A method for unblocking a wellbore and near wellbore zone in a gas well

Abstract

The present application relates to a kind of gas well wellbore and near wellbore zone's deplugging method, the deplugging method includes: wellbore deplugging and / or near wellbore zone deplugging;The wellbore deplugging includes sequentially carried out first atomization deplugging, first liquid phase deplugging, first soak and first emptying back flow;The wellbore deplugging is carried out at least once, the terminal point of operation is that the solid content of the back flow fluid obtained by first emptying back flow is ≤10mg / L;The near wellbore zone deplugging includes sequentially carried out second liquid phase deplugging, second soak, second emptying back flow, second atomization deplugging, third soak and third emptying back flow;The near wellbore zone deplugging is carried out at least once, the terminal point of operation is that the solid content of the back flow fluid obtained by third emptying back flow is ≤30mg / L.The deplugging method provided by the present application can adjust the overall acidizing profile of gas reservoir, increase the acid swept volume, and at the same time, can enter the far wellbore zone of gas reservoir, communicate the discontinuous pores and fractures, and realize the deep deplugging of gas reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas production technology, specifically to a method for unblocking the wellbore and near-wellbore zone in a gas well. Background Technology

[0002] Currently, during the gas well development process, gas wells containing H2S, CO2, and high-mineralization formation water experience severe corrosion and scaling in some well tubing due to the combined effects of the well fluid, corrosive media in natural gas and formation water, tubing corrosion products, formation water crystal products, and heavy components in corrosion inhibitors. This leads to organic or inorganic blockages near the wellbore, preventing normal production. During production, this manifests as a sharp or rapid drop in output, increased oil-casing pressure differential, and slow formation pressure recovery, causing the gas well to remain in a low-yield and inefficient production state for extended periods until it is forced to shut down, severely impacting the single-well productivity.

[0003] Currently, acidizing is a common chemical method used to unblock wellbores and near-wellbore areas. Liquid acid is injected into the wellbore at a pressure lower than that of the formation using a pump truck to dissolve and clean the scale in the wellbore. Then, nitrogen or natural gas lift is used to return the injected acid and the cleaned scale to the surface combustion tank.

[0004] After removing the scale inside the wellbore, a pump truck is used to inject liquid formation unblocking agent into the near-wellbore zone at a pressure higher than the formation pressure but lower than the formation fracture pressure. Nitrogen or natural gas is then injected to replace the liquid formation unblocking agent completely into the formation for near-wellbore unblocking.

[0005] For example, CN111502599A discloses an acid-dissolving method for unblocking oil and gas wells, relating to the field of oil and gas drilling and production technology. This method addresses the technical problem of difficulty in determining the amount of acid used for unblocking oil and gas wells. The method includes: identifying the blockage point closest to the gas outlet of the working pipe, denoted as the blockage metering point; calculating the amount of unblocking acid used based on the metering point, denoted as V; purging the working pipe under controlled pressure; injecting V volume of the unblocking acid into the working pipe, immersing the adhering material in the acid; closing the working pipe and allowing the unblocking solution to react with the adhering material for a preset time; and backflushing the unblocked solution. This acid-dissolving method can determine the optimal amount of unblocking acid used to acidify the adhering material, preventing situations of excessive unblocking acid or incomplete reaction of the adhering material.

[0006] CN113462372A discloses a deblocking acid solution for removing blockages in high-temperature, high-pressure gas wells. Based on its mass, the deblocking acid solution comprises the following components: 5-10 wt% hydrochloric acid, 0-2.0 wt% hydrofluoric acid, 1-3 wt% clay stabilizer, 3.0-6.0 wt% corrosion inhibitor, 1-3 wt% drainage aid, 1-3 wt% iron ion stabilizer, 5-20 wt% waterproofing agent, 1-3 wt% demulsifier, and the balance being water. This deblocking acid solution can effectively remove blockages in high-temperature, high-pressure wells with minimal corrosion to the wellbore and tubing and minimal damage to the formation.

