COMPOSITION WHICH MAKES IT POSSIBLE TO DELAY THE FORMATION OF GAS HYDRATES

Abstract

Provided is a composition comprising at least one polymer, the repeat unit of which comprises at least one amide functional group, at least one polyetheramine with a weight-average molecular weight (M.sub.W) of greater than 100 g.mol.sup.1 and exhibiting at least two secondary and/or tertiary amine functional groups, and optionally, but preferably, at least one organic solvent. Also provided is method of using of the composition for delaying, indeed even preventing, the formation of gas hydrates, in particular in a process for extracting oil and/or gas and/or condensates, and also to the process for delaying, indeed even preventing, the formation and/or the agglomeration of gas hydrates, employing a composition as defined above.

Claims

1. A composition comprising: a) at least one polymer, the repeat unit of which comprises at least one amide functional group, b) at least one polyetheramine with a weight-average molecular weight (M.sub.W) of greater than 100 g.mol.sup.1, and exhibiting at least two secondary and/or tertiary amine functional groups, and c) optionally, at least one organic solvent.

2. The composition according to claim 1, in which the polymer, the repeat unit of which comprises at least one amide functional group, is a polymer obtained by polymerization of one or more monomers chosen from substituted or unsubstituted (meth)acrylamides, or vinyl monomers having lactam groups.

3. The composition according to claim 1, in which the polymer, the repeat unit of which comprises at least one amide functional group, is a polymer obtained by polymerization of one or more monomers chosen from vinylpyrrolidone (VP), vinylcaprolactam (VCap), acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N,N-dialkylacrylamide, N,N-dialkylmethacrylamide, N,N-dialkylaminoalkylacrylamide, N,N-dialkylaminoalkylmethacrylamide, and also their quaternary alkylammonium salts.

4. The composition according to claim 1, in which the polymer, the repeat unit of which comprises at least one amide functional group, is a polymer obtained by polymerization of monomers of vinylcaprolactam (VCap) type and of vinylpyrrolidone (VP) type.

5. The composition according to claim 1, in which the total amount of the copolymer or copolymers a) is of between 1% and 50% by weight, with respect to the total weight of the composition.

6. The composition according to claim 1, in which the polyetheramine b) exhibits at least two secondary and/or tertiary amine functional groups.

7. The composition according to claim 1, in which the polyetheramine b) is represented by the formula (I) below: ##STR00002## in which: R.sub.1 and R.sub.2, which are identical or different, represent a saturated or unsaturated and linear or branched hydrocarbon chain comprising from 1 to 24 carbon atoms, limits included, R.sub.3 represents a hydrogen atom, a methyl radical or an ethyl radical, and n represents an integer of between 1 and 50, limits included.

8. The composition according to claim 1, in which the total amount of the polyetheramine(s) is between 0.5% and 40% by weight, with respect to the total weight of the composition.

9. The composition according to claim 1, in which the said at least one organic solvent is chosen from alkyl alcohols comprising from 1 to 4 carbon atoms, glycol ethers and their mixtures.

10. A process for delaying, or preventing, the formation and/or the agglomeration of gas hydrates, comprising a stage of addition of a composition as defined in claim 1 to a mixture having a composition liable to form hydrates.

11. The process according to claim 10, in which the composition according to the invention is added in an amount between 0.1% and 10% by weight, with respect to the total weight of the aqueous phase in a production fluid.

12. The process according to claim 10, in which the composition is introduced into the production fluid continuously, discontinuously, regularly or irregularly, or temporarily, in one or more portions.

13. The process according to claim 10, in which the fluid treated with the composition according to the invention is a drilling mud or a completion fluid.

14. Use of a composition according to claim 1 for delaying, or preventing, the formation and/or the agglomeration of hydrates, preferably in a process for extracting oil and/or gas and/or condensates.

Description

EXAMPLES

Example 1

[0076] The kinetic effectiveness of different hydrate-inhibiting compositions was tested on a mixture comprising: [0077] a gas phase, consisting of 98 mol % of methane and 2 mol % of propane; and [0078] an aqueous phase comprising a 1 g.l.sup.1 NaCl solution.

[0079] The tests were carried out at a pressure of 135 bar (13.5 MPa), a pressure value which is characteristic of the extraction conditions where a risk of hydrate formation exists. The equilibrium temperature of this mixture at 135 bar (13.5 MPa) is approximately 19.5 C. In other words, at 135 bar (13.5 MPa), the gas hydrates form when the temperature becomes less than or equal to 19.5 C.

