RU2259556C1 - Method for determining volumetric share of water in pipeline with gas-liquid mixture - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: method includes coaxially exciting effect from water component of gas-liquid mixture on pipe of dielectric material and measuring changes of resonance frequencies, exciting electromagnetic field in two identical coil resonators, positioned coaxially on pipe of dielectric material, two identical supporting and measuring auto-generators. Electric field of coil of support auto-generator is screened from gas-liquid mixture. frequencies of auto-generators are evened in absence of gas-liquid mixture in pipeline. Proportionality coefficient of difference of frequencies of auto-generators is set relatively to determined volumetric share of water in presence of gas-liquid mixture with known volumetric share of water.

EFFECT: higher precision.

Description

The present invention relates to the field of measuring equipment and can be used in gas condensate and oil fields in multicomponent flow meters to measure water flow without separation into fractions of a gas-liquid mixture (GHS) of production products directly at the wells or in the reservoirs of primary processing.

In the flow metering of GHS, the method of separation of components in separation plants with periodic measurement of their costs is widely used. Recently, real-time flow metering of multicomponent flows has been developing intensively, mainly for oil production, with the integrated use of classic single-phase flow meters: turbine, diaphragm, Coriolis, Venturi nozzles and others. However, such measuring tools are not widely used, mainly due to low reliability, when operating in gas condensate and oil and gas fields.

A known method of measuring the permeability of liquid dielectrics, in particular biological fluids (AS No. 13232131, USSR, MKI G 01 N 22/00, publ. 7.07.87), including the excitation of reference and measuring oscillators of electromagnetic fields in two ring dielectric resonators, placing an ampoule with the test liquid in the axial hole of the resonator of the measuring oscillator, mixing the frequencies of the oscillators with a mixer and determining the dielectric constant from the frequency of the signal at the output of the mixer.

However, the implementation of this method in a pipeline with GHS is difficult due to the open nature of the electromagnetic field in the ring dielectric resonator, in addition, the conductivity of the liquid fraction will affect the results of determining the dielectric constant due to the presence of salts in water.

A known method of determining the volumetric water content in the GHS (Daisake Yamazaki, Shuichi Haruyama. Development of multiphase flowmeter without radioactive sourse. - Yokogava, Electric corporation: In the collection - BP Exploration Multiphase Mesurement Course, 1997, p. 69), in which two ring electrodes placed in a pipeline parallel to each other and coaxially to the pipe, one of them is connected to an alternator, the other to an alternating current meter, and the capacitive current between the electrodes is measured. The current value determines the capacitance between the electrodes, which depends on the dielectric constant of the GHS, which, in turn, depends on the volumetric water content in the GHS.

However, the described method does not provide the necessary measurement accuracy due to the small extent of the interaction site and the lack of measures to take into account the salinity of the water, affecting its conductivity.

Closest to the claimed is a method for determining the relative proportions of oil, gas and water in the pipeline according to US patent G 01 N 22/04 US 5389883 "Mesurement of gas and water content in oil", 1995 (prototype). By placing a plurality of coil resonators having different resonant frequencies coaxially on a pipe of dielectric material and measuring changes in their resonant frequencies, the proportions of oil, water and gas flowing through the pipe are calculated.

The disadvantage of this method is the lack of consideration of the influence of salinity on the measurement results, as well as the difficulty of calibrating many coil resonators.

The technical result of the invention is to increase the accuracy of determining the volumetric water content in the pipeline with GHS by eliminating the influence of its salinity on the measurement results.

The technical result is achieved by the fact that in the method for determining the volume fraction of water in the pipeline with GHS, including the excitation of electromagnetic fields in coil resonators placed coaxially on a pipe of dielectric material, the effect of the aqueous component of the gas-liquid mixture on the field frequencies and the measurement of changes in resonant frequencies excite the electromagnetic field in two identical coil resonators with two identical reference and measuring oscillators and screen the electric field of the coil of the reference oscillator generator of the gas-liquid mixture from the frequency oscillators are aligned in the absence of gas-liquid mixture in line and set the proportionality coefficient difference frequency oscillators with respect to the determined volumetric proportion of water in the presence of GLM with a known volume fraction of water.

In this case, when the frequencies of the reference and measuring oscillators are aligned, the water conductivity makes the same contribution to the frequency shift of the reference and measuring oscillators due to the exclusion of the influence of the frequency dispersion of conductivity, and the difference in their frequencies will be determined only by the influence of the dielectric constant of the GHS proportional to the volume fraction of water.

The volume fraction of water is measured as follows.

Using automatic oscillators, they excite a magnetic field inside the coil of the reference oscillator and an electromagnetic field inside the coil of the measuring oscillator, tune the oscillators to the same frequency and measure its value F _o in the absence of GHS in the pipeline.

