RU2698552C1 - Method of estimating the flow of methane into the atmosphere, which is carried by floating bubbles emerging from the upper layer of sedimentary rocks at the bottom of the water reservoir, and a device for its implementation - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: invention relates to means of estimating flow of methane into atmosphere, which is carried by floating bubbles emerging from upper layer of sedimentary rocks at the bottom of water reservoir. Essence: sample of sedimentary rock is taken and placed on bottom of closed vertical reservoir. Reservoir is filled over the sample of the sedimentary rock with water from the analysed water body to the height of not less than ten meters. Preset flow of methane from nozzle inserted through bottom into reservoir is passed through sample of sedimentary rock. Water bubbles coming out of water are separated from water and drops splashes. Flow of gas leaving water is collected and measured. Images of the emerging bubbles near the water surface are recorded. Recording of images of emerging bubbles near water surface is synchronized with measurements of gas flow and composition. Device for method implementation contains gas cylinder (1) with methane equipped with regulator (2) connected to controller (3) of methane flow. Controller (3) of methane flow through valve (4) is connected to nozzle (5) passing through the bottom inside closed vertical tank (6). Vertical tank (6) is made with height of more than ten meters. Lower part of reservoir (6) is intended for arrangement of sample (7) of sedimentary rock, on top of which water (8) is filled. Inside the upper part of tank (6) there is a conical funnel shaped as inverted funnel (9), the tube of which is brought out from above. Outside tank (6) there is a gas flow meter (11) and a digital video camera (13), to accommodate the lens in the side wall of tank (6) below funnel (9) there is a window. Funnel tube (9) through separator (10) is connected to gas flow meter (11), which is connected to chromatograph (12), wherein control and registration unit (14) is connected to methane flow controller (3), to meter (11) flow of gas, to chromatograph (12) and to digital video camera (13).EFFECT: high accuracy of estimating the flow of methane into the atmosphere, which is carried by bubbles emerging in the water and emerging from the upper layer of sedimentary rocks.2 cl, 3 dwg

Description

The invention relates to geophysics, and in particular, to means for estimating the gas flow and can be used to estimate the methane flow carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of the reservoir into the atmosphere, for example, to simulate the flow of greenhouse methane gas from the ocean to the atmosphere .

A known method for evaluating the flow of methane carried by bubbles emerging in water [RU 150012 U1, IPC G01S 15/02 (2006.01), publ. 01/27/2015], which includes a preliminary calibration of a marine echo sounder, consisting in the fact that a predetermined stream of gas bubbles is released from a nozzle lowered to the bottom of the reservoir, and the level of the backscattered sound signal from the pop-up bubbles is determined using the echo sounder. By changing the gas flow, a calibration curve is obtained that relates the level of the echo sounder signal to the gas flow at the bottom of the reservoir. Using a calibration curve, the methane flow at the bottom in vivo is determined from the echo sounder signal level.

To implement this method, a device for evaluating the flow of methane carried by bubbles emerging in water [RU 150012 U1, IPC G01S 15/02 (2006.01), publ. 01/27/2015], containing an echo sounder associated with the matching unit, to which a digital registration system, a control and registration unit that is connected to GPS / GLONASS, a 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.

Using the known method and device, knowing the methane flow at the bottom, it is impossible to determine the methane flow coming from pop-up bubbles into the atmosphere, which is very important for modeling the flow of greenhouse methane gas from the ocean to the atmosphere. This is due to the fact that, when a bubble emerges, part of the methane due to diffusion passes from the bubble into water, and nitrogen and oxygen enter the bubble from the water. The methane flow to the atmosphere is estimated from the methane flow at the bottom using programs that calculate the methane content of a pop-up bubble, for example, a program for calculating the gas content of a pop-up bubble [SiBu-GUI (Greinert J., McGinnis DF Single bubble dissolution model: the graphical user interface SiBu-GUI // Environ Model Software. 2009. Vol. 24. - P. 1012-1013]. An experimental verification of this possibility with artificially created bubbles, carried out on a shallow shelf in the Laptev Sea from the surface of fast ice, showed an acceptable coincidence of experimentally determinedof concentrations in methane bubbles near the water surface with calculated values [Chernykh, D., Salomatin, A., Yusupov, V., et al. Quantitative acoustic estimation of methane flows from landfast ice on shallow East Siberian shelf // Vestnik FEB RAS, 2013 No. 6. - P. 128-133]. However, in the transition from artificially created bubbles to natural bubbles, a significant error arises in estimating the flow of methane into the atmosphere. This is due to the fact that the flow of methane from the pop-up bubble into the water depends on the characteristics of the upper sedimentary layer of the bottom, from which the bubbles exit into the reservoir. Bubbles passing through the upper sedimentary layer of reservoirs into water transfer 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. The presence of such substances on the surface of the bubble significantly affects the ascent rate and the flow of methane from the bubbles into the water.

