Method for long-distance lowering of large-diameter casing pipe in horizontal directional drill hole

Abstract

The invention discloses a method for long-distance lowering of a large-diameter sleeve in a horizontal directional drill hole, which comprises the following steps of: performing drill hole construction, flushing the drill hole by circulating water, firstly lowering a sleeve short section into the drill hole by using a drill rod, recording the current propelling depth when the sleeve short section encounters obstacles in the process of pushing the sleeve short section in the drill hole, and then withdrawing the drill rod and the sleeve short section to finish the long-distance lowering of the large-diameter sleeve in the horizontal directional drill hole. Re-sweeping the hole at the depth and circularly flushing the drilled hole; and then slowly pushing the casing pipe nipple into the drill hole by using the drill rod until the casing pipe nipple reaches the bottom of the hole, and finally officially lowering the long casing pipe. The casing pipe nipple with the diameter the same as that of the long casing pipe is firstly pushed once through the drill rod, and subsequent hole sweeping and water injection punching are matched, so that steps, fracture structures and redundant rock debris in a drill hole can be accurately and effectively removed, the risk when the long casing pipe is put down is greatly reduced, the casing pipe is prevented from being clamped, the casing pipe can be quickly put down to the bottom of the hole, and the service life of the casing pipe is prolonged. The problem of long-distance casing lowering in a horizontal directional drill hole is solved.

Description

Technical Field

[0001] This invention relates to the field of underground engineering construction technology. Specifically, it relates to a method for installing enlarged diameter casing over long distances within horizontal directional boreholes. Background Technology

[0002] Horizontal directional drilling is frequently involved in underground engineering construction. This type of drilling is widely used in geological exploration, gas drainage, trenchless paving, and geological remediation. Lowering casing can effectively improve the stability of horizontal boreholes; however, as the diameter and depth of horizontal boreholes gradually increase, lowering casing becomes increasingly difficult. Conventional small-diameter casing (50mm) can be lowered to a maximum depth of several hundred meters, fully meeting the needs of long-distance lowering. However, for large-diameter casing, such as 177.8mm, the difficulty of lowering increases rapidly with the depth. Ideally, the borehole wall should be intact and smooth, but in actual construction, long-distance horizontal directional drilling takes a long time. Due to the influence of strata movement, geological factors, mud erosion, and local accumulation of rock cuttings, the borehole wall may not remain in an ideal state in some areas. Large-diameter casing can hinder the lowering process. When this happens, the casing needs to be completely pulled out, the borehole cleaned using equipment, and then the casing needs to be lowered again. This process is very time-consuming and labor-intensive, and cases of casing getting stuck and unable to be pulled out occur frequently. To balance construction costs, the conventional lowering method generally controls the depth to around 100 meters, which restricts the development of horizontal casing construction. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to provide a method for lowering a large-diameter casing over a long distance in a horizontally directional borehole. This method can effectively increase the lowering depth of the large-diameter casing in the horizontally directional borehole, and will not cause problems such as jamming or deflection during the lowering process. It can enable the casing to be lowered into place quickly in one go, speed up the lowering speed, effectively avoid rework, and save construction costs and time.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for enlarging the diameter of a casing over a long distance in a horizontally directional borehole, comprising the following steps:

[0005] Step A: Drilling: Use a horizontal directional drilling rig to drill holes along the designed trajectory until the designed hole depth is reached;

[0006] Step B: Circulating water flushing of the borehole: High-pressure water is injected into the bottom of the hole through the drill rod, and the water flow from the bottom of the hole back to the opening of the hole is used to circulate and flush the borehole until the rock cuttings inside the hole are removed, ensuring that the borehole is unobstructed;

[0007] Step C: Lowering the casing sub: First, withdraw the drill pipe from the borehole. Then, install the casing sub with guide blocks on its surface onto the end of the drill pipe using a reducer. Use the drill pipe to slowly push the casing sub into the borehole. When the casing sub encounters an obstacle and cannot be pushed to the bottom of the hole in one go, record the current depth. Then, withdraw the drill pipe and casing sub, re-sweep the hole at this depth, and perform a circulating flush. Then, use the drill pipe again to slowly push the casing sub into the borehole until it reaches the bottom of the hole.