During calibration, the frequencies of the reference F _op and the measuring F _{ISM of} autogenerators are measured in the presence of a GHS with a known volumetric water content in the pipeline. The change in the frequency of the reference oscillator ΔF _op equal to

ΔF _op = F _op -F _o = ΔF _magn

where F _o - the frequency of the reference oscillator in the absence of GHS;

F _op - the frequency of the reference oscillator in the presence of GHS;

ΔF _magn - change in the frequency of the reference oscillator due to changes in the magnetic field in the presence of GHS,

due to the influence of the conductivity (salinity) of water on the magnetic field of the coil of the reference oscillator, and the change in the frequency of the measuring oscillator ΔF _ISM equal to

ΔF_изм=F_изм-F_о=ΔF_магн+ΔF_электр,

.DELTA.F _{ism ism} -F = F = ΔF _{of the mag} + ΔF _electric,

where F _o - the frequency of the measuring oscillator in the absence of GHS;

F _ISM ^- frequency measuring oscillator in the presence of GHS;

ΔF _magn - change in the frequency of the measuring oscillator due to changes in the magnetic field in the presence of GHS;

ΔF _electron is a change in the frequency of the measuring oscillator due to a change in the electric field in the presence of the GHS due to the influence of both the conductivity of the water on the magnetic field of the coil of the measuring oscillator and the dielectric constant of the GHS on the electric field of this coil.

The dielectric constant of the GHS consists of the dielectric constant of the gas close to 1, and the increment of the dielectric constant Δε _in , caused by the appearance of water in the pipeline. When the volume fraction of water in the GHS Ж _in <0.5, the change in the frequency ΔF _{electr is} proportional to the increment Δε _in :

ΔF _electr . = Δε _in · F _o / 2.

In turn, the increment Δε _in proportional to the volume fraction of water Θ _in in the GHS:

Δε _in = logε _in · ln10 · Θ _in = 4.39Θ _in ,

where ε _in = 81 is the dielectric constant of water.

When the coils are identical in the difference in frequency changes

_Edited -ΔF _op ΔF = ΔF _{magn RE} + ΔF = ΔF -ΔF _{magn RE,}

changes caused by the influence of conductivity cancel each other out, therefore the frequency difference

(F _meas -F _o ) - (F _op -F _o ) = F _meas -F _op = ΔF _electron , is determined only by the increment Δε _{in the} dielectric constant of the GHS, proportional to the volume fraction of water Θ _in in the GHS. The proportionality coefficient k (changing the frequency difference by one percent of the volume fraction of water in the GHS) is set during calibration if there is a GHS in the pipeline with a known volumetric water content according to the formula:

k = (F _meas -F _op ) / Θ _c .

During operation, calculate the volumetric fraction of water _в in GHS according to the formula:

Θ _in = (F _meas -F _op ) / k,

where F _ISM - frequency measuring oscillator in the presence of GHS;

F _op - the frequency of the reference oscillator in the presence of GHS;

k is the proportionality coefficient established during calibration. Moreover, the value of the coefficient k does not depend on the salinity of water in the GHS.

As an example of a specific implementation, Table 1 shows the technical result when determining the volume fraction of water by a coil without shielding an electric field and by the proposed method with two coils with shielding a field in one of them for different specified volume fractions of water in the GHS.

Table 1 Preset Θ _in ,% Measured Θ _in one coil,% Error,% Measured Θ _{in the} proposed method,% Error,% Salinity of water, 3% 5 4.7 -6.0 4.8 -4.0 fifteen 16,0 + 6.7 15,5 +3.3 thirty 27.8 -7.3 28.9 -3.7 45 48.7 +8.2 46.8 +4.0 Salinity of water, 6% 5 4.6 -8.0 4.8 -4.0 fifteen 16.1 +7.3 15.7 +4.7 thirty 27.5 -8.3 28.7 -4.3 45 49.6 +10.2 47.0 +4.4

Improving the accuracy of determining the volume fraction of water in the pipeline with GHS contributes to lower costs in the collector sections of the primary processing of gas condensate or oil and gas fields, as well as more accurate prediction of well life.

Claims (1)

A method for determining the volume fraction of water in a pipeline with a gas-liquid mixture, including the excitation of electromagnetic fields in coil resonators placed coaxially on a pipe of dielectric material, the effect of the aqueous component of the gas-liquid mixture on field frequencies and measuring changes in resonant frequencies, characterized in that they excite an electromagnetic field in two identical coil resonators with two identical reference and measuring oscillators, shield the electric field of the coil of the reference oscillator pa from the gas-liquid mixture equalize the frequency oscillators in the absence of gas-liquid mixture in line and set the proportionality coefficient oscillators frequency differences with respect to the determined volumetric proportion of water in the presence of gas-liquid mixtures with a known volume fraction of water.