RU2613335C2 - Device for estimating gas flow carried by bubbles ascending from bottom of water bodies - Google Patents

Abstract

FIELD: physics, measurement technology.

SUBSTANCE: invention relates to devices for remote estimation of gas flow carried by bubbles ascending from the bottom of water bodies, and can be used, for example, in measuring offshore methane flow, carried by bubbles ascending from the upper sediment layer of the bottom. The device consists of an echo sounder, a digital recording system, a control and recording unit, a GPS/GLONASS receiver and a bubble generator, consisting of a gas cylinder, a gas supply system, a bottom platform and a nozzle with a mouthpiece. The introduction of a bottom platform and a mouthpiece in the device enables to dip the nozzle into the upper sediment layer during calibration. As a result, artificial bubbles are coated with particles of the substance of the sediment layer and therefore, in terms of ascending speed and rate of dissolution, virtually do not differ from natural bubbles, which significantly improves accuracy of estimating gas flow.

EFFECT: invention improves accuracy of estimating gas flow.

4 cl, 1 dwg

Description

The invention relates to geophysics, and in particular, to devices for remote assessment of the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs, and can be used, for example, to measure methane flows on the shelf carried by the pop-up bubbles coming from the upper sedimentary layer of the bottom.

Known ultrasonic flow meter components of a multiphase medium in pipelines [RU 2126143 C1, IPC 6 G01F 1/74, G01F 1/66, publ. 02/10/1999], which allows one to estimate the gas flow carried by bubbles floating in water bodies. This device consists of two measuring chambers with emitters and receivers of acoustic pulses, one of which is connected to the unit for measuring the parameters of the pulses, and the other to the unit for measuring the speed of a multiphase medium, while the units are connected to an electronic computer system. An ultrasonic flowmeter of components of a multiphase medium makes it possible to estimate the gas flow carried by the bubbles by the speed of movement of the bubbles and their relative content in water. Using it, one can estimate the gas flow from a local source at the bottom of water bodies.

To evaluate the gas flow from a local source at the bottom of reservoirs, this device must be installed at the bottom of reservoirs with great accuracy relative to the source. In addition, in order to evaluate the gas flow from a vast section of the bottom, it is necessary to carry out a large number of such measurements in series, which is a very time-consuming, expensive, and often impossible exercise.

A device for evaluating the flow of gas carried by bubbles emerging in water [RU 150012 U1, IPC G01S 15/02 (2006.01), publ. 01/27/2015], selected as a prototype, containing an echo sounder connected to a matching unit, to which a digital registration system, a control and recording unit that is connected to a GPS / GLONASS receiver and an echo sounder are connected in series. The bubble generator consists of a series-connected cylinder with gas, a gas supply system and a nozzle lowered into the reservoir. The gas supply system is connected to the control and registration unit.

The accuracy of estimating the gas flow by such a device significantly depends on the characteristics of the upper sedimentary layer of the bottom, from which the bubbles exit into the reservoir. This is due to the fact that in the known device, the bubbles exit the nozzle directly into the water, and the natural bubbles leaving the bottom pass through the upper sedimentary layer. Bubbles passing through the upper sedimentary layer of the reservoirs and leaving the reservoir carry particles of sedimentary layer material on their surface, the chemical composition and quantity of which depends on the physical and chemical characteristics of the substances contained in the upper sedimentary layer of the reservoirs. The presence of such substances on the surface of the bubble significantly affects the rate of ascent and the rate of dissolution of the bubbles. Therefore, the natural bubbles emerging from the upper sedimentary layer of the bottom and artificial bubbles coming out of the nozzle directly into the water, with the same gas flow, can significantly differ in the ascent rate and the dissolution rate. This leads to the fact that for the same gas stream, the signals of backscattering sound from pop-up natural and artificial bubbles will be different. Thus, an error occurs when evaluating the gas flow.

The objective of the invention is to improve the accuracy of estimation of the gas flow carried by the pop-up bubbles emerging from the bottom of the reservoirs.

The proposed device for evaluating the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs, as in the prototype, contains an echo sounder, which is connected to the control and registration unit, which is connected to the GPS / GLONASS receiver and echo sounder, via a matching unit and a digital registration system , a bubble generator comprising a gas cylinder connected to a gas supply system, and a nozzle lowered into a reservoir, the gas supply system being connected to a control and registration unit.

