RU2135984C1 - Method of determining water content in oil stream of an oil deposit - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: method is based on using a parameter of electromagnetic oscillations passed through controlled stream, mentioned parameter being electromagnetic oscillation frequency. Water content is calculated in terms of equation presented in description. EFFECT: increased determination accuracy. 1 dwg

Description

 The invention relates to the field of measuring equipment and can be used in process control systems.

 A known method implemented by a hydrometer for crude oil (V.A. Viktorov et al. "Radio wave measurements of technological processes", M .: "Energoatomizdat", 1989, p. 170), in which the phase difference of the waves in the measuring and reference waveguides filled respectively watered and reference oil, determine the moisture content of the oil flow of one field.

 The disadvantage of this known method is the complexity of the procedure for determining moisture content, associated with the need to form simultaneously two - measuring and reference channels.

 The closest technical solution to the proposed one is the method of determining moisture content adopted by the author for the prototype (V.A. Viktorov et al. "High-frequency method for measuring non-electric quantities", Moscow: Nauka, 1978, p. 253). In the device that implements this method, the oscillations of the microwave generator pass through ferrite gates and a directional coupler connected between them into the transmitting horn antenna. An electromagnetic wave transmitted through the controlled medium enters the receiving horn antenna and then into the detector section to measure the moisture-related power transmitted through the medium.

 The disadvantage of this method should be considered the error due to the influence of various disturbing effects on the power of the electromagnetic wave during its measurement.

 The objective of the proposed technical solution is to increase the accuracy of measuring the moisture content of the oil stream.

где f_пр - частота прошедших через поток нефти электромагнитных колебаний, λ - длина волны электромагнитных колебаний в свободном пространстве, C - скорость волны электромагнитных колебаний в свободном пространстве, ε_н - диэлектрическая проницаемость нефти.The problem is achieved in that in the method for determining the moisture content of the oil flow of one field, based on the use of the parameter of electromagnetic waves transmitted through the controlled stream, their frequency is used as an informative parameter of electromagnetic waves and the moisture content W of the oil stream is calculated by the formula

where f _CR - the frequency of electromagnetic waves transmitted through the oil flow, λ is the wavelength of electromagnetic waves in free space, C is the wave velocity of electromagnetic waves in free space, ε _n is the dielectric constant of the oil.

 The essence of the claimed invention, characterized by a combination of the above features, is that when exposed to electromagnetic flow by electromagnetic waves, their frequency receives information about the moisture content of the controlled stream.

 The presence in the claimed method of a combination of the essential features listed above allows us to solve the problem of determining the moisture content of the oil flow based on the use of the parameter of electromagnetic waves transmitted through the controlled oil flow with the desired technical result, i.e. high accuracy of measurement.

 The drawing shows a functional diagram of a device that implements the proposed method.

 A device that implements this technical solution contains an electromagnetic oscillation generator 1, a transmitting and receiving horn antenna (emitter and receiver, respectively) 2 and 3, mounted diametrically on the outer surface of the pipeline 4, and a frequency counter 5.

 The proposed method is based on determining the dependence of the frequency of electromagnetic waves on the phase velocity of their waves during its propagation through the water emulsion stream.

где C - скорость волны в свободном пространстве, v_ф - фазовая скорость волны в потоке, λ - длина волны в свободном пространстве, λ_зам - длина волны в замедляющем водоэмулсионном потоке. С другой стороны, из электродинамики известно, что при распространении электромагнитной волны по диэлектрической среде для параметра v_ф можно записать

где ε - диэлектрическая проницаемость контролируемой среды.In the case under consideration, the flooded oil flow due to the relatively high dielectric constant of water (ε _at ≃ 80) should be considered as a decelerating system that affects the propagation velocity of an electromagnetic wave as it passes through a controlled oil flow. Then, as follows from the work of I. V. Lebedev, “Microwave Technique and Devices,” Moscow: Vysshaya Shkola, 1970, p. 378, for the deceleration coefficient K _{deputy of a} given water-based oil flow we will have

where C is the speed of the wave in free space, v _f is the phase velocity of the wave in the stream, λ is the wavelength in free space, λ _deputy is the wavelength in the decelerating water emulsion flow. On the other hand, from electrodynamics it is known that when an electromagnetic wave propagates through a dielectric medium for parameter v _f, we can write

where ε is the dielectric constant of the controlled medium.

