阅读说明：本技术 一种基于高密度均相压井液的平衡压修井方法 (Balanced pressure well repairing method based on high-density homogeneous well killing fluid ) 是由 朱西柱 李立标 吴春生 燕永利 牛梦龙 涂建 王锋涛 于长龙 孙爽 杨耀春 何吉 于 2021-07-19 设计创作，主要内容包括：一种基于高密度均相压井液的平衡压修井方法,首先将硝酸钠和氯化钙混合后加入到循环加药系统,然后加入溴化锌和缓蚀剂；然后在循环加药系统内的水的中循环溶解,得到密度均匀的压井液；检查配制压井液是否达标,若是压井液达标则进行压井液的注入、通洗井阶段；最后查看井口是否合格,如果井口不溢流、倒吸,则压井合格；压井合格后进行起管柱、检串过程,再驱替压井液,完成修井。本发明中平衡压修井不再用大密度非均相压井液压井,使用的高密度均相压井液,配制过程简单且不存在固相,不易堵塞储层。本发明中平衡压修井是在不封堵油管及套管的条件下可以进行地面上的常压修井,其施工周期短、需要的设备少,可以大程度降低修井费用。(A well repairing method based on balanced pressure of high-density homogeneous well killing fluid, add sodium nitrate and calcium chloride into circulating medicine system after mixing at first, then add zinc bromide and corrosion inhibitor; then circularly dissolving in water in a circulating dosing system to obtain well killing fluid with uniform density; checking whether the prepared well killing fluid reaches the standard, and if the prepared well killing fluid reaches the standard, injecting the well killing fluid and cleaning the well; finally checking whether the well mouth is qualified, and if the well mouth does not overflow or suck backwards, controlling the well to be qualified; and (4) after the well killing is qualified, performing the processes of pipe string lifting and string detection, and then displacing well killing fluid to complete well repair. The balanced-pressure well repairing method does not need a high-density heterogeneous well killing hydraulic well, and the used high-density homogeneous well killing fluid has the advantages of simple preparation process, no solid phase and difficulty in blocking a reservoir. The balanced pressure well repair of the invention can be carried out under normal pressure on the ground under the condition of not plugging an oil pipe and a casing, has short construction period and less required equipment, and can greatly reduce the well repair cost.)

1. A balanced pressure well repairing method based on high-density homogeneous well killing fluid is characterized by comprising the following steps:

firstly, mixing sodium nitrate and calcium chloride, adding the mixture into a circulating dosing system, and then adding zinc bromide and a corrosion inhibitor;

step two, circularly dissolving in water in a circulating dosing system to obtain well killing fluid with uniform density;

checking whether the prepared well killing fluid reaches the standard, and if the prepared well killing fluid reaches the standard, injecting the well killing fluid and cleaning the well; finally checking whether the well mouth is qualified, and if the well mouth does not overflow or suck backwards, controlling the well to be qualified;

and step four, after the well killing is qualified, the pipe column is taken up and the string is detected, and then the well killing fluid is displaced to complete the well repairing.

2. The well repairing method based on the balanced pressure of the high-density homogeneous well killing fluid is characterized in that in the first step, the circulating dosing system comprises a storage tank, and the water flow in the storage tank is 200L/min-400L/min.

3. The method for well intervention based on high density homogeneous well killing fluid of claim 1, wherein the density of the well killing fluid in the second step is calculated by the following formula;

ρ_{theory of the invention}gH₁＝ρ_{Practice of}g(H₁-h) (3)

In the formula (3), ρ_{Theory of the invention}Density of the well killing fluid theoretically required, g is gravitational acceleration, rho_{Practice of}To actual kill fluid density, H₁Is the vertical height and h is the buffer height.

4. The method for carrying out balanced pressure well workover on the basis of the high-density homogeneous well killing fluid according to claim 3, wherein the buffer height is 50-100 m.

5. The method of claim 3, wherein the theoretical desired kill fluid density is calculated by the formula:

P_downhole＝ρ_{Theory of the invention}×g×H₁ (2)

In the formula (2), P_{Shut-in well}For shut-in pressure, H₁Is the vertical height, p_{Theory of the invention}G is the gravity acceleration, which is the density of the well killing fluid required by theory.

6. The high-density homogeneous well killing fluid-based equilibrium well killing method according to claim 1, wherein the time of circulating dissolution is 2-5 hours; in the second step, each well killing fluid comprises: water: 0.485m³～0.597m³110.44-215.53 kg of calcium chloride, 466.02-573.13 kg of sodium nitrate, 142-542.7 kg of zinc bromide and 100-200 kg of HS-3 imidazole quaternary ammonium salt.

