Emulsion is a stable heterogeneous mixture of two or more immiscible liquids, one dispersed in the other, in the form of microscopically visible droplets.
Emulsion problems are quite common in oil production and desalting systems, and usually have to be chemically treated to meet specifications for transportation and refining.
Normally, formation water is emulsified in the produced crude (water-in-oil emulsion). In addition to the formation water, natural emulsifying agents such as organic acids, asphaltenes, resins, naphthenic acids, finely divded solids and inorganic salys maybe present. The emulsion is formed near the wellbore where the liquids are forced through small formation openings at high velocity or when released gas bubbles through oil and water. It may also be formed in the refinery between condensed sour water and crude frateions.
The stability of an emulsion is increased by:
l The intensity of agitation (shearing stress—main factor)
l High viscosity (increased coalescence time)
l High specific gravity (heavier oil)
l Age (emulsion equilibrium) decrease in water content. ( Hence, the more water removed, the more difficult to remove the residual water)
l Decrease in temperature
l Pressure drop over valves
A demulsifier is a surface agent acting in the interface between oil and water, competing with the naturally occurring emulsifying agents. In order to act satisfactorily it is important that the demulsifier move quickly to the interface, break the skin which forms between the water droplet an oil, coagulate droplets to bigger droplets and water-wet particles present.
Coagulation droplets and particles can then separate from the oil.
In today’s production systems with high flow rates and short residence time, it is particularly important to achieve rapid coagulation and water separation from the crude. Even though some systems have long residence time, rapid dropping of the water is desired high water cut is found.
Demulsifier formulas can be highly specific to particular areas, formations, or even well. In order to optimize an effective demulsifier for a particular application, a series of tests with different chemicals are normally performed on fresh stable emulsion samples.
Some formulations have very wide applicability, but may not be as effective as a formulation which has been custom designed for the specific emulsion problem.
Products (www.deshi-chem.com)
This series of products are high polymers polymerized initiator including polyamine, propylene glycol, stearyl alcohol, and resin with PO and EO. Some of the products are polymerized in crosslinking with epoxy chloropropane or isocyanate or in auto-polymerizing of unsaturated substances.
DESHI CHEM provides a wide range of demulsifer formulations for tough oilfield emulsion problems. We have developed more than 80 kinds of demulsifers to meet the requirements of different situations. The catalog doesn’t list all the demulsifier products.
There are two major categories of demulsifiers, oil soluble and water soluble. Oil soluble product is a perfect blending of polymer compounds polyamines, propylene glycol, octadecadienoic alcohol, and propylene oxide, ethylene oxide in aromatic solvent. It is intended to effectively separate formation water from emulsion in crude oil. Water soluble product uses water as the solvent and it is intended to effectively separate oil from treated water.
Answer to some common questions
1. Will higher treating temperatures always give better oil/water separation?
Not always. Higher temperatures usually help, but in some cases – particularly where very light oils or condensates carry waxes – additional heat has been seen to give negative results.
2. Will demulsifier treatment interfere with bactericide, scale inhibitor, or corrosion
Only in extremely rare cases.
3. Once the proper dumulsifier is found for a given crude, can I expect it to work for the life of the production?
In some cases, the same formulation has been effective for tens of years. There exist those miserable systems, however, which change so frequently that the dumulsifier may have to be reevaluated every few days to weeks. These are normally new wells, and they may“ clean up” after producing for some months.
4. What is the single most common reason that a demulsifier stops functioning in a system?
Chemical injection has been interrupted, or has dropped below the minimum effective treating level. The reasons include gas locking of chemical pumps, plugged filters, loss of power to chemical pump, plugged injection lines, leaking check valves, an- in some parts of the world- sabotage.
