CN112227464A

CN112227464A - A kind of thermal insulation structure of geothermal well shaft and construction method thereof

Info

Publication number: CN112227464A
Application number: CN202010992469.3A
Authority: CN
Inventors: 郤保平; 杨欣欣; 何水鑫; 辛国旭; 董赟盛; 成泽鹏; 李晓雪
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2020-09-21
Filing date: 2020-09-21
Publication date: 2021-01-15

Abstract

The invention belongs to the technical field of downhole heat exchange in geothermal wells, and in particular relates to a novel thermal insulation structure for a geothermal well wellbore and a construction method thereof, comprising a thermal insulation central pipe, a geothermal well casing and a drill pipe. In particular, it relates to a method of reserving a cavity between the thermal insulation central pipe and the casing of a geothermal well, and pressing thermal insulation mortar into the cavity from bottom to top through the center of the drill pipe to form a thermal insulation layer on site. coating. The present application provides a novel thermal insulation structure of a geothermal well shaft and a construction method thereof, which simplifies the construction process, improves the integrity of the thermal insulation layer, increases the thermal insulation performance, reduces heat loss, increases the outlet water temperature, and can effectively improve the utilization of thermal energy.

Description

Geothermal well shaft heat insulation structure and construction method thereof

Technical Field

The invention belongs to the field of geothermal energy development, and particularly relates to a geothermal well shaft heat insulation structure and a construction method thereof.

Background

Geothermal resources are clean renewable energy sources, are widely distributed in China, have abundant reserves and great development potential, and can be directly utilized. Fossil fuels which are widely used at present cannot be taken as a long-term measure for social development by virtue of the characteristics of non-regenerability, severe environmental pollution in the using process and the like. Therefore, the development of a clean and environment-friendly heating mode is not slow. The advantages of clean and renewable geothermal energy supply are that the problems of energy and environment can be well solved.

In the process of geothermal development, heat preservation and heat insulation are very important when fluid after heat exchange is extracted, and the temperature of extracted water and heat extraction power are directly related. Research shows that the temperature of the near-ground rock-soil layer is close to the ground and is far lower than the temperature of the fluid after heat exchange, so that the fluid has less heat loss at a larger well depth and most of the heat loss occurs at a smaller well depth in the geothermal energy exploitation, and the heat insulation layer is arranged at the smaller depth (well depth), so that the heat insulation performance of a shaft can be effectively improved, the heat loss is reduced, the temperature of the extracted fluid is improved, and the cost is reduced.

At present, in the exploitation of geothermal energy, the selection of pipeline heat-insulating materials and heat-insulating schemes not only relates to the operation efficiency of a system, but also relates to economic factors in the early investment and operation process. In order to reduce the heat loss of equipment and pipelines and improve the heat utilization rate, a plurality of scholars have proposed a plurality of shaft heat preservation technologies, but the problems of complex construction, higher cost, difficult realization and the like exist. The novel geothermal well shaft heat preservation technology can effectively improve the heat preservation performance of a shaft at a smaller well depth, improve the temperature of produced water, and can not only achieve the purposes of heat preservation and heat insulation, but also reduce the use cost.

Disclosure of Invention

The invention aims to solve the problems of low water outlet temperature and low heat energy utilization rate of a production well caused by heat loss in a shaft in the process of geothermal energy development. The invention provides a geothermal well shaft heat-insulating structure and a construction method thereof.