[0007] However, during the unblocking operations in the wellbore and near-wellbore area of ​​the aforementioned gas wells, the liquid unblocking agent flows downwards along the wellbore too quickly, reaching the bottom of the well rapidly. Very little unblocking agent remains in the upper tubing. Furthermore, because the unblocking agent does not flow downwards along the entire tubing, some sections of the tubing do not come into contact with it, resulting in insufficient unblocking of the scale in the upper tubing. During the near-wellbore unblocking process, the liquid formation unblocking agent tends to finger along high-permeability channels, causing heterogeneous propagation and failing to connect discontinuous pores. This limits the volume of liquid formation unblocking agent that can reach the wellbore, thus failing to achieve the desired unblocking effect. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for unblocking the wellbore and near-wellbore zone in gas wells, so as to solve the problems of excessively fast downward flow of liquid unblocking agent along the wellbore, insufficient contact between the wellbore and the unblocking agent resulting in too small residual unblocking agent dosage in the upper tubing or partial tubing not contacting the unblocking agent, which leads to unsatisfactory unblocking, as well as the problem of the liquid formation unblocking agent fingering along high-permeability channels, which limits the volume of liquid formation unblocking agent that can be affected.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for unblocking the wellbore and near-wellbore zone in a gas well, the unblocking method comprising: unblocking the wellbore and / or unblocking the near-wellbore zone;

[0011] The wellbore unblocking includes sequentially performing a first atomization unblocking, a first liquid phase unblocking, a first well shut-in, and a first venting and backflow; the wellbore unblocking is performed at least once, and the endpoint of the operation is that the solid content of the backflow fluid obtained from the first venting and backflow is ≤10mg / L;

[0012] The near-wellbore unblocking includes sequentially performing a second liquid phase unblocking, a second well shut-in, a second venting and backflow, a second atomization unblocking, a third well shut-in, and a third venting and backflow; the near-wellbore unblocking is performed at least once, and the endpoint of the operation is that the solid content of the backflow fluid obtained from the third venting and backflow is ≤30mg / L.

[0013] The unblocking method provided by this invention involves filling the entire wellbore with atomized unblocking agent during the wellbore unblocking stage, thus unblocking the entire wellbore. The liquid unblocking agent is used for immersion unblocking of severely scaled lower sections of the wellbore. Simultaneously, during the near-wellbore unblocking process, a liquid formation unblocking agent is first used to remove severely blocked sections near the wellbore, followed by atomized acid for deeper unblocking. Compared to liquid acid, atomized acid can penetrate into the upper and lower permeability areas, adjusting the overall acidification profile of the gas reservoir and increasing the acid sweep volume. It can also penetrate into the far-wellbore zone of the gas reservoir, connecting discontinuous pores and achieving deep unblocking of the gas reservoir. This method is simple and suitable for widespread application in gas wellbore and near-wellbore unblocking operations.

[0014] In this invention, when both wellbore unblocking and near-wellbore zone unblocking are performed, wellbore unblocking is performed first, followed by near-wellbore zone unblocking.

[0015] In this invention, during multiple wellbore unblocking operations, the solid content of the return fluid obtained from the first venting and return is detected each time. When the solid content is ≤10mg / L, subsequent operations are carried out. The specific solid content can be 10mg / L, 9mg / L, 8mg / L, 7mg / L, 6mg / L, or 5mg / L, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] In this invention, during multiple near-wellbore unblocking operations, the solid content of the return fluid obtained from the third venting and return is measured each time. When the solid content is ≤30mg / L, subsequent operations are carried out. The specific solid content can be 30mg / L, 25mg / L, 20mg / L, 15mg / L, 10mg / L, or 5mg / L, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] In this invention, after the liquid unblocking agent and the atomized unblocking agent are injected into the near-wellbore zone, a gaseous medium is required to push the agent into the near-wellbore zone.

