A DEVICE FOR DETERMINING THERMOPHYSICAL CHARACTERISTICS OF SOLIDS IN UNCASED DRILL WELLS

Abstract

The utility model relates to the field of geophysical well logging, namely, the determination of the thermophysical properties of rocks in uncased boreholes, and can be used in the practice of geophysical work related to the study of well cross-sections and hydrocarbon production, as well as for mathematical modeling and optimization of hydrocarbon production processes. The technical result of the utility model is the creation of a device for determining the thermophysical properties of solids in uncased boreholes, ensuring increased operational reliability. The device comprises a heat insulator, a heater, a heater temperature sensor, a clamping mechanism mechanically contacting the heat insulator, an electronic unit in which the clamping mechanism is designed as a centralizer with four clamping levers, each of which contains a measuring element consisting of a heat insulator made of heat-insulating material,in which three heat receivers are installed with temperature sensors built into them, oriented along the generatrix of the inner surface of the well, and the central heat receiver, in addition to the temperature sensor, contains a heater made in the form of a coil made of a material with high thermal conductivity with a wound high-resistance insulated wire, which is electrically isolated from the temperature sensor, while the outer surface of the heat insulator with the temperature sensors and heater recessed in it is capable of taking the shape of the inner surface of the well wall under the action of the spring force, and the electronic unit is electrically connected to the heater and the temperature sensors of the measuring elements. 2 fig.,

Description

[0001] The utility model relates to the field of geophysical well surveys, namely the determination of thermophysical characteristics (thermal conductivity, thermal diffusivity, heat capacity) of rocks in uncased boreholes and can be used in the practice of geophysical work related to the study of well sections and hydrocarbon production, as well as for mathematical modeling and optimization of hydrocarbon production processes.

[0002] A device for determining the thermophysical properties of rocks in a borehole is known, comprising a cylindrical body made of a material with high thermal conductivity (copper), on the ends of which solid cylinders made of a material with low thermal conductivity (ebonite) are mounted with a spring centralizer fixed to them. A linear heater made of insulated nichrome wire filled with Wood's alloy is placed in the axial hole of the body, and a temperature sensor is located on the surface of the body. The spring centralizer centers the device along the borehole axis and ensures a uniform gap between the outer surface of the body and the borehole wall (SU 732515, E21B 47 / 06, published 05.05.1980).

[0003] Thermophysical properties of rocks in the heating zone are determined by the rate of change of the sensor temperature at a constant heating power. The technical result achieved is increased reliability of the obtained data by eliminating convective heat transfer into the borehole.

[0004] A disadvantage of this device is the presence of an annular gap between the outer surface of the housing and the borehole wall, through which the wellbore fluid flows. Variability in the flow rate of the wellbore fluid and its composition (water, oil, gas) during the survey affect the rate of change of the sensor's temperature at a constant heating power, which reduces the reliability of the obtained data on the thermal properties of the rock.

[0005] Another drawback of the device is that its design does not provide direct physical and thermal contact between the heater and temperature sensor and the rock, but only through an annular gap filled with borehole fluid. This circumstance also reduces the reliability of the obtained data on the thermal properties of the rock.

[0006] Furthermore, the low thermal conductivity of the borehole fluid in the annular gap reduces the rate of heat transfer and increases the time it takes to conduct the test. Convective heat transfer into the borehole cannot be ruled out, given the stated ratio of the linear heater to the cylinder length.

[0007] A borehole probe is known for measuring the thermal properties of rocks, comprising a tubular body made of a material with high thermal conductivity (bronze, duralumin), on the inner surface of which an axisymmetric resistive heater of constant specific thermal power is installed with thermal contact, thermally insulated with hard rubber from the cavity of the body as part of a single channel open into the borehole, completely blocked during measurements, a thick-walled cylinder made of a material of reference thermal conductivity (stainless steel 12X18H10T) is seated on the outer surface of the body, the length of which coincides with the length of the measuring heater and on which pairs of temperature sensors are installed along its internal and external generators at a selected pitch.The probe also contains spring centralizers that center the probe along the borehole axis and create a uniform annular gap between the outer surface of the thick-walled cylinder and the borehole wall, controlled inflatable packers, a container filled with a high-thermal-conductivity composition (drilling mud with additives of highly thermally conductive dispersed metals or minerals), a means for pumping the composition through channels into the annular gap, an electronic unit in the internal sealed cavity of the probe, and a surface processing complex (RU 2406081, G01N25 / 18, published 10.05.2009).

[0008] The thermal properties of rocks are calculated and output by a surface processing unit operating according to a pre-programmed measurement program. It maintains and regulates the resistive heater, processes and stores incoming data from temperature sensors, and generates control commands during processing stages. The achieved positive result is highly accurate thermal properties of rocks measured in both autonomous and automatic modes.

