of hydrate was carried out at 28 C., for a sufficient time to remove the residual hydrate structures prior to the next run.

[0546] Ten experiments were carried out for each system to determine averages for the hydrate formation including hydrate growth rate, hydrate formation kinetics, hydrate characterisation and dissociation onset time, and hydrate volume fraction.

Results

[0547] The anti-agglomerant, tocopherol succinate, showed a degree of kinetic hydrate inhibition ability based on the increased hydrate formation onset time and subcooling of the temperature of the pure water system 1 (pure water: 7.01K, 33.42 min.fwdarw.anti-agglomerant: 8.19 K, 54.27 min).

[0548] In contrast, from the kinetics perspective, the commercial AA (DTAB) resulted in the slight promotion of hydrate formation in terms of time and temperature (pure water: 7.01K, 33.42 min.fwdarw.DTAB: 5.9 K, 29.10 min). Furthermore, the results indicate that systems 2 and 3 containing anti-agglomerant and conventional AA respectively, both overall resulted in a less conversion of water to hydrate than which occurred in the pure water system 1. In addition, both systems 2 and 3 comprising AA showed a similar conversion ratio (pure water: 77.36%, DTAB: 73.79%, and Anti-agglomerant: 73.35%).

[0549] During hydrate formation in the pure water system 1, the torque rapidly increased in the range of 0.5-0.15 hydrate volume fraction (.sub.rel,max: 1.74). This observation is consistent with the rapid rate of growth rate in the second to third stage of the hydrate growth rate curve. As a result of this phenomenon, the resistance to flow in the system suddenly increases as indicated by the sudden torque increase observed.

[0550] For the DTAB system 3, the maximum torque (.sub.rel,max: 1.32) was recorded between 0.15 and 0.25 hydrate volume fraction. Like DTAB, the Anti-agglomerant showed a similar trend (.sub.rel,max: 1.18).

[0551] With regard to growth rate, the hydrate volume fraction was mainly observed in the second stage showing the highest average growth rate.

[0552] For the commercial AA (system 3) and the anti-agglomerant (system 2), the growth rate trend showed a similar pattern showing the highest value seen in the second stage followed by a decreased rate. Unlike the AA systems, the growth rate stagnated in the pure water system due to mass transfer limitations. Rapid growth rate in the next step is cause by for the reason. The rapid torque increase is evidenced by the rapid growth rate with concern of hydrate fraction.

[0553] Preferably, the anti-agglomerant is a hydratephillic type AA and is not emulsifying which is likely to explain why no emulsion forms. This is indicative of demonstrating that the hydrophilic head group of anti-agglomerant is interacting with the gas hydrate. This behaviour is in line with that of DTAB in system 3. In contrast to the anti-agglomerants described herein, the commercial AAs are charged making them sensitive to ions present and insoluble in the continuous phase.

[0554] As the anti-agglomerant is a vitamin-E based anti-agglomerant it is less toxic to the environment in comparison with quaternary ammonium AA such as DTAB.

[0555] The diffraction studies indicate that regardless of the nature of the AA used the XRD pattern of the solids formed are very similar indicating essentially the same hydrate mixtures are formed in each of systems 1-3. In short, there is a combination of structure I and structure II hydrate formed in all three systems considered. It is clear therefore that the presence of the anti-agglomerant does not alter the structure of the hydrate formed.

[0556] The corrosion inhibition of tocopherol carbon steel was tested in an aqueous corrosion fluid. The weight-loss measurement was conducted in open vials. The solutions used were 2M HCl with or without 500 ppm polymers (Blank). The carbon steel samples were cut into 131 mm dimensions and were washed and degreased by ethanol after polish. They were then rinsed and dried with distilled water. These coupons with freshly prepared surface were then immersed in the HCl/polymers solutions for 120 h. At specific time intervals, the coupons were withdrawn from the solutions and weighted after being rinsed by ethanol and pure water. The immersion tests were totally repeated 5 times to acquire relatively accuracy data. The experiment compares the measure of weight loss during the exposure period. Where more corrosion occurs, a higher weight loss of the starting sample is observed. The data shows that (+) alpha-tocopherol (2.88% loss) and racemic alpha tocopherol (2.69% loss) has some corrosion inhibition ability compared to the blank sample (3.4% loss). As this method is aqueous-based, oil soluble inhibitors are expected to perform better.

