An improved structure of a sandstone geothermal well with the same diameter

Abstract

The present invention discloses an improved structure of a sandstone geothermal well with the same diameter, belonging to the technical field of geothermal well structure, including: a reducing male and female joint, an upper cover set at the upper end of the reducing male and female joint, and a lower cover set at the lower end of the reducing male and female joint; the reducing male and female joint is divided into: a sealing section, a bearing section set below the sealing section, and a reducing section set below the bearing section from the upper end to the lower end; the sealing section is coaxially connected with the upper cover, and the reducing section is coaxially connected with the lower cover; the upper cover is connected with the reducing male and female joint by a thread, and the lower cover is fixedly connected with the reducing male and female joint by a coupling; a V-shaped groove is provided on the outer wall of the contact position between the reducing male and female joint and the lower cover. In this scheme, by reducing the diameter of the well body structure, the disadvantage that the cement plug at the lower part of the bottleneck caused by the same diameter well body structure cannot be completely removed is solved, and the hard jam accident caused by the falling of cement blocks is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of geothermal well structures, and in particular to an improved structure of a sandstone geothermal well with a same-diameter wellbore. Background Art

[0002] In the development of sandstone geothermal wells, the original wellbore structure uses the same specifications of surface casing (outer diameter Steel grade J55, wall thickness 9.65mm, trapezoidal buckle); the second opening has been continuously explored and improved from the original sleeve overlap connection to the hanger overlap suspension connection, from the use of ordinary hangers to fully sealed hangers, striving to achieve high-quality and efficient sandstone geothermal well body structure quality and continuous and stable production capacity.

[0003] These hangers all require a prefabricated hanging cone to determine the hanging position, and to achieve hanging and sealing at this position; however, in actual application, it was found on site that the rigid diameter change of the inner hole formed by the cone caused the cement plug formed after the first cementing to form a bottleneck at the diameter change part of the hanger male and female joints, and the cement plug was lowered before the second cementing. When the drill bit is cleaning the cement plug, only the area above the pass can be thoroughly cleaned, while the area below the pass is less cleaned due to the smaller aperture of the pass. The drill bit cannot pass through, so it is impossible to clean it thoroughly. The drill bit cannot pass through, so it is impossible to clean thoroughly. The inner diameter of the surface casing There is a big difference. The thickness of the tubular cement residue formed by the annular seam reaches 39.55mm, which cannot be completely removed. During the secondary drilling process, due to the vibration and impact of the drill bit, these residual cement randomly falls off in blocks into the wellbore, causing block blocking to the drill bit, affecting smooth drilling and even causing hard jamming accidents. Summary of the invention

[0004] In view of the above problems, the present invention provides an improved structure of a sandstone geothermal well with a same-diameter wellbore.

[0005] The technical solution adopted by the present invention is: an improved structure of a sandstone geothermal well with the same diameter, comprising: a reducing male and female joint, an upper cover arranged at the upper end of the reducing male and female joint, and a lower cover arranged at the lower end of the reducing male and female joint;

[0006] The reducing male and female joint is divided into: a sealing section, a bearing section arranged below the sealing section, and a reducing section arranged below the bearing section, from the upper end to the lower end;

[0007] The sealing section is coaxially connected to the upper cover, and the reducing section is coaxially connected to the lower cover.

[0008] Furthermore, the upper cover is connected to the reducer male and female joints via threads, and the lower cover is fixedly connected to the reducer male and female joints via couplings.

[0009] Furthermore, a V-shaped groove is provided on the outer wall of the contact position between the reducer male and female joint and the lower cover;

[0010] The coupling is clamped in the V-shaped groove, and the contact surface between the coupling and the V-shaped groove is arranged as a V-shaped inclined surface matching the V-shaped groove.

[0011] Furthermore, the sealing section is the portion between the upper end and the lower end of the reducing male and female joint where the inner diameter does not change;

[0012] The load-bearing section is a portion with an inclination on the inner wall of the reducer male and female joints;

[0013] The reducing section is the portion between the lower end of the bearing portion and the lower end of the reducing male and female joints.

[0014] Furthermore, the outer wall structure from the bearing section to the diameter-changing section is a stepped structure.

[0015] Furthermore, there is at least one group of steps arranged on the outer wall from the load-bearing section to the diameter-changing section.

[0016] Furthermore, the outer diameter of the sealing section inner diameter

[0017] The inner diameter of the upper end of the bearing section Lower end inner diameter

[0018] The inner diameter of the reducing section outer diameter

[0019] The inner diameter of the lower sleeve outer diameter

[0020] Furthermore, the diameter of the second drill bit during the second opening matches the diameter of the lower end of the bearing section.