[0008] Step D: Formal lowering of the long casing: Use the drill pipe to slowly withdraw the short casing section from the borehole, install the short casing section on the front end of the long casing, use the drill pipe to push the rear end of the long casing, push the long casing to the designed hole depth, and complete the lowering of the casing.

[0009] By using the casing short section, the permeability of the borehole can be preliminarily tested, and targeted cleaning and flushing can be carried out to ensure the smooth lowering of the long casing and avoid rework and pipe jamming problems.

[0010] In the method described above for enlarging the diameter of a casing over a long distance in a horizontally directional borehole, in step C, guide and centering blocks are provided on the wall of the casing subsection at least near both ends. These guide and centering blocks are supported between the outer wall of the casing subsection and the borehole wall, ensuring that the outer wall of the casing subsection does not contact the borehole wall. The purpose of these guide and centering blocks is to straighten and support the casing subsection, preventing direct friction between the casing subsection and the borehole wall.

[0011] The above-mentioned method for enlarging the diameter of a casing over a long distance in a horizontally directional borehole includes four guide and centering blocks evenly spaced along the circumferential direction on each end of the casing short section; there is a gap between two circumferentially adjacent guide and centering blocks; the guide and centering blocks are staggered from each other in the axial direction. By setting multiple guide blocks, it is possible to detect and determine whether there are insurmountable obstacles inside the borehole wall. These obstacles are generally continuous in the circumferential direction and / or in the axial direction, and are very likely to jam the casing wall. Setting guide blocks is equivalent to increasing the outer diameter of the casing sub. Furthermore, by using guide blocks at two different distribution angles, it is possible to effectively detect hard obstacles or insurmountable obstacles that may jam the casing. When there are soft obstacles inside the borehole wall that are not easy to jam the casing, such as rock cuttings, gaps can be set to allow the rock cuttings to pass through, avoiding jamming the casing sub. This achieves the detection and judgment of hard obstacles while avoiding jamming by soft obstacles, ensuring that the subsequent long casing can be lowered smoothly, and minimizing the number of times the casing sub is withdrawn, thus achieving a balance between detection effect and efficiency.

[0012] In the above-mentioned method for enlarging the diameter of a casing over a long distance in a horizontally directional borehole, the thickness of the guide straightening block protruding from the casing short section is 12 mm, and its axial distribution length in the casing short section is 150 mm; the radial distance from the side of the guide straightening block away from the casing short section to the axis of the casing short section is less than the radius of the borehole. The borehole diameter is 219.5 mm, and the casing outer diameter is 177.8 mm. A 12 mm guide block is installed, with a gap of a few millimeters between the guide block and the borehole wall. The casing sub has radial movement in the borehole, making it easy to push. At the same time, the casing sub can still tilt slightly in the borehole, allowing for early detection of sections that could cause casing deviation and affect casing descent. This is especially important in the curved sections of the borehole. If the guide block completely fills the gap between the casing sub and the borehole, the friction is very high, increasing the difficulty of pushing and making it difficult to accurately detect and judge obstacles in the borehole. The casing sub cannot deflect relative to the borehole, making it impossible to simulate and judge the above situations, and thus it is impossible to guarantee the smooth descent of the subsequent casing.

[0013] In the aforementioned method for enlarging the diameter of casing over a long distance in horizontal directional drilling, each of the guiding and centering blocks has an inclined surface at both ends that connects to the wall of the casing section, with the angle between the inclined surface and the wall of the casing section being 30°. When encountering localized steps or fracture structures within the borehole, the inclined surface can guide the casing section to perform a certain radial movement, thereby determining whether the corresponding obstacle will cause the casing to jam.

