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1. Measurement of crude oil (1) Liquid level measurement of glass tube A glass tube liquid level meter having a length of about 80 and constituting a communication tube with a separator was installed on an oil separator. Some important oil in the separator presses water into the glass tube, and the weight of the oil in the separator is obtained based on the relationship between the height of water rise in the glass tube and the amount of oil in the separator, and the time required for the rise of the liquid level in the glass tube is measured. , can be converted to the production of oil wells.
Glass pipe oil is a traditional method commonly used in domestic oil fields, accounting for more than 90% of the total number of oil wells. This method is simple to equip and has low investment. However, due to the intermittent oil consumption method, the system error is 10% to 20%. In addition, in the high water cut period, especially in the extremely high water cut period, it is very difficult to measure the liquid after the low gas-liquid ratio well and the metering operation causes great inconvenience.
(2) The telegram volume is based on the glass tube level metering oil. An electrode is installed above and below the specified dipstick height H. When the water rises to the lower electrode, the chronograph meter is turned on and the water rises. When the electrode is on the upper electrode, the meter cuts off and stops, and the time t for recording the rise in H of the water is recorded. The output of the well can be calculated according to the method of measuring the oil level on the glass tube.
(3) Dumping volume The oil diverting device is mainly composed of an oil diverter, a counter and the like. When one bucket is full, it is turned to drain and the other bucket is filled with oil. This cycle repeats the accumulation of oil. The oil measuring device has a simple structure and a certain measuring accuracy.
2. Measurement of natural gas (1) Orifice plate Measurement of gas is a traditional method of gas measurement. Measurements are made with orifice plates and bellows differential pressure gauges, depending on the differential pressure before and after the gas flows through the orifice plate. To calculate the gas flow. The metering device has a simple structure and convenient installation, but the measuring range is small, only 1:3, and the metering accuracy is influenced by the precision of the processing and installation of the orifice plate.
(2) Separator Discharge Gas Measurement After the oil and gas separator used for metering is completed, the natural gas outlet valve of the separator is closed, and the output of natural gas is calculated according to the time of liquid discharge. This method does not require a special measuring device, the principle is simple, but the operation workload is large and the precision is not high.
(3) gas flow meter gas measurement With the development of technology, gas flow meter in the natural gas measurement more and more applications, commonly used gas turbine flow meter, precession vortex flowmeter, vortex flowmeter, gas Roots Flowmeters and so on.
Gas turbine flowmeters, precessional vortex flowmeters, and vortex flowmeters are speed-type flowmeters. The gas turbine flowmeter is mainly composed of a turbine, a diversion gas, a magnetoelectric converter, etc., and has the advantages of high accuracy, good repeatability, rapid response, and wide measurement range. The disadvantage is that it has moving parts and is easy to wear, which affects the accuracy of measurement. .
Vortex flowmeter is based on the "Carmen" vortex principle developed a flowmeter. A vortex generator is inserted into the pipeline. When fluid flows in the pipeline, vortices are alternately generated on both sides of the vortex generator. The vortex columns alternately arranged downstream are called “vortex streets†and pass through a certain point in time. The number of vortex streets is proportional to the flow velocity of the fluid. The vortex street is detected by a pressure sensor. The weak electrical signal detected is processed and converted into flow for display or remote transmission.
Precession vortex flowmeter working principle; the flow of fluid into the flowmeter through the vortex generator to generate vortex flow, vortex flow precession in the venturi tube, to reach the shortening of sudden throttling to accelerate the vortex flow. When the vortex flow enters the diffusion section, it is forced into the precession-type secondary rotation due to the effect of the return flow. The frequency of the vortex flow is proportional to the medium velocity and is a linear relationship. It is detected by the pressure sensor. The detected weak electrical signal is processed and can be converted into a flow signal.
Precession vortex flowmeters and vortex flowmeters all have the advantages of simple structure, high accuracy, large measuring range, no mechanical moving parts, easy installation and use, and no influence of density, viscosity, etc. of the medium.
Gas Roots Flowmeter is a volumetric flowmeter with high measurement accuracy and is suitable for precise volume measurement. It is widely used in trade and precision storage and transportation metering management. However, the natural gas separated in the oil well metering contains more droplets, which will affect the lubrication of the rotating mechanism of the flow meter, and it is prone to card and plugging accidents. Therefore, it is generally not appropriate to use such a flow meter.
3. Measurement of Moisture Content (1) Manual Sampling The operator takes a certain amount of oil sample, and uses the distillation method, electric dehydration method, etc. to determine the moisture content of the oil sample, thereby obtaining the water content parameter of the oil well. This is the main detection method used in China's oil fields. It is not easy to manually take the oil sample. The lack of representativeness increases the error of the crude oil moisture content.
