Double-layer continuous pipe electric heater based on temperature thermocouple and use method

Abstract

The invention belongs to the technical field of underground electric heating, and particularly relates to a double-layer continuous pipe electric heater based on a temperature thermocouple and a using method. A double-layer continuous pipe electric heater based on a temperature thermocouple comprises a continuous pipe outer sheath, the continuous pipe outer sheath is filled with second filler, a plurality of heating cable units are arranged in the second filler, each heating cable unit comprises a heating core wire, a cable sheath is arranged on the outer side of the heating core wire in a sleeving mode, and the cable sheath is arranged in the continuous pipe outer sheath. A first filler is arranged between the cable sheath and the heating core wire, and a temperature thermocouple is arranged in the second filler between the adjacent heating cable units. By adopting a double-layer structure that the coiled tubing outer sheath wraps the cable sheath and the cable sheath wraps the heating core wire, a joint structure is eliminated, the overall reliability of the underground electric heater is improved, meanwhile, a temperature thermocouple is arranged in the underground electric heater, the temperature can be measured more accurately while heating is conducted, the heating control precision is improved, and the underground electric heater is suitable for popularization and application. And the heating efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of underground electric heating, and in particular relates to a double-layer coiled tube electric heater based on a temperature measuring thermocouple and a use method thereof. Background Art

[0002] With the massive depletion of conventional oil and gas resources and the continuous rise in oil demand, heavy oil resources, with their wide distribution, huge reserves, and low reserve utilization rate, have become the main potential for lower-level development. Among the currently proven heavy oil reserves, a considerable portion of the unused heavy oil reserves are sensitive heavy oil reservoirs.

[0003] In the existing technology, sensitive heavy oil reservoirs are usually exploited by steam injection thermal recovery. However, since sensitive oil reservoirs are prone to clay swelling when exposed to water, the seepage channels are blocked, the seepage capacity is reduced, and even the seepage channels are completely blocked. At the same time, the oil layers of sensitive heavy oil reservoirs are thin, resulting in increased heat loss from the upper and lower cover layers due to the steam injected into the oil layers, a smaller lateral sweep volume in the oil layers, and a lower heat utilization rate. In addition, due to the serious heterogeneity of the oil layers in sensitive heavy oil reservoirs and large differences between layers, the seepage capacity is poor, resulting in a low degree of reserve utilization in the vertical direction of the oil layers. At the same time, as the steam throughput cycle increases, the water recovery rate increases and the underground water storage volume is large, resulting in unsatisfactory oil recovery results.

[0004] The oil reservoir electric heating production device disclosed in Chinese Patent No. 201410098385X utilizes multiple steel-armored heating cables attached to the outer surface of a hollow sucker rod to uniformly heat the heavy oil entering the rod. However, these steel-armored heating cables only heat the heavy oil within the rod, resulting in limited heating effectiveness. Furthermore, the power consumption of these steel-armored heating cables increases with increasing well depth, reducing their effectiveness and preventing targeted heating of the oil reservoir being produced. Chinese patent CN 210899705 U discloses a downhole oil layer heating cable. The outer sheath of the heating cable is made of a 9-meter seamless steel pipe, which is extended by butt welding. The butt joint poses a serious risk to reliability. The outer sheath has insufficient pressure and corrosion resistance at high temperatures, and the reusability rate is low. The heating cable lacks an effective temperature measurement method. The heater temperature is adjusted by measuring the wellhead temperature or the downhole heavy oil temperature. The temperature control is relatively lagging, and the heating temperature is prone to overshoot, causing heavy oil to accumulate. Alternatively, to prevent temperature overshoot, the heating temperature is set low, affecting heating efficiency. Summary of the Invention

[0005] In response to the above problems, the present invention aims to provide a double-layer coiled tubing electric heater based on temperature-measuring thermocouples and a method for use. By adopting a double-layer structure in which the coiled tubing outer sheath wraps the cable sheath, which in turn wraps the heating core wire, the joint structure is eliminated, thereby improving the overall reliability of the downhole electric heater. At the same time, a temperature-measuring thermocouple for multi-point temperature measurement is provided internally. During heating, the temperature can be measured more accurately, improving the control accuracy of heating and increasing the heating efficiency. The use of coiled tubing as the outer sheath of the electric heater product combines the excellent characteristics of coiled tubing products, such as high strength, good toughness, corrosion resistance, high temperature resistance, and long fatigue life, and can significantly extend the service life of the outer sheath in downhole.

