Gu Ke Jiang REN Fu-Mei
Jiangsu Oil Exploration Bureau
Yang Zhou 225009

Abstract Technical studies on the measurement of stripper wells have been made for many years, but the problems have not been solved completely. This study is aimed at transforming the structure of the separator to further improve technological process and increase accuracy of measurement. Traditional process of measurement should also be innovated by applying advanced techniques of measurement abroad.
Subject Headings Well measurement, Separator, Measurement process, Measurement mechanism

As the old oilfields of the high moisture content, the difficulty of measuring oil is increasing. Coupled with the development and production management needs of the oil field measurement technology requirements also increase. Therefore, oil field wellhead serious measures to solve problems, improve the current wellhead measurement accuracy and management level, oil production has become an urgent need to resolve important issues.

Well Status and measurement problems

At present, oil wells are basically using a measuring vertical separation for a two-phase gas-liquid separation, with glass tube of oil, moisture content of sampling tests, double bellows differential pressure measurement gas, such measurement methods in high-moisture content of the main Existence of the following questions.

A two-phase separator glass tube of oil, measuring time is short, big error

Glass tube of oil has the advantage of simple, easy maintenance, durable and low moisture content in the period was able to meet production requirements, the high moisture content period, the amount of the increase in oil time only 1 ~ 2 min, or less . In such a short period of time measuring the output of 24 h, the error on the larger relative error is greater than about 10%.

2 artificial moisture content of crude oil, big error

To accurately measure the production wells, it is necessary to accurately measure the average moisture content of crude oil. Because of the current representative sampling of specific operations and the factors have great skills, several times the average margin as high as 20% to 30%, which amount to a single well-production and production water.

3 gas output measures are not running

Well tone of the measurement of output, although the configuration of the orifice flowmeter, but the scene investigation shows that the use of a not ideal, most instruments can not put normal operation, many metering station also has never used, plus the years of not Orifice Test, even in hard to say-also used its measurement accuracy.

High moisture content of the oil well measuring the characteristics of

A high moisture content of wells, and volatile

The use of two-phase measures separator measurement of high moisture content of crude oil, although flowmeter and online aquifer analyzer can be measured in the normal range, but measured by the net oil production wells are still greater error, do not meet standards. Assumptions measurement of the total amount of work that did not flow meter error, only 2.0 accuracy of high water cut-line analysis (generally high moisture content of the instrument are not reliable accuracy higher than 2.0) or testing of the oil-for measurement error on the 2.2% to 100%, see Table 1.

Table 1 moisture content and accuracy of net oil error tables

This is the moisture content of measurement error is 2% of net oil at the accuracy of measurement.

2 oil, gas and water separator three-phase measures

From Table 1 indicates that the high moisture content of the oil wells to the net oil measurement accuracy, it is essential to the mixture of free water separated, made into instruments of crude oil in water content dropped to a certain extent (for example, 30 per cent), The measurement accuracy can be guaranteed. The use of three-phase separator, the oil, gas and water by separating certain requirements in order to more accurately measure the oil wells, gas, water production, DN600 bubble of crude oil metered into the separator, a waist measurement of volume round Flowmeter , The measured value to High 4.5% (compared with the quality of law). Practice has proved that only Fen Deqing, in the order of the prospective. Therefore, a three-phase separator high moisture content of the oil well measuring the key technology.

Foreign oil metering situation

Well measurement main features in the following areas:
(1) the United States in the oil field wellhead measurement, the low moisture content of a two-phase separation, the high moisture content in a period of three-phase separation, the timing for measurement. In the oilfield construction design, the three-phase separators are designed, in the period of low moisture content, three-phase separator when the use of two-phase, high moisture content in the period to start using three-phase separation functions. U.S. oil metering station is characterized by the process. Metering station set up isolation measures and production separator two sets of devices, production separator used to measure the metering station at the oil, gas and water output, measured in oil wells more than the election of a multi-valve.
2A three-phase separator measurement instruments and supporting the use of most, if equipped with on-line flowmeter and moisture content analysis instrument can achieve continuous measurement.
3Metering station at the second table basic intelligence, digital, flow, moisture content, such as data collection, processing, computing, computer output are used, may at any time, regular print, Absolute Oil output, clean water, gas, water content and other data.
4) Measurement system, every oil wells in the general measurement 8 h or 24 h, measurement cycle for 7 d, 12d, 30d range.

