A wellbore temperature balance test device and test method

Abstract

The present invention discloses a wellbore temperature balance test device and a test method, which include a base. An outer protection cylinder, a cylinder barrel, a cement sheath, a casing and a tubing are arranged coaxially on the upper end surface of the base. A heating rod is arranged inside the tubing, and the inner wall of the cement sheath is attached to the outer wall of the casing; a first cover plate is arranged at the tops of the casing and the tubing, and a second cover plate is arranged at the tops of the outer protection cylinder and the cylinder barrel; an oil tubing temperature and pressure control valve communicating with the tubing, a casing temperature and pressure control valve and a casing outflow valve communicating with the casing are arranged on the first cover plate; an outer protection cylinder injection valve and an outer protection cylinder outflow valve communicating with the outer protection cylinder, a cylinder barrel injection valve and a cylinder barrel outflow valve communicating with the cylinder barrel are arranged on the second cover plate; temperature sensors are arranged on the inner wall of the outer protection cylinder, the inner wall of the cylinder barrel, the outer wall of the cement sheath, the inner and outer walls of the casing and the inner and outer walls of the tubing. The present invention can obtain the radial variation of injection and production temperatures and the balance relationship over time, providing an experimental basis for reasonably setting the injection-production balance period.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas production engineering, and particularly relates to a wellbore temperature balance test device and a test method. Background Art

[0002] During the production operation of underground gas storage wells, heavy oil thermal recovery wells, etc., due to the large injection and production of gas storage wells and the temperature changes during steam stimulation of heavy oil wells, the wellbore temperature changes. Excessive temperature changes generate large axial loads. Especially during the injection-production conversion process, the temperature difference is the largest. For example, when a gas storage well has just finished producing gas and then injects natural gas, the excessive axial load is extremely likely to cause the tubing string to fail. Both SY / T 73730 and SY / T 6952-1 standards give the calculation method of the axial load caused by temperature changes. However, this calculation method mainly considers the longitudinal temperature gradient change along the well depth and does not consider the radial temperature change. To reduce the axial load caused by this temperature effect, an injection-production balance period is set during the injection-production operation of gas storage wells, and a soaking period is set during steam stimulation, hoping to make the wellbore temperature gradient change consistent with the formation temperature gradient change through the large cavity of the formation. However, the lengths of the injection-production balance period and the soaking period are only inferred based on production experience and numerical calculations, without real test basis. Especially, the current definition of the injection-production balance period of gas storage wells is not less than 15 days. However, due to the need for injection-production peak regulation, injection-production conversion may be required in 3 days. How much risk this brings to the wellbore safety urgently needs to be solved.

[0003] The main problems existing in the prior art are as follows: 1) By relying on geophysical logging instruments, the longitudinal temperature change (temperature gradient) of the wellbore along the well depth can be measured, but the radial temperature change between the wellbore and the formation cannot be tested; 2) Both the existing standards and the tubing string mechanics theory give the calculation method of the axial load caused by longitudinal temperature changes, but the radial temperature change is not considered. The main reason is that it is difficult to obtain the radial temperature change. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a wellbore temperature balance test device and a test method to obtain the radial change of injection-production temperature and the balance relationship over time, provide a test basis for reasonably setting the injection-production balance period, provide a theoretical verification basis for further reducing the tubing string axial load, and ensure the safe operation of the injection-production wellbore.

[0005] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0006] A wellbore temperature balance test device includes a base. An outer protection cylinder, a cylinder barrel, a cement ring, a casing, and a tubing are arranged on the upper end surface of the base along the same center line. One ends of the outer protection cylinder, the cylinder barrel, the cement ring, the casing, and the tubing are all connected to the upper end surface of the base. A heating rod is arranged inside the tubing, and the inner wall of the cement ring is attached to the outer wall of the casing. A first cover plate is provided at the top of the casing and the tubing, and a second cover plate is provided at the top of the outer protection cylinder and the cylinder barrel. An oil tubing temperature and pressure control valve communicating with the tubing, a casing temperature and pressure control valve and a casing outflow valve communicating with the casing are arranged on the first cover plate. An outer protection cylinder injection valve and an outer protection cylinder outflow valve communicating with the outer protection cylinder, and a cylinder barrel injection valve and a cylinder barrel outflow valve communicating with the cylinder barrel are arranged on the second cover plate. Temperature sensors are arranged on the inner wall of the outer protection cylinder, the inner wall of the cylinder barrel, the outer wall of the cement ring, the inner and outer walls of the casing, and the inner and outer walls of the tubing.

