阅读说明：本技术 气井自平衡防污染完井管柱 (Self-balancing anti-pollution well completion pipe string for gas well ) 是由 岳慧 邓大伟 王立双 于 2019-11-11 设计创作，主要内容包括：本发明提出了一种气井自平衡防污染完井管柱,包括,下部丢手管柱,其包括下部油管、设置在下部油管上的封隔器,以及连接在所述封隔器上部的内插管；上部完井管柱,其包括由上至下依次设置在上部油管上的安全阀及外插管,所述外插管套接在所述内插管外。本发明的气井自平衡防污染完井管柱两处采用U型管原理,一方面避免了压井过程中的重力置换,实现了气井的长期压稳,从而保证作业过程的井控安全；另一方面采用丢手回插管柱,减小了上部管柱的起出风险；同时上部管柱内外压力自动平衡,且气体不会窜入油套环空内,保证了套管安全；另外本发明还具有环空加防腐剂、泡沫剂等功能。(The invention provides a self-balancing anti-pollution well completion pipe column for a gas well, which comprises a lower releasing pipe column, a lower anti-pollution pipe column and an inner inserting pipe, wherein the lower releasing pipe column comprises a lower oil pipe, a packer arranged on the lower oil pipe, and the inner inserting pipe is connected to the upper part of the packer; and the upper well completion pipe column comprises a safety valve and an outer sleeve which are sequentially arranged on the upper oil pipe from top to bottom, and the outer sleeve is sleeved outside the inner sleeve. According to the self-balancing anti-pollution well completion pipe column for the gas well, the principle of the U-shaped pipe is adopted at two positions, so that on one hand, gravity displacement in the well killing process is avoided, and long-term pressure stability of the gas well is realized, and thus the well control safety in the operation process is ensured; on the other hand, the releasing and back-inserting pipe column is adopted, so that the lifting risk of the upper pipe column is reduced; meanwhile, the internal and external pressures of the upper tubular column are automatically balanced, and gas cannot flow into the oil sleeve annulus, so that the safety of the sleeve is ensured; in addition, the invention also has the functions of adding a preservative, a foaming agent and the like into the annular space.)

1. A self-balancing anti-pollution well completion pipe column of a gas well is characterized by comprising,

the lower releasing tubular column comprises a lower oil pipe, a packer arranged on the lower oil pipe and an inner insert pipe connected to the upper part of the packer;

and the upper well completion pipe column comprises a safety valve and an outer sleeve which are sequentially arranged on the upper oil pipe from top to bottom, and the outer sleeve is sleeved outside the inner sleeve.

2. The gas well self-balancing anti-contamination completion string according to claim 1, further comprising a gas invasion prevention device located at a lower portion of the packer.

3. The self-balancing anti-pollution well completion string for the gas well as claimed in claim 2, wherein the anti-gas invasion device comprises a double-layer pipe, the double-layer pipe comprises a double-layer pipe outer pipe and a double-layer pipe inner pipe, the bottom of the double-layer pipe outer pipe is closed, the top of the double-layer pipe outer pipe is provided with an opening, the double-layer pipe inner pipe is inserted into the interior of the double-layer pipe outer pipe from the opening, and the bottom of the double-layer pipe inner pipe is open.

4. The gas well self-balancing anti-contamination completion string according to any one of claims 1 to 3, wherein the upper tubing is a nickel-based alloy tubing.

5. The self-balancing anti-contamination completion string for gas wells according to any of claims 1 to 3, wherein the top of the inner casing is sealed from the outer casing.

6. The self-balancing anti-contamination completion string for gas wells according to any of claims 1 to 3, wherein a gap is provided between the top of the inner insert and the outer insert.

Technical Field

The invention relates to the technical field of petroleum engineering well completion, in particular to a self-balancing anti-pollution well completion pipe string for a gas well.

Background

The vast majority of natural gas wells are currently completed by using packers, as shown in fig. 1, the packer is used for blocking off the oil casing annulus, so that natural gas is prevented from entering the casing, the casing and a wellhead are subjected to high pressure, the well control risk is reduced, and H2S and CO2 in the natural gas are prevented from contacting the casing and the wellhead and corroding the casing and the wellhead.

However, the completion of the well by adopting the packer has higher requirements on the performances of pressure bearing and the like of the packer, and meanwhile, because the packer is difficult to unseal, even if the packer can be unsealed, the well must be pressured when the tubular column is operated due to the well control requirement, but the well is difficult to stabilize when the well is pressured, because the gas density is low and the liquid density is high, the gas in the shaft is replaced by the gravity, the gas is moved upwards, the well killing liquid is easy to leak into the stratum, particularly for a fracture-cavity type gas reservoir, the risk is extremely high, even if the gas well is stabilized, the well killing liquid can cause great damage to the stratum, the yield is reduced greatly after the operation, and the gas well is also the main reason for the operation without repairing the well as far as possible.

