Method of and a composition for controlling gas hydrate blockage through the addition of a synergistically acting blend with a quaternary benzyl ammonium compound

Abstract

The present disclosure relates to a gas hydrate inhibitor composition, comprising A) a compound according to formula (1) ##STR00001## wherein R1 is an alkyl group having from 1 to 5 carbon atoms; R2 is hydrogen or an alkyl group having from 1 to 5 carbon atoms; R3 is present or not as hydrogen and organic moieties having from 1 to 20 carbon atoms; R4 is selected from —(CH.sub.2).sub.t—, —[CH.sub.2—CHR.sup.6).sub.t]—, —(CH.sub.2—CHR.sup.6O).sub.u—(CH.sub.2).sub.t— and combinations thereof; R5 is an alkyl or alkenyl group having 4 to 22 carbon atoms; R6 is hydrogen or an alkyl group having from 1 to 4 carbon atoms; R7 is hydrogen or an alkyl group having from 1 to 4 carbon atoms; R8 is present or not as hydrogen or organic moieties having from 1 to 20 carbon atoms; t is 2, 3 or 4; u is an integer between 0 and 100; n is 0 or 1 m is 0 or 2 o is 0 or 2, p is 0 or 1 X.sup.− is an anion, and a synergistic cationic surfactant which is selected from quaternary benzyl ammonium salts having besides the benzyl group at least one C.sub.8-C.sub.18-alkyl group bound to the nitrogen atom.

Claims

1. A method for inhibiting gas hydrate formation in a system containing hydrocarbons and water, comprising the step of contacting the system with a composition comprising A) from 5 to 95 weight-% of a compound according to formula (1) ##STR00008## wherein R1 is an alkyl group having from 1 to 5 carbon atoms; R2 is hydrogen or an alkyl group having from 1 to 5 carbon atoms; R3 is present or not as hydrogen and organic moieties having from 1 to 20 carbon atoms; R4 is selected from —(CH2)t-, —[(CH2-CHR6)t]-, —(CH2-CHR6O)u-(CH2)t- and combinations thereof; R5 is an alkyl or alkenyl group having 4 to 22 carbon atoms; R6 is hydrogen or an alkyl group having from 1 to 4 carbon atoms; R7 is hydrogen or an alkyl group having from 1 to 4 carbon atoms; R8 is present or not as hydrogen or organic moieties having from 1 to 20 carbon atoms; t is 2, 3 or 4; u is an integer between 0 and 100; n is 0 or 1 m is 0 or 2 o is 0 or 2 p is 0 or 1 X— is an anion, and B) from 5 to 95 weight-% of a synergistic cationic surfactant which is selected from quaternary benzyl ammonium salts having besides the benzyl group at least one C.sub.8-C.sub.18-alkyl group bound to the nitrogen atom.

2. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein B) is from 5 to 95 weight-% of a quaternary benzyl ammonium compound of the formula (19): ##STR00009## wherein R.sup.11 is an alkyl group having 8 to 18 carbon atoms, R.sup.12 is an alkyl group having from 1 to 5 carbon atoms, R.sup.19 is an alkyl group having from 1 to 18 carbon atoms, and Y.sup.− is an anion.

3. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein X.sup.− is selected from the group consisting of hydroxide, carboxylate, halide, sulphate, organic sulphonate, acrylate, methacrylate, and combinations thereof.

4. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein Y.sup.− is selected from the group consisting of bromide, chloride, hydroxide and combinations thereof.

5. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein R3 is hydrogen, and the anion X.sup.− is selected from the group consisting of hydroxide, carboxylate, halide, sulphate, organic sulphonate, and combinations thereof.

6. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the step of contacting may be achieved by mixing, blending with mechanical mixing equipment or devices, stationary mixing setup or equipment, magnetic mixing or other suitable methods, other equipment known to one skilled in the art or combinations thereof to provide adequate contact and/or dispersion of the composition in the mixture.

7. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the step of contacting can be made in-line or offline or both.

8. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the pressure is at or greater than atmospheric pressure.

9. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the pressure is greater than about 1 MPa.

10. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the composition further comprises at least one solvent.

11. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 10, wherein the solvent is selected from the group consisting of water, methanol, ethanol, iso-propanol, n-butanol, iso-butanol, 2-ethyl hexanol, ethylene glycol, 1,2-propylene glycols, 1,3-propylene glycol, hexylene glycol, ethylene glycol mono butylether (butyl cellosolve), ethylene glycol dibutyl ether, tetrahydrofuran, methylethylketone, diisobutylketone, N-methylpyrrolidone, cyclohexanone, xylene, toluene, and mixtures thereof.

12. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 10, wherein the solvent is present in the inhibitor composition in the range from 0.1% to about 95%, based on the volume of the inhibitor composition.

13. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the concentration of the compound according to formula (1) is between about 0.01 wt.-% and about 5 wt.-% based on the water content.

14. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein the composition further comprises thermodynamic or kinetic gas hydrate inhibitors.

15. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein R.sup.1 is n-butyl, R.sup.2 is n-butyl, R.sup.3 is C.sub.2H.sub.5, R.sup.4 is —(CH.sub.2).sub.t—, R.sup.5 is C.sub.12H.sub.25, R.sup.6 is H, R.sup.7 is H, R.sup.8 is not present, m is 0, n is 1, o is 2, p is 1, t is 3, u is not present, and X.sup.− is ethyl sulfate.

16. The method for inhibiting gas hydrate formation in a system containing hydrocarbons and water according to claim 1, wherein R.sup.1 is n-butyl, R.sup.2 is n-butyl, R.sup.3 is H, R.sup.4 is —(CH2)t-, R.sup.5 is coco alkyl, R.sup.6 is H, R.sup.7 is not present, R.sup.8 is not present, m is 0, n is 0, o is 0, p is 1, t is 3, u is not present, and X— is acrylate.

Description

EXAMPLES

Test Procedure 1: Evaluation of Hydrate Inhibitor Compounds in Parallel Process Development Reactors

(1) To a 100 mL stainless steel reactor, attached to thermostat and a liquid handling system, dodecane (10 mL), brine (20 mL of 5% NaCl, density of 1.07 g/cm.sup.3 at 25° C.), and the anti-agglomerant formulation were added at 30° C. The reactor was pressurized to 95 bar with Erdgas H (see Table 1 for composition). The stirrer speed was adjusted to 1000 rpm for 1 min to saturate the liquid with gas. Subsequently the stirrer speed was reduced to 200 rpm, and a temperature setting of −10° C. was initiated. Monitoring the internal temperature of the reactor showed a characteristic exotherm indicative of hydrate formation below a threshold temperature. If the exotherm was accompanied by a prolonged increase in stirrer power uptake this was indicative of agglomeration, signifying a failure. If the stirrer power remained constant or following an increase returned to the original baseline, agglomeration was prevented; indicating a pass.

(2) For evaluation of their hydrate inhibitor performance, the testing was started with 0.3 wt.-% of the hydrate inhibitor, formulated as a 60% active solution in methanol. If samples failed at this dose rate, they were labelled as >0.3 wt.-% minimum effective dose (MED) and were not tested further. If samples initially tested at 0.3 wt.-% passed, they were sequentially and incrementally reduced in dose rate by 0.05 wt.-% each time until a dose rate was used that failed. When that occurred, the last passing dose rate was input into the Table (4) as the Minimum Effective Dose (MED).

(3) TABLE-US-00001 TABLE 1 Erdgas H gas composition Component Name Chemical Symbol Amount (mol-%) Nitrogen N.sub.2 0.14 Carbon Dioxide CO.sub.2 0 Methane C.sub.1 87.56 Ethane C.sub.2 7.6 Propane C.sub.3 3 i-Butane i-C.sub.4 0.5 n-Butane n-C.sub.4 0.8 i-Pentane i-C.sub.5 0.2 n-Pentane n-C.sub.5 0.2

(4) Monitoring of the internal temperature of the reactor shows a characteristic exotherm indicative of hydrate formation below a threshold temperature. If the exotherm is accompanied by a prolonged increase in stirrer power uptake this is indicative of agglomeration; signifying a failure. If the stirrer power remains constant or following an increase returns to the original baseline, agglomeration is prevented; indicating a pass.

(5) Water Drop Testing

(6) When appraising Anti-Agglomerants, performance is obviously the highest criteria to consider, however there are several secondary properties that should also be considered that can have an effect on the operational system to which the AA's are applied. It should be realized that both the primary criteria of performance as well as the secondary properties needs to be met for a particular chemistry or product to be suitable for use within an operational system. The water drop of the embodiments here (actives plus synergists), were surprisingly better relative to the standard AA's alone. When considering the water drop, a time period was chosen that would be considered aggressive (less time) for offshore separation, in part to ensure good translation to eventual field application conditions. Specifically, at the total water drop (amount of expected water to be separated) was observed after vigorous mixing (created emulsion), with a time duration of 1 minute.