[0006] The technical solution of the present invention is: a double-layer coiled tubing electric heater based on a temperature measuring thermocouple, comprising a coiled tubing outer sheath, the interior of the coiled tubing outer sheath being filled with a second filler, a plurality of heating cable units being arranged in the second filler, the heating cable units comprising a heating core wire, the outer side of the heating core wire being sheathed with a cable sheath, a first filler being arranged between the cable sheath and the heating core wire, and a temperature measuring thermocouple being further arranged in the second filler between adjacent heating cable units.

[0007] The number of the heating cable units is 3 to 10, and the heating cable units are evenly distributed in the second filler with the central axis of the continuous pipe outer sheath. The number of the temperature measuring thermocouples is 3 to 10, and the temperature measuring thermocouples are located between adjacent heating cable units and close to the pipe wall of the continuous pipe outer sheath.

[0008] The length of the temperature measuring thermocouple is ≥1000m, the temperature measuring range of the temperature measuring thermocouple is -200℃~+1250℃, the temperature measuring accuracy is ±1℃, the temperature resolution is 0.1℃, and the maximum deformation range of the temperature measuring thermocouple while ensuring the temperature resolution is 30%~35%.

[0009] A stainless steel armored outer sheath is provided on the outside of the temperature measuring thermocouple, and the diameter of the stainless steel armored outer sheath ranges from 3 to 5 mm.

[0010] The first filler and the second filler have the same composition, both being magnesium oxide powder.

[0011] The outer sheath of the continuous pipe and the cable sheath are made of the same material, namely 316L, 310S, and 825 stainless steel, and the heating core wire is made of 6J40 and Cr20Ni80.

[0012] A method for using a double-layer coiled tube electric heater based on a temperature measuring thermocouple, using the double-layer coiled tube electric heater based on a temperature measuring thermocouple as described above, comprising the following steps: S1: Determine the heating temperature based on the initial viscosity, freezing point, cracking temperature of the crude oil in the oil layer to be heated and the formation temperature. The heating temperature is higher than the original freezing point and lower than the cracking temperature of the crude oil. S2: Use a coiled tubing vehicle to lower a double-layer coiled tubing electric heater based on a temperature measuring thermocouple directly into the oil layer to be heated in the oil well; S3: Start the double-layer coiled tubing electric heater based on the temperature measuring thermocouple to heat the oil layer to be heated, and monitor the temperature changes of the oil well in real time, including the oil well outlet temperature and crude oil temperature; S4: According to the temperature change of the oil well, the heating temperature of the double-layer coiled tubing electric heater based on the temperature measuring thermocouple is adjusted, and the temperature measuring thermocouple is used for monitoring to complete the heating of the oil layer to be heated.

[0013] The technical effects of the present invention are: 1. The present invention improves the overall reliability of the downhole electric heater by adopting a double-layer structure in which the outer sheath of the continuous tube wraps the cable sheath, which in turn wraps the heating core wire. The pressure resistance and corrosion resistance of the outer sheath at high temperatures are improved, and the reuse rate is high; 2. The present invention is provided with a multi-point temperature measurement thermocouple inside the outer sheath of the continuous tube. While heating, the temperature can be measured more accurately, the control accuracy of the heating is improved, the heating efficiency is improved, and the heating temperature is prevented from being too high, causing heavy oil to solidify; 3. The present invention facilitates oilfield downhole operations by adopting a structure in which the outer sheath of the continuous tube wraps the heating core wire, which can reduce the downhole operation of one temperature measuring cable, thereby improving the efficiency of downhole operations. At the same time, the temperature signal has strong anti-interference ability, and the temperature signal can be accurately transmitted to the wellhead.

