Thermal field transient method and device for underground oil-gas-water flow monitoring

Abstract

The invention relates to the technical field of oil field logging tools, in particular to a thermal field transient method and device for underground oil-gas-water flow monitoring. According to the thermal field transient method and device for underground oil-gas-water flow monitoring, a heating device is put into an underground target heating layer section for heating, so that a temperature field of underground fluid is greatly changed, and after the change process of the temperature field is recorded, the flow velocity of the underground fluid is calculated according to recorded data and parameters of a target well. According to the thermal field transient method and device for underground oil-gas-water flow monitoring, the heating device is lowered to the designated depth underground for heating, the temperature change amplitude of underground fluid is forcibly improved, accordingly, the influences such as temperature loss caused by underground environment factors are counteracted, the temperature change process is recorded, and the monitoring accuracy of the underground oil-gas-water flow is improved. And in combination with the working parameters of the target well and the inlet liquid, the flow velocity of the underground liquid can be calculated by measuring the time profile of the underground temperature field even for a low-yield and low-injection production well or a production well with too large well depth.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield logging tools, and particularly to a thermal field transient method and device for monitoring underground oil, gas and water flow rates. Background Art

[0002] During the logging process of oilfield production, the flow rate differences in each production interval underground are usually reflected by measuring the time profile of the temperature field in the underground environment, and the production profile of the reservoir is interpreted using distributed temperature data. In the prior art, due to the low production and injection state of production wells, the heat conduction power before and after well switching underground is greater than or equal to the heat convection power, resulting in no obvious temperature difference during the measurement, thus making the measurement work unable to proceed smoothly. At the same time, when the depth in the target well is too large, the long flow path of the underground fluid leads to a large amount of heat loss of the liquid in the well, which also causes no obvious temperature difference during the measurement, thus resulting in the inability to smoothly carry out the measurement work. Therefore, in view of the above deficiencies, a thermal field transient method and device for monitoring underground oil, gas and water flow rates are proposed. Summary of the Invention

[0003] (I) Technical Problems to be Solved

[0004] In view of the deficiencies of the prior art, the present invention provides a thermal field transient method and device for monitoring underground oil, gas and water flow rates, which solves the problem that when measuring a well with too large a depth or a low-production and low-injection production well, no obvious temperature difference will be generated in the underground fluid, resulting in the inability to measure the flow rate of the underground liquid by measuring the time profile of the underground temperature field.

[0005] (II) Technical Solutions

[0006] To solve the above problems, the present invention provides a thermal field transient method for monitoring underground oil, gas and water flow rates, including:

[0007] Step S1: Lower a heating device into the target well and lower the heating device to a specified depth;

[0008] Step S2: Start the heating device to exchange heat with the surrounding liquid and record the heat exchange amount;

[0009] Step S3: Set temperature measurement points underground according to work requirements. After heating for a period of time, stop the heating device and record the temperature change △T and the temperature change time at the temperature measurement points;

[0010] Step S4: Obtain the working parameters of the target well and the relevant parameters of the underground liquid, and combine the values measured in Step S2 and Step S3 to calculate the flow velocity of the underground fluid.

[0011] Further, the working parameters of the target well in Step S4 include the inner diameter of the well; the underground liquid parameters include liquid density, liquid viscosity and liquid specific heat capacity.

[0012] There is also provided a thermal field transient device for downhole oil-gas-water flow monitoring, which is applicable to the thermal field transient method for downhole oil-gas-water flow monitoring described above, and includes:

[0013] A device main body, with a heating device provided at the end of the device main body, and a number of temperature measurement points evenly arranged on the device main body from top to bottom. A temperature measurement device is provided at the temperature measurement points, and the temperature measurement device transmits temperature signals to the ground control system in real time.

[0014] Further, upper and lower plugs are respectively provided at the upper and lower ends of the heating device, and a chemical energy heat release structure is provided between the upper and lower plugs.

[0015] Further, the chemical energy heat release structure includes a tubular outer shell, and an isolation layer is provided in the middle of the outer shell; the isolation layer 104 divides the inside of the outer shell into upper and lower parts, with a liquid reactant stored in the upper half of the outer shell and a heating agent stored in the lower half.