Disclosure of Invention

In order to solve the technical problem, the invention provides a self-balancing anti-pollution well completion pipe string for a gas well

The invention relates to a self-balancing anti-pollution well completion pipe string for a gas well, which comprises,

the lower releasing tubular column comprises a lower oil pipe, a packer arranged on the lower oil pipe and an inner insert pipe connected to the upper part of the packer;

and the upper well completion pipe column comprises a safety valve and an outer sleeve which are sequentially arranged on the upper oil pipe from top to bottom, and the outer sleeve is sleeved outside the inner sleeve.

In one embodiment, the completion string further comprises a gas invasion prevention device located below the packer.

In one embodiment, the gas invasion preventing device comprises a double-layer pipe, the double-layer pipe comprises a double-layer pipe outer pipe and a double-layer pipe inner pipe, the bottom of the double-layer pipe outer pipe is closed, the top of the double-layer pipe outer pipe is provided with an opening, the double-layer pipe inner pipe is inserted into the inside of the double-layer pipe outer pipe from the opening, and the bottom of the double-layer pipe inner pipe is in an opening shape.

Compared with the prior art, the self-balancing anti-pollution well completion pipe column for the gas well can realize long-term stable well killing during replacement of the upper pipe column in later operation, avoids well control risks, and is simple and convenient to operate because the upper pipe column is not provided with a packer; the annular pressure and the gas pressure in the oil pipe are automatically balanced, gas-liquid displacement cannot be generated, and the packer does not bear differential pressure, so that the reliability of the packer and the reliability of the pipe column are facilitated; and thirdly, preservatives, foaming agents and the like can be added through the annular space, so that the functions of corrosion prevention, foam discharging and the like are realized.

The technical features described above can be combined in various technically feasible ways to produce new embodiments, as long as the object of the invention is achieved.

Drawings

The invention will be described in more detail hereinafter on the basis of non-limiting examples only and with reference to the accompanying drawings. Wherein:

FIG. 1 shows a schematic representation of a prior art completion string configuration;

FIG. 2 shows a schematic structural diagram of a first embodiment of a self-balancing anti-contamination completion string for a gas well according to the present invention;

FIG. 3 shows a schematic diagram of the lower release string of the completion string of FIG. 2;

fig. 4 shows a schematic structural diagram of a second embodiment of the self-balancing anti-contamination completion string for a gas well of the invention.

In the drawings, like components are denoted by like reference numerals. The figures are not drawn to scale.

Wherein the reference numerals are:

1. a self-balancing anti-pollution well completion pipe string of the gas well; 10. an upper completion string; 101. a safety valve; 102. an upper oil pipe; 103. an outer cannula; 20. a lower releasing tubular column; 201. inserting a tube; 202. a packer; 203. a lower oil pipe; 30. a gas intrusion prevention device; 301. a double-layer tube outer tube; 302. a double-layer tube inner tube; 100. a safety valve; 200. a sleeve; 300. an oil pipe; 400. and (4) a packer.

Detailed Description

The invention will be described in further detail below with reference to the drawings and specific examples. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.

Parts which are not described in the invention can be realized by adopting or referring to the prior art.

As shown in FIG. 1, most of the existing natural gas wells are completed by using a packer 400, namely, the packer 400 is used for sealing off the oil casing annulus to prevent natural gas from entering the casing 200, so that the casing 200 and a well head bear high pressure, the well control risk is reduced, and meanwhile, H in the natural gas can be avoided₂S and CO₂Contacting the casing 200 and the wellhead and corroding the casing 200 and the wellhead.

However, the completion of the well by adopting the packer has higher requirements on the performances of pressure bearing and the like of the packer, and meanwhile, because the packer is difficult to unseal, even if the packer can be unsealed, the well must be pressured when the tubular column is operated due to the well control requirement, but the well is difficult to stabilize when the well is pressured, because the gas density is low and the liquid density is high, the gas in the shaft is replaced by the gravity, the gas is moved upwards, the well killing liquid is easy to leak into the stratum, particularly for a fracture-cavity type gas reservoir, the risk is extremely high, even if the gas well is stabilized, the well killing liquid can cause great damage to the stratum, the yield is reduced greatly after the operation, and the gas well is also the main reason for the operation without repairing the well as far as possible.

In order to solve the problems, the invention provides a novel well completion pipe string, so that when operation is needed in the later period of a gas well, on one hand, the gas well can be safely stabilized for a long time, the construction safety is ensured, on the other hand, the stratum is prevented from being polluted by the loss of well killing fluid, the stress condition of a packer is improved, and the reliability of the pipe string is improved.