[0007] Further, the outer diameter of the outer protection cylinder is much larger than the outer diameter of the cylinder barrel, the outer diameter of the cylinder barrel is much larger than the outer diameter of the casing, and the outer diameter of the casing is larger than the outer diameter of the tubing.

[0008] Further, the outer diameter of the tubing is 60 mm to 139.7 mm, the outer diameter of the casing is 177.8 mm to 245 mm, the outer diameter of the cylinder barrel is not less than 500 mm, and the outer diameter of the outer protection cylinder is not less than 1000 mm.

[0009] Further, the wall thickness of the cement ring is not less than 20 mm, the wall thickness of the cylinder barrel is 2 mm to 5 mm, and the wall thickness of the outer protection cylinder is not less than 8 mm.

[0010] Further, the heights of the casing and the tubing are the same, the heights of the outer protection cylinder and the cylinder barrel are the same, and the height of the cement ring is less than the height of the casing and greater than the height of the cylinder barrel.

[0011] Further, the heights of the casing and the tubing are 600 mm to 1500 mm, and the heights of the outer protection cylinder and the cylinder barrel are 500 mm to 600 mm.

[0012] Further, flow meters and thermometers are arranged on the cylinder barrel injection valve, the cylinder barrel outflow valve, the outer protection cylinder injection valve, the outer protection cylinder outflow valve, and the casing outflow valve.

[0013] Furthermore, the extending end of the outer protection cylinder injection valve is close to the bottom of the outer protection cylinder, and the extending end of the outer protection cylinder outflow valve is close to the top of the outer protection cylinder; the extending end of the cylinder barrel injection valve is close to the bottom of the cylinder barrel, and the extending end of the cylinder barrel outflow valve is close to the top of the cylinder barrel; the extending end of the casing temperature and pressure control valve is close to the bottom of the casing, and the extending end of the casing outflow valve is close to the top of the casing; the extending end of the tubing temperature and pressure control valve is close to the top of the tubing.

[0014] A wellbore temperature balance test method, which uses the described test device for testing, includes:

[0015] Step 1: Open the outer protection cylinder injection valve and inject water with a temperature of T4 into the outer protection cylinder until the temperature and flow rate of the water flowing out of the outer protection cylinder outflow valve are the same as those during injection. Keep the outer protection cylinder injection valve and the outer protection cylinder outflow valve open to make the water circulate and ensure that the temperature T4 remains unchanged.

[0016] Step 2: Open the cylinder barrel injection valve and inject water with a temperature of T3 into the cylinder barrel until the temperature and flow rate of the water flowing out of the cylinder barrel outflow valve are the same as those during injection. Keep the cylinder barrel injection valve and the cylinder barrel outflow valve open to make the water circulate and ensure that the temperature T3 remains unchanged.

[0017] Step 3: Open the casing temperature and pressure control valve, fill the casing with annulus protection fluid, close the casing outflow valve, and apply a set pressure. Record the temperature T2 and pressure P2 inside the casing at this time.

[0018] Step 4: Open the tubing temperature and pressure control valve, inject fluid into the tubing, apply a set pressure, control the heating rod to heat to the temperature T1, and record the temperature T1 and pressure P1 inside the tubing at this time.

[0019] Step 5: Injection and production process test. Keep the temperature T1 and pressure P1 inside the tubing unchanged, and record the change of temperature at each point over time through the temperature sensor; close the cylinder barrel injection valve and the cylinder barrel outflow valve, and record the change of temperature at each point over time through the temperature sensor; close the cylinder barrel injection valve, the cylinder barrel outflow valve, the outer protection cylinder injection valve, and the outer protection cylinder outflow valve, and record the change of temperature at each point over time through the temperature sensor; analyze the radial propagation speed of temperature during the injection and production of fluid to obtain the temperature gradient change.