[0009] The disadvantage of the probe is the relatively complex technical execution and labor-intensive in terms of time and number of operations process of excluding convective heat transfer from the measurement interval, which consists in the fact that in the study area, an annular gap is initially established between the outer surface of the thick-walled cylinder and the wellbore wall using centralizers, then a lower controlled inflatable packer is installed, the means for pumping the calculated volume of a high thermal conductivity composition from a container is turned on, the annular gap is filled with a high thermal conductivity composition, thereby displacing the well fluid that filled it, after which the annular gap is closed by installing an upper controlled inflatable packer, and the cavity of the tubular body, which is part of a single channel open into the wellbore for the passage of well fluid when the probe moves along the wellbore, is completely closed by a valve for the duration of the measurements.

[0010] Another disadvantage of the probe is that its design does not provide direct physical and thermal contact between the heater and temperature sensor and the formation. It does so only through an annular gap filled with a highly thermally conductive compound during measurements. While this circumstance eliminates convective heat loss in the packer installation interval, the introduction of an intermediate link in the form of a highly thermally conductive compound into the heat exchange chain between the outer surface of the thick-walled cylinder and the borehole wall complicates the probe's design and reduces its reliability.

[0011] The closest in technical essence to the claimed utility model is a device for determining the thermophysical characteristics of solids in natural occurrence conditions, containing

[0012] a heater and a heater temperature sensor, made in the form of a single thin-film flexible membrane in the form of a spiral made of electrically conductive material (brass foil), which is in mechanical contact with the heat insulator;

[0013] - a heat insulator, which, depending on the design, can be made of a hard or elastic material (sponge rubber), in which two temperature sensors are located;

[0014] - a clamping device that mechanically contacts the heat insulator and the body of the device;

[0015] - an electronic unit in the internal sealed cavity of the device body, to which a heater, a heater temperature sensor and two temperature sensors located in the heat insulator are connected.

[0016] In a particular case, the heat insulator can be made of an elastic material that, under the influence of a pressing force, is capable of taking the shape of the surface of a solid body on which thermal properties are measured.

[0017] In a particular case, the heat insulator and the clamping element may have shapes, sizes and thermal properties that exclude the occurrence of thermal convection of the environment (RU 2403561, G01N25 / 00, published 10.11.2010).

[0018] Thermophysical characteristics of a solid (thermal conductivity and thermal diffusivity) are determined by measuring the temperature of a heater pressed against the solid's surface, which also functions as a temperature sensor. This temperature measurement is used both in the time interval from the onset of heating of the solid to the onset of thermal convection in the surrounding environment, and after the solid ceases heating. The device is used to measure the thermal properties of inhomogeneous solids, as well as solids with cylindrical, conical, spherical, elliptical, and rough and uneven surfaces, and in wells filled with borehole fluid.

[0019] A drawback of the known device is that the heater and heater temperature sensor are made of a single flexible membrane in the form of a spiral (or meander) made of brass foil 10 microns thick and 20 microns wide. The membrane surface, which is pressed against the borehole wall during measurements, is exposed and unprotected. Since the uncased borehole wall is rough and uneven, there is a high risk of damage to the thin and narrow conductive membrane coils. Damage in even one location leads to device failure, reducing the operational reliability of the device.

[0020] Since the surface of the brass membrane facing the wellbore wall is open and unprotected, it comes into contact with the wellbore fluid, which contains water and various dissolved salts. This creates parasitic conductivity paths between the conductive turns of the membrane, reducing the efficiency of the heater and heater temperature sensor and potentially causing a short circuit and device failure. This also reduces the operational reliability of the device.

[0021] Furthermore, the versatility of a flexible brass membrane, which combines the functions of a heat sink, heater, and heater temperature sensor, precludes the creation of a high-power resistive heater (with a resistance of several tens of ohms) due to the low resistivity of brass. Attempts to increase heating power by increasing the voltage supplied to the heater can lead to burnout of the membrane's conductive turns due to exceeding the maximum permissible current density across the conductor cross-section, which also reduces the operational reliability of the device.

[0022] The desire to increase the heating power by increasing the resistance of the heater by reducing the thickness of the conductive turns of the membrane, although it leads to an increase in the surface resistance of the brass foil, but at the same time the mechanical strength of the flexible membrane decreases, and as a result, the operational reliability of the device decreases.

[0023] The objective and technical result of the utility model is to create a device for determining the thermophysical characteristics of solids in uncased boreholes, ensuring increased operational reliability.

