Reinforcing device for cement of shallow hole of geothermal well and construction process of reinforcing device

Abstract

The invention discloses a reinforcing device for geothermal well shallow hole cement and a construction technology of the reinforcing device. The construction technology comprises the following steps that firstly, a sleeve is placed on the periphery of a shallow hole well wall; secondly, a reinforcing device is arranged between the casing pipe and the well wall, wherein the reinforcing device comprises a supporting ring, a flow guide pipe, a packing layer and an expansion filling unit; thirdly, cement paste is injected into a gap between the casing pipe and the well wall through the flow guide pipe; and fourthly, before the cement paste is solidified, gaps of the shallow holes are evenly filled with the cement paste through the combined action of an expansion filling unit and a packing layer, and the well cementation sealing performance is improved. And the casing pipe is always kept at the central position in the running and grouting processes, so that the casing pipe is effectively prevented from being deflected or deformed due to lateral pressure of a stratum, and the overall uniformity and reliability of well cementation quality are improved.

Description

Technical Field

[0001] This invention relates to the field of geothermal well cementing construction technology, and in particular to a cement cementing construction process and reinforcement device suitable for shallow borehole sections. Background Technology

[0002] During the drilling process of geothermal wells, cementing is required to seal the casing and wellbore to prevent shallow groundwater leakage and hot water upwelling. However, existing shallow-hole cementing methods generally suffer from the following problems: Loose wellbore structure makes it prone to local grout leakage during grouting; uneven distribution of cement slurry in the shallow hole annulus leads to voids or debonding; the casing is affected by lateral pressure during grouting, which may cause displacement or tilting, thereby reducing cementing quality; therefore, how to achieve stable cementing effect in shallow hole sections and ensure uniform filling of cement slurry has become an urgent technical problem to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide a cement reinforcement device for shallow borehole geothermal wells and its construction process, so as to solve the problems of uneven cement slurry distribution, poor well sealing and easy casing displacement in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a cement reinforcement device for shallow geothermal wells and its construction process, wherein the construction process includes the following steps: Step 1: Place casing around the outer perimeter of the shallow wellbore; Step 2: Install a reinforcement device between the casing and the wellbore. The reinforcement device includes a support ring, a guide pipe, a sealing layer, and an expansion filling unit. Step 3: Inject cement slurry into the gap between the casing and the well wall through the guide pipe; Step 4: Before the cement slurry solidifies, the expansion filling unit and the sealing layer work together to make the cement slurry evenly fill the shallow hole gaps and improve the cementing sealing performance.

[0005] As a preferred embodiment of the present invention, the support rings are arranged at intervals along the circumference of the shallow hole well wall to form a zoned support, which is used to prevent the casing from shifting during the grouting process.

[0006] As a preferred embodiment of the present invention, the guide pipe is provided with multiple radial slurry outlets, which are arranged inclined toward the well wall to achieve uniform distribution of cement slurry in the annulus.

[0007] As a preferred embodiment of the present invention, the sealing layer is made of flexible composite rubber material, which can automatically expand and fit the well wall under the action of grouting pressure, thereby blocking the backflow of cement slurry.

[0008] As a preferred embodiment of the present invention, the expansion filling unit is made of a water-swellable material, and its expansion direction extends radially to compensate for irregular voids in the well wall.

[0009] As a preferred technical solution of the present invention, the construction process adopts a segmented grouting method, and the grouting volume and pressure of each segment can be adjusted to adapt to different geothermal well formation conditions.

