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A new study of low-yield wells metering device technology
Published on:2015-3-20 11:00:10 Hits:

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 oilfield in high water cut period, the oil well metering becomes more and more difficult.Coupled with the development of production and management needs, to oil metering technologyrequirements in raising. Therefore, earnestly solve oilfield wellhead metering problem, improve thecurrent wellhead metering accuracy and management level, has become an important issue to be solved in the oilfield production.

The present situation and existing problems of oil well metering

At present, the oil well metering basically is used in vertical two-phase separator for gas-liquid separation, tube oil using glass, artificial sampling water content, double corrugated pipe differential pressure measuring gas, this measurement mainly exists the following problems in high water cut period.

The 1 phase separator glass tube oil, the measurement time is short, big error

As the old oilfield in high water cut period, the oil well metering becomes more and more difficult. Coupled with the development of production and management needs, to oil metering technology requirements in raising. Therefore, earnestly solve oilfield wellhead metering problem, improve the current wellhead metering accuracy and management level, has become an important issue to be solved in the oilfield production.

The present situation and existing problems of oil well metering

At present, the oil well metering basically is used in vertical two-phase separator for gas-liquid separation, tube oil using glass, artificial sampling water content, double corrugated pipe differential pressure measuring gas, this measurement mainly exists the following problems in high water cut period.

The 1 phase separator glass tube oil, the measurement time is short, big error

Glass tube oil has the advantages of simple operation, convenient maintenance, durable, in low water period is able to meet the production requirement, in high water cut stage, liquid increased, the amount of the oil time is only 1 ~ 2min, or even less. In such a short time measurement of 24h production, the error caused by the larger, the relative error of about more than 10%.

2 artificial determination of water content in crude oil, big error

To accurately measure the oil production wells, we must accurately measure the average moisture content of crude oil. Because of the current representative and specific operators manual sampling skill factors have a great relationship, mean differences of several times of up to 20% ~ 30%, the quasi oil production of single well is difficult to quantity and water production.

3 gas output measurement are not running

Metering well yield configuration tone, although the orifice plate flowmeter, but from the field survey, using was not ideal, most instrument failed to put into normal operation, many metering station also never used, and the orifice plate for many years without verification, even in its measurement precision is also very difficult to explain.

The characteristics of oil well measurement in high water cut period

1 oil wells with high moisture content, and large fluctuation

The use of two-phase metering separator metering of crude oil with high water content, although the flowmeter and online moisture analyzer can work normally in the measuring range, but pure oil production wells measured still larger error, do not meet the standard requirements. Work flow meter measuring total fluid volume assumed when no error, only high water content online analyzer 2 level accuracy (reliable precision generally high water cut analyzer were less than 2 level) of pure oil measurement error or artificial laboratory caused is 2.2% ~ 100%, see table 1.

Table 1 moisture content control and pure oil accuracy error table


2 oil, gas, water three phase metering separator

From table 1 we can see, in high water cut stage to the pure oil well metering accuracy, must take the free water in the mixture liquid is separated, so that water cut crude oil into the oil quantity meter rate dropped to a certain extent (such as 30%), the total measurement accuracy can be guaranteed. The use of three-phase separator, the oil, gas, water separately according to certain requirements, oil, gas, water production can be more accurately metering of oil wells, the metering separator foam oil enters the DN600, using the waist wheel flowmeter fluid volume, the measured value is higher 4.5% (compared with weight method). Practice has proved, only tell, to measure the potential. Therefore, a three-phase separator into the key technology of oil well measurement in high water cut period.

Measurement of oil wells in foreign countries

The characteristics of oil well metering mainly has following several aspects:

(1) USA in Oilfield wellhead metering in low water cut stage, using two-phase separation, high water cut stage by adopting a three-phase separation, timing of continuous measurement. In the oil field construction and design, is the design of the three-phase separator, in low water period, three phase separator when using a two phase, in the high water cut stage, began to use three-phase separation function. The characteristics of America oil metering station process is. Set the metering separator and production separator two sets of device for metering station, production separator used to measure the metering station of oil, gas, water production, well and the oil well measurement adopts multi way valve.

(2) by using a measuring three-phase separator mostly with the instrument supporting the use of, such as equipped with flow meter and online moisture analyzer can realize continuous measurement.

(3) metering station two times table of basic intelligent, digital, flow, moisture content, data acquisition, processing, operation, output by computer, can display, print output timing, net oil, gas, water purification, water content and other data at any time.

(4) measurement system, general every oil well metering 8h or 24h, the measurement cycle for 7d, 12D, 30d range.

Development and test of new type oil well metering device

Based on years of study of three-phase separator metering technology, and from the separate measurement technology of foreign countries, we developed three phase metering separator and tested in the field, the experiment results prove that, the separator has the breakthrough in the design process of the structure, achieved good results.


