Heat exchange and test method for deep geothermal development shaft

Abstract

The invention discloses a heat exchange and test method for a deep geothermal development shaft. The problem that an existing geothermal development well cannot obtain related outlet water temperature, outlet flow and water temperature data in a shaft in different periods is mainly solved. The method is characterized by comprising the following steps: S1, fixing a temperature measuring optical fiber on an optical fiber carrying tubular column, and tripping into the bottom of a geothermal development well along with the optical fiber carrying tubular column; s2, setting a temperature measuring point of the temperature measuring optical fiber; s3, temperature data of the initial stage, the heat collection stage and the temperature field recovery stage are collected; and S4, the heat exchange power of the geothermal development well is calculated according to the collected temperature data, the temperature field recovery condition is judged, and when the temperature of the temperature field recovery stage of the corresponding temperature measurement point is equal to the temperature of the initial stage, the temperature field is completely recovered. According to the heat exchange and test method for the deep geothermal development shaft, different well section temperatures, outlet temperatures and outlet flows of a heat collection stage and a heat collection stopping stage can be recorded, and a basis is provided for large-scale development and well position deployment of geothermal development wells.

Description

Technical Field

[0001] The invention relates to the field of geothermal energy development, in particular to a heat exchange test method for a deep geothermal development wellbore. Background Art

[0002] Deep geothermal development wells refer to geothermal development wells with a vertical depth of more than 2500m. Wellbore heat exchange technology is the main development method for deep geothermal energy development, including U-shaped well and vertical wellbore heat exchange, and the heat exchange medium is mainly water; that is, U-shaped wells or vertical wells are drilled to the deep heat extraction target layer, and then circulating water is injected into the well, and the wellbore is heated to extract geothermal energy. Wellbore heat exchange generally includes three stages: the initial stage, the heat extraction stage, and the heat extraction stop stage during the temperature field recovery period; in these three stages, heat tests are used to obtain relevant outlet water temperature, outlet flow rate, and water temperature data at different times in the wellbore, providing a basis for large-scale development and geothermal development well location deployment. However, there is no such heat test method for current geothermal development wells. Summary of the invention

[0003] In order to overcome the problem that existing geothermal development wells are unable to obtain relevant outlet water temperature, outlet flow rate, and water temperature data at different periods in the wellbore, the present invention provides a deep geothermal development wellbore heat exchange test method, which can record the temperatures, outlet temperatures and outlet flow rates of different well sections in the initial stage, heat production stage and temperature field recovery stage, providing a basis for large-scale development and well site deployment of geothermal development wells.

[0004] The technical solution of the present invention is: a deep geothermal development wellbore heat exchange test method, comprising:

[0005] S1. Fix the temperature measuring optical fiber on the optical fiber carrying pipe string and lower it into the bottom of the geothermal development well along with the optical fiber carrying pipe string;

[0006] S2. Setting the temperature measuring point of the temperature measuring optical fiber;

[0007] S3, collecting data, respectively collecting temperature data in the initial stage, heat collection stage, and temperature field recovery stage;

[0008] S4. Calculate the heat exchange power of the geothermal development well based on the collected temperature data and determine the temperature field recovery status. When the temperature of the temperature field recovery stage at the corresponding temperature measuring point is equal to the temperature of the initial stage, the temperature field is fully recovered.

[0009] The geothermal development well is a U-shaped well, which includes a vertical well section and a horizontal well section, wherein the temperature measuring optical fiber in the vertical well section is fixed on the sucker rod and lowered to the bottom of the well with the sucker rod, and the temperature measuring optical fiber in the horizontal well section is prefabricated in the continuous oil pipe and lowered to the bottom of the well with the continuous oil pipe; wherein the spacing between the temperature measuring points in the vertical well section is not greater than 20m, and the spacing between the temperature measuring points in the horizontal well section is not greater than 10m.