[0020] Step 6: Shut-in production test. Close the heating rod and the tubing temperature and pressure control valve, record the changes in the temperature T1 and pressure P1 inside the tubing, and record the temperature changes at each point over time through the temperature sensor; close the cylinder injection valve and the cylinder outflow valve, and record the temperature changes at each point over time through the temperature sensor; close the cylinder injection valve, the cylinder outflow valve, the outer protection cylinder injection valve, and the outer protection cylinder outflow valve, and record the temperature changes at each point over time through the temperature sensor; analyze the radial propagation speed of the temperature in the wellbore after shut-in and obtain the temperature equilibrium time.

[0021] Further, when the heating temperature of the heating rod is lower than 100 °C, inject water into the tubing; when the heating temperature of the heating rod is 100 °C to 300 °C, inject hydraulic oil into the tubing; when the heating temperature of the heating rod is higher than 300 °C, inject nitrogen into the tubing.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: A wellbore temperature balance test device provided by the present invention, when in use, open the outer protection cylinder injection valve, inject water with a temperature of T4 into the outer protection cylinder until the temperature and flow rate of the water flowing out from the outer protection cylinder outflow valve are the same as those during injection. The outer protection cylinder injection valve and the outer protection cylinder outflow valve remain open to keep the water circulating and ensure that the temperature T4 remains unchanged. Open the cylinder injection valve, inject water with a temperature of T3 into the cylinder until the temperature and flow rate of the water flowing out from the cylinder outflow valve are the same as those during injection. The cylinder injection valve and the cylinder outflow valve remain open to keep the water circulating and ensure that the temperature T3 remains unchanged. Open the casing temperature and pressure control valve, fill the annulus protection fluid into the casing, close the casing outflow valve, and apply a set pressure, and record the temperature T2 and pressure P2 inside the casing at this time. Open the tubing temperature and pressure control valve, inject fluid into the tubing, apply a set pressure, control the heating rod to heat to the temperature T1, and record the temperature T1 and pressure P1 inside the tubing at this time. When conducting the injection and production process test, keep the temperature T1 and pressure P1 inside the tubing unchanged, and record the change of the temperature at each point over time through the temperature sensor. Close the cylinder injection valve and the cylinder outflow valve, and record the change of the temperature at each point over time through the temperature sensor. Close the cylinder injection valve, the cylinder outflow valve, the outer protection cylinder injection valve, and the outer protection cylinder outflow valve, and record the change of the temperature at each point over time through the temperature sensor. Analyze the radial propagation speed of the temperature during the injection and production of the fluid to obtain the temperature gradient change. When conducting the shut-in and production suspension test, turn off the heating rod and the tubing temperature and pressure control valve, record the change of the temperature T1 and pressure P1 inside the tubing, and record the change of the temperature at each point over time through the temperature sensor. Close the cylinder injection valve and the cylinder outflow valve, and record the change of the temperature at each point over time through the temperature sensor. Close the cylinder injection valve, the cylinder outflow valve, the outer protection cylinder injection valve, and the outer protection cylinder outflow valve, and record the change of the temperature at each point over time through the temperature sensor. Analyze the radial propagation speed of the temperature inside the wellbore after shut-in to obtain the temperature balance time. It can be seen that the present invention can obtain the radial change of the injection and production temperature and the balance relationship over time, provide an experimental basis for reasonably setting the injection and production balance period, provide a theoretical verification basis for further reducing the axial load of the pipe string, and ensure the safe operation of the injection and production wellbore. The present invention can simulate the radial distribution and propagation time of the wellbore temperature under working conditions such as the injection and production operation of a gas storage reservoir and the steam stimulation of heavy oil thermal recovery. It not only provides an experimental basis for the injection and production balance period of the gas storage reservoir and the soaking period of steam stimulation, but also provides a calculation basis for accurately determining the temperature load distribution of the pipe string, and ultimately provides technical support for realizing the safety production operation control in the oilfield site.

[0023] Furthermore, the outer diameter of the outer protection cylinder of the present invention is much larger than the outer diameter of the cylinder, the outer diameter of the cylinder is much larger than the outer diameter of the casing, and the outer diameter of the casing is larger than the outer diameter of the tubing, which is beneficial to distinguish the far formation environment, the near formation environment, and the wellbore environment, and can deeply analyze the temperature change relationship among the far formation, the near formation, and the wellbore.