[0014] In the above-mentioned method for enlarging the diameter of a casing over a long distance in a horizontal directional borehole, in step C, one end of the reducing joint is threadedly connected to the end of the drill rod, and the other end of the reducing joint is threadedly connected to the end of the casing stub.

[0015] The aforementioned method for long-distance enlarged diameter casing in horizontal directional drilling involves a reducing joint comprising a small-diameter end and a large-diameter end. The small-diameter end and the large-diameter end are coaxially welded together and fluid-conducting with each other. A gap exists between the casing sub and the borehole to allow fluid passage, minimizing the impact on borehole pressure during the pushing or pulling of the casing sub. Both the small-diameter end and the large-diameter end are internally threaded. The small-diameter end has the same outer diameter as the drill pipe and is threadedly connected, while the large-diameter end has the same outer diameter as the casing sub and is also threadedly connected. By using the reducing joint, a thrust is applied from the tail of the casing sub, consistent with the actual casing lowering process. Furthermore, the reducing joint design provides better radial elasticity, increasing the end flexibility of the casing sub during pushing and improving sensitivity to various obstacles, especially those that could cause casing deflection.

[0016] In the above-mentioned method for enlarging the diameter of a casing over a long distance in a horizontally directional borehole, the outer diameter of the casing short section, the long casing, and the reducing joint is the same at the end connected to the casing short section.

[0017] In the above-mentioned method for enlarging the diameter of a long-distance casing in a horizontally directional borehole, in step D, the long casing is formed by connecting multiple casing sections.

[0018] In the above-mentioned method for enlarging the diameter of a casing over a long distance in a horizontally directional borehole, in step D, after the casing short section is completely withdrawn from the borehole by the drill rod, the casing short section is first removed from the reducing joint, then the long casing is installed on the reducing joint, and finally the casing short section is installed on the front end of the long casing, using the casing short section to guide the long casing forward in the borehole.

[0019] The technical solution of the present invention achieves the following beneficial technical effects:

[0020] By first pushing a short casing section with the same diameter as the long casing through the drill pipe, and then combining it with subsequent hole sweeping and water injection flushing, steps, fracture structures, and excess rock cuttings in the borehole can be accurately and effectively removed. This greatly reduces the risk of lowering the long casing, prevents the casing from getting stuck, and allows the casing to be quickly lowered to the bottom of the hole, solving the problem of long-distance casing lowering in horizontal directional drilling. Attached Figure Description

[0021] Figure 1 A schematic diagram of the front end of the casing short section of the present invention entering the borehole;

[0022] Figure 2 A schematic diagram showing the sleeve section of the present invention reaching the bottom of the hole;

[0023] Figure 3 Schematic diagram of the sleeve short section of the present invention;

[0024] Figure 4 A schematic diagram of the end structure of the sleeve short section of the present invention;

[0025] Figure 5 A schematic diagram of the reducing connector of this invention.

[0026] The reference numerals in the figure are as follows: 1-sleeve short section; 2-guide and straightening block; 3-inclined surface; 4-reducing joint; 41-small diameter end; 42-large diameter end. Detailed Implementation

[0027] This embodiment describes a method for long-distance casing installation with enlarged diameter in horizontal directional drilling. The drilling diameter is 219.5 mm, and the casing diameter is 177.8 mm. Figure 1-2 As shown, it includes the following steps:

[0028] Step A: Drilling: Use a horizontal directional drilling rig to drill holes along the designed trajectory until the designed hole depth is reached;

[0029] Step B: Circulating water flushing of the borehole: High-pressure water is injected into the bottom of the hole through the drill rod, and the water flow from the bottom of the hole back to the opening of the hole is used to circulate and flush the borehole until the rock cuttings inside the hole are removed, ensuring that the borehole is unobstructed;

[0030] Step C: Lowering the casing section: First, withdraw the drill rod from the borehole and remove the drill bit from the end of the drill rod. Then, install the casing section 1, which has a guide and centering block 2 on its surface, onto the end of the drill rod through the reducer 4. Use the drill rod to slowly push the casing section 1 into the borehole. When the casing section 1 encounters an obstacle and cannot be pushed to the bottom of the hole in one go, record the current depth. Then, withdraw the drill rod and casing section 1, re-sweep the hole at this depth, and perform a circulating flush. Then, use the drill rod again to slowly push the casing section 1 into the borehole until it reaches the bottom of the hole.