[0080] The tests are carried out in a mechanically stirred cell temperature-controlled by a jacket. The cell is cylindrical in shape with an internal volume of approximately 292.6 cm.sup.3 (149 mm in height for 50 mm in diameter). It is made of steel resistant to 200 bar (20 MPa) and is protected by a valve. The working pressure is provided by an AG-30 gas booster from Haskel. The cell comprises instruments in order to be able to continuously monitor the internal pressure, the stirring torque and the temperature.

[0081] In order to carry out the evaluations of the different products, 250 cm.sup.3 of aqueous phase containing the additive to the evaluated, or without additive (reference), are first introduced into the cell, under vacuum by suction. After equilibrating the temperature at 19.5 C., the gas mixture is charged, with stirring, to the cell until a stable pressure of 135 bar (13.5 MPa) is obtained.

[0082] The assembly is subsequently heated to and maintained at 30 C. for 24 hours in order to erase the thermal history of the mixture and is then brought down, at the rate of 0.2 C./min, to the temperature corresponding to the targeted sub-cooling (in this instance 9.5 C. and 4.5 C. for respective sub-coolings of 10 C. and 15 C.).

[0083] The kinetic effectiveness of the hydrate-inhibiting compositions is measured at different sub-coolings (10 C. and 15 C.) but also at different dosages. The dosage corresponds in this instance to the amount (weight) of hydrate-inhibiting composition introduced into the aqueous phase, with respect to the weight of the water.

[0084] The kinetic performance of the hydrate-inhibiting compositions is determined by the measurement of the delay time to the formation of the hydrate crystals. This time, also known as induction time, is expressed in hours or in days. In other words, the longer the induction time, the more effective the hydrate inhibitor.

[0085] In this instance, this time is measured from the moment when the temperature in the cell reaches the target temperature of the test corresponding to the sub-cooling studied (9.5 C. and 4.5 C. for respective sub-coolings of 10 C. and 15 C.) and the pressure in the cell has stabilized. The final point for measuring the induction time corresponds to the start of formation of the hydrates. It is located on the curve of pressure as a function of the time by the point where the pressure begins to fall in the cell (fall in pressure corresponding to the consumption of gas in order to form solid hydrates) and confirmed by an increase in the torque of the stirrer (viscosification of the medium, which becomes loaded with solid) and possibly a very slight exothermic peak on the temperature curve.

[0086] The composition A, according to the invention, and the comparative compositions B, C, D and E (in accordance with the teaching of the patent U.S. Pat. No. 6,180,699) were prepared by mixing the different components, the amounts of which are expressed in Table 1 below.

[0087] Unless otherwise indicated, all the amounts are shown as percentage by weight, with respect to the total weight of the composition.

TABLE-US-00001 TABLE 1 Composition A Composition B Composition C Composition D Composition E (invention) (comparative) (comparative) (comparative) (comparative) Luvicap 55W.sup.(a) 20% 30% 20% Luvicap EG.sup.(b) 20% Jeffamine D 230.sup.(c) 10% Jeffamine D 400.sup.(c) 10% Jeffamine SD 401.sup.(d) 10% 30% 2-Butoxyethanol 70% 70% 70% 70% 70% .sup.(a)vinylpyrrolidone (VP)/vinylcaprolactam (VCap) 1:1 copolymer, sold by BASF .sup.(b)polyvinylcaprolactam (VCap) homopolymer, sold by BASF .sup.(c)polyalkoxydiamine (di(primary amine)), sold by Huntsman .sup.(d)polyalkoxydiamine (di(secondary amine)), sold by Huntsman

[0088] The kinetic effectiveness of the hydrate-inhibiting compositions, for a sub-cooling of 10 C., is evaluated for respective dosages of 1% and 3% by weight for each of the compositions A (invention), B, C, D and E (comparative). Each of the test compositions is introduced into the aqueous phase and the experiment is carried out as described above.

[0089] The kinetic performance of these compositions, characterized by the induction time, was measured twice, and the mean of these measurements is expressed in Table 2 below.

TABLE-US-00002 TABLE 2 Results for a sub-cooling of 10 C. Composition A Composition B Composition C Composition D Composition E (invention) (comparative) (comparative) (comparative) (comparative) Induction time 105 hours 86 hours 10 hours 60 hours 50 hours Dose = 1% Induction time 120 hours 90 hours 15 hours 70 hours 60 hours Dose = 3%

[0090] The above results show that, for a sub-cooling of 10 C., the compositions of the present invention are more effective than the comparative compositions. This is because, in the composition according to the present invention, where in the vinylcaprolactam/vinylpyrrolidone copolymer is in a mixture with a di(secondary amine) (composition A), 105 hours (for a dosage of 1% by weight) and 120 hours (for a dosage of 3% by weight) are needed to see the appearance of gas hydrates.

