CN108343398B - Oil well scale prevention method - Google Patents
Oil well scale prevention method Download PDFInfo
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- CN108343398B CN108343398B CN201711204951.0A CN201711204951A CN108343398B CN 108343398 B CN108343398 B CN 108343398B CN 201711204951 A CN201711204951 A CN 201711204951A CN 108343398 B CN108343398 B CN 108343398B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B37/00—Methods or apparatus for cleaning boreholes or wells
- E21B37/06—Methods or apparatus for cleaning boreholes or wells using chemical means for preventing, limiting or eliminating the deposition of paraffins or like substances
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
Abstract
The invention discloses an oil well scale prevention method, and belongs to the field of oil field exploitation. The method comprises the following steps: injecting a well washing liquid into a sleeve of the target oil well to wash the well; after the well washing is finished, injecting a pad fluid into the near-well stratum of the target oil well through the casing pipe so as to clean an oil-gas channel of the near-well stratum; after the oil gas channel is cleaned, sequentially injecting scale prevention liquid and postposition liquid into the near-well stratum through the casing pipe, and closing the well for a preset time to realize scale prevention of the near-well stratum; opening a well and exploiting the target oil well so as to utilize the produced liquid to carry the antiscaling agent in the antiscaling liquid into the shaft of the target oil well, thereby realizing the antiscaling of the shaft; the anti-scaling liquid comprises water and an anti-scaling agent, and the concentration of the anti-scaling agent in the anti-scaling liquid is 40 kg/square water to 70 kg/square water; the anti-scaling agent comprises the following components in percentage by weight: 20-30% of imidazoline, 40-60% of sodium polyacrylate, 3-5% of kaolinite and the balance of water. The method provided by the invention can effectively prevent the near-well stratum and the shaft of the oil well from scaling.
Description
Technical Field
The invention relates to the field of oilfield exploitation, in particular to an oil well scale prevention method.
Background
In the process of oil field exploitation, due to the change of the physical property and production parameters of crude oil, near-well stratum, mineshafts and well facilities of an oil well are easy to scale, which not only can damage the oil layer and reduce the productivity, but also can increase the maintenance operation frequency of the oil well. Accordingly, there is a need for a method of scale prevention for an oil well to prevent scaling of the near-wellbore formation, the wellbore, and the downhole facilities of the oil well.
The prior art provides a method for preventing scale by dropping, which comprises the following steps: the chemical adding device communicated with the shaft is arranged at the wellhead of the oil well, and the anti-scaling liquid in the chemical adding device enters the shaft in a dropping mode by means of the gravity of the chemical adding device and enters the near-well stratum through the shaft, so that the anti-scaling effect on the near-well stratum, the shaft and the well facility of the oil well can be achieved.
In the process of implementing the invention, the inventor finds that the prior art has at least the following problems:
if the oil well is an inclined well, when the anti-scale liquid falls vertically in the shaft by the self gravity, the anti-scale liquid can be hung on the inclined part of the shaft wall of the shaft in the form of liquid drops, so that a small part of the anti-scale liquid enters the near-well stratum, and the anti-scale liquid cannot play an effective anti-scale effect on the near-well stratum, thereby reducing the production of the oil well.
Disclosure of Invention
The embodiment of the invention provides an oil well scale prevention method, which can solve the problems. The technical scheme is as follows:
a method of scale control of an oil well, the method comprising:
injecting a well washing liquid into a sleeve of the target oil well to wash the well;
after the well washing is finished, injecting a pad fluid into the near-well stratum of the target oil well through the casing pipe so as to clean an oil-gas channel of the near-well stratum;
after the oil gas channel is cleaned, sequentially injecting scale prevention liquid and postposition liquid into the near-well stratum through the casing pipe, and closing the well for a preset time to realize scale prevention of the near-well stratum;
opening a well and exploiting the target oil well so as to utilize produced liquid to carry the antiscaling agent in the antiscaling liquid into a shaft of the target oil well, thereby realizing antiscaling of the shaft;
the post-positioned fluid is used for