CLAUSES

[0557] 1. A process for inhibiting gas hydrate agglomeration in a hydrocarbon phase, preferably natural gas, comprising the steps of: [0558] (i) providing at least one oil soluble anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group; [0559] (ii) generating repulsive forces between gas hydrates in the hydrocarbon phase by contacting the gas hydrates with the at least one anti-agglomerant to form a plurality of dispersed gas hydrate-anti-agglomerant anti-agglomerant associated particles. [0560] 2. A process for inhibiting gas hydrate crystal agglomeration in a hydrocarbon phase, wherein under gas hydrate crystal formation conditions, one or more of the hydrocarbons are trapped within structures formed from water molecules present with the one or more hydrocarbons, said method comprising the steps of: [0561] (i) providing at least one oil soluble anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group; [0562] (ii) contacting the gas hydrate crystals during or after their formation with the at least one anti-agglomerant whereby the hydrophilic head groups of the at least one anti-agglomerant associates with the water molecules of the gas hydrate crystals to form a plurality of associated gas crystal-anti-agglomerant particles whereby repulsive forces between the lipophilic tail groups of the associated gas crystal-anti-agglomerant particle formed prevent agglomeration of the gas hydrate crystals into gas hydrate clusters. [0563] 3. A process of inhibiting the formation of gas hydrate blockages in a hydrocarbon well, pipeline and/or conduit carrying a hydrocarbon phase, the process comprising the steps of: [0564] preventing a gas hydrate of blockage size forming in the hydrocarbon phase by maintaining a dispersion of gas hydrate crystals formed in the hydrocarbon phase by contacting the gas hydrate crystals with at least one oil soluble anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group thereby forming a plurality of associated gas crystal-anti-agglomerant particles, [0565] whereby repulsive forces between the associated gas crystal-anti-agglomerant particles prevent agglomeration of the gas hydrate crystals into a solid blockage size plug. [0566] 4. A process according to any one of the preceding clauses, whereby the degree of lipophilicity and hydrophilicity of the respective lipophilic and hydrophilicity is sufficiently balanced to provide an oil soluble anti-agglomerant that is capable of associating with hydrates such that the resultant forces between the gas hydrate-anti-agglomerant associated particles maintain the gas hydrate-anti-agglomerant associated particles in substantially dispersed form in the hydrocarbon phase. [0567] 5. A process according to any one of the preceding clauses, wherein the repulsive forces between the gas hydrate-anti-agglomerant associated particles prevents agglomeration of the particles into larger gas hydrate clusters of a size that forms a solid hydrate pipeline or conduit blockage. [0568] 6. A process according to any one of the preceding clauses, wherein the hydrocarbon phase is a water-in-hydrocarbon dispersion. [0569] 7. A process according to any one of the preceding clauses, wherein the hydrocarbon phase is transported through a line, for example, a well, flowline, pipe or conduit. [0570] 8. A process for inhibiting gas hydrate agglomeration in a slurry in a transport line comprising a water-in-hydrocarbon phase having a plurality of water droplets dispersed in a continuous hydrocarbon phase, said method comprising the steps of: [0571] (i) providing at least one oil soluble anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group, to the water-in-hydrocarbon dispersion in the transport line; [0572] (ii) allowing the anti-agglomerant to associate with gas hydrates formed at an interface of the water-hydrocarbon phase to form a slurry comprising a dispersion of gas hydrate-anti-agglomerant associated particles in the hydrocarbon continuous phase, [0573] whereby repulsive forces between the gas hydrate-anti-agglomerant associated particles and/or attractive forces between the gas hydrate-anti-agglomerant associated particles and the hydrocarbon continuous phase of the slurry maintain the gas hydrate-anti-agglomerant associated particles in substantially dispersed form. [0574] 9. A process according to any one of the preceding clauses wherein the dispersion has a relative viscosity lower than that of slurry comprising equivalent particles formed under the same conditions in the absence of the oil soluble anti-agglomerant. [0575] 10. A process according to any one of the proceeding clauses, wherein the hydrocarbon phase has an associated watercut of from 1 to 100%, more preferably from 5 to 60%, and most preferably from 10 to 50%. [0576] 11. A process according to any one of the proceeding clauses, further comprising the step of monitoring the risk of plugging or blockage by the observation of one or more of: a decrease in flow rate, a pressure drop along a flowline, an increase in the hydrate volume fraction in the line, and an increase in the hydrate/hydrocarbon slurry relative viscosity, whereby observation of one or more of pressure drop, hydrate volume fraction and relative viscosity indicates that anti-agglomerant is required in the hydrocarbon phase, for example, wherein anti-agglomerant is added such that P.sub.flowline is maintained at a value <300 psi, .sub.hyd is maintained at a value <0.10, whereby .sub.hyd is the hydrate volume fraction in the line, and/or .sub.r is maintained at a value <10, whereby .sub.r is the hydrate slurry relative viscosity, a decrease in flow rate of a 20%. [0577] 12. A process according to any one of the proceeding clauses, wherein the preferred anti-agglomerant does not generate an oil-in-water emulsion. [0578] 13. A process according to any one of the proceeding clauses, wherein the non-ionic hydrophilic head group s derived from a natural source or is a naturally occurring product, a precursor to, a metabolite or a derivative thereof, preferably, the anti-agglomerant is environmentally benign, biodegradable, and/or non-toxic to plants, animals, marine life and/or insects. [0579] 14. A process according to any one of the proceeding clauses, wherein the anti-agglomerant is derived from a lipid that is derived from ketoacyl or isoprene precursors or building blocks, for example, a nonsaponifiable lipid, preferably selected from the group consisting of: a fat soluble vitamin, fat soluble terpene and a fat soluble steroid, fat soluble derivatives, fat soluble precursors, or fat soluble metabolite thereof. [0580] 15. A process according to any one of the proceeding clauses, wherein the anti-agglomerant comprises at least one lipophilic tail being a lipid that is derived from ketoacyl or isoprene precursors or building blocks, for example, a nonsaponifiable lipid, preferably selected from the group consisting of: a fat soluble vitamin, fat soluble terpene and a fat soluble steroid, fat soluble derivatives, fat soluble precursors, or fat soluble metabolite thereof. [0581] 16. A process according to any one of the proceeding clause, wherein the biodegradable naturally occurring product is an oil soluble substance selected from the group of naturally occurring lipids consisting of: Fatty Acyls [FA], Glycerolipids [GL], Sphingolipids [SP], Sterol Lipids [ST], Prenol Lipids [PR], Saccharolipids [SL], and Polyketides [PK]. [0582] 17. A process according to any one of the proceeding clauses, wherein the anti-agglomerant comprises a fused ring system having from 2 to 10 fused 4, 5 or 6-membered rings, which are saturated or unsaturated rings, for example an optionally substituted chromane ring system or an optionally substituted gonane, optionally substituted sterol, optionally substituted sterone, optionally substituted phytosterol, optionally substituted sterane, cholestane, cholestene or other related ring system or secosteorid system, for example, comprising three fused 6-membered cyclohexane rings and one fused five membered ring, wherein the optional substituents are independently selected from one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, acyl, carboxylate, halide, amine or amide functionalities. [0583] 18. A process according to any one of the proceeding clauses, the anti-agglomerant has the following general structure:

