Intercepting and cementing method for deep geothermal U-shaped well

Abstract

The invention relates to the field of well completion and cementing of U-shaped well drilling engineering, and discloses a deep geothermal U-shaped well intercepting and cementing method which comprises the following steps: S1, presetting a plurality of punching positions on a sleeve; s2, punching operation is conducted on the casing pipe at the punching position so that a series of fluid channels can be formed; s3, cement paste is conveyed to the fluid channel through the interior of the casing pipe and enters an annular area of the U-shaped well through the fluid channel; and S4, the flowing area of the cement paste is controlled, so that the cement paste is solidified in the annular area above the butt joint cavity of the U-shaped well, and closure and well cementation are achieved. According to the intercepting well cementation method, the drilling position is preset, and the fluid channel is formed, so that accurate conveying of the cement paste is achieved, a traditional complex pipe string structure and expensive tools are avoided, the construction process is simplified, the construction cost is reduced, and the construction efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of completion cementing for U-shaped well drilling engineering, and specifically to a method for intercepting and cementing a deep geothermal U-shaped well. Background Art

[0002] As a clean and renewable energy resource, deep geothermal energy has received increasing attention. In the development of deep geothermal energy, the U-shaped well, as an important well type structure, is widely used in the exploitation and utilization of geothermal energy. A deep geothermal U-shaped well refers to the docking and connection of a vertical well and a horizontal well. The U-shaped well plays an important role in geothermal energy development through the cyclic flow of groundwater.

[0003] As an important geothermal energy development structure, the deep geothermal U-shaped well faces multiple challenges in the cementing operation. In traditional cementing operations, the docking cavity is vulnerable to sealing effects after casing cementing, and at the same time, secondary plugging of the vertical well section is required, increasing the construction complexity and cost. In addition, traditional double-stage injection matching tools have risks in half-way cementing and are costly, bringing many inconveniences to geothermal energy development. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for intercepting and cementing a deep geothermal U-shaped well. For the cementing of deep geothermal U-shaped wells, an intercepting cementing method is proposed. Compared with the half-way cementing method in the industry, the risk is smaller, and it can reduce the investment in geothermal development of U-shaped wells, thus more effectively achieving the purpose of half-way cementing.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for intercepting and cementing a deep geothermal U-shaped well, comprising the following steps:

[0006] S1. Preset a plurality of punching positions on the casing;

[0007] S2. Perform punching operations on the casing at the punching positions to form a series of fluid channels;

[0008] S3. Convey the cement slurry through the inside of the casing to the fluid channels and enter the annulus area of the U-shaped well through the fluid channels;

[0009] S4. Control the flow area of the cement slurry to solidify the cement slurry in the annulus area above the docking cavity of the U-shaped well to achieve intercepting and cementing.

[0010] Preferably, the punching length of the casing is optimized to 15 meters to prevent the cement slurry from flowing laterally into the docking cavity of the U-shaped well.

[0011] Preferably, the punching density and hole diameter of the punched casing meet the requirements of casing strength and fluid flow regime during the construction process.

[0012] Preferably, the cement slurry has a predetermined density and viscosity coefficient to adapt to the high-temperature and high-pressure environment of deep geothermal wells.

[0013] Preferably, the density of the cement slurry is 1.8 g / ml and the viscosity coefficient is 120 cP.

[0014] Preferably, the drilling operation includes forming the fluid channel on the casing using mechanical, blasting or laser drilling techniques.

[0015] Preferably, it further includes: before transporting the cement slurry, injecting a cleaning fluid through the fluid channel to clean the annulus area of the U-shaped well.

[0016] Preferably, it further includes: measuring the plastic viscosity and yield value of the cement slurry using a rotational viscometer and adjusting the flow characteristics of the cement slurry according to the measurement results.

[0017] Preferably, the step of controlling the flow of the cement slurry includes monitoring the flow rate, pressure and temperature of the cement slurry in the annulus area of the U-shaped well.

[0018] Preferably, it further includes: determining the flow state of the cement slurry in the annulus area of the U-shaped well as laminar flow, transitional flow or turbulent flow before the cement slurry solidifies.

[0019] Preferably, it further includes: determining the flow state of the cement slurry according to the Reynolds number and critical Reynolds number of the Bingham plastic fluid.

[0020] The present invention also provides a casing string structure for intercepting and cementing a deep geothermal U-shaped well for implementing the above method, including:

[0021] A casing, on which a series of preset drilling positions are provided;

[0022] One or more fluid channels formed through the drilling positions on the casing;

[0023] An injection port for transporting the cement slurry to the fluid channel.

