RU2408868C2 - Method of detecting solid fraction inclusions in gas stream - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of detecting solid fraction inclusions in a gas stream is based on recording the number of collisions of solid fraction inclusions with the inner surface of a pipe. Recording is carried out by receiving acoustic signals generated during collision using sensors on the outer surface of the pipe. An acoustic signal arising upon collision of an inclusion with the inner surface of the pipe is received in at least two points spaced apart on the surface of the pipe. A collision is recorded if the difference in arrival time of the acoustic signal at these points corresponds to given ratios, i.e. the ratio of distances between sensors to time difference for arrival of waves at the sensors.

EFFECT: high accuracy, broader functionalities and field of use of the sensor for detecting solid fraction inclusions in a gas stream.

2 cl, 2 dwg

Description

The invention relates to a method for providing storage and transportation of natural gas and can be used in the gas industry.

When analyzing the removal of sand from gas wells, the main issue is the assessment of the tolerance of the removal, while the admissible refers to the removal of sand that does not exceed the emergency operating standards of the wells.

The control of the removal of both solid and liquid impurities from gas wells should be level, with a breakdown of the entire recording range into levels, and the numerical values of the impurity concentration boundaries at each level should correspond to the needs of gas production technological services.

An analysis of the known technical solutions shows that the measurement of the mass of dispersed solid impurities in the gas stream can be performed by invasive detectors.

A known method of controlling the removal of sand from a gas well (RF patent No. 2285909, published October 20, 2006), according to which a rod coated with a gummy substance is introduced into the gas stream. Maintain the rod in the stream for a while and then remove. The gummy substance with grains of sand stuck in it is abundantly washed with a solvent and the resulting solution is filtered. The presence and amount of sediment is used to judge the fact and intensity of sand removal.

Also known is a method and device for controlling the mass flow rate of crushed solid material transported through a pneumatic pipeline (RF patent No. 2280843, published July 27, 2006), according to which a dense gas stream is formed from the carrier gas stream by means of a nozzle located in the inlet pipe of the measuring chamber particles suspended in it. The formed jet is directed to the front surface of the head of the acoustic sensor (reflector) in the form of a rod located in the measuring chamber on the axis of the inlet pipe. An acoustic sensor that perceives the impact of particles of solid material is connected to an acoustic transducer that measures the frequency and amplitude of the acoustic waves generated in the rod, which determine the mass flow rate.

The disadvantage of the above methods is the need for intervention in the design of the gas pipeline, the complexity of installation and maintenance, the fragility of the elements immersed in the gas stream with sand, due to abrasive wear. In this regard, the development of non-invasive solids detectors becomes relevant. They must determine the presence and concentration of solid impurities (sand) in the gas stream, while installing them on the outer surface of the gas pipe.

Existing non-invasive acoustic devices (sensors) for recording sand removal from gas wells have a common fundamental drawback - the absence of a control zone localized on the pipe with a known shape and area, exclusively within which the acts of collisions of individual grains of sand with the inner surface of the pipe should be recorded. As a result, such non-invasive detectors respond to extraneous noise, including from sand, acting on the inner surface of the pipe at uncontrolled distances from their installation site. Such noises, in actual operating conditions of gas storages (wells), can be at the same level with the recorded useful signals.

A known method of recording sand in a gas stream is a Particle Monitor with digital signal processing DSP-06 company ClampOn (www.clampon.com.).

The method consists in the fact that a block containing one piezoelectric sensor and a processor unit for processing the sensor signal is installed on the gas pipeline. The problem of noise selection and the selection of useful signals from impacts of solid particles on the inner surface of the pipe is solved using computer technology and the application of various mathematical methods for signal processing.

The method implemented in the Particle Monitor DSP-06 is the closest in technical essence to the claimed method and is therefore selected as a prototype.

The disadvantages of the prototype:

- lack of a localized control zone with known geometric characteristics;

- the need to use sufficiently powerful computing equipment (the minimum requirement is a Pentium III processor, or its equivalent with 512 MB RAM) and, accordingly, high power consumption (at the level of units of watts). High energy consumption does not allow the use of devices based on this method in the absence of stationary power supply, that is, directly at the mouth of gas wells, where the level of extraneous noise is minimal;

- the need to use cable lines.

The objective of the proposed method is to increase accuracy, expand the functionality and scope of the registrar of inclusions of solid fractions in the gas stream.

To achieve a technical result in the method for recording inclusions of solid fractions in a gas stream, which consists in registering the number of collisions of inclusions of solid fractions with the inner surface of the pipe by receiving acoustic signals generated by the collision, sensors located on the outer surface of the pipe are carried out by receiving acoustic signals at least at two points spatially spaced along the pipe surface, and a collision is recorded if the difference in the arrival times of the acoustic about the signal at these points satisfies the given relationships. As initial data for given ratios, one can take the distance between the sensors and the difference in the arrival of the wave to the sensors.

