JPH0734770A - Top job/cementing method of well casing - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a casing by expansion of water content by placing and jointing concrete after hot fluid is supplied to the head section solidified in the middle course to eliminate water content in the case of cementing of a well such as a geothermal well, etc. CONSTITUTION:Concrete 9 lining a tunnel wall 8 is lost in the ground because of underground cracks 10, etc., steam or heated water is supplied in the vicinity of the head section 11 solidified in the middle course without reaching the ground surface through a geothermal fluid supply pipe 14, and water content in a circular gap section 12 is eliminated. After that, concrete is gradually filled in the circular gap section 12 between a surface casing 7 and a conductor casing 4 through a pipe 13, and cementing is made up-to the ground surface. According to the constitution, water content is not kept in the concrete, and the breakdown of the casing can be prevented in the case of production of the geothermal fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for top-job cementing a well casing, and more particularly, it is difficult to form voids in the cement head of the annular gap and no water remains in the annular gap. Therefore, we propose a method for top job cementing of well casing that can prevent the casing from being crushed when geothermal fluid is collected.

[0002]

2. Description of the Related Art Wells such as geothermal wells and oil wells have a casing made of steel pipe buried therein for the purpose of preventing the inflow of low temperature hot water and preventing the collapse of the well wall. Figure 2
Is a general geothermal well mine map (casing program). Conductor casing up to 90 m from the ground surface.
21 is buried, and inside thereof, a surface casing 22 that is buried to a depth of about 600 m is located. Further, inside the surface casing 22, a die-back casing that is in direct contact with a geothermal fluid that is a mixed fluid of steam and hot water ejected from an underground crack.
23 and liner 24 are buried to reach a depth of around 1500m. It should be noted that cement 25 is filled in the gaps between the casings 21, 22 and 23 and is fixed to each other. Further, the reference numeral 26 in the drawing is
It is a bare hole where the casing is not set, and is a part where geothermal fluid is sampled from underground cracks.

Conventionally, a two-plug type cementing method, a two-stage type cementing method, an inner string cementing method, a top-job cementing method and the like have been applied as a method of embedding and fixing each casing. The most commonly used two-plug type cementing method among the above-mentioned cementing methods will be described below. in this way,
First, inside the excavated well, with a centralizer etc.,
The above casings are inserted so as to leave an annular gap between the excavated well wall or another casing. Then, muddy water is injected into the casing to cool the well, and then a spacer (preceding liquid) is pressure-fed into the casing. Next, the first plug is inserted into the casing so that the cement slurry does not mix with the muddy water and the spacer at the time of pumping, the cement slurry is pumped into the casing, and then the second plug is inserted to insert the first plug. The cement slurry is sandwiched between the second plug and the second plug. Thereafter, by pumping muddy water from the above-ground portion to pressurize the second plug, the first plug arrives at the casing bottom portion, and at the same time, the casing and the casing or the casing from the cement feed hole provided in the first plug. It is a method of pushing the cement slurry into the annular gap between the tunnel wall and the pit wall and returning the cement slurry to the ground surface.

In the case of the casing cementing method by the two-plug type cementing method, it is usual that the cement pumped and filled in the casing returns to the surface of the earth through the annular gap portion, but some kind of obstacle such as underground cracking occurs. When the cement is lost to the ground due to its existence, there is a problem that it does not completely return to the surface of the earth and stops in the middle of the annular gap to form a cement head, which hardens as it is.

On the other hand, the above-mentioned top-job cementing method is a method developed to solve the problems of the above-mentioned two-plug type cementing method. This top-job cementing method is, as shown in FIG. 3, first, from the ground surface portion to the tip of the small diameter pipe 35 up to the vicinity of the cement head 34 of the cement 33 solidified in the annular gap portion between the casing 31 and the hole wall 32. Inserting and lowering, clean water is sent into the small diameter pipe to wash the annular gap portion, then cement slurry is pressure-fed from the pipe, and the small diameter pipe 34 is lifted when the cement slurry returns to the ground surface.
Is the method.

[0006]

In the above-mentioned prior art, a casing to be buried in a well generally has a coupling portion for connecting the casing and the casing protruding to the hole wall side, or the casing is Since the centralizer for setting in the center of the well is projecting to the hole wall side like the coupling part, there is a problem that only a pipe having a small diameter can be inserted into the annular gap part. Further, in these conventional methods, when the cement head is deep underground, a void cannot be uniformly filled with the cement slurry in the vicinity of the cement head, or water is present in this void. There is a problem in that the casing is fixed while it is still trapped, which causes various problems.

[0007] In particular, when water is trapped in the voids and the jet test or production of the geothermal fluid is started, the water expands due to the high temperature geothermal fluid, and the pressure pushes the casing into the inside of the well. There was a risk that the casing would crack and collapse.

When the casing is crushed, thereafter, logging equipment such as thermometer and pressure gauge and drilling equipment for repair cannot be hung down, or low temperature geothermal fluid flows in, In some cases, the temperature in the well decreased, and in the worst case, the geothermal fluid did not pass through the casing and directly ejected from the crushed part to the aboveground part near the well.

As a means for preventing such various problems, it has been conventionally considered to fill the annular gap with gravel or sand whose particle size has been adjusted and replace it with top job cementing. However, in such an alternative method, the casing cannot be tightly fixed, and another problem occurs such as the wellhead extending, and the life of the well being shortened due to the vibration due to the ejection of the geothermal fluid.

Therefore, an object of the present invention is to provide a technique for top job cementing which makes it difficult to form voids in the cement head of the annular gap and prevents water from remaining on the cement head. The purpose is to propose a top-job cementing method for well casings that does not cause casing collapse.

