Method for Enhanced Oil Recovery Using an Emulsion

Abstract

The present invention relates a method for treating oil well using an emulsion composition. More particularly, the method comprises a step of introducing an emulsion composition in an amount of 0.01% to 100% to pore volume of oil reservoir into the oil well, such that interfacial tension between the oil well and the reservoir reduces to 10.sup.−4 mM/m or below thereby enable removal of oil therefrom.

(No illustrative FIGURE.)

Claims

1.-11. (canceled)

12. An oil recovery method from an oil well, comprising the steps of: introducing an emulsion composition having a dispersed oil-in-water or water-in-oil droplet size of equal to or less than 1 μm and is present in an amount ranging from 0.01 to 100% to a pore volume of an oil reservoir into the oil well, such that interfacial tension between the oil well and the oil reservoir reduces to 10.sup.−4 mN/m or below, thereby enabling removal of oil therefrom; wherein the emulsion composition comprises an aqueous phase present in a range of 0.5 to 40% by weight of the total composition, a non-aqueous phase present in a range of 15 to 90% by weight of the total emulsion composition, a surfactant present in a range of 2 to 60% by weight of total composition, and a compound having chemical structure I present in a range of 1 to 30% by weight of the total emulsion composition,
R.sub.1—CONH—[R.sub.2—NH—R.sub.3].sub.n—HNOC—R.sub.4  (Chemical Structure I) in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are linear, branched or aromatic carbon containing substituents having 2 to 26 carbon atoms and n is an integer in a range of 1 to 100, wherein each of the substituents is selected from the group consisting of an alkyl group, a carbonyl group, a carboxylic group, an amine group, an amide group and combinations thereof; and wherein the emulsion composition is chemically stable and has a low dependency on pH, ionic strength, temperature, type of rocks at oil reservoir, or any combination thereof.

13. The method according to claim 12, further comprising a step of pre-flushing the oil well with seawater in an amount in a range of 0.01 to 10% to the pore volume of the oil reservoir.

14. The method according to claim 13, further comprising a step of introducing a polymeric solution into the oil well, in which the polymeric solution is present in an amount ranging from 0.15 to 100% to the pore volume of the oil reservoir into the oil well.

15. The method according to claim 14, wherein the polymeric solution comprises water and the polymer is selected from the group consisting of polyacylamine or derivatives thereof, xanthan gum, hydroxyethyl cellulose, carboxymethyl cellulose, guar gum and combinations thereof.

16. The method according to claim 15, wherein the polymeric solution has a polymer concentration in a range of 0.01 to 2 w/w % in water.

17. The method according to claim 14, further comprising a step of introducing the oil well with an aqueous solution present in an amount ranging from 0.15% to 200% to the pore volume of the oil reservoir.

18. The method according to claim 17, wherein the aqueous solution is selected from the group consisting of water, treated seawater, brine and combinations thereof.

19. The method according to claim 17, further comprising a step of diluting the emulsion composition to a concentration in a range of 0.1-20 w/w % in water, treated seawater or brines.

20. The method according to claim 12, wherein the emulsion composition further comprises a co-surfactant present in a range of 1% to 30% by weight of the total emulsion composition, in which the co-surfactant is selected from the group consisting of a short-chain surfactant, a short-chain non-ionic surfactant, an alcohol, an amide and combinations thereof.

21. The method according to claim 18, wherein the brine is selected from the group consisting of ammonium chloride, potassium chloride, sodium chloride, sodium formate, potassium chloride, potassium formate, sodium bromide, calcium chloride, calcium bromide and combinations thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0020] Exemplary, non-limiting embodiments of the invention will be disclosed. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

[0021] The term “emulsion” herein refers to microemulsion or nanoemulsion having dispersed oil-in-water or water-in-oil.

[0022] The present invention is an enhanced oil recovery method from an oil well comprising a step of: introducing an emulsion composition in an amount of 0.01% to 100% to pore volume of oil reservoir into the oil well, such that interfacial tension (IFT) between the oil well and the reservoir reduces to 10.sup.−4 mM/m or below thereby enable removal of oil therefrom. In one embodiment, the IFT can be reduced to 10.sup.−6 mN/m.

[0023] The step of introducing the emulsion composition can be conducted by injecting it into an oil well and flooding thereof, such that there is sufficient contact between the emulsion, the oil reservoir, and undesired deposits along the oil well. Advantageously, the composition to seep through rocks or cracks in the oil well as well. Upon sufficient contact, the emulsion adsorbs onto the reservoir surfaces and oil surfaces. It reduces the contact angle and facilitate the reduction in interfacial tension. It shall be noted that further introduction of water therein helps remove excess oils within the pores.

[0024] If necessary, the method comprises a step of pre-flushing the oil well with treated seawater. The seawater used is preferably treated to remove bacteria, fungus, and oxygen. Generally, the step of pre-flushing is conducted before the step of introducing the emulsion composition thereinto. More particularly, the oil well is pre-flushed with treated seawater in an amount of 0.01% to 10% to pore volume of the oil reservoir.