The invention adopts the following technical means to solve the technical problems: a kind of heat insulation structure of the well shaft of the geothermal well and its construction method, the heat insulation structure includes the heat insulation central pipe, sleeve and heat insulation layer sandwiched between heat insulation central pipe and sleeve, its construction method includes the following steps: after completion construction of a shaft is finished, a grout stop plug is installed at the depth h of a sleeve, a central pipe grout stop plug is arranged at the bottom of a heat insulation central pipe, and a hole which can just accommodate a drill rod is formed in the central pipe grout stop plug; the depth of putting the heat preservation center tube is h department, the center tube ends the thick liquid stopper and is located the top that ends the thick liquid stopper, and there is the clearance between the two, the back is accomplished in the installation of heat preservation center tube, form annular cavity between heat preservation center tube and the sleeve pipe, the hole that ends the thick liquid stopper with the bottom of drilling rod through the center tube stretches into the center tube and ends the thick liquid stopper and end the clearance between the thick liquid stopper, the heat preservation mortar gets into two thick liquid stopper clearances earlier through the drilling rod and gets into in the cavity afterwards, through adjustment slip casting pressure, make the heat preservation mortar from bottom to top fill the cavity closely knit, simultaneously with the liquid discharge in the cavity, treat that insulation construction is stable after, demolish the mortar layer that forms in two end thick liquid stopper and two end thick liquid stopper clearances, the heat preservation mortar forms the.

According to the geothermal well shaft heat insulation structure and the construction method thereof, the limiting devices are arranged on the periphery of the geothermal well shaft at intervals in the process of placing the heat insulation central pipe, so that the heat insulation central pipe is positioned in the center of the geothermal well shaft, and the heat insulation mortar is ensured to be uniformly distributed.

According to the geothermal well shaft heat insulation structure and the construction method thereof, the depth h is determined according to the factors of site geological conditions and stratum temperature.

According to the geothermal well shaft heat insulation structure and the construction method thereof, the difference between the inner diameter of the sleeve and the outer diameter of the heat insulation central pipe is 50-60mm, the thickness of the formed heat insulation layer is 50-60mm, and the heat conductivity coefficient of the heat insulation mortar is not more than 0.1W/m.K.

According to the geothermal well shaft heat insulation structure and the construction method thereof, the heat insulation central pipe is internally provided with the anticorrosive coating, and the thickness of the anticorrosive coating is 0.1-4 mm.

The invention has the advantages that: the heat preservation layer manufacturing construction method is simple to operate, economical and practical, the heat preservation structure is good in integrity, and the defects that the heat preservation effect of the joint is poor and the like are overcome. The heat of the stratum is fully utilized, the heat insulation performance of the shaft can be effectively improved, heat loss is reduced, the temperature of produced fluid is improved, and meanwhile, the cost can be reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention and the technical solutions in the prior art, the following briefly introduces the drawings, which are needed to be used in the description of the embodiments and the prior art. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a cross-sectional view of the construction process of the heat-insulating layer of the geothermal pipeline provided by the invention.

FIG. 2 is a top view of the construction process of the heat-insulating layer of the geothermal pipeline provided by the invention.

FIG. 3 is a sectional view of the heat-insulating layer of the geothermal pipeline.

FIG. 4 is a top view of the heat-insulating layer of the geothermal pipeline.

Reference numerals: 1-heat preservation central pipe; 2-a sleeve; 3, insulating layer; 4-stop-grouting plug; 5-central tube grout stop plug; 6-a drill rod; 7-a limiting device.

Detailed Description

The following further describes embodiments of the present invention with reference to the drawings, so as to explain the design principles and technical solutions of the present invention.

In the existing geothermal heating demonstration project, the designed well depth is 3000m, the ground elevation is 770m, the diameter of an opening of a geothermal well is 450mm, the inner diameter of the wellbore after the process of drilling, completing and casing the well 2 is 426mm (namely the inner diameter of the casing 2), and the diameter of a final hole of the geothermal well is 300mm (namely the inner diameter of the heat preservation central pipe 1).

As shown in the attached drawing 1, after the construction of the shaft well completion process with the design depth of 3000m is finished, a unidirectional horizontal grout stop plug 4 is installed at a position with the depth of 1000m in a sleeve 2, an anticorrosive coating is sprayed (provided) on the wall surface of a heat-insulating central pipe 1, a horizontal central pipe grout stop plug 5 is arranged at the end part of the bottom end of the heat-insulating central pipe 1, a round hole with the diameter of 100mm is reserved in the center of the central pipe grout stop plug 5, a drill rod 6 can pass through the round hole of the grout stop plug, in the lowering process, a limiting device 7 is arranged on the outer side of the heat-insulating central pipe 1 at an interval of 100m, the heat-insulating central pipe 1 is lowered to the position with the depth of 1000m along the sleeve 2. The heat preservation center tube 1 is a steel tube with the inner diameter of 300mm and the outer diameter of 320mm, and a cavity 3 with the width of 53mm is reserved between the sleeve 2 and the heat preservation center tube 1.