7. The balanced workover method based on high-density homogeneous well killing fluid of claim 1 or 6, wherein, in the second step, the density of the well killing fluid is in the range of 1.4g/cm³～1.7g/cm³。

8. The method for balanced well intervention based on high density homogeneous well intervention fluid as claimed in claim 1 wherein the well intervention fluid is injected by injecting the well intervention fluid into the annulus first and then injecting the well intervention fluid from the tubing port after the annulus is filled, or by reverse circulation injection, and the volume of the annulus, tubing, volume to be replenished and wellbore required for the well intervention fluid is calculated by the following formula:

in formulae (4), (5), (6) and (7), D₁Is the inner diameter of the casing, D₂Is the inner diameter of the oil pipe, D₃Is the outer diameter of the oil pipe, v_{Annular space}Is the annular volume, v_{Oil pipe}Is the volume v of the oil pipe_SupplementTo supplement the volume v_ShaftIs the total volume of the wellbore.

9. The balanced-pressure well repairing method based on the high-density homogeneous well killing fluid as claimed in claim 1, wherein when the well killing fluid is reused, the well killing fluid is used as a base fluid according to the well shut-in pressure and the vertical height of the next well, and medicines are added into the base fluid to adjust the density so as to meet the working requirement of the next well.

10. The method for balanced well intervention based on the high density homogeneous well killing fluid of claim 9, wherein the density adjustment is performed by the following steps when the well killing fluid is repeatedly used:

calculating the required actual well killing fluid density according to the well closing pressure and the vertical height of the new well;

② calculating the required amount of the base liquid by the following formula and adjusting the density of the base liquid to 1.5g/cm³；

V_{Volume of well killing fluid}＝α×V_{Well bore volume} (9)

Wherein D is₁Is the internal diameter of the annulus, H is the vertical height, beta is the expansion rate of the well killing fluid, alpha is the coefficient, rho: density of the base fluid; z is the dilution; x is the required base liquid amount; n is theoretical dilution water consumption;

calculating the addition of sodium nitrate, calcium chloride and zinc bromide according to the theoretical dilution water consumption n:

m_{sodium nitrate}＝n·527.47kg；

m_{Calcium chloride}＝n·243.96kg；

m_{Zinc bromide}＝n·54.95kg；

Wherein m is_{Sodium nitrate}M is the amount of sodium nitrate added_{Calcium chloride}M is the amount of calcium chloride added_{Zinc bromide}Is the adding amount of zinc bromide;

thirdly, calculating the density of each square of well killing fluid from 1.5g/cm³The amount of zinc bromide added is required to adjust to the actual kill fluid density.

Technical Field

The invention relates to the technical field of petroleum engineering, in particular to a balanced pressure well repairing method based on high-density homogeneous well killing fluid.

Background

In recent years, with rapid development of economy, the national demand for oil and gas resources has increased. The exploitation conditions of the oil well and the technical level of the well repairing process have a great influence on the efficiency and productivity of the whole petroleum engineering. In addition, the technology modernization can effectively increase the petroleum content and better meet the huge petroleum needs of China. If the well repairing process of the underground operation link of the petroleum project is not obviously improved, the whole petroleum project has serious problems and even influences the development process of the whole petroleum project. Therefore, the promotion of the well repairing process and the promotion process of the downhole operation of the petroleum project is very critical.

Killing the well mainly includes filling high polymer temporary plugging agent or high-density killing fluid into oil and water wells to balance the bottom pressure. The limitation of the high polymer temporary plugging agent can be obtained by looking up data: the preparation process is complex. Secondly, the high polymer temporary plugging agent has a solid phase and is easy to plug a reservoir stratum. And thirdly, the addition of the blocking remover is easy to cause secondary pollution. Fourthly, the method cannot be used repeatedly, and has high cost and great pollution.

Therefore, the high polymer temporary plugging agent has been abandoned by most oil fields due to the limitation, and nowadays, high-density well control fluid is mostly adopted in the oil field to balance the bottom hole pressure. The high-density well killing fluid is divided into an organic well killing fluid and an inorganic well killing fluid, and by comparing the two well killing fluids, the inorganic well killing fluid can be found to have the following four advantages:

the preparation process is convenient. ② no inflammable and explosive organic matters are contained. And the environment and the stratum are not polluted. High density and repeated use.

Therefore, inorganic kill fluids are becoming the best option for balancing bottom hole pressure in future pressurized workover operations.

