CN112253085A - Method for determining length of well completion string - Google Patents

Method for determining length of well completion string Download PDF

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Publication number
CN112253085A
CN112253085A CN202011062438.4A CN202011062438A CN112253085A CN 112253085 A CN112253085 A CN 112253085A CN 202011062438 A CN202011062438 A CN 202011062438A CN 112253085 A CN112253085 A CN 112253085A
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China
Prior art keywords
completion string
string
distance
annular space
insertion end
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CN202011062438.4A
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CN112253085B (en
Inventor
王汉
李玉飞
张华礼
陆林峰
张�林
唐庚
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Petrochina Co Ltd
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Petrochina Co Ltd
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/08—Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00—Survey of boreholes or wells
    • E21B47/04—Measuring depth or liquid level

Abstract

The disclosure provides a length determination method of a well completion pipe string, and belongs to the field of well completion processes of oil and gas wells. The length determination method comprises the following steps: running the completion string into the production casing to a first depth using a drill pipe; injecting a liquid into the annular space between the hanging string and the production casing to circulate the liquid through the annular space and the completion string; continuing to lower the completion string and monitoring the liquid pressure in the annular space in real time; stopping lowering the completion string when the liquid pressure in the annular space reflects that the insertion end of the completion string is contacted with the top of the back insertion barrel; acquiring a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is in contact with the top of the back-plugging barrel; based on the second distance, a length of the completion string is determined. The method does not need to insert the well completion string into the back-plugging barrel, reduces the possibility of damaging the sealing ring outside the well completion string, ensures the sealing effect between the well completion string and the back-plugging barrel, and improves the well completion quality.

Description

Method for determining length of well completion string
Technical Field
The disclosure relates to the field of well completion processes of oil and gas wells, in particular to a length determination method of a well completion pipe string.
Background
The well completion refers to a process of communicating a well bottom and an oil layer in a certain structure after an open hole well reaches a designed well depth. The well completion is the last important link of the well drilling work and the beginning of the oil production engineering, and is closely connected with the subsequent oil production, water injection and the development of the whole oil and gas field. Therefore, the quality of the well completion of the oil and gas well directly affects the production capacity and the economic life of the oil and gas well, and even relates to whether the whole oil field can be reasonably developed.
In the related art, when a completion operation is performed, a completion string with a certain length is generally required to be lowered into a well by using a drill pipe and inserted into a back insert sleeve in the well, and then a target length of the completion string required to be inserted into the back insert sleeve from a wellhead is determined according to the lowering depths of the drill pipe and the completion string. And then, matching the length of the completion string according to the determined target length so that the length of the completion string reaches the target length. Finally, the lengthened completion string is inserted into the back-plugging barrel to complete the completion operation. The end, inserted into the back insertion barrel, of the completion string is externally provided with a plurality of sealing rings, so that the completion string can be in sealing fit with the back insertion barrel, and oil and gas production operation can be conveniently carried out subsequently through the completion string and the back insertion barrel.
However, in the above-mentioned well completion operation, when the length of the completion string is determined, the completion string needs to be inserted into the back-plugging barrel, which may cause damage to the sealing ring outside the completion string, affect the sealing effect between the completion string and the back-plugging barrel after the completion string is inserted back into the back-plugging barrel, and further affect the completion quality and the production capacity of the oil and gas well.
Disclosure of Invention
The embodiment of the disclosure provides a length determination method of a well completion string, the well completion string does not need to be inserted into a back insert barrel, the possibility that a sealing ring outside the well completion string is damaged is reduced, the sealing effect between the well completion string and the back insert barrel is ensured, and the well completion quality is improved. The technical scheme is as follows:
the disclosed embodiment provides a length determination method of a completion string, wherein the completion string is used for being inserted back into an insertion barrel in a production casing, the insertion barrel is positioned at the top of a suspension string, the suspension string is positioned in the production casing in a well and a suspension packer is arranged between the suspension string and the production casing, and the length determination method is characterized by comprising the following steps:
running the completion string into the production casing with a drill pipe to a first depth, the first depth being a first distance from the insertion end of the completion string to a wellhead;
injecting a liquid into an annular space between the hanger string and the production casing, circulating the liquid within the annular space and the completion string;
continuing to lower the completion string and monitoring the fluid pressure in the annulus in real time;
stopping lowering the completion string when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
obtaining a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is in contact with the top of the back-plugging barrel;
determining a length of the completion string based on the second distance.