(7) Experimental Details:

(8) Into a graduated 100 mL cylinder with conical bottom (typically used for emulsion testing), 50 mL of oil and 50 mL of water were charged. The water was 6% brine (using NaCl) and the oil was a medium crude from the Gulf of Mexico. To the 100 mL of total fluids 1 wt.-% in respect to the aqueous phase of a hydrate inhibitor (as a 60 wt.-% active formulation) were added. A dose rate of 1% was deliberately chosen to highlight the effect of the hydrate inhibitors on the water drop. The bottles were capped, shaken vigorously by hand, and allowed to stand at room temperature for 1 minute, at which point the amount of water that could be observed as a separate phase was recorded. This number was then multiplied by 2 to obtain the results shown in Table 4 as a percent of water present. A value of 100% means that all the water was observed as a separate phase. If less than 100% was observed, the remaining water was either within the oil or as part of a “rag layer” or emulsion layer. For testing, gas hydrate inhibitor formulations were prepared by blending amphiphiles (A) according to table 2 and cationic surfactants (B) according to table 3 with the weight ratios according to table 4. For ease of handling, the formulations were adjusted to 60 wt.-% active content with methanol.

(9) These formulations were tested for their minimum dosage rate for hydrate inhibition according to test procedure 1. The minimum dosage rates for a pass given in table 4 refer to the required minimum dosage of active ingredient.

(10) TABLE-US-00002 TABLE 2 Characterization of tested gas hydrate inhibitors A) according to Formula 1 wherein: Residue A1 A2 R.sup.1 n-butyl n-butyl R.sup.2 n-butyl n-butyl R.sup.3 C.sub.2H.sub.5 H R.sup.4 —(CH.sub.2).sub.t— —(CH.sub.2).sub.t— R.sup.5 C.sub.12H.sub.25 Coco alkyl R.sup.6 H H R.sup.7 H — R.sup.8 — — m 0 0 n 1 0 o 2 0 p 1 1 t 3 3 u — — X.sup.− ethyl sulfate acrylate

(11) TABLE-US-00003 TABLE 3 Characterization of tested cationic surfactants B) having general formula N.sup.+(R.sup.11)(R.sup.12)(R.sup.19)(R.sup.20) Y.sup.− R.sup.11 R.sup.12 R.sup.19 R.sup.20 Y.sup.− B1 coco alkyl CH.sub.3 CH.sub.3 benzyl Cl.sup.− B2 C.sub.8H.sub.17 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B3 C.sub.10H.sub.21 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B4 C.sub.12H.sub.25 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B5 C.sub.12H.sub.25 CH.sub.3 CH.sub.3 benzyl Br.sup.− B6 C.sub.14H.sub.29 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B7 C.sub.16H.sub.33 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B8 C.sub.18H.sub.37 CH.sub.3 CH.sub.3 benzyl Cl.sup.− B9 iso-C.sub.13H.sub.27 CH.sub.3 C.sub.2H.sub.5 benzyl ethyl sulfate B10 coco alkyl CH.sub.3 coco alkyl benzyl Br.sup.− B11 (comp.) C.sub.16H.sub.33 CH.sub.3 CH.sub.3 CH.sub.3 Cl.sup.− B12 (comp.) C.sub.12H.sub.25 CH.sub.3 CH.sub.3 C.sub.4H.sub.9 Br.sup.− B13 (comp.) C.sub.16H.sub.33 CH.sub.3 CH.sub.3 C.sub.4H.sub.9 Br.sup.− B14 (comp.) C.sub.18H.sub.37 CH.sub.3 CH.sub.3 C.sub.4H.sub.9 Br.sup.− B15 (comp.) C.sub.10H.sub.21 C.sub.4H.sub.9 C.sub.4H.sub.9 C.sub.4H.sub.9 Br.sup.− B16 (comp.) C.sub.12H.sub.25 H CH.sub.3 C.sub.12H.sub.25 Cl.sup.− Coco alkyl comprises as main components 51 wt.-% C.sub.12H.sub.25, and 16 wt.-% C.sub.14H.sub.29.