[0091] By way of comparison, the composition C, which comprises only the solvent and the same di(secondary amine), delays the appearance of the hydrates by only 10 hours, for a dosage of 1% by weight, and by only 15 hours, for a dosage of 3% by weight. The composition B, which comprises only the solvent and the same copolymer, makes it possible to delay their formation by only 86 hours (for a dosage of 1% by weight) and by only 90 hours (for a dosage of 3% by weight).

[0092] These results also show that the composition according to the present invention (composition A) is much more effective than the compositions known from the prior art, for example the composition E according to the patent U.S. Pat. No. 6,180,699, which delays the formation of hydrate by only 50 hours (for a dosage of 1% by weight) and by only 60 hours (for a dosage of 3% by weight).

[0093] The same tests are subsequently carried out for a greater sub-cooling, now of 15 C. Each of the compositions A (invention) and B, C, D and E (comparative) is evaluated, according to the protocol described above, at the doses of 1% and 3% by weight of each of the compositions A (invention) and B, C, D and E (comparative).

[0094] The kinetic performance of these compositions was measured twice, and the mean of these measurements is expressed in Table 3 below.

TABLE-US-00003 TABLE 3 Results for a sub-cooling of 15 C. Composition A Composition B Composition C Composition D Composition E (invention) (comparative) (comparative) (comparative) (comparative) Induction time 26 hours 1 hour <1 hour 4 hours 2 hours Dose = 1% Induction time 90 hours 3 hours <1 hour 12 hours 4 hours Dose = 3%

[0095] These results lead to very similar conclusions. At a dosage of 1% by weight, the comparative composition D delays the formation of gas hydrates by only 8 hours, whereas the composition according to the invention (composition A) delays this formation by 26 hours.

[0096] Furthermore, the vinylcaprolactam/vinylpyrrolidone copolymer alone (composition B), and also the di(secondary amine) alone (composition C), are poor kinetic hydrate inhibitors at high sub-cooling, since it is found that they delay only very slightly or do not delay at all the formation of the hydrates under these temperature conditions.

[0097] Finally, with a dosage of 3% by weight of composition A, the formation of gas hydrates is delayed by 90 hours, for a sub-cooling of 15 C.

[0098] An advantage is thus clearly established with respect to the prior art, in that the composition according to the present invention results in a longer induction time for greater sub-coolings (15 C.) than that observed with the compositions of the prior art. It is thus possible to work at lower temperatures than the current temperatures while increasing the production output of oil and/or gas.

Example 2

[0099] A study of the kinetic effectiveness of different hydrate-inhibiting compositions is carried out, according to the same protocol as that defined in Example 1.

[0100] The kinetic effectiveness of the hydrate-inhibiting compositions is measured at different sub-coolings (10 C. and 11 C.). The dosage corresponds in this instance to the amount (weight) of hydrate-inhibiting composition introduced into the aqueous phase, with respect to the weight of the water.

[0101] As indicated in Example 1, the induction time is measured from the the moment when the temperature in the cell reaches the temperature of 9.5 C. for a sub-cooling of 10 C. and the pressure in the cell has stabilized. In the absence of formation of hydrate after a certain time, the test is continued by the lowering of the temperature in the cell in order to reach 8.5 C. for a sub-cooling of 11 C. Once the pressure in the cell has stabilized at 8.5 C., the induction time at 8.5 C. is measured. The final point for measuring the induction time corresponds to the start of formation of the hydrates. It is located on the curve of pressure as a function of the time by the point where the pressure begins to fall in the cell (fall in pressure corresponding to the consumption of gas in order to form solid hydrates) and confirmed by an increase in the torque of the stirrer (viscosification of the medium, which becomes loaded with solid) and possibly a very slight exothermic peak on the temperature curve.

[0102] The composition F according to the invention was prepared by mixing the different components, the amounts of which are expressed in Table 4 below.

[0103] Unless otherwise indicated, all the amounts are shown as percentage by weight, with respect to the total weight of the composition.

