CN113586004A - Method for plugging waste well of gas storage - Google Patents
Method for plugging waste well of gas storage Download PDFInfo
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- CN113586004A CN113586004A CN202010362088.7A CN202010362088A CN113586004A CN 113586004 A CN113586004 A CN 113586004A CN 202010362088 A CN202010362088 A CN 202010362088A CN 113586004 A CN113586004 A CN 113586004A
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- 239000002699 waste material Substances 0.000 title claims abstract description 147
- 238000003860 storage Methods 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000004568 cement Substances 0.000 claims abstract description 336
- 239000002002 slurry Substances 0.000 claims abstract description 92
- 238000007789 sealing Methods 0.000 claims abstract description 24
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 claims abstract description 23
- 229910052601 baryte Inorganic materials 0.000 claims abstract description 23
- 239000010428 baryte Substances 0.000 claims abstract description 23
- 239000007788 liquid Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 238000007790 scraping Methods 0.000 claims description 4
- 230000000694 effects Effects 0.000 abstract description 22
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000007789 gas Substances 0.000 description 53
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 16
- 238000010276 construction Methods 0.000 description 8
- 239000003345 natural gas Substances 0.000 description 8
- 238000002347 injection Methods 0.000 description 7
- 239000007924 injection Substances 0.000 description 7
- 239000011435 rock Substances 0.000 description 7
- 230000000903 blocking effect Effects 0.000 description 6
- 239000002245 particle Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000005056 compaction Methods 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 230000015271 coagulation Effects 0.000 description 2
- 238000005345 coagulation Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000002844 continuous effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000011882 ultra-fine particle Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
- E21B33/138—Plastering the borehole wall; Injecting into the formation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
- E21F17/16—Modification of mine passages or chambers for storage purposes, especially for liquids or gases
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- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The disclosure provides a method for plugging a waste well of a gas storage, and belongs to the technical field of production of gas storage. Injecting superfine cement slurry into a position, corresponding to a reservoir, in a to-be-blocked waste well, and forming a reservoir cement plug in the to-be-blocked waste well so as to block the reservoir; injecting conventional cement slurry into a position, corresponding to a cover layer, in a waste well to be blocked, forming a cover layer cement plug in the waste well to be blocked so as to block the cover layer, wherein the cover layer is an original layer which is positioned above a reservoir and used for sealing the reservoir; injecting conventional cement paste above a cover cement plug in a waste well to be plugged, and forming a continuous cement plug above the cover to plug the cover cement plug; and injecting the barite slurry above the continuous cement plug in the waste well to be plugged, and forming the heavy cement plug above the continuous cement plug so as to compact and seal the continuous cement plug. The plugging method for the waste well of the gas storage can obviously improve the plugging effect.
Description
Technical Field
The disclosure belongs to the technical field of gas storage production, and particularly relates to a method for plugging a waste well of a gas storage.
Background
The gas storage is an artificial gas field or a gas reservoir formed by reinjecting commodity natural gas conveyed by a long-distance pipeline into an underground space. And then establishing a gas storage well in the gas storage for gas production. The production of gas storage well is characterized by that in spring, summer and autumn high-pressure gas injection is implemented, and in winter, in order to ensure normal gas supply, large-discharge gas production is implemented. In the gas injection process, the waste well to be plugged in the gas storage also bears the same high pressure, the formation pressure is higher in the later stage of gas injection, and in order to prevent the natural gas from flowing away along the original oil extraction gas production channel, the waste well to be plugged needs to be plugged.
In the related technology, the plugging of the waste well to be plugged of the gas storage is generally performed by adopting a cement injection plug plugging technology, specifically, a certain amount of cement slurry is injected into a target layer of the gas storage and a corresponding shaft to form a cement plug, so as to achieve the purpose of permanently plugging the waste well to be plugged.
However, the operation of the gas storage has the characteristic of periodic strong mining and strong injection, and even after the gas storage is plugged, high-low pressure alternating load is still borne, so that the method directly plugs the waste well to be plugged, a certain micro gap is formed between a cement plug and a sleeve, the sealing of the waste well to be plugged is easily lost, once the sealing of the waste well to be plugged is lost, natural gas can be moved up and down along the cement plug or moved to a non-gas storage layer and a wellhead, and huge potential safety hazards are caused, and the safety production of one well is directly influenced.
Disclosure of Invention
The embodiment of the disclosure provides a method for plugging a waste well of a gas storage, which can effectively plug the waste well in the gas storage. The technical scheme is as follows:
the embodiment of the disclosure provides a method for plugging a waste well of a gas storage, which comprises the following steps:
injecting superfine cement slurry into a position, corresponding to a reservoir, in a to-be-blocked waste well, wherein a reservoir cement plug is formed in the to-be-blocked waste well so as to block the reservoir;
injecting conventional cement slurry into the position, corresponding to a cover layer, of the waste well to be blocked, wherein a cover layer cement plug is formed in the waste well to be blocked so as to block the cover layer, and the cover layer is an original layer which is positioned above the reservoir layer and used for sealing the reservoir layer;
injecting the conventional cement slurry above the cover cement plug in the abandoned well to be plugged, and forming a continuous cement plug above the cover cement plug to plug the cover cement plug;
injecting a barite slurry over the continuous cement plug in the abandoned well to be plugged and forming a heavy cement plug over the continuous cement plug to compact and seal the continuous cement plug.
In one implementation manner of the present disclosure, before injecting the ultrafine cement slurry into the to-be-plugged waste well at a position corresponding to the reservoir, and forming a reservoir cement plug in the to-be-plugged waste well to plug the reservoir, the plugging method further includes:
and cleaning the shaft of the waste well to be plugged.
In yet another implementation of the present disclosure, the cleaning the wellbore of the abandoned well to be plugged comprises:
scraping the shaft of the waste well to be plugged;
and performing clean water circulation well washing on the shaft of the waste well to be plugged for at least 2 weeks.
In yet another implementation of the present disclosure, the injecting the ultra-fine cement slurry into a to-be-plugged abandoned well at a position corresponding to a reservoir, the to-be-plugged abandoned well having a reservoir cement plug formed therein to plug the reservoir, includes:
lowering a cement pipe column into the waste well to be plugged, and enabling the cement pipe column to be located above the reservoir stratum;
injecting the superfine cement slurry into the reservoir through the cement pipe column so as to form a reservoir cement plug at a position corresponding to the reservoir in the waste well to be plugged and above the reservoir;
and closing the well and waiting for setting, so that the reservoir cement plug is solidified to form the reservoir cement plug.
In yet another implementation of the present disclosure, the injecting the ultra-fine cement slurry into the reservoir through the cement string to form the reservoir cement plug at and above the location corresponding to the reservoir in the abandoned well to be plugged comprises:
and injecting the superfine cement slurry into the cement pipe column by adopting the squeezing pressure not more than 20MPa until the top boundary of the superfine cement slurry is more than 50m of the reservoir, wherein the top boundary of the superfine cement slurry is the top surface of a liquid column formed by the superfine cement slurry in the cement pipe column.
In yet another implementation of the present disclosure, the shut-in setting to cure the reservoir cement plug to form the reservoir cement plug comprises:
closing the well and waiting for setting to solidify the reservoir cement plug to form a primary reservoir cement plug;
and injecting clear water at a pressure of not more than 20MPa to carry out positive pressure test operation on the preliminary reservoir cement plug, and if the pressure drop of the reservoir cement plug is less than 0.5MPa within 30min of the pressure test operation, taking the preliminary reservoir cement plug as the reservoir cement plug.
In yet another implementation of the present disclosure, the injecting the conventional cement slurry over the cap rock cement plug in the abandoned well to be plugged and forming a continuous cement plug over the cap rock to plug the cap rock cement plug comprises:
if the cover layer is in a sealing state, injecting the conventional cement paste into the waste well to be plugged at a position corresponding to the cover layer above the reservoir so as to form the cover layer cement plug with the length not less than 300 m;
and if the cover layer is in a non-sealing state, repairing the cover layer, and injecting the conventional cement paste into the position corresponding to the repaired cover layer to form the cover layer cement plug with the length not less than 300 m.
In yet another implementation of the present disclosure, the injecting the conventional cement slurry over the cap rock cement plug in the abandoned well to be plugged and forming a continuous cement plug over the cap rock to plug the cap rock cement plug comprises:
and injecting the conventional cement paste into the shaft of the waste well to be plugged through a high-pressure pump truck to form a continuous cement plug with the length of not less than 300 m.
In yet another implementation of the present disclosure, injecting a barite slurry over the continuous cement plug in the abandoned well to be plugged and forming a heavy cement plug over the continuous cement plug to compact and seal the continuous cement plug comprises:
and injecting the barite slurry into the shaft of the waste well to be plugged through a high-pressure pump truck to form the heavy cement plug with the length not less than 500 m.
In yet another implementation of the present disclosure, after the step of injecting a barite slurry into the abandoned well to be plugged above the continuous cement plug and forming a heavy cement plug above the continuous cement plug to compact and seal the continuous cement plug, the method further includes:
and injecting an annular protection liquid above the continuous cement plug in the waste well to be plugged so as to protect a casing between the upper part of the continuous cement plug and the wellhead of the waste well to be plugged.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
when the plugging method provided by the embodiment is used for plugging a waste well to be plugged, firstly, the superfine cement slurry is injected into a reservoir corresponding to the waste well to be plugged, and a reservoir cement plug is formed above the reservoir to plug the reservoir, so that the superfine cement slurry can enter the reservoir along pores in the reservoir, and the pores in the reservoir are plugged through the coagulation of the superfine cement slurry, thereby plugging the reservoir and preventing natural gas from losing from the reservoir. Then, conventional cement slurry is injected into the cover layer corresponding to the abandoned well and a cover layer cement plug is formed on the cover layer to seal the cover layer. Therefore, the cover layer can be plugged by forming the cover layer cement plug in the cover layer through the conventional cement paste, the gas reservoir tightness of the waste well to be plugged is further ensured, and the natural gas injected into the gas storage is prevented from possibly moving upwards along the cement ring outside the sleeve of the waste well to be plugged and entering the non-storage layer above the cover layer or reaching the ground.
And then, after the construction of reservoir and cover layer plugging is completed, injecting conventional cement paste above the cover layer cement plug to form a continuous cement plug so as to plug a shaft of a waste well to be plugged. Finally, a barite slurry is injected over the continuous cement plug to form a heavy cement plug from the barite slurry. In order to ensure the plugging effect, barite slurry is injected into the upper part of the cement plug, and the continuous cement plug can be sealed by means of the settlement and compaction effects of barite so as to thoroughly plug the shaft.
According to the method for plugging the waste well of the gas storage, the reservoir cement plug, the cover cement plug, the continuous cement plug and the heavy cement plug are formed respectively, so that the waste well to be plugged can be effectively plugged, a shaft in the waste well to be plugged can be fully sealed, and the plugging effect is guaranteed.
According to the method for plugging the waste well of the gas storage, the purpose of permanently plugging the waste well to be plugged of the gas storage is achieved by respectively and comprehensively plugging the reservoir, the cover layer and the shaft. The method for plugging the waste well of the gas storage is simple in construction steps and good in effect, and guarantees construction quality and safe operation of the gas storage in order to guarantee the permanent plugging effect of the waste well to be plugged of the gas storage.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a gas storage waste well according to an embodiment;
FIG. 2 is a flow chart of a method for plugging a waste well of a gas storage according to an embodiment of the present invention;
fig. 3 is a flow chart of another method for plugging a waste well of a gas storage according to an embodiment of the present invention.
The symbols in the drawings represent the following meanings:
1. artificial well bottom; 2. a reservoir; 3. a cap layer; 4. a sleeve; 41. a technical sleeve; 42. a surface casing; 5. the cement is back to high; 6. a continuous cement plug; 7. a heavy cement plug; 8. and (4) a protective solution.
Detailed Description
To make the objects, technical solutions and advantages of the present disclosure more apparent, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
In order to better describe the plugging method, the stratum structure of the waste well to be plugged is explained first with reference to fig. 1.
The waste well to be plugged comprises an artificial well bottom 1, a reservoir stratum 2, a cover stratum 3 and a sleeve 4, wherein the artificial well bottom 1 is positioned at the bottommost part of the waste well to be plugged, the reservoir stratum 2 is positioned above the artificial well bottom 1, the cover stratum 3 is positioned above the reservoir stratum 2, and the cover stratum 3 is used for plugging the reservoir stratum 2.
The cap rock 3 typically effects plugging of the reservoir 2 by cementing a plug. The sleeve 4 is arranged on the periphery of the well wall of the waste well to be plugged, and the sleeve 4 is used for supporting the well wall of the waste well to be plugged. The casing 4 is typically set around the wall of the abandoned well to be plugged by cement. The outer peripheral wall of the casing 4 forms a cement return 5 when setting takes place.
The inner wall of the casing 4 at a location adjacent the reservoir 2 is provided with perforations for communication with the reservoir 2. A technical casing 41 and a surface casing 42 are sequentially sleeved on the casing 4 close to the wellhead, and the surface casing 42 is sleeved on the outer side of the technical casing 41.
Fig. 2 is a flow chart of the plugging method, and as shown in fig. 2, the plugging method includes:
s201: injecting superfine cement slurry into the position, corresponding to the reservoir, of the to-be-blocked waste well, and forming a reservoir cement plug in the to-be-blocked waste well so as to block the reservoir.
In the implementation mode, the reservoir of the waste well to be plugged can be effectively plugged through the superfine cement slurry injected into the reservoir at high pressure.
The ultrafine cement slurry is a cement slurry prepared by using ultrafine cement, and in general, the ultrafine cement is high-performance grouting material particles composed of inorganic ultrafine particles such as ultrafine cement, and the particle size of the particles is smaller than that of conventional cement.
S202: and injecting conventional cement slurry into the position, corresponding to the cover layer, of the waste well to be blocked, and forming a cover layer cement plug in the waste well to be blocked so as to block the cover layer, wherein the cover layer is an original layer which is positioned above the reservoir and used for sealing the reservoir.
In the implementation mode, the cover layer is used as an original sealing layer of the reservoir, and the sealing cover layer can ensure the tightness of the gas reservoir in the waste well to be sealed. And the water-filled slurry is injected into the cover layer at high pressure, so that the cover layer can be blocked by a cement plug formed by the slurry.
It should be noted that the conventional cement slurry is distinguished from the above ultra-fine cement slurry, and the conventional cement slurry refers to a cement slurry prepared by conventional cement, which is ordinary cement used for well cementation during drilling.
S203: conventional cement slurry is injected over the cap cement plug in the abandoned well to be plugged and a continuous cement plug is formed over the cap to plug the cap cement plug.
In the implementation mode, the conventional cement slurry is injected into the shaft of the waste well to be plugged to form the continuous cement plug, so that the shaft of the waste well to be plugged can be plugged, and the plugging effect of the waste well to be plugged is further improved.
S204: and injecting the barite slurry above the continuous cement plug in the waste well to be plugged, and forming the heavy cement plug above the continuous cement plug so as to compact and seal the continuous cement plug.
When the plugging method provided by the embodiment is used for plugging a waste well to be plugged, firstly, the superfine cement slurry is injected into a reservoir corresponding to the waste well to be plugged, and a reservoir cement plug is formed above the reservoir to plug the reservoir, so that the superfine cement slurry can enter the reservoir along pores in the reservoir, and the pores in the reservoir are plugged through the coagulation of the superfine cement slurry, thereby plugging the reservoir and preventing natural gas from losing from the reservoir. Then, conventional cement slurry is injected into the cover layer corresponding to the abandoned well and a cover layer cement plug is formed on the cover layer to seal the cover layer. Therefore, the cover layer can be plugged by forming the cover layer cement plug in the cover layer through the conventional cement paste, the gas reservoir tightness of the waste well to be plugged is further ensured, and natural gas injected into the gas storage is prevented from possibly moving upwards along a cement ring outside a sleeve of the waste well to be plugged and entering a non-storage layer above the cover layer or reaching the ground.
And then, after the construction of reservoir and cover layer plugging is completed, injecting conventional cement paste above the cover layer cement plug to form a continuous cement plug so as to plug a shaft of a waste well to be plugged. Finally, a barite slurry is injected over the continuous cement plug to form a heavy cement plug from the barite slurry. In order to ensure the plugging effect, barite slurry is injected into the upper part of the cement plug, and the continuous cement plug can be sealed by means of the settlement and compaction effects of barite so as to thoroughly plug the shaft.
According to the method for plugging the waste well of the gas storage, the reservoir cement plug, the cover cement plug, the continuous cement plug and the heavy cement plug are formed respectively, so that the waste well to be plugged can be effectively plugged, a shaft in the waste well to be plugged can be fully sealed, and the plugging effect is guaranteed.
According to the method for plugging the waste well of the gas storage, the purpose of permanently plugging the waste well to be plugged of the gas storage is achieved by respectively and comprehensively plugging the reservoir, the cover layer and the shaft. The method for plugging the waste well of the gas storage is simple in construction steps and good in effect, and guarantees construction quality and safe operation of the gas storage in order to guarantee the permanent plugging effect of the waste well to be plugged of the gas storage.
Fig. 3 is another gas storage waste well plugging method provided by an embodiment of the present invention, and referring to fig. 3, the gas storage waste well plugging method includes:
step 301: and cleaning a shaft of the waste well to be plugged.
In the implementation mode, the shaft of the waste well to be plugged is cleaned, dirt attached to the shaft of the waste well to be plugged can be removed, so that various cement plugs formed in the shaft subsequently can be in sealing fit with the inner wall of the shaft, the plugging effect is further improved, and sealing failure is avoided.
Alternatively, step 301 may be implemented by:
firstly, a shaft of a waste well to be plugged is scraped.
In the implementation mode, the impurities and dirt attached to the inner wall of the shaft of the waste well to be plugged can be removed, so that the sealing effect between the inner wall of the shaft and the cement slurry injected subsequently is better.
Illustratively, the scraper repeatedly scrapes the well section range from 50m above to 50m below the well section to be plugged in the abandoned well for at least 5 times by lifting and lowering the scraper back and forth in the well shaft of the abandoned well to be plugged.
In the implementation mode, the scraper is used for repeatedly scraping the inside of the shaft of the waste well to be plugged, so that the attached impurities on the inner wall of the shaft can be quickly removed.
In addition, in the embodiment, in order to ensure that the shaft of the waste well to be blocked is smooth up and down, the shaft of the waste well to be blocked can be salvaged together during scraping, if the shaft of the waste well to be blocked has fallen objects, the fallen objects can be salvaged, and the purpose of fishing is on the premise of not influencing the blocking.
And then, performing clean water circulation well washing on the shaft of the waste well to be plugged for at least 2 weeks.
In the above implementation, the impurity dirt existing in the well bore can be discharged out of the well bore by the clean water circulation well washing. Meanwhile, the inner wall of the shaft of the waste well to be blocked can be further cleaned through circulating well washing, and the smoothness of the shaft of the waste well to be blocked is finally ensured.
Step 302: injecting superfine cement slurry into the position, corresponding to the reservoir, of the to-be-blocked waste well, and forming a reservoir cement plug in the to-be-blocked waste well so as to block the reservoir.
In the implementation mode, the reservoir of the waste well to be blocked is blocked by injecting the superfine cement slurry into the reservoir corresponding to the waste well to be blocked and solidifying the superfine cement slurry in the reservoir, and meanwhile, the reservoir cement plug is formed above the reservoir, so that the reservoir can be further blocked.
Alternatively, step 302 may be implemented by:
firstly, a cement pipe column is lowered into a waste well to be plugged, and the cement pipe column is positioned above a reservoir stratum.
In the implementation mode, the cement pipe column penetrates through the cover layer and is placed above the reservoir layer, so that the injected superfine cement paste can cross the cover layer and enter the reservoir layer along the cement pipe column, and a reservoir layer cement plug is formed above the reservoir layer.
And then, injecting the superfine cement slurry into the reservoir through the cement pipe column so as to form a reservoir cement plug at the position corresponding to the reservoir in the waste well to be plugged and above the waste well to be plugged.
In the implementation mode, the cement pipe column penetrates through the cover layer and is placed above the reservoir, so that the superfine cement slurry can be effectively guaranteed to enter and exit the reservoir quickly, and the matching of the superfine cement slurry can be selected according to the porosity of the corresponding reservoir in the waste well to be blocked.
Generally, superfine cement with matched particles is selected to be prepared into superfine cement slurry according to the porosity of a reservoir corresponding to a waste well to be plugged.
Exemplarily, the above steps are implemented by:
(1) and injecting the superfine cement slurry into the cement pipe column by adopting the squeezing pressure of not more than 20MPa until the top boundary of the superfine cement slurry is more than 50m of the reservoir, wherein the top boundary of the superfine cement slurry is the top surface of a liquid column formed by the superfine cement slurry in the cement pipe column.
In the implementation mode, the superfine cement paste can be smoothly injected into the reservoir to seal the reservoir by reasonably controlling the pressure of extruding the superfine cement paste, and the top boundary of a liquid column of the superfine cement paste formed after the superfine cement paste is more than 50m of the reservoir, so that the sealing effect of the reservoir can be ensured.
Illustratively, the ultra-fine cement slurry may be injected into the cement string using a positive circulation injection method, and the average radius of the ultra-fine cement slurry into the reservoir is 0.5-4 m.
In the implementation mode, the superfine cement slurry is injected from the cement pipe column through a forward circulation injection method, and liquid in the well in the waste well to be blocked is discharged from the well mouth, so that the superfine cement slurry can be quickly injected into the reservoir to block the reservoir.
(2) And lifting the cement pipe column to the top boundary of the reservoir cement plug by a pump truck for more than 100 m.
In the implementation mode, through the operation, when the superfine cement slurry is solidified at the reservoir and above the reservoir to form the reservoir cement plug, the cement pipe columns are also solidified and solidified together, and further the formed reservoir cement plug is prevented from being infirm or the blocking effect is poor.
(3) And closing the well and waiting for setting so that the reservoir cement plug is solidified to form the reservoir cement plug.
It should be noted that shut-in and setting-out refers to closing the wellhead device and allowing the reservoir cement plug to set by standing.
In the implementation mode, the superfine cement slurry injected into the reservoir of the abandoned well to be blocked can be solidified at a high speed by closing the well and waiting for solidification, so that a reservoir cement plug is formed above the reservoir, and the reservoir is blocked.
(4) And injecting clear water under the pressure of not more than 20MPa to carry out positive pressure test operation on the preliminary reservoir cement plug, and if the pressure drop of the reservoir cement plug is less than 0.5MPa within 30min of the pressure test operation, taking the preliminary reservoir cement plug as the reservoir cement plug.
In the implementation mode, whether the reservoir cement plug formed in the abandoned well to be blocked in the steps can effectively block the reservoir can be detected by performing pressure test operation on the reservoir cement plug, and the blocking effect of the reservoir cement plug on the reservoir is determined.
Illustratively, during pressure test operation, the reservoir is normally tested under the pressure of 20MPa by adopting clean water, the pressure test operation requires 30min, and the reservoir plugging by the reservoir cement plug is qualified when the pressure drop of the reservoir cement plug is less than 0.5 MPa. On the contrary, within 30min of pressure test operation, if the pressure drop of the reservoir cement plug is not less than 0.5MPa, the reservoir is not qualified for blocking, and the reservoir needs to be blocked continuously.
If the reservoir plugging is unqualified, drilling and plugging the original reservoir cement plug, and then continuously injecting the superfine cement plug until the pressure test is qualified.
Step 303: conventional cement slurry is injected over the cap cement plug in the abandoned well to be plugged and a continuous cement plug is formed over the cap to plug the cap cement plug.
In the implementation mode, the cover layer is used as an original sealing layer of the reservoir and is generally positioned above the reservoir, the purpose of blocking the cover layer is to ensure the gas reservoir tightness in the waste well to be blocked, and if the cover layer is not blocked, natural gas injected into the reservoir in the waste well to be blocked is likely to move upwards along two interfaces of one interface area of a cement ring outside a sleeve of the waste well to be blocked and to flow into a non-reservoir layer above the cover layer or a well mouth of the waste well to be blocked to the ground.
Alternatively, step 303 may be implemented by:
if the cover layer is in a sealing state, injecting conventional cement paste into the waste well to be plugged at a position corresponding to the cover layer above the reservoir to form a cover layer cement plug with the length not less than 300 m;
in the implementation mode, if the cover layer is in a perfect sealing state, the cover layer can effectively plug the reservoir, so that the cover layer can be effectively plugged by directly forming the cover layer cement plug above the cover layer.
And if the cover layer is in a non-sealing state, repairing the cover layer, and injecting conventional cement paste into a position corresponding to the repaired cover layer to form a cover layer cement plug with the length not less than 300 m.
In the implementation manner, if the cover layer is in an imperfect sealing state, it indicates that the cover layer cannot effectively plug the reservoir, and at this time, the cover layer needs to be effectively repaired to ensure that the cover layer can effectively plug the reservoir, so that cement slurry can be continuously injected to form a cover layer cement plug to plug the cover layer.
Illustratively, when the cover layer corresponding to the waste well to be plugged is in an imperfect sealing state, and the annular cement return height above the reservoir top boundary corresponding to the waste well to be plugged is less than 200m, or the continuous high-quality cement cementing section above the reservoir top boundary is less than 25m, repairing the cover layer, casing forging and milling the cover layer section above the reservoir top boundary of the waste well, wherein the casing forging and milling length is not less than 30 m. Conventional cement slurry is then injected into the forge milled well section to form a 30-50m cap cement plug.
In the implementation mode, if the cover layer is in a non-sealing state and the section with continuous high-quality cement cementation above the top boundary of the reservoir is less than 25m, at this time, the cover layer of the waste well to be plugged and the casing are in a non-sealing state, and the casing and the cover layer need to be resealed according to the relevant operation requirements, so that resealing between the casing and the cover layer can be achieved through casing forging and milling.
Step 304: conventional cement slurry is injected over the cap cement plug in the abandoned well to be plugged and a continuous cement plug is formed over the cap to plug the cap cement plug.
In the implementation mode, the shaft can be plugged by forming the continuous cement plug by using the conventional cement paste, and the plugging effect of the plugging method on the waste well to be plugged is further improved.
Alternatively, step 304 may be implemented by:
and injecting conventional cement slurry into a shaft of the waste well to be plugged through a high-pressure pump truck to form a continuous cement plug with the length of not less than 300 m.
In the implementation mode, the conventional cement paste is the cement paste prepared by conventional cement, and the length of the continuous cement plug is not less than 300m, so that the blocking effect of the continuous cement plug on the cover cement plug can be ensured.
Step 305: and injecting the barite slurry above the continuous cement plug in the waste well to be plugged, and forming the heavy cement plug above the continuous cement plug so as to compact and seal the continuous cement plug.
In above-mentioned implementation, through pouring into the barite mud in continuous cement stopper top, form the heavy cement stopper through the barite mud, rely on the continuous effect of subsiding, the compaction of heavy cement stopper, can play sealed effect to the continuous cement stopper, and then further improve the shutoff effect of this shutoff method.
Alternatively, step 305 may be implemented by:
and injecting barite slurry into a shaft of the waste well to be plugged through a high-pressure pump truck to form a heavy cement plug with the length not less than 500 m.
In the implementation mode, the barite slurry is injected into the well casing to be plugged to form the heavy cement plug, so that the continuous cement plug can be further compacted and sealed, and the plugging effect of the continuous cement plug is improved.
Step 306: and injecting the annular protection liquid above the continuous cement plug in the waste well to be plugged so as to protect a sleeve between the upper part of the continuous cement plug and the wellhead of the waste well to be plugged.
In the implementation mode, the annulus protection liquid is injected into the uppermost part inside the shaft of the waste well to be plugged, and the casing of the waste well to be plugged is completely soaked by the annulus protection liquid, so that the casing can be effectively protected by the annulus protection liquid, and the casing in the waste well to be plugged is prevented from being corroded.
Step 307: and installing wellhead equipment on the wellhead of the abandoned well to be plugged to complete the well.
In the above implementation mode, the simple wellhead equipment is installed on the wellhead of the waste well to be blocked, so that the waste well to be blocked can be further blocked, and unnecessary troubles caused by overlarge pressure in the well are prevented.
Illustratively, the simple wellhead equipment may include wellhead pressure gauges, wellhead valves, and the like. The installation is carried out according to actual needs.
Referring to fig. 1 again, in this embodiment, after the gas storage waste well plugging method is used for plugging a waste well to be plugged, the concrete plugging state may be as shown in fig. 1, and a reservoir cement plug is plugged above a reservoir 2. And a cover cement plug is plugged above the cover layer 3. And the continuous cement plug 6 is blocked above the cover cement plug. The upper part of the continuous cement plug 6 plugs the heavy cement plug 7, and a shaft on the upper part of the heavy cement plug 7 is filled with protective liquid 8. Therefore, the method can be used for permanently and comprehensively plugging the reservoir, the cover layer and the shaft, so that the aim of permanently plugging the waste well to be plugged in the gas storage can be fulfilled. The method for plugging the waste well of the gas storage is simple in construction steps and good in effect, and guarantees construction quality and safe operation of the gas storage in order to guarantee the permanent plugging effect of the waste well to be plugged of the gas storage.
The above description is meant to be illustrative of the principles of the present disclosure and not to be taken in a limiting sense, and any modifications, equivalents, improvements and the like that are within the spirit and scope of the present disclosure are intended to be included therein.
Claims (10)
1. A method for plugging a gas storage waste well is characterized by comprising the following steps:
injecting superfine cement slurry into a position, corresponding to a reservoir, in a to-be-blocked waste well, wherein a reservoir cement plug is formed in the to-be-blocked waste well so as to block the reservoir;
injecting conventional cement slurry into the position, corresponding to a cover layer, of the waste well to be blocked, wherein a cover layer cement plug is formed in the waste well to be blocked so as to block the cover layer, and the cover layer is an original layer which is positioned above the reservoir layer and used for sealing the reservoir layer;
injecting the conventional cement slurry above the cover cement plug in the abandoned well to be plugged, and forming a continuous cement plug above the cover cement plug to plug the cover cement plug;
injecting a barite slurry over the continuous cement plug in the abandoned well to be plugged and forming a heavy cement plug over the continuous cement plug to compact and seal the continuous cement plug.
2. The plugging method according to claim 1, wherein before injecting the ultra-fine cement slurry into a waste well to be plugged at a position corresponding to a reservoir, the waste well to be plugged forming a reservoir cement plug to plug the reservoir, the plugging method further comprises:
and cleaning the shaft of the waste well to be plugged.
3. The method of plugging according to claim 2 wherein said cleaning of the wellbore of the depleted well to be plugged comprises:
scraping the shaft of the waste well to be plugged;
and performing clean water circulation well washing on the shaft of the waste well to be plugged for at least 2 weeks.
4. The plugging method according to claim 1, wherein the injecting the ultra-fine cement slurry into a waste well to be plugged at a position corresponding to a reservoir, and a reservoir cement plug is formed in the waste well to be plugged so as to plug the reservoir, comprises:
lowering a cement pipe column into the waste well to be plugged, and enabling the cement pipe column to be located above the reservoir stratum;
injecting the superfine cement slurry into the reservoir through the cement pipe column so as to form a reservoir cement plug at a position corresponding to the reservoir in the waste well to be plugged and above the reservoir;
and closing the well and waiting for setting, so that the reservoir cement plug is solidified to form the reservoir cement plug.
5. The method of plugging according to claim 4, wherein said injecting said ultra-fine cement slurry into said reservoir through said cement string to form said reservoir cement plug at and above a location corresponding to said reservoir in said depleted well to be plugged comprises:
and injecting the superfine cement slurry into the cement pipe column by adopting the squeezing pressure not more than 20MPa until the top boundary of the superfine cement slurry is more than 50m of the reservoir, wherein the top boundary of the superfine cement slurry is the top surface of a liquid column formed by the superfine cement slurry in the cement pipe column.
6. The method of plugging according to claim 4, wherein said shut-in waiting for setting said reservoir cement plug to form said reservoir cement plug comprises:
closing the well and waiting for setting to solidify the reservoir cement plug to form a primary reservoir cement plug;
and injecting clear water at a pressure of not more than 20MPa to carry out positive pressure test operation on the preliminary reservoir cement plug, and if the pressure drop of the reservoir cement plug is less than 0.5MPa within 30min of the pressure test operation, taking the preliminary reservoir cement plug as the reservoir cement plug.
7. The method of any one of claims 1 to 6, wherein the injecting the conventional cement slurry over the cap cement plug in the abandoned well to be plugged and forming a continuous cement plug over the cap cement plug to plug the cap cement plug comprises:
if the cover layer is in a sealing state, injecting the conventional cement paste into the waste well to be plugged at a position corresponding to the cover layer above the reservoir so as to form the cover layer cement plug with the length not less than 300 m;
and if the cover layer is in a non-sealing state, repairing the cover layer, and injecting the conventional cement paste into the position corresponding to the repaired cover layer to form the cover layer cement plug with the length not less than 300 m.
8. The method of any one of claims 1 to 6, wherein the injecting the conventional cement slurry over the cap cement plug in the abandoned well to be plugged and forming a continuous cement plug over the cap cement plug to plug the cap cement plug comprises:
and injecting the conventional cement paste into the shaft of the waste well to be plugged through a high-pressure pump truck to form a continuous cement plug with the length of not less than 300 m.
9. The plugging method according to any one of claims 1 to 6, wherein injecting a barite slurry over the continuous cement plug in the abandoned well to be plugged and forming a heavy cement plug over the continuous cement plug to compact and seal the continuous cement plug comprises:
and injecting the barite slurry into the shaft of the waste well to be plugged through a high-pressure pump truck to form the heavy cement plug with the length not less than 500 m.
10. The plugging method according to any one of claims 1 to 6, wherein the step of injecting a barite slurry over the continuous cement plug in the abandoned well to be plugged and forming a heavy cement plug over the continuous cement plug to compact and seal the continuous cement plug further comprises:
and injecting an annular protection liquid above the continuous cement plug in the waste well to be plugged so as to protect a casing between the upper part of the continuous cement plug and the wellhead of the waste well to be plugged.
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