JPH0480195B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a geothermal production well for effectively utilizing geothermal energy, and particularly relates to a geothermal production well that is less prone to scaling and a method for drilling the same. It is something.

[Conventional technology]

FIG. 2 is a diagram showing a cross section of a conventional geothermal production well, and FIG. 3 is a diagram for explaining a general production well drilling method. In the figure, 1 is the conductor casing, 2 is the anchor casing 2, 3 is the production casing, 4 is the ground surface, 5 is the cementing, 6 is the geological formation, 11 is the mud pump, 12 is the stand pipe, and 13 is the rotary hose. , 14 is swivel, 15 is kelly, 16 is drill pipe,
17 is a drill collar, 18 is a bit, 19 is a ditch, 20 is a mud screen, 21 is a suction tank, 22 is a rotary table, 2
3 each indicates a seller.

Methods for drilling production wells include muddy water drilling, fresh water drilling, air drilling, etc., and FIG. 3 shows an example of muddy water drilling. When drilling a production well using mud drilling, first, drill collar 1 is attached to bit 18.
Connect 7 and Kelly 15 and descend to cellar 23
Start excavating from the bottom of the Drilling is carried out by rotating the rotary table 22 and rotating the bit 18 through the Kelly 15 while using the drill collar 17.
This is done by gradually applying the same weight to the bit 18. At the same time, on the other hand, the muddy water pump 11 is operated to circulate muddy water. For muddy water, use muddy water pump 11
It is sucked in from the suction tank 21 and sent under pressure, passing through an above-ground pipe to the stand pipe 1.
2. Sprayed from the nozzle of the bit 18 through the inside of the rotary hose 13, swivel 14, kelly 15, and drill collar 17. This muddy water then rises between the outside of the drill pipe 16 and the tunnel wall (annulus) containing cuttings cut by the blade of the bit 18, and flows from the vertical pipe and horizontal pipe into the ditch trough 19. Street Matsudo Screen 2
At 0, the cuttening is removed and suction tank 2
Return to 1. This creates a continuous circulation system between the muddy surface and the inside and outside of the mine. When the excavation is carried out to a predetermined depth as described above, the excavation is stopped and the muddy water continues to circulate for a while to lift the cutlets contained in the muddy water inside the mine to the surface of the ground.Afterwards, when the inside of the mine is clean, the pipe is lifted. . The casing is then lowered and cemented.

The geothermal production wells drilled as described above are used to protect the soft strata near the ground surface, to block groundwater, and to serve as a base for installing blowout preventers, as shown in Figure 2. The conductor casing 1 to be set, the anchor casing 2 to the production casing 3 were all fixed with cementing 5.

Production wells are drilled for the purpose of extracting hot water from geothermal reservoirs that have already been discovered through various surveys, but they require a sturdy finish that will allow continued extraction of steam and other materials for as long as possible. As mentioned above, the earth is excavated, the excavation debris is removed, and then the casing is inserted and cemented. In particular, it is necessary that the insertion casing be completely cemented, and that the above-ground wellhead equipment have sufficient durability.

[Problem that the invention seeks to solve]

In the above-mentioned geothermal production well, one of the major problems is the occurrence of scaling, and the occurrence of this scaling is mostly concentrated in the deformed uneven portions of the production casing. This deformation of the production casing is caused by moisture penetrating into the voids in the mortar in that area, which expands due to geothermal heat and compresses the casing. However, in general, when the hardening of mortar is accelerated by the action of reaction heat and geothermal heat, it is difficult to integrate the mortar and the casing due to its rapid contraction, and moreover, in most cases, cracks occur between them. For this reason, the current situation is that it is difficult to eliminate voids in fixed mortar.

The present invention is based on the above invention, and includes:
The objective is to provide a geothermal production well that prevents casing deformation and scaling.

[Means for Solving the Problems] To this end, the present invention provides a geothermal production well for effectively utilizing geothermal energy, which includes a conductor.
The casing and anchor casing portions are fixed by cementing, and the production casing portion is loosely fitted without cementing, and a slow-hardening cement is used for the cementing.

[Effect]

In the geothermal production well of the present invention, since the production casing is non-cemented, there is no deformation of the production casing. Furthermore, since the conductor casing is cemented using slow-hardening cement, the occurrence of cracks during hardening is prevented. Therefore, it becomes possible to prevent scaling caused by deformation of the casing, which could not be avoided in the past.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining a shallow geothermal production well which is an embodiment of the geothermal production well and drilling method according to the present invention, and numerals 1 to 6 indicate the same ones as in FIG. 2, respectively.

In Figure 1, conductor casing 1
The anchor casing 2 is fixed with cementing 5 as in the conventional case, but the production casing 3 is loosely fitted without cementing. Therefore, in the production casing 3, although the casing was conventionally deformed due to the voids in the cement in order to be fixed by cementing, this effect is completely eliminated, and the cause of scaling is eliminated. Furthermore, cementing 5 when drilling a shallow geothermal production well is performed using cement that hardens slowly. As cementing to delay hardening, methods such as using fly ash cement, mixing a slow hardening agent, and using mortar with a reduced amount of cement can be adopted. By applying such slow-hardening cementing 5, it is possible to improve the conventional problem of cracks occurring due to rapid shrinkage due to cement curing heat and geothermal heating.

〔Effect of the invention〕

As is clear from the above explanation, conventionally, when cementing is used to fix the production casing, groundwater seeps into the cavities created by the shrinkage and aging of the cement, and is heated and expanded by geothermal heat, deforming the production casing. According to the present invention,
Since the production casing part is loosely fitted without cementing and the cementing is applied using a slow curing method, deformation due to the above factors is eliminated and scaling does not occur. Therefore, casing damage and clogging caused by scaling are eliminated, and geothermal production wells can be maintained for a long period of time.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining a shallow geothermal production well which is an embodiment of the geothermal production well and its drilling method according to the present invention, Fig. 2 is a diagram showing a cross section of a conventional geothermal production well, and Fig. 3 is a diagram for explaining a general production well drilling method. 1... Conductor casing, 2... Anchor casing, 3... Production casing, 4... Ground surface, 5... Cementing, 6...
... Geological formation, 11 ... Mud pump, 12 ... Stand pipe, 13 ... Rotary hose, 14 ...
Swivel, 15...Kelly, 16...Drill pipe, 17...Drill collar, 18...Bit, 19...Ditch gutter, 20...Matsudo screen, 21...Suction tank, 22...Rotary Table, 23...Cellar.

Claims (1)

[Claims] 1. A geothermal production well for the effective production and utilization of geothermal energy, in which the conductor casing and anchor casing parts are fixed by cementing, and the production casing part is fitted loosely with non-cementing. A geothermal production well characterized by the use of slow-hardening cement.