The conventional pressure relief string detection mode and the conventional pressure belt string detection mode are adopted in the current string detection mode. Influenced by stratum physical properties, the conventional string inspection has long pressure relief period, and the transportation of the flowback liquid has environmental protection risks. The pressure detection string has the problems of high cost, long construction period, high pressure safety risk and the like. A new operation form is urgently needed to replace operation under pressure, improve the working condition of a shaft, ensure fine and effective water injection and promote the stable construction and development of an oil reservoir.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a balanced pressure well repairing method based on high-density homogeneous pressure well repairing fluid, which can balance the formation pressure and can carry out the balanced pressure well repairing of the normal pressure well repairing on the ground under the condition of not plugging an oil pipe and a casing.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a balanced pressure well repairing method based on high-density homogeneous well killing fluid comprises the following steps:

firstly, mixing sodium nitrate and calcium chloride, adding the mixture into a circulating dosing system, and then adding zinc bromide and a corrosion inhibitor;

step two, circularly dissolving in water in a circulating dosing system to obtain well killing fluid with uniform density;

checking whether the prepared well killing fluid reaches the standard, and if the prepared well killing fluid reaches the standard, injecting the well killing fluid and cleaning the well; finally checking whether the well mouth is qualified, and if the well mouth does not overflow or suck backwards, controlling the well to be qualified;

and step four, after the well killing is qualified, the pipe column is taken up and the string is detected, and then the well killing fluid is displaced to complete the well repairing.

The invention has the further improvement that in the step one, the circulating dosing system comprises a storage tank, and the water flow in the storage tank is 200-400L/min.

The invention is further improved in that the density of the pressurized well fluid in the second step is calculated by the following formula;

ρ_{theory of the invention}gH₁＝ρ_{Practice of}g(H₁-h) (3)

In the formula (3), ρ_{Theory of the invention}Density of the well killing fluid theoretically required, g is gravitational acceleration, rho_{Practice of}To actual kill fluid density, H₁Is the vertical height and h is the buffer height.

The invention is further improved in that the buffer height is 50-100 m.

A further improvement of the invention is that the theoretical required kill fluid density is calculated by the formula:

P_downhole＝ρ_{Theory of the invention}×g×H₁ (2)

In the formula (2), P_{Shut-in well}For shut-in pressure, H₁Is the vertical height, p_{Theory of the invention}G is the gravity acceleration, which is the density of the well killing fluid required by theory.

The further improvement of the invention is that the time of circulating dissolution is 2-5 hours; in the second step, each well killing fluid comprises: water: 0.485m³～0.597m³110.44-215.53 kg of calcium chloride, 466.02-573.13 kg of sodium nitrate, 142-542.7 kg of zinc bromide and 100-200 kg of HS-3 imidazole quaternary ammonium salt.

The invention is further improved in that in the second step, the density of the well killing fluid is in the range of 1.4g/cm³～1.7g/cm³。

The invention has the further improvement that when the well killing fluid is injected, the injection is carried out in a mode of injecting the well killing fluid into the annular space firstly and injecting the well killing fluid from an oil pipe port after the injection is completed, or in a reverse circulation injection mode, and the annular space, the oil pipe, the volume to be supplemented and the volume of the well killing fluid required by a shaft are calculated by the following formula:

in formulae (4), (5), (6) and (7), D₁Is the inner diameter of the casing, D₂Is the inner diameter of the oil pipe, D₃Is the outer diameter of the oil pipe, v_{Annular space}Is the annular volume, v_{Oil pipe}Is the volume v of the oil pipe_SupplementTo supplement the volume v_ShaftIs the total volume of the wellbore.

The invention is further improved in that when the well killing fluid is reused, the well killing fluid is used as base fluid according to the well shut-in pressure and the vertical height of the next well, and medicines are added into the base fluid for density adjustment so as to meet the working requirement of the next well.