A drill rod 6 with the diameter of 100mm extends into a gap between two grout stop plugs through a central pipe grout stop plug 5, heat insulation mortar is pressed into a cavity 3 between a heat insulation central pipe 1 and a sleeve 2 through the drill rod 6, the cavity 3 is uniformly filled with the heat insulation mortar from bottom to top under the action of grouting pressure, and water in the cavity 3 is discharged at the same time, as shown in figure 1. After grouting is finished, the drill rod 6 is taken out, and the heat insulation material is prevented from seeping out due to the existence of the grout stop plug. And curing and forming the heat-insulating material to form the heat-insulating layer 3 after 2-3 days.

And after the structure of the heat-insulating layer is stable, removing the two grout stop plugs and the mortar layer between the two grout stop plugs, and finishing the manufacture of the heat-insulating layer 3, as shown in the attached figures 3 and 4.

The heat-insulating mortar is inorganic heat-insulating mortar, inorganic vitrified micro-beads (also called closed-cell expanded perlite) are used as light aggregate, and dry powder mortar consisting of cementing material, anti-cracking additive and other fillers is added.

Finally, it should be noted that: the above embodiments are only used for explaining the technical solution of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the constructor can modify the technical solutions described in the foregoing embodiments, or equivalently replace some or all of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims

1. A geothermal well wellbore thermal insulation structure and construction method thereof, characterized in that: the thermal insulation structure comprises a thermal insulation central pipe (1), a casing (2) and is sandwiched between the thermal insulation central pipe (1) and the casing (2). The thermal insulation layer (3), the construction method of which comprises the following steps: after the completion of the wellbore construction, install a slurry stopper (4) at the depth h of the casing (2), and set a center pipe stopper at the bottom of the thermal insulation center pipe (1). The slurry plug (5), the center pipe slurry stopper (5) is provided with a hole just enough to accommodate the drill pipe (6); the insulating center pipe (1) is lowered to a depth of h, and the center pipe slurry stopper (5) It is located above the pulp stopper (4), and there is a gap between them. After the installation of the thermal insulation central pipe (1) is completed, an annular cavity (3) is formed between the thermal insulation central pipe (1) and the casing (2). to extend the bottom of the drill pipe (6) through the hole of the central pipe slurry stopper (5) into the gap between the central pipe slurry stopper (5) and the slurry stopper (4), and the thermal insulation mortar passes through the drill pipe (6). ) first enters the gap between the two grouting plugs and then enters the cavity (3), and by adjusting the grouting pressure, the insulating mortar fills the cavity (3) from bottom to top, and at the same time, the liquid in the cavity (3) is filled. After the thermal insulation structure is stabilized, the two slurry stoppers and the mortar layer formed in the gap between the two slurry stoppers are removed, and the thermal insulation mortar connects the thermal insulation central pipe (1) and the casing (2) to form an thermal insulation layer (3).

2. A geothermal well wellbore thermal insulation structure and construction method thereof according to claim 1, characterized in that: during the process of lowering the thermal insulation central pipe (1), a limit device (7) is arranged on the periphery of the pipe every other distance. .

3. A geothermal well bore insulation structure and construction method thereof according to claim 1 or 2, wherein the depth h is determined according to the on-site geological conditions and formation temperature factors.

4. A geothermal wellbore insulation structure and construction method thereof according to claim 1 or 2, characterized in that: the thickness of the insulation layer (3) is 50mm-60mm, and the thermal conductivity of the insulation mortar is not greater than 0.1W/m·K.

5. A geothermal wellbore thermal insulation structure and construction method thereof according to claim 1 or 2, wherein the thermal insulation central pipe (1) is provided with an anti-corrosion coating, and the thickness of the anti-corrosion coating is 0.1-4 mm.