[0018] In this invention, the end point of wellbore unblocking operation also requires controlling the oil-casing pressure difference to be less than 2 MPa.

[0019] As a preferred technical solution of the present invention, the first atomization unblocking method involves atomizing the liquid wellbore unblocking agent with a gaseous medium and then injecting it into the wellbore for treatment.

[0020] Preferably, the injection rate of the gas medium used in the first atomization unblocking process is 1000-1200 dm. 3 / h, for example, could be 1000dm 3 / h、1010dm 3 / h、1020dm 3 / h、1030dm 3 / h、1040dm 3 / h, 1050dm3 / h、1060dm 3 / h、1070dm 3 / h、1080dm 3 / h、1090dm 3 / h、1100dm 3 / h、1110dm 3 / h、1120dm 3 / h、1130dm 3 / h、1140dm 3 / h、1150dm 3 / h、1160dm 3 / h、1170dm 3 / h、1180dm 3 / h、1190dm 3 / h or 1200dm 3 / h, etc., but not limited to the listed values, other unlisted values ​​within this range also apply.

[0021] Preferably, the volume ratio of the gaseous medium to the liquid wellbore unblocking agent used in the first atomization unblocking process is (2000-2400):1, for example, it can be 2000:1, 2105:1, 2310:1, 2315:1, 2320:1, 2325:1, 2330:1, 2335:1, 2340:1, 2345:1, 2350:1, 2355:1, 2360:1, 2365:1, 2370:1, 2375:1, 2380:1, 2385:1, 2390:1, 2395:1 or 2400:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] In this invention, the injection volume of the first atomized liquid wellbore unblocking agent is based on the calculation that the atomized unblocking agent fills the entire wellbore after being converted according to the wellbore pressure. The specific calculation process is as follows:

[0023]

[0024] In the formula: V 注入量 —Atomized gas injection volume (nitrogen or natural gas) under standard ground conditions, in m³ 3 V 井筒 —Wellbore volume, m 3 ;T 标准 —Temperature under standard ground conditions, K; P 井筒 —Average pressure inside the wellbore, MPa; Z 井筒 —Gas deviation coefficient under average wellbore pressure and average temperature conditions; T 井筒 —Average temperature inside the wellbore, K; P 标准—Pressure under standard ground conditions, MPa.

[0025] As a preferred technical solution of the present invention, the first liquid phase unblocking is to inject a liquid wellbore unblocking agent into the wellbore for treatment.

[0026] As a preferred embodiment of the present invention, the injection volume of the liquid unblocking agent in the first liquid-phase unblocking process is ≤ the volume of 100m of wellbore height. That is, the injection volume of the liquid unblocking agent should ensure that the liquid level is ≤ 100m. Specifically, if wellbore unblocking is performed at least twice, the injection volume of the liquid unblocking agent in the first instance should be 80-100m, and the pumping speed should be < 0.01m / s². 3 / min. Starting from the second injection, the injection volume of liquid unblocking agent must also ensure that the liquid level is ≤60m. The specific liquid level height can be 100m, 95m, 90m, 85m, 80m, 75m, 70m, 65m, 60m, 55m, 50m, 45m, 40m, 35m, or 30m, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] In this invention, the simmering time of the first well is based on the time required for the wellbore unblocking agent to react with the wellbore scale. It can be selected according to the wellbore unblocking agent used. For example, if a mass concentration of 15% HCl + 1.5% corrosion inhibitor + 1.0% gel breaker + 1.0% iron ion stabilizer + 8% neutral unblocking agent is used, the simmering time after injecting the wellbore unblocking agent is 16 hours.

[0028] As a preferred technical solution of the present invention, the second liquid phase unblocking involves injecting a liquid formation unblocking agent into the near-wellbore zone for treatment.