The invention is further improved in that when the well killing fluid is repeatedly used, the density adjustment process is as follows:

calculating the required actual well killing fluid density according to the well closing pressure and the vertical height of the new well;

② calculating the required amount of the base liquid by the following formula and adjusting the density of the base liquid to 1.5g/cm³；

V_{Volume of well killing fluid}＝α×V_{Well bore volume} (9)

Wherein D is₁Is the internal diameter of the annulus, H is the vertical height, beta is the expansion rate of the well killing fluid, alpha is the coefficient, rho: density of the base fluid; z is the dilution; x is the required base liquid amount; n is theoretical dilution water consumption;

calculating the addition of sodium nitrate, calcium chloride and zinc bromide according to the theoretical dilution water consumption n:

m_{sodium nitrate}＝n·527.47kg；

m_{Calcium chloride}＝n·243.96kg；

m_{Zinc bromide}＝n·54.95kg；

Wherein m is_{Sodium nitrate}M is the amount of sodium nitrate added_{Calcium chloride}M is the amount of calcium chloride added_{Zinc bromide}Is the adding amount of zinc bromide;

thirdly, calculating the density of each square of well killing fluid from 1.5g/cm³The amount of zinc bromide added is required to adjust to the actual kill fluid density.

Compared with the prior art, the invention has the following beneficial effects:

compared with the conventional pressure relief detection string and the conventional pressure detection string, the balanced pressure workover well has the advantages that a blowout preventer is not required to be installed any more, the pipe lifting process is simple, the time consumption is less, and the safety coefficient is high. The invention does not need to add a blocking remover, has high density, can be repeatedly used, does not pollute the environment and stratum and is environment-friendly. Compared with the existing well killing fluid, the balanced well killing and repairing fluid does not need a high-density heterogeneous well killing fluid well killing well, and the high-density homogeneous well killing fluid used in the invention has the advantages of simple preparation process, no solid phase and difficulty in blocking a reservoir stratum. Compared with the pressurized workover, the balanced pressure workover in the invention can carry out the normal pressure workover on the ground under the condition of not plugging the oil pipe and the sleeve, has short construction period, needs a small number of workers and less equipment, and can greatly reduce the workover cost.

Furthermore, in order to prevent the problem that the volume of well killing fluid in a shaft is reduced and the balance in the shaft is broken due to the fact that the well killing fluid is brought out due to the inertia effect in the pipe running process in actual construction, the generated pressure is insufficient, and the well killing is failed, the method is provided with a buffer height of 50-100 meters in an oil pipe, and the problem is well solved.

Drawings

FIG. 1 is a dispensing flow chart;

FIG. 2 is a schematic diagram of reverse circulation injection;

fig. 3 is a schematic diagram of forward implant.

FIG. 4 is a flow chart of the present invention.

In the figure: 1-a well killing fluid storage tank; 2-a recycle line; 3-adding a medicine funnel; 4-cement truck; 5-a flow meter; 6-annulus; 7-an oil pipe; 8-an annulus pressure gauge; 9-oil pipe pressure gauge.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Referring to fig. 1-4, each of the present invention kill fluid formulations comprises: water: 0.485m³～0.597m³110.44-215.53 kg of calcium chloride, 466.02-573.13 kg of sodium nitrate, 142-542.7 kg of zinc bromide and 100-200 kg of HS-3 imidazole quaternary ammonium salt (corrosion inhibitor).

The density adjusting range of the well killing fluid reaches 1.4-1.7 g/cm³And is therefore referred to as high density. Specifically, the raw materials are prepared according to the well repairing operation depth and the well head pressure to meet the requirementA kill fluid of the density described above.

The balanced pressure well repairing method matched with the well repairing device correspondingly comprises the following steps:

step one, calculating the density of the theoretically required well killing fluid according to basic data (well closing pressure and vertical height) of an oil well:

the calculation formula is as follows:

P_downhole＝P_{Shut-in well}+ρ_{Water (W)}×g×H₁ (1)

P_Downhole＝ρ_{Theory of the invention}×g×H₁ (2)

P in the formulae (1) and (2)_{Shut-in well}For shut-in pressure, H₁Is the vertical height, p_{Theory of the invention}Is the theoretically required kill fluid density.

Step two, setting a buffer height, and calculating the actual well killing fluid density:

the calculation formula is as follows:

ρ_{theory of the invention}gH₁＝ρ_{Practice of}g(H₁-h) (3)

In the formula (3), h is a buffer height, and is generally 50-100 m.

Calculating the density rho of the well killing fluid which needs to be prepared actually according to the formula (3)_{Practice of}。

Step three, according to the basic data of the oil well: inner diameter D of casing₁Inner diameter D of oil pipe₂Outer diameter D of oil pipe₃Calculating the required volume of the well killing fluid of each part:

the calculation formula is as follows:

v in formulae (4), (5), (6) and (7)_{Annular space}Is the annular volume, v_{Oil pipe}Is the volume v of the oil pipe_SupplementTo supplement the volume v_ShaftIs the total volume of the wellbore.