[0010] As a preferred embodiment of the present invention, the reinforcement device can be lowered into the well along with the casing and positioned by a mechanical limiting structure; and the reinforcement device and the casing are detachably connected to facilitate subsequent construction or maintenance.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: The geothermal well shallow hole cement reinforcement device and its construction process of the present invention, by setting support rings arranged at intervals around the outer periphery of the casing, ensure that the casing remains in the center position during the lowering and grouting process, effectively avoiding the casing from deflection or deformation due to lateral pressure from the formation, thereby improving the overall uniformity and reliability of the cementing quality; the guide pipe is provided with multiple inclined slurry outlets, which can form diffusion flow and rotation flow in the annulus, so that the cement slurry is evenly distributed in the shallow hole section, avoiding local slurry deposition or voids; the sealing layer is made of flexible composite rubber material, which can automatically expand and fit the well wall under the action of grouting pressure, thereby forming a ring-shaped sealing barrier to prevent the cement slurry from backflowing and improving the sealing integrity of the cementing; the expansion filling unit is made of water-swellable material, which can expand radially at the cement slurry solidification front and fill the small cracks or irregular gaps between the well walls, further improving the slurry filling effect and solving the common slurry leakage problem in shallow loose formations. Detailed Implementation

[0012] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Example 1: This invention provides a cement reinforcement device for shallow geothermal wells and its construction process, the construction process including the following steps: Step 1: Place casing around the outer perimeter of the shallow wellbore; Step 2: Install a reinforcement device between the casing and the wellbore. The reinforcement device includes a support ring, a guide pipe, a sealing layer, and an expansion filling unit. Step 3: Inject cement slurry into the gap between the casing and the well wall through the guide pipe; Step 4: Before the cement slurry solidifies, the expansion filling unit and the sealing layer work together to make the cement slurry evenly fill the shallow hole gaps and improve the cementing sealing performance.

[0014] Preferably, the support rings are arranged at intervals along the circumference of the shallow hole wall to form zoned support, which is used to prevent the casing from shifting during the grouting process.

[0015] Preferably, the guide pipe is provided with multiple radial slurry outlets, which are arranged inclined toward the well wall to achieve uniform distribution of cement slurry in the annulus.

[0016] Preferably, the sealing layer is made of a flexible composite rubber material, which can automatically expand and fit the well wall under grouting pressure, thereby preventing cement slurry backflow.

[0017] Preferably, the expansion filling unit is made of a water-swellable material, and its expansion direction extends radially to compensate for irregular voids in the well wall.

[0018] Preferably, the construction process adopts a segmented grouting method, and the grouting volume and pressure of each segment can be adjusted to adapt to different geothermal well formation conditions.

[0019] Preferably, the reinforcement device can be lowered into the well along with the casing and positioned by a mechanical limiting structure; and the reinforcement device and the casing are detachably connected to facilitate subsequent construction or maintenance.

[0020] Example 2; Overall structure of the device: The reinforcement device includes a support ring, a guide pipe, a sealing layer, and an expansion filling unit, wherein: Support ring: It has a circular structure and is fitted onto the outer wall of the casing. Its outer diameter is slightly larger than the outer diameter of the casing by 5 to 10 mm. One support ring is installed every 1 to 2 m along the length of the casing. The support ring is made of corrosion-resistant alloy steel and has multiple evenly distributed reinforcing ribs on its outer surface, which are used to provide radial support for the casing during grouting.

[0021] The guide pipe is located on the outside of the support ring and is connected to the grouting pipe inside the casing. The guide pipe has multiple inclined grout outlets with a diameter of 5 to 10 mm. The direction of the grout outlets is at an angle of 30° to 45° relative to the axis of the guide pipe, so that the injected cement grout forms a rotating flow field in the annulus.

[0022] Packing layer: Located between the support ring and the well wall, the packing layer is made of flexible composite rubber material with a thickness of approximately 20 mm. During high-pressure grouting, the packing layer can expand radially, forming a tight fit with the well wall, thereby preventing grout backflow.

[0023] Expandable filling unit: Located on the outer surface of the sealing layer, it is coated with water-swellable resin. After contacting the water in the cement slurry, it slowly expands radially, increasing in volume by 20-50% to fill the tiny cracks and irregular cavities between the well wall and the sealing layer.

