JPH0420077B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a well support method in which a fractured portion (fracture space) of the ground adjacent to a well is supported with a hydration-swellable material and has a high degree of permeability.

Since the 1940s, when hydraulic fracturing of the ground adjacent to oil wells began to be carried out, solid granular propping agents have been added to such fractures to prevent them from becoming blocked by ground pressure. ) has been adopted.

However, in this conventional method, the granular support material collapses due to the pressure of the underground plate, or the support material is buried underground and the fractured part becomes clogged, causing damage to the underground layer. The drawback was that the amount of fluids contained therein, such as oil or gas, could be reduced over time. Similar problems also existed in geothermal wells that sample hot fluids. Therefore, there has been a strong demand for improvement of these drawbacks.

The present invention was achieved as a result of intensive studies in view of the above circumstances, and the first invention is an oil well,
In order to prevent blockage of the fractured parts of the ground adjacent to wells such as geothermal wells that have been fractured by hydraulic power, etc., a slurry of water and substances that expand in volume through hydration reactions, such as quicklime, calcined dolomite, and magnesia, is used. This well support construction method is characterized in that a mixture is injected or press-fitted into the fractured part, and the fractured part is supported by the hydration expansion force of the substance and is made highly permeable.

Next, the second invention of the present invention provides a well in which a slurry mixture of water and a substance that expands in volume through a hydration reaction is further mixed with a hydration reaction retarder in the first invention. This is a support method.

Quicklime, calcined dolomite and magnesia used in the present invention are CaO and CaO+, respectively.
It is composed of MgO and MgO, and undergoes a hydration reaction according to the chemical reaction formula shown below, causing volume expansion.

CaO + H ₂ O → Ca (OH) ₂ MgO + H ₂ O → Mg (OH) ₂ And in the present invention, as mentioned above, a substance that expands in volume through a hydration reaction (used in powder form) and water (if necessary) are used. In order to inject or pressurize a slurry-like mixture with a hydration reaction retardant) into the fractured part of the hydraulically fractured ground, the volume of the above substance expands in the fractured part due to a hydration reaction, and the underground pressure increases. This prevents the crushed portion from clogging. It also encourages the expansion of fractured parts and the formation of new cracks.

Furthermore, the hydration products of substances such as quicklime, calcined dolomite, and magnesia, which expand in volume through hydration reactions, are not compact unlike the hardened bodies of hydraulic substances such as Portland cement, so they cannot be easily absorbed from underground layers. Forms the necessary connections for fluids. Therefore, it has a high degree of permeability to fluids such as oil, gas, and water vapor.

In the present invention, when using a substance that undergoes a rapid hydration reaction such as soft calcined lime, it is difficult to inject or press into the fractured part of the ground, so it is necessary to add a hydration reaction retarder as described above. Therefore, the hydration reaction of the substance can be delayed and injection or press-fitting into the crushed portion can be facilitated.

In addition, in the case of hard calcined quicklime, even if it comes into contact with water, it does not immediately undergo a hydration reaction. Since quicklime, calcined dolomite, and magnesia have different hydration reactivity depending on their type and particle size, a retarder is used depending on the state of the hydration reaction. Further, by selecting the type and amount of the hydration reaction retarder, the injection or press-in operation time can be adjusted.

As the hydration reaction retarder, sugars, polyhydric alcohols, borates, gypsum, etc. are preferably used. The appropriate amount of these additions will vary over a wide range for this reason alone, as well temperatures vary widely, but typically sugars and polyalcohols are added to hydration-swelling substances such as quicklime. 0~
About 3wt%, borate and gypsum about 0 to 30wt%. Note that these retarders are used by being mixed in advance with either quicklime or mixed water.

Further, in the present invention, water is used in an amount equal to or slightly larger than the stoichiometric amount for the hydration reaction.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A plain concrete specimen 1 with a side of 1 m cube was cut using a cutter machine (equipped with a diamond blade) to form a kerf 2 as shown in Figure 1. The pressure inside the plate is in the direction of the arrow that closes the fractured part, as shown in Figure 2.
A test was conducted to observe the clogging of the kerf 2 by applying a pressure of 2000 t/m ² .

CaO made by calcining limestone at 1500℃ for 3 hours in an electric furnace
Grind hard calcined lime with crystal grains of 30 to 100μ, and
A kneaded material 3 (slurry) having a particle size of 100 mesh and 30 wt% of water added thereto was poured into the kerf 2 and left for 1 hour. When pressure was applied in the direction of the arrow as described above and observation was made one month later, it was found that the kerf 2 was not closed, but rather was expanded, and cracks 4 had occurred in the uncut portion.

For comparison, when the above test was carried out by filling the kerf 2 with glass beads having an average particle diameter of 10 μm, more than half of the kerf 2 was crushed, and the glass beads were significantly broken.

Example 2 A cut groove 2 was formed using the same concrete specimen 1 as in Example 1, and a test was conducted assuming a fractured portion in the ground.

CaO made by calcining limestone at 1500℃ for 3 hours in an electric furnace
Hard calcined lime with crystal grains of 30 to 100μ is crushed and
Quicklime with a particle size of 500mesh was prepared. Unreinforced concrete specimen 1
The solution was injected into the kerf 2 and left for 2 hours. Then, as in Example 1, pressure was applied in the direction of the arrow, and when this pressure was maintained for one month, observation was made, and it was found that the kerf 2
The kerf 2 was not closed, but rather the kerf 2 was expanded, and a crack 4 had occurred up to the uncut portion.

[Brief explanation of drawings]

Figure 1 is a perspective view of a specimen assuming a fractured portion in the ground according to the present invention, and Figure 2 shows the state of the test results using the specimen of Figure 1. 1... Plain concrete specimen, 2... Cut groove, 3...
a slurry-like mixture of a substance that expands in volume through a hydration reaction and water (or further a hydration reaction retarder);
4...Crack.

Claims (1)

[Scope of Claims] 1. In order to prevent blockage of a fractured part of the ground adjacent to a well such as an oil well or a geothermal well, which is fractured by hydraulic power or the like,
A slurry-like mixture of water and a substance that expands in volume through a hydration reaction, such as quicklime, calcined dolomite, or magnesia, is injected or press-fitted into the fractured part, and the fractured part is supported by the hydration expansion force of the substance. This well support construction method is characterized by providing a high level of permeability to the well. 2. In order to prevent blockage of the fractured parts of the ground adjacent to oil wells and geothermal wells that have been fractured by hydraulic power, hydration reactions with substances that expand in volume through hydration reactions, such as quicklime, calcined dolomite, and magnesia, are used. A slurry-like mixture of a retarder and water is injected or press-fitted into the fractured part, and the fractured part is supported by the hydration expansion force of the substance and is made to have a high degree of permeability. Well support method.