[0029] As a preferred embodiment of the present invention, the injection volume of the liquid formation unblocking agent in the second liquid-phase unblocking process is 2.0 m reservoir radius pore volume. The specific process is as follows:

[0030]

[0031] Where: V—injection volume of unblocking agent in the near-wellbore zone, m 3 R—Injection radius, m; h 层1 —Thickness of layer 1, m; h 层2 —Layer 2 thickness, m; φ 层1 —Porosity of layer 1; φ 层2 —Layer 2 porosity.

[0032] Preferably, the injection rate of the liquid formation unblocking agent in the second liquid-phase unblocking process is 0.3-0.5 m. 3 / min, for example, could be 0.3m 3 / min, 0.31m 3 / min, 0.32m3 / min, 0.33m 3 / min, 0.34m 3 / min, 0.35m 3 / min, 0.36m 3 / min, 0.37m 3 / min, 0.38m 3 / min, 0.39m 3 / min, 0.4m 3 / min, 0.41m 3 / min, 0.42m 3 / min, 0.43m 3 / min, 0.44m 3 / min, 0.45m 3 / min, 0.46m 3 / min, 0.47m 3 / min, 0.48m 3 / min, 0.49m 3 / min or 0.5m 3 / min, etc., but not limited to the listed values, other unlisted values ​​within this range also apply.

[0033] In this invention, the simmering time for the second well is determined by the reaction time required between the formation unblocking agent and the formation scale. The unblocking agent used can be selected accordingly. For example, if the mass concentration is 20% HCl + 0.5% corrosion inhibitor + 1.0% gel breaker + 1.0% iron ion stabilizer + 8% neutral unblocking agent + 0.5% fluorine surfactant + 1.0% fluid loss reducer, the simmering time after injecting the unblocking agent in the near-wellbore zone is 24 hours.

[0034] As a preferred technical solution of the present invention, the second atomization unblocking process involves using a gaseous medium to atomize the liquid formation unblocking agent and inject it into the near-wellbore area for treatment.

[0035] As a preferred embodiment of the present invention, the injection rate of the gas medium used in the second atomization unblocking process is 1000-1200 dm. 3 / h, for example, could be 1000dm 3 / h、1010dm 3 / h、1020dm 3 / h、1030dm 3 / h、1040dm 3 / h, 1050dm 3 / h、1060dm 3 / h、1070dm 3 / h、1080dm 3 / h、1090dm3 / h、1100dm 3 / h、1110dm 3 / h、1120dm 3 / h、1130dm 3 / h、1140dm 3 / h、1150dm 3 / h、1160dm 3 / h、1170dm 3 / h、1180dm 3 / h、1190dm 3 / h or 1200dm 3 / h, etc., but not limited to the listed values, other unlisted values ​​within this range also apply.

[0036] Preferably, the volume ratio of the gaseous medium to the liquid formation unblocking agent used in the second atomization unblocking process is (1000-1200):1, for example, it can be 1000:1, 1010:1, 1020:1, 1030:1, 1040:1, 1050:1, 1060:1, 1070:1, 1080:1, 1090:1, 1100:1, 1110:1, 1120:1, 1130:1, 1140:1, 1150:1, 1160:1, 1170:1, 1180:1, 1190:1 or 1200:1, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0037] Preferably, the injection volume of the liquid formation unblocking agent after atomization in the second atomization unblocking process is the reservoir pore volume with a formation radius of 2m to 5m calculated based on the formation pressure. The specific calculation process is as follows:

[0038]

[0039] In the formula: V 注入量 —Atomized gas injection volume (nitrogen or natural gas) under standard ground conditions, in m³ 3 ;T 标准 —Temperature under standard ground conditions, K; P 地层 —Near-wellbore average formation pressure, MPa; Z 地层 —Gas deviation coefficient under near-wellbore mean formation pressure and mean formation temperature conditions; T 地层 —Number of formation temperatures near the wellbore, K; P 标准 —Pressure under standard ground conditions, MPa; R1—5m injection radius, m; R2—2m injection radius, m; h 层1 —Thickness of layer 1, m; h 层2 —Layer 2 thickness, m; φ 层1 —Porosity of layer 1; φ层2 —Layer 2 porosity.

