Methods for dehydrating crude oil

Crude oil dehydration can first be carried out at the oil field; thereafter, it is left to stand in storage tanks until its water content drops below 1%, after which it is sent to the atmospheric and vacuum distillation units where electrical desalination is used to further reduce the water content to below 0.3%. Finally, it enters the distillation unit.

Is heating required for static dehydration, and to what temperature? For example, if it contains 10% water, how long will it take for the water content to drop below 1%? Could you please provide a detailed explanation? Thank you! !

During the desalination and dewatering of crude oil, in order to break down the emulsion, the four methods mentioned above—heating, addition of demulsifiers, electrical treatment, and mixing—are widely used simultaneously with sedimentation; usually, several of these methods are employed at the same time. This approach of using several methods simultaneously to treat crude oil emulsions ensures rapid and effective separation of the emulsion. Oilfield dehydration makes use of a so-called \"pipeline demulsification\" process: in the presence of a demulsifier, the hydraulic effects generated by the flow of emulsified crude oil in the pipelines are utilized to successfully combine these effects with the sedimentation that occurs as a result of the parallel flow of the liquids within the pipelines. During electrical desalination in refineries, since the crude oil stays in the unit for only a short time, deep dehydration must be ensured in order to achieve thorough desalination. At this time, a combination of heating, the addition of demulsifiers, electric fields, and gravity sedimentation is commonly used. (2) Thermochemical demulsification: Thermochemical demulsification is primarily used for the dehydration of crude oil in oil fields, and only in some cases is it employed for oil desalination in refineries. In this method, the demulsifier is added to the crude oil while mixing, and the mixture is heated to around 60°C in order to reduce the viscosity of the crude oil, increase the density difference between oil and water, and weaken the effect of the emulsifying agents in the emulsified water, thereby achieving oil-water separation. Among these, the addition of demulsifiers is a very important measure, as raising the temperature alone cannot completely break down the interfacial film that prevents water droplets from colliding and coalescing in most crude oils. After adding the demulsifier, the emulsified substances adsorbed on the phase interface, dispersed and dissolved on the surface of the water droplets have their activity (HLB value) altered. As a result, under the combined effect of temperature and the demulsifier, the emulsified crude oil causes the small water droplets to coalesce into larger ones, which then separate rapidly from the crude oil due to gravity. (3) Demulsification by electrodialysis: A high-voltage electric field is used to break down W/O emulsions; this method is widely applied in the desalination processes of electrodialysis units in oil refineries, as well as in the acid-base refining (electrorefining) of oils. Although both scenarios make use of high-intensity electric fields, their applications in electrodialysis and electrorefining differ slightly. Crude oil electrodialysis units generally use a power-frequency AC electric field, whereas electrorefining uses a DC electric field. The effect of an alternating electric field on an emulsion is that, under the influence of the electric field, the polarized water droplets attract each other and combine to form larger droplets, which then settle rapidly due to gravity. The effect of the direct current electric field is that the charged water droplets, under the influence of the non-uniform electric field generated by vertical cylindrical or plate-shaped electrodes, move along the lines of force; this causes the droplets to move toward the electrodes, where they accumulate on their surfaces, and then flow downward under the action of gravity. This method is typically used for emulsions with low water content, where the water droplets are far apart from each other, and the mutual attraction between them plays only a minor role. (4) Demulsification of O/W emulsions: Compared with W/O emulsions, single O/W emulsions possess completely different properties. Generally, the emulsifiers in W/O type emulsions are hydrophobic substances such as asphalt and resins ； O/W emulsions generally consist of hydrophilic substances such as soaps and water-soluble surfactants. Therefore, the methods used to break down W/O emulsions are not applicable to breaking down O/W emulsions; the demulsifiers for W/O emulsions are, in most cases, the emulsifiers for O/W emulsions. In refineries, O/W emulsions are primarily formed during oil refining, alkaline washing, and overhead water removal. O/W emulsions can be mixed with water in any proportion, contaminating refinery wastewater.

For crude oils with a relatively high density, the temperature can be controlled at around 40 degrees; our factory can control it up to 55 degrees at most. 20 degrees for light crude oil is sufficient. If the moisture content is not very high, leaving it to sit for a few days will suffice

The key factor in low-temperature dehydration of crude oil is demulsifiers!

For most crude oils at the combined stations of oil production facilities, the required dehydration level is less than 0.3%, achieved through a combination of sedimentation dehydration and electrical dehydration methods. Generally, if the crude oil dehydration index exceeds the specified upper limit, it can cause serious incidents such as flooding in the crude oil stabilization units downstream, especially in the crude oil stabilization towers of positive-pressure types. I work in the primary processing of oil and gas, so I am quite sensitive to this issue. Our positive-pressure crude oil stabilization units often suffer from the problem of high water content in the crude oil coming from the oil fields. Currently, online moisture analyzers are used for real-time monitoring, but they can only enable timely adjustments to the feed rate as a temporary solution, without addressing the root cause.

What is emerging now is ultrasonic demulsification, which is simple, convenient, and helps save energy and reduce consumption; it has been used in the refineries of Qilu Petrochemical for a long time already.

The key to crude oil dehydration is the selection of demulsifier type and the settling time.

Ultrasonic waves are a scam. I went to Qilu earlier this year to learn from their methods; I checked their metrics and they were even lower than ours, so the results weren’t good. They’re now using foreign demulsifiers for demulsification. It seems to be a project created to show off achievements.

Could someone provide the method for calculating settlement time?

I work at the Daqing Oilfield, where the main processes used are sedimentation dehydration and electrical dehydration.

Finally found some good material, thanks

What was said on the 5th floor is very good; I agree. The quality of dehydration has a significant impact on the design of the distillation apparatus, so it must be given great attention.

A combination of sedimentation dehydration and electrical dehydration yields good results! !

An electrodehydration device used primarily for dehydration is called an “electrodehydration unit”. . . An electrodesalination device used primarily for desalination is called an “electrodesalination unit”. . . The raw materials processed in the two methods may differ; electro-dehydration is used for crude oils with a high water content of around 10% or even over 30%. This includes oil from individual oil wells in oil fields, oil that has been collected through pipelines and requires pre-treatment, as well as heavy crude oils with high density and viscosity such as Oli emulsified oil – which is produced by adding water to crude oil abroad. These oils are sourced either from unexpected supplies from oil fields with high water content purchased directly by refineries, or from pilot production operations. . . Electrodesalination units are generally used in oil field stabilization systems to maintain stable quality parameters regarding salt and water content in crude oil during its transportation ； Or it is installed before the atmospheric and vacuum distillation or catalytic processing steps in refineries, to prevent or suppress salt corrosion and avoid catalyst salt poisoning. Generally, desalination can achieve dehydration at the same time. . . Generally, dehydration can achieve desalination simultaneously. . . :lol Last edited by wangsc on 2009-3-3 14:48 ]