Compared with the traditional separation and pressurization scheme, vacuum system on offshore platform has economic advantages, which is of great significance to the development of offshore marginal oil and gas fields. This paper analyzes and discusses the application of vacuum system in offshore oil and gas fields. Why can it be applied in offshore oil and gas fields?
Offshore production facilities refer to the buildings built on the sea. Due to the fact that offshore facilities are used for subsea oil development and production, and the differences in water depth and sea conditions, reservoir area and production life, there are many types of offshore production facilities. Basically, it can be divided into three categories: offshore fixed production facilities, floating production facilities and underwater production systems.
The development of offshore oil and gas fields is a complex system engineering, and the production of oil and gas often depends on the export pressurization equipment. The vacuum system is a kind of equipment that can directly pressurize and transport the wellhead logistics. It does not need to separate the gas-liquid two-phase fluid, and the pressurized multi-phase fluid can be directly transported by an offshore pipeline. Compared with the traditional separation pressurization scheme, the vacuum system scheme can reduce the wellhead back pressure, improve the oil and gas production, reduce the number of equipment on the platform, occupied area and platform weight, and save 30% ~ 40% of the initial investment. With the contradiction between oil and gas field development cost and economic benefits becoming increasingly prominent, multiphase transportation technology has been paid more and more attention.
Vacuum system is composed of two-stage bracket type: it is composed of oil rotary vane vacuum pump, roots vacuum pump, mounting bracket, connecting pipe, control box, oil mist filter, etc., which is used for vacuum exhaust of production and research equipment.
In roots water ring vacuum system, it is more advantageous to select water ring vacuum pump as the front stage pump than other vacuum pumps. It overcomes the shortcomings of the limit pressure difference (the limit pressure of the unit is much higher than that of the water ring vacuum pump) when a single water ring vacuum pump is used and the pumping rate is low under a certain pressure. At the same time, it retains the advantages of Roots vacuum pump that can work rapidly and has a larger pumping rate. It is especially suitable for pumping out a large amount of condensable steam, especially when the gas ballasted oil seal mechanical vacuum pump has insufficient ability to remove condensable steam, or the solvent used can deteriorate the pump oil and affect the performance, or the vacuum system does not allow oil pollution. When equipped with explosion-proof motor and electrical appliances, and comply with the corresponding safety rules, it can also extract flammable and explosive gases.
Vacuum system in offshore oil and gas fields application advantages:
The wellhead fluid of offshore oilfield is usually a mixture of oil, gas and water, and the material flow of each dispersed wellhead platform usually needs to be exported to the central platform for oil, gas and water treatment. Based on the traditional pressurization scheme, the gas-liquid separation of multiphase fluid is carried out in the separator first, the separated associated gas is pressurized and exported through the natural gas washing tank and compressor system, and the separated liquid is pressurized and exported through the crude oil export pump.
Now, the vacuum system does not need to separate the wellhead material flow, and can directly pressurize the wellhead multiphase fluid for export. Compared with the traditional production system, the mixed transportation system simplifies the platform process and reduces the number, area and weight of equipment on the platform. In addition, for the low pressure oil wells in the later stage of oilfield production, the mixed production system can be used to reduce the wellhead pressure and increase the oil and gas production, so as to effectively improve the economic benefits of oilfield development.