New oil wells measurement devices Development and Test

Years of study in the three-phase separator on the basis of measurement technology, and drawing from a foreign country, the measurement technology, we developed a three-phase measures separator at the scene and conducted a test, test results show that the separation is in the process of design Some breakthroughs, made good use of effects.

1 separator design of the formation

In the early 1970s, it was the French have automatic three-phase measures of horizontal separation for a large number of field trials. In its application conditions and the actual situation of China's oil fields under the premise of inadequate understanding of, their mechanical imitation, such as oil-water interface control float, finally failed. The main reason is the failure SEPARATOR, poor control of oil-water interface, frequent water run oil or oil in the water is running. Poor control of oil-water contact in other crude oil gathering and transportation equipment such as vertical or horizontal settlement dehydration cans, electrical equipment, such as dehydration is widespread in this issue in the future, have been trapped for more than 10 years Longzhe oil and gas gathering and transportation workers, people in Set on the location of the oil-water interface installed a wide range of instruments, results are not satisfactory. Although the three-phase separation imitation of France's test failure, but we recognize that, in order to obtain the three-phase separator successful, we must overcome the control of the interface difficulties. In order to clarify three-phase oil-water separator interface in the working conditions of the actual situation, we conducted the following test: the design of a three-phase 1000 the horizontal separation, as shown in Figure 1. Liquid separator in the side of the equidistance top-down design a sampling of the valve. In the run-time through a large number of samples that separator in the operation of the liquid state is not always there is a top oil, the clear water below the oil-water interface, and is often part of the liquid at the top of the water content is Low net reservoir, the water separator at the bottom of the layer, the moisture content of which is a gradual transition layer. The large number of field experiments for many years so that we get the following valuable experience: interface control is the key to success for separation technology; previously used a variety of instruments to direct attempts to control oil-water interface is undesirable, while enhancing the instrument control Accuracy is work hard directional errors. Process conditions on the instruments play a decisive role in the success or failure.
In light of the above understanding, we see some of the information in a foreign country, after the Enlightenment has been drawn up following a three-phase separator design (see Figure 2)
Oil wells considered in the measurement of impurities, and wells with high gas content is not high, so choose vertical structure. Set separator, with oil drums and set buckets, barrels from top to bottom at both ends of a level controller, for the separation of the oil-water interface is usually the direct control of a water diversion weir by the regulation can export high water , And fixed the corresponding high oil exports, thus indirectly control the oil-water interface height, making isolated from the oil and water into oil drums and buckets, respectively, if the discharge of oil or water targets are not met, as long as the adjustment of export high water Can easily meet the requirement. Oil drums and buckets of liquid level control is very easy to achieve a mature technology that can reliably run.

2 wells measuring device measures the composition and theory

Well oil to the three-phase separation, the crude oil into oil drums, when reached on the float at the surface, float a signal to pneumatic valve film full Pai oil, crude oil through online moisture content analyzers, flowmeters scraper, the film valve And so on from the separation of water after the water overflow weir of the mouth, into the collection buckets. Similarly, when the water level rose on the float, the film valve open drainage, the water flow meters, valves from the film, when oil or water level dropped to the float position, film valve closed, the next bucket of oil or the accumulation of water . In separator at the top of the gas exports, with the temperature, pressure transmitter, filters, gas Roots flowmeter, auto-Diao Yafa, single-flow valve, and so on. The three-phase separation into the tubing and attach a drug device can be controlled in a row to increase to oil demulsifier.