[0021] Furthermore, the second drill bit diameter

[0022] Advantages of the present invention:

[0023] By making structural changes to the lower end part of the reducer male and female joints, the disadvantage that the cement plug at the lower part of the bottleneck caused by the same diameter wellbore structure cannot be completely removed is solved, that is, the formation of tubular cement blocks of cement at the lower end of the cement plug is reduced. Therefore, the drill bit can be smoothly raised and lowered during the second drilling, and the cement plug under the bottleneck can be completely removed during the second drilling, avoiding the occurrence of hard jamming due to the falling of residual cement blocks during the drilling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 is a front structural schematic diagram of an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the existing geothermal well structure.

[0027] Reference numerals:

[0028] 1 is a reducer male and female joint, 101 is a sealing section, 102 is a load-bearing section, 103 is a reducer section, 2 is an upper sleeve, 3 is a lower sleeve, and 4 is a coupling. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1

[0031] See also Figure 1 to Figure 2 ,like Figure 1 to Figure 2 As shown, an improved structure of a sandstone geothermal well with the same diameter comprises: a reducer male and female joint 1, an upper cover 2 arranged at the upper end of the reducer male and female joint 1, and a lower cover 3 arranged at the lower end of the reducer male and female joint 1;

[0032] The reducer male and female joint 1 is divided into: a sealing section 101, a load-bearing section 102 arranged below the sealing section 101, and a reducer section 103 arranged below the load-bearing section 102, from the upper end to the lower end;

[0033] The sealing section 101 is coaxially connected to the upper cover 2 , and the reducing section 103 is coaxially connected to the lower cover 3 .

[0034] It should be noted that in order to remove cement residues in the wellbore structure and ensure the normal use of the hanger, the only feasible way is to reduce the inner hole of the casing below the male and female joints of the hanger as much as possible while ensuring that the second-opening drill bit can pass smoothly, and match it with the specifications of the drill bit. The most feasible solution to achieve this goal is to reduce the diameter of the hanger so that there is no residue or the size of the cementing cement is reduced.

[0035] For example, the surface casing of the pump chamber section of a sandstone geothermal well is 13″3 / 8 Casing, two openings use 7″ The casing is used as technical casing, and the conventional secondary drill bit is used Specification drill bit, the matching casing can be selected 10″3 / 4 steel grade J55 Casing, 10″3 / 4 The inner diameter of the casing is Can guarantee The drill bit is smoothly lifted and lowered, and the cement plug under the pass can be completely removed during the second drilling.

[0036] In addition, casing is a steel pipe used to support the well wall of oil and gas wells to ensure the normal operation of the entire oil well during the drilling process and after completion. Each well uses several layers of casing according to different drilling depths and geological conditions. After the casing is laid, cement is used for cementing. Unlike oil pipes and drill pipes, it cannot be reused and is a one-time consumable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes. Casing can be divided into: guide tube, surface casing, technical casing and oil layer casing according to its use.

[0037] In one embodiment of the present invention, the upper cover 2 is connected to the reducer male and female joint 1 through threads, and the lower cover 3 is fixedly connected to the reducer male and female joint 1 through a coupling.

[0038] In one embodiment of the present invention, a V-shaped groove is provided on the outer wall of the contact surface between the reducer male and female joint 1 and the lower cover 2;

[0039] The coupling 4 is clamped in the V-shaped groove, and the contact surface between the coupling 4 and the V-shaped groove is set as a V-shaped inclined surface matching the V-shaped groove.

[0040] It should be noted that the arrangement of the V-shaped groove and the V-shaped slope increases the friction between the coupling 4 and the V-shaped groove, making it difficult for the coupling 4 to fall off the outer wall, thereby facilitating the coupling 4 to connect the lower surface pipe 2 with the reducer male and female joint 1.

[0041] In one embodiment of the present invention, the sealing section 101 is the portion between the upper end and the lower end where the inner diameter of the reducer male and female joint 1 does not change;

[0042] The load-bearing section 102 is a portion with an inclination on the inner wall of the reducer male and female joint 1;

[0043] The reducing section 103 is the portion between the lower end of the load-bearing section 102 and the lower end of the reducing male and female joint 1 .

[0044] In one embodiment of the present invention, the outer wall structure from the bearing section 102 to the diameter-changing section 103 is a stepped structure.