(2) On-line metering The on-line meter is installed on the crude oil pipeline and the moisture content of the liquid is measured on-line using instruments such as density meters, capacitors, and microwaves.
1 The density meter measures the moisture content. The density of the oil-water mixture was measured using a liquid density meter in the form of a vibrating tube or the like, and the water content was calculated from the density.
2 The capacitance method measures the moisture content. The measurement of water content of low-water-bearing crude oil mostly uses a coaxial barrel-type capacitive sensor, which uses the principle of the relationship between the dielectric constant of the crude oil emulsion and the water content to realize the measurement of the moisture content of the crude oil.
3 microwave method. The moisture content of the oil-water mixture is detected based on the degree of absorption of microwaves by crude oil and water.
4 gamma ray and x-ray absorption method. When gamma rays and x-rays pass through a substance, the intensity of the radiation decays. Because the absorption coefficient of crude oil and water to the radiation is different, the moisture content of the oil-water mixture can be calculated by measuring the intensity of the radiation.
4. New technology for measuring oil well production With the development of technology and the need for oil field management, reducing the labor intensity of workers, and increasing production efficiency, many metering devices that can comprehensively measure oil, gas, and water production have emerged.
(1) Three-phase separation metering Three-phase separation metering measures the separation of oil, gas and water separately. After separation, the crude oil contains relatively low water content (generally below 30%), crude oil measurement error is reduced, and it is not influenced by the oil well moisture content. However, in order to separate extra-high water-containing crude oil into low-water-bearing crude oil for measurement, the process technology is very complicated, and a large amount of free water often carries a part of crude oil, causing great errors, and requires a large number of instrumentation and investment. , management operations are difficult and maintenance costs are high.
(2) Two-phase separation measurement Two-phase separation measurement is to separate oil well production fluid into liquid and gas, and then measure it separately. The two-phase separation metering device is mainly composed of a two-phase separator, a gas flow meter, a liquid flow meter, an aqueous analyzer, etc. The gas flow meter and the liquid flow meter measure the gas production amount and the liquid production amount of the oil well, and the water analyzer measures the separated liquid. The moisture content of the oil well is calculated from the oil, gas, and water production of the well.
Another form of metering device consists of a two-phase separator, a mass flow meter, and a gas flow meter. The mass flow meter measures the amount of liquid that is separated and calculates the moisture content therein, thereby measuring the oil, gas, and water production of the well. This kind of computing device has less investment and is easy to operate. It has gained more applications in China's oil fields.
(3) Non-separate metering Non-separate metering does not separate well production fluids. Venturi tubes, densitometers, or different flow sensors are combined to measure the flow of gases and liquids. Double gamma ray densitometers, capacitors, and microwaves are used for liquids. The water content monitor is used to determine the oil and water content to calculate the respective production of oil, gas and water.
Oil and gas water non-separation metrology technology has great advantages in terms of land area and so on. However, oil, gas, water and other components in oil well production fluids are generally not uniformly mixed. They flow at different speeds and may also interact to form waxes and hydroxides, and cause unpredictable and complicated flow regimes. Therefore, it is very difficult to develop a flowmeter with a wide range of application. Although there are various schemes for achieving the separation measurement of oil and gas water at home and abroad, there are few successful applications.
5. Development Trends (1) Development towards instrumentation. With the advancement of technology and the wide application of various gas and liquid flowmeters, flowmeters with simple operation and easy reading are inevitably used in the production measurement of oil wells. Such as for natural gas metering swirl vortex flowmeter, vortex flowmeter.
(2) Develop in the direction of high precision. In the late stage of development of China's oil fields, it is necessary to accurately and timely understand the production status of oil wells and provide real and credible data for production management. As a result, the accuracy of oil well measurement will inevitably increase.
(3) Towards rapid development. In order to grasp the production status of oil wells in a timely manner, it is necessary to shorten the oil well metering cycle and perform more frequent and timely measurements on the oil wells, so the metering speed must be increased.
(4) Towards automation. The development of automation technology provides a reliable guarantee for reducing labor intensity and increasing labor productivity. At the same time, in order to achieve accurate and rapid measurement of oil wells, automated measurement methods must also be used. The research and application of three-phase separation and measurement, two-phase separation measurement and non-separation measurement will receive more and more attention. (
The measurement of oil well production is an important task in oilfield production management. Accurate and timely measurement of oil well production has important guiding significance for understanding the status of reservoirs and formulating production plans. At present, the oil well production measurement methods adopted by various oil fields in China include gas measurement with glass tube oil well plate, gas measurement with oil hopper plate, two-phase separation density method and three-phase separation measurement method. With the advancement of technology, oilfields increasingly need well-functioning, highly automated well metering equipment to increase labor productivity and oil field management.