Demulsification is a general term used to describe the separation of water from crude oil. As crude oil is produced from a reservoir it tends to become mixed with either natural formation water or mixed formation and injection water. This produced mixture of crude oil and water is termed an oil and water emulsion. It is critical to topsides process operations that the crude oil is efficiently and quickly separated from the water to allow dry oil to be exported and clean water to be discharged within consent, thus maximising crude oil value and minimising operating costs.

Typically the emulsions formed are water in oil with the continuous phase being oil and the dispersed phase being water.

The severity of the emulsion formed and thus the ease at which it can be broken is dependant on many factors including:

physical and chemical properties of the crude oil

production temperature

distance between reservoir and topsides

degree of agitation experienced between reservoir and separator, turbulent flow

presence of solids (sand, clay, bacteria, scale, asphaltenes, corrosion product, napthenates) and / or natural surfactants     which act to stabilise the emulsion

The most common method of breaking emulsions is with the use of demulsifying / desalting chemicals.

Demulsifying / desalting chemicals tend to act on the emulsion by:

flocculation of the oil droplets

dropping of the water

coalescence of the water droplets

The speed and efficiency at which this occurs can be improved by process equipment design and operating conditions e.g. increasing the temperature, separator design etc.

Demulsifier Selection and Application
Demulsifiers are generally injected on a continuous basis upstream of the 1st stage production separator but in certain circumstances they can be injected subsea.

Demulsifier selection is best performed on live crude oil thus the selection process must be performed in the field and is generally performed using the “bottle test” method. Using this method numerous base chemicals can be tested on fresh emulsions and at the exact operating conditions thus a product can be formulated which is specific to the field and the emulsion. As field conditions change over its lifetime it is essential to optimise demulsifier performance on a regular basis.

Glexoil can provide  a range of demulsifiers  that consist mainly of complex blends of various intermediates formulated to produce a definitive finished product tailored made to aid the separation of crude oil and produced water at the best optimum dose.