[0025] In accordance to preceding description, the step of introducing the emulsion composition into the oil well may work in association with aqueous solution and/or polymer flooding in different sequences. Aqueous solution flooding herein is also generally known as “water flooding” in the art. Particularly, aqueous solution flooding herein uses water, treated seawater, or brine. The brine used is selected from ammonium chloride, potassium chloride, sodium chloride, sodium formate, potassium chloride, potassium formate, sodium bromide, calcium chloride, calcium bromide and mixtures thereof. On the other hand, polymer flooding herein preferably uses biosynthesized and/or water-soluble polymer. More particularly, the polymeric solution comprises polymer selected from any one or a combination of polyacylamine or derivatives thereof, xanthan gum, hydroxyethyl cellulose, carboxymethyl cellulose, and guar gum.

[0026] In one embodiment, the method comprised of sequential steps: (1) pre-flushing the oil well with treated seawater in an amount of 0.01% to 10% to pore volume of the oil reservoir; (2) introducing a nanoemulsion composition in an amount of 0.01% to 50% to pore volume of oil reservoir into the oil well, such that interfacial tension (IFT) between the oil well and the reservoir reduces to 10.sup.−4 mM/m or below thereby enable removal of oil therefrom; and then (3) introducing the oil well with an aqueous solution in an amount of 0.15% to 100% to pore volume of the oil reservoir.

[0027] In another embodiment, the method comprised of sequential steps: (1) pre-flushing the oil well with treated seawater in an amount of 0.01% to 10% to pore volume of the oil reservoir; (2) introducing a nanoemulsion composition in an amount of 0.01% to 100% to pore volume of oil reservoir into the oil well, such that interfacial tension (IFT) between the oil well and the reservoir reduces to 10.sup.−4 mM/m or below thereby enable removal of oil therefrom; (3) introducing a polymeric solution into the oil well, in which the polymeric solution is in an amount of 0.15% to 100% to pore volume of oil reservoir into the oil well; and then (4) introducing the oil well with an aqueous solution in an amount of 0.15% to 100% to pore volume of the oil reservoir.

[0028] Alternatively, the method comprises an embodiment where the nanoemulsion and the polymer solution are mixed prior to introducing into the oil well. In this embodiment, the method comprised of sequential steps: (1) pre-flushing the oil well with treated seawater in an amount of 0.01% to 10% to pore volume of the oil reservoir; (2) introducing a mixture of nanoemulsion composition and polymer solution in an amount of 0.01% to 100% to pore volume of oil reservoir into the oil well, such that interfacial tension (IFT) between the oil well and the reservoir reduces to 10.sup.−4 mM/m or below thereby enable removal of oil therefrom; (3) introducing an extra dose of polymeric solution into the oil well, in which the polymeric solution is in an amount of 0.15% to 100% to pore volume of oil reservoir into the oil well; and then (4) introducing the oil well with an aqueous solution in an amount of 0.15% to 200% to pore volume of the oil reservoir.

[0029] More particularly, the emulsion composition used is preferably diluted with water, treated seawater, or brine to a predetermined concentration prior to use. The brine used is selected from ammonium chloride, potassium chloride, sodium chloride, sodium formate, potassium chloride, potassium formate, sodium bromide, calcium chloride, calcium bromide and mixtures thereof. The seawater used is preferably treated to remove bacteria, fungus, and oxygen. In the preferred embodiment, the method comprises a step of introducing a nanoemulsion composition having concentration of 0.1-20 w/w % in water into the oil well.

[0030] The emulsion composition used preferably comprises an aqueous phase in 0.5 to 60% by weight of total composition; an non-aqueous phase in 15 to 90% by weight of total composition; a surfactant in 2 to 60% by weight of total composition; and a compound having Chemical structure I in 1 to 30% by weight of total composition,

R.sub.1—CONH—[R.sub.2—NH—R.sub.3].sub.n—HNOC—R.sub.4  (Chemical structure I)

[0031] in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are linear, branched or aromatic carbon-containing substituents having 2 to 26 carbon atoms and n is an integer ranges from 1 to 100, wherein each of the substituents comprises an alkyl group, carbonyl group, a carboxylic group, an amine group, or an amide group.

[0032] Optionally, the emulsion used may further comprised of 1-5 w/w % of biocides selected from glutaraldehyde, terakis-hydroxymethylphosphonium sulfate, n-alkyldimethyl-benzylammonium chloride and mixtures thereof.

[0033] Optionally, the emulsion used may also further comprised of 1-5 w/w % of chelating agents selected from amino trimethylene phosphonic acids, polyhydric alcohol phosphate esters, hexamethylenediaminetetra (methylenephosphonic acid) and mixtures thereof.

[0034] Optionally, the emulsion used may also further comprised of 1-5 w/w % of corrosion inhibitors selected from phosphate esters, amine salts of polycarboxylic acids, quaternary ammonium ammonium salts, quaternary iminium salts, amidoamines, imidazolines, ethoxylated fatty amines, ethoxylated fatty diamines and mixtures thereof.

[0035] Optionally, the emulsion used may also further comprised of 1-5 w/w % of pH buffers, if necessary.

[0036] The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all aspects only as illustrative and not restrictive. The scope of the invention is, therefore indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.