JP2023005190A - Well construction method - Google Patents

Abstract

A method for constructing a well that removes a mud film formed in a hole formed by drilling, eliminates variations in the ground, and can exhibit the original stable performance of the well. A method for constructing a well according to the present embodiment is a method for constructing a well in the ground G, wherein the hole is drilled while injecting a stabilizing liquid containing bentonite or natural clay. A drilling step of forming holes 11 in the ground G while forming a mud film on the wall, and injecting a dispersion liquid containing a dispersant into the holes 11 to settle the earth and sand contained in the muddy water in the holes 11. a diluting step, a replacement step of replacing the stable liquid in the pores 11 with a solution containing a polymer thickener to form a polymer film made of the polymer thickener on the pore walls, and cutting the mud film. It has a removing step and a washing step of washing the inside of the hole 11 to remove the polymer film. [Selection drawing] Fig. 1

Description

The present invention relates to a well construction method.

Conventionally, deep wells and recharge wells are made by inserting a casing with a screen at the bottom into a well hole drilled while preventing the collapse of the pore wall using a stabilizing liquid, and filling the outer circumference of the screen with granular filter material (silica sand, etc.). It is chiseled. After drilling the well, the stable liquid and groundwater in the well are pumped up to wash the inside of the well.
As a stabilizing liquid, bentonite mud (rotary method), natural clay dispersion (percussion method), etc. are used. Such a stabilizing liquid effectively acts to stabilize the hole wall during drilling. On the other hand, if the mud film formed by the stable liquid remains on the ground and the filter material after the construction of the well, it blocks the water path and reduces the pumping/injection performance of the well. After drilling a well, groundwater is pumped up and washed, but this washing does not completely remove the bentonite mud film or the natural clay mud film. The remaining mud film on the borehole wall is a major cause of well loss.

A well drilling method using a biodegradable polymer instead of bentonite mud or the like as a stabilizing liquid is known (see, for example, Patent Document 1). However, this drilling method is not popular among general drillers because it is costly and difficult to manage and handle the stable liquid during drilling.

JP 2015-83732 A

In the excavation method of Patent Document 1, when the viscosity of the stable liquid containing the biodegradable polymer is high, shavings of the drilled ground (hereinafter referred to as "slime") and muddy water are sufficiently separated by the slime separator. It was not possible (mud water stopped circulating in the hole and the tank, and the quality of the mud water could not be maintained). On the other hand, if the viscosity of the stabilizing liquid containing biodegradable polymer is low, the pebbles in the gravel layer in the ground will not rise to the ground surface, and it takes a long time to drill holes.

The present invention has been made in view of the above circumstances, and is capable of removing the mud film formed in the hole formed by drilling, eliminating variations in the ground, and exhibiting the original stable performance of the well. The purpose is to provide a construction method for

The present invention has the following aspects.
[1] A well construction method for constructing a well in the ground, wherein a stable liquid containing bentonite or natural clay is injected into the hole while drilling to form a mud film on the wall of the hole, and A drilling step of forming a hole, a dilution step of injecting a dispersion containing a dispersing agent into the hole to settle the sediment contained in the muddy water in the hole, and the stable liquid in the hole, Substitution step of substituting with a solution containing a polymer thickener to form a polymer film made of the polymer thickener on the pore wall, removal step of cutting the mud film, and cleaning the inside of the hole and a cleaning step of removing the polymer film.
[2] The well construction method according to [1], wherein the polymer thickener is a biodegradable polymer.
[3] The well construction method according to [2], wherein in the cleaning step, a cleaning liquid containing an enzyme capable of decomposing the biodegradable polymer is injected into the hole to clean the inside of the hole.

According to the present invention, it is possible to provide a method for constructing a well that removes the mud film formed in the hole formed by drilling, eliminates unevenness in the ground, and exhibits the stable performance inherent in the well.

It is a schematic diagram which shows an example of the construction method of the well by embodiment of this invention. It is a schematic diagram which shows an example of the construction method of the well by embodiment of this invention. It is a schematic diagram which shows an example of the construction method of the well by embodiment of this invention. It is a schematic diagram which shows an example of the construction method of the well by embodiment of this invention.