A known method and device for its implementation, selected as a prototype, using which determine the flow of methane carried by bubbles near the water / air boundary in the case when the gas enters the water through a layer of precipitation [Yuan Q., Valsaraj K. T. , Reible DD, Willson C.S. A laboratory study of sediment and contaminant release during gas ebullition // Journal of the Air & Waste Management Association. 2007. V. 57. N. 9. - P. 1103-1111]. The method consists in the fact that a predetermined stream of gas bubbles is released from a nozzle into the bottom of a vertical tank with a height of the order of one meter through a sample of sedimentary rock at its bottom, the flow of methane leaving the water filling the rest of the tank is measured, and images of pop-up bubbles are recorded by which judge the size of pop-up bubbles near the surface of the water.

A device for evaluating the flow of methane transported by pop-up bubbles leaving the sedimentary rock layer at the bottom of the reservoir contains a methane gas cylinder equipped with a regulator that is connected to the methane flow controller, and through a valve, with a nozzle passed through the bottom into the vertical reservoir, height 74 see. The lower part of the reservoir is filled with a sample of sedimentary rock, above which there is water. Inside the tank, in its upper part, a conical bell is installed in the form of an inverted funnel, the tube of which is brought out and connected to a gas flow meter. Below the funnel, in the side wall of the tank, a window is made for placing the lens of a digital video camera mounted on the outside.

The known device operates as follows. Previously, the lower part of the vertical reservoir is filled with the necessary sample of sedimentary rock. Then, on top of the sedimentary rock sample, the vertical reservoir is filled with water, which may also be from the studied reservoir. After that, the regulator on the gas cylinder with methane is opened, and the methane flow is controlled by the methane flow controller. Methane under pressure enters through the valve and nozzle into the bottom of the vertical tank. After passing through the layer of sedimentary rock images, methane bubbles enter the water and float to the surface. The gas escaping to the surface of the water is collected by a gas collection system and its flow is determined using a flow meter. Using a digital video camera, images of gas bubbles near the surface of the water are obtained.

Thus, the flow of gas into the atmosphere, delivered by pop-up bubbles of methane, passed before entering the water through sedimentary rock of different composition, is estimated. However, the accuracy of determining the flow of methane entering the atmosphere is insufficient. This is due to the fact that when the bubble comes up, nitrogen and oxygen enter it from the water. Therefore, the estimate of methane flow into the atmosphere is overestimated. The measurement accuracy is also reduced due to the manual control of all processes and measurements, which does not allow to accurately synchronize the beginning of the registration of the gas flow with the first appearance of pop-up bubbles in the upper part of the tank.

The proposed inventions can improve the accuracy of estimating the flow of methane into the atmosphere carried by bubbles floating up in the water leaving the upper layer of sedimentary rocks.

A method for evaluating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of the reservoir, as in the prototype, includes taking a sample of sedimentary rock and placing it on the bottom of a closed vertical reservoir, filling the reservoir on top of the sedimentary rock sample with water from the investigated reservoir passing a predetermined methane stream through a sedimentary rock sample from a nozzle inserted through the bottom into the reservoir, collecting and measuring a gas stream leaving the water, recording images in floating bubbles near the surface of the water.

According to the invention, a vertical reservoir above the sedimentary rock sample is filled with water to a height of not less than ten meters, gas bubbles leaving the water are separated from water splashes and drops, and the registration of images of pop-up bubbles near the water surface is synchronized with measurements of the gas flow and its composition.