[0024] The stated problem is solved, and the required technical result is achieved by a device for determining the thermophysical characteristics of solids in uncased boreholes, containing a heat insulator, a heater, a heater temperature sensor, a clamping mechanism mechanically in contact with the heat insulator, an electronic unit in which, unlike the prototype, the clamping mechanism is made in the form of a centralizer with clamping levers in an amount of no more than four, in each of which a measuring element is embedded, consisting of a heat insulator made of a heat-electric insulating material, in which three heat receivers are installed with temperature sensors built into them, oriented along the generatrix of the inner surface of the well, wherein the central heat receiver, in addition to the temperature sensor, contains a heater made in the form of a coil made of a material with high thermal conductivity with a wound high-resistance insulated wire, which is electrically isolated from the temperature sensor,wherein the outer surface of the heat insulator with temperature sensors and a heater recessed in it is capable of taking the shape of the inner surface of the well wall under the action of the spring force, and the electronic unit is electrically connected to the heater and temperature sensors of the measuring elements.

[0025] The design of the device with temperature sensors and a heater recessed into the heat insulator ensures that the measuring elements are not subject to mechanical damage when they come into contact with the uneven surface of the well wall, which increases operational reliability.

[0026] The essence of the utility model is explained by drawings, where Fig. 1 shows a general view of a device for determining the thermophysical characteristics of solids in uncased boreholes, and Fig. 2 shows a measuring element of the device.

[0027] The device (Fig. 1) contains four measuring elements 1 mounted on clamping levers 2 of the centralizer, fixed on the body 3 of the device in such a way that the measuring elements are pressed against diametrically opposite sides of the borehole wall 4. The electronic unit, installed in the body 3, is electrically connected to the measuring elements 1. The device also contains a cable head 5 and a geophysical cable 6 for transmitting information to the surface. The measuring element (Fig. 2) consists of a heat insulator 7, in which heat receivers 8 are placed with temperature sensors 9 built into the heat receivers, in addition, a heater 10 is placed in the central heat receiver. The heater is made in the form of a coil made of a material with high thermal conductivity (for example, copper) with a wound high-resistance insulated wire, the temperature sensor and the heater are electrically isolated from each other.Miniature thermocouples are used as temperature sensors, as they are the most stable and require no adjustment. The heater is recessed into a heat insulator made of thermal and electrical insulating material. The heat insulator and heater are embedded in the clamping lever of the centralizer, with the outer surface of the heat insulator and heater protruding. The outer surface of the heat insulator and heater is flush with a small protrusion (up to 5 mm) from the outer surface of the clamping lever. Each temperature sensor, located in the heat sink of the heat insulator, contains a housing made of a material with high thermal conductivity, within which a temperature-sensitive element is installed. The outer surface of the temperature sensor housing extends outward and is flush with the outer surface of the heat insulator and heater.The measuring elements are oriented along the inner surface of the borehole, with the temperature sensors of the outer heat receivers positioned symmetrically relative to the heater temperature sensor of the central heat receiver. The outer surface of the heat insulator, heater, and temperature sensor is shaped to replicate the inner surface of the borehole wall.

[0028] The device for determining the thermophysical properties of solids in uncased boreholes operates as follows. The borehole tool with the device is lowered into the borehole. Upon reaching the study area, the heater is turned on and the temperature changes of the sensors are measured simultaneously during heating. The heater is then turned off and temperature changes are continued with sensors located along the borehole perimeter in four perpendicular directions. Next, using pre-calculated temperature change nomograms and comparing the measured temperature changes with the sensor located in the heater, the thermophysical properties of the solids are determined. By analyzing the temperature changes of the sensors in the heat receivers and comparing them with the calculated data, corrections are made for the influence of the convective component on the thermophysical properties of the solids.

[0029] The thermal activity of solids in uncased boreholes is determined using calculation formulas and established corrections for convection.

[0030] Thus, the proposed utility model makes it possible to increase the operational reliability of a device for determining the thermophysical characteristics of solids in uncased boreholes.

Claims

A device for determining the thermophysical characteristics of solids in uncased boreholes, comprising a heat insulator, a heater, temperature sensors for measuring elements, a clamping mechanism mechanically in contact with the heat insulator, an electronic unit, characterized in that the clamping mechanism is made in the form of a centralizer with four clamping levers, each of which has a measuring element embedded in it, consisting of a heat insulator made of a heat-electrically insulating material, in which three heat receivers are installed with temperature sensors for measuring elements mounted in them, oriented along the generatrix of the inner surface of the borehole, wherein the central heat receiver, in addition to the temperature sensor for the measuring element, contains a heater made in the form of a coil made of a material with high thermal conductivity with a wound high-resistance insulated wire, which is electrically isolated from the temperature sensor for the measuring element,wherein the outer surface of the heat insulator with temperature sensors of the measuring elements and a heater recessed in it is capable of taking the shape of the inner surface of the well wall under the action of the pressing force, and the electronic unit is electrically connected to the heater and temperature sensors of the measuring elements.

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