[0024] The present invention provides a method for intercepting and cementing a deep geothermal U-shaped well. It has the following beneficial effects:

[0025] The intercepting and cementing method of the present invention realizes the precise transportation of the cement slurry by presetting the drilling positions and forming fluid channels, avoids the traditional complex pipe string structure and expensive tools, simplifies the construction process, reduces the construction cost, and improves the construction efficiency. At the same time, the flow of the cement slurry is controlled to make it evenly distributed and solidify in the annulus area of the U-shaped well to form a sealing layer, effectively realizing the purpose of intercepting and cementing, improving the stability and reliability of intercepting and cementing, and reducing the subsequent maintenance cost and risk. Description of the Drawings

[0026] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0027] Figure 2 It is a schematic diagram of casing drilling, throttling and cementing of the present invention;

[0028] Figure 3 A schematic diagram of four rows of staggered holes of the present invention;

[0029] Figure 4 A schematic diagram of four rows of spiral holes of the present invention;

[0030] Figure 5 It is a schematic diagram of calculating the cross-sectional area of ​​the comparative screen tube of the present invention;

[0031] Figure 6 It is a schematic diagram of calculating the cross-sectional area of ​​a perforated pipe of a comparative example of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Please see attached Figure 1 The embodiment of the present invention provides a deep geothermal U-shaped well interception and cementing method, including steps S1 to S4, which are specifically as follows:

[0034] In step S1, a plurality of punching positions are preset on the casing.

[0035] In this step, the perforation positions on the casing are determined according to the specific U-shaped well design and geological conditions, and factors such as well depth, formation characteristics, geothermal and geopressure should generally be considered. The preset perforation positions should meet the needs of cement slurry delivery and curing, while avoiding affecting the stability of the casing structure.

[0036] In this embodiment, Figure 2 As shown, the preset drilling position refers to the well casing string down to the bottom of the well, a certain distance from the bottom of the well (20 meters to 25 meters from the bottom of the well for CRU type wells) on the casing body, comprehensively considering the anti-external squeeze strength of the casing after the hole is opened and the flow area of ​​the hole, to achieve short-circuit circulation cementing, and achieve the purpose of preventing the U-shaped well group docking cavity, especially the bottom part of the vertical well from being sealed by cement slurry.

[0037] In step S2, the casing is punched at the punching position to form a series of fluid channels.

[0038] In this step, for the punching operation, techniques such as mechanical punching, blasting punching or laser punching can be adopted, and a suitable punching method is selected according to the actual requirements and formation conditions. At the same time, the punching operation should ensure the smoothness and stability of the fluid channel to avoid generating debris or residues that may affect the subsequent delivery and curing of the cement slurry.

[0039] In this embodiment, when punching, first determine the preset punching positions on the casing, and then select appropriate mechanical punching equipment, such as a drilling rig or a drill bit. According to the pre-designed punching parameters and formation conditions, perform precise punching operations on the casing. After completing the punching operation, inspect the punching positions to ensure the quality and smoothness of the punching channels. Finally, carry out cleaning work to remove any possible debris or residues to ensure the unobstructedness of the fluid channel.

[0040] Among them, in step S3, convey the cement slurry through the inside of the casing to the fluid channel and enter the annulus area of the U-shaped well through the fluid channel.

[0041] In this step, inject the pre-prepared cement slurry into the inside of the casing through a conveying device and convey it to the annulus area of the U-shaped well through the fluid channel formed by punching. The design of the fluid channel should consider the flow characteristics of the cement slurry to ensure that the cement slurry can effectively enter the annulus area of the U-shaped well.

[0042] In this embodiment, during construction, first mix cement, water and other possible required additives according to a pre-determined ratio to ensure that the quality and performance of the cement slurry meet the requirements. Start the conveying device and begin to convey the pre-prepared cement slurry into the inside of the casing through the conveying device. Monitor parameters such as the flow rate, pressure and flow of the cement slurry to ensure that the cement slurry can stably enter the inside of the casing. Through the fluid channel formed by the preset punching positions, convey the cement slurry from the inside of the casing to the annulus area of the U-shaped well. Monitor the flow state of the cement slurry in the fluid channel to ensure that the cement slurry can smoothly enter the annulus area of the U-shaped well.

[0043] In some embodiments, before conveying the cement slurry, inject a cleaning fluid through the fluid channel to clean the annulus area of the U-shaped well.

[0044] Specifically, injecting a cleaning fluid through the fluid channel to clean the annulus area of the U-shaped well before conveying the cement slurry can ensure the cleanliness of the annulus area of the U-shaped well, which helps to improve the cementing effect and adhesion performance of the cement slurry.

[0045] Among them, in step S4, control the flow area of the cement slurry so that the cement slurry cures in the annulus area above the docking cavity of the U-shaped well to achieve intercepting cementing.

