Criteria for Selecting Effective Demulsifier

Emulsions have been the archenemy of the oilfield industries since a long time. It is an issue which is discussed by the oil exploitation companies every now and then. Owing to this big problem, let’s understand what emulsion and demulsification stands for. Emulsion is the process in which fine droplets of one liquid disperse upon a different liquid which does not mix with each other. Solution of this problem is very important so that the further processes can be carried out without any blockage. Thus demulsification comes into picture. Demulsifiers are the breakers of emulsion and are commonly used in the petroleum and crude oil industries. They are applied and removed before the oil goes to the refining process.

The common questions that go around in an oilfield industry are whether the best demulsifier is been chosen? Or whether the demure is optimized properly? Well, we can say that proper selection of demulsifiers can be constantly improved by various trials and tests. The uncertainties in choosing a good demulsifier can be annihilated by pinning down the good properties and other factors that will support demulsification.

Formulation of the Demulsifier

The demulen should be properly formulated so as to ensure good results. The formulations are typical with mixtures of three to four chemistries. It should be done by keeping the properties of oil, which is to be demulsified, in mind. For example a paraffin demulsifier which is a petroleum demulsifier is used to remove the oil/water emulsions and obtain high quality crude and effluent water. The density change due to the demucle action makes the separation easier. The rate and cleanliness of water are also the factors which are considered for choosing a good demulent. The formulator plays the base agent, which is then modified to water or oil based ones. The temperature, mixing ratio and solubility are the other influential factors.

Understanding the Emulsion Causes

In high scale industries it is important to understand the emulsion factors. This helps in selection of an appropriate demulsifier. Factors such as:
1. Droplet size
2. Temperature
3. Water cut
4. Turbulence
5. pH composition

The prior task is to analyze the causes and understand that which factors can and cannot be treated. Like the water cut cannot be controlled but, the temperature can be controlled by increasing the insulating flowlines. The droplet size can be controlled by shearing. This will lead to a better decision making and have good a hold over the demulent usage. Case study and annual report can help in proper optimization of a demulsifier.

Selection Criterion of Demulsifier

The demulate should be selected by keeping the treatment system in mind. Some of the factors that should be kept in mind are:
1  Emulsion retention time
2. The type of emulsion to be treated
3. Water cuts
4.  Heating factors
5. Temperature range for summers and winters
6. Whether the composition is constant or changing

The demulsifier should be changes according to the field conditions. Even the low and high temperature problems can upset the treatment plan. For example, acidizing can cause stable emulsions. The demulsifier dosage should be increased if required. Same demulent or same dose of demulent cannot be preferred for all conditions.
The selection procedure starts with bottle tests. An emulen sample is passed through many centrifuge tubes. Then several demulens are added to these centrifuge tubes in various amounts and the water dropout data is accessed to determine the best candidate. The factors that should be noted during these tests are:

1.Particles at the interface
2. Sedimentation in water
3.Water clarity
4.Rag layer formation
5.Chromium of the emulsion

The concentration and temperature factors are tested and the demulsifier with fastest and cleanest water separation standards are then selected as the best ones.

Mixing and Overdosing

Thorough mixing of the demulent should be done to make it effective enough. A well mixed demulen will instantly mix with the emulsion and migrate to its surrounding water droplets. Demucle slugging should be avoided to prevent formation of high concentration regions and re-emulsification. Using sufficient amount of diluents can make the mixing of the demulen more uniform. Pipes, valves etc can provide enhancement in the persistence of the chemical interface. The mixing should neither be too low for proper mixing nor too severe to cause further tightening of the emulen. Special mixers should be installed. The mixers should be according to the treatment plant like for the crude oil demulsifiers or for the petroleum demulsifiers.

Overdose of the demulen can cause severe problems. It results in the formation of rag layers and worsens the plant cost. Demulsifier control systems should be implanted to increase or decrease the demulen rate according to the condition.

This article has been written by Govind Patel.