[0031] Step D: Formal Lowering of the Long Casing: After slowly withdrawing the short casing section 1 from the borehole using the drill pipe, first remove the short casing section 1 from the reducer 4, then install the long casing on the reducer 4, install the short casing section 1 at the front end of the long casing, and push the rear end of the long casing using the drill pipe. The long casing is composed of multiple casing sections joined together. Push the casing section by section, using the short casing section 1 to guide the long casing forward in the borehole until the long casing is pushed to the designed hole depth, thus completing the lowering of the casing.

[0032] like Figure 3-4 As shown, in step C, guide and centering blocks 2 are provided on the wall of the casing sub 1 at least near both ends; the guide and centering blocks 2 are supported between the outer wall of the casing sub 1 and the borehole wall, so that the outer wall of the casing sub 1 does not contact the borehole wall. Figure 4 As shown, four guide and straightening blocks 2 are evenly spaced along the circumference at each end of the casing short section 1; there is a gap between two adjacent guide and straightening blocks 2 in the circumferential direction; the guide and straightening blocks 2 are staggered in the axial direction. Specifically, the thickness of the guide and straightening blocks 2 protruding from the casing short section 1 is 12mm, and the length distributed in the axial direction of the casing short section 1 is 150mm; each guide and straightening block 2 has a bevel 3 at both ends that connects to the wall of the casing short section 1, and the angle between the bevel 3 and the wall of the casing short section 1 is 30°; the radial distance from the side of the guide and straightening block 2 away from the casing short section 1 to the axis of the casing short section 1 is less than the radius of the borehole, that is, after the casing short section 1 with guide and straightening blocks 2 is installed in the borehole, there is an average gap of 8mm between the guide and straightening blocks 2 and the borehole wall. In practice, due to gravity, the lower guide and straightening blocks 2 will fit against the borehole wall, and the gap between the upper guide and straightening blocks 2 and the borehole wall will increase.

[0033] like Figure 5As shown, in step C, the reducing connector 4 includes a small diameter end 41 and a large diameter end 42. The small diameter end 41 and the large diameter end 42 are coaxially welded and fixed together, and the small diameter end 41 and the large diameter end 42 are fluidly connected to each other. Both the small diameter end 41 and the large diameter end 42 are provided with internal threads. The small diameter end 41 has the same outer diameter as the drill pipe and is threadedly connected. The large diameter end 42 has the same outer diameter as the casing stub 1 and is threadedly connected. The outer diameter of the casing stub 1, the long casing, and the reducing connector 4 is the same at the end connected to the casing stub 1.

[0034] In the initial stage of construction, the borehole wall is generally circular and relatively smooth. Before the casing is lowered, the borehole wall may exhibit faults, protrusions, steps, fracture structures, etc. If such structures intrude into the borehole in a small area, they will not significantly affect the casing lowering. Similarly, the presence of a small amount of rock cuttings in the borehole will also not significantly affect the casing lowering. However, the presence of continuous or large and numerous obstacles in the borehole can easily affect the casing lowering. This invention utilizes the method of lowering a casing section 1 first to detect unseen structures within the borehole, distinguish different obstacle types, identify obstacles that may hinder the casing lowering, and eliminate obstacles that are unlikely to impede the casing lowering, ensuring the smooth and rapid lowering of the subsequent casing and guaranteeing construction efficiency.