A well construction method according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG.
1 to 4 are schematic diagrams showing an example of a well construction method according to an embodiment of the present invention.
It should be noted that the present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified.

[Well construction method]
The method of constructing a well according to the present embodiment is a method of constructing a well in the ground, and drilling is performed while injecting a stable solution containing bentonite or natural clay to form a mud film on the hole wall. A drilling step of forming holes in the ground while forming, a dilution step of injecting a dispersion containing a dispersant into the holes to settle the earth and sand contained in the muddy water in the holes, and the holes A replacement step of replacing the stabilizing liquid inside with a solution containing a polymer thickener to form a polymer film made of the polymer thickener on the pore wall, and a removing step of cutting the mud film and a cleaning step of cleaning the inside of the pores and removing the polymer membrane.

In this embodiment, the well 1 shown in FIG. 4 is constructed on the ground G having an embankment layer, a cohesive soil layer and an aquifer.

(drilling process)
As shown in FIG. 1, in the drilling process, a liquid feed pump 21 for circulating muddy water in the hole 11 is installed on the ground surface (the surface of the ground G).
In the drilling step, a stable liquid containing bentonite or natural clay is injected by the liquid feed pump 21 while drilling. A hole 11 is formed.
In the drilling process, a positive circulation method using drilling mud containing a stabilizing liquid is used. As a drilling method, for example, a rotary drilling method using bentonite mud, a percussion drilling method using natural clay, and the like are used.

In the positive circulation method, drilling mud containing a stable liquid injected into the hole 11 fills the inside of the hole 11 and rises.
Due to the upward flow of drilling mud, earth and sand produced by drilling is carried to the mouth of the hole (the opening of the hole 11 on the surface of the ground G) 11a. Then, a separation device provided on the surface of the ground G separates earth and sand from the drilling muddy water containing earth and sand. The drilling mud from which the earth and sand have been separated is injected into the hole 11 again.

The stabilizing liquid is made by dissolving bentonite or natural clay in water (such as tap water or industrial water). When the stabilizing liquid contains bentonite, the stabilizing liquid is bentonite mud. If the stabilizing liquid contains natural clay, it is a natural clay dispersion.
The content of bentonite or natural clay in the stable liquid is preferably 10% by mass to 15% by mass, more preferably 5% by mass to 10% by mass, relative to the total mass (100% by mass) of the stable liquid.

(Dilution process)
In the dilution process, a liquid dispersion containing a dispersant that reduces the viscosity of the mud is injected into the holes 11 by the liquid feed pump 21 , thereby sedimenting the earth and sand contained in the mud within the holes 11 .
In the dilution step, a diluent is injected into the drilling mud stored inside the hole 11 . When the diluent is injected, the action of the dispersant reduces the viscosity of the drilling mud and promotes sedimentation of the earth and sand.
In the dilution step, the drilling mud is preferably diluted so that the specific gravity of the drilling mud is 1.05 to 1.10.

A diluent is made by dissolving a diluent in water. A diluent is an agent containing, as a main component, a dispersant (surfactant) that reduces the viscosity of mud. That is, when a diluent containing a dispersant is injected into muddy water, the viscosity of the muddy water is lowered, sedimentation of the sediment occurs, and the concentration of sediment in the supernatant can be reduced.

Examples of dispersants include synthetic dispersants and natural dispersants.
As the synthetic dispersant, for example, a polycarboxylic acid-based dispersant having a carboxyl group, specifically a polyacrylate such as sodium polyacrylate, is preferably used.
As the natural dispersant, for example, a lignin-based dispersant is used.

After sedimentation of the earth and sand contained in the drilling mud, the earth and sand (slime) collected at the bottom of the hole 11 is discharged. For example, a bucket for bottom dredging is used to remove accumulated earth and sand.

(Replacement step)
As shown in FIG. 2, in the replacement step, the liquid feed pump 21 replaces the stable liquid in the holes 11 with a solution containing the polymer thickener, and the polymer film made of the polymer thickener is formed in the holes 11 . formed on the pore walls of
In the replacement step, the polymer thickener is dissolved in water (tap water, industrial water, etc.) to prepare a polymer solution, and the polymer solution is injected into the holes 11 to stabilize the holes 11. Replace the liquid with the polymer solution.