(12) TABLE-US-00004 TABLE 4a Results from autoclave testing (components testing; comparative) Gas hydrate inhibitor (wt.-% active) MED water drop Example comp. A comp. B (wt.-%) (%)  1 (comp.) A1 (100) — 0.30 80  2 (comp.) A2 (100) — 0.30 84  5 (comp.) — B1 (100) >0.30.sup.(a) 58  6 (comp.) — B2 (100) >0.30.sup.(a) 62  7 (comp.) — B3 (100) >0.30.sup.(a) 60  8 (comp.) — B4 (100) >0.30.sup.(a) 60  9 (comp.) — B5 (100) >0.30.sup.(a) 56 10 (comp.) — B6 (100) >0.30.sup.(a) 62 11 (comp.) — B7 (100) >0.30.sup.(a) 64 12 (comp.) — B8 (100) >0.30.sup.(a) 60 13 (comp.) — B9 (100) >0.30.sup.(a) 54 14 (comp.) — B10 (100) >0.30.sup.(a) 60 15 (comp.) — B11 (100) >0.30.sup.(a) 64 16 (comp.) — B12 (100) 0.30 70 17 (comp.) — B13 (100) >0.30.sup.(a) 76 18 (comp.) — B14 (100) >0.30.sup.(a) 70 19 (comp.) — B15 (100) 0.30 72 20 (comp.) — B16 (100) >0.30.sup.(a) 70 .sup.(a)>0.30 wt.-% means it did not pass at 0.30 wt.-% dose rate and was not tested at higher concentration.

(13) TABLE-US-00005 TABLE 4b Results from autoclave testing (formulations containing A1) Gas hydrate inhibitor (wt.-% active) MED water drop Example comp. A comp. B (wt.-%) (%) 21 A1 (50.0) B1 (50.0) 0.10 86 22 A1 (71.4) B1 (28.6) 0.05 88 23 A1 (50.0) B2 (50.0) 0.15 88 24 A1 (71.4) B2 (28.6) 0.10 88 25 A1 (50.0) B3 (50.0) 0.10 86 26 A1 (71.4) B3 (28.6) 0.10 90 27 A1 (50.0) B4 (50.0) 0.10 86 28 A1 (71.4) B4 (28.6) 0.05 88 29 A1 (28.6) B4 (71.4) 0.10 86 30 A1 (50.0) B6 (50.0) 0.10 88 31 A1 (71.4) B6 (28.6) 0.05 92 32 A1 (50.0) B7 (50.0) 0.10 88 33 A1 (71.4) B7 (28.6) 0.05 88 34 A1 (50.0) B10 (50.0) 0.15 86 35 A1 (71.4) B10 (28.6) 0.15 86 36 (comp.) A1 (50.0) B14 (50.0) 0.20 84 37 (comp.) A1 (71.4) B14 (28.6) 0.20 84 38 (comp.) A1 (50.0) B15 (50.0) 0.30 82 39 (comp.) A1 (71.4) B15 (28.6) 0.25 84 40 (comp.) A1 (50.0) B16 (50.0) >0.30.sup.(a) 84 41 (comp.) A1 (71.4) B16 (28.6) >0.30.sup.(a) 84

(14) TABLE-US-00006 TABLE 4c Results from autoclave testing (formulations containing A2) Gas hydrate inhibitor (wt.-% active) MED water drop Example comp. A comp. B (wt.-%) (%) 42 A2 (50.0) B1 (50.0) 0.05 94 43 A2 (71.4) B1 (28.6) 0.05 96 44 A2 (28.6) B1 (71.4) 0.10 94 45 A2 (50.0) B2 (50.0) 0.15 94 46 A2 (71.4) B2 (28.6) 0.10 94 49 A2 (50.0) B4 (50.0) 0.05 98 50 A2 (71.4) B4 (28.6) 0.05 96 51 A2 (50.0) B5 (50.0) 0.10 96 52 A2 (71.4) B5 (28.6) 0.10 96 53 A2 (80.0) B6 (20.0) 0.05 98 54 A2 (50.0) B6 (50.0) 0.05 96 55 A2 (20.0) B6 (80.0) 0.15 94 56 A2 (50.0) B7 (50.0) 0.10 94 57 A2 (71.4) B7 (28.6) 0.05 96 58 A2 (50.0) B9 (50.0) 0.15 96 59 A2 (71.4) B9 (28.6) 0.10 94 60 A2 (50.0) B10 (50.0) 0.15 96 61 A2 (71.4) B10 (28.6) 0.15 96 62 (comp.) A2 (50.0) B11 (50.0) 0.30 90 63 (comp.) A2 (71.4) B11 (28.6) 0.25 92 64 (comp.) A2 (28.6) B12 (71.4) 0.20 90 65 (comp.) A2 (50.0) B12 (50.0) 0.20 90 66 (comp.) A2 (71.4) B12 (28.6) 0.25 88 67 (comp.) A2 (50.0) B13 (50.0) 0.20 88 68 (comp.) A2 (71.4) B13 (28.6) 0.20 86 69 (comp.) A2 (50.0) B16 (50.0) 0.30 92 70 (comp.) A2 (71.4) B16 (28.6) 0.25 92