According to the invention, a platform is lowered to the gas supply system, a nozzle is lowered to the bottom of the reservoir, on the lateral surface of which, at the bottom, an nozzle is fixed, at the end of which a nozzle is fixed, the end of which, facing the bottom sediments, is made tapering.

The bottom platform can be made in the form of a cylinder of steel.

The nozzle can be made of a steel tube and mounted on the bottom platform at an angle of 30-45 ° to its vertical.

The nozzle can be made of steel in the form of a cone.

The achievement of the claimed technical result, namely, increasing the accuracy of estimating the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs, is due to the fact that when calibrating the device using a bubble generator, the bubbles are as close as possible to natural bubbles emerging from the upper sedimentary layer bottom. This happens due to the fact that artificial bubbles exit the nozzle in the upper sedimentary layer of the bottom and pass through this layer before exiting the bottom into the water column. As a result, they are covered with particles of sedimentary layer material and therefore practically do not differ from natural bubbles in their ascent rate and dissolution rate. Technically, this is achieved by the fact that the nozzle has a nozzle at its end and is installed on the bottom platform, which is lowered to the bottom of the reservoir, and when the bottom platform is placed on the bottom of the reservoir, the nozzle with the nozzle is immersed to a certain depth in the upper sedimentary layer of the bottom.

In FIG. 1 is a block diagram of an apparatus for evaluating a gas flow carried by pop-up bubbles exiting the bottom of water bodies.

The device for evaluating the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs contains a control and registration unit 1 (BUR), which is connected to an echo sounder 2 (E), to which a matching unit 3 (BS), a digital registration system 4 ( SCR), which is connected to the control and registration unit 1 (BUR), which is connected to the GPS / GLONASS receiver 5 (P). The bubble generator 6 (GP) contains a gas cylinder 7 (BG) connected in series, a gas supply system 8 (LNG), a bottom platform 9 (DP) mounted on its side surface, below, at an angle of 30-45 ° to the vertical, a nozzle 10 (C), at the end of which a nozzle 11 (H) is fixed, the end of which, facing the bottom sediments, is made in the form of a cone.

A device for evaluating the flow of gas carried by the pop-up bubbles leaving the bottom of the reservoirs is installed on the vessel. Preliminary in a given area using a bubble generator 6 (GP) carry out calibration. To do this, the ship becomes drift in the area where there are no natural pop-up bubbles. Then, the bottom platform 9 (DP) connected to the gas supply system 8 (LNG) and the nozzle 10 (C) fixed on it, at the end of which a nozzle 11 (NAS) are lowered, are lowered to the bottom of the reservoir directly under the echo sounder 2 (E). When installing the bottom platform 9 (DP) at the bottom of the reservoir, the nozzle 10 (C) with the nozzle 11 (NAS) installed at its end is immersed in the upper sedimentary layer of the bottom. The nozzle 11 (NAS) protects the nozzle 10 (C) from mechanical damage and clogging by sedimentary rocks when it is immersed in the upper layer of bottom sediments. At the command of the control and registration unit 1 (BUR), the gas supply system 8 (LNG), to which the gas comes from the gas cylinder 7 (BG), provides a predetermined gas flow entering the bottom platform 9 (DP) and exiting the nozzle 10 (C) into the upper sedimentary layer in the form of bubbles. Bubbles pass through the upper sedimentary layer and, coming out of the bottom of the reservoir, float in the water column. At the same time, an acoustic signal from the echo sounder 2 (E) is emitted in the direction of the bottom. The same echo sounder 2 (E) receives signals for backscattering sound from emerging from the bottom and pop-up bubbles. Sound backscatter signals through the matching unit 3 (BS) and digital recording system 4 (SCR) are sent to the control and recording unit 1 (BUR), where they are processed and displayed in the form of an echogram that shows the distribution of the sound backscatter signal under the echo sounder 2 (E ) By changing the magnitude of the gas flow exiting the nozzle 10 (C), a calibration dependence of the magnitude of the signal of backscattering sound on the magnitude of the gas flow for various depths N.