Fourthly, according to the calculated density rho of the well killing fluid_{Practice of}And total volume v of the wellbore_ShaftDetermining the amount of various medicines and water required:

calculating the total volume v of the shaft according to the actual volume of the well fluid needing to be matched and pressured as a theory_Shaft1.5 times of the pressure relief fluid, so that the amount of various medicines and water is determined to be needed, and the preparation work before the preparation of the well killing fluid is completed.

The medicine placing sequence is that firstly, sodium nitrate and calcium chloride are respectively and orderly placed on two sides of a medicine adding funnel, and zinc bromide is respectively placed behind the sodium nitrate and the calcium chloride, so that the subsequent adding is convenient.

Step five, all preparation is ready in early work, a circulating pump is started, and a circulating dosing system shown in the figure 1 is established, wherein the circulating dosing system comprises a well killing fluid storage tank 1, a circulating pipeline 2, a dosing hopper 3, a cement truck 4 and a flowmeter 5; wherein, the outlet of the well killing liquid storage tank 1 is connected with the inlet of the circulating pipeline 2, the outlet of the circulating pipeline 2 is connected with the inlet of the box body on the cement truck 4, and the outlet of the box body is connected with the well killing liquid storage tank 1 through the flowmeter 5. A dosing funnel 3 is arranged on the circulating pipeline 2. An annular pressure gauge 8 is arranged on the annular space 6, and an oil pipe pressure gauge 9 is arranged on the oil pipe 7.

Preparing medicine addition:

the dosing sequence is as follows: the sodium nitrate and calcium chloride are first mixed and added, and finally the calcium bromide is added.

When the sodium nitrate and the calcium chloride are added, firstly, according to the mass ratio of the sodium nitrate to the calcium chloride of 2: 1, wherein the adding amount of the added raw materials is not limited after one of the sodium nitrate and the calcium chloride is added.

The water flow in the medicine adding process is controlled to be between 200L/min and 400L/min.

The dosing process needs to record the dosing amount, the pipeline temperature and the corresponding well killing fluid density every 15 minutes, so that the dosing process is accurate.

Step six, circulating the dissolving process:

considering the problems of more dissolved medicines and uncertainty of field temperature, insufficient dissolution and uneven density distribution possibly exist, and after all the medicines are added, the circulating pump is used for circulating to fully dissolve and mix the medicines uniformly.

The cycle time is generally 2 to 5 hours.

Step seven, checking whether the prepared well killing fluid reaches the standard:

after the well killing fluid is fully dissolved and the density is uniformly distributed after circulation, the volume and density of the prepared well killing fluid are detected and recorded. And checking whether the well killing fluid reaches the standard or not.

Step eight, injecting well killing liquid and flushing:

the implantation process may be performed in two ways. The first method is reverse circulation injection, see fig. 2. The second method is to adopt positive extrusion of the annulus and the tubing respectively, i.e. after the annulus is filled, the injection of the well killing fluid from the tubing port is started, see fig. 3.

The well washing is carried out in a reverse circulation well washing mode (namely, the oil pipe 7 is a liquid outlet, and the oil sleeve annulus 6 is a liquid inlet);

the pump truck displacement is kept between 400L/min and 600L/min during well flushing. And finishing the well washing work when the density of the inlet and outlet well washing liquid is kept consistent.

The kill fluid acts as a flushing fluid during the flushing phase.

And step nine, stopping the pump, recording the pressure condition of the well head after observing for 12 hours, and checking whether the well head overflows or not.

If the wellhead overflows, the density is proved to be insufficient, the density of the well killing fluid needs to be increased again by calcium bromide, and the density is increased by 0.2g/cm each time³And injecting again until the wellhead is not flooded.

If the well mouth does not overflow, the back suction proves that the well killing is qualified. The next string-up work can be started.

When the density is adjusted, the oil pipe and the annular space are connected into the circulating dosing system shown in the figure 1, and dosing is carried out at the funnel until the density meets the requirement and no overflow exists at the wellhead.

Step ten, pipe string lifting and string checking processes:

when the string is lifted to check strings, a post is required to be well observed, and the distance between the liquid level and a well mouth is 50-100 meters all the time.

And after the string detection work is finished, injecting displacement water from the annulus to start displacement. The injection flow is controlled between 200L/min and 400L/min. When the volume of displaced kill fluid is monitored to be equal to the volume of injected kill fluid. And when the density of the displacement liquid is equal to that of the injected water, finishing the displacement, stopping the pump and finishing the well repair.

Step eleven, filtering the well killing fluid

The displaced well killing fluid needs to be filtered, and the filtering flow is controlled to be 100-200L/min.