[0024] Furthermore, the outer diameter of the tubing of the present invention is 60 mm to 139.7 mm, the outer diameter of the casing is 177.8 mm to 245 mm, the outer diameter of the cylinder barrel is not less than 500 mm, and the outer diameter of the outer protection cylinder is not less than 1000 mm, which can truly simulate the conditions of the downhole tubing and casing, while reducing the floor area of indoor experiments and facilitating the conduct of tests.

[0025] Furthermore, the wall thickness of the cement sheath of the present invention is not less than 20 mm, the wall thickness of the cylinder barrel is 2 mm to 5 mm, and the wall thickness of the outer protection cylinder is not less than 8 mm, which can simulate the actual cementation thickness downhole. The use of a thin-walled cylinder barrel is beneficial to the temperature exchange between the near formation and the far formation, and the thick-walled outer protection cylinder ensures the pressure-bearing capacity.

[0026] Furthermore, the heights of the casing and the tubing of the present invention are the same, the heights of the outer protection cylinder and the cylinder barrel are the same, and the height of the cement sheath is less than the height of the casing and greater than the height of the cylinder barrel, which is convenient for controlling the formation of a high-temperature and high-pressure environment in the wellbore, beneficial to the measurement of temperature propagation, and prevents excessive measurement errors.

[0027] Furthermore, the heights of the casing and the tubing of the present invention are 600 mm to 1500 mm, and the heights of the outer protection cylinder and the cylinder barrel are 500 mm to 600 mm. Compared with a well depth of thousands of meters, based on this micro-element segment design method, it is beneficial to improve the calculation accuracy of the temperature propagation along the entire well depth.

[0028] Furthermore, flow meters and thermometers are provided on the cylinder barrel injection valve, the cylinder barrel outflow valve, the outer protection cylinder injection valve, the outer protection cylinder outflow valve, and the casing outflow valve of the present invention, which is convenient for collecting the flow rate and temperature inside the cylinder barrel, the outer protection cylinder, and the casing.

[0029] Furthermore, the extending end of the outer protection cylinder injection valve is close to the bottom of the outer protection cylinder, and the extending end of the outer protection cylinder outflow valve is close to the top of the outer protection cylinder; the extending end of the cylinder barrel injection valve is close to the bottom of the cylinder barrel, and the extending end of the cylinder barrel outflow valve is close to the top of the cylinder barrel; the extending end of the casing temperature and pressure control valve is close to the bottom of the casing, and the extending end of the casing outflow valve is close to the top of the casing; the extending end of the tubing temperature and pressure control valve is close to the top of the tubing. With such a design, injecting liquid at the bottom and discharging liquid at the top can quickly achieve an initial temperature balance within the entire corresponding space.

[0030] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, is described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the specific embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic diagram of a wellbore temperature balance test device of the present invention.

[0033] In the figure: 1 - tubing temperature and pressure control valve; 2 - casing temperature and pressure control valve; 3 - cylinder injection valve; 4 - outer protection cylinder injection valve; 5 - outer protection cylinder; 6 - cylinder; 7 - cement sheath; 8 - casing; 9 - tubing; 10 - heating rod; 11 - temperature sensor; 12 - base; 13 - second cover plate; 14 - outer protection cylinder outflow valve; 15 - cylinder outflow valve; 16 - casing outflow valve; 17 - first cover plate. Specific embodiments

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0035] Based on the problems of large temperature difference changes and excessive pipe string axial loads during the downhole injection-production conversion process, the present invention proposes a wellbore temperature balance test device. The wellbore temperature balance test device of the present invention is mainly used for wellbore - formation system temperature balance tests, obtaining the radial temperature transfer relationships of tubing, casing, cement, formation, etc., establishing different temperature exchange time relationships, determining the radial temperature balance time, and further establishing the injection-production balance period. The wellbore temperature balance test device of the present invention consists of three parts: a wellbore system, a near - formation system, and a far - formation system. Among them, the wellbore system mainly includes tubing, heating rods, casing, and cement sheath; the near - formation system is mainly a cylinder filled with hydraulic oil; the far - formation system is mainly an outer protection cylinder filled with hydraulic oil or water.