[0010] Further, when the geothermal development well is a U-shaped well, step S3 includes:

[0011] S3.1. Collect the temperature of each temperature measuring point in the initial stage. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1, Th2...Th from the wellhead to the bottom of the well. n The temperatures of the measuring points in the vertical wellbore are recorded as Ts1, Ts2, ..., Ts from the wellhead to the bottom of the well. n ;

[0012] S3.2, collect the inlet flow rate Q and the temperature of each temperature measuring point during the heat extraction stage, where the temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1', Th2'...Th from the wellhead to the bottom of the well. n ', the temperature of the measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1', Ts2'...Ts n ';

[0013] S3.3. Collect the temperature of each temperature measuring point during the temperature field recovery stage. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1", Th2"...Th from the wellhead to the bottom of the well. n ", the temperature of the temperature measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1", Ts2"...Ts n ".

[0014] Further, in step S4, heat exchange power W = Q × Δt / 0.86, where W is heat exchange power (kW); Q is flow rate (m 3 / h); Δt: Ts1'-Th1'.

[0015] Further, in step S4, during the temperature field recovery phase, when Th n -Th n "≤2℃, the temperature field is judged to be fully restored.

[0016] The geothermal development well is a vertical well, and the temperature measuring optical fiber is bundled on the heat exchange pipe string and lowered into the bottom of the well along with the heat exchange pipe string, wherein the distance between the temperature measuring points is no more than 20m.

[0017] Further, when the geothermal development well is a vertical well, step S3 includes:

[0018] S3.1. Collect the temperature of each measuring point in the initial stage, and record it as T1, T2, ... T from the wellhead to the bottom of the well. n , where T1 is the wellbore inlet temperature, T n is the temperature of the lowest measuring point;

[0019] S3.2. Collect the inlet flow rate Q and the temperature of each temperature measuring point during the heat collection stage. The cold water inlet temperature is measured by the temperature measuring point on the temperature measuring optical fiber, which is recorded as T1'. The hot water outlet temperature is measured by the thermometer at the outlet of the heat exchange column, which is recorded as T c ;

[0020] S3.3. Collect the temperature of each measuring point during the temperature field recovery stage. The temperature in the wellbore from the wellhead to the bottom of the well is recorded as T1", T2", ... T n ".

[0021] Further, in step S4, heat exchange power W = Q × Δt / 0.86, where W is heat exchange power (kW); Q is flow rate (m 3 / h); Δt: T c -T1'.

[0022] Further, in step S4, during the temperature field recovery phase, when T n -T n "≤2℃, the temperature field is judged to be fully restored.

[0023] Furthermore, the temperature collection frequency of the temperature measuring point is 1 time / 4 hours to 1 time / day.

[0024] The present invention has the following beneficial effects: by adopting the above-mentioned scheme and the heat exchange test method, the temperature changes of each section in the wellbore at each stage of heat exchange can be collected, the heat exchange power in different time periods of the heat production stage can be determined, and the recovery law of the temperature field of each section of the wellbore when the wellbore stops heat production can be intuitively studied; the influence radius of the heat exchange temperature field of U-shaped wells and vertical wells can be numerically simulated to provide a basis for the design of geothermal energy well networks for large-scale utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the present invention;

[0026] Figure 2 It is a schematic diagram of heat exchange in a U-shaped well;

[0027] Figure 3 It is a schematic diagram of vertical well heat exchange. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] Depend on Figure 1 As shown, a deep geothermal development wellbore heat exchange test method is described. Since geothermal development wells include U-shaped wells and vertical wells, for the convenience of description, the U-shaped wells and vertical wells are described separately here.

[0030] When the geothermal development well is a U-shaped well, the deep geothermal development wellbore heat exchange test method includes the following steps:

[0031] S1. Select a suitable type of temperature measuring optical fiber, fix one temperature measuring optical fiber on the sucker rod, and lower it into the bottom of the U-shaped vertical well with the sucker rod. For example, if the horizontal well completion casing is φ177.8mm, you can choose steel grade CT80φ50.08mm×4mm type continuous tubing and DOSC-150℃-180Mpa-316L-8.0mm-2MM-2L type temperature measuring optical fiber; prefabricate another temperature measuring optical fiber in the continuous tubing and lower it into the bottom of the horizontal well of the U-shaped well with the continuous tubing. If the vertical well completion casing is φ177.8mm, you can choose φ19mm type sucker rod and DOSC-150℃-180Mpa-316L-8.0mm-2MM-2L type temperature measuring optical fiber, such as Figure 2 .