[0016] Further, the heating agent is provided with a vertically oriented liquid guide tube, the inside of the liquid guide tube is hollow, and a plurality of liquid guide holes are evenly provided on the side wall.

[0017] Further, the heating device includes a protective layer and a heating core. The heating core is located inside the protective layer, and a wire is provided inside the heating core. The wire is bent inside the heating core, and both ends are connected to a ground power supply to form a circuit; a heating wire is provided at the bottom end of the wire.

[0018] Further, an optical fiber capillary tube is also provided inside the heating core, and an insulating material is filled between the optical fiber capillary tube, the wire and the protective layer.

[0019] Further, the protective layer is sequentially provided with an outer armor wire, an anti-corrosion protective layer, an inner armor wire, a sheath layer and a protective tube from outside to inside, and the heating core is located inside the protective tube.

[0020] Further, an insulating tube is provided outside the wire.

[0021] (III) Beneficial effects

[0022] The thermal field transient method and device for downhole oil-gas-water flow monitoring provided by the present invention lower the heating device to a specified depth downhole for heating, forcibly increasing the temperature change range of the downhole fluid, thereby offsetting the influence of temperature loss caused by downhole environmental factors, etc., recording the temperature change process, and then combining the working parameters of the target well and the downhole liquid. Even for low-production and low-injection production wells or production wells with too great a well depth, the liquid flow rate downhole can be calculated by measuring the time profile of the downhole temperature field. Description of the drawings

[0023] Figure 1Flow chart of the thermal field transient method for downhole oil-gas-water flow monitoring of the present invention;

[0024] Figure 2 Structural diagram of the chemical energy heating device of the thermal field transient device for downhole oil-gas-water flow monitoring of the present invention;

[0025] Figure 3 Cross-sectional view of the electric energy heating device of the thermal field transient device for downhole oil-gas-water flow monitoring of the present invention;

[0026] Figure 4 Structural diagram of the bottom end of the electric energy heating device of the thermal field transient device for downhole oil-gas-water flow monitoring of the present invention.

[0027] Among them, 101, upper plug; 102, outer shell; 103, reactant; 104, isolation layer; 105, liquid guide pipe; 106, heating agent; 201, outer armor wire; 202, anti-corrosion protection layer; 203, inner armor wire; 204, sheath layer; 205, protection pipe; 206, insulating material; 207, insulating pipe; 208, optical fiber capillary; 209, wire; 210, heating wire. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] In the description of the present invention, it is necessary to understand that the orientation or positional relationship indicated by "upper", "lower", "inner", "outer", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description, rather than indicating or implying that the indicated components must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0030] Embodiment 1:

[0031] As Figure 1 shown, this embodiment provides a thermal field transient method for downhole oil-gas-water flow monitoring, which is characterized by including:

[0032] Step S1: Lower the heating device into the target well and lower the heating device to the specified depth; during the preparation work, the staff needs to set the lowering position of the heating device according to the purpose of this measurement work. Usually, when multi-segment segmented measurement of the downhole is required, a heating device needs to be set in each measurement segment respectively;

[0033] Step S2: Start the heating device to exchange heat with the surrounding liquid and record the heat exchange amount. After the heating device is started, it releases heat to the surroundings and conducts heat exchange with the flowing liquid underground. After the liquid absorbs heat, its temperature rises, causing the temperature of the liquid from the heating device upward to the wellhead to rise, thereby amplifying the temperature change range of the underground liquid.

[0034] Step S3: Set temperature measurement points underground according to work requirements. After heating for a period of time, stop the heating device and record the temperature change amount and temperature change time at the temperature measurement points. After heating for a period of time, the temperature of the underground liquid from the heating device to the wellhead usually reaches the highest temperature that the heating effect of the heating device can reach. After stopping the heating device, as the underground liquid continuously flows upward, the heated underground liquid will gradually cool down and return to the initial temperature. During this process, the greater the flow rate of the underground liquid, the faster the liquid temperature drops. By measuring the law of the temperature change of the liquid flowing through the temperature measurement points over time, the time for the underground fluid to flow from the heating device to the temperature measurement points when the heating device is working and the time for the underground liquid at the temperature measurement points to cool down after the heating device stops working can be obtained.