TABLE-US-00004 TABLE 4 Composition F (invention) Luvicap 55W.sup.(a) 20% Jeffamine SD 2001.sup.(b) 10% 2-Butoxyethanol 70% .sup.(a)vinylpyrrolidone (VP)/vinylcaprolactam (VCap) 1:1 copolymer, sold by BASF .sup.(b)polyalkoxydiamine (di(secondary amine)), sold by Huntsman

[0104] The kinetic effectiveness of the composition F for a sub-cooling of 10 C. and of 11 C. is evaluated for a dosage of 1% by weight. The test composition is introduced into the aqueous phase and the experiment is carried out as described above.

[0105] The kinetic performance of these compositions, characterized by the induction time, was measured twice, and the mean of these measurements is expressed in Table 5 below.

TABLE-US-00005 TABLE 5 Results for a sub-cooling of 10 C. Composition F Composition B (invention) (comparative) Induction time More than 106 hours 86 hours Dose = 1%

[0106] The results above show that, for a sub-cooling of 10 C., the composition of the present invention is more effective than the comparative composition B, which is eliminated for the sub-cooling of 10 C. This is because, in the composition according to the present invention, where the vinylcaprolactam/vinylpyrrolidone copolymer is in a mixture with a di(secondary amine) (composition F), it was not possible in 106 hours to see the appearance of gas hydrates (for a dosage of 1% by weight).

[0107] The test with the composition F was continued for a greater sub-cooling, now of 11 C., according to the protocol described above, at the dose of 1% by weight.

[0108] The kinetic performance of this composition was measured twice, and the mean of these measurements is expressed in Table 6 below.

TABLE-US-00006 TABLE 6 Result for a sub-cooling of 11 C. Composition F (invention) Induction time 25 hours Dose = 1%

[0109] An advantage is thus clearly established with respect to the prior art, in that the composition according to the present invention makes it possible to work at temperatures which are lower than the current temperatures and which correspond to sub-cooling values encountered during production.

Example 3

[0110] The objective of the test of thermal stability with injection is to determine if the hydrate-inhibiting composition can be injected into the line transporting the water/gas/condensate fluids, when they are still hot, without causing deposition or blockage. The test comprises two parts. The hydrate-inhibiting composition F is stored in a closed flask in a climatically controlled chamber at 90 C. for 24 h without the slightest change in appearance being noticed. An aqueous solution comprising 30 g of sodium chloride (NaCl) per litre is prepared and heated to 90 C. on a heating plate. The composition F is injected into the aqueous solution in a few seconds using a syringe, so as to have a concentration of 1% by weight. No appearance of any deposit, gel or suspension over 1 hour is recorded.

Example 4

[0111] The objective of the emulsion test is to determine if the hydrate-inhibiting composition can be injected into the line transporting the water/gas/condensate fluids, without causing, in the downstream plants, problems related to the presence of a stable emulsion. An aqueous solution comprising 30 g of NaCl per litre, and also white spirit in equal proportion, are poured into a flask at ambient temperature. This operation is repeated in two other flasks. The mixtures are supplemented by the addition of 2% by weight of formulation A or F respectively for the second and third flasks. The three flasks are vigorously stirred until a visually homogeneous emulsion is obtained.

[0112] The flasks are observed after 19 seconds, 43 seconds and 1 minute and 2 seconds. In the flask not containing hydrate inhibitor, the emulsion has virtually completely disappeared from 19 seconds. In the flask containing the composition A and the flask containing the composition F, the emulsion is still stable at 43 seconds. At 1 minute and 2 seconds, no emulsion is stable any longer; separation of the two phases is observed. These periods of time during which the emulsions are stable are perfectly acceptable for this use.

Example 5

[0113] The objective of the dehydration test is to determine if the hydrate-inhibiting composition can be separated from the water which contains it, by evaporation of the water. This is because it may be useful to separate the hydrate-inhibiting additive, once the fluids have exited from the region thermally favourable to the hydrates, before discarding the water produced during the extraction from the field, so as to limit the impact on the environment or on the rock receiving the water produced.

[0114] 200 ml of an aqueous solution comprising 0.5% by weight of formulation F and 1 g.l.sup.1 of NaCl are prepared. The solution is placed in a narrow and wide glass container, so as to have a large contact surface area between the solution and the glass. The open container is placed in an oven at 130 C. until only 2 ml of liquid remains. Deposition on the walls is not observed, apart from a few marks containing NaCl crystals, resulting from the evaporation of a few drops of water projected onto the walls during the filling. Likewise, the aqueous solution remains clear. Thus, the hydrate-inhibiting composition F can be separated from the water without risk of deposition in the plants.