[0011]

[Means for Solving the Problems] As a result of earnest research to achieve the above-mentioned object, it was found that it is effective to use steam or hot water for the above-mentioned problems,
The method of the present invention as described below has been conceived. That is, the present invention, through the well casing, by pumping and filling the cement slurry into the annular gap between the casing and the well wall or another casing, when performing cementing of the annular gap, sludge, Due to accidents such as misrecognition of the temperature in the formation, miscalculation of the amount of cement and collapse in the mine,
In the top job cementing method of the well casing when the cement slurry is solidified on the way without returning to the surface of the earth, and the cement head is formed in the annular gap portion, in the vicinity of the cement head, After removing the geothermal fluid supply pipe through the inside of the well casing and supplying steam or hot water into the casing through the pipe to heat the inside of the well to remove water in the annular gap portion. The method is a top job cementing method for a well casing, which comprises feeding cement slurry into the annular gap.

[0012]

The top job cementing method according to the present invention is a cement head in which the cement slurry is solidified from the geothermal fluid supply pipe through the well before the cement slurry is fed into the annular gap portion from the small diameter pipe. This is a method in which the cement slurry is fed from a small diameter pipe after the water in the annular gap is evaporated and removed by supplying it to the vicinity of the portion. Therefore, according to such a method, since a void portion is unlikely to occur in the annular gap portion and water does not remain, even if a jet test or production of a geothermal fluid is started,
There is no possibility of crushing the casing.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an underground view for explaining the top job cementing method of the present invention. First, a well casing method up to the implementation of the top job cementing method of the present invention will be described with reference to FIG.

After excavating to a depth of about 50 m with a 24-inch bit and expanding to 34 inches, the conductor casing 1
Was embedded, and the annular gap between the pit wall 2 and the conductor casing 1 was filled with cement 3 and fixed. Then 24
The conductor casing 4 was buried by further excavating with an inch bit up to about 500 m, and cement 6 was filled in the annular gap portion between the conductor casing 4 and the conductor casing 1 and the pit wall 5 to fix them. Then, further digging up to 1100 m with a 17 1/2 inch bit, pulling up the digging pipe, burying and fixing the surface casing 7 in the well, and pit wall 8 and surface casing 7 and conductor casing 4 and surface casing. Cement 9 was filled in each of the annular gaps with 7 and fixed. The two-plug type cementing method was used as the cementing method for these casings.

When this casing cementing method was carried out, the cement slurry that had been pump-filled into the annular gap between the conductor casing 4 and the surface casing 7 as shown in FIG.
The cement head 11 was formed at about 300 m underground and solidified as it was, and the cement slurry did not return to the ground surface. Next, the top job cementing method of the present invention was carried out.

First, in the annular gap 12 between the conductor casing 4 and the surface casing 7, the inner diameter is 25 mm.
The small-diameter pipe 13 was inserted, and air was forced into the pipe 13 to scatter the muddy water retained in the cement head 11 of the annular gap 12. Then, geothermal steam (150 ° C.) was continuously fed into the well for 3 days through the geothermal fluid supply pipe 14 previously inserted into the well. The sent-in steam was recovered from the fluid recovery pipe 16 provided below the master valve 15. After that, fresh water instead of steam is fed from the geothermal fluid supply pipe 14 to cool the conductor casing 4 and the surface casing 7, and then the cement slurry is gradually fed from the small diameter pipe 13 to the annular gap portion 12, and the surface portion Cemented up to.

After that, the cement head around 300 m
When the degree of adhesion of the 11 cements and the presence or absence of water were measured by a logging device, it was confirmed that there was no water and the joint portion was adhered. In addition, after the cementing is completed, an underground crack (geothermal reservoir) is excavated further to 2500 m.
However, no crushing of the casing was found at around 300 m. In addition,
Regarding the equipment used, reference numeral 17 in the figure denotes a violent ejection preventing device for preventing the geothermal fluid from exploding.

Although not particularly implemented in this embodiment, before the air is press-fitted from the small diameter pipe 13,
You may inject fresh water to remove dirt such as mud in the gap 12, or you may scatter mud in the well by air lift etc. before sending geothermal steam, and replace it with steam. It is also possible to send hot water. As can be understood from the above description, it has been found that the method of the present invention can be applied to the cementing of all casings such as conductor casings and production casings.

[0019]

As described above, according to the top-job cementing method of the present invention, voids are less likely to occur in the cement head of the annular gap portion, and there is no residual water, so geothermal fluid production It is possible to provide an effective technique capable of preventing the casing from being crushed at times.

[Brief description of drawings]

FIG. 1 is an underground view showing a top job cementing method of the present invention.

[Fig. 2] An inside view of a general geothermal well.

FIG. 3 is a schematic diagram for explaining a conventional top job cementing method.

[Explanation of symbols]

 1, 4 Conductor casing 2, 5, 8 Well wall 3, 6, 9 Cement 7 Surface casing 10 Underground crack 11 Cement head 12 Annular gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Ikeuchi 72 Sasamori, Ukai, Takizawa-mura, Iwate-gun, Iwate Prefecture Hiji Heavy Industries, Ltd. Morioka Plant

Claims (1)

[Claims] 1. A cement slurry is pressure-filled into an annular gap between the casing and a well wall or another casing through a well casing, whereby the cement slurry is grounded when cementing the annular gap. In the top job cementing method of the well casing when the cement head is formed in the annular gap without solidifying in the middle of the process, the well casing is provided in the vicinity of the cement head. The geothermal fluid supply pipe is descended through the pipe, and steam or hot water is supplied into the casing through the pipe to heat the inside of the well to remove water in the annular gap portion, and then the annular gap. Top job cementing method for a well casing, characterized in that cement slurry is fed into the section.