[0014] The following is a further description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic structural diagram of a double-layer coiled tube electric heater based on a temperature measuring thermocouple according to an embodiment of the present invention.

[0016] Reference numerals: 1 - outer sheath of continuous tube; 2 - cable sheath; 3 - first filler; 4 - temperature measuring thermocouple; 5 - heating core wire; 6 - second filler. DETAILED DESCRIPTION Example 1

[0017] like Figure 1As shown, a double-layer coiled tubing electric heater based on temperature measuring thermocouples includes a coiled tubing outer sheath 1, the interior of the coiled tubing outer sheath 1 is filled with a second filler 6, a plurality of heating cable units are arranged in the second filler 6, and the heating cable units include heating core wires 5, the outer side of the heating core wires 5 is sheathed with a cable sheath 2, a first filler 3 is arranged between the cable sheath 2 and the heating core wires 5, and a temperature measuring thermocouple 4 is further arranged in the second filler 6 between adjacent heating cable units.

[0018] During actual use, the present invention adopts a structure in which the heating core wire is wrapped with a continuous tube outer sheath, thereby eliminating the joint structure, improving the overall reliability of the downhole electric heater, improving the pressure resistance and corrosion resistance of the outer sheath at high temperatures, and having a high reuse rate; the present invention provides a multi-point temperature measurement thermocouple inside the outer sheath of the continuous tube, which can measure the temperature more accurately during heating, improve the control accuracy of heating, improve the heating efficiency, and prevent the heating temperature from being too high to cause heavy oil agglomeration; the present invention adopts a structure in which the heating core wire is wrapped with a continuous tube outer sheath, which facilitates oilfield downhole operations, can reduce the downhole operation of one temperature measuring cable, and improves the efficiency of downhole operations. At the same time, the temperature signal has a strong anti-interference ability, and the temperature signal can be accurately transmitted to the wellhead. Example 2

[0019] Preferably, based on Example 1, in this embodiment, the number of the heating cable units is 3 to 10, and the heating cable units are evenly distributed in the second filler 6 with the central axis of the continuous pipe outer sheath 1. The number of the temperature measuring thermocouples 4 is 3 to 10, and the temperature measuring thermocouples 4 are located between adjacent heating cable units and close to the pipe wall of the continuous pipe outer sheath 1.

[0020] During actual use, the heating cable units of the present invention are evenly distributed within the second filler 6 with the central axis of the coiled tubing outer sheath 1, ensuring the uniformity of the temperature around the coiled tubing outer sheath 1 during heating. The temperature measuring thermocouple 4 is located between adjacent heating cable units and close to the pipe wall of the coiled tubing outer sheath 1, ensuring that the temperature measuring thermocouple 4 can detect the heating temperature of the oil layer position by the heating core wire 5. Example 3

[0021] Preferably, based on Example 1 or Example 2, in this embodiment, the length of the temperature measuring thermocouple 4 is ≥1000m, the temperature measuring range of the temperature measuring thermocouple 4 is -200℃~+1250℃, the temperature measurement accuracy is ±1℃, the temperature resolution is 0.1℃, and the maximum deformation range of the temperature measuring thermocouple 4 while ensuring the temperature resolution is 30%~35%.

[0022] During actual use, the length of the temperature measuring thermocouple 4 of the present invention is ≥1000m, which can realize temperature measurement in the continuous production process. The temperature measuring range of the temperature measuring thermocouple 4 is -200℃~+1250℃, the temperature measurement accuracy is ±1℃, and the temperature resolution is 0.1℃, which ensures that the temperature measuring thermocouple 4 has accurate temperature measurement performance. The maximum deformation range of the temperature measuring thermocouple 4 while ensuring the temperature resolution is 30%~35%, which ensures that the temperature measuring thermocouple 4 does not fail during the rolling and drawing process of the downhole electric heater. Example 4

[0023] Preferably, based on Example 1, in this embodiment, a stainless steel armored outer sheath is provided on the outer side of the temperature measuring thermocouple 4, and the diameter of the stainless steel armored outer sheath ranges from 3 to 5 mm.