[0036] As a specific embodiment of the present invention, as Figure 1 shown, a wellbore temperature balance test device includes a base 12. An outer protection cylinder 5, a cylinder 6, a cement sheath 7, a casing 8, and a tubing 9 are arranged on the upper end surface of the base 12 along the same center line. One ends of the outer protection cylinder 5, the cylinder 6, the cement sheath 7, the casing 8, and the tubing 9 are all connected to the upper end surface of the base 12. Preferably, for convenient connection, the base 12 is selected as a flange.

[0037] Specifically, asFigure 1 As shown, the outer diameter of the outer protective cylinder 5 is much larger than that of the cylinder barrel 6, which is much larger than that of the casing 8. The outer diameter of the casing 8 is larger than that of the oil pipe 9, and the inner wall of the cement sheath 7 is attached to the outer wall of the casing 8. Preferably, the outer diameter of the oil pipe 9 is 60 mm to 139.7 mm, the outer diameter of the casing 8 is 177.8 mm to 245 mm, the wall thickness of the cement sheath 7 is no less than 20 mm, the outer diameter of the cylinder barrel 6 is no less than 500 mm, the wall thickness of the cylinder barrel 6 is 2 mm to 5 mm, the outer diameter of the outer protective cylinder 5 is no less than 1000 mm, and the wall thickness of the outer protective cylinder 5 is no less than 8 mm. The casing 8 and the oil pipe 9 are of the same height, and the outer protective cylinder 5 and the cylinder barrel 6 are of the same height. The height of the cement sheath 7 is less than that of the casing 8 but greater than that of the cylinder barrel 6. Preferably, the height of the casing 8 and the oil pipe 9 is 600 mm to 1500 mm, and the height of the outer protective cylinder 5 and the cylinder barrel 6 is 500 mm to 600 mm.

[0038] like Figure 1 As shown, a heating rod 10 is provided in the oil pipe 9, which is fixed on the base 12 and located at the center line of the oil pipe 9. A first cover plate 17 is installed on the top of the casing 8 and the oil pipe 9. Preferably, the first cover plate 17 is a flange. The oil pipe temperature and pressure control valve 1 connected to the oil pipe 9, as well as the casing temperature and pressure control valve 2 and the casing outflow valve 16 connected to the casing 8 are installed on the first cover plate 17. Preferably, the insertion end of the oil pipe temperature and pressure control valve 1 is close to the top of the oil pipe 9, the insertion end of the casing temperature and pressure control valve 2 is close to the bottom of the casing 8, and the insertion end of the casing outflow valve 16 is close to the top of the casing 8. A second cover plate 13 is installed on the top of the outer protective cylinder 5 and the cylinder barrel 6. The outer protective cylinder injection valve 4 and the outer protective cylinder outflow valve 14 connected to the outer protective cylinder 5, as well as the cylinder barrel injection valve 3 and the cylinder barrel outflow valve 15 connected to the cylinder barrel 6 are installed on the second cover plate 13. Preferably, the outer protective cylinder injection valve 4 extends into the bottom of the outer protective cylinder 5, and the outer protective cylinder outflow valve 14 extends into the top of the outer protective cylinder 5; the cylinder barrel injection valve 3 extends into the bottom of the cylinder barrel 6, and the cylinder barrel outflow valve 15 extends into the top of the cylinder barrel 6. In this embodiment, the cylinder barrel injection valve 3, the cylinder barrel outflow valve 15, the outer protective cylinder injection valve 4, the outer protective cylinder outflow valve 14, and the sleeve outflow valve 16 are all provided with flow meters and thermometers.

[0039] like Figure 1 As shown, temperature sensors 11 are installed on the inner wall of outer protective cylinder 5, the inner wall of cylinder barrel 6, the outer wall of cement sheath 7, the inner and outer walls of casing 8, and the inner and outer walls of oil pipe 9. Specifically, as needed, temperature sensors 11 may be arranged at a single point or multiple points along the circumference and depth of outer protective cylinder 5, cylinder barrel 6, cement sheath 7, casing 8, and oil pipe 9.

