RU78578U1 - GEOTHERMAL PROBE FOR MEASURING HEAT FLOW - Google Patents

Abstract

The utility model is aimed at improving the accuracy of measurement of thermophysical characteristics, increasing the depth of measurements in bottom sediments and a controlled change by a given amount of measurement horizons of thermophysical characteristics while simplifying the design of the probe. This result is achieved through the manufacture of a measuring unit in the form of a combined temperature sensor and heater and the installation of the obtained blocks in the groove of the supporting rod made of a material whose thermal conductivity is lower than the thermal conductivity of the bottom sediments, and the installation of a deepening device in the upper part of the rod. 5 cpf, 1 ill.

Description

The utility model relates to geophysical equipment and can be used to measure temperature profiles, distribution of thermal conductivity by depth and heat flux in a water layer, in bottom sediments and wells.

Thermophysical measurements form the basis of the heat flux method in the exploration of minerals such as oil, gas hydrates, radioactive elements, the deposits of which create abnormal (exceeding average values) heat fluxes directed from the depth of sedimentary rocks to the surface of the Earth or the surface of bottom sediments in the ocean.

Most of the currently known devices for measuring such thermophysical quantities as heat flux, temperature or thermal conductivity in the bottom sediments of the water area are freely falling probes equipped with powerful metal supporting rods, pipes or needles, to which thin metal tubes with primary transducers-thermistors or wire are attached resistance for measuring temperature and heating elements for measuring thermal conductivity. A massive load is attached to the upper base of the support rod, due to which the rod is introduced into the bottom sediments.

A device for measuring geothermal flow through the bottom of the water area, containing temperature sensors mounted on the probe tube, and at least one remotely controlled sensor heater. The probe tube is attached to an airtight container, inside of which there is a device for determining the temperature difference (AS USSR No. 408254).

A device is known for conducting thermophysical studies in the bottom silts of water areas (USSR AS No. 1520465). The device contains a sealed container with equipment and a movement mechanism consisting of an electric motor and drums brought out, a sample tube, needle probes with heat-sensitive elements and heaters, rigidly fixed with their point upwards by brackets of heat-insulating material on the sleeve. The sleeve, made in the form of a hollow cylinder, is mounted on the sample tube with the possibility of vertical movement and is connected to the drums by means of flexible connections. The container is connected to the cable, through which the device lowers to the bottom of the reservoir. Under the influence of its own weight or with the help of weighting agents

the sampler pipe goes deeper into the muddy soil, which at the same time fills it. Thermophysical characteristics are measured continuously over the entire height of immersion in the bottom sediments of the sampler pipe. The device allows you to record the temperature and thermal conductivity of precipitation, not disturbed by the introduction of a probe into them.

Known geothermal probe "GEOS-3M" (developed by Samara Polytechnic University, manufacturer - SPC "PALS", Samara;

http://geotherm.ginras.ru/06_03_aqua_rus.htm:

http://geotherm.ginras.ru/Pdf/image06_03_G1.pdf). The GEOS-3M system is designed to automatically measure the temperature of bottom sediments; temperature gradient at measuring horizons; thermal conductivity of precipitation at the same horizons; hydrostatic pressure (depth); water temperature; the angle of penetration of the probe into the precipitation (angle of deviation from the vertical) and determination, based on the data obtained, of the Earth's deep heat flux through the bottom of the water area. In addition, the probe allows vertical temperature sensing of the water column to a depth determined by the length of the cable cable. The measurement results are recorded in the memory of the on-board computer and displayed on the display screen.

The device is a geothermal probe immersed in a measured medium, and an airborne unit interconnected by a cable.

The probe is a sealed container in which an electronic measuring unit with a thermistor for measuring the temperature of the bottom layer of water, a pressure sensor and inclinometer is located. The lower part of the container is attached to a bearing steel rod, along which two thin metal tubes are fixed, forming measuring “braids”. One of them contains thermistors for measuring the temperature profile of precipitation, and the other contains heating elements used as heat sources for measuring thermal conductivity, and thermistors used to control the temperature of heating elements.

