Optimizing Energy Consumption of Electric Submersible Pump in Offshore Oilfield

Electric submersible pumps have always been highly praised for their large displacement and head for lifting oil production. In addition, the electric submersible pump production system has the advantages of simple ground equipment, convenient operation, small equipment occupation area and space, and long service life. It is especially suitable for Offshore oil fields where space is at a premium. At present, the electric submersible pump well lifting method has become one of the main lifting methods for offshore oilfield development. The electric submersible pump unit has high power and a large installed total capacity. It is one of the main energy-consuming equipment in the oilfield. Especially when the oilfield development has entered the stage of high water cut, the requirements for the oil recovery technology of the electric submersible pump are also increasing. Due to equipment selection and design Unreasonable and oil well formation parameters, changes in production capacity and other reasons lead to reduced working efficiency of electric submersible pumps, high energy loss, and increased oil recovery costs. In this paper, by studying the method of changing the working system of the oil well, the electric energy utilization rate of the electric submersible pump can be improved, the energy consumption of the electric submersible pump can be reduced, and the electric submersible pump can be operated in the best economic zone.

The composition of the electric submersible pump oil production system is mainly divided into two parts: the surface and the downhole. The downhole part of the electric submersible pump oil production system is mainly composed of sensors, protectors, check valves, submersible oil pumps, pressure relief valves, power cables and centralizers. The ground part is mainly composed of transformers, frequency converters, switchboards and control cabinets. The working principle of the electric submersible pump unit is to use electric energy as the power source. The grid voltage is first changed by the transformer and then input to the control cabinet. The electric energy is transmitted to the submersible motor through the cable. The submersible motor converts the electric energy into mechanical energy to drive the electric submersible pump at high speed Rotate to increase the pressure of the well fluid step by step, reaching the lifting head required by the electric submersible pump unit at the outlet of the electric submersible pump, the lifted well fluid is lifted to the ground through the oil pipe, and then transmitted to the surface gathering and transportation system through the surface pipeline .

The electric submersible pump transports the oil, gas and water in the formation to the ground, which itself is a process of energy conversion, and each node of energy conversion will have a certain loss rate. The total power lost in the oil production process of the electric submersible pump can generally be divided into three parts: downhole input power loss, intermediate cable power loss and ground equipment power loss. main power loss point. The main factors affecting the energy consumption of electric submersible pumps are as follows:

• Effective power loss. The effective power loss is related to the depth of the pump hanging, the lifting fluid volume, and the fluid density (oil density, water content, sand content). The deeper the pump hanging, the higher the energy consumption, and the larger the lifting fluid volume, the higher the energy consumption. The bigger the higher the energy consumption.
• Oil pipe friction loss. The friction loss of the oil pipe is affected by many factors, among which the flow rate, the size and length of the oil pipe, the smoothness of the inner wall of the oil pipe, the fouling of the oil pipe, and the wax deposition will all affect the friction loss. Secondly, the friction caused by the fluid viscosity is also the friction loss of the oil pipe. main source of .

(3) Power loss of submersible motor. The power loss of the submersible motor is related to the head of the electric submersible pump, the displacement of the electric submersible pump, the efficiency of the submersible motor, the formation pressure, and the physical properties of the fluid.

(4) Intermediate cable power loss. The larger the cross-sectional area of the cable, the smaller the resistance, and the smaller the power loss of the cable under the same voltage; the larger the cable voltage, the smaller the power loss of the cable under the same resistance. In addition, the material of the cable is different, the resistance is also different, and the power loss of the cable is also different.

(5) Power loss of ground equipment. The power loss of surface equipment is affected by factors such as wellhead back pressure, nozzle size, surface pipeline inner diameter, surface pipeline inner wall roughness, and valve pressure drop loss.

Solution:

(1) When the electric submersible pump produces oil in offshore oilfields, the design parameters of the electric submersible pump must match the actual production parameters. The use of small pumps and large displacement production will result in the loss of electrical energy converted into heat energy, and the production of large pumps with small displacement will result in waste of electrical energy converted into pressure energy.

(2) Reduce the back pressure of the surface process and reduce the pressure difference between the upstream and downstream of the oil well nozzle, which can reduce the amount of work done by converting the electrical energy of the electric submersible pump into fluid internal energy and reduce energy consumption.

(3) After the oil well enters a period of high water cut, when extracting liquid to increase production, the oil nozzle should be opened first, and then the frequency should be adjusted according to the wellhead pressure, so as to maximize the energy saving effect.

(4) Due to the limited space of the offshore platform, most of the reservoirs with high porosity and large fractures are exploited with edge and bottom water, and the formation energy is sufficient. After entering the high water cut period, the method of increasing liquid production is basically adopted to increase oil production Increasing production will also face the problem of a substantial increase in energy consumption. This method can maximize the utilization of electric energy of the electric submersible pump, make the electric submersible pump operate in the best economic zone, and achieve energy saving and carbon reduction. It is suitable for the promotion and implementation of offshore oil fields.