[0040] The present invention provides a wellbore temperature balance test method. The test preparations required before the test are as follows:

[0041] ①Install the heating rod 10 on the base 12, and then install the oil pipe 9 on the base 12;

[0042] ②After pouring a cement ring 7 outside the casing 8, install it on the base 12;

[0043] ③Install the cylinder barrel 6 on the base 12;

[0044] ④Install the outer protection cylinder 5 on the base 12;

[0045] ⑤Arrange the temperature sensors 11 on the inner and outer walls of the oil pipe 9, the inner and outer walls of the casing 8, the outer wall of the cement ring 7, the inner wall of the cylinder barrel 6 and the inner wall of the outer protection cylinder 5 respectively. The temperature sensors 11 can be arranged at single or multiple points along the circumferential and depth directions according to actual needs;

[0046] ⑥Install the first cover plate 17 and connect it to the oil pipe 9 and the casing 8;

[0047] ⑦Seal the second cover plate 13 and take temperature protection measures around the device to prevent the internal temperature change from being affected by the external environment;

[0048] ⑧Nitrogen, water or oil can be injected into the oil pipe 9 through the oil pipe temperature and pressure control valve 1. Annular protection fluid can be injected into the annulus between the oil pipe 9 and the casing 8 (i.e., inside the casing 8) through the casing temperature and pressure control valve 2. The oil pipe 9, the casing 8, the cement ring 7 and the fluid therein together form a wellbore system;

[0049] ⑨Water or hydraulic oil can be injected into the cylinder barrel 6 through the cylinder barrel injection valve 3. The cylinder barrel 6 and the fluid therein form a near formation system;

[0050] ⑩Water can be injected into the outer protection cylinder 5 through the outer protection cylinder injection valve 4. The outer protection cylinder 5 and the fluid therein form a far formation system.

[0051] See Figure 1 as shown, a wellbore temperature balance test method of the present invention specifically includes the following steps:

[0052] Step 1: Open the outer protection cylinder injection valve 4 and inject water with a temperature of T4 into the outer protection cylinder 5 until the temperature and flow rate of the water flowing out from the outer protection cylinder outflow valve 14 are the same as those during injection. The outer protection cylinder injection valve 4 and the outer protection cylinder outflow valve 14 remain open to keep the water circulating and ensure that the temperature T4 remains unchanged.

[0053] Step 2: Open the cylinder barrel injection valve 3 and inject water with a temperature of T3 into the cylinder barrel 6 until the temperature and flow rate of the water flowing out from the cylinder barrel outflow valve 15 are the same as those during injection. The cylinder barrel injection valve 3 and the cylinder barrel outflow valve 15 remain open to keep the water circulating and ensure that the temperature T3 remains unchanged.

[0054] Step 3: Open the casing temperature and pressure control valve 2, fill the annulus protection fluid into the casing 8, close the casing outflow valve 16, and apply the set pressure. Record the temperature T2 and pressure P2 inside the casing 8 at this time.

[0055] Step 4: Open the tubing temperature and pressure control valve 1, inject fluid into the tubing 9, and apply the set pressure. Control the heating rod 10 to heat to the temperature T1, and record the temperature T1 and pressure P1 inside the tubing 9 at this time;

[0056] Specifically, when the heating temperature of the heating rod 10 is lower than 100 °C, water is injected into the tubing 9; when the heating temperature of the heating rod 10 is 100 °C - 300 °C, hydraulic oil is injected into the tubing 9; when the heating temperature of the heating rod 10 is higher than 300 °C, nitrogen is injected into the tubing 9.

[0057] Step 5: Injection-production process test. Keep the temperature T1 and pressure P1 inside the tubing 9 unchanged, and record the change of temperature at each point over time through the temperature sensor 11; close the cylinder injection valve 3 and the cylinder outflow valve 15, and record the change of temperature at each point over time through the temperature sensor 11; close the cylinder injection valve 3, the cylinder outflow valve 15, the outer protection cylinder injection valve 4 and the outer protection cylinder outflow valve 14, and record the change of temperature at each point over time through the temperature sensor 11; analyze the radial propagation speed of temperature during the injection and production of fluids, and obtain the temperature gradient change.