Implement one

As shown in fig. 2 and 3, the self-balancing anti-contamination well completion string 1 for gas wells of the present invention comprises an upper well completion string 10 and a lower releasing string 20, wherein the upper well completion string 10 comprises a safety valve 101 and an outer casing 103 sequentially arranged on an upper oil pipe 102 from top to bottom, the lower releasing string 20 comprises a lower oil pipe 203, a packer 202 arranged on the lower oil pipe 203, and an inner casing 201 connected to the upper part of the packer 202, and the upper well completion string 10 and the lower releasing string 20 are connected together by sleeving the outer casing 103 outside the inner casing 201, so as to form the self-balancing anti-contamination well completion string 1 for complete gas wells.

Preferably, the diameter of outer cannula 103 is 1 to 2.5 inches greater than the diameter of inner cannula 201.

When the packer is used, the lower releasing string 20 is put into a well, the packer 202 is set above a gas layer section, and the opening of the lower oil pipe 203 is positioned in a pocket below a gas layer perforation section. Because the lower releasing pipe column 20 at the lower part is not provided with a safety valve, the operation is convenient, a non-killing operation process can be adopted, the stratum can not be polluted under the condition of realizing well control safety, and the releasing pipe column is particularly useful for low-pressure wells.

After packer 202 is set, the upper and lower tubing 203 of lower release string 20 is filled with a kill fluid, preferably having a specific gravity equal to the gas zone pressure coefficient, so that the gas and fluid column pressures are balanced. In the shaft at the perforation section, gas is above liquid, the gas cannot enter the bottom opening of the lower oil pipe 203 downwards to cause gas invasion, and the liquid cannot enter the stratum upwards to cause leakage, so that the well pressure can be stabilized stably for a long time.

After setting, since the gas well is already stable, the upper completion string 10 can be safely lowered, as shown in FIG. 3, with the outer sleeve 103 being fitted over the inner sleeve 21 of the lower release string 20, with the purpose of creating a flow path there around, which prevents gas-liquid displacement. The outer cannula 103 may be sealed to the top of the inner cannula 21 or a gap may be provided.

When in production, induced spraying is carried out in the oil pipe, and gas is produced from the oil pipe after liquid in the pipe column is discharged. Because the gas pressure and the liquid column pressure of intubate department are equal, therefore the liquid in the annular space can not get into in the oil pipe, gas in the oil pipe also can not get into the annular space, consequently even the intubate is unsealed can not cause gas to get into annular space contact and corrosion sleeve pipe and well head, annular space liquid column pressure can offset gas pressure (if when kill-job fluid proportion is less than the formation pressure coefficient, liquid pressure can not offset formation pressure completely, then the well head can take certain pressure, well head sleeve pipe pressure equals the difference of formation pressure and liquid column pressure, pressure is lower).

When formation pressure reduces, the liquid column pressure in the annular space is higher than gas pressure, and liquid in the annular space can flow into in the oil pipe automatically, is carried out ground by gas.

Because the insertion pipe does not need to be sealed, the pressure above and below the packer is equal, and therefore the reliability of the packer is improved.

When the upper portion leakage appears in later stage well completion tubular column, block up, when relief valve inefficacy scheduling problem, can go into kill fluid or oil pipe horizontal push kill well from the annular space pump, because 23 bottoms of lower part tubular columns are below the perforation section, consequently can not produce the gas-liquid replacement phenomenon, consequently can be with well pressure steady, consequently can safely take off and change upper portion well completion tubular column 10, upper portion well completion tubular column 10 does not take the packer in addition, the tubular column is taken off simple and conveniently, kill fluid can not get into the stratum simultaneously, cause the pollution to the stratum.

When the stratum produces water, the foaming agent can be added into the sleeve to realize the foam water drainage and gas recovery process. Or the small oil pipe is replaced to realize the optimization of the drainage and gas production of the pipe column.

The preservative can be dripped from the sleeve at any time, and the preservative enters the oil pipe from the insertion pipe to achieve the purpose of preventing the oil pipe from being corroded.

Example two

As shown in fig. 4, the self-balancing contamination-prevention completion string 1 for the gas well of the present invention may further comprise a gas invasion preventing device 30, wherein the gas invasion preventing device 30 is positioned at the lower part of the packer 22.

Preferably, the gas intrusion prevention device 30 is a double-layer tube structure, and includes a double-layer tube outer tube 301 and a double-layer tube inner tube 302, the bottom of the double-layer tube outer tube 301 is closed, the top of the double-layer tube outer tube 301 is provided with an opening, the double-layer tube inner tube 302 is inserted into the inside of the double-layer tube outer tube 301 from the opening, and the bottom of the double-layer tube inner tube 302 is open. Therefore, the flow channel forms upward and downward flow around the position, so that gas-liquid replacement is prevented, and the effects of gas invasion prevention and leakage prevention during well killing operation are achieved.