A device for evaluating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of the reservoir, as in the prototype, contains a gas cylinder with methane equipped with a regulator, which is connected to a methane flow controller, which is connected through a valve to the nozzle, passed through the bottom into a closed vertical tank, the lower part of which is designed to accommodate a sedimentary rock sample, on top of which water is poured, conically installed inside the upper part of the tank a bell in the form of an inverted funnel, the tube of which is pulled outward from above, a gas flow meter and a digital video camera are located outside the tank, a window is made to place the lens in the side wall of the tank below the funnel.

Unlike the prototype, the vertical tank is made more than ten meters high. The funnel tube through the separator is connected to a gas flow meter, which is connected to the chromatograph. The control and registration unit is connected to a methane flow controller, to a gas flow meter, to a chromatograph, and to a digital video camera.

Improving the accuracy of estimating the flow of methane into the atmosphere carried by bubbles floating up in the water leaving the upper layer of sedimentary rocks at the bottom of the reservoir occurs by measuring the composition of the gas leaving the surface of the water, significantly increasing the height of the closed vertical tank, and also by automating control of all processes and measurements. Measurement of the composition of the gas released into the atmosphere allows only methane to be taken into account and to exclude other gases, for example, nitrogen and oxygen, which enter the bubble from the water when it emerges. Increasing the height of the closed vertical tank (> 10 m) allows to reduce the error in estimating the flow of methane into the atmosphere at greater depths than the height of the vertical tank. This is due to the fact that the maximum change in the bubble size upon ascent due to a decrease in pressure occurs precisely in the upper ten-meter layer. In this layer, the pressure on the bubble decreases by half, because of which its volume doubles. In FIG. 1 as an example, the calculated dependence of the surface area of a methane pop-up bubble on the depth of its location in water is presented. The calculation was performed for a bubble with a radius at the water surface of 3 mm. It is seen that the maximum change in the area (~ 30%) through which the exchange of gases between the bubble and the surrounding water takes place occurs in the upper ten-meter layer. Deeper than 10 m down to a depth of 80 m, an additional change in surface area lies in the range of 14%.

As a result of control automation, the registration of the magnitude of the gas flow and its composition is started when the pop-up bubbles are first registered with a digital video camera, which reduces the measurement error.

In FIG. Figure 1 shows the dependence of the surface area of a methane bubble emerging from its depth in water.

In FIG. 2 is a block diagram of a device for estimating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of a reservoir.

In FIG. Figure 3 presents the results of measuring the concentration of methane obtained using a chromatograph: a) a histogram, where rectangle K shows the methane content in the calibration sample and rectangle Izm in the gas sample passing through the water column; b) - chromatograms of gas samples with a methane peak, where the dotted line shows the result obtained for the calibration sample, and the solid line for the gas sample passed through the water column.

A device for evaluating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of the reservoir contains a gas cylinder 1 (BG) equipped with a regulator 2 (PE), to which a methane flow controller 3 (KOH) is connected, connected through the valve 4 (BE) with a nozzle 5, passed through the bottom into the closed vertical tank 6, a height of more than ten meters. A sample of sedimentary rock 7 is placed in the lower part of the tank 6, over which water 8 from the studied reservoir is poured. The remaining part of the tank 6 is filled with water 8. Inside the tank 6, in its upper part, there is a conical bell in the form of an inverted funnel 9, the tube of which is brought outward from above and connected through a separator 10 (CEP) with a gas flow meter 11 (PI), which is connected to a chromatograph 12 (XP). Below the funnel 9, in the side wall of the tank 6, a window is made for accommodating the lens of the digital video camera 13 (B), mounted on the outside. The control and registration unit 14 (BUR) is connected to a gas flow meter 11 (PI), a chromatograph 12 (XP), a digital video camera 13 (B), and a methane flow controller 3 (KOH).

The control and registration unit 14 (BUR) is made on the basis of a personal computer, for example, on the basis of an Intel Core i5 processor running the Windows operating system. As a cylinder with gas 1 (BG) with regulator 2 (PE), a standard methane cylinder equipped with a regulator is used. The controller 3 (KOH) gas flow can be performed on the basis of the gearbox BKO-50-4. Valve 4 (BE) may be standard. The nozzle 5 can be made of a steel tube with an inner diameter of 5 mm and an outer diameter of 10 mm. As a gas flow meter 11 (IP), the LGR DTL-100 greenhouse gas analyzer can be used. As chromatograph 12 (XP), an SRI 8610C gas chromatograph can be used. The closed vertical tank 6 is made of a plastic pipe with a diameter of 0.12 m and a height of 25 m. The funnel for collecting gas 9 is made of stainless steel. As a separator 10 (CEP) used a standard separator Flamcovent NW, Flamco Netherlands.

Previously, the lower part of the vertical reservoir 6 to a height of 20 cm was filled with a sample from the upper layer of sedimentary rocks taken at a landfill in the Laptev Sea. Then, on top of the layer of sample 7, the vertical tank 6 to a height of 20 m was filled with sea water. After that, the regulator 2 (PE) on the gas cylinder 1 (BG) and valve 4 (BE) were opened. The signal from the control and registration unit 14 (BUR) turned on a video camera 13 (V), a gas flow meter 11 (PI), a chromatograph 12 (XP), and gave controller 3 (KOH) a methane flow in terms of atmospheric pressure of 5 l / min. A predetermined methane flow under pressure entered through valve 4 (BE) and nozzle 5 into the lower part of a closed vertical reservoir 6. Passing through a layer of sedimentary rock sample 7, methane entered water 8 and floated in the form of bubbles to its surface. The gas escaping to the surface of the water was collected by a funnel 9, using a separator 10 (CEP), water splashes and drops were removed from the gas samples. Using a digital video camera 13 (B), images of gas bubbles were obtained near the surface of the water, the gas flow was measured using a gas flow meter 11 (IP), and the gas composition was determined using a chromatograph 12 (XP). Moreover, following the pop-up bubbles by their appearance, we determined the period of gas registration by the gas flow meter 11 (IP) and chromatograph 12 (XP). In a specific case, the gas registration period was 23.7 ± 0.3 s.

Using a digital video camera 13 (B), 4.0 ± 0.1 mm bubbles popping up at a speed of ~ 21 cm / s were detected.

Information on the amount of methane delivered to the atmosphere, obtained using a gas flow meter 11 (PI) and chromatograph 12 (XP), allowed us to establish that the flow of methane to the atmosphere was 3.6 ± 0.2 l / min, and the percentage of methane amounted to 73.6% - a) in FIG. 3. As can be seen from b) in FIG. 3, in addition to methane, oxygen and nitrogen are present in the collected gas. Thus, when bubbles bubble up from a depth of 20 m, about 26% of methane from its initial value is given into the water.

The methane flux into the atmosphere measured by the prototype device was 4.5 ± 0.2 l / min, which is 25% higher than that obtained using the proposed device.

In addition, using the program for processing the recorded video sequence with pop-up bubbles, the control and recording unit 14 (BUR) allows you to determine the distribution of pop-up bubbles by size and speed of their ascent, which is necessary for the further construction of models describing the flow of methane through water into the atmosphere, and for calculations of methane flow during acoustic remote measurements from the ship.

Claims (2)

1. A method for evaluating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rock at the bottom of a reservoir, including sampling a sedimentary rock and placing it on the bottom of a closed vertical reservoir, filling the reservoir on top of a sedimentary rock sample with water from the test reservoir, passing through sedimentary rock sample of a given methane stream from a nozzle inserted through the bottom into the reservoir, collecting and measuring the gas flow coming out of the water, registering images of a pop-up bubble ov near the surface of the water, characterized in that the vertical reservoir above the sedimentary rock sample is filled with water to a height of not less than ten meters, gas bubbles leaving the water are separated from water splashes and drops, synchronization of the registration of images of pop-up bubbles near the water surface with measurements of the gas flow and its composition. 2. A device for evaluating the flow of methane into the atmosphere carried by pop-up bubbles leaving the upper layer of sedimentary rocks at the bottom of the reservoir, containing a gas cylinder with methane, equipped with a regulator that is connected to a methane flow controller, which is connected through a valve to a nozzle passed through the bottom inside a closed vertical tank, the lower part of which is designed to accommodate a sedimentary rock sample, on top of which water is poured, a conical bell in the form of an inverted funnel, the tube of which is pulled outward from above, a gas flow meter and a digital video camera are located outside the tank, for placing the lens of which a window is made in the side wall of the tank below the funnel, characterized in that the vertical tank is made more than ten meters high, the funnel tube is connected through a separator to a gas flow meter that is connected to the chromatograph, while the control and recording unit is connected to a methane flow controller, to a gas flow meter, to the chromatograph, and to the numbers new camcorder.

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