[0040] In this invention, the simmering time for the third well is determined by the reaction time required between the formation unblocking agent and the formation scale. The unblocking agent used can be selected accordingly. For example, if the mass concentration is 20% HCl + 0.5% corrosion inhibitor + 1.0% gel breaker + 1.0% iron ion stabilizer + 8% neutral unblocking agent + 0.5% fluorine surfactant + 1.0% fluid loss reducer, the simmering time after injecting the unblocking agent near the wellbore is 24 hours.

[0041] As a preferred technical solution of the present invention, the gaseous medium used in the unblocking method includes nitrogen and / or natural gas.

[0042] As a preferred technical solution of the present invention, the unblocking method includes: wellbore unblocking and / or near-wellbore zone unblocking;

[0043] The wellbore unblocking process includes sequential steps of first atomization unblocking, first liquid phase unblocking, first well shut-off, and first venting and flowback. The wellbore unblocking is performed at least once, with the endpoint being a solid content of ≤10 mg / L in the flowback fluid obtained from the first venting and flowback. The first atomization unblocking involves atomizing the liquid wellbore unblocking agent using a gaseous medium and injecting it into the wellbore for treatment. The injection rate of the gaseous medium used in the first atomization unblocking is 1000-1200 dm³. 3 / h; The volume ratio of the gaseous medium and the liquid wellbore unblocking agent used in the first atomization unblocking is (2000-2400):1; The first liquid phase unblocking involves injecting the liquid wellbore unblocking agent into the wellbore for treatment; The injection volume of the liquid wellbore unblocking agent in the first liquid phase unblocking is ≤ the volume of the wellbore height 100m;

[0044] The near-wellbore unblocking process includes, sequentially, a second liquid-phase unblocking, a second well shut-in, a second venting and flowback, a second atomization unblocking, a third well shut-in, and a third venting and flowback. The near-wellbore unblocking is performed at least once, with the endpoint being a solid content of ≤30 mg / L in the flowback fluid obtained from the third venting and flowback. The second liquid-phase unblocking involves injecting a liquid formation unblocking agent into the near-wellbore area. The injection volume of the liquid formation unblocking agent in the second liquid-phase unblocking is equal to the pore volume of a reservoir radius of 2.0 m. The injection rate of the liquid formation unblocking agent in the second liquid-phase unblocking is 0.3-0.5 m / s². 3 / min; In the second atomization unblocking process, the liquid formation unblocking agent is atomized using a gaseous medium and injected into the near-wellbore area for treatment; The injection rate of the gaseous medium used in the second atomization unblocking process is 1000-1200 dm / min. 3 / h; The volume ratio of the gaseous medium and the liquid formation unblocking agent used in the second atomization unblocking is (1000-1200):1; The injection volume of the liquid formation unblocking agent after atomization in the second atomization unblocking is the reservoir pore volume with a formation radius of 2m to 5m calculated based on the formation pressure;

[0045] The gaseous medium used in the unblocking method includes nitrogen and / or natural gas.

[0046] In this invention, during the backflow process, if the oil pressure drops rapidly to 0 during venting and drainage, and the flame is small and no liquid is discharged, the process is immediately switched to air-lift drainage. When the oil jacket pressure is basically balanced and no more water is discharged, the venting and backflow stage is considered to be over.

[0047] In this invention, the selection of the types of wellbore unblocking agents and formation unblocking agents only needs to ensure that they are effective; the specific types will not affect the unblocking effect brought about by the unblocking process of this invention. The wellbore unblocking agents and formation unblocking agents used can refer to existing unblocking agents in the prior art. Specifically, they can be prepared by referring to the formulas disclosed in existing technologies, or commercially available unblocking agents that can be atomized can be used.

