Aromatic sulfonic acid demulsifier for crude oils

Details Aromatic sulfonic acid demulsifier for crude oils Aromatic sulfonic acid demulsifier for crude oils

2002-10-01

2003-07-29

Metzmaier, Daniel S. (Department: 1712)

Colloid systems and wetting agents; subcombinations thereof; pro

Compositions containing an agent for breaking ; processes of...

Continuous liquid phase colloid system and discontinuous...

C210S708000, C210S748080, C204S563000, C204S567000

Reexamination Certificate

active

06599949

ABSTRACT:

FIELD OF THE INVENTION
The invention is related to crude oil demulsification and aromatic sulfonic acid demulsifier formulations.
BACKGROUND OF THE INVENTION
Produced crude oils contain varying amounts of water and inorganic salts like chlorides, sulfates and carbonates of Group Group I and Group II elements. The presence of salts present difficulties during crude oil processing such as corrosion of the oil processing equipment. In order to mitigate the effects of corrosion resulting from the presence of salts, it is advantageous to reduce the salt concentration to the range of 3 to 5 ppm by weight of the crude oil. This concentration corresponds to approximately 2 pounds of inorganic salts per 1,000 barrels of crude oil. One method to remove salts from a crude oil is to solubilize the salts in water and remove the water from the crude oil. Generally the water present in crude oil is either phase separated water or emulsified water. Emulsified water is water that is dispersed in oil as a water-in-oil emulsion. Demulsification is the method of removing the dispersed water from the oil. Generally when crude oil is produced from subterranean environments, salts like chlorides, sulfates and carbonates of Group I and Group II elements are dissolved in the water phase. Water with dissolved salts is generally called brine. Demulsification results in removal of water and a reduction in salt concentration. The value of crude oil is enhanced by reducing the levels of salts and water in the crude oil.
Among the crude oil demulsification methods in use today, electrostatic demulsification, gravity separation, centrifugation and hydrocyclone-assisted separation are frequently used. Wash water is added until the crude oils water content is in the range of 4 to 15 vol. %, and a chemical demulsifier formulation is added so that the oil and the aqueous phases can be separated by separation methods known in the art. As used herein, a crude oil emulsion is a mixture of crude oil and a suspended aqueous phase, which may be in the form of droplets stabilized by naturally occurring surface-active compounds in the crude oil. Additionally, inorganic solids such as clay or silica can also contribute to emulsion stabilization.
In electrostatic separation, dispersed brine droplets coalesce in between electrodes located in the oil phase. The coalesced aqueous droplets then settle below the oleaginous crude oil phase. The separation can occur in a separator where effluent brine can be removed. Treated crude is removed from the upper part of the separator. Intermediate between the oil phase and the brine phase is a “rag” layer comprising a stable emulsion and solids. The rag layer may remain in the demulsifier vessel or it may be removed therefrom for storage or further processing.
Effective demulsification requires addition of a chemical demulsifier additive to the wash water or to the crude prior to application of an electrostatic field or centrifugal force to the crude oil emulsion. Crude oils that contain high amounts of asphaltenes and naphthenic acids are generally called heavy crude oils and are difficult to demulsify. These crude oils require specifically tailored demulsifier additives for demulsification to be effective. Many demulsifier additives have phenolic groups in their chemical structure. In some cases, crude oil demulsifier additives that do not contain phenolic groups and are effective on crude oils containing asphaltenes and naphthenic acids are desired.
SUMMARY OF THE INVENTION
In one embodiment, the invention is a crude oil demulsifier formulation comprising:
about 10 wt. % to about 80 wt. % based on the weight of the chemical demulsifier formulation of an additive having the formula:
R—Ar—SO
3
H
where R is an alkyl group containing at least 16 carbons and at least one branch of an alkyl group, Ar is an aromatic group with at least two 6-ring aromatic groups and
about 90 wt. % to about 20 wt. % based on the weight of the chemical demulsifier formulation of a co-additive selected from the group consisting of dipropylene monobutyl ether, aromatic naphtha, isoparaffinic solvent, cycloparaffinic solvent, aromatic solvent, diethylene glycol monobutyl ether, benzyl alcohol, and mixtures thereof.
In another embodiment, the invention is a process to demulsify a crude oil emulsion comprising:
adding to a crude oil emulsion a chemical demulsifier formulation comprising:
about 10 wt. % to about 80 wt. % based on the weight of the chemical demulsifier formulation of an additive having the formula:
R—Ar—SO
3
H
where R is an alkyl group containing at least 16 carbons and at least one branch of an alkyl group, Ar is an aromatic group with at least two 6-ring aromatic groups and
about 90 wt. % to about 20 wt. % based on the weight of the chemical demulsifier formulation of a co-additive selected from the group consisting of dipropylene monobutyl ether, aromatic naphtha, isoparaffinic solvent, cycloparaffinic solvent, aromatic solvent, diethylene glycol monobutyl ether, benzyl alcohol, and mixtures thereof.
separating said emulsion into a plurality of layers, and optionally, recovering demulsified crude oil.
DETAILED DESCRIPTION OF THE INVENTION
Applicants' discoveries are based on the fact that adding a chemical demulsifier formulation can enhance brine droplet coalescence in crude oil. The chemical additive in the formulation is a branched aromatic sulfonic acid of a certain structure. Application of electrostatic fields, centrifugation or hydrocyclone treatment enhances the process of coalescence of dispersed brine droplets. For a chemical demulsifier additive which, itself, is an acid to be effective as a demulsifier of an acid containing crude oil is unexpected because acids are known to those skilled in the art to be emulsifiers.
The combination of the additive and co-additive provides a synergistic effect and enhances demulsification performance. The combination of the aromatic sulfonic acid additive and co-additive comprises the demulsifier formulation. Co-additives selected from the group consisting of dipropylene monobutyl ether, aromatic naphtha, isoparaffinic solvent, cycloparaffinic solvent, aromatic solvent, diethylene glycol monobutyl ether, benzyl alcohol, and mixtures thereof are examples where synergistic behavior can be obtained.
While the invention can be practiced with any crude oil containing brine, it is preferably practiced with heavy or waxy crude oils. Heavy or waxy crude oils have one or more of the following characteristics:
The crude oil has an API gravity ranging from about 5 to about 30.
The crude oil has a high naphthenic acid concentration; characterized by a high “TAN” number (the TAN number represents the number of milliequivalents of potassium hydroxide required to neutralize 1 gram of crude oil).
The fraction of the crude oil soluble in n-heptane ranges from about 0.5 wt. % to about 15 wt. %.
The invention can also be practiced on crude oil distillates, synthetic oils for example, silicone oils and vegetable or animal derived oils.
Chemical demulsifier additive useful in the practice of the invention has the structure:
R—Ar—SO
3
H
Preferably, the chemical demulsifier additive has an alkyl group R that is at least 16 carbons. The alkyl group is preferably branched. A “Y” branched alkyl group is more preferred. The “Y” branch may have further branching. The aromatic group, Ar, has at least two 6-ring aromatic groups. Preferably the rings are fused. Cycloalkyl groups can be attached to the aromatic rings. The cycloalkyl rings have at least 6 carbons and can be fused or pendant to the aromatic rings. The SO
3
H group can be attached to any position on the aromatic rings. Preferably at least 1 SO
3
H group is present.
The chemical demulsifier additive is used in combination with a co-additive. Co-additives useful in the practice of this invention include diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, aromatic naphtha, isoparaffinic solvent, cycloparaffinic solvent, aromatic solvent, oxygenated solvents, such as diethylene monobutyl ether be

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