[0024] During actual use, a stainless steel armored outer sheath is provided on the outside of the temperature measuring thermocouple 4 of the present invention, which can effectively protect the temperature measuring thermocouple 4. The diameter of the stainless steel armored outer sheath ranges from 3 to 5 mm, which facilitates the integrated manufacturing of the temperature measuring thermocouple 4 in the continuous tube outer sheath 1. Example 5

[0025] Preferably, based on Example 1 or Example 4, in this embodiment, the first filler 3 and the second filler 6 have the same composition, both of which are magnesium oxide powder.

[0026] In actual use, the first filler 3 and the second filler 6 of the present invention have the same composition, both of which are magnesium oxide powder, which is convenient for filling the outer sheath 1 of the continuous pipe and the cable sheath 2. Example 6

[0027] Preferably, based on Example 1 or Example 5, in this embodiment, the coiled tube outer sheath 1 and the cable sheath 2 are made of the same material, 316L, 310S, 825 stainless steel, and the heating core wire 5 is made of 6J40, Cr20Ni80.

[0028] In actual use, the coiled tubing outer sheath 1 and the cable sheath 2 of the present invention are made of the same material, namely 316L, 310S, and 825 stainless steel. The heating core wire 5 is made of 6J40 and Cr20Ni80. After manufacture, the downhole electric heater can continuously produce 2500m, has an operating voltage of 3000V, a maximum power of 0.3MW, and a diameter of φ31.8mm-φ88.9mm. Example 7

[0029] A method for using a double-layer coiled tube electric heater based on a temperature measuring thermocouple, using the double-layer coiled tube electric heater based on a temperature measuring thermocouple as described above, comprising the following steps: S1: Determine the heating temperature based on the initial viscosity, freezing point, cracking temperature of the crude oil in the oil layer to be heated and the formation temperature. The heating temperature is higher than the original freezing point and lower than the cracking temperature of the crude oil. S2: Use a coiled tubing vehicle to lower a double-layer coiled tubing electric heater based on a temperature measuring thermocouple directly into the oil layer to be heated in the oil well; S3: Start the double-layer coiled tubing electric heater based on the temperature measuring thermocouple to heat the oil layer to be heated, and monitor the temperature changes of the oil well in real time, including the oil well outlet temperature and crude oil temperature; S4: According to the temperature change of the oil well, the heating temperature of the double-layer coiled tubing electric heater based on the temperature measuring thermocouple is adjusted, and the temperature measuring thermocouple 4 is used for monitoring to complete the heating of the oil layer to be heated.

[0030] The actual operating temperature of the double-layer coiled tubing electric heater based on the temperature measuring thermocouple in the well is precisely controlled by using PLC+touch screen+thyristor power regulator. By setting the heating temperature, the PLC uses 485 communication to control the power output of the thyristor power regulator and the operating power of the double-layer coiled tubing electric heater based on the temperature measuring thermocouple. The operating temperature of the double-layer continuous tube electric heater based on temperature measuring thermocouple is collected into the PLC through the integrated temperature measuring thermocouple 4 through the transmitter and displayed in real time on the touch screen.

[0031] The control of the double-layer coiled tube electric heater based on temperature measuring thermocouples has three control modes: automatic, remote and local: Automatic control method: During the heating process of the double-layer coiled tubing electric heater based on thermocouples, if the temperature difference measured by thermocouple 4 is greater than 80°C, the PLC controls the PID control of the power regulator to maintain a constant temperature output to prevent the heating core 5 of the double-layer coiled tubing electric heater from overheating and melting. This is done until the temperature difference of the double-layer coiled tubing electric heater based on thermocouples is less than 10°C. The PLC then continues to control the power regulator to increase the temperature. When the temperature is less than or equal to 100°C from the target temperature, the PLC controls the thyristor power regulator to reduce the input power and heat at 50% power to prevent reservoir sintering caused by temperature overshoot. When the temperature is less than or equal to 50°C, the PLC controls the thyristor power regulator to reduce the power to 20% for heating. When the temperature is less than or equal to 10°C from the set temperature, the PLC controls the thyristor power regulator to maintain constant temperature control by PID control.

