JPH0345193B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is applicable to deep borehole drilling such as geothermal power generation drilling, oil drilling, mineral resource drilling, and various resource exploration drilling, in which circulating mud for drilling is removed from the hole wall. This article relates to a construction method for preventing water loss in deep boreholes that prevents water from escaping.

"Prior art" The state of deep boring is as shown in Figure 2, where 1 is the casing and 2 is the casing 1.
With a drill rod that penetrates through the drill rod, circulating mud for drilling is injected into the bottom of the hole from the tip through the hollow core of the drill rod 2, filling the hole 3, and being collected in a tank 4 on the ground. Note that arrow 5 in the figure indicates lost water.

Conventional water loss prevention methods include the following.

() Method by adjusting the concentration of muddy water This method is a construction method that seals the diversion layer (cracks) by increasing the concentration of muddy water.

() Method using cement grout This method involves pouring cement grout alone or cement grout mixed with wood chips, straw, etc. into a deep borehole to prevent water loss.

() Method of injecting chemicals through a hose This method involves injecting a water-stopping chemical that gels in water using an injection hose lowered to a predetermined depth (water leakage point).

() Method of injecting chemical liquid through a rod This method is a method in which a water stop chemical liquid that gels in water is injected using an injection rod that is lowered and replenished to a predetermined depth (water loss area).

() Method of injecting a water-stopping chemical using a capsule This method is a method in which a water-stopping chemical is set in a capsule at a predetermined gel time and is lowered to a predetermined depth (water stoppage layer), then the capsule ruptures to stop water. be.

() Chemical pouring method This method involves pouring a water stop chemical in liquid or granular form from the mouth of the borehole.

``Problems to be solved by the invention'' However, the conventional construction method described above has the following problems.

In other words, the above-mentioned method () is advantageous because it allows the drilling rod to remain in place, but since the mud particles are not as large as gelled materials, it is not effective when the crack width is large or water loss is severe. There is no. In addition, if the concentration becomes too high, it has the disadvantage of collapsing the weak pore walls other than the areas where water is lost (because it adheres only to the surface of the pore walls without penetrating into the walls).

Method () is advantageous because it allows the drilling rod to remain in place, but it takes a long time for the cement to harden (8 to 10 hours), so it takes time to stop the water, and it It adheres to wall surfaces and is difficult to penetrate, causing a series of excavation systems to stop working for a few days or even several dozen days in cases of severe water loss.
In addition, circulating mud water is wasted and tens of tons of cement are used. Furthermore, cement has poor permeability, so re-excavation will cause the hole wall to collapse.

For methods () to (), the excavation rod must be raised, so it takes time to raise and lower the rod (5 to 10 hours depending on the depth).
There is a problem because it takes

If the drilling rod is not pulled up, use a strong chemical solution to prevent the drilling rod from moving. Chemical solutions with weak strength are ineffective.

Looking further at each individual method, in the construction method (),
If it is difficult to lower the injection hose (it gets twisted) and it gets too deep, there will be a loss of chemical solution (inside the hose). In method (), it takes time to lower the injection rod, and due to the strength of the rod, it can only be done for a distance of about 700 m, resulting in a loss of chemical solution. The method () has the inconvenience that it is not possible to descend to a predetermined depth and destroy the capsule reliably and safely, and that it is not possible to continuously supply a predetermined amount.

With the method in parentheses, it is unclear whether the chemical will reach the specified depth. The deeper the depth, the greater the loss of chemical solution.

``Means for Solving Problems'' and ``Operations'' The present invention was made in view of the above circumstances, and its gist is to interrupt the circulation of muddy water in the drilling rod when water leakage occurs. Then, a piece of Japanese paper impregnated with cement, water glass, or a gel-like material of polyethylene glycol methacrylate is sealed as a spacer in the drilling rod, and then a spacer containing an isocyanate compound that has the property of gelling by causing a hydrolysis reaction is used as the main component. A predetermined amount of grout is press-fitted, and then the spacer is re-enclosed to form a grout-filled bed partitioned from the top and bottom by spacers inside the drilling rod. After that, mud water circulation is restarted and the grout is placed in the water-losing area. Assuming that we supply up to
While the drilling rod remains in place, the grout, which has a high risk of gelling during descent, is poured out from the tip of the drilling rod at the point where it first comes in contact with water without causing gelling. The point is that we have provided a construction method to prevent water leakage under the highest conditions.

"Example" This will be explained in detail below based on the figures.