[0045] It should be noted that by setting the outer wall from the bearing section 102 to the reducing section 103 to a stepped structure, the friction force of cement on the pipe sleeve is increased during the cementing process, thereby facilitating the cementing process.

[0046] In one embodiment of the present invention, at least one set of steps is disposed on the outer wall from the bearing section 102 to the diameter-changing section 103 .

[0047] In one embodiment of the present invention, the outer diameter of the sealing section 101 is inner diameter

[0048] The inner diameter of the upper end of the bearing section 102 Lower end inner diameter

[0049] 103 diameter in the reducer section outer diameter

[0050] Inner diameter of lower cover 3 outer diameter

[0051] In one embodiment of the present invention, the diameter of the second drill bit during the second opening matches the diameter of the lower end of the bearing section 102 .

[0052] In one embodiment of the present invention, the diameter of the second drill bit is

[0053] Embodiment 2

[0054] Wellbore structure and strength verification of variable diameter hanger:

[0055] The variable diameter hanger is realized at the lower end of the original fully sealed hanger, maintaining the double sealing function of each section of the original hanger unchanged; after the casing of the second opening technology is put into the well, the load direction formed by its deadweight is downward. From the perspective of force analysis, the part above the load-bearing section is subjected to tensile stress, and the part above is subjected to internal compressive stress. The outer diameter and inner diameter of this part are The same as the casing, it is the weakest part of the male and female joints of the hanger and is a dangerous section, which needs to be strength checked.

[0056] For example, the outer diameter of the variable diameter part inner diameter Material J55, yield strength σ s =700Mpa,

[0057] The allowable stress is:

[0058] Assuming the weight of the double-opening casing is T and the compressive stress is σ, the following conditions should be met:

[0059]

[0060] That is: T≤158[σ]=73786MN=738t

[0061] From the calculation results, we can know that: It is safe to reduce the diameter of the casing here under the condition that the total weight is less than 738t.

[0062] Therefore, according to this plan, it is fully feasible to change the diameter of the wellbore structure through the hanger part. After this innovative improvement of the wellbore structure, the disadvantage of the cement plug at the bottom of the pass caused by the wellbore structure with the same diameter cannot be completely removed is solved, and the hard jamming accidents caused by the falling of cement blocks are avoided, making the previous two-opening variable diameter wellbore structure more technically feasible.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An improved structure of a sandstone geothermal well with a same diameter, characterized in that: include: A reducing male and female joint, an upper cover arranged at the upper end of the reducing male and female joint, and a lower cover arranged at the lower end of the reducing male and female joint; The reducing male and female joint is divided into: a sealing section, a bearing section arranged below the sealing section, and a reducing section arranged below the bearing section, from the upper end to the lower end; The sealing section is coaxially connected to the upper cover, and the reducing section is coaxially connected to the lower cover; The upper cover is connected to the reducer male and female joints by threads, and the lower cover is fixedly connected to the reducer male and female joints by couplings; A V-shaped groove is provided on the outer wall of the contact position between the reducer male and female joint and the lower cover; The coupling is clamped in the V-shaped groove, and the contact surface between the coupling and the V-shaped groove is set as a V-shaped inclined surface matching the V-shaped groove; The sealing section is the portion between the upper end and the lower end where the inner diameter of the reducer male and female joints does not change; The load-bearing section is a portion with an inclination on the inner wall of the reducer male and female joints; The reducing section is the portion between the lower end of the bearing portion and the lower end of the reducing male and female joints; The outer diameter of the sealing section inner diameter The inner diameter of the upper end of the bearing section Lower end inner diameter The inner diameter of the reducing section outer diameter The inner diameter of the lower sleeve outer diameter The diameter of the second drill bit during the second opening matches the diameter of the lower end of the bearing section; The lower end of the reducer male and female joints is structurally changed to solve the problem that the cement plug at the bottom of the pass cannot be completely removed due to the wellbore structure with the same diameter, and reduce the formation of tubular cement blocks at the bottom of the cement plug. Therefore, the drill bit can be smoothly tripped in the second opening, and the cement plug under the pass can be completely removed during the second opening drilling, avoiding the occurrence of hard jams caused by the residual cement blocks falling during the drilling process; The outer wall structure from the load-bearing section to the diameter-changing section is a stepped structure.

2. The improved structure of the sandstone geothermal well with the same diameter according to claim 1 is characterized in that: There is at least one group of steps arranged on the outer wall from the bearing section to the diameter-changing section.

3. The improved structure of the sandstone geothermal well with the same diameter according to claim 1 is characterized in that: The second drill bit diameter

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