Сопоставление выражений (2) и (3) позволяет получить равенство, характеризующее зависимость фазовой скорости волны в обводненом потоке от ее длины
λv_ф= Cλ_зам.
Анализ этого выражения показывает, что в этом случае любое изменение фазовой скорости, обусловленное непостоянством диэлектрической проницаемости контролируемой среды, может привести к увеличению или уменьшению длины замедляющей волны. Следовательно, согласно эффекту нормальной дисперсии электромагнитных волн в замедляющих системах при уменьшении фазовой скорости v_ф (увеличении диэлектрической проницаемости ε) частота электромагнитных колебаний в определенном диапазоне длин волн должна расти и наоборот. В силу этого выражение (3) с учетом λ_зам= C/f_зам, где f_зам - частота замедленных водоэмульсионным потоком электромагнитных колебаний, примет следующий вид:

Подставляя в выражение (4) известную зависимость диэлектрической проницаемости обводненного потока нефти (формула Винера) от влагосодержания, получим
λ²f $\genfrac{}{}{0ex}{}{\text{2}}{\text{зам}}$ = C²ε_н+3C²ε_нW,
где ε_н - диэлектрическая проницаемость нефти, W - влагосодержание.From a comparison of formulas (1) and (2), it can be seen that during the interaction of an electromagnetic wave with a water-emulsion oil flow, a wave can slow down, the length of which is defined as

A comparison of expressions (2) and (3) allows us to obtain the equality characterizing the dependence of the phase velocity of the wave in the flooded stream on its length
λv _f = Cλ _deputy.
An analysis of this expression shows that in this case, any change in the phase velocity due to instability of the dielectric constant of the controlled medium can lead to an increase or decrease in the length of the decelerating wave. Therefore, according to the effect of normal dispersion of electromagnetic waves in slowing down systems, with a decrease in the phase velocity v _f (increase in the dielectric constant ε), the frequency of electromagnetic waves in a certain range of wavelengths should increase and vice versa. By virtue of this, expression (3), taking into account λ _deputy = C / f _deputy , where f _deputy is the frequency of electromagnetic oscillations slowed down by the emulsion flow, will take the following form:

Substituting into expression (4) the known dependence of the dielectric constant of the watered oil flow (Wiener formula) on the moisture content, we obtain
λ ² f $\genfrac{}{}{0ex}{}{\text{2}}{\text{deputy}}$ = C ² ε _n + 3C ² ε _n W,
where ε _n is the dielectric constant of oil, W is the moisture content.

Из последнего выражения вытекает, что при постоянном значении диэлектрической проницаемости нефти (одной сортности нефти) по величине частоты замедленных электромагнитных колебаний можно оценить влагосодержание в обводненном потоке нефти.Hence, for moisture content W, we have

From the last expression it follows that at a constant value of the dielectric constant of oil (of the same oil grade), the moisture content in the flooded oil stream can be estimated from the value of the frequency of slowed-down electromagnetic oscillations.

A device that implements the proposed method works as follows. The microwave signal of the electromagnetic oscillation generator 1 through the transmitting horn antenna 2 enters the oil stream flowing through the pipe 4. Then, after interacting with the controlled medium, the signal passes through it and is picked up by the receiving horn antenna (receiver) 3. Electromagnetic oscillations slowed down by the oil flow from the output of the latter served on the frequency meter 5, through which the magnitude of the frequency of the electromagnetic waves transmitted through the flow associated with the moisture content of W. is estimated. Given that in nnom case its removal frequency of the transmitted signal and the measurement made when full flow of water-based receiver cavity oil past frequency f of electromagnetic waves _etc. can be considered equal to the frequency f _deputy.

 Thus, according to the proposed method, based on measuring the frequency of electromagnetic waves transmitted through a water-emulsion oil flow, it is possible to provide a higher accuracy of measuring the moisture content of an oil flow of one field (one oil grade).

Claims (1)

The method for determining the moisture content of the oil flow of one field, in which the oil flow is affected by electromagnetic oscillations and, according to the parameter of electromagnetic waves transmitted through the controlled stream, their moisture content is judged, characterized in that their frequency is used as an informative parameter of electromagnetic waves and the moisture content W of the stream is calculated oil formula

where f _CR - the frequency of electromagnetic waves transmitted through the oil flow;
λ is the wavelength of electromagnetic waves in free space;
C is the wave velocity of electromagnetic waves in free space;
ε _n - dielectric constant of oil.