[0035] Step S4: Obtain the working parameters of the target well and the relevant parameters of the underground liquid, and combine the measured values in Step S2 and Step S3 to calculate the flow velocity of the underground fluid. During the calculation process, assume that the height difference between the measurement point and the heating device is d, and the time for the temperature at the measurement point to gradually drop from the highest point to the initial temperature is t. At this time, t also represents the time for the underground liquid at the heating device to flow to the measurement point after the heating device stops heating. Thus, the expression for calculating the underground liquid flow velocity can be obtained as v = d / t.

[0036] However, the heat conduction loss is ignored in the above calculation process, and it can only be applied to situations where the accuracy requirements for the calculation results are not high, such as estimations, and only approximate values are needed.

[0037] In actual measurement work, the heat conduction loss in the underground environment needs to be considered. At this time, parameters such as the inner diameter of the well, liquid density, liquid viscosity, and liquid specific heat capacity need to be measured. Denote the diameter of the target well as r1, the liquid density as ρ, the liquid specific heat capacity as c p , and the heat conductivity between the liquid and the heating device as k.

[0038] The apparent heat conductivity per unit length of the wellbore is , where r2 is the radius of the formation thermal influence.

[0039] The initial temperature of the liquid is T1, and the temperature rise relative to the ambient temperature T0 is △T1 = T1 - T0. The liquid flows upward at a flow velocity v and reaches the wellhead after time t. At this time, the temperature drops to T2, and the temperature rise is △T2 = T2 - T0.

[0040] Average temperature rise △T avg =(△T1+△T2) / 2.

[0041] Total heat loss Q = ρAdc p (△T1-△T2), where A is the cross-sectional area of the well.

[0042] At the same time, based on heat conduction loss, , the two equations are combined to obtain

[0043] , set t=d / v and A=πr 2 Substituting it into this, we get .in, , h is the total heat transfer coefficient.

[0044] Through the above calculation process, the flow rate of the downhole fluid can be obtained.

[0045] Example 2:

[0046] like Figure 2 As shown, based on the thermal field transient method for downhole oil, gas and water flow monitoring provided in Example 1, this embodiment proposes a thermal field transient device for downhole oil, gas and water flow monitoring, which is used to implement the method in Example 1, including:

[0047] The device body has a heating device at the end thereof. Several temperature measuring points are evenly arranged on the device body from top to bottom, and temperature measuring devices are provided on the temperature measuring points. The temperature measuring devices transmit temperature signals to the ground control system in real time.

[0048] The heating device is equipped with an upper plug 101 and a lower plug 107 at its upper and lower ends, respectively. A chemical heat release structure is located between the upper and lower plugs 101 and 107. The heating device is connected to other components of the device body via the upper and lower plugs 101 and 107. The chemical heat release structure is filled with chemicals. When not in operation, the chemicals are isolated from each other. When heating is required, the two chemicals are mixed, and the heat released by the chemical reaction heats the surrounding environment and the fluid downhole.

[0049] The chemical energy exothermic structure includes a tubular outer shell 102, and an isolation layer 104 is provided in the middle of the outer shell 102; the isolation layer 104 divides the inside of the outer shell 102 into upper and lower parts. The upper half of the outer shell 102 stores the liquid reactant 103, and the lower half stores the heating agent 106. The outer shell 102 serves as the main body of the chemical energy exothermic structure, playing a supporting role and also used to load the chemical agents in the device. The isolation layer 104 is used to separate the chemical agents in the outer shell 102 to prevent the agents from contacting and reacting before heating. When heating work needs to be carried out, the isolation layer 104 can be damaged or removed to enable the agents to be mixed and release heat. Usually, due to the limited space inside the outer shell 102, when selecting the chemical reactions to be used, exothermic reactions that only require the mixing of two agents should be selected as much as possible to simplify the structure of the device. Usually, in order for the two agents to be fully mixed and react, the way of mixing solid agents and liquid agents is usually selected when choosing the agents. The solid agent is used as the heating agent 106 and placed below the isolation layer 104, and the liquid agent is used as the reactant 103 and placed above the isolation layer 104. Usually, the reaction between water and quicklime is selected as the chemical reaction during heating. The corresponding reactant 103 is water and is stored above the isolation layer 104, and quicklime is used as the heating agent 106 and placed below the isolation layer 104. When water and quicklime are separated and stored separately, they are both stable, safe enough and will not corrode the outer shell 102. Moreover, the two agents are difficult to obtain during daily work. Considering the comprehensive economy and safety, the reaction process between water and quicklime is the optimal solution for selecting chemical reactions in this device. During the working process, when the required heat release of the reaction is too large, the heat release of the reaction can be increased by increasing the dosage, or other chemical reactions with a higher heat release can be selected as the chemical reaction in the chemical exothermic structure and the corresponding agents can be selected as the heating agent 106 and the reactant 103.

