Method for inhibiting water permeation in an extraction well of a hydrocarbon oil from an underground reservoir

Abstract

The present invention relates to a composition for inhibiting water permeation in an extraction well of a hydrocarbon oil from an underground reservoir which comprises injecting into said reservoir at least one polymerizable composition comprising: at least one hydrophilic monomer, at least one hydrophilic initiator of radical polymerization with thermal activation (hydrophilic initiator), at least one lipophilic initiator of radical polymerization with thermal activation (lipophilic initiator). The present invention also relates to the polymerizable compositions that can be used in said method.

Claims

1. A polymerizable composition for injection into an underground reservoir of hydrocarbon oil, said composition comprising: at least a first monomer selected from an acrylic monomer or a methacrylic monomer; and at least a second monomer comprising at least one ethylene unsaturation and at least one polyoxoethylene chain; at least one hydrophilic initiator of radical polymerization with thermal activation (hydrophilic initiator) having a temperature T.sub.1/2 (10 h) in water within the range of 50-150° C., at least one lipophilic initiator of radical polymerization with thermal activation (lipophilic polymerization initiator) having a temperature T.sub.1/2 (10 h) in benzene within the range of 50-150° C., said composition being capable apt to form polymers in situ in contact with reservoir water, wherein the initiator is hydrophilic if its distribution coefficient between water and 1-octanol is less than zero, and the initiator is lipophilic if its distribution coefficient between water and 1-octanol is greater than zero.

2. The polymerizable composition according to claim 1 wherein the total concentration of said at least one hydrophilic initiator and said at least one lipophilic initiator is within the range of 0.006-1.00% by weight with respect to the overall weight of said at least one hydrophilic monomer.

3. The polymerizable composition according to claim 1, wherein said at least one lipophilic initiator is present in a concentration within the range of 0.005-0.500% by weight with respect to the overall weight of said at least one hydrophilic monomer.

4. The polymerizable composition according to claim 1, wherein said at least one hydrophilic initiator is present in a concentration within the range of 0.001-0.100% by weight with respect to the overall weight of said at least one hydrophilic monomer.

5. The polymerizable composition according to claim 1, wherein the weight ratio between the hydrophilic initiator and the lipophilic initiator present in the polymerizable composition is within the range of 95:5 to 5:95.

6. The polymerizable composition according to claim 1, wherein said polymerizable composition comprises at least one crosslinking compound.

7. The polymerizable composition according to claim 6, wherein the at least one crosslinking compound is selected from the group consisting of N,N′-methylene-bis-acrylamide, ethyleneglycol-dimethacrylate, divinylbenzene, poly(ethyleneglycol)diacrylate, 1,4-butandiol diacrylate, trimethyl-propane triacrylate, 1,4-bis(4-vinylphenoxy)butane and bis(2-methacryloyl)-oxyethyl disulfide.

8. The polymerizable composition according to claim 1, wherein said polymerizable composition comprises at least one surfactant.

9. The polymerizable composition according to claim 1, wherein said polymerizable composition polymerizes forming a hydrogel.

10. The polymerizable composition according to claim 1, wherein said second monomer has the following formula (I)
CH.sub.2═CR.sub.1—CO—X—(CH.sub.2CH.sub.2O).sub.nR.sub.2  (I) wherein: R.sub.1 is H or CH.sub.3; R.sub.2 is H, OH, C.sub.1-C.sub.4 alkyl, C.sub.1-C.sub.4 alkoxy, or an acrylate group COCR.sub.3═CH.sub.2 wherein R.sub.3 is H or CH.sub.3, X is O or NH; n is an integer within the range of 1-500.

11. The polymerizable composition according to claim 1, wherein said first monomer is selected from acrylic acid and methacrylic acid.

12. The polymerizable composition according to claim 1, further including a liquid carrier.

13. The polymerizable composition according to claim 12, wherein the liquid carrier is selected from the group consisting of water, tetrahydrofuran (THF), ethanol, and acetone.

14. The polymerizable composition according to claim 12, wherein the liquid carrier is in a quantity within the range of 20-70% by weight with respect to the total weight of the hydrophilic monomers.

15. The polymerizable composition according to claim 13, wherein the liquid carrier is in a quantity within the range of 20-70% by weight with respect to the total weight of the hydrophilic monomers.

Description

EXAMPLES

(1) Preparation of the Polymerizable Compositions

(2) Polymerizable compositions according to the present invention were prepared using the following ingredients:

(3) a) a mixture of hydrophilic monomers composed of methacrylic acid (AMA), as main monomer, and 2-hydroxyethyl methacrylate-PEG (HEMA-PEG), as comonomer (molecular weight (Mw) of HEMA-PEG about 2000 Da; average value of n in general formula (I) equal to 45; salification degree of HEMA-PEG equal to about 100%);

(4) b) 4,4′-azobis(4-cyanovaleric acid) as hydrophilic polymerization initiator;

(5) c) benzoyl peroxide as lipophilic polymerization initiator;

(6) d) bisacrylamide as crosslinking agent.

(7) The relative quantities of main monomer and comonomer with respect to the total weight of the mixture of hydrophilic monomers are: 75% AMA, 25% HEMA-PEG.

(8) The polymerizable compositions were prepared by first mixing the monomer and comonomer together, and subsequently adding the hydrophilic and lipophilic initiators and crosslinking agent to the resulting mixture.

(9) Polymerization Tests

(10) In order to verify the behaviour of the polymerizable compositions under conditions close to those of the reservoir, each composition was subjected to two separate polymerization reactions, respectively in the presence of:

(11) (i) saline water (distilled water containing Na′ (34 g/l), Ca.sup.++ (5.8 g/l), Mg.sup.++ (0.6 g/l)) ions;

(12) (ii) water/oil mixture (dispersion) at 50% by weight.

(13) The tests were carried out by pouring the polymerizable composition into a test-tube containing saline water or a water/oil mixture kept at a temperature of 85° C.

(14) The tests in water showed the capacity of the polymerizable compositions according to the present invention of polymerizing until the formation of a hydrogel.

(15) During the tests in water, the time was also measured, during which the composition polymerizes forming the hydrogel (gelation time).

(16) The tests in a water/oil mixture, on the other hand, showed that the polymerizable compositions do not substantially form hydrogels in contact with an oil.

(17) The chemical composition of the polymerizable compositions and the results of the tests are indicated in Table 1 below.

(18) TABLE-US-00001 TABLE 1 Mixture Formation hydrophilic Total Ratio Lip of hydrogel Composition monomers AMA/ Crosslinking concentration In./. Gelation time in water/oil nr. HEMA-PEG.sup.1 agent.sup.2 initiators.sup.2 Hydr. In.sup.3 in water mixture S46 75/25 0.35 0.05 90/10 5 hrs 16 min NO S50 75/25 0.35 0.025 70/30 >8 hours NO S51 75/25 0.35 0.025 60/40 >8 hours NO .sup.1AMA/HEMA-PEG weight ratio in the mixture of hydrophilic monomers .sup.2weight percentage with respect to the weight of the mixture of hydrophilic monomers .sup.3lipophilic initiator (Lip. In.)/hydrophilic initiator (Hydr. In.) weight ratio .sup.1 AMA/HEMA-PEG weight ratio in the mixture of hydrophilic monomers .sup.2 weight percentage with respect to the weight of the mixture of hydrophilic monomers .sup.3 lipophilic initiator (Lip. In.)/hydrophilic initiator (Hydr. In.) weight ratio

(19) The tests effected showed that the polymerizable compositions according to the present invention selectively polymerize in the presence of water, whereas they are inactive in the presence of oil.