What is Pumping Oil Extraction Method? A kind of artificial lift oil extraction method (refer to artificial lift oil extraction method). The method of running a pump in the oil well and pumping the liquid produced in the oil reservoir to the surface is called the oil pumping method. The oil well pump used in this method is divided into two types: rod and rodless according to the power transmission mode.
??The rod pump?is the most commonly used single-cylinder single-acting oil pump (Figure 1), and its oil displacement depends on the diameter and stroke of the pump and the number of strokes. There are two types of rod pumps, rod pumps and tube pumps. A complete sucker rod pump unit includes a sucker unit, a sucker rod string, and a sucker pump (Figure 2).
??The pumping unit mainly converts the circular motion of the driving machine (usually an electric motor) into reciprocating linear motion to drive the sucker rod and the pump. The pumping unit has two types: beam type and seamless type. The former is the most widely used and the chain pumping unit used in some mines in China belongs to the latter (see color image). The sucker rod string is a long rod string that connects the pumping unit and the sucker pump. It is more than a kilometer long.
The vibration and elastic deformation caused by the alternating load make the stroke of the suspension point of the sucker rod and the stroke of the pump plunger different. Big difference. Oil well diameter, run, and number of runs must be optimized by design calculations based on the production characteristics of each oil well. Install a gas separation device? ? gas anchor at the pump inlet, or increase the depth of the pump to reduce the influence of the gas content in the fluid on the fullness of the pump (ie volumetric efficiency).
The vertical chain pumping unit developed in China is suitable for large-load and long-stroke operations.
??A rod pump is a self-weight system. As the cross section of the sucker rod increases, so does its load. There is a limit to the penetration depth of sucker rods made of various materials. To increase the penetration depth of the pump, the material, heat treatment process, and sucker rod grade must be changed. Depending on the elasticity of the sucker rod and the characteristics of the formation fluid, a favorable combination of stroke and number of strokes should be selected when choosing a work system.
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The working depth of the rod pump has exceeded 3,000m outside, and the load of the pumping unit has exceeded 25t. The displacement of the pump is related to the depth of the well. The daily displacement of some shallow wells can reach 400 m 3 , and the average depth well can reach 200 m 3 , but the pumping The production of oil wells is mainly based on the production capacity of the oil layer .
The main advantages of the rod pumping unit are simple structure and convenient maintenance and operation. Pump efficiency in medium and deep wells is about 50%, which is suitable for medium and low production wells. Currently, more than 85% of the oil wells in the world are produced by mechanical extraction of oil and most of them use rod pumps.
The rodless pump is suitable for medium depth wells or deep wells and inclined wells with large production. Industrial applications are electric submersible pumps, hydraulic piston pumps and hydraulic jet pumps.
??Electric submersible pump?is a set of multi-stage centrifugal pumps and electric motors connected directly to the pump set. The power cable sends electricity to the downhole motor to drive the centrifugal pump and pump fluid from the well to the surface.
Since the mechanical pump unit is used in the casing, the diameter of the mechanical pump is limited, so a form is needed (Figure 3). To prevent downhole fluid (especially water) from entering the armature and causing motor failure, a special sealing device is required and a protector is installed at the connection part of the pump and motor.
The displacement of the pump is limited by the size of the well and the head is determined by the number of stages of the pump, which depend on the power of the motor. Electric submersible pumps are suitable for oil wells with medium and high liquid production, fine oil or watery crude oil with less gas and sand. Generally, when the daily displacement is 100-1000m 3 and the head is within 2000m, the efficiency is higher and it can be used in inclined wells.
The well construction is relatively simple, the management is convenient, the maintenance-free period is longer, and the pump efficiency is about 60%; but it is not suitable for wells with high gas content and wells with corrosive fluids. The displacement of the pump cannot be adjusted after lowering, and the mechanical pump constitutes the cost. Higher, raising and lowering operations and maintenance are more complicated.
??Hydraulic piston pump?uses ground pump to inject liquid to drive downhole hydraulic motor to drive downhole pump to pump downhole liquid out of the surface. The principle of operation of a hydraulic piston pump is similar to that of a rod pump, except that the reciprocating movement is carried out by a hydraulic motor and a reversing valve (Figure 4). There are two types of hydraulic piston pumps downhole pumps, single acting and double acting, and high pressure plunger pumps are used for surface pumps.
There are two types of processes: ? Open process. The single-tube structure uses low-viscosity crude oil as the power fluid, which not only reduces the frictional resistance of the pipeline, but also reduces the viscosity of the extracted oil and mixes with the produced liquid to be produced. on the floor. . ?Closed process. Use light oil or water as power fluid, add lubricants and preservatives when using water, automatically circulate and do not mix with the produced fluid, only a small amount of replenishment is needed during the working process.
The hydraulic piston pump can be operated in a single well, or can be built for centralized management of a pump set. The displacement range is wide, from tens to thousands of cubic meters per day, and it is suitable for deep wells, high-elevation wells, heavy oil wells and inclined wells. The advantage is that the displacement can be adjusted arbitrarily, the oil pipe cannot be raised and lowered from the pump, and the operation and management are convenient.
The pump efficiency can reach more than 85%. The disadvantage is that a high-pressure pipe must be built in the ground and the energy fluid must be processed, which increases the costs of construction and management of the well.
Hydraulic jet pump oil pump with nozzle and diffuser (Figure 5). Hydraulic jet pump has no moving parts, simple structure, low cost, convenient operation, but low efficiency, not more than 30-35%, resulting in too small a production pressure difference, which is only suitable for high pressure and high performance. wells. Generally, it is only used in the initial stage of the hydraulic piston pump, that is, when the oil well pressure is high and the displacement is large; when the pressure decreases and the displacement decreases, the hydraulic piston pump is used.