Although the polymeric thickener is not particularly limited, biodegradable polymers are preferable from the viewpoint of being decomposed by bacteria in the ground. Examples of biodegradable polymers include semi-synthetic polymers and biopolymers.

Semi-synthetic polymers are compounds obtained by chemical synthesis using natural resources as starting materials. As the semi-synthetic polymer, for example, a cellulose-based polymer obtained using cellulose, which is a type of natural resource, as a starting material can be used. Examples of the cellulosic polymer include carboxymethyl cellulose (CMC) introduced with carboxymethyl groups, methyl cellulose (MC) introduced with methyl groups, and hydroxyethyl cellulose (HEC) introduced with hydroxyethyl groups.

Carboxymethylcellulose is an anionic polymer. Methylcellulose and hydroxyethylcellulose are nonionic polymers.

Biopolymers are compounds obtained from secretions from microbial activity. Biopolymers include, for example, thickening polysaccharides such as xanthan gum, chitosan, and polysaccharides.

The content of the polymer thickener in the polymer solution is preferably 3% by mass to 8% by mass, more preferably 3% by mass to 5% by mass, relative to the total mass (100% by mass) of the polymer solution.

The viscosity of the polymer solution before injection into the holes 11 is preferably 50 to 60 seconds, more preferably 50 to 55 seconds, in terms of funnel viscosity.
The funnel viscosity is the viscosity of muddy water measured by the following method using a funnel viscometer.

(Method for measuring funnel viscosity)
Support the funnel body so that it stands vertically with the attached tripod, and put a lid with a metal fitting on the top.
Muddy water is collected to the brim with a muddy water collection container (500 mL).
The outflow port at the bottom of the funnel body is closed with the index finger, and the mud sample collected by the mud sampler is poured into the funnel body from above.
Place the collection container below the outlet on the bottom of the funnel body.
Release the finger blocking the outlet at the bottom of the funnel body and measure the time (seconds) for the muddy water to flow out.
The measurement results are expressed in seconds (500 mL/500 mL) with muddy water viscosity as funnel viscosity.

The viscosity of the polymer solution after injection into the holes 11 is preferably 25 to 40 seconds, more preferably 20 to 30 seconds, in terms of funnel viscosity. When the funnel viscosity is equal to or higher than the lower limit, collapse of the hole walls of the holes 11 can be suppressed. If the funnel viscosity is equal to or less than the upper limit, workability is improved in the removal step described below.

In the replacement step, by replacing the stable liquid in the pores 11 with a solution containing a polymer thickener, it is possible to prevent the walls of the pores 11 from collapsing due to peeling of the mud film. The mud film is necessary to hold the hole wall during drilling.

(Removal process)
As shown in FIG. 3, in the removing step, the mud film formed on the inner surface of the hole 11 is cut and removed.
In the removing step, the method of cutting the mud film is not particularly limited, but for example, a method of mechanically cutting the mud film is preferable.

In the method of mechanically cutting the mud film, for example, as shown in FIG. 3, a removing device 31 called a bit is used. The mud film is cut by moving the removal device 31 in the depth direction of the hole 11 while contacting the hole wall of the hole 11 . As a result, the inner diameter of the hole 11 is increased (widened). Therefore, most of the mud film on the hole wall of the hole 11 is removed, and the water path in the well 1 is not clogged by the mud film.
The amount of scraping off the mud film is not particularly limited, but for example, the diameter of the hole 11 may be widened from about 600 mm to about 1000 mm. By widening the diameter of the hole 11, the pumping/injection performance of the well can be further improved.

In addition, after the well 1 is completed, the mud film is removed because it causes loss of the well. In addition, since a polymer film made of a polymer thickener is formed on the pore walls, the pore walls do not collapse even when the mud film is removed.

Next, as shown in FIG. 4, a cylindrical casing 41 is installed in the hole 11. As shown in FIG. The casing 41 may be, for example, a steel casing to which a wire wound screen is welded.
Also, a pump 42 is installed at the lower end of the casing 41 .
Furthermore, a pumping pipe 43 extending from the pump 42 to the hole mouth 11a of the hole 11 is installed.