[0050] Among them, the isolation layer 104 usually selects paraffin as the raw material. The temperature in the well is usually higher than the melting point of paraffin. After being lowered into the well with the device, the paraffin-made isolation layer 104 will gradually melt. By adjusting the volume of the isolation layer 104, its melting time can be controlled so that the isolation layer 104 melts after the device reaches the heating position. After the isolation layer 104 melts, the reactant 103 above flows downward under the action of gravity and contacts the heating agent 106 below to react and release heat.

[0051] It should be noted that the heating agent 106 is provided with a vertical liquid guide tube 105. The liquid guide tube 105 is hollow inside and has multiple liquid guide holes evenly distributed on the sidewall. After the isolation layer 104 melts, some of the reactants 103 directly contact the upper surface of the heating agent 106, while some of the reactants 103 flow into the liquid guide tube 105 and react with the heating agent 106 along the liquid pouring holes. This increases the contact area between the heating agent 106 and the reactants 103, improves the mixing efficiency between the two, and prevents the device's heat release efficiency from being reduced due to insufficient mixing and reaction between the two.

[0052] In addition, the isolation layer 104 can also adopt a mechanical structure, and a power device is installed on the isolation layer 104. When the reaction needs to release heat, the power device is controlled to destroy or remove the isolation layer 104 to realize the contact reaction of the reactant 103 and the heating agent 106. However, due to the limited space in the outer shell 102, the mechanical structure needs to consider avoiding contact between the power device and the reactant 103 and the heating agent 106. The production cost is high and it is prone to failure. Therefore, the mechanical structure is not considered except for special work requirements.

[0053] Since the reaction time is controlled by the melting time of the isolation layer 104, for production wells with deeper depths, a large amount of paraffin needs to be filled as the isolation layer 104 to ensure that the melting time of the isolation layer 104 is later than the time it takes for the device to be lowered to the target well depth. However, a large amount of paraffin will cause the reactant 103 and the heating agent 106 to be unable to fully contact and mix during the subsequent chemical reaction and heat generation process, affecting the heat release efficiency of the device. Therefore, the solution of using a chemical heating structure as a heating device is more suitable for heating and subsequent calculation work in working conditions where the heating position is not deep, such as low-injection and low-yield production wells. During the operation, only one temperature measuring point needs to be set at the wellhead. It should be noted that during the preparation process, a sufficient amount of reagent needs to be filled in the outer shell 102 to ensure that the temperature change can be measured at the wellhead position after the device is heated underground.

[0054] Example 3:

[0055] like Figure 3 、 Figure 4As shown in the figure, based on Embodiment 2, the present invention further provides another implementation manner of the heating device. The difference from Embodiment 2 is that the heating device includes a protective layer and a heating core. The heating core is located inside the protective layer. A wire 209 is provided inside the heating core. The wire 209 is bent inside the heating core, and both ends are connected to the ground power supply to form a loop; a heating wire 210 is provided at the bottom end of the wire 209. The difference between this embodiment and Embodiment 2 is that in this embodiment, the heating wire 210 is energized to generate heat as the heat source of the device, rather than chemical energy. In this embodiment, the heating core is used to be energized for heating and is connected to the temperature measuring device in the device to transmit the temperature signal measured by the temperature measuring device. After the device is placed in the well, the wire 209 is energized. Since both ends of the wire 209 are connected to the ground power supply to form a loop, the heating wire 210 on the wire 209 is energized to generate heat and transfer the heat to the surrounding downhole liquid. During the working process, only a cable long enough according to the working needs needs to be processed as the heating device, and the heating wire 210 at the bottom end can be lowered to any depth along the production well for heating.

