Process for the removal of deposits from an oil or gas well, and/or from the surface structures, and/or from the equipment connected therewith, and/or from hydrocarbon bearing formations

Abstract

Process for the removal of deposits from an oil or gas well, and/or from surface structures, and/or from the equipment connected therewith, and/or from hydrocarbon-bearing formations, comprising:—injecting at least one oil-in-water nanoemulsion into said oil or gas well, and/or surface structures, and/or equipment connected therewith, and/or hydrocarbon bearing formations; leaving said nanoemulsion in said oil or gas well, and/or surface structures, and/or equipment connected therewith, and/or hydrocarbon bearing formations, for a predetermined time.

Claims

1. A process for removing deposits, the process comprising: injecting at least one oil-in-water nanoemulsion into at least one space selected from the group consisting of an oil well, a gas well, a surface structure, and a hydrocarbon bearing formation; and leaving the at least one nanoemulsion in the space for from 1 hour to 10 days, wherein said oil-in-water nanoemulsion has a dispersed phase consisting essentially of an oil and a dispersing phase consisting essentially of water and at least one surfactant, and wherein said oil-in-water nanoemulsion is prepared according to a process comprising diluting a homogeneous water/oil mixture (1) in a dispersing phase consisting of water to which at least one surfactant (2) has been added, wherein: the homogeneous water/oil mixture (1) comprises water, in an amount ranging from 65% by weight to 99.9% by weight with respect to a total weight of the mixture (1), and at least two surfactants (1) having a different hydrophilic-lipophilic balance from one another, in amounts such that the mixture (1) is homogenous; an interface tension of the homogeneous water/oil mixture (1) is lower than or equal to 1 mN/m; the surfactants (1) and (2) are selected from the group consisting of a non-ionic surfactant, an anionic surfactant and a polymeric surfactant; and amounts of said dispersing phase and of said surfactant (2) are such that the oil-in-water nanoemulsion has a hydrophilic-lipophilic balance higher than that of the homogeneous water/oil mixture (1).

2. The process of claim 1, wherein said process is suitable for removing organic deposits.

3. The process of claim 1, wherein said oil-in-water nanoemulsion has a dispersed phase consisting of an oil and a dispersing phase consisting of water and at least one surfactant.

4. The process of claim 3, the dispersed phase is distributed in the dispersing phase in the form of droplets having a diameter ranging from 10 nm to 500 nm.

5. The process of claim 4, wherein the dispersed phase is distributed in the dispersing phase in the form of droplets having a diameter ranging from 15 nm to 200 mn.

6. The process of claim 1, wherein said oil-in-water nanoemulsion has a hydrophilic-lipophilic balance value higher than or equal to 9.

7. The process of claim 6, wherein said oil-in-water nanoemulsion has a hydrophilic-lipophilic balance value ranging from 10 to 16.

8. The process of claim 1, wherein, in said oil-in-water nanoemulsion, the dispersed phase is distributed in the dispersing phase in the form of droplets having a specific area (area/volume) ranging from 6000 m.sup.2/l to 300000 m.sup.2/l.

9. The process of claim 8, wherein, in said oil-in-water nanoemulsion, the dispersed phase is distributed in the dispersing phase in the form of droplets having a specific area (area/volume) ranging from 15000 m.sup.2/l to 200000 m.sup.2/l.

10. The process of claim 1, wherein surfactants are present in said oil-in-water nanoemulsion in an amount ranaing from 0.1% by weight to 20% by weight with respect to a total weight of said oil-in-water nanoemulsion.

11. The process of claim 10, wherein surfactants are present in said oil-in-water nanoemulsion in an amount ranging from 0.25% by weight to 12% by weight with respect to the total weight of said oil-in-water nanoemulsion.

12. The process of claim 1, wherein said oil is present in said oil-in-water nanoemulsion in an amount ranging from 2% by weight to 20% by weight with respect to a total weight of said oil-in-water nanoemulsion.

13. The process of claim 12, wherein said oil is present in said oil-in-water nanoemulsion in an amount ranging from 3% by weight to 15% by weight with respect to a total weight of said oil-in-water nanoemulsion.

14. The process of claim 3, wherein a surfactant selected from the group consisting of a non-ionic surfactant, an ester of a fatty acid of sorbitan, a polymeric surfactant, and mixtures thereof is present in said dispersing phase.

15. The process of claim 3, wherein said oil is selected from the group consisting of an aromatic hydrocarbon, a linear hydrocarbon, a branched hydrocarbon, a cyclic hydrocarbon, and mixtures thereof.

16. The process of claim 3, wherein said water is selected from the group consisting of a demineralized water, salt water, and a mixture thereof.

17. The process of claim 1, wherein said oil-in-water nanoemulsion has a pH ranging from 7 to 13.

18. The process of f claim 17, wherein said oil-in-water nanoemulsion has a pH ranging from 8 to 12.

19. The process of claim 1, wherein said oil-in-water nanoemulsion is injected into the space at a temperature ranging from 5° C. to 90° C.