[0032] S2. Set the temperature measuring points of the temperature measuring optical fiber. In the vertical well section of the U-shaped well, the distance between the temperature measuring points is no more than 20m. In the horizontal well section of the U-shaped well, the distance between the temperature measuring points is no more than 10m.

[0033] S3, collect data, collect temperature data in the initial stage, heat collection stage, and temperature field recovery stage, and the frequency of temperature collection is once every 4 hours to once every day. Specifically:

[0034] S3.1. Collect the temperature of each measuring point in the initial stage before the heat exchange begins. In the horizontal wellbore that constitutes the U-shaped well, the temperature of the measuring points from the wellhead to the bottom of the well is recorded as Th1, Th2...Th n , where Th1 is the inlet temperature of the horizontal well section, Th n is the temperature of the last temperature measuring point in the horizontal well section; the temperature of the temperature measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1, Ts2...Ts n , where Ts n is the temperature of the measuring point at the lowest end of the vertical well section, and Ts1 is the outlet temperature of the vertical well section.

[0035] S3.2. Collect the inlet flow rate Q during the heat extraction stage and the temperature of each temperature measuring point during the heat exchange period. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1', Th2'...Th from the wellhead to the bottom of the well. n ', the temperature of the temperature measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1', Ts2'...Ts n '.

[0036] S3.3. Collect the temperature of each temperature measuring point in the temperature field recovery stage after a round of heat exchange. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1", Th2"...Th from the wellhead to the bottom of the well. n ", the temperature of the temperature measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1", Ts2"...Ts n ".

[0037] S4. In the heat production stage, the heat exchange power of the geothermal development well is calculated according to the temperature data collected in step S3, wherein the heat exchange power W = Q × Δt / 0.86, where W is the heat exchange power (kW); Q is the flow rate (m 3 / h); Δt: Ts1'-Th1'.

[0038] During the temperature field recovery phase, the temperature field recovery status is judged at any time. At a certain period of the temperature field recovery phase, the initial stage temperature data Th of the horizontal well section is compared. n And the temperature data Th in the temperature field recovery stage n ", when Th n -Th n "≤2℃, the temperature field is judged to be fully restored.

[0039] When the geothermal development well is a vertical well, the deep geothermal development wellbore heat exchange test method includes the following steps:

[0040] S1. Select the appropriate type of temperature measuring optical fiber, bundle the temperature measuring optical fiber on the heat exchange column, and lower it into the bottom of the vertical well with the heat exchange column. If the completion casing is φ139.7mm, you can choose N80 steel grade φ89mm×62mm insulation pipe as the heat exchange column, DOSC-150℃-180Mpa-316L-8.0mm-2MM-2L type temperature measuring optical fiber, such as Figure 3 .

[0041] S2. Set the temperature measuring points of the temperature measuring optical fiber. For vertical well heat exchange wells, the distance between the temperature measuring points should not exceed 20m.

[0042] S3, collect data, collect temperature data in the initial stage, heat collection stage, and temperature field recovery stage, and the frequency of temperature collection is once every 4 hours to once every day. Specifically:

[0043] S3.1. Collect the temperature of each measuring point in the initial stage, and record it as T1, T2, ... T from the wellhead to the bottom of the well. n , where T1 is the wellbore inlet temperature, T n is the temperature of the lowest measuring point;

[0044] S3.2. Collect the inlet flow rate Q and the temperature of each temperature measuring point during the heat collection stage. The cold water inlet temperature is measured by the temperature measuring point on the temperature measuring optical fiber, which is recorded as T1'. The hot water outlet temperature is measured by the thermometer at the outlet of the heat exchange column, which is recorded as T c ;

[0045] S3.3. Collect the temperature of each measuring point during the temperature field recovery stage. The temperature in the wellbore from the wellhead to the bottom of the well is recorded as T1", T2", ... T n ".