[0024] Construction process steps The casing is pre-assembled with the reinforcement device and lowered into the shallow borehole section of the geothermal well. The support ring ensures the casing remains centered in the wellbore, preventing deviation caused by wellbore side pressure. After the casing reaches the designed depth, the annulus is inspected using sonic logging tools to confirm the presence of irregular gaps between the casing and the wellbore, ensuring the expansion filling unit functions effectively. Cement slurry is prepared according to the designed mix ratio, typically using high-fineness silicate cement with added expansion agents and retarder to ensure good fluidity and stability under shallow formation conditions. The slurry is injected into the casing using a grouting pump, sequentially entering the guide pipe and exiting through multiple inclined outlets, forming a rotating diffusion flow. To ensure construction quality, a segmented grouting process was adopted, with each segment having a length of 3–5 m. The grouting pressure increased progressively in each segment to ensure that the grout fully filled the annulus. As the grouting pressure increased, the sealing layer gradually expanded and adhered to the well wall, forming a sealing barrier that effectively prevented grout backflow. The self-adaptive expansion characteristics of the sealing layer allowed it to adapt to different well diameters and well wall roughness. After grouting, the expansion filling unit gradually expanded upon contact with the water in the cement grout, further filling irregular voids in the well wall and preventing channeling caused by grout not covering the pores. After the grout fully diffused, filled, and sealed the annulus, the curing stage began. After the cement grout solidified, a dense cement ring was formed in the shallow borehole section, effectively fixing the casing and sealing channels for different formation water bodies, thus completing the cementing construction. The following effects were achieved through the device and process described in this embodiment: Casing centering is guaranteed: the segmented arrangement of the support ring improves the stability of the casing in shallow sections and avoids deflection; uniform slurry distribution: the rotating diffusion flow formed by the inclined slurry outlet of the guide pipe ensures uniform distribution of cement slurry in the annulus, reducing the risk of local voids; enhanced sealing: the expansion of the sealing layer tightly adheres to the well wall, preventing slurry backflow and significantly improving the cementing sealing effect; void filling: the expansion filling unit expands upon contact with water, filling the well wall gaps and improving cementing integrity; improved adaptability: the segmented grouting method can be flexibly adjusted according to different well wall structures, ensuring cementing effect under complex formation conditions; improved construction efficiency and safety: the device is lowered as a whole with the casing, simplifying the construction process and reducing the intensity of manual operation and construction risks.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A shallow-hole cement reinforcement device for geothermal wells and its construction process, characterized in that, The construction process includes the following steps: Step 1: Place casing around the outer perimeter of the shallow hole well wall; Step 2: Install a reinforcement device between the casing and the wellbore. The reinforcement device includes a support ring, a guide pipe, a sealing layer, and an expansion filling unit. Step 3: Inject cement slurry into the gap between the casing and the well wall through the guide pipe; Step 4: Before the cement slurry solidifies, the expansion filling unit and the sealing layer work together to make the cement slurry evenly fill the shallow hole gaps and improve the cementing sealing performance.

2. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The support rings are arranged at intervals along the circumference of the shallow hole wall to form zoned support, which is used to prevent the casing from shifting during the grouting process.

3. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The guide pipe is equipped with multiple radial slurry outlets, which are arranged at an angle toward the well wall to achieve uniform distribution of cement slurry in the annulus.

4. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The sealing layer is made of flexible composite rubber material, which can automatically expand and fit the well wall under the grouting pressure, thereby preventing the backflow of cement slurry.

5. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The expansion filling unit is made of water-swellable material, and its expansion direction extends radially to compensate for irregular voids in the well wall.

6. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The construction process employs a segmented grouting method, where the grouting volume and pressure of each segment are adjustable to adapt to different geothermal well formation conditions.

7. The shallow-hole cement reinforcement device for geothermal wells and its construction process according to claim 1, characterized in that: The reinforcement device can be lowered into the well along with the casing and positioned by a mechanical limiting structure; and the reinforcement device and the casing are detachably connected to facilitate subsequent construction or maintenance.