Optionally, stopping lowering the completion string when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger, comprising:
and when the liquid pressure in the annular space rises by a set amplitude within a set time and continues to rise, judging that the insertion end of the well completion string is in contact with the top of the insert return cylinder, and stopping lowering the well completion string.
Optionally, the set time is 5-10 s, and the set range is 200% -300%.
Optionally, said injecting a liquid into an annulus between said hanging string and said production casing, circulating said liquid within said annulus and said completion string, comprising:
and injecting clear water into an annular space between the suspension pipe column and the production casing by adopting a fracturing truck at a first pressure and a first discharge capacity, so that the liquid circularly flows in the annular space and the back insertion barrel until the pumping pressure of the fracturing truck is stabilized at a second pressure, and the discharge capacity is kept unchanged.
Optionally, the first pressure is 1-1.5 MPa, and the first discharge capacity is 0.1-0.5 m3/min。
Optionally, running the completion string into the production casing to a first depth with a drill pipe comprises:
acquiring a theoretical distance from the top of the back plugging cylinder to a wellhead;
and adopting a drill rod to lower the well completion pipe column into the production casing to the first depth according to the theoretical distance, wherein the difference value between the first depth and the theoretical distance is a set value, and the set value is 5-10 m.
Optionally, the obtaining a theoretical distance from the top of the back plugging cylinder to the wellhead comprises:
recording the running-in depth of the drill rod when the suspended pipe column is run into the production casing by adopting the drill rod;
and determining the running depth of the drill rod as the theoretical distance from the top of the back-inserting cylinder to the wellhead.
Optionally, the obtaining a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is in contact with the top of the stinger comprises:
when the completion string is run into the production casing to a first depth using a drill pipe, making a first marking at a first location of the drill pipe that is flush with a wellhead surface;
marking a second marking at a second location of the drill pipe that is flush with the surface of the wellhead when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
and determining the second distance according to the first depth and the distance from the first mark to the second mark.
Optionally, the obtaining a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is in contact with the top of the stinger comprises:
marking a second marking at a second location of the drill pipe that is flush with the surface of the wellhead when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
determining a distance of the second marking from the insertion end of the completion string as the second distance.
Optionally, said determining a length of said completion string from said second distance comprises:
acquiring the depth of the back inserting cylinder;
determining a sum of the second distance and the depth of the backinsertion barrel to be a length of the completion string.
The technical scheme provided by the embodiment of the disclosure has the following beneficial effects:
the completion string is lowered into the production casing to a first depth by the drill rod, so that the completion string is spaced from the top of the return plunger by a certain distance, and the inner hole of the completion string can be communicated with the annular space between the suspension string and the production casing. The annulus is then injected with a fluid so that the fluid can circulate within the annulus and the completion string. The completion string is then run into the production casing and the fluid pressure in the annulus is monitored in real time. When the insertion end of the completion string is contacted with the top of the back-insert barrel, the inner hole of the completion string is not communicated with the annular space, at the moment, liquid can not flow circularly in the annular space and the inner hole of the completion string any more, and the pressure of the liquid in the annular space can rise. Thus, by monitoring the change in fluid pressure within the annular space, it can be determined whether the male end of the completion string is in contact with the top of the stinger. Stopping lowering the completion string when the fluid pressure in the annular space reflects that the inserted end of the completion string contacts the top of the back-plugging barrel, and obtaining a second distance from the inserted end of the completion string to the wellhead at the moment. And finally, determining the length of the well pipe column according to the second distance. The method does not need to insert the well completion string into the back-insert barrel, reduces the possibility of damaging the sealing ring outside the well completion string, ensures the sealing effect between the well completion string and the back-insert barrel when the well completion string is inserted back into the back-insert barrel, improves the well completion quality and ensures the production capacity of the oil and gas well.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a method flow diagram of a method of determining a length of a completion string provided by an embodiment of the present disclosure;
FIG. 2 is a method flow diagram of another method of determining a length of a completion string provided by an embodiment of the present disclosure;
FIG. 3 is a running schematic of a hanging string provided by an embodiment of the present disclosure;
FIG. 4 is a schematic illustration of a completion string run into a production casing to a first depth provided by an embodiment of the present disclosure;
FIG. 5 is a schematic diagram of the insertion end of a completion string contacting the top of a stinger provided by an embodiment of the present disclosure.