[0046] S4, the heat exchange power of the geothermal development well is calculated according to the temperature data collected in step S3, where the heat exchange power W = Q × Δt / 0.86, where W is the heat exchange power (kW); Q is the flow rate (m 3 / h); Δt: T c -T1'.

[0047] In the temperature field recovery stage, the temperature field recovery status is judged. At a certain period in the temperature field recovery stage, the initial stage temperature data T n And the temperature data T in the temperature field recovery stage n ", when T n -T n "≤2℃, the temperature field is judged to be fully restored.

[0048] Example 1: Thermal Test of CRR3-U1 Well Group

[0049] Well CRR3-U1 is a U-shaped well. The thermal test conditions of this well group are operation for half a year and temperature field recovery for half a year.

[0050] (1) Initial stage: record the temperature in the wellbore every 4 hours and record the temperature Th of the last temperature measuring point in the horizontal section before heat extraction operation n 123℃;

[0051] (2) Heat collection stage: record the inlet flow, operating time, temperature, record the outlet temperature and calculate the heat exchange power, record once every 4 hours, see Table 1 for details.

[0052] Table 1 U-type wellbore heat exchange test parameters

[0053]

[0054] Example of heat exchange power calculation: The heat exchange power calculated based on the last recorded data on the 180th day of operation of the well group is as follows:

[0055] Inlet flow rate Q = 40m 3 / h, inlet temperature Th1'=30℃, outlet temperature Ts1'=62℃, Δt=Ts1'-Th1'=32℃, then the power

[0056] W=Q×Δt / 0.86, at this time the operating power W=1488KW.

[0057] (3) Temperature field recovery stage: record the temperature of each temperature measuring point in the vertical well Ts1"~Ts n ", record the temperature of each temperature measuring point in the horizontal well Th1" ~ Th n ", admission is made every 4 hours;

[0058] Temperature field recovery judgment: The temperature field recovery period of this well group is half a year, and it recovers to the Th recorded in the first 4 hours on the 170th day. n " is 122℃, then Th n -Th n "=1℃≤2℃, then it is judged that the temperature field is fully restored.

[0059] Example 2: LS4 Well Thermal Test

[0060] Well LS4 is a vertical heat exchange well, and the thermal test conditions are heat production operation for half a year and temperature field recovery for half a year.

[0061] (1) Initial stage: record the temperature in the wellbore every 4 hours, and record the temperature Tn of the lowest temperature measuring point before heat extraction operation as 120°C;

[0062] (2) Heat collection stage: including inlet flow, operating time, temperature setting, outlet data collection and power calculation, which are collected every 4 hours. For details, see Table 2.

[0063] Table 2 Vertical well heat exchange parameter setting table

[0064]

[0065] Example of heat exchange power calculation: The heat exchange power calculated based on the last recorded data on the 180th day of operation of the well group is as follows:

[0066] Inlet flow rate Q = 15m 3 / h, inlet temperature T1'=30℃, outlet temperature T c =50℃,

[0067] Δt=T c -T1'=20℃

[0068] Calculation formula: W = Q × Δt / 0.86

[0069] At this time, the operating power W = 349KW

[0070] (3) Temperature field recovery stage: The temperature of each temperature measuring point in the temperature field recovery stage is collected. The temperature in the wellbore is recorded as T1", T2", ... Tn" from the wellhead to the bottom of the well, and the data is recorded every 4 hours;

[0071] Temperature field recovery judgment: The temperature field recovery period of the well is half a year. The temperature field recovery period is half a year. The Tn" recorded in the first 4 hours on the 160th day is 118℃, and Th n -Th n "=120℃-118℃=2℃, then it is judged that the temperature field is fully restored at this time.

Claims

1. A deep geothermal development wellbore heat exchange test method, characterized in that include: S1. Fix the temperature measuring optical fiber on the optical fiber carrying pipe string and lower it into the bottom of the geothermal development well along with the optical fiber carrying pipe string; S2. Setting the temperature measuring point of the temperature measuring optical fiber; S3, collecting data, respectively collecting temperature data in the initial stage, heat collection stage, and temperature field recovery stage; S4. Calculate the heat exchange power of the geothermal development well based on the collected temperature data and determine the temperature field recovery status. When the temperature of the temperature field recovery stage at the corresponding temperature measuring point is equal to the temperature of the initial stage, the temperature field is fully recovered.