The filtering operation is qualified only by filtering turbid well control fluid with high oil content into transparent, clear and impurity-free well control fluid.

Step twelve, recycling the well killing fluid

The killing fluid injected into the well bore is inevitably diluted to cause density reduction, so that the killing fluid is used as base fluid to be added with medicines to adjust the density according to the relevant data of the next well. So that the density of the oil well meets the requirement of the next well killing operation.

The specific adjustment density calculation process is as follows:

calculating the density of the required well killing fluid according to the related data of the new well and formulas (1), (2) and (3);

② calculating the required base liquid amount and adjusting the density of the base liquid to 1.5g/cm³；

V_{Volume of well killing fluid}＝α×V_{Well bore volume} (9)

Known data are:

D₁: annulus inside diameter, m;

h: vertical height, m;

beta: swelling ratio of well killing fluid (1.5 g/cm)³The well killing fluid is 1.82, 1.6g/cm³1.86% of the kill fluid);

α: the coefficient is generally 1.5 (the volume of the prepared well killing fluid is generally 1.5 times of the theoretical calculated value in consideration of various conditions on site);

ρ: base fluid density, g/cm³；

Data required for experimental measurements:

z: dilution amount, m³(ii) a (1 m)³The density was 1.5g/cm³The volume of clear water used when the well killing fluid is diluted to the density rho of the base fluid is recorded as z);

from the known data and experimentally measured data z, it can be calculated according to equations (8), (9) and (10):

x: amount of base liquid required, m³；

n: theoretical amount of water used for dilution, m³；

Calculating the required medicine amount according to the theoretical water consumption n:

m_{sodium nitrate}＝n·527.47kg

m_{Calcium chloride}＝n·243.96kg

m_{Calcium bromide}＝n·54.95kg

Thirdly, calculating the density of each square of well killing fluid from 1.5g/cm³Adjusted to p_{Practice of}The amount of zinc bromide added is required, see table 1.

TABLE 1 amount of zinc bromide used for density variation

The following are specific examples.

Example 1

The operation purpose is as follows: balanced pressure well workover based on high-density homogeneous well killing fluid

The operation depth is as follows: 2000m

Pressure at the well head: 10MPa

Types of well killing fluids: high-density homogeneous inorganic well killing fluid

Calculating according to a formula: bottom hole pressure 29.6MPa, theoretical kill fluid density rho_{Theory of the invention}1.51g/cm³。

According to rho_{Theory of the invention}gH₁＝ρ_{Practice of}g(H₁-h) calculating p_{Practice of}Where ρ is_{Theory of the invention}＝1.51g/cm³H is 100, and p is calculated_{Practice of}1.58g/cm³。

The volume of the oil pipe is calculated to be 6.41m³Hollow volume of oil jacket ring is 16.89m³The volume of the well killing fluid needs to be supplemented to be 2.48m³Total volume 25.78m³. Considering the loss amount of the killing fluid in the injection process, the total volume of the field prepared killing fluid is 35m³The quality of the required medicine is calculated.

7696kg zinc bromide, 8539kg calcium chloride, 18462kg sodium nitrate and 19m water³200kg of HS-3 imidazoline quaternary ammonium salt and 19m of water³. The entire dosing process amounted to 6 hours. The medicine is circulated for 2 hours by a circulating pump in consideration of the problems of sufficient dissolution and uniform density distribution. The used circulating pump is a self-sucking pump, the specification is MA-75052H, the caliber of an inlet and an outlet is 50mm, the power is 7.5KW, the total flow is 600ml/min, and the total lift is 34 m.

Measuring the volume and density of the in-tank well killing fluid after circulating for two hours, wherein the volume of the in-tank well killing fluid is 35m in total³The density of the well killing fluid in the tank is 1.58g/cm³. The volume and density of the well killing fluid meet the requirements.

Before starting pressure injection, 15 minutes of pressure holding and pressure testing observation period is needed, the 15 minutes of observation period is ended, and the well killing work is started without abnormal conditions.

The first stage is to fill the annulus with the calculated V from the beginning of injection to the completion of the kill fluid_{Annular space}The required kill fluid is injected from the annulus. The initial injection pressure was 20MPa and this stage ensured constant outlet pressure by controlling the outlet throttle. When the amount of the well killing fluid is 15m³Then (c) is performed. The total water removal is measured to be 13.5m³And the first stage injection ends.

Because the water discharged by the oil pipe is discharged after passing through the pressure release valve, the water discharged by the oil pipe and the injected well killing fluid can not correspond in real time.