FIGS. 1a to 1e are explanatory diagrams of the procedure of the construction method of the present invention. Due to the occurrence of water leakage, the mud water circulation is interrupted and the drilling rod 2 is moved to the tricomb bit 2a at the tip of the drilling rod.
20 to prevent it from being buried in compacted soil and becoming unable to be driven again.
Raise it ~50m (Figure a).

Insert a 20-50m advance spacer 6 into the drilling rod 2 (Figure b).

The spacer 6 is made of a gel-like material that can leak through the small holes of the tricomb bit 2a, such as a piece of Japanese paper impregnated with cement, or a gel material of water glass or polyethylene glycol methacrylate.

Next, grout 7 is press-fitted via a pump or the like (Figure c).

The grout 7 is mainly composed of an isocyanate compound that has the property of causing a hydration reaction and gelling, and the entire amount of the injected grout causes a hydration reaction and gels without waste while maintaining its permeability. do. Therefore, in principle, it cannot occur that it is diluted with groundwater or washed away, resulting in incomplete gelation or groundwater contamination. In other words, when the isocyanate compound, which is the main component of grout, comes into contact with underground pore water, it reacts as shown in the following equation, generating carbon dioxide gas and
Create a polyurea gel that is completely insoluble in water.

That is, This polyurea is a hydrophobic, non-hydrophobic gel with a three-dimensional structure that strongly bonds between soil particles, creating strong compacted soil.

In addition, the carbon dioxide gas generated during the water addition reaction is dispersed in the grout as minute bubbles, and the grout expands its apparent volume and permeates into the soil manually, making the amount less than the actual amount used. to create a much larger volume of compacted soil.

In addition, by this active expansion and infiltration, even if the groundwater is in a state of water movement, it is possible to reliably solidify the ground at the target location while eliminating its influence.

Water stoppage can be ensured by adding such a strong soil forming agent.

The amount of grout 7 varies depending on the water loss situation, but 200 to 1000 kg is added.

After grout 7, add trailing spacer 6' 20~50
After pouring cement milk or mortar depending on the water loss situation, the circulation of the muddy water 8 is restarted, and the grout 7 that has been lowered inside the drilling rod 2 is directed to the water loss location through the opening of the trichome bit 2a. Pour it out (Figure d).

In the above, the preceding spacer 6 pushes out the muddy water in the rod and separates the grout 7 from the muddy water,
The trailing spacer 6' demarcates the recirculating mud 8 which backs up the grout 7.

The leading spacer 6, the grout 7, and the trailing spacer 6' are discharged in this order from the opening of the trichome bit 2a, and the grout 7 is supplied even when it comes into contact with water for the first time at this water leakage point, so it is The inconveniences of solidification and clogging of the openings of the tricomb bit 2a due to solidification are avoided.

If the water does not stop after one time, repeat the above steps. When the water has stopped, the excavation rod 2 is lowered and excavation is resumed (Fig. e).

The figure is drawn in the case of extremely shallow water loss where the leading spacer 6 reaches the tricone bit 2a when the trailing spacer 6' is enclosed.

"Effects of the Invention" The various effects of the present invention described above are listed below.

(1) There is no need to raise the drilling rod to the ground.

(2) It takes 700~ to raise the drilling rod to the ground.
It takes more than 5 hours to reach a depth of 1000m. or,
The same amount of time is required to descend, but this method does not require this.

(3) Since there is no need to raise the drilling rod to the ground, if water leakage occurs, it can be immediately stopped, and there is no waste of muddy water.

(4) No need for injection rod, injection hose or injection capsule.

(5) Lower costs.

[Brief explanation of drawings]

Figures 1 a to e are explanatory diagrams of the procedure of the construction method of the present invention, and Figure 2
The figure is an explanatory diagram of the water loss situation. 1...Casing, 2...Drilling rod, 2a...
...tricone bit, 3...hole, 4...tank, 5
...Itsui, 6... Spacer, 7... Grout,
8...Muddy water.

Claims (1)

[Claims] 1 When water leakage occurs, the circulation of mud in the drilling rod is interrupted, and a piece of Japanese paper impregnated with cement, water glass, or a gel-like material of polyethylene glycol methacrylate is sealed in the drilling rod as a spacer, and then the water addition reaction is started. A predetermined amount of grout whose main component is an isocyanate compound that has the property of causing gelling is injected into the drilling rod, and the spacer is then re-enclosed to form a grout-filled bed partitioned from the top and bottom by spacers inside the drilling rod. ,
A method for preventing water loss in deep boreholes, which is characterized in that the circulation of mud is then restarted to supply grout to the location of water loss.