Then, the natural gas flow carried by the pop-up bubbles is estimated in a given area. Depending on the task, the measurements are carried out in the drift or on the go of the vessel on which the proposed device is installed. On command from the control and registration unit 1 (BUR), the acoustic signal of the echo sounder 2 (E) is emitted in the direction of the bottom. The same echo sounder 2 (E) receives signals for backscattering sound from emerging from the bottom and pop-up bubbles. Sound backscatter signals through the matching unit 3 (BS) and the digital recording system 4 (SCR) are sent to the control and registration unit 1 (BUR), where they are processed and displayed in the form of an echogram. Using the previously obtained calibration dependence for depth H, the gas flow carried by the pop-up bubbles is estimated from the value of the backscattered sound signal from the bubbles. At the same time, a signal from the GPS / GLONASS receiver 5 (P) is received at the control and registration unit 1 (BUR) to record the current coordinates. Thus, in a given area, it is possible to measure the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs at a given point or to take a survey, for example, by performing parallel tacks and obtain the distribution of the size of the gas flow carried by the pop-up bubbles throughout the area.

The characteristics of the echo sounder 2 (E), which is part of the complex for estimating the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs (frequency and duration of the transmissions, signal frequency, power, radiation pattern characteristics), are determined in a standard way depending on the depth of the task , weather conditions, sizes of pop-up bubbles. For sufficiently large depths (more than 300 m), it is better to register at frequencies of 20-50 kHz, since a signal with higher frequencies is greatly attenuated. In shallow areas (depth less than 300 m) it is preferable to work with frequencies in the range of 50-250 kHz. The control and registration unit 1 (BUR) can be performed on the basis of a personal computer or using microprocessors. Coordination unit 3 (BS), digital registration system 4 (SCR), GPS / GLONASS receiver 5 (P) can be standard. As a cylinder with gas 7 (BG), a standard cylinder with methane can be used, and for shallow areas with any other gas, including inert gas. The gas supply system 8 (LNG) can be made on the basis of the BKO-50-4 reducer, a rotameter for measuring the gas flow of the LZM-4T series and a high pressure hose. The bottom platform 9 (DP) can be made, for example, of steel. When placed on the bottom, it should be located on the bottom surface and maintain stability. The nozzle 10 (C) is installed on the bottom platform (DP) so that when setting the bottom platform 9 (DP) to the bottom, it sinks into the upper sediment layer to a predetermined depth. The nozzle 10 (C) can be made in the form of a tube of steel with an inner diameter of 1-5 mm. The outer diameter of the nozzle 10 (C) determines its strength characteristics and is selected based on the characteristics of bottom sediments in a given area. The nozzle 11 (NAS), which is installed on the end of the nozzle 10 (C), can be made of steel. It must be securely fastened to the nozzle 10 (C), for example, by means of a threaded connection or welding. The end face of the nozzle 11 (US), facing the bottom sediments, can be made pointed to facilitate entry into them. The nozzle 11 (HAC) should be made so that the end face of the nozzle 10 (C) is not blocked by the elements of the nozzle 11 (HAC) and gas bubbles freely escape from it into the upper layer of bottom sediments. Technical characteristics of the used elements and blocks of the claimed device are determined by the task and measurement conditions.

Field tests of the device were carried out at a shallow testing ground in the Sea of Japan 12 m deep with a natural gas torch. A device for estimating the flow of gas carried by pop-up bubbles leaving the bottom of water bodies was installed on the ship. The complex used an echo sounder 2 (E) with a frequency of 200 kHz. The control and registration unit 1 (BUR) was made on the basis of a personal computer based on the Intel Core i5 processor running the Windows operating system. The coordination unit 3 (BS) and the digital registration system 4 (SCR) were standard. As a gas cylinder 7 (BG), a standard nitrogen cylinder was used. The gas supply system 8 (LNG) was made on the basis of the BKO-50-4 gearbox, a rotameter for measuring the gas flow rate of the LZM-4T series and a high-pressure hose withstanding pressure of 50 atm. The bottom platform 9 (DP) was made of steel in the form of a cylinder with a diameter of 30 cm and a thickness of 10 cm. On the bottom platform 9 (DP), a nozzle 10 (C) made of a steel tube with an inner diameter of 5 was installed at an angle of 30 ° to the vertical mm and an outer diameter of 10 mm. At the end of the nozzle 10 (C) was installed nozzle 11 (US) of steel. The nozzle 11 (US) was a cone with a base diameter of 20 mm, mounted on the end of the nozzle (C) by means of three steel rods with a diameter of 5 mm by welding.