##STR00147## [0584] wherein [0585] each X is independently (CH.sub.2).sub.n, where n is 0 to 4, O, N or S; [0586] when X outside the ring is (CH.sub.2).sub.n and n is 1 to 4, Z is selected from the group of functionalities consisting of: optionally substituted alkyl carboxylate, optionally substituted alkyl dicarboxylate, optionally substituted alkyl dicarboxylate ester, optionally substituted alkyl amide, optionally substituted alkyl ether, optionally substituted alkyl ester; [0587] when X outside the ring is O, Z is selected from the group of functionalities consisting of: optionally substituted carboxylate, optionally substituted dicarboxylate, optionally substituted dicarboxylate ester, optionally substituted amide, optionally substituted ether, optionally substituted ester; [0588] when X outside the ring is N, Z is selected from the group of functionalities consisting of: optionally substituted amine, optionally substituted amide, optionally substituted azo, optionally substituted azoxy, optionally substituted carbamate, optionally substituted diazo, optionally substituted diazonium, optionally substituted guanidine, optionally substituted hydrazine, optionally substituted hydrazole, optionally substituted imine; optionally substituted carbonic acid bisamides, optionally substituted oximes, optionally substituted nitrones, and optionally substituted nitriles; when X outside the ring is S, Z is selected from the group of functionalities consisting of: thiol, selfenic acid, optionally substituted sulfide, optionally substituted disulfide, optionally substituted sulfinic acid, optionally substituted sulfinic acid ester, optionally substituted sulfonic acid, optionally substituted sulfonic acid ester; [0589] Y is an optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl; [0590] R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are independently selected from H, OR.sup.x wherein R.sup.x is H or optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl; [0591] wherein the optional substituents are independently selected from one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, acyl, carboxylate, halide, amine or amide functionalities. [0592] 19. A process according to clause 18, wherein X outside the ring is O, and Z is selected from the group of functionalities consisting of: optionally substituted carboxylate, optionally substituted dicarboxylate, optionally substituted dicarboxylate ester, optionally substituted amide, optionally substituted ether, optionally substituted ester. [0593] 20 A process according to clause 18 or clause 19, wherein Z is a carboxylate, alkyl carboxylate, ester or alkyl ester functionality. [0594] 21. A process according to any one of clauses 18 to 20, wherein the optionally substituted dicarboxylate functionality is of formula C(O)(L).sub.nC(O)OR.sup.6, wherein L is a linker group, n is 1 to 10, R.sup.6 is H or branched or unbranched alkyl. [0595] 22. A process according to any one of clause 18 to 21, wherein the optionally substituted dicarboxylate functionality is selected from oxalate, malonate, succinate, glutarate, adipate, or pimelate. [0596] 23. A process according to any one of clause 18 to 22, wherein Y is an optionally substituted branched or unbranched C.sub.3-C.sub.25 alkyl, an optionally substituted branched or unbranched C.sub.3-C.sub.25 alkenyl or an optionally substituted branched or unbranched C.sub.3-C.sub.25 alkynl, more preferably, an optionally substituted branched or unbranched C.sub.12-C.sub.17 alkyl, an optionally substituted branched or unbranched C.sub.12-C.sub.17 alkenyl or an optionally substituted branched or unbranched C.sub.5-C.sub.17 alkynl. [0597] 24. A process according to any one of the preceding clauses, wherein the anti-agglomerant has the following general structure:

##STR00148## [0598] wherein [0599] R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R are independently H, OH, methyl, ethyl, propyl or butyl; [0600] L is (CH.sub.2).sub.n-alkyl linker and n is 2, 3 or 4 and R.sup.6 is H; [0601] Y is optionally substituted branched or unbranched C.sub.12-C.sub.17 alkyl, an optionally substituted branched or unbranched C.sub.12-C.sub.17 alkenyl or an optionally substituted branched or unbranched C.sub.5-C.sub.17 alkynl. [0602] 25. A process according to clause 24, wherein (i) R.sup.1 is methyl, R.sup.2 is methyl, R.sup.3 is methyl, R.sup.4 is methyl, and R.sup.5 is H; and Y is a saturated or unsaturated C.sub.16 alkyl having a methyl branch at carbons 2, 8 and 12 of the C.sub.16 alkyl chain, the anti-agglomerant is based on alpha-tocopherol or alpha-tocotrienol; (ii) R.sup.1 is methyl, R.sup.2 is H, R.sup.3 is methyl, R.sup.4 is methyl, and R.sup.5 is H; and Y is a saturated or unsaturated C.sub.16 alkyl having a methyl branch at carbons 2, 8 and 12 of the C.sub.16 alkyl chain, the anti-agglomerant is based on beta-tocopherol or beta-tocotrienol; (iii) R.sup.1 is H, R.sup.2 is H, R.sup.3 is methyl, R.sup.4 is methyl, and R.sup.5 is H; and Y is a saturated or unsaturated C.sub.16 alkyl having a methyl branch at carbons 2, 8 and 12 of the C.sub.16 alkyl chain, the anti-agglomerant is based on gamma-tocopherol or gamma-tocotrienol; (iv) R.sup.1 is H, R.sup.2 is H, R.sup.3 is methyl, R.sup.4 is methyl, and R.sup.5 is H; and Y is a saturated or unsaturated C.sub.16 alkyl having a methyl branch at carbons 2, 8 and 12 of the C.sub.16 alkyl chain, the anti-agglomerant is based on delta-tocopherol or delta-tocotrienol. [0603] 26. A process according to any one of the proceeding clauses, wherein the lipophilic tail group of the anti-agglomerant of the invention is based on a vitamin E based product such as alpha-tocopherol, alpha-tocotrienol, beta-tocotrienol, delta-tocotrienol, gamma-tocotrienol, didesmethyl tocotrienol, beta-tocopherol, alpha-tocopheronic acid, alpha-tocopheronolactone, gamma-tocopherol, and delta-tocopherol, most preferably, and alpha tocopherol succinate. [0604] 27. A process according to any one of clauses 1 to 17, wherein the anti-agglomerant has the following general formula:

##STR00149## [0605] wherein [0606] each of rings a, b, c, d can be independently saturated or unsaturated; [0607] each X is independently (CH.sub.2).sub.n, where n is 0 to 4, O, N or S; [0608] when X is (CH.sub.2).sub.n and n is 1 to 4, Z is selected from the group of functionalities consisting of: optionally substituted alkyl carboxylate, optionally substituted alkyl dicarboxylate, optionally substituted alkyl dicarboxylate ester, optionally substituted alkyl amide, optionally substituted alkyl ether, optionally substituted alkyl ester; [0609] when X is O, Z is selected from the group of functionalities consisting of: optionally substituted carboxylate, optionally substituted dicarboxylate, optionally substituted dicarboxylate ester, optionally substituted amide, optionally substituted ether, optionally substituted ester; [0610] when X is N, Z is selected from the group of functionalities consisting of: optionally substituted amine, optionally substituted amide, optionally substituted azo, optionally substituted azoxy, optionally substituted carbamate, optionally substituted diazo, optionally substituted diazonium, optionally substituted guanidine, optionally substituted hydrazine, optionally substituted hydrazole, optionally substituted imine; optionally substituted carbonic acid bisamides, optionally substituted oximes, optionally substituted nitrones, and optionally substituted nitriles; when X outside the ring is S, Z is selected from the group of functionalities consisting of: thiol, selfenic acid, optionally substituted sulfide, optionally substituted disulfide, optionally substituted sulfinic acid, optionally substituted sulfinic acid ester, optionally substituted sulfonic acid, optionally substituted sulfonic acid ester, [0611] wherein the optional substituents are independently selected from one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, acyl, carboxylate, halide, amine or amide functionalities; [0612] Y is an optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl; [0613] R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently selected from H, OH, COR.sup.x, COOR.sup.x, OR.sup.x wherein R.sup.x is H or optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl, wherein the optional substituents are independently selected from one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, acyl, carboxylate, halide, amine or amide functionalities. [0614] 28. A process according to clause 27, wherein the anti-agglomerant has general formula,

##STR00150## [0615] wherein [0616] X is O; [0617] Z is selected from the group of functionalities consisting of: optionally substituted carboxylate, optionally substituted dicarboxylate, optionally substituted dicarboxylate ester, optionally substituted amide, optionally substituted ether, optionally substituted ester; [0618] R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently selected from H, OR.sup.x wherein R.sup.x is H or optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl; [0619] wherein the optional substituents are independently selected from one or more of C.sub.1-C.sub.6 alkyl, hydroxyl, acyl, carboxylate, halide, amine or amide functionalities; [0620] Y is an optionally substituted branched or unbranched alkyl, an optionally substituted branched or unbranched alkenyl or an optionally substituted branched or unbranched alkynl. [0621] 29. A process according to clauses 27 or 28, wherein Y is an optionally substituted branched or unbranched C.sub.7-C.sub.10 alkyl, an optionally substituted branched or unbranched C.sub.7-C.sub.10 alkenyl or an optionally substituted branched or unbranched C.sub.7-C.sub.10 alkynl. [0622] 30. A process according to any one of clauses 27 to 29, wherein the anti-agglomerant has the following general structure:

##STR00151## [0623] 31. A process according to any one of clauses 27 to 30, the anti-agglomerant has the following general structure:

##STR00152## [0624] wherein [0625] L is (CH.sub.2).sub.n-alkyl linker and n is 1, 2, 3 or 4, and R.sup.7 is H; and Y is an optionally substituted branched C.sub.7-C.sub.10 alkyl, an optionally substituted branched C.sub.7-C.sub.10 alkenyl. [0626] 32. A process according to any one of clauses 27 to 31, the hydrophilic head group is based on succinate, preferably, being contained within a sitosterol succinate anti-agglomerant molecule. [0627] 33. Use of an oil soluble anti-agglomerant to prevent gas hydrate agglomeration in a hydrocarbon phase, said at least one oil anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group. [0628] 34. Use of an anti-agglomerant in the prevention of gas hydrate cluster formation, said anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group. [0629] 35. Use according to clause 33 or 34 in oil and/or natural gas recovery, particularly where the hydrocarbon phase is transported in cold conditions, both onshore and offshore, preferably, as an alternative or supplement to thermodynamic inhibitors (MEG) in applications where thermodynamic inhibitors are used. [0630] 36. Use of an anti-agglomerant derived from a lipophilic, oil soluble naturally occurring product, a precursor to, a metabolite or a derivative thereof and comprising at least one non-ionic hydrophilic head group as a corrosion inhibitor. [0631] 37. Use according to clause 36, wherein the anti-agglomerant is used in the presence of a hydrocarbon phase.