RU2382359C2 - Method for monitoring of multiphase flow in pipeline - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: application: for monitoring of multiphase flow in pipeline. Pipeline with monitored medium is scanned with ultrasonic pulses, pulses that have passed through medium and have been reflected from interphase boundary are received, their amplitudes are measured, as well as runtime, which are used to identify nature of multiphase flow motion, which differs by the fact that additionally pulses are received, which have been multiply reflected from boundary of "pipe metal - medium", time of their reverberation is identified, which is used to judge on medium properties in the following manner: smooth increase of reverberation time confirms increase of gas phase content in liquid, sharp rise identifies crossing of interphase boundary "liquid-gas", sharp reduction of reverberation time characterises crossing of boundaries of liquids with various acoustic properties in case of stratified flow.

EFFECT: improved accuracy and information value of multiphase flow monitoring in pipeline.

2 dwg

Description

The invention relates to instrumentation and can be used to determine the type of multiphase flow in the pipeline during its operation.

A known method of controlling a multiphase flow in a pipeline [1], which consists in placing a group of transducers around the circumference of the pipeline in the same plane of its cross section, multiphase flow is heard by ultrasonic vibrations, receive pulses of ultrasonic vibrations transmitted through the flow and reflected from the discontinuities of the multiphase flow, measure them amplitudes and travel times, convert them into a digital form convenient for processing and compare with a set of digital ones available in the flash memory of the microprocessor module standards corresponding to different multiphase flows, and the nature of the multiphase flow is determined by comparison. The disadvantage of this method is the complexity of its implementation, due to the need to ensure tight acoustic contact between all the transducers and the surface of the pipeline, the presence of many digital standards, which must take into account, in addition to all possible variations in the nature of multiphase flow, wall thickness, diameter of the pipeline and individual acoustic characteristics of the transducers.

A known method of monitoring flow discontinuities [2], which consists in the fact that the pipeline with a controlled medium is sounded by ultrasonic pulses in two mutually perpendicular directions, receive pulses and pulses transmitted through the medium, reflected from the phase boundary, measure their amplitudes and travel time data are judged on the concentration of the gas phase and the flow regime.

The disadvantages of the method are:

1) low accuracy of the method, due to the complexity of the exact location of the sensor receivers on the acoustic axis of the sensor emitters;

2) low information content of the recorded parameters and, as a consequence, the complexity of the correct interpretation of the data obtained;

3) the impossibility of accurately determining the location of the phase boundary, because the velocity of the ultrasonic pulse in the measured medium is unknown under the existing conditions (pressure, temperature, speed).

The objective of the invention is to improve the accuracy and information content of the method.

The problem is solved in that in the method of multiphase flow in the pipeline, which consists in the fact that the pipeline with a controlled medium is sounded by ultrasonic pulses, the pulses transmitted through the medium are received, and the pulses reflected from the phase boundary measure their amplitudes and travel time, according to which determine the nature of the motion of the multiphase flow, additionally take pulses that are repeatedly reflected from the boundary “metal pipe - medium”, determine the time of their reverberation, which is used to judge the properties of the medium with In the following way: a smooth increase in the reverberation time indicates an increase in the content of the gas phase in the liquid, a sharp one indicates the intersection of the liquid – gas interface, a sharp decrease in the reverberation time characterizes the intersection of the boundaries of liquids with different acoustic properties in a layered flow.

As an explanation of the essence of the claimed invention, the following.

When solving the problems of protection against corrosion pipelines, it is important to know the presence and ratio of the volumes of the phases of liquid hydrocarbon (for example, gas condensate) and produced water and the nature of the multiphase flow. The difficulty of identifying the interface between such liquids by ultrasound is due to the small difference in their acoustic properties. Therefore, the level of the signal received from the phase boundary “liquid hydrocarbon - formation water” is comparable to the noise level in the electro-acoustic path of the flaw detector and is an uninformative parameter.

The difference in the levels of the pulse reflected from the boundaries “pipe metal - liquid hydrocarbon” and “pipe metal - produced water” is also small and amounts to about 3-4%, however, with a multiple reflected signal it is not difficult to fix by the length of the reverberation time of the multiple reflected pulse.

A multiple reflected pulse from the liquid phase boundaries cannot be achieved due to the attenuation of ultrasonic pulses in the liquid.

Figures 1 and 2 show the waveforms of a flaw detector with pulses repeatedly reflected from the boundary "pipe metal - gas condensate" and "pipe metal - produced water", respectively.

A method of controlling a multiphase flow in a pipeline is as follows.

By means of a piezoelectric transducer, ultrasonic pulses are introduced into the metal of the pipeline pipe. Multiple reflected pulses reflected from the “metal pipe - medium” boundary are obtained. The pulse reverberation time is determined (FIG. 1). The transducer scans the pipeline surface by moving along its circumference. An increase in the reverberation time indicates a decrease in the density of the medium adjacent to the metal of the pipe: smooth - about an increase in the content of the gas phase in the liquid, sharp - about the intersection of the liquid – gas interface.

A decrease in reverberation time indicates an increase in the density of the medium. When the transducer crosses the boundaries of liquids with various acoustic properties during a stratified flow, a sharp decrease in the reverberation time of pulses is observed (Fig. 2).

The place of change of the reverberation time is marked on the pipeline as the place of passage of the phase boundary of the flow.

Example. For the effective use of corrosion protection means of the Vuktyl-Ukhta condensate pipeline, it is necessary to identify areas with a stratified flow of the medium as the most dangerous in terms of corrosion. The transported medium consists of a gas phase, a gas condensate phase and a formation water phase. With a stratified flow of the medium, they are located in the pipeline depending on their density: below - water, above - gas, in the middle of the cavity of the pipeline - condensate.

To implement the method, a general-purpose ultrasonic flaw detector UD-2-12 and a piezoelectric transducer (PEP) P111-2.5-12-002 are used.

Install the probe on the outer side surface of the pipeline (the border "metal pipe - condensate"). Multiply reflected pulses reflected from the boundary are obtained (FIG. 1). Move the probe down the circumference of the pipeline. A sharp decrease in the reverberation time (Fig. 2) indicates the transition of the PED interface between the phases "condensate - water". By scanning the surface of the pipeline upward from the lateral surface to increase the reverberation time, the interface “condensate - gas” is marked.

Information sources

1. Patent for the invention of the Russian Federation No. 2198397, IPC 7 G01N 29/02, publ. 02.10.2003, O.N. Kuzyakov and S.A. Dudko. A method of controlling a multiphase flow in a pipeline (analog).

2. AS No. 1631401 of the USSR, IPC 5 G01N 29/00, publ. 02/28/1991, bull. No. 8. E.S. Chistyakov and Yu.I. Dyshleva. A method for monitoring fluid flow discontinuities in a pipeline (prototype).

Claims (1)

A method of controlling a multiphase flow in a pipeline, which consists in the fact that a pipeline with a controlled medium is sounded by ultrasonic pulses, receive pulses transmitted through the medium, and pulses reflected from the phase boundary, measure their amplitudes and travel time, which determine the nature of the movement of the multiphase flow , characterized in that they additionally receive pulses repeatedly reflected from the boundary “pipe metal - medium", determine the time of their reverberation, which is used to judge the properties of the medium as follows azom: smooth increase in reverberation time indicates an increase in the content of gas phase into the liquid, the sharp - of the intersection of the interface phase "liquid - gas", a sharp decrease reverberation time characterizes the intersection boundaries of liquids with different acoustic properties when stratified flow.

Images