Preferably, the diameter of the outer tube 301 of the double tube is 1 to 2.5 inches greater than the diameter of the inner tube 302 of the double tube.

The gas intrusion prevention device 30 may be connected to the lower tubing 203 or may be directly connected to the lower portion of the packer, and the lower tubing 203 is replaced by a double tubing inner tube 302, which functions as the lower tubing.

EXAMPLE III

The self-balancing anti-pollution well completion pipe column for the gas well provided by the invention is implemented on site by taking a plain gas field as an example.

The plain gas field block is a high-pressure high-yield high-sulfur hydrogen sulfide gas field, the gas reservoir is buried deep by about 5000m, the pressure of a gas layer of the Changxing group is about 75MPa, the pressure coefficient is about 1.5, a stratum contains cracks, and killing wells are easy to leak and difficult to stabilize. And the hydrogen sulfide content is high, the operation risk is extremely high, so a permanent packer completion string is generally adopted, after the completion string is put down once, the operation and the string replacement are basically not considered in the later period, but the cement well abandoning treatment can be usually carried out only when the packer and the safety valve fail.

By utilizing the self-balancing anti-pollution completion pipe string of the gas well, the self-balancing anti-pollution completion pipe string shown in figure 3 can be put into the gas well with perforated completion, and the self-balancing anti-pollution completion pipe string shown in figure 4 can be put into the gas well with open hole completion.

The lower release pipe column 20 can be run in by using a drill rod, and because the drill rod is usually run in by a stand, the running speed is high, the empty well casing time can be reduced, and the well control risk is reduced.

After the packer 202 is set, because the opening of the lower oil pipe 203 (the lower gas invasion preventing device 30 for an open hole well) is positioned below the perforation section, gas-liquid displacement in a shaft can be avoided, and the specific gravity of the kill fluid is designed to be equal to the formation pressure coefficient, so that the wellhead can be prevented from overflowing and leaking, the long-term stable kill can be realized, and the well control risk can be greatly reduced.

After the well killing is stable, the well killing can be safely released and sent out, a sealing pipe column (such as a drill rod) can be set, then the upper well completion pipe column 10 is put in, the upper well completion pipe column 10 is slow to set because a nickel-based alloy oil pipe and a gas sealing thread are adopted, and the safety valve is provided with an external pipeline, but the well killing is stable for a long time because the gas well can not be replaced by gas and liquid, so that the risk of setting out the pipe column can be greatly reduced.

After the upper completion string 10 is put in, a wellhead is installed, a pipeline is connected, low-density well killing fluid is slowly circulated reversely from the casing, the pressure in the pipe is reduced, and gas enters the oil pipe to realize induced flow.

The casing will be under pressure because the annulus mud weight is slightly less than the formation pressure coefficient. (e.g., if 5000m vertical depth, formation pressure coefficient 1.5, kill fluid density 1.4, casing pressure 5 MPa). But gas does not enter the casing.

When the formation pressure is reduced in the later period, if the pressure coefficient is reduced to 1.2, the liquid in the annular space can be reduced by about 1000m, and the automatic gas pressure balance is realized. The low-density well killing fluid can be replaced at proper time according to the pressure of the oil casing so as to keep the casing full of the fluid.

When the tubular column needs to be replaced in the later period, high-density killing fluid can be filled into the casing, enters the oil pipe and is filled with the oil pipe, but does not leak into the stratum, and therefore the pressure of the gas well can be stabilized. The pipe column can be safely replaced at this time.

In the production process, a foaming agent or a preservative can be added into the casing at any time, so that the aims of foam drainage and gas production or delaying the corrosion prevention of the oil pipe are fulfilled.

According to the self-balancing anti-pollution well completion pipe column for the gas well, the principle of the U-shaped pipe is adopted at two positions, so that on one hand, gravity displacement in the well killing process is avoided, and long-term pressure stability of the gas well is realized, and thus the well control safety in the operation process is ensured; meanwhile, the upper pipe column is not provided with a packer, so that the operation is simple and convenient; the releasing and back-inserting pipe column is adopted, so that the lifting risk of the upper pipe column is reduced; meanwhile, the internal pressure and the external pressure of the upper pipe column are automatically balanced, gas cannot flow into the oil sleeve annulus, gas-liquid displacement cannot be generated, the packer does not bear pressure difference, the reliability of the packer and the pipe column is facilitated, and the safety of the casing is ensured; antiseptic, foaming agent and the like can be added through the annular space, and functions such as anticorrosion and foam discharging are achieved.

It will thus be appreciated by those skilled in the art that while the invention has been described with reference to a preferred embodiment, various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.