[0058] Step 6: Shut-in production test. Close the heating rod 10 and the tubing temperature and pressure control valve 1, record the change of temperature T1 and pressure P1 inside the tubing 9, and record the change of temperature at each point over time through the temperature sensor 11; close the cylinder injection valve 3 and the cylinder outflow valve 15, and record the change of temperature at each point over time through the temperature sensor 11; close the cylinder injection valve 3, the cylinder outflow valve 15, the outer protection cylinder injection valve 4 and the outer protection cylinder outflow valve 14, and record the change of temperature at each point over time through the temperature sensor 11; analyze the radial propagation speed of temperature in the wellbore after shut-in, and obtain the temperature equilibrium time.

[0059] Step 7: Change the temperature and pressure inside the tubing 9, and repeat Step 5 and Step 6.

[0060] Through the tests under different temperatures inside the tubing, obtain the radial distribution and change of the wellbore temperature at different well depths, and finally obtain the temperature equilibrium period of the entire wellbore.

[0061] Finally, it should be noted that the above-described embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any person skilled in the technical field of the present invention can still modify the technical solutions described in the foregoing embodiments, or can easily conceive of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A wellbore temperature balance test device, characterized in that: The invention comprises a base (12), wherein the upper end surface of the base (12) is provided with an outer protective cylinder (5), a cylinder barrel (6), a cement ring (7), a casing (8) and an oil pipe (9) on the same center line, wherein one end of the outer protective cylinder (5), the cylinder barrel (6), the cement ring (7), the casing (8) and the oil pipe (9) are all connected to the upper end surface of the base (12), a heating rod (10) is provided in the oil pipe (9), and the inner wall of the cement ring (7) is attached to the outer wall of the casing (8); a first cover plate (17) is provided on the top of the casing (8) and the oil pipe (9), and a second cover plate (17) is provided on the top of the outer protective cylinder (5) and the cylinder barrel (6). 3); the first cover plate (17) is provided with an oil pipe temperature and pressure control valve (1) in communication with the oil pipe (9), and a casing temperature and pressure control valve (2) and a casing outflow valve (16) in communication with the casing (8); the second cover plate (13) is provided with an outer protection cylinder injection valve (4) and an outer protection cylinder outflow valve (14) in communication with the outer protection cylinder (5), and a cylinder injection valve (3) and a cylinder outflow valve (15) in communication with the cylinder (6); the inner wall of the outer protection cylinder (5), the inner wall of the cylinder (6), the outer wall of the cement ring (7), the inner and outer walls of the casing (8), and the inner and outer walls of the oil pipe (9) are provided with temperature sensors (11).

2. A wellbore temperature balance test device according to claim 1, characterized in that: The outer diameter of the outer protective cylinder (5) is much larger than the outer diameter of the cylinder barrel (6), the outer diameter of the cylinder barrel (6) is much larger than the outer diameter of the sleeve (8), and the outer diameter of the sleeve (8) is larger than the outer diameter of the oil pipe (9).

3. A wellbore temperature balance test device according to claim 2, characterized in that: The outer diameter of the oil pipe (9) is 60 mm to 139.7 mm, the outer diameter of the sleeve (8) is 177.8 mm to 245 mm, the outer diameter of the cylinder (6) is not less than 500 mm, and the outer diameter of the outer protective cylinder (5) is not less than 1000 mm.

4. A wellbore temperature balance test device according to claim 3, characterized in that: The wall thickness of the cement ring (7) is not less than 20 mm, the wall thickness of the cylinder barrel (6) is 2 mm to 5 mm, and the wall thickness of the outer protective cylinder (5) is not less than 8 mm.

5. A wellbore temperature balance test device according to claim 1, characterized in that: The casing (8) and the oil pipe (9) have the same height, the outer protective cylinder (5) and the cylinder barrel (6) have the same height, and the height of the cement ring (7) is smaller than the height of the casing (8) and larger than the height of the cylinder barrel (6).

6. A wellbore temperature balance test device according to claim 5, characterized in that: The height of the sleeve (8) and the oil pipe (9) is 600 mm to 1500 mm, and the height of the outer protective cylinder (5) and the cylinder barrel (6) is 500 mm to 600 mm.