20. The process of claim 19, wherein said oil-in-water nanoemulsion is injected into the space at a temperature ranging from 15° C. to 80° C.

21. The process of claim 19, wherein said oil-in-water nanoemulsion is left in the space for a time ranging from 8 hours to 2 days.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 (Samples A) shows samples at the starting moment (time=0) containing asphaltene and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right) as described in Example 2.

(2) FIG. 1 (Samples B) shows the above samples—maintained for 24 hours (time=24 hours) at room temperature (25° C.) under static consitions—containing asphaltene and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right) as described in Example 2.

(3) FIG. 2 (Samples A) shows the samples, after 24 hours, at room temperature (25° C.) and under static conditions, containing clogging emulsion and oil-in-water nanoemulsion with increasing concentrations of xylene (left to right) as described in Example 3.

(4) FIG. 2 (Samples B) shows the above samples ater 24 hours, at room temperature (25° C.) subjected to hand vibration and left to settle for 1 hour at room temperature (25° C.), containing clogging emulsion and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right) as described in Example 3.

(5) FIG. 3 shows the above samples (a), (b) and (c) (from left to right) maintained for 24 hours, at room temperature (25°C.), under static conditions. It can be seen that the use of the oil-in-water nanoemulsion allows a good removal of the asphaltene which is solubilized forming a black fluid phase on the surface as described in Example 4.

(6) Some illustrative and non-limiting examples are provided for a better understanding of the present invention and for its embodiment.

EXAMPLE 1

(7) (1) Preparation of the Precursor of the Oil-in-Water Nanoemulsion

(8) 0.121 g of Atlox 4913 (polymethylmethacrylate-polyethyleneglycol graft copolymer of Uniqema), 0.769 g of Span 80 (sorbitan monooleate of Fluka), 3.620 g of Glucopone 600 CS UP (alkyl polyglucoside of Fluka, 50% solution in water) and 6.150 g of xylene, were poured into a 50 ml beaker equipped with a magnetic stirrer, and the whole mixture was kept under stirring until complete dissolution. When the dissolution was complete, 4.340 g of deionized water were added and the whole mixture was kept under bland stirring for 2 hours, obtaining 15 g of a precursor having a HLB equal to 12.80.

(9) Said precursor was left to stabilize for 24 hours at room temperature (25° C.), before being used.

(10) (2) Preparation of the Oil-in-Water Nanoemulsion

(11) 0.325 g of Glucopone 215 CS UP (alkyl polyglucoside of Fluka, 60% solution in water) and 2.236 g of deionized water, were poured into a 20 ml glass vial, and the whole mixture was maintained under stirring until complete dissolution.

(12) When the dissolution was complete, 2.439 g of precursor obtained as described above, were added and the whole mixture was kept under bland stirring, for 2 hours, obtaining a nanoemulsion having a transparent-translucid appearance, a HLB equal to 13.80 and a xylene concentration equal to 20% by weight with respect to the total weight of the nanoemulsion.

(13) Said nanoemulsion was used for obtaining, through dilution with deionized water, nanoemulsions at different concentrations (% by weight) of xylene indicated in Table 1.

(14) TABLE-US-00001 TABLE 1 Oil-in-water Total surfactants Water Xylene nanoemulsion (% weight)* (% weight)* (% weight)* (a) 1.2 96.8 2 (b) 2.4 93.6 4 (c) 3.6 90.4 6 (d) 4.8 87.2 8 (e) 6.0 84.0 10 (f) 12 68.0 20 *= % weight with respect to the total weight of the nanoemulsion.

(15) The nanoemulsions obtained as described above, have droplets of dispersed phase (xylene) having dimensions ranging from 40 nm to 60 nm, a polydispersity index lower than 0.2 and are stable for over six months.

EXAMPLE 2

(16) The following samples were prepared in order to evaluate the removal capacity of asphaltene deposits of the nanoemulsion in accordance with the present invention.

(17) Samples of 0.6 g of asphaltene were crushed manually in a mortar and sieved by means of a 4 mm-mesh aluminium sieve. The samples thus prepared were treated using nanoemulsions at different concentrations of xylene, obtained as described above and indicated in Table 1.

(18) For the above purpose, 5 g of the oil-in-water nanoemulsion to be tested and whose characteristics are indicated in Table 2, were added to each sample. A sample was prepared, for comparative purposes, to which 5 g of deionized water were added (sample 1 of Table 2).