The second stage increases the injection pressure every five minutes. Controlling the injection of 0.85m every five minutes³The total injection time was about 80 minutes, and a total injection of 13m was measured³13.5m of drainage water³. The tubing pressure will be 0 MPa. Adding 26.5m in total³. And (3) starting circulating well flushing, stopping the pump after well flushing is finished, and observing that the annular pressure (measured by an annular pressure gauge 8 arranged on the annular space) and the oil pipe pressure (measured by an oil pipe pressure gauge 9 arranged on the oil pipe) are both 0 after 12 hours without overflow.

And (4) starting the pipe, wherein the well killing fluid is needed to be supplemented every 20 pipes in the pipe starting process. Each time of replenishing the well killing fluid is 0.3m³. Total 10 times of total 3m³. When the pipe is started, an oil pipe with the depth not less than 1/3 of the well is firstly put into the well, the well mouth is well set, and the well is strictly forbidden to be stopped when the well is empty. And (3) checking scaling and corrosion conditions of the oil outlet pipe and the underground accessories, measuring the oil pipe, checking data, checking the position of the packer, replacing unqualified oil pipes and accessories, and recording. And (5) running a completion string. According to the requirement of a well completion pipe string, a bridge type concentric well completion separate injection drilling tool is arranged, and the structure is as follows: the method comprises the steps of mother plugging, a sieve tube, a double-acting valve, a CQFFO3 type anti-corrosion coating oil tube, a bridge type concentric water distributor, a CQFFO3 type anti-corrosion coating oil tube, a Y341-114 washable well packer, a CQFFO3 type anti-corrosion coating oil tube, a bridge type concentric water distributor, a CQFFO3 type anti-corrosion coating oil tube, a Y341-114 washable well packer and a phi CQFFO3 type anti-corrosion coating oil tube and is used for conveying the oil to a wellhead. And finishing the string checking work.

After the well repairing work is finished, the well killing fluid is displaced by using a movable well washing vehicle to reversely circulate, and the filtered well killing fluid is displaced by 30m³Density of 1.3g/cm³100ml of 1.57g/cm water are added to the laboratory³Diluting to 1.3g/cm³112.5ml of water was used. Conversion to 1m³And Z is 1.125.

Example 2

This embodiment differs from embodiment 1 in that 15m of the annular portion³13m of oil pipe part after completion of injection of well killing fluid³The advantage of this embodiment over embodiment 1 is that the kill fluid is injected from the tubing in a forward direction, the kill fluid is injected from the top down in the tubing, and the kill fluid and the water in the tubing are in a reverse direction. The contact surface of the two is less, the contact time is short, and the dilution effect of water on the well killing fluid can be greatly reduced.

Example 3

The operation purpose is as follows: balanced pressure well workover based on high-density homogeneous well killing fluid

The operation depth is as follows: 2500m

Pressure at the well head: 11.5MPa

Types of well killing fluids: high-density homogeneous inorganic well killing fluid

Based on the calculated bottom hole pressure: 36MPa, kill fluid density rho_{Theory of the invention}：1.48g/cm³Density of kill fluid ρ_{Practice of}：1.54g/cm³The volume of the annulus: 19.78m³And the volume of the oil pipe is as follows: 7.55m³The supplement volume: 3m³. Wellbore volume: 30.5m³。

The volume of the prepared well killing fluid is 40m³Substituting into a formula to calculate the required amount of the base liquid of 28m³. Adjusting the density to 1.5g/cm³7860kg of sodium nitrate needs to be added. 3636kg of calcium chloride and 820kg of zinc bromide, and the density is from 1.5g/cm³Adjusted to 1.54g/cm³. 2184kg of calcium bromide is required. 200kg of HS-3 imidazole quaternary ammonium salt (corrosion inhibitor) is added. Mixing various medicines according to figure 1, and measuring the well killing fluid at 40m after all the medicines are added and the cement truck is used for circulating for two hours³Density of 1.54g/cm³. The volume and density of the well killing fluid meet the requirements.

Before the well killing is started, 15 minutes of pressure holding and pressure testing observation period is needed, the observation period of 15 minutes is ended, and the well killing work is started without abnormal conditions. And in the two injection stages, the volume of the injected well killing fluid, the volume of the water discharged by the oil pipe and the change condition of the wellhead pressure are monitored in real time. The injection amount and the discharge amount are monitored once in ten minutes, and the injection amount is controlled to be 2m every ten minutes³. The whole injection process is about 100 minutes to inject the well killing fluid 20m³. The total water discharge was measured to be 19.5m³. The annular pressure was measured to be 0MPa after injection was complete.