The formation of the 1 separator design

At the beginning of twentieth Century 70 years, people have done a lot of field experiments on the French horizontal three-phase automatic metering separator. Learn enough premise in the actual situation of its application condition and oil field in China, by mechanical imitation of the oil-water interface, such as the control of the floating ball, finally failed. The main cause of failure is the separator oil-water interface control problems often occur in water, oil or oil to run run water phenomenon. The oil-water interface control problems in the other gathering equipment such as oil vertical or horizontal sedimentation tank, the electric dehydrator dehydration equipment exists generally, this problem in the future 10 years have been trapped on the oil and gas gathering and transportation workers, people have installed various instruments in the interface position of oil and water, the effect is not ideal. Although the test of imitation French three phase separator failed, but makes us realize that, in order to obtain the success of three-phase separator, must overcome the difficulties of interface control. In order to understand the actual situation of three-phase separator oil-water interface in working conditions, we carried out the following experiments: the design of the horizontal three-phase separator of a Phi 1000, as shown in figure 1. A list of sampling valve design in distance separator liquid part from top to bottom side. At run time by a large sample analysis, the separator liquid in the run down state section does not always exist a is oil above, below is the clear water of the oil-water interface, and often is the top part of the liquid is water with very low rate of pure oil, the bottom of the separator for water layer, in which a water content the gradient transition layer. A large number of field experiments for many years so we obtained the following valuable experience: interface control is the key technology of the success or failure of the separator; previous attempts to use a variety of instruments to directly control the oil-water interface is not desirable, in improving the accuracy of instrument control fluctuation kongfu is directional errors. The success or failure of technological conditions on the instrument plays a decisive role in.

In view of the above, we obtained the enlightenment in refer to some foreign material, worked out the following three phase separator design (see Figure 2).

Considering the multi impurity oil well metering in oil wells with high water, and gas content is not high, so the choice of vertical structure. A set of drums and separator in buckets, each bucket is arranged on the lower ends of the separator liquid level controller, the usually direct control of oil-water interface into adjustable weir pipe by adjusting water outlet height, and fixed oil outlet corresponding to height, thereby indirectly control the oil water interface height, makes the separated oil and water can respectively enter the barrel and barrel, if the oil or water discharge indicators do not meet the requirements, as long as the adjustment of the water height of the outlet can be conveniently meet the requirements. Bucket and bucket liquid level control is a mature technology is easy to implement, can run reliably.

The composition and measurement principle of 2 oil well metering device

Single Jinglai oil by three-phase separation, crude oil into the oil drum, when the liquid level reaches the floating ball, floating ball sends a signal to the pneumatic diaphragm valve is fully open oil discharge, oil through online moisture analyzer, scraper flowmeter, thin film valve discharge; after the separation of the water pipe water weir overflow, into the collection bucket. Similarly, when the water level rises to the floating ball valve is opened, film drainage, water flow meter, the discharge valve through the film, when the oil or water level drop to a lower float ball valve closed position, film, oil or water down a bucket of the accumulation of. In the gas outlet at the top of the separator, a temperature, pressure transmitter, filter, gas flowmeter, automatic pressure regulating valve, a single flow valve. A dosing device into the oil pipeline of the three-phase separator is arranged, can continuously to the oil adding demulsifier.

The main technical indexes of 3 three-phase separator

Structure size: Phi 1600 * 4300

Working pressure: 0.6MPa

Working temperature: 40 to 47 DEG C

Liquid handling capacity: 200m 3 /d

Liquid residence time: 30min

After the separation index: the oil in water is less than or equal to 30%

Oily sewage is less than or equal to 0.4%


4 advantages in the measurement of the separator

(1) by use of a vertical separator, allowing the oil-water interface in a larger range of fluctuation, and can control the separation effect.

(2) using the set of drums, the water collection barrel, adjustable water weir structure, the control method to control the oil-water interface directly into the liquid level difficult to control and easy to implement switch control.

(3) intermittent discharge way of making the range a meter can be adapted to yield difference of each oil well disparity, namely in the separator processing range, no matter how many what wells in production, as long as good control of flowmeter before and after the pressure, flow meter will not over range in measurement. Therefore in the metering stations do not have a plurality of flow meter with different range to adapt to various wells yield measurement of uneven.

(4) the settlement separation process to the interior of the separator is not disturbed flow of liquid drainage, the separation effect is not affected.

The main instrument of 5 and three phase separator matching

Elastic scraper flowmeter, the amount of oil, the amount of water used for precision: + 1%

Online moisture analyzer (0% ~ 100%) accuracy: + 2%

Gas flowmeter accuracy: + 1%

Single chip computer and print output device

6 test results

The three-phase separation efficiency to meet the requirements of measurement. Moisture content 30% < oil; oil in water < 0.4%; adjustable weir pipe control oil-water interface active, flexible, very effective II, make oily water content and water to control the rate eventually separated oil, which is a breakthrough on the technology; single chip microcomputer used for oil well measurement, control of oil, water level, automatic collection of oil, gas, water flow rate and temperature signal, pressure signal and processing it, operation, may at any time or timing print results.


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