Thus, the method is based on the principle of locating the source of the acoustic signal, which consists of analog processing of the latter, with the separation of the frequencies of thickness vibrations of the pipe wall, and the simplest digital processing algorithm, followed by counting the number of events.

The drawing shows the experimental curves of the sensitivity zones of a device containing two acoustic sensors. Curve a) corresponds to the specified permissible time of the channel response time τ = 18.9 μs, curve b) corresponds to τ = 9.45 μs.

Developed pilot samples of devices on which the feasibility of the proposed method was demonstrated.

The possibility of using the principle of location in the detection of solid inclusions was theoretically studied for the case of a flat location, given that the analysis of collisions of sand grains with the inner surface of the pipe is quite correct to conduct on its flat scan, since the wall thickness of the pipe is much less than the diameter (for example, a pipe with an inner diameter of 100 mm has wall thickness equal to 7 mm).

Let on the indicated scan, the Cartesian coordinate plane (X0Y), the axis 0Y coincide with the axis of the pipe, the axis 0X lies in the lateral cylindrical surface, and the system of two acoustic sensors D1 and D2 is located so that the coordinates of the first of them are equal (0, -с ), the second - (0, s). Suppose further that the collision of a grain of sand with a plane occurs at an arbitrary point with coordinates (x, y).

The sensitivity zone of the acoustic system will be considered the part of the coordinate plane, the hit of a grain of sand on which is an event recorded, the hit of a grain of sand on a plane outside the zone should be ignored by the system. The criterion defining the sensitivity zone of the two sensors under consideration is defined as follows: the time difference in the arrival of an acoustic wave to them should not exceed a certain specified value τ. Then the boundaries of the sensitivity zone are determined by the equality of the parameter τ and the detected time difference. This is equivalent to the following condition: at the boundary of the sensitivity zone, the difference in the distances from the point of impact of the sand with the coordinate plane to the points at which the sensors are located is a constant value.

Thus, the boundaries of the sensitivity zone of the system of two sensors are a hyperbola, in the foci of which the sensors are located, the zone itself is a part of the coordinate plane bounded by the branches of the hyperbola and containing its imaginary axis.

Therefore, to uniquely determine the sensitivity zone of the system of two sensors located on a plane of material with a known acoustic wave propagation velocity, it is necessary to specify two quantities:

- the distance between the sensors,

- the time difference between the arrival of the wave to the sensors τ.

Since setting the time difference τ, at a fixed distance between the sensors c, uniquely determines the boundaries and, accordingly, the area of the sensitivity zone, measuring the number of collisions of sand grains with the zone per unit time allows us to solve the problem of determining the quantitative characteristics of sand removal. In addition, by changing the parameter τ (for example, by a command via radio or cable channel), it is possible to control the area of the sensitivity zone, that is, the resolution of the device.

The sensitivity zone of a system of 3 sensors - D0, D1, D2 can be defined as the intersection of the sensitivity zones of two subsystems D0-D1 and D0-D2.

A pilot instance of the device with two sensors was tested to experimentally determine the boundaries of the sensitivity zone. The tests were carried out at different values of the difference in time τ of arrival of acoustic pulses to the sensors generated by particle impacts. The results obtained (see the drawing) showed good agreement with the theory, which proves the possibility of the invention.

The advantages of this development are:

- the possibility of forming a closed control zone with an adjustable area during the measurement, which allows, on the one hand, to significantly reduce the influence of extraneous noise on the measurement accuracy, and on the other, to obtain quantitative characteristics of sand removal;

- non-invasive method of measurement, ease of external installation, appropriate on the "knee" or in places of narrowing of the flow, where collisions of grains of sand with the inner surface of the pipe are most likely;

- low power consumption, the possibility of autonomous operation during the year directly on the mouths of gas wells;

- low cost;

- simplicity, and therefore reliability;

- the ability to quickly and mass implementation.

Claims (2)

1. The method of recording inclusions of solid fractions in the gas stream, based on recording the number of collisions of inclusions of solid fractions with the inner surface of the pipe by receiving acoustic signals generated by the collision by sensors located on the outer surface of the pipe, characterized in that the acoustic signal arising from the collision inclusions with the inner surface of the pipe, take at least two points spatially spaced along the surface of the pipe, and the collision is recorded if the difference acoustic signal arrival times at these points corresponds to a predetermined ratio. 2. The method according to claim 1, characterized in that as given take the ratio between the distances between the sensors and the time difference between the arrival of the wave to the sensors.