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 the related art, when determining the length of the completion string, the completion string of the initial length is usually connected with a suspended weight meter, the completion string of the initial length is lowered into the well by using a drill pipe, and the contact between the completion string and the back plugging barrel is judged by observing the indication number of the suspended weight meter. The number of indications of the heaving gauge may be significantly reduced when the completion string is in contact with the stinger.
However, the manner in which the number of indications of the weight scale is relied upon to determine whether the completion string is in contact with the return spool is inaccurate. On the one hand, since the return stinger is usually several kilometers from the wellhead, the required length of the completion string is long and the weight is heavy when running downhole, and even if the completion string is subjected to a supporting force in contact with the return stinger, the speed of the supporting force transmitted to the suspended weight surface on the ground is slow and the force transmission is not sensitive. When the indication of the heaviness gauge changes, the completion string may have already been inserted into the backstinger, resulting in an inaccurate length of the finally determined completion string. On the other hand, even if the number of indications of the weight scale becomes significantly smaller, there is a possibility that the completion string will only encounter a blockage during the run in and will not contact the back-out casing, and therefore, the manner of determining whether the completion string is in contact with the back-out casing by means of the number of indications of the weight scale is inaccurate.
To ensure the accuracy of the target length of the completion string is determined, further downward pressure is applied to the completion string to fully insert the completion string into the stinger, typically when the indication of the catenary decreases significantly, which indicates that the completion string is fully inserted into the stinger. And then marking the position of the drill pipe, which is flush with the surface of the wellhead, taking out the completion string and the drill pipe together, and determining the target length of the required completion string according to the length from the marked position to the insertion end of the completion string. And then, the well completion pipe column is matched and lengthened to the target length, so that the well completion pipe column with the required length can be obtained. And finally, the well completion pipe column after being matched with the length is inserted back into the back insert barrel by adopting the drill rod, and the connection of the well completion pipe column and the back insert barrel can be completed.
However, in the process of determining the target length of the completion string, the completion string needs to be completely inserted into the back-plugging barrel, which may damage the sealing ring outside the completion string, affect the sealing effect between the completion string and the back-plugging barrel after the completion string is inserted back into the back-plugging barrel, and further affect the completion quality and the production capacity of the oil and gas well.
In order to solve the technical problem, an embodiment of the present disclosure provides a length determination method of a completion string, and fig. 1 is a flowchart of a length determination method of a completion string provided by an embodiment of the present disclosure, and as shown in fig. 1, the length determination method includes:
step 101, running a completion string into a production casing to a first depth using a drill pipe.
Wherein the first depth is a distance from the insertion end of the completion string to a wellhead.
Step 102, injecting a fluid into an annulus between the hanging string and the production casing to circulate the fluid through the annulus and the completion string.
The well completion pipe column is used for being inserted back into a back insertion barrel in the production casing, the back insertion barrel is positioned at the top of the suspension pipe column, and the suspension pipe column is positioned in the production casing in the well and a suspension packer is arranged between the suspension pipe column and the production casing. The suspension packer can play a sealing role, and after liquid is injected into an annular space between the suspension pipe column and the production casing, the liquid cannot continuously flow downwards but only flows above the suspension packer under the action of the suspension packer.