[0046] In this step, by monitoring parameters such as the flow rate, pressure, and temperature of the fluid channel, the flow state of the cement slurry is adjusted in real time to ensure that the cement slurry is evenly distributed in the annulus area of the U-shaped well. Control the flow of the cement slurry so that it gradually solidifies in the annulus area above the docking cavity of the U-shaped well, preventing the cement slurry from entering the docking cavity, forming a fixed plugging layer, and achieving the effect of intercepting and cementing.

[0047] Generally speaking, the intercepting and cementing method of the present invention realizes the precise delivery of the cement slurry by presetting the drilling position and forming a fluid channel, avoiding the traditional complex pipe string structure and expensive tools, simplifying the construction process, reducing the construction cost, and improving the construction efficiency. At the same time, control the flow of the cement slurry to prevent it from entering the docking cavity, make it evenly distributed and solidify in the annulus area of the U-shaped well, form a plugging layer, effectively achieve the purpose of intercepting and cementing, improve the stability and reliability of intercepting and cementing, and reduce the subsequent maintenance cost and risk.

[0048] As an embodiment of the present invention, the drilling length of the casing is set to 15 meters, which can effectively prevent the lateral flow of the cement slurry into the docking cavity of the U-shaped well.

[0049] As an embodiment of the present invention, the cement slurry has a predetermined density and viscosity coefficient to adapt to the high-temperature and high-pressure environment of deep geothermal wells.

[0050] In this embodiment, the density of the cement slurry is 1.8 g / ml, the viscosity coefficient is 120 cP, and the flow rate is 1.8 m 3 / min.

[0051] As an embodiment of the present invention, the method further includes: using a rotational viscometer to measure the plastic viscosity and yield value of the cement slurry, and adjusting the flow characteristics of the cement slurry according to the measurement results.

[0052] Specifically, according to the Reynolds number (Re = ρvd / μ, where v, ρ, and μ are the flow velocity, density, and viscosity coefficient of the fluid respectively, and d is the characteristic length), judge the flow state of the cement slurry. Calculate the cement slurry velocities in the perforated pipe, the hole, and the annulus between the casing and the wellbore to be 1.326 m / s, 0.663 m / s, and 1.393 m / s respectively, and the Reynolds numbers are 3377, 199, and 1362 respectively. And judge the flow state according to the following method:

[0053] For the plastic viscosity μ p,RV and yield value τ o,RV measured by the rotational viscometer, correct them according to the following formula:

[0054]

[0055]

[0056] Once we have these corrected values, we can calculate the Reynolds number for a Bingham plastic fluid as follows:

[0057] Calculation of the Reynolds number for a Bingham fluid

[0058] For pipe flow:

[0059]

[0060] For annulus flow, if the ratio of the outer diameter to the inner diameter D o / D h > 0.3, the narrow slit approximation should be used; otherwise, the pipe approximation should be used.

[0061] For the pipe approximation:

[0062]

[0063] For the narrow slit approximation:

[0064]

[0065] Next, we need to calculate the Hertz number He to determine the critical core gap ratio α c , and then calculate the upper critical Reynolds number and the lower critical Reynolds number These values will help us determine whether the flow regime is laminar, transitional, or turbulent. As follows:

[0066] Calculation of the critical Reynolds number for a Bingham plastic fluid: Hertz number calculation

[0067] Pipe flow: Pipe approximation: Narrow slit approximation: Calculation of the critical core gap ratio

[0068]

[0069] Calculation of the upper critical Reynolds number

[0070] Pipe flow:

[0071]

[0072] Annulus flow: Pipe approximation

[0073]

[0074] Annulus flow: Narrow slit approximation

[0075]

[0076] Calculation of the lower critical Reynolds number

[0077] Pipe flow:

[0078]

[0079] Annular flow: Pipe approximation

[0080]

[0081] Annular flow: Narrow slit approximation

[0082]

[0083] Bingham plastic fluid flow regime discrimination table

[0084]

[0085] By comparing the calculated Reynolds number with the critical Reynolds number, the flow regime of the cement slurry, whether it is laminar flow or turbulent flow, can be preliminarily judged, so as to preliminarily evaluate and control the fluid flow characteristics during the cementing process.

[0086] Please refer to the appendix Figure 2 , the present invention provides a casing string structure for deep geothermal U-shaped well plugging and cementing, which is used to implement the deep geothermal U-shaped well plugging and cementing method in the above-mentioned embodiments, including:

[0087] Casing, on which a series of preset punching positions are provided;

[0088] One or more fluid channels are formed through the punching positions on the casing;

[0089] Injection port, used to convey the cement slurry to the fluid channel.

[0090] In this embodiment, the casing string structure adopts a φ177.8mm punching guide shoe + 2 roots of φ177.8mm N80 casing with a wall thickness of 8.05mm BC thread punching casing + drillable float collar + 1 root of φ177.8mm N80 casing with a wall thickness of 8.05mm BC thread + drillable float collar + φ177.8mm N80 casing with a wall thickness of 8.05mm BC thread to the wellhead (take the example of CRU well group).