[0032] Remote control: By establishing 5G wireless communication with the oilfield production and operation center, the operating parameters of the double-layer coiled tubing electric heater based on temperature measuring thermocouples, including current, voltage, temperature, operating time, abnormal alarms, etc., are uploaded to the data acquisition server in real time. Operation and maintenance operators can remotely monitor the electric heater through mobile phone apps, computers, and large control screens, and obtain real-time operating parameters and alarm information.

[0033] Local control: The operating temperature is set directly through the on-site touch screen to control the start / stop of the double-layer coiled tube electric heater based on temperature measuring thermocouples. Local control is mainly used during on-site operations, equipment commissioning, and electric heater inspection and maintenance.

[0034] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A double-layer coiled tube electric heater based on a temperature measuring thermocouple, characterized in that: The invention comprises a continuous tube outer sheath (1), wherein the interior of the continuous tube outer sheath (1) is filled with a second filler (6), a plurality of heating cable units are arranged in the second filler (6), the heating cable units include a heating core wire (5), the outer side of the heating core wire (5) is sheathed with a cable sheath (2), a first filler (3) is arranged between the cable sheath (2) and the heating core wire (5), and a temperature measuring thermocouple (4) is further arranged in the second filler (6) between adjacent heating cable units.

2. The double-layer coiled tube electric heater based on temperature measuring thermocouple according to claim 1, characterized in that: The number of the heating cable units is 3 to 10, and the heating cable units are evenly distributed in the second filler (6) along the central axis of the continuous pipe outer sheath (1). The number of the temperature measuring thermocouples (4) is 3 to 10, and the temperature measuring thermocouples (4) are located between adjacent heating cable units and close to the pipe wall of the continuous pipe outer sheath (1).

3. The double-layer coiled tube electric heater based on temperature measuring thermocouple according to claim 1, characterized in that: The length of the temperature measuring thermocouple (4) is ≥1000m, the temperature measuring range of the temperature measuring thermocouple (4) is -200°C to +1250°C, the temperature measuring accuracy is ±1°C, the temperature resolution is 0.1°C, and the maximum deformation range of the temperature measuring thermocouple (4) under the condition of ensuring the temperature resolution is 30% to 35%.

4. The double-layer coiled tube electric heater based on temperature measuring thermocouple according to claim 1, characterized in that: The temperature measuring thermocouple (4) is provided with a stainless steel armored outer sheath on the outside, and the diameter of the stainless steel armored outer sheath ranges from 3 to 5 mm.

5. The double-layer coiled tube electric heater based on temperature measuring thermocouple according to claim 1, characterized in that: The first filler (3) and the second filler (6) have the same composition, both being magnesium oxide powder.

6. The double-layer coiled tube electric heater based on temperature measuring thermocouple according to claim 1, characterized in that: The continuous tube outer sheath (1) and the cable sheath (2) are made of the same material, namely 316L, 310S, and 825 stainless steel, and the heating core wire (5) is made of 6J40 and Cr20Ni80.

7. A method for using a double-layer coiled tube electric heater based on a temperature measuring thermocouple, using the double-layer coiled tube electric heater based on a temperature measuring thermocouple according to claim 1, characterized in that: The following steps are involved: S1: Determine the heating temperature based on the initial viscosity, freezing point, cracking temperature of the crude oil in the oil layer to be heated and the formation temperature. The heating temperature is higher than the original freezing point and lower than the cracking temperature of the crude oil. S2: Use a coiled tubing vehicle to lower a double-layer coiled tubing electric heater based on a temperature measuring thermocouple directly into the oil layer to be heated in the oil well; S3: Start the double-layer coiled tubing electric heater based on the temperature measuring thermocouple to heat the oil layer to be heated, and monitor the temperature changes of the oil well in real time, including the oil well outlet temperature and crude oil temperature; S4: According to the temperature change of the oil well, the heating temperature of the double-layer continuous tube electric heater based on the temperature measuring thermocouple is adjusted, and the temperature measuring thermocouple (4) is used for monitoring to complete the heating of the oil layer to be heated.

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