[0048] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0049] The unblocking method provided by this invention introduces an atomized unblocking fluid treatment process at a specific stage. Compared with liquid acid, atomized acid can penetrate into the upper and lower permeability areas, adjusting the overall acidification profile of the gas reservoir and increasing the acid sweep volume. At the same time, it can enter the far-well zone of the gas reservoir, connecting discontinuous pores and achieving deep unblocking of the gas reservoir. This avoids the problem of limited sweep volume of liquid formation unblocking agents caused by fingering along high-permeability channels when using only liquid unblocking agents. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the unblocking method provided in an embodiment of the present invention;

[0051] Figure 2 This is the gas production curve before and after unblocking of the CJ26-6 gas well in Embodiment 1 of the present invention.

[0052] In the figure, section A is the gas production curve of the gas well one month before unblocking; section B is the gas production curve of the gas well during the unblocking period. Due to the frequent opening and closing of gas wells during the unblocking period, the gas production data is not included in the statistics; section C is the gas production curve of the gas well three months after unblocking.

[0053] a-Casing pressure curve, b-Oil pressure curve, c-Daily gas production curve, d-Daily water production curve.

[0054] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0055] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0056] This invention provides a method for unblocking the wellbore and near-wellbore zone in a gas well, such as... Figure 1 As shown, the process includes injecting atomized unblocking agent after draining the wellbore, followed by injecting liquid unblocking agent for treatment, then simmering the well and backflowing, repeating the cycle until the backflowing fluid becomes clear and transparent, at which point the wellbore unblocking is complete, and the unblocking of the near-wellbore zone begins.

[0057] In the unblocking process near the wellbore, liquid unblocking agent is first injected and pushed into the near-wellbore area through a gas medium. Then, the well is shut down and vented back. Next, atomized unblocking agent is added for unblocking (pushed into the near-wellbore area through a gas medium). The process of shutting down and venting back is repeated. The state of the vented back is checked each time. When the vented back is clear and transparent, the unblocking of the near-wellbore area is completed.

[0058] The specific implementation process is as follows:

[0059] Example 1

[0060] This embodiment describes a method for unblocking an actual gas well, as detailed below:

[0061] The CJ26-6 well in the CJ gas field has a normal production oil-casing pressure differential of around 1.5 MPa and a daily gas production of 2.5 × 10⁻⁶ MPa. 4 m 3 The output gas contains approximately 3.670% CO2 and 409.38 mg / m³ of H₂S per day. 3 From commissioning to unblocking, a total of 5400L of corrosion inhibitor was added. The total salinity of the produced water was 14785mg / L, the chloride content was 9718mg / L, and the water type was CaCl2. As production time increased, the oil-casing pressure difference increased to approximately 5.3MPa, and the daily gas production decreased to 0.35×10⁻⁶. 4 m 3 The well was repeatedly blocked at around / d. After analysis, the main reason for the decline in gas well production was considered to be:

[0062] ① Scaling in wellbore is caused by organic deposits, formation water crystal products, etc., which are heavy components of corrosion inhibitors;

[0063] ②CO2 forms CO3 in water 2- Ions and Ca in formation water 2+The formation of CaCO3 scale deposits and the expansion and migration of reservoir clay minerals upon contact with water cause blockage in the near-wellbore area.