(19) TABLE-US-00002 TABLE 2 Xylene conc. in oil-in-water Amount of xylene with nanoemulsion respect to asphaltene nanoemulsion SAMPLE (% weight).sup.(1) (% weight).sup.(2) pH 1 0 0 7.53.sup.(3) (comparative) 2 2 16.6 7.45 3 4 33.3 8.53 4 6 50.0 8.74 5 8 66.6 9.02 6 10 83.3 9.24 7 20 166.6 9.66 .sup.(1)= % weight with respect to the total weight of the nanoemulsion; .sup.(2)= % weight with respect to the total weight of the asphaltene contained in the sample; .sup.(3)= pH of the deionized water as such.

(20) FIG. 1 (Samples A) shows samples at the starting moment (time=0) containing asphaltene and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right). It can be seen that the oil-in-water nanoemulsions are capable, even at low concentrations of xylene (i.e. 4%), to come into contact with the asphaltene and to start the formation of a black fluid phase on the surface, whereas, in case of the use of water alone, the asphaltene begins to form an agglomerate on the surface.

(21) FIG. 1 (Samples B) shows the above samples—maintained for 24 hours (time=24 hours) at room temperature (25° C.) under static conditions—containing asphaltene and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right). It can be seen that the use of the oil-in-water nanoemulsion allows, even at low concentrations of xylene (i.e. 4%), a good removal of the asphaltene which is solubilized, forming a black fluid phase on the surface whereas, in case of the use of water alone, the asphaltene forms an agglomerate on the surface.

EXAMPLE 3

(22) The following samples were prepared in order to evaluate the removal capacity of clogging emulsions of the nanoemulsion in accordance with the present invention.

(23) Samples of 1 g of clogging emulsion comprising 80% of formation water and 20% of gasoline rich in highly unstable asphaltenes, coming from the oil field of Pineto (Teramo), were treated using nanoemulsions at different concentrations of xylene, obtained as described above and indicated in Table 1.

(24) For the above purpose, 5 g of the oil-in-water nanoemulsion to be tested, whose characteristics are indicated in Table 3, were added to each sample. For comparative purposes, a sample was prepared to which 5 g of deionized water were added (sample 1 of Table 3)

(25) TABLE-US-00003 TABLE 3 Xylene conc. in Amount of xylene with oil-in-water respect to clogging nanoemulsion emulsion nanoemulsion SAMPLE (% weight).sup.(1) (% weight).sup.(2) pH 1 0 0 7.53.sup.(3) (comparative) 2 2 10 7.45 3 4 20 8.53 4 6 30 8.74 5 8 40 9.02 6 10 50 9.24 7 20 100 9.66 .sup.(1)= % weight with respect to the total weight of the nanoemulsion; .sup.(2)= % weight with respect to the total weight of the clogging emulsion contained in the sample; .sup.(3)= pH of deionized water as such.

(26) FIG. 2 (Samples A) shows the samples, after 24 hours, at room temperature (25° C.) and under static conditions, containing clogging emulsion and oil-in-water nanoemulsion with increasing concentrations of xylene (left to right). It can be seen that the use of the oil-in-water nanoemulsion allows, even at low concentrations of xylene (i.e.4%), a good removal of the clogging emulsion which is solubilized forming a black fluid phase on the surface whereas, in the case of the use of water alone, the asphaltene forms an agglomerate on the surface.

(27) FIG. 2 (Samples B) shows the above samples after 24 hours, at room temperature (25° C.) subjected to hand vibration and left to settle for 1 hour at room temperature (25° C.), containing clogging emulsion and oil-in-water nanoemulsion with increasing concentrations of xylene (from left to right). It can be seen that the use of the oil-in-water nanoemulsion allows, even at low concentrations of xylene (i.e.4%), a good removal of the clogging emulsion which is solubilized forming a black fluid phase on the surface whereas, in the case of use of water alone, the asphaltene agglomerate remains on the surface.

EXAMPLE 4

(28) The following samples were prepared in order to evaluate the removal capacity of asphaltene deposits of the nanoemulsion in accordance with the present invention, with respect to the use of solvent.

(29) Samples of 0.6 g of asphaltene were manually crushed in a mortar and sieved by means of a 4 mm-mesh aluminium sieve.

(30) The samples thus prepared were treated by adding: (a) 5 g of the nanoemulsion at 10% of xylene obtained as described in Example 1; (b) 0.5 g of xylene and 4.5 g of deionized water, in succession; (c) 4.5 g. of deionized water and 0.5 g of xylene, in succession.

(31) FIG. 3 shows the above samples (a), (b) and (c) (from left to right) maintained for 24 hours, at room temperature (25° C.), under static conditions. It can be seen that the use of the oil-in-water nanoemulsion allows a good removal of the asphaltene which is solubilized forming a black fluid phase on the surface.

(32) If xylene and water are added, in succession, a lower effect is observed: the walls are in fact dirty and the asphaltene does not form a well-separable black fluid phase on the surface.

(33) If water and xylene are added, in succession, a very low effect is observed: the asphaltene, in fact, remains in the form of a very viscous fluid.