[0056] Wherein, an optical fiber capillary 208 is further provided inside the heating core. An insulating material 206 is filled between the optical fiber capillary 208, the wire 209 and the protective layer. The optical fiber capillary 208 is mainly used to transmit digital signals. When manufacturing the heating device, a temperature measuring device needs to be installed on the heating device according to the working needs. At this time, the optical fiber capillary 208 is connected to the temperature measuring device, and the top end of the optical fiber capillary 208 is connected to the control equipment on the ground to transmit the temperature signal measured by the downhole temperature measuring device to the control equipment on the ground for data acquisition. The material of the insulating material 206 is generally a rubber-like insulating material with good elasticity.

[0057] It should be noted that the protective layer is sequentially provided with an outer armor wire 201, an anti-corrosion protective layer 202, an inner armor wire 203, a sheath layer 204 and a protective tube 205 from outside to inside. The heating core is located inside the protective tube 205. After the heating core is inserted into the protective tube 205, the void inside the protective tube 205 is filled with an insulating material. At this time, the protective layer is arranged layer by layer from inside to outside on the outer wall of the protective tube 205. The protective tube 205 is usually a stainless steel tube or an alloy steel tube, which is mainly used to isolate external pressure and protect the optical fiber and the wire from being squeezed and damaged.

[0058] The sheath layer 204 is usually a seamless stainless steel tube or a galvanized steel tube. After wrapping the protective tube 205, an electromagnetic shield is formed inside to eliminate external electromagnetic interference. In order to further improve the effect of internal and external isolation, an insulating material such as polyethylene or epoxy resin is usually coated on the outer wall of the sheath layer 204.

[0059] The outer armor steel wires 201 and the inner armor steel wires 203 are usually tightly woven by galvanized steel wires or stainless steel wires to provide mechanical support for the heating device and improve the tensile and extrusion resistance of the heating device. An anti-corrosion protection layer 202 is filled between the outer armor steel wires 201 and the inner armor steel wires 203 for anti-corrosion treatment. Usually, the anti-corrosion protection layer 202 includes two layers, the inner layer is an anti-corrosion film made of polyethylene film or other insulating and anti-corrosion materials, and the outer layer is an anti-corrosion sealing medium composed of high-molecular materials such as epoxy resin or polyethylene, which prevents the fluid from continuing to penetrate into the inner armor steel wires 203 after passing through the outer armor steel wires 201.

[0060] An insulating tube 207 is provided outside the wire 209. By wrapping an insulating tube 207 outside the wire 209, the wire 209 is supported and protected to prevent the wire 209 from being squeezed and bent during operation. The insulating tube 207 is usually a stainless steel tube, and a high-temperature-resistant insulating material such as polyvinyl fluoride is filled between the inside and the wire 209.

[0061] Usually, the material of the wire 209 is copper wire, and the material of the heating wire 210 is nickel-chromium alloy. During the heating process, direct current is passed through the wire 209. Since the resistance of the heating wire 210 is relatively large, the heat generation power generated after energization is relatively higher than that of the wire. After increasing the current, different heat generation powers are formed in the wire 209 section and the heating wire 210 section, so as to achieve key heating of the target layer and achieve the effect of greatly changing the temperature field of the target layer section. After energization, while the heating wire heats the target position, the wire 209 always heats the surrounding downhole liquid, and the heat dissipated by the wire 209 is used to offset the heat loss of the downhole liquid during the flow along the well. Thus, the temperature field changes can be measured at each temperature measurement point in the device.

[0062] Usually, in order to improve the applicability of the device, in this embodiment, a cable of sufficient length is usually processed as the heating device. However, due to the relatively large total length of the cable, for some heating measurement work with relatively shallow heating depths, the transportation cost of the cable is relatively high. Therefore, the heating device using electric heating proposed in this embodiment is usually applicable to heating measurement work with relatively deep heating positions.