[0064] According to the unblocking method of the present invention

[0065] The wellbore unblocking agent (15% HCl + 1.5% corrosion inhibitor (disodium hydroxyethylidene diphosphate) + 1.0% gel breaker (potassium persulfate) + 1.0% iron ion stabilizer (tetrasodium ethylenediaminetetraacetate) + 8% neutral unblocking agent (EDTA as complexing agent, carboxyethyl galactomannan as solubilizer, pancreatic acid bleaching agent as penetrant, and acrylate-methyl acrylate copolymer as dispersant) is used, along with a near-wellbore unblocking agent (20% HCl + 0.5% corrosion inhibitor (disodium hydroxyethylidene diphosphate)). The wellbore unblocking operation was carried out using a mixture of disodium diphosphate, 1.0% breaker (potassium persulfate), 1.0% iron ion stabilizer (tetrasodium ethylenediaminetetraacetate), 8% neutral unblocking agent (EDTA as complexing agent, carboxyethyl galactomannan as solubilizer, pancreatic bleach as penetrant, and acrylate-methyl acrylate copolymer as dispersant), 0.5% fluorinated surfactant (perfluoroalkyl acid), and 1.0% fluid loss reducer (hydroxymethyl cellulose). A total of 8m³ of unblocking agent was injected during the wellbore unblocking stage. 3 The wellbore unblocking process is carried out in 10 rounds, with 0.3m of liquid unblocking agent added in each round. 3 0.5m of atomized anti-blocking agent 3 After the well is drained back, the next round of injection is carried out.

[0066] During the near-wellbore unblocking phase, a total of 23m³ of formation unblocking agent was injected. 3 8m of liquid formation unblocking agent 3 15m of atomized formation unblocking agent 3 They were respectively sealed in wells and returned to the source.

[0067] The gas well production dynamics after unblocking were observed for three months following the test. Figure 2 As shown, the wellhead casing pressure differential decreased from 5.3 MPa to 1.43 MPa, and the production rate decreased from 0.35 × 10⁻⁶ MPa. 4 m 3 / d increased to 2.62×10 4 m 3 / d, returning to normal production levels, indicates that the wellbore and near-wellbore area have successfully undergone atomization to dissolve the blockage.

[0068] Example 2

[0069] This embodiment serves as a comparative example to Example 1. The gas well production conditions in this embodiment are largely the same as those in Example 1, and conventional chemical unblocking methods are employed, as detailed below:

[0070] The CJ26-9 well in the CJ gas field has a normal production oil-casing pressure differential of around 1.4 MPa and a daily gas production of 2.5 × 10⁻⁶ MPa.4 m 3 The output gas contains approximately 3.662% CO2 and 400.31 mg / m³ of H₂S per day. 3 From commissioning to unblocking, a total of 4900L of corrosion inhibitor was added. The total mineralization of the produced water was 14231mg / L, the chloride content was 9610mg / L, and the water type was CaCl2. As production time increased, the oil-casing pressure difference increased to about 5MPa, and the daily gas production decreased to 0.33×10⁻⁶. 4 m 3 The well was repeatedly blocked at around / d. After analysis, the main reason for the decline in gas well production was considered to be:

[0071] ① Formation water crystal products and other substances cause scale buildup in the wellbore;

[0072] ②CO2 forms CO3 in water 2- Ions and Ca in formation water 2+ The formation of CaCO3 scale deposits and the expansion and migration of reservoir clay minerals upon contact with water cause blockage in the near-wellbore area.

[0073] This well employed the liquid wellbore unblocking agent and near-wellbore zone unblocking agent described in Example 1 for unblocking operations. A total of 8m³ of liquid wellbore unblocking agent was injected during the wellbore unblocking stage. 3 The wellbore unblocking process is carried out in 10 rounds, with 0.8m of liquid wellbore unblocking agent added in each round. 3 After the well is drained back, the next round of injection is carried out.

[0074] During the near-wellbore unblocking phase, a total of 23m³ of formation unblocking agent was injected. 3 All unblocking agents were liquid, and each was used for well shut-off and flowback. After the experiment, the production dynamics of the gas well were monitored for three months after unblocking. The wellhead-casing pressure differential decreased from 5 MPa to 2.9 MPa, and the production increased from 0.33 × 10⁻⁶ MPa. 4 m 3 / d increased to 0.76×10 4 m 3 / d, conventional unblocking achieved some success, but compared with Example 1, the oil-casing pressure difference was still large, proving that the wellbore unblocking was not thorough. The daily gas production and pressure recovery level after the measures were still significantly different from Example 1, proving that the unblocking in the near-wellbore area was not thorough.