And 103, continuing to lower the completion string, and monitoring the liquid pressure in the annular space in real time.
And 104, stopping lowering the completion string when the liquid pressure in the annular space reflects that the insertion end of the completion string is contacted with the top of the back-plugging sleeve.
And 105, acquiring a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is contacted with the top of the back-plugging barrel.
And 106, determining the length of the completion string according to the second distance.
The embodiment of the disclosure enables the completion string to be spaced from the top of the return insert barrel by a certain distance by running the completion string into the production casing to a first depth by using the drill rod, and the inner hole of the completion string can be communicated with the annular space between the suspension string and the production casing. The annulus is then injected with a fluid so that the fluid can circulate within the annulus and the completion string. The completion string is then run into the production casing and the fluid pressure in the annulus is monitored in real time. When the insertion end of the completion string is contacted with the top of the back-insert barrel, the inner hole of the completion string is not communicated with the annular space, at the moment, liquid can not flow circularly in the annular space and the inner hole of the completion string any more, and the pressure of the liquid in the annular space can rise. Thus, by monitoring the change in fluid pressure within the annular space, it can be determined whether the male end of the completion string is in contact with the top of the stinger. Stopping lowering the completion string when the fluid pressure in the annular space reflects that the inserted end of the completion string contacts the top of the back-plugging barrel, and obtaining a second distance from the inserted end of the completion string to the wellhead at the moment. And finally, determining the length of the well pipe column according to the second distance. The method does not need to insert the well completion string into the back-insert barrel, reduces the possibility of damaging the sealing ring outside the well completion string, ensures the sealing effect between the well completion string and the back-insert barrel when the well completion string is inserted back into the back-insert barrel, improves the well completion quality and ensures the production capacity of the oil and gas well.
Fig. 2 is a flowchart of another method for determining the length of a completion string according to an embodiment of the present disclosure, as shown in fig. 2, the method includes:
and step 201, acquiring the theoretical distance from the top of the return inserting barrel to the wellhead.
Illustratively, step 201 may include:
recording the setting depth of a drill rod when the suspension pipe column is set into the production casing by adopting the drill rod;
and determining the running depth of the drill rod as the theoretical distance from the top of the back-inserting barrel to the wellhead.
FIG. 3 is a schematic diagram of a suspended string set in accordance with an embodiment of the present disclosure, as shown in FIG. 3, the suspended string 310 is connected to a drill pipe 320, a reinsertion cylinder 311 is located at the top of the suspended string 310, and the suspended string 310 is located in a production casing 300 in a well and a suspended packer 330 is provided between the suspended string 310 and the production casing 300.
Alternatively, after the suspended pipe string 310 is lowered to the set position, a mark may be made on the position of the drill pipe 320 flush with the wellhead, and then after the drill pipe 320 is taken out, the distance from the end of the drill pipe 320 connected with the suspended pipe string 310 to the mark is measured and recorded, so that the theoretical distance H1 from the top of the back plugging cylinder 311 to the wellhead can be obtained.
Since the length of the drill rod 320 is typically several kilometers and the weight is heavy, the drill rod 320 may be elongated in tension by the weight of the drill rod 320 itself during removal of the drill rod. Therefore, the distance from the measured end of the drill pipe 320 connected to the hanging string 310 to the mark may be different from the actual distance from the top of the reinsertion cylinder to the wellhead, and therefore, H1 obtained in this step is the theoretical distance from the top of the reinsertion cylinder 311 to the wellhead, not the actual distance.
Step 202, running the completion string into the production casing to a first depth using the drill pipe according to the theoretical distance.
Wherein, the difference value between the first depth and the theoretical distance is a set value a, and the set value a is 5-10 m. That is, the first depth is H1-a. The first depth is the distance from the insertion end of the completion string to the wellhead,
FIG. 4 is a schematic illustration of a completion string run into a production casing to a first depth as provided by an embodiment of the present disclosure, as shown in FIG. 4, when the distance from the insertion end of the completion string 410 to the wellhead is H1-a, and the theoretical distance from the insertion end of the completion string 410 to the top of the stinger 311 is a.