2. The deep geothermal development wellbore heat exchange test method according to claim 1, characterized in that: The geothermal development well is a U-shaped well, which includes a vertical well section and a horizontal well section, wherein the temperature measuring optical fiber in the vertical well section is fixed on the sucker rod and lowered to the bottom of the well with the sucker rod, and the temperature measuring optical fiber in the horizontal well section is prefabricated in the continuous oil pipe and lowered to the bottom of the well with the continuous oil pipe; wherein the spacing between the temperature measuring points in the vertical well section is not greater than 20m, and the spacing between the temperature measuring points in the horizontal well section is not greater than 10m.

3. The deep geothermal development wellbore heat exchange test method according to claim 2, characterized in that: When the geothermal development well is a U-shaped well, step S3 includes: S3.

1. Collect the temperature of each temperature measuring point in the initial stage. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1, Th2...Th from the wellhead to the bottom of the well. n The temperatures of the measuring points in the vertical wellbore are recorded as Ts1, Ts2, ..., Ts from the wellhead to the bottom of the well. n ; S3.2, collect the inlet flow rate Q and the temperature of each temperature measuring point during the heat extraction stage, where the temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1', Th2'...Th from the wellhead to the bottom of the well. n ', the temperature of the measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1', Ts2'...Ts n '; S3.

3. Collect the temperature of each temperature measuring point during the temperature field recovery stage. The temperature of the temperature measuring points in the wellbore of the horizontal well that constitutes the U-shaped well is recorded as Th1", Th2"...Th from the wellhead to the bottom of the well. n ", the temperature of the temperature measuring points in the vertical wellbore from the wellhead to the bottom of the well is recorded as Ts1", Ts2"...Ts n ".

4. The deep geothermal development wellbore heat exchange test method according to claim 3, characterized in that: In step S4, heat exchange power W=Q×Δt / 0.86, where W is heat exchange power (kW); Q is flow rate (m 3 / h); Δt: Ts1'-Th1'.

5. The deep geothermal development wellbore heat exchange test method according to claim 4, characterized in that: In step S4, during the temperature field recovery phase, when Th n -Th n "≤2℃, the temperature field is judged to be fully restored.

6. The deep geothermal development wellbore heat exchange test method according to claim 1, characterized in that: The geothermal development well is a vertical well, and the temperature measuring optical fiber is bundled on the heat exchange pipe string and lowered into the bottom of the well along with the heat exchange pipe string, wherein the distance between the temperature measuring points is no more than 20m.

7. The deep geothermal development wellbore heat exchange test method according to claim 6, characterized in that: When the geothermal development well is a vertical well, step S3 includes: S3.

1. Collect the temperature of each measuring point in the initial stage, and record it as T1, T2, ... T from the wellhead to the bottom of the well. n , where T1 is the wellbore inlet temperature, T n is the temperature of the lowest measuring point; S3.

2. Collect the inlet flow rate Q and the temperature of each temperature measuring point during the heat collection stage. The cold water inlet temperature is measured by the temperature measuring point on the temperature measuring optical fiber, which is recorded as T1'. The hot water outlet temperature is measured by the thermometer at the outlet of the heat exchange column, which is recorded as T c ; S3.

3. Collect the temperature of each measuring point during the temperature field recovery stage. The temperature in the wellbore from the wellhead to the bottom of the well is recorded as T1", T2", ... T n ".

8. The deep geothermal development wellbore heat exchange test method according to claim 7, characterized in that: In step S4, heat exchange power W=Q×Δt / 0.86, where W is heat exchange power (kW); Q is flow rate (m 3 / h); Δt: T c -T1'.

9. The deep geothermal development wellbore heat exchange test method according to claim 8, characterized in that: In step S4, during the temperature field recovery phase, when T n -T n "≤2℃, the temperature field is judged to be fully restored.

10. The deep geothermal development wellbore heat exchange test method according to claims 1-9, characterized in that: The temperature collection frequency of the temperature measuring point is 1 time / 4 hours to 1 time / day.

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