[0063] Combining Embodiment 1, Embodiment 2 and Embodiment 3, the downhole oil-gas-water flow monitoring thermal field transient method and device provided by the present invention can amplify the change amplitude of the downhole temperature field by heating, and then calculate the flow rate of the downhole liquid by measuring the change of the downhole temperature field. The specific operation process of the present invention is as follows:

[0064] Step 1: Select a suitable heating method and the corresponding heating device according to the working requirements. When the heating position is relatively shallow, select the chemical energy heating method and the corresponding device. When the heating position is relatively deep, select the electric heating method and the corresponding heating device.

[0065] Step 2: Lower the device into the well along the wellhead and lower the heating device to the heating position.

[0066] Step 3: Start the heating device for heating. After the heating device is started, heat the surrounding target interval. At this time, the liquid flowing through the target interval absorbs heat and the temperature rises, resulting in the temperature of the fluid gradually increasing from the heating device upwards, increasing the variation range of the temperature field of the downhole fluid.

[0067] Step 4: Stop heating after heating for a period of time, record the relationship between the temperature change at the measurement point and time, and calculate the fluid flow rate. After stopping heating, the temperature of the downhole fluid gradually decreases. Record the process of temperature change at the measurement point. According to the measured data and the parameters of the target well itself, calculate the flow rate of the downhole fluid according to the calculation process in Embodiment 1.

[0068] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermal field transient method for downhole oil-gas-water flow monitoring, characterized in that, Including: Step S1: Lower a heating device into the target well and lower the heating device to a specified depth; Step S2: Start the heating device to exchange heat with the surrounding liquid and record the heat exchange amount; Step S3: Set temperature measurement points underground according to working needs. After heating for a period of time, stop the heating device and record the temperature change amount and temperature change time of the temperature measurement points; Step S4: Obtain the working parameters of the target well and the relevant parameters of the downhole liquid, and combine the values measured in Step S2 and Step S3 to calculate the flow velocity of the downhole fluid.

2. The transient thermal field method for downhole oil-gas-water flow monitoring according to claim 1, characterized in that, The working parameters of the target well in Step S4 include the inner diameter of the well; the downhole liquid parameters include liquid density, liquid viscosity, and liquid specific heat capacity.

3. A thermal field transient device for downhole oil-gas-water flow monitoring, applicable to the thermal field transient method for downhole oil-gas-water flow monitoring described in claim 1, characterized in that, Including: The device main body, a heating device is provided at the end of the device main body, and several temperature measurement points are evenly arranged on the device main body from top to bottom. A temperature measurement device is provided on the temperature measurement points, and the temperature measurement device transmits temperature signals to the ground control system in real time.

4. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 3, characterized in that, Upper and lower plugs (101) and (107) are respectively provided at the upper and lower ends of the heating device, and a chemical energy heat release structure is provided between the upper plug (101) and the lower plug (107).

5. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 4, characterized in that The chemical energy heat release structure includes a tubular outer shell (102), and an isolation layer (104) is provided in the middle of the outer shell (102); the isolation layer 104 divides the inside of the outer shell (102) into upper and lower parts. The upper half of the outer shell (102) stores the liquid reactant (103), and the lower half stores the heating agent (106).

6. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 5, characterized in that, The heating agent (106) is provided with a vertically directed liquid guide tube (105), the inside of the liquid guide tube (105) is hollow, and a plurality of liquid guide holes are evenly provided on the side wall.

7. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 3, wherein, The heating device includes a protective layer and a heating core. The heating core is located inside the protective layer. A wire (209) is provided in the heating core, and the wire (209) is bent inside the heating core. The two ends are connected to the ground power supply to form a circuit; a heating wire (210) is provided at the bottom end of the wire (209).

8. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 7, characterized in that, An optical fiber capillary (208) is also provided in the heating core, and an insulating material (206) is filled between the optical fiber capillary (208), the wire (209), and the protective layer.

9. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 8, characterized in that The protective layer is sequentially provided with an outer armor wire (201), an anti-corrosion protective layer (202), an inner armor wire (203), a sheath layer (204), and a protective tube (205) from the outside to the inside. The heating core is located inside the protective tube (205).

10. The transient thermal field device for downhole oil-gas-water flow monitoring according to claim 9, wherein, An insulating tube (207) is provided outside the wire (209).

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