[0075] The results from the above embodiments show that the unblocking method provided by the present invention, in the wellbore unblocking stage, uses atomized unblocking agent to fill the entire wellbore and unblock the entire wellbore. The liquid unblocking agent is used for immersion unblocking of the low-lying parts of the wellbore with severe scaling. At the same time, in the near-wellbore unblocking process, liquid formation unblocking agent is first used to remove the severely blocked parts near the wellbore, and then atomized acid is used for deep unblocking. Compared with liquid acid, atomized acid can enter the upper part and the lower permeability part, can adjust the overall acidification profile of the gas reservoir, increase the acid sweep volume, and can enter the far-wellbore area of ​​the gas reservoir to connect discontinuous pores and achieve deep unblocking of the gas reservoir. The method is simple and suitable for widespread application in gas wellbore and near-wellbore unblocking operations.

[0076] The present invention is described in detail through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0077] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0078] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0079] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for unclogging the wellbore and near-wellbore zone in a gas well, characterized in that, The unblocking methods include: wellbore unblocking and near-wellbore zone unblocking; The wellbore unblocking includes sequentially performing a first atomization unblocking, a first liquid phase unblocking, a first well shut-in, and a first venting and backflow; the wellbore unblocking is performed at least once, and the endpoint of the operation is that the solid content of the backflow fluid obtained from the first venting and backflow is ≤10mg / L; The first atomization unblocking method involves atomizing the liquid wellbore unblocking agent into the wellbore using a gaseous medium and then injecting it into the wellbore for treatment. The near-wellbore unblocking includes sequentially performing a second liquid phase unblocking, a second well shut-in, a second venting and backflow, a second atomization unblocking, a third well shut-in, and a third venting and backflow; the near-wellbore unblocking is performed at least once, and the endpoint of the operation is that the solid content of the backflow fluid obtained from the third venting and backflow is ≤30mg / L; The second atomization unblocking process involves using a gaseous medium to atomize the liquid formation unblocking agent and inject it into the near-wellbore area for treatment.

2. The unblocking method as described in claim 1, characterized in that, The injection rate of the gas medium used in the first atomization unblocking process is 1000-1200 dm. 3 / h.

3. The unblocking method as described in claim 1, characterized in that, The volume ratio of the gaseous medium to the liquid wellbore unblocking agent used in the first atomization unblocking process is (2000-2400):

1.

4. The unblocking method as described in claim 1, characterized in that, The first liquid phase unblocking involves injecting a liquid wellbore unblocking agent into the wellbore for treatment.

5. The unblocking method as described in claim 1, characterized in that, The second liquid-phase unblocking involves injecting a liquid formation unblocking agent into the near-wellbore area for treatment.

6. The unblocking method as described in claim 1, characterized in that, In the second liquid phase unblocking process, the injection volume of the liquid formation unblocking agent is 2.0 m of reservoir radius pore volume.

7. The unblocking method as described in claim 1, characterized in that, In the second liquid-phase unblocking process, the injection rate of the liquid formation unblocking agent is 0.3-0.5 m. 3 / min.

8. The unblocking method as described in claim 1, characterized in that, The injection rate of the gas medium used in the second atomization unblocking process is 1000-1200 dm. 3 / h.

9. The unblocking method as described in claim 1, characterized in that, The volume ratio of the gaseous medium to the liquid formation unblocking agent used in the second atomization unblocking process is (1000-1200):

1.

10. The unblocking method as described in claim 1, characterized in that, The injection volume of the liquid formation unblocking agent after atomization in the second atomization unblocking process is the reservoir pore volume with a formation radius of 2m to 5m calculated based on the formation pressure.

11. The unblocking method as described in claim 1, characterized in that, The gaseous medium used in the unblocking method includes nitrogen and / or natural gas.

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