[0035] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A method of long distance lowering of a large diameter casing within a horizontal directional borehole, characterized by, The method comprises the following steps: Step A: drilling operation: using a horizontal directional drilling machine to drill a hole according to the designed trajectory until the designed hole depth is reached; Step B: circulating water flushing of the hole: high-pressure water flow is injected into the hole bottom through the drill rod, and the hole is flushed in a circulating manner by using the water flow flowing from the hole bottom to the hole opening until the hole is cleaned and the hole is unobstructed; Step C: lowering the casing segment: the drill rod is first withdrawn from the hole, then the casing segment (1) provided with a guide centralizer (2) on the surface is installed on the end of the drill rod through the reducing adapter (4), and the casing segment (1) is slowly pushed into the hole by the drill rod; when the casing segment (1) cannot be pushed to the hole bottom at one time due to obstruction, the current pushing depth is recorded, then the drill rod and the casing segment (1) are withdrawn, the depth is re-scanned and the hole is flushed in a circulating manner; then the casing segment (1) is slowly pushed into the hole by the drill rod again until it is pushed to the hole bottom; Step D: formally lowering the long casing: the casing segment (1) is slowly withdrawn from the hole by the drill rod, the casing segment (1) is installed at the front end of the long casing, and the rear end of the long casing is pushed by the drill rod to push the long casing to the designed hole depth, thereby completing the lowering of the casing.

2. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to claim 1, characterised in that, In step C, at least two end positions of the casing segment (1) are provided with guide centralizers (2); the guide centralizers (2) are supported between the outer wall of the casing segment (1) and the hole wall of the hole, so that the outer wall of the casing segment (1) does not contact the hole wall of the hole.

3. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to claim 2, characterised in that, Four guide centralizers (2) are equally spaced in the circumferential direction on each end of the casing segment (1); there is a gap between the circumferentially adjacent two guide centralizers (2); and the guide centralizers (2) are arranged axially staggered.

4. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to any one of claims 1 to 3, characterised in that, The guide centralizers (2) protrude from the thickness of the casing segment (1) by 12 mm, the distribution length of the guide centralizers (2) in the axial direction of the casing segment (1) is 150 mm, and the radial distance from the side of the guide centralizers (2) away from the casing segment (1) to the axis of the casing segment (1) is less than the radius of the hole.

5. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to claim 4, wherein, Both ends of each guide centralizer (2) are provided with a bevel (3) connected to the wall of the casing segment (1), and the included angle between the bevel (3) and the wall of the casing segment (1) is 30°.

6. A method of long distance dropping of a large diameter casing in a horizontal directional borehole according to claim 1, wherein, In step C, one end of the reducing adapter (4) is threadedly connected with the end of the drill rod, and the other end of the reducing adapter (4) is threadedly connected with the end of the casing segment (1).

7. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to claim 6, characterised in that, The reducing adapter (4) comprises a small-diameter end (41) and a large-diameter end (42), the small-diameter end (41) and the large-diameter end (42) are coaxially welded and fixed together, and the small-diameter end (41) and the large-diameter end (42) are in fluid communication with each other; the small-diameter end (41) and the large-diameter end (42) are both provided with internal threads, the small-diameter end (41) and the drill rod have the same outer diameter and are threadedly connected, and the large-diameter end (42) and the casing segment (1) have the same outer diameter and are threadedly connected.

8. A method of long distance dropping of a large diameter casing in a horizontal directional bore according to claim 1, wherein, The casing segment (1), the long casing and the end of the reducing adapter (4) connected with the casing segment (1) have the same outer diameter.

9. A method of long distance dropping of a large diameter casing in a horizontal directional borehole according to claim 1, wherein, In step D, the long casing is formed by butting the casing segments.

10. A method of long distance lowering of a large diameter casing within a horizontal directional bore according to claim 1, wherein, In step D, after the casing segment (1) is completely withdrawn from the borehole by the drill rod, the casing segment (1) is first detached from the variable-diameter joint (4), then the long casing is installed on the variable-diameter joint (4), and finally the casing segment (1) is installed on the front end of the long casing to guide the long casing to advance in the borehole.

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