Demulsifier composition and method of using same

1. A method of resolving an emulsion of water and crude petroleum oil, the method comprising:

obtaining a crude petroleum oil from a subterranean reservoir;

mixing the crude petroleum oil with a wash water, resulting in a water-in-crude oil emulsion;

adding a demulsifier composition to the water-in-crude oil emulsion to form a treated emulsion, the demulsifier composition comprising: (i) a first nonionic surfactant having a hydrophilic-lipophilic balance (HLB) of less than about 9; (ii) a coupling agent capable of stabilizing the demulsifier composition in the amount of from about 5% to about 40% based on the total weight of the demulsifier composition; (iii) a second nonionic surfactant that is water-soluble or dispersible and is different from the first nonionic surfactant; (iv) at least one nonionic demulsifier comprising a polyethyleneimine alkoxylate, a cross-linked ethylene oxide/propylene oxide copolymer, or combinations thereof; and (v) water; and

separating the crude petroleum oil from the water.

2. The method of claim 1 wherein the adding is accomplished by injecting the demulsifier composition into a crude oil process stream between a well head and a final oil storage tank.

3. The method of claim 1 wherein the adding is accomplished continuously or in batch fashion.

4. The method of claim 1 , further comprising allowing the treated emulsion to stand in a quiescent state for a period of time sufficient to obtain separation of the treated emulsion into distinct layers of water and oil prior to the separating.

5. The method of claim 4 , wherein the allowing the treated emulsion to stand is accomplished in a settling tank.

6. The method of claim 1 wherein the amount of the demulsifier composition added to the water-in-crude oil emulsion is about 10 ppm to 5000 ppm based on the volume of crude oil production.

7. The method of claim 1 , wherein the first nonionic surfactant having an HLB of less than about 9 comprises an alkoxylated alcohol, an alkoxylated alkylphenol, a glycerol ester, a glycol ester, a polyethyleneglycol ester, a polyglycerol ester, a sorbitol ester, an ethylene oxide/propylene oxide copolymer, or a combination thereof.

8. The method of claim 7 , wherein the alkoxylated alcohol is selected from the group consisting of ethoxylated and propoxylated C 6 -C 20 alcohols; and mixtures thereof.

9. The method of claim 8 , wherein said alkoxylated alcohol comprises about 1-6 moles of alkylene oxide per mole of alcohol.

10. The method of claim 1 , wherein the amount of the first nonionic surfactant is about 0.1% to about 35% by weight based on the total weight of the demulsifier composition.

11. The method of claim 1 , wherein the amount of the first nonionic surfactant is about 2% to about 25% by weight based on the total weight of the demulsifier composition.

12. The method of claim 1 , wherein the coupling agent is a water-soluble organic solvent.

13. The method of claim 12 , wherein the water-soluble organic solvent is selected from the group consisting of short chain alcohols with between 1 and 6 carbon atoms; diols with between 1 and 6 carbon atoms; glycerol; alkyl ethers of alkylene glycols with between 1 and 6 carbon atoms; polyalkylene glycols less than 6 kD; and mixtures thereof.

14. The method of claim 1 , wherein from about 2% to about 30% of the at least one nonionic demulsifier is present, based on total weight.

15. The method of claim 1 , wherein the second nonionic surfactant includes an alkoxylated alcohol, ethylene oxide/propylene oxide copolymers, and/or alkoxylated alkylphenol having an HLB greater than about 10.

16. The method of claim 1 , wherein from about 2% to about 25% of the second nonionic surfactant is present, based on weight.