7. A wellbore temperature balance test device according to claim 1, characterized in that: The cylinder injection valve (3), the cylinder outflow valve (15), the outer protection cylinder injection valve (4), the outer protection cylinder outflow valve (14) and the sleeve outflow valve (16) are all provided with flow meters and thermometers.

8. A wellbore temperature balance test device according to claim 1, characterized in that: The insertion end of the outer protection cylinder injection valve (4) is close to the bottom of the outer protection cylinder (5), and the insertion end of the outer protection cylinder outflow valve (14) is close to the top of the outer protection cylinder (5); the insertion end of the cylinder barrel injection valve (3) is close to the bottom of the cylinder barrel (6), and the insertion end of the cylinder barrel outflow valve (15) is close to the top of the cylinder barrel (6); the insertion end of the casing temperature and pressure control valve (2) is close to the bottom of the casing (8), and the insertion end of the casing outflow valve (16) is close to the top of the casing (8); the insertion end of the oil pipe temperature and pressure control valve (1) is close to the top of the oil pipe (9).

9. A wellbore temperature balance test method, characterized in that: The test device according to any one of claims 1 to 8 is used to conduct a test, comprising: Step 1: Open the outer protection cylinder injection valve (4) and inject water at a temperature of T4 into the outer protection cylinder (5) until the temperature and flow rate of the water flowing out of the outer protection cylinder outflow valve (14) are consistent with those during injection. The outer protection cylinder injection valve (4) and the outer protection cylinder outflow valve (14) are kept open to keep the water circulating and ensure that the temperature T4 remains unchanged. Step 2: Open the cylinder injection valve (3) and inject water at a temperature of T3 into the cylinder (6) until the temperature and flow rate of the water flowing out of the cylinder outflow valve (15) are consistent with those during injection. The cylinder injection valve (3) and the cylinder outflow valve (15) are kept open to keep the water circulating and ensure that the temperature T3 remains unchanged. Step 3: Open the casing temperature and pressure control valve (2), fill the casing (8) with annular protection fluid, close the casing outflow valve (16), apply the set pressure, and record the temperature T2 and pressure P2 in the casing (8) at this time; Step 4: Open the oil pipe temperature and pressure control valve (1), inject fluid into the oil pipe (9), apply a set pressure, control the heating rod (10) to heat to temperature T1, and record the temperature T1 and pressure P1 in the oil pipe (9) at this time; Step 5, injection and production process test, keep the temperature T1 and pressure P1 in the oil pipe (9) unchanged, and record the temperature change of each point over time through the temperature sensor (11); close the cylinder injection valve (3) and the cylinder outflow valve (15), and record the temperature change of each point over time through the temperature sensor (11); close the cylinder injection valve (3), the cylinder outflow valve (15), the outer protection cylinder injection valve (4) and the outer protection cylinder outflow valve (14), and record the temperature change of each point over time through the temperature sensor (11); analyze the radial propagation velocity of the temperature during the injection and production process of the fluid to obtain the temperature gradient change; Step 6: shut-in and production stoppage test: close the heating rod (10) and the oil pipe temperature and pressure control valve (1), record the changes in temperature T1 and pressure P1 in the oil pipe (9), and record the changes in temperature at each point over time through the temperature sensor (11); close the cylinder injection valve (3) and the cylinder outflow valve (15), and record the changes in temperature at each point over time through the temperature sensor (11); close the cylinder injection valve (3), the cylinder outflow valve (15), the outer protection cylinder injection valve (4) and the outer protection cylinder outflow valve (14), and record the changes in temperature at each point over time through the temperature sensor (11); analyze the radial propagation velocity of the temperature in the wellbore after shutting in, and obtain the temperature equilibrium time.

10. A wellbore temperature balance test method according to claim 9, characterized in that: When the heating temperature of the heating rod (10) is lower than 100°C, water is injected into the oil pipe (9); when the heating temperature of the heating rod (10) is between 100°C and 300°C, hydraulic oil is injected into the oil pipe (9); when the heating temperature of the heating rod (10) is higher than 300°C, nitrogen is injected into the oil pipe (9).

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