The second stage increases the injection pressure every five minutes. Controlling to inject 1m every five minutes³The total injection pressure was measured at 8m for about 40 minutes of the entire injection process³7.8m of drainage water³. The pressure of the oil pipe is 0MPa, and the total adding amount is 28m³. And (4) starting circulating well washing, stopping the pump, observing that the annular pressure and the oil pipe pressure are both 0 after 12 hours, and avoiding overflow. And (4) starting the pipe, wherein the well killing fluid is needed to be supplemented every 20 pipes in the pipe starting process. Each time of replenishing the well killing fluid is 0.3m³. Total 10 times of total 3m³。

After the well repairing work is finished, the well killing fluid is displaced by using the reverse circulation of the movable well washing vehicle, and the killing fluid is displaced by 33m³Density of 1.29g/cm³Z was 1.095 as measured in the laboratory.

Example 4

This embodiment differs from embodiment 3 in that 20m of the annular portion³8m of oil pipe part after completion of injection of well killing fluid³The control fluid is injected from the oil pipe in the positive direction, and compared with the embodiment 3, the embodiment has the advantages that the control fluid is injected from top to bottom in the oil pipe, the control fluid and the water in the oil pipe are in reverse directions, the contact surface of the control fluid and the water in the oil pipe is less, and the contact time is short, so that the dilution effect of the water on the control fluid can be greatly reduced.

Example 5

The operation purpose is as follows: balanced pressure well workover based on high-density homogeneous well killing fluid

The operation depth is as follows: 1500m

Pressure at the well head: 8MPa

Types of well killing fluids: high-density homogeneous inorganic well killing fluid

Bottom hole pressure is calculated according to the formula: 22.7MPa,. rho_{Theory of the invention}Is 1.54g/cm³，ρ_{Practice of}Is 1.64g/cm³Annular volume 12m³The volume of the oil pipe is 4.6m³Supplement volume 1.8m³. Wellbore volume 18.4m³。

The volume of the prepared well killing fluid is 29m³The required base liquid is 20.3m³Theoretical dilution water amount of 10.7m³20.3m³The density of the base liquid is adjusted to 1.5g/cm³Various medicines are needed. 5643.2kg of sodium nitrate, 2610.4kg of calcium chloride and 588kg of zinc bromide. Then the density is adjusted from 1.5g/cm³Adjusted to 1.64g/cm³. 6668kg of zinc bromide is added. 150kg of HS-3 imidazole quaternary ammonium salt (corrosion inhibitor) is added.

Measuring the well killing fluid 29m by using a circulating pump to circulate for two hours after all the medicines are added³Density of 1.64g/cm³. The volume and density of the well killing fluid meet the requirements.

Before the well killing is started, 15 minutes of pressure holding and pressure testing observation period is needed, the observation period of 15 minutes is ended, and the well killing work is started without abnormal conditions. And in the two injection stages, the volume of the injected well killing fluid, the volume of the water discharged by the oil pipe and the change condition of the wellhead pressure are monitored in real time.

The first stage is ten minutes to monitor the injection amount and the discharge amount, and the injection amount is controlled to be 2m every ten minutes³. The whole injection process is about 60 minutes to inject the well killing fluid 12m³. The total water removal is measured to be 11.8m³. The annular pressure was measured to be 0MPa after injection was complete.

The second stage increases the injection pressure every five minutes. Controlling to inject 1m every five minutes³The total injection pressure was measured at 5m for about 25 minutes³4.8m of drainage water³. The tubing pressure will be 0 MPa. Adding 17m in total³. And (5) starting circulating well washing and stopping the pump, observing that the annular pressure and the oil pipe pressure are both 0 after 12 hours, and avoiding overflow. And (4) starting the pipe, wherein the well killing fluid is needed to be supplemented every 20 pipes in the pipe starting process. Each time of replenishing the well killing fluid is 0.3m³. The whole pipe-taking process is supplemented for seven times, and the total is 2.1m³。

Example 6

This embodiment differs from embodiment 3 in that 12m of the annular portion³5m of oil pipe part after completion of injection of well killing fluid³The kill fluid is injected positively from the tubing. The advantage of this embodiment over embodiment 3 is that the kill fluid is top-down in the tubing and the kill fluid and the water in the tubing are reversed. The contact surface of the two is less, the contact time is short, and the dilution effect of water on the well killing fluid can be greatly reduced.

The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.