Next, a filter material 51 such as crushed stone is filled between the casing 41 and the inner surface of the hole 11 .
Next, a water impermeable material 52 such as OK bentonite or granular bentonite is placed on the upper surface of the filter material 51 (the surface on the surface side of the lot number G).

(Washing process)
After the installation of the casing 41 and the filter material 51 is completed, a cleaning process is performed.
In the cleaning step, the inside of the hole 11 is cleaned with a cleaning liquid to remove the polymer film inside the hole 11 .

In the cleaning step, a cleaning liquid is injected into the polymer solution in the holes 11 . Here, the washing liquid is injected into the polymer solution in the hole 11 via the pumping pipe 43 .
The injected washing liquid diffuses into the filled area of the filter material 51, passes through the gaps of the filter material 51, and reaches the pore walls. As a result, the enzyme (cellulase) contained in the cleaning liquid decomposes the biodegradable polymers (carboxymethylcellulose, xanthan gum) contained in the polymer solution and the biodegradable polymers adhering to the pore walls and the filter material 51 .

After a waiting time required for decomposition of the biodegradable polymer has passed, the drilling mud pooled in the hole 11 is pumped up. At this time, the decomposition product of the biodegradable polymer by the enzyme is also pumped up together with the drilling mud. Since groundwater flows in as drilling mud is pumped up, the hole walls, the surface of the filter material 51, and the casing 41 are washed.
Then, after each part is sufficiently washed with groundwater (for example, after the water pumped up by the pump 42 becomes clean), the washing process is completed.

A cleaning liquid is made by dissolving a cleaning agent in water.
Detergents are agents containing enzymes capable of degrading biodegradable polymers. That is, when a washing solution containing this enzyme is injected into muddy water after sedimentation of earth and sand, the biodegradable polymer contained in this muddy water is decomposed by the enzyme. In the upper part of the muddy water, the amount of sediment has decreased due to sedimentation, and the viscosity of the muddy water has decreased. Therefore, the enzyme can efficiently decompose the biodegradable polymer.
Enzymes secreted by cellulolytic bacteria, specifically cellulases, can be used as detergents.

After the cleaning process is completed, a finishing process is performed.

According to the well construction method of the present embodiment, by drilling while injecting a stabilizing solution containing bentonite or natural clay, the drilling step of forming the hole 11 in the ground G and the viscosity of the muddy water are reduced. By injecting a diluted solution containing a dispersant into the holes 11 to settle the sediment contained in the muddy water in the holes 11, the stable liquid in the holes 11 is added to the solution containing the polymer thickener Because it has a replacement step of replacing, a removing step of removing the mud film formed on the pore walls of the pores 11, and a cleaning step of cleaning the inside of the pores 11 and removing the polymer thickener in the pores 11 , the ground G is eliminated, and the well 1 capable of exerting its original stable performance can be constructed.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Each configuration and combination thereof in the above-described embodiment are examples, and addition, omission, replacement, and other modifications of the configuration are possible without departing from the scope of the present invention.

1 well 11 hole 21 liquid sending pump 31 removing device 41 casing 42 pump 43 pumping pipe 51 filter material 52 waterproof material

Claims (3)

A well construction method for constructing a well in the ground,
A drilling step of forming a hole in the ground while forming a mud film on the hole wall by drilling while injecting a stable solution containing bentonite or natural clay;
A dilution step of injecting a dispersion containing a dispersant into the holes to settle sediment contained in the muddy water in the holes;
a replacement step of replacing the stabilizing liquid in the pores with a solution containing a polymer thickener to form a polymer film made of the polymer thickener on the pore walls;
a removing step of cutting the mud film;
and a cleaning step of cleaning the inside of the hole and removing the polymer membrane. The method of constructing a well according to claim 1, wherein the polymeric thickener is a biodegradable polymer. 3. The well construction method according to claim 2, wherein in said cleaning step, a cleaning liquid containing an enzyme capable of decomposing said biodegradable polymer is injected into said holes to clean said holes.

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