3 three-phase separation with the main technical indicators

Dimensions: 16004300
Work pressure: 0.6MPa
Operating temperature: 40桫47
Liquid handling capacity: 200m 3 /d
Liquid Time 30min
After the separation indicators кˮ30%
Sewage oil 0.4%

4 separator in the measurement of the benefits

(1) the vertical separation, allowing water contact in the larger context of fluctuations, to separate the effect of control.
2 sets used oil drums, set buckets, water diversion weir structure, the difficulty of direct control over the oil-water interface control methods become easy to implement and control the liquid level switch control.
3intermittent row makes a way of measuring instruments range can adapt to the difference between the yield of oil wells, that is, in the capacity of the separator, no matter what the output of oil wells in the number, as long as good control before and after the pressure flowmeter , In the measurement when the flow meter will not be super-range. So in the measurement stations do not have to use different range of more than flowmeter to adapt to the uneven production of the wells in the measurement.
4internal separation from the settlement process from discharges of liquid flow when the disturbance, the separation will not be affected.

5 and three-phase separator supporting the main instrument

Flowmeter flexible scraper for oil volume, volume of water accuracy1.0%
Online moisture content analysis0%100% accuracy:2.0%
Roots gas flow meter accuracy:1.0%
SCM and print output devices

6 trial

three-phase separation measures to meet requirements. Oil moisture <30 percent of the water oil <0.4%; used to transfer control of the oil-water interface weir active, flexible and very effective, so that eventually separated from the water content in the oil and oily water to control the rate, which is technology On a breakthrough; SCM measures for the oil wells in the oil, water level control, automatic acquisition of oil, gas and water traffic signals and temperature, pressure and to signal processing, calculation, may at any time or regular print results .

7 error analysis

As instruments of direct measurements of x and y indirect measurement exists between the function y = f (x), from Differential know, direct measurements of measurement errors caused by indirect measurements of error of the function of the incremental, The incremental function of the differential can be used to express. Similarly, n direct measurements xi (i = 1,2, n) and indirect measurements of the relationship as a function
y=f(x 1 ,x 2 x n )
The measurement of the total function of the error can be said for the entire differential

On the function of the general formula for calculating error. For our study by the measurement device of its instrument of error for the random nature of error. Its is calculated as follows:

In the R-related items also called for covariance. In actual measurement, between the various direct measurements are independent, that is, the R zero.
Isolation measures on a single instrument of measurement error xi a random error, and mutually independent. According to independent variables error superposition principle, the measurement device error may be under-calculated:

The measurement is a complete separation of the measurement system, measuring the total error from four areas: water content analysis of the accuracy of the instrument, flexible scraper flowmeter accuracy of the measurement error of oily water and do not take into account additional factors of error.
Moisture content analysis instrument for the accuracy of2.0%
Flowmeter flexible scraper for the accuracy of 1.0%
Oily water for the measurement error 0.2%
Did not consider the additional factor of error 0.1%

Through the above calculation of measurement devices can be drawn from the uncertainty of 2.5%
This package has placed in recent years in Daqing, Jiangsu Oilfield, such as probation, effective and basically solved the high water cut wells measurement issues, the promotion of good value.

8 needs to be improved in the

separator size too small block of low-yielding wells, the need to design small, lightweight, prizing the load; the lower than the gas-liquid wells, although with less angry, but in the three-phase separators, gas The proportion of space to the right, gas space on the effects of separation can not be ignored.

Small block of low-yield oil wells measurement of low-vision

Small block of low-yield wells measurement issues, has long been unable to solve very good. We imagine, in the gas separation after two-phase measures, according to two separate dissolution of the liquid mixture equivalent to the total volume of the two liquids and size of the principle, and the mixture by measuring the total volume and quality of the two physical , The relevant equations for the two liquids are the respective volume (mass).
Another method is the use of metering station activities, the effect may be better. With small three-phase separator with oil, gas and water meters and metering pumps, water pumps for metering and measuring enter into the pipe network to filling stations. The measurement at a reasonable measurement cycle tour. This measurement methods have the following characteristics:
(1) the traditional "m" shaped cluster fixed metering station at gathering process to series gathering process, greatly reducing the pipeline investment, while reducing the management difficulties.
(2) to achieve a single well oil, gas and water three-phase separation, continuous automatic measuring instrument to ensure measurement accuracy. Oil and water 5%, gas 10%.
(3) the measures to achieve professional management, computer automatic data acquisition and processing, printing oil, gas and water production. Eliminate the human factor, to create the conditions unattended.
(4) a trailer carrying, all-weather measures to replace the current fixed metering station. Its effect significantly.

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