Previously, a calibration was performed at the test site using a bubble generator 6 (GP). The frequency of sending acoustic signals of the echo sounder 2 (E) was 2 Hz, while the second and subsequent reflections of the acoustic signals from the bottom did not fall on the echogram from the water column. The duration of the packets was 0.3 ms. During the calibration, the vessel got into a drift away from the natural gas flare and the bottom platform 9 (DP) connected to the gas supply system 8 (LNG) and nozzle 10 (C) with a nozzle mounted at its end were lowered to the bottom of the reservoir directly under the echo sounder 2 (E) 11 (US). When the bottom platform 9 (DP) was installed on the bottom of the reservoir, the nozzle 10 (C) with the nozzle 11 (NAS) installed at its end was immersed in the upper sediment layer of the bottom to a depth of about 10 cm. At the command of the control and registration unit 1 (BUR), the system the gas supply 8 (LNG), to which the gas comes from the gas cylinder 7 (BG), provided a predetermined gas flow entering the bottom platform 9 (DP) and exiting from the nozzle 10 (C) into the upper sedimentary layer in the form of bubbles. At the same time, the acoustic signal of the echo sounder 2 (E) was emitted in the direction of the bottom. The same echo sounder 2 (E) received signals of backscattering sound from emerging from the bottom and pop-up bubbles. Sound backscattering signals through the matching unit 3 (BS) and the digital recording system 4 (SCR) were sent to the control and recording unit 1 (BUR), where they were processed and displayed as an echogram. Changing the magnitude of the gas flow exiting the nozzle 10 (C), we constructed a calibration dependence of the magnitude of the signal of backscattering sound on the magnitude of the gas flow for various depths N.

Then, the gas flow carried by the pop-up bubbles from the natural gas plume was evaluated. The measurements were carried out in the drift of the vessel above the natural gas torch. On command from the control and registration unit 1 (BUR), the acoustic signal of the echo sounder 2 (E) was emitted in the direction of the bottom. The same echo sounder 2 (E) received signals of backscattering sound from emerging from the bottom and pop-up bubbles. Sound backscatter signals through the matching unit 3 (BS) and the digital recording system 4 (SCR) were sent to the control and registration unit 1 (BUR), where they were processed and displayed as an echogram. Using the previously obtained calibration dependence of the sound backscattering signal from the bubbles, the gas flow was estimated for various depths N. At the same time, a signal from the GPS / GLONASS receiver 5 (P) was received at the control and recording unit 1 (BUR) to record the current coordinates. To verify the received data, a gas trap was lowered to the bottom of the vessel, made in the form of an inverted funnel with a closed neck, which completely closed the source of the natural gas torch. In this case, all bubbles emerging from the natural gas torch gradually collected in the neck of the trap. The gas flow was determined by the volume of the collected gas over a certain period of time after the trap was installed at the bottom. A comparison of the results showed that an objective estimate of the gas flow carried by the pop-up bubbles made using a trap with an acceptable accuracy of 12% coincided with the estimates obtained using a device for estimating the gas flow carried by the pop-up bubbles emerging from the bottom of water bodies. Estimates made using the prototype gave an error in estimating the gas flow carried by the pop-up bubbles at 25%.

Thus, the proposed device for evaluating the gas flow carried by the pop-up bubbles leaving the bottom of the reservoirs, it was possible to achieve the task, namely to improve the accuracy of the estimation of the gas flow carried by the pop-up bubbles coming out of the bottom of the reservoirs.

Claims (4)

A device for estimating the gas flow carried by pop-up bubbles leaving the bottom of reservoirs containing an echo sounder that is connected to a control and recording unit through a matching unit and a digital recording system that is connected to a GPS / GLONASS receiver and an echo sounder, a bubble generator consisting of series connected a gas cylinder and a gas supply system connected to a control and registration unit, a nozzle lowered into the reservoir, characterized in that a plume lowered to the bottom of the reservoir is connected to the gas supply system a form on the side surface of which, below, at an angle to the vertical, a nozzle is fixed, at the end of which a nozzle is fixed, the end of which, facing the bottom sediments, is made tapering. 2. The device according to p. 1, characterized in that the bottom platform is made in the form of a cylinder of steel. 3. The device according to p. 1, characterized in that the nozzle is made of a steel tube and mounted on the bottom platform at an angle of 30-45 ° to its vertical. 4. The device according to claim 1, characterized in that the nozzle is made of steel in the form of a cone.

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