[0091] The punching pipe is consistent with the design casing specification for running into the well, which is a φ177.8mm N80 casing with a wall thickness of 8.05mm BC thread. 1.0m on both sides of the circumferential arrangement of the pipe body is not punched. The upper part of the second casing from the bottom of the well is punched for 5.0m, and the rest of the blind pipe is not punched, and the hole diameter ≥ Φ20mm (a total of ≥100); 1.0m on both sides of the other whole casing pipe body is not punched, and the rest are all punched.

[0092] For the perforated casing hole layout design, a perforated pipe with an outer diameter of 177.8 mm, a steel grade of N80, and a wall thickness of 8.05 mm is selected as the base pipe. There is a 1.0 m non-perforated area on both sides of the circumferentially arranged pipe body. The layout of the perforated pipe is as shown in Figure 3 and 4 . The entire pipe is perforated for a total of 5.0 m, and the blind pipes in the remaining positions are not perforated. Φ40 mm ≥ hole diameter ≥ Φ20 mm (a total of ≥ 100); another entire casing is evenly distributed in 4 circumferential rows, with 2 - 4 holes in 1 row. The longitudinal spacing between holes ranges from 100 mm ≥ hole spacing ≥ 50 mm. Among them, the holes in 2 rows are symmetric to each other. The hole diameters of the two casings and the longitudinal spacing between holes are the same.

[0093] Compared with the application in the string of the plugging and cementing matching tool, there is no outer casing packer and differential pressure dual-stage injection, and the structure is simpler. Only two tools save an investment of 87,000 yuan.

[0094] Comparative example:

[0095] The conventional thermal recovery well screen pipe has been verified on-site and meets the strength requirements. Its outer diameter is 177.8 mm, the wall thickness is 8.05 mm, the slot width is 0.3 mm, and there are 128 evenly distributed circumferentially. Its cross-sectional area is calculated, and the calculation result is 2042.752 mm 2 , as shown in Figure 5 .

[0096] The outer diameter of the perforated pipe is 177.8 mm, the wall thickness is 8.05 mm, and there are 2 evenly distributed 20 mm holes circumferentially. Its cross-sectional area is calculated, and the calculation result is 2068.387 mm 2 , as shown in Figure 6 .

[0097] By comparison, the cross-sectional area of the perforated pipe is larger than that of the screen pipe. This indicates that after removing some materials to form holes, the remaining cross-sectional area of the perforated pipe is still sufficient to provide strength similar to that of the screen pipe. Therefore, it can be inferred that the strength of the perforated pipe meets the requirements of the thermal recovery well.

[0098] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for intercepting and cementing a deep geothermal U-shaped well, characterized in that, It includes the following steps: S1. Preset a number of punching positions on the casing; S2. Perform a punching operation on the casing at the punching positions to form a series of fluid channels; S3. Convey the cement slurry through the inside of the casing to the fluid channels and enter the annulus area of the U-shaped well through the fluid channels; S4. Control the flow area of the cement slurry so that the cement slurry solidifies in the annulus area above the docking cavity of the U-shaped well to achieve cut-off cementing.

2. The deep geothermal U-shaped well plugging and cementing method according to claim 1, characterized in that, The punching length of the casing is optimized to 15 meters to prevent the cement slurry from flowing laterally into the docking cavity of the U-shaped well.

3. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1 or 2, characterized in that, The density of the cement slurry is 1.8 g / ml and the viscosity coefficient is 120 cP.

4. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, The punching operation includes forming the fluid channels on the casing using mechanical, blasting or laser punching techniques.

5. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, It also includes: Before conveying the cement slurry, inject a cleaning fluid through the fluid channels to clean the annulus area of the U-shaped well.

6. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, It also includes: Use a rotational viscometer to measure the plastic viscosity and yield value of the cement slurry and adjust the flow characteristics of the cement slurry according to the measurement results.

7. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, The step of controlling the flow of the cement slurry includes monitoring the flow rate, pressure and temperature of the cement slurry in the annulus area of the U-shaped well.

8. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, It also includes: Determine the flow state of the cement slurry in the annulus area of the U-shaped well as laminar flow, transitional flow or turbulent flow before the cement slurry solidifies.

9. A method for intercepting and cementing a deep geothermal U-shaped well according to claim 1, characterized in that, It also includes: Determine the flow state of the cement slurry according to the Reynolds number and critical Reynolds number of the Bingham plastic fluid.

10. A casing string structure for intercepting and cementing a deep geothermal U-shaped well, which is used to implement a method for intercepting and cementing a deep geothermal U-shaped well according to any one of claims 1-9, characterized in that, It includes: A casing with a series of preset punching positions thereon; One or more fluid channels formed through the punching positions on the casing; An injection port for conveying the cement slurry to the fluid channels.

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