JP2951826B2 - Top job cementing method for well casing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top job cementing method for a well casing, and more particularly to a method of forming a void in a cement head in an annular gap and preventing water from remaining in the annular gap. Therefore, a top job cementing method for a well casing that can prevent the collapse of the casing when collecting geothermal fluid or the like is proposed.

[0002]

2. Description of the Related Art In a well such as a geothermal well or an oil well, a casing made of a steel pipe is buried in the well for the purpose of preventing inflow of low-temperature hot water and preventing collapse of a well wall. FIG.
Is a general geothermal well plan (casing program), and the conductor casing extends up to 90m from the surface.
21 is buried, and a surface casing 22 buried to a depth of about 600 m is positioned inside the buried surface casing 21. And, the more the inside of Surface casing 22, Thailand back casing in direct contact with the geothermal fluid is a mixed fluid of steam and heat water to be ejected from the underground crack
23 and liner 24 are buried to reach a depth of around 1500m. The gaps between the casings 21, 22, and 23 are filled with cement 25 and are fixed to each other. Also, reference numeral 26 in the figure is
It is an open hole where the casing is not set, and is a part where the geothermal fluid is collected from the underground crack.

Conventionally, as a method of burying and fixing the above casings, a two-plug cementing method, a two-stage cementing method, an inner string cementing method, a top job cementing method, and the like have been applied. The most commonly used two-plug cementing method among the above cementing methods will be described below. in this way,
First, in the drilled well, a centralizer etc.
Between the drilled Anakabe or outer casing for inserting the upper listen pacing so as to leave an annular gap. Then, the wellbore was cooled by injecting mud into the casing, then to pump pre flush (prior solution) within its casing. Then, muddy water and up the cement slurry at the time of pumping
So as not to mix with Les flash, first into the casing
A plug is inserted, the cement slurry is pressure-filled into the casing, and then a second plug is inserted to sandwich the cement slurry between the first and second plugs. Thereafter, the second plug is pressurized by feeding muddy water from the above-ground portion, so that the first plug arrives at the casing bottom portion, and at the same time, the casing and the casing or the casing are inserted through the cement inlet hole provided in the first plug. In this method, the cement slurry is pushed into the annular gap between the pit and the pit wall to return the cement slurry to the ground surface.

[0004] In the case of the cement cementing method using the two-plug cementing method, it is usual that the cement pressed and filled into the casing returns to the surface of the ground through the annular gap. When cement is lost in the formation due to its presence, there is a problem that the cement does not return completely to the surface but stops in the middle of the annular gap to form the cement head and solidifies as it is. .

On the other hand, the above-mentioned top job cementing method is a method developed to solve the above-mentioned problems of the two-plug type cementing method. As shown in FIG. 3, the top job cementing method firstly starts from the surface to the small diameter pipe 35 to the vicinity of the cement head 34 of the cement 33 solidified in the annular gap between the casing 31 and the pit wall or the casing 32. The tip of is inserted and lowered, clean water is fed into the small-diameter pipe to wash the annular gap, and then the cement slurry is pumped from the pipe, and when the cement slurry returns to the ground, the small-diameter pipe 35 is lifted. That is the method.

[0006]

In the prior art described above, generally, a casing buried in a wellbore has a coupling portion for connecting the casing and the casing protruding from the hole wall side, or the casing is not provided with the coupling portion. Since the centralizer for setting in the center of the well is protruding toward the hole wall side like the coupling part, there is a problem that only a small diameter pipe can be inserted into the annular gap. In addition, according to these conventional methods, when the cement head exists deep underground, voids may be formed in the vicinity of the cement head without being uniformly filled with the cement slurry, and water may be formed in the void. There has been a problem that the casing is fixed while being closed, causing various adverse effects.

[0007] In particular, when water is trapped in the above-mentioned gap, when a test or production of a geothermal fluid is started, the water expands due to the high-temperature geothermal fluid, and the casing is pushed inside the well by the pressure. As a result, the casing could be crushed.

When the casing is crushed, logging equipment such as a thermometer and a pressure gauge and drilling equipment for repair cannot be lowered into the well, or a low-temperature geothermal fluid flows into the well. anti of or Kitaichi the temperature drop of the wellbore, in the worst case, geothermal fluid is ejected directly to the ground portion around wells from the portion which crushed without passing through the casing
An important obstacle to well maintenance occurs .

As a means for preventing such various problems, conventionally, it has been considered to replace the top job cementing by filling the annular gap with gravel or sand whose grain size has been adjusted. However, in such an alternative method, the casing cannot be fixed tightly, and there are other problems such as an increase in the wellhead portion and a reduction in the life of the well due to vibration caused by the ejection of the geothermal fluid.

Therefore, an object of the present invention is to provide a top job cementing technique which makes it difficult for voids to be formed in the cement head in the annular gap and prevents water from remaining in the cement head. In order to propose a top-job cementing method for well casings without causing casing crushing.

[0011]

Means for Solving the Problems As a result of earnest research to achieve the above-mentioned object, it was found that it was effective to use steam or hot water for the above-mentioned problems.
We have now conceived a method of the present invention as described below. That is, the present invention is to perform cementing of the annular gap by pumping and filling cement slurry into the annular gap between the casing and the wellbore or another casing through the well casing, Accidents such as misidentification of temperature in the formation, misidentification of the amount of cement,
In the top job cementing method of the well casing when the cement slurry is solidified in the middle without returning to the surface to form a cement head in the annular gap, in the vicinity of the cement head, After the geothermal fluid supply pipe is lowered through the well casing and steam or hot water is supplied into the casing through the pipe, the well is heated to remove moisture in the annular gap. And feeding a cement slurry into the annular gap portion.

[0012]

In the top job cementing method according to the present invention, before the cement slurry is fed into the annular gap from the small diameter pipe, the cement slurry solidifies hot water or steam from the geothermal fluid supply pipe through the wellbore. This is a method of feeding the cement slurry from a small-diameter pipe after evaporating and removing the water in the annular gap by supplying it to the vicinity of the cement head. Therefore, according to such a method, a void portion is hardly generated in the annular gap portion, and water does not remain, so that even if the injection test or production of the geothermal fluid is started, the casing may be crushed. Not even.

[0013]

FIG. 1 is an underground view for explaining a top job cementing method according to the present invention. First, a well casing cementing method up to implementing the top job cementing method of the present invention will be described with reference to FIG.

After excavating to a depth of 34 inches by digging with a 24-inch bit to about 50 m underground, the conductor casing 1
And the annular gap between the pit wall 2 and the conductor casing 1 was filled with cement 3 and fixed. Then 24
Dig further to around 500m with an inch bit and surf
Buried E scan casing 4, and fixing the annular gap between the surface casing 4 and conductor casing 1 and Anakabe 5 filled with cement 6. Next, dig up to 1100m with 17 1/2 inch bit,
After raising the digging pipes, buried secure the Intermediate over preparative Ke <br/> pacing 7 Downhole, Anakabe 8 and Intermediate chromatography
Preparative casing 7 and surface casing 4 and inter
Each of the annular gaps with the intermediate casing 7 was filled with cement 9 and fixed. In addition, the cementing method of these casings used the two-plug type cementing method.

[0015] When embodying the casing cementing method, and surface casing 4 as shown in FIG. 1 interface
-The cement slurry pumped and filled into the annular gap between the intermediate casing 7 and the underground crack 10 was lost to the underground crack 10, so the cement head 11 was formed about 300m below the ground and solidified as it was, and the cement slurry returned to the ground surface. Next, the top job cementing method of the present invention was implemented.

First, the surface casing 4 and the interface
The annular gap 12 between the Midieto casing 7, by inserting a small diameter pipe 13 having an inner diameter of 25 mm, were scattered mud by press-fitting the air has remained the cement head 11 of the annular gap 12 into the pipe 13 . Next, geothermal steam (150 ° C.) was introduced into the wellbore from the geothermal fluid supply pipe 14 previously inserted into the wellbore.
Sent for consecutive days. The sent steam was recovered from a fluid recovery pipe 16 provided below the master valve 15. After that, fresh water is supplied from the geothermal fluid supply pipe 14 instead of steam to supply the surface casing 4 and the interface.
The intermediate casing 7 was cooled, and then the cement slurry was gradually fed from the small-diameter pipe 13 into the annular gap 12, and cemented to the surface.

After that, the cement head near 300 m
When the degree of adhesion of cement and the presence or absence of water in the cement of No. 11 were measured by a logging device, it was confirmed that there was no water and the seam portion was in close contact. In addition, after cementing is completed, the ground is further excavated to 2500m and the underground crack (geothermal reservoir)
Therefore, the blast test was started, but no crushing of the casing near 300 m was observed. In addition,
Regarding the equipment used, reference numeral 17 in the figure denotes a blast preventing device for preventing blast of geothermal fluid.

In this embodiment, although not particularly implemented, before air is injected from the small-diameter pipe 13,
Dirt such as mud in the gap 12 may be removed by injecting fresh water, or muddy water in the well may not be scattered by an air lift or the like before sending geothermal steam. Alternatively, hot water can be sent. As can be understood from the above description, it has been found that the method of the present invention can be applied to cementing of any casing such as a conductor casing and a production casing.

[0019]

As described above, according to the top job cementing method of the present invention, a void is hardly generated in the cement head in the annular gap and there is no residual moisture, so that the geothermal fluid production is prevented. It is possible to provide an effective technique capable of preventing the casing from being crushed at times.

[Brief description of the drawings]

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

FIG. 2 is a general geothermal well pit.

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

[Explanation of symbols]

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

Continuation of the front page (56) References JP-A-7-34770 (JP, A) JP-A-61-237792 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E21B 33 / 13

Claims (1)

(57) [Claims] 1. A cement slurry is pressure-fed and filled into an annular gap between the casing and a wellbore or another casing through a well casing, whereby cement slurry is applied to the surface of the ground when performing cementing of the annular gap. In the top job cementing method for the well casing when the cement head is solidified in the middle without returning to form a cement head in the annular gap, the well casing is provided near the cement head. By lowering a geothermal fluid supply pipe through the inside and supplying steam or hot water into the casing through the pipe, the inside of the well is heated to remove moisture in the annular gap, and then the annular gap is removed. Top job cementing method of wellbore casing, characterized in that the fed cement slurry section.