The use of two different measuring “braids” for measuring the temperature gradient and determining thermal conductivity, each of which is equipped with its own set of temperature sensors, reduces the accuracy of heat flow measurements, since the errors of temperature measurements in determining the temperature gradient and determining thermal conductivity in this case add up

Closest to the claimed utility model is a modification of the geothermal probe GEOS-3M described above. Circuit diagram

a modified version of the probe is described in the annotated report “Research on the geothermal specifics of structural and tectonic elements of the Russian Arctic” for 2007 of the State educational institution of higher professional education of the Russian University of Friendship of Peoples, published on the website www.rad.pfu.edu.ru/info/sc/otc_templan .doc.

The probe also consists of a supporting rod and a sealed container in which an electronic measuring unit with a thermistor for measuring the temperature of the bottom layer of water, a pressure sensor and inclinometer is located. The lower part of the container is attached to a bearing steel rod, along which two thin metal tubes are fixed, forming measuring “braids”. But, the measuring “braids” of the prototype probe are identical in design and interchangeable. Each of the “braids” contains a unit for measuring thermophysical quantities, consisting of both temperature sensors and a heater, which is a linear heater uniformly distributed along the length of the “braid”.

Through the cable, the probe is connected to the on-board unit, designed to work with a personal computer via a standard USB port. The on-board unit provides electrical power to the probe and the transmission of measurement information received from the probe to a personal computer. In a personal computer, all directly or indirectly measured parameters are calculated and presented in the form of tables and graphs.

Miniature thermistors are used as temperature sensors. In the "braid" for measuring thermal conductivity, at the command of the operator, the heating current is turned on.

The probe container contains sensors for hydrostatic pressure, water temperature and the angle of penetration of the probe, as well as an electronic measuring unit, including a micro-converter that converts the sensor signals to digital codes, and a microprocessor that provides the transmission of all digital data via cable to the on-board unit.

The primary pressure transducer is a pressure transducer.

The sensor angle of penetration of the probe into the bottom sediments is a miniature accelerometer.

Note that for all the above-known known probes, including the prototype, the use of a metal supporting rod for penetrating deep into the bottom sediments leads to a distortion of the data due to the high

thermal conductivity of the metal, which reduces the likelihood of detecting temperature anomalies in the upper sediment layer, and the random depth of immersion of the sensors in precipitation with an unknown density that varies with depth during free fall makes it almost impossible to use probes to estimate the spatial scales of local microscale temperature anomalies caused, for example, by tidal variations in the temperature of the upper layer of bottom sediments or spatial displacements of currents, which lead to distortion of the results atov deep heat flow measurements. The temperature measurement procedure is greatly lengthened, since it requires a long process of temperature control of the sensors, first due to mutual heating due to friction of the penetrating parts of the probe and the surrounding sediment, and then due to the redistribution of temperature in the precipitation caused by higher thermal conductivity of the metal parts of the probe.

In addition, the fundamental limitation of the ability to measure thermophysical quantities, including heat flux, the prototype probe is the structural complexity of the device, the decrease in measurement accuracy due to the use of the "conductivity" measurement of thermal conductivity as a heater - a linear heater uniformly distributed along the length braids ”, which, in combination with a long metal tube into which the unit for measuring thermophysical quantities in the form of a linear heater and thermistors is placed, leads to the effect of remote x heater portions on the temperature measured by each thermistor and this greatly reduces the possibility of precipitation separation horizontal layers with different thermal conductivity, which is especially important for the top layer of the bottom sediments, the thermal conductivity which greatly varies with depth due to reduce humidity.

The objective of the utility model is to increase the accuracy of measurement of thermophysical characteristics, increase the depth of measurements in bottom sediments and a controlled change by a given amount of measurement horizons of thermophysical characteristics while simplifying the design of the probe.

The problem is solved by a geothermal probe for measuring thermophysical quantities, consisting of a supporting rod, in the upper part of which there is a sealed container containing an electronic measuring unit and a burial device, while the supporting rod is made of a material whose thermal conductivity is lower than the thermal conductivity of the measured deposits, and is equipped with a gutter with installed in it with at least one measuring unit

thermophysical quantities containing a temperature sensor combined with a heating element.

To expand the functionality of the probe and improve the accuracy of measurements, the probe can be equipped with hydrostatic pressure and / or angle sensors, which are installed in the container.

The probe can be equipped with a camera to control the place of its introduction.

The electronic measuring unit of the probe is designed to convert sensor signals to digital codes, and can be performed, for example, on the basis of a microcontroller with an ADC. The resulting digital codes can then be transmitted via cable to the on-board recording unit in real time or stored in the memory of the electronic measuring unit, provided it is equipped with an autonomous system for collecting and storing information, for example, in the form of a controller with flash memory and / or other devices for collecting of information

The supporting rod of the probe can be made in the form of a needle.

The deepening device may be located in a container with an electronic measuring unit or located in a separate container in series or parallel to the first.

In FIG. a diagram of the inventive probe is presented, where 1 is the supporting rod, 2 are the blocks of measurement of thermophysical quantities, including a temperature sensor and a heating element combined with it, 3 is an electronic measuring unit, 4 is a burial device, 5 is a recording system, 6 is a cable - cable, 7 - power supply unit of the deepening device and the heating element.

Blocks (2) measuring thermophysical quantities, contain a temperature sensor and a heating element combined with it. Typically, the temperature sensor is a cylindrical thermistor equipped with an insulating sheath, and the heating element can be made, for example, in the form of a wire of high resistance material wound around the insulating sheath of a thermistor. The resulting block (2) is mounted in a trench (not shown in FIG.) Milled along the guide of the rod (1) along its entire length.

The combination of the temperature sensor and the heating element in one unit (2) of measuring thermophysical quantities allows to increase the accuracy of measuring the heat flux by reducing errors in measuring the temperature gradient in precipitation and determining thermal conductivity, since in this case the temperature of each

the horizon on which the block (2) is located is measured by the same thermistor.

The number of blocks (2) located in the groove of the supporting rod (1) can be arbitrary and is determined by the research task and the geometric dimensions of the sensors. Blocks (2) are connected to the electronic measuring unit (3) by wires laid in the groove of the supporting rod (1).

For the manufacture of a supporting rod, a material is used whose thermal conductivity is lower than the thermal conductivity of bottom sediments, that is, as a rule, not higher than 0.92 W / m ² for marine sediments (Handbook of Physical Constants of Rocks. Edited by S. Clark Jr. M. M .: Mir , 1969, 544 p.). Such thermal conductivity is, for example, wood, plastic and other similar materials. The use of these materials eliminates the redistribution (equalization) of temperature between the layers of precipitation and thereby significantly reduce the measurement errors caused by the influence of the measuring device on the measurement results. The use of materials with a lower thermal conductivity than the thermal conductivity of the precipitation for the manufacture of the supporting rod also allows the installation of temperature sensors directly on the supporting rod, which greatly simplifies the mechanical design of the device and increases its reliability.

The device (4) for deepening the probe can be performed, for example, in the form of an electromechanical or pneumatic vibrator mounted in the upper part of the supporting rod (1). This device (4) provides deepening to a predetermined depth in the precipitation of the bearing rod (1) by a command transmitted to it either via a cable cable (6) or through an acoustic channel. The power of the device (4) can be either autonomous or via a power cable.

The deepening device (4) allows you to change the temperature measurement horizons by a predetermined value, which, while using a supporting rod (1) made of a material with the corresponding thermal conductivity and the design of the unit (2) for measuring thermophysical quantities, consisting of a temperature sensor combined with a heating element, allows to detect small-scale temperature anomalies and heterogeneities of thermal conductivity in the upper layer of bottom sediments, and to take into account their influence on the results of measurements of deep thermal flux, which leads to a decrease in error detection of anomalous heat flow caused by mineral deposits, such as hydrocarbons.

The placement of the electronic measuring unit (3) and the device (4) for deepening into containers of a streamlined, vertically elongated along the axis of the probe shape makes it easier to immerse the probe in precipitations to a depth exceeding the probe’s own length up to a depth at which the power of the deepening device is insufficient for further advance inward, increase the hydrodynamic characteristics of the probe, and therefore reduce the energy intensity of immersion and increase the depth of research.

A geothermal probe works as follows.

In the case of using a geothermal probe to measure heat flux through the bottom of the water area, the probe is lowered on a cable (6) first into a layer of water with a constant temperature in depth, previously measured by a high-precision thermometer, and in this layer is maintained for the time required to reach a constant level of readings (signals) of all temperature sensors of the blocks (2). The signal level of each temperature sensor corresponding to the temperature of the water in the layer is recorded in the measuring unit (3) and the registration system (5), and thus the probe is calibrated. Then the probe is lowered until the bottom touches the tip of the supporting rod (1) and the immersion depth until the bottom touches is taken as zero depth in the sediments. Further deepening of the bearing rod (1) with blocks (2) into precipitation is carried out first under its own weight (until the cable cable is tensioned (6)), and then by turning on the deepening device (4) for the time necessary to move deeper into the precipitation preset distance. The device (4) for deepening is switched on from the side of the vessel by applying voltage to it from the power unit (8). After the next deepening, the probe is fixed at the reached depth for the time required to reach a constant level of signals from all temperature sensors of the unit (2). Then, the heating elements of the block (2) are turned on, which heat the metal housings of the thermistors to a temperature of about 3-4 ° C higher than the temperature of the medium, measured in the previous step. The temperature to which the body of each thermistor is heated is measured by the thermistor itself with an accuracy of ± 0.01 ° C. After turning off the heating elements, the thermistor bodies cool down. The cooling rate depends on the thermal conductivity of the soil at the location of the thermistor. Thus, at different cooling rates of thermistors located at different depths, it is possible to obtain a thermal conductivity profile in the precipitation, which, with the inhomogeneity (layered structure) of the precipitation, can significantly increase the accuracy of measuring the heat flux.

The temperature constants of the thermistors installed in the supporting rod are adjusted with respect to the temperature constants of the free thermistors by calibration in an environment with known thermal conductivity, such as water.

After completing the measurements of the temperature and thermal conductivity gradients at the studied levels, at which the temperature-thermal conductivity measuring units (2) are installed, the deepening device (4) is turned on again and the probe is deepened to the next horizon, at which the measurement cycle is repeated. The optimal depth of the next horizon is the depth at which the position of the upper block (2) of the probe coincides with the position of the lower block (2) on the previous horizon.

The specific hardware implementation of the electronic measuring unit (3), the burial device (4), temperature sensors and heaters is standard, well-known to the average specialist and depends on the task of measurement, the required accuracy, resolution, speed.

Thus, the proposed constructive solution of the inventive geothermal probe for measuring thermophysical characteristics, such as temperature, thermal conductivity and heat flux, allows measurements to a depth determined mainly by the power of the burial device. The measurement accuracy is determined by the characteristics of the temperature sensors used and the accuracy of their calibration before diving. In addition, the probe makes it possible to detect and evaluate spatial small-scale temperature anomalies that interfere with measurements of the geothermal heat flux, and thus reduce the detection errors of abnormal heat fluxes caused by mineral deposits, such as hydrocarbons.

Claims (6)

1. A geothermal probe for measuring thermophysical quantities, including a supporting rod, a unit for measuring thermophysical quantities, consisting of a temperature sensor and a heating element, as well as a sealed container located in the upper part of the supporting rod and containing an electronic measuring unit, characterized in that the unit for measuring thermophysical the values are made in the form of a temperature sensor and a heating element conjugated to each other, the supporting rod is made of a material whose thermal conductivity is lower thermal conductivity of the measured deposits, is equipped with a longitudinal trough in which at least one unit for measuring thermophysical quantities is installed, while the probe further comprises a deepening device installed in the upper part of the supporting rod. 2. The geothermal probe according to claim 1, characterized in that the supporting rod has the shape of a needle. 3. The geothermal probe according to claim 1, characterized in that the sealed container contains sensors for hydrostatic pressure and / or the angle of penetration of the probe. 4. The geothermal probe according to claim 1, characterized in that it is equipped with a television camera. 5. The geothermal probe according to claim 1, characterized in that the electronic measuring unit is equipped with an autonomous information collection system. 6. The geothermal probe according to claim 1, characterized in that the container has a streamlined shape, elongated vertically along the axis of the bearing rod.