In the disclosed embodiment, H1 ═ 4000m, a ═ 10m, i.e., the first depth is 3990m, and completion string 410 is run into the production casing to a depth of 3990m, and run is stopped.
Step 203, injecting a fluid into the annular space between the hanging string and the production casing to circulate the fluid through the annular space and the completion string.
Referring to FIG. 4, the hanging packer 330 may now function as a seal. When fluid is injected into the annular space S between the hanging string 310 and the production casing 300, the fluid will not continue to flow downward but only above the hanging packer 330 under the action of the hanging packer 330.
Illustratively, step 203 may comprise:
clear water is injected into an annular space between the suspension pipe column and the production casing by adopting the fracturing truck at a first pressure and a first discharge capacity, so that liquid circularly flows in the annular space and the back insertion barrel until the pumping pressure of the fracturing truck is stabilized at a second pressure, and the discharge capacity is kept unchanged.
In order to ensure the sealing effect of the suspension packer, when a fracturing truck is used for injecting water into the annular space S between the suspension pipe column 310 and the production casing 300, clean water needs to be injected by adopting low pump pressure and small displacement.
Optionally, the first pressure is 1-1.5 MPa, and the first discharge capacity is 0.1-0.5 m3And/min. The sealing effect of the suspended packer can be guaranteed at the moment.
In the disclosed embodiment, the first pressure is 1.3MPa and the displacement is 0.15m3And/min, wherein the second pressure is 1.5MPa, namely the pumping pressure of the fracturing truck is stabilized at 1.5 MPa.
And step 204, continuing to lower the completion string, and monitoring the liquid pressure in the annular space in real time.
In the disclosed embodiment, the fluid pressure within the annulus S may be monitored in real time by electronic pressure gauges on the fracturing truck.
The lowering of the completion string is stopped when the fluid pressure in the annulus reflects that the inserted end of the completion string is in contact with the top of the stinger, step 205.
Illustratively, step 205 may include:
and when the liquid pressure in the annular space rises by a set amplitude within a set time and continues to rise, judging that the insertion end of the well completion string is in contact with the top of the plug-back sleeve, and stopping lowering the well completion string.
Fig. 5 is a schematic diagram of the contact between the insertion end of the completion string and the top of the back-plugging casing provided by the embodiment of the present disclosure, and as shown in fig. 5, the insertion end of the completion string 410 is further coaxially connected with an introduction section 411. The cross-sectional area of the lead-in section 411 decreases from the end of the lead-in section 411 connected to the insertion end of the completion string 410 to the end remote from the insertion end of the completion string 410 to facilitate insertion of the lead-in section 411 into the stinger 311 for guiding purposes.
At this point, the insertion end of completion string 410 is in contact with the top of the stinger 311 and the introduction section 411 is located in the stinger 311. The seal structure 410a on the outer wall of the completion string 410 is located at the top of the stinger 311, just sealing between the outer wall of the completion string 410 and the inner wall of the stinger 311. The inner bore of completion string 410 is not in communication with annulus S and fluid can no longer circulate through annulus S and the inner bore of completion string 410 and the pressure of the fluid in annulus S can rise in a short period of time.
In the embodiment of the disclosure, the setting time is 5-10 s, and the setting range is 200% -300%.
Wherein the rising amplitude of the liquid pressure in the annular space refers to the amplitude of the rise relative to the second pressure.
For example, in the disclosed embodiment, when the liquid pressure in the annular space rises from the second pressure of 1.5MPa to 4.5MPa within 5 seconds, the rising amplitude is (4.5MPa-1.5MPa)/1.5 MPa-200%.
A second distance from the insertion end of the completion string to the wellhead is obtained 206 when the insertion end of the completion string contacts the top of the back-insert barrel.
In one implementation of the embodiment of the present disclosure, step 206 may include:
in a first step, a first marking is made at a first location of a drill pipe that is flush with a surface of a wellhead while a completion string is run into a production casing to a first depth using the drill pipe.
Referring to FIG. 4, completion string 410 is run into production casing to a first depth H1-a and drill pipe 420 is provided with a first marker A1. At this point, the drill rod 420 is lowered 35m, HA1＝35m。
Second, a second marking is made at a second location of the drill pipe that is flush with the surface of the wellhead when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger.
Referring to FIG. 5, the inserted end of the completion string 410 is in contact with the top of the stinger 311 and the drillpipe 420 is provided with a second designation A2. At this point, the drill rod 420 is lowered 39m, HA2＝39m。
And thirdly, determining a second distance according to the first depth and the distance from the first mark to the second mark.
Referring to FIG. 5, the distance from the first marker A1 to the second marker A2 is Δ H at this time. I.e., completion string 410 continues to move down Δ H before the insertion end of completion string 410 contacts the top of stinger 311.
The sum of the first depth H1-a and the distance Δ H from the first mark to the second mark, i.e., the second distance H2, can be expressed as follows:
H2＝(H1-a)+ΔH
in the disclosed embodiments, Δ H ═ HA2-HA1＝39-35＝4m。H2＝3990m+4m＝3994m。
In another implementation manner of the embodiment of the present disclosure, step 206 may include:
making a second mark at a second position of the drill pipe, which is flush with the surface of the wellhead, when the liquid pressure in the annular space reflects that the insertion end of the completion string is in contact with the top of the back-plugging sleeve;
determining a distance of the second marking from the insertion end of the completion string as a second distance.
Illustratively, referring to FIG. 5, after the second marking A2 is made on the drillpipe, the drillpipe 420 and completion string 410 may be removed together and the second distance may be determined by measuring the distance H2 from the second marking A2 to the insertion end of the completion string.
And step 207, determining the length of the completion string according to the second distance.
Illustratively, step 207 may include:
obtaining a depth of the insertion barrel;
and determining the sum of the second distance and the depth of the back plugging barrel as the length of the completion string.
Referring to fig. 4 or 5, the depth of the reinsertion cylinder 311 is b.
In embodiments of the present disclosure, the depth of the stinger can be measured at the surface prior to running the hanging string into the production casing using the drill pipe.
Illustratively, the length H of the completion string is H2+ b.
In the disclosed embodiment, the back plugThe depth b of the bore 311 is 2m, and the length H of the completion string 410 is H2+ b 3994m +2m 3996 m. After the length of completion string 410 is determined, drill pipe 420 and completion string 410 may be removed and drill pipe 420 and completion string 410 may then be separated. The initial length of completion string 410 is (H1-a) -HA23990-35-3955 m, which is different from the target length 3996m by 41m, when the completion string 410 is configured, a string nipple with the length of 41m is coaxially welded at the end, opposite to the insertion end, of the completion string 410.
The embodiment of the disclosure enables the completion string to be spaced from the top of the return insert barrel by a certain distance by running the completion string into the production casing to a first depth by using the drill rod, and the inner hole of the completion string can be communicated with the annular space between the suspension string and the production casing. The annulus is then injected with a fluid so that the fluid can circulate within the annulus and the completion string. The completion string is then run into the production casing and the fluid pressure in the annulus is monitored in real time. When the insertion end of the completion string is contacted with the top of the back-insert barrel, the inner hole of the completion string is not communicated with the annular space, at the moment, liquid can not flow circularly in the annular space and the inner hole of the completion string any more, and the pressure of the liquid in the annular space can rise. Thus, by monitoring the change in fluid pressure within the annular space, it can be determined whether the male end of the completion string is in contact with the top of the stinger. Stopping lowering the completion string when the fluid pressure in the annular space reflects that the inserted end of the completion string contacts the top of the back-plugging barrel, and obtaining a second distance from the inserted end of the completion string to the wellhead at the moment. And finally, determining the length of the well pipe column according to the second distance. The method does not need to insert the well completion string into the back-insert barrel, reduces the possibility of damaging the sealing ring outside the well completion string, ensures the sealing effect between the well completion string and the back-insert barrel when the well completion string is inserted back into the back-insert barrel, improves the well completion quality and ensures the production capacity of the oil and gas well.
The above description is intended to be exemplary only and not to limit the present disclosure, and any modification, equivalent replacement, or improvement made without departing from the spirit and scope of the present disclosure is to be considered as the same as the present disclosure.

Claims (10)

1. A method of determining the length of a completion string for back-plugging into a back-plugging barrel within a production casing, the back-plugging barrel being located at the top of a suspended string located within the production casing in a well with a suspended packer located therebetween, the method comprising:
running the completion string into the production casing with a drill pipe to a first depth, the first depth being the distance from the insertion end of the completion string to the wellhead;
injecting a liquid into an annular space between the hanger string and the production casing, circulating the liquid within the annular space and the completion string;
continuing to lower the completion string and monitoring the fluid pressure in the annulus in real time;
stopping lowering the completion string when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
obtaining a second distance from the insertion end of the completion string to the wellhead when the insertion end of the completion string is in contact with the top of the back-plugging barrel;
determining a length of the completion string based on the second distance.
2. The length determination method of claim 1, wherein stopping running the completion string when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger comprises:
and when the liquid pressure in the annular space rises by a set amplitude within a set time and continues to rise, judging that the insertion end of the well completion string is in contact with the top of the insert return cylinder, and stopping lowering the well completion string.
3. The length determination method according to claim 2, wherein the set time is 5 to 10 seconds, and the set width is 200 to 300%.
4. The length determination method of claim 1, wherein said injecting a liquid into an annular space between said hanging string and said production casing to circulate said liquid within said annular space and said completion string comprises:
and injecting clear water into an annular space between the suspension pipe column and the production casing by adopting a fracturing truck at a first pressure and a first discharge capacity, so that the liquid circularly flows in the annular space and the back insertion barrel until the pumping pressure of the fracturing truck is stabilized at a second pressure, and the discharge capacity is kept unchanged.
5. The length determination method according to claim 4, wherein the first pressure is 1 to 1.5MPa, and the first displacement is 0.1 to 0.5m3/min。
6. The length determination method of claim 1, wherein running the completion string into the production casing to a first depth using a drill pipe comprises:
acquiring a theoretical distance from the top of the back plugging cylinder to a wellhead;
and adopting a drill rod to lower the well completion pipe column into the production casing to the first depth according to the theoretical distance, wherein the difference value between the first depth and the theoretical distance is a set value, and the set value is 5-10 m.
7. The length determination method of claim 6, wherein the obtaining a theoretical distance from a top of the backinsertion cartridge to a wellhead comprises:
recording the running-in depth of the drill rod when the suspended pipe column is run into the production casing by adopting the drill rod;
and determining the running depth of the drill rod as the theoretical distance from the top of the back-inserting cylinder to the wellhead.
8. The length determination method of claim 1, wherein obtaining a second distance from the insertion end of the completion string to a wellhead when the insertion end of the completion string is in contact with a top of the stinger comprises:
when the completion string is run into the production casing to a first depth using a drill pipe, making a first marking at a first location of the drill pipe that is flush with a wellhead surface;
marking a second marking at a second location of the drill pipe that is flush with the surface of the wellhead when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
and determining the second distance according to the first depth and the distance from the first mark to the second mark.
9. The length determination method of claim 1, wherein obtaining a second distance from the insertion end of the completion string to a wellhead when the insertion end of the completion string is in contact with a top of the stinger comprises:
marking a second marking at a second location of the drill pipe that is flush with the surface of the wellhead when the fluid pressure within the annular space reflects that the insertion end of the completion string is in contact with the top of the stinger;
determining a distance of the second marking from the insertion end of the completion string as the second distance.
10. The length determination method according to any one of claims 1 to 9, wherein determining the length of the completion string according to the second distance comprises:
acquiring the depth of the back inserting cylinder;
determining a sum of the second distance and the depth of the backinsertion barrel to be a length of the completion string.
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