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Crude oil dewatering

All oil fields will be exploited with water ina certain period, especially for oil field with fast producing rate and withwater injection to strengthen the exploitation. The period of oil producing withoutwater is normally short. The water appears early and the moisture content incrude oil increases rapidly. The water is almost a “permanent partner” forcrude oil during the exploitation of oil field, especially at the middle andlater period of exploitation, there is no oil when there is no water. Therefore,dewatering of crude oil becomes an essential link for the development of oilfield attracting people’s attention.

Over years of repeated practices, thedewatering technologies of crude oil successfully developed are as follows:

Dewatering through settlement and separation:the separation of oil and water is achieved through passing through specialequipment, which takes advantage of the principle of light oil and heavy water.

Dewatering through chemical demulsification:the oil and water in emulsified state are separated by adoption of chemicalagent. The chemical demulsification is the most widely adopted one during thedewatering of crude oil.

Dewatering through electric demulsification: itis used for high intensity electric field of electric demulsification with AC,DC, AC-DC and impulse power supply. The basic principle is to separate oil andwater ion through the function of electric ion.

Wetting coalescence demulsification: itfacilitates the reduction of viscosity of crude oil and increase ofvolatilization degree of light components during the dewatering andstabilization of crude oil, which promotes the separation oil and water.

A large amount of energy is required fordewatering of crude oil. The dewatering and stabilizing equipment of crude oilare established together for the purpose to take full advantage of the energy. Tosave energy and reduce volatilization loss of oil and gas, the light hydrocarbonshall be recovered through crude oil stabilization. The dewatering process ofcrude oil becomes “tank-free and enclosing”. The process without tank isfeature with high enclosing degree. There is not any volatilization loss duringthe process. During the enclosing process, the enclosing of crude oildewatering process is vital important due to its high operating temperature,long suspension time and liable volatilization loss of oil and gas. Accordingto inspection, the oil and gas loss accounts for 50% of the total loss duringthe dewatering link if no enclosing process is adopted.

The dewatering equipment of crude oil is thereflection of dewatering technology, which is important during the dewateringprocess of crude oil. The rationality of structure for dewatering equipmentinfluences directly the effect and efficiency of dewatering and quality ofcrude oil, as well as the production and operating cost, and therefore impacts thetotal economic benefit of crude oil dewatering production. For this reason, theoil-gas gathering and treatment process become “tank-free”, that is to say, thesettlement separator of storing tank type is not used any more, which isreplaced by pressure-resisting settlement separator with development ofadvanced large-scale dewatering and pressure-resisting vessel.

The electric dehydrator has the highest efficiencywith the best treatment ability relaying on the function of electric field fordewatering. There are many types for electric dehydrator, such as pipe type,storing tank type, vertical cylindrical type and spherical type. With thedevelopment of petroleum industry, the electric dehydrator of horizontalcylindrical type is widely adopted after continuous practice and conclusion. Thetreatment scale and production quality reach higher level with treatmentability for each device per hour of several times of its capacity. The moisturecontent of purified oil can be reduced below 0.03%.

The effective combination of horizontalelectric dehydrator, oil-gas separator, firebox heater and settlementdehydrator is to speed up the oil field construction and improve theconstruction prefabrication degree of dewatering device. The combination ofdevices with compact structure saves pipelines, valves, power equipments in alarge degree. This combined device can increase or reduce the quantity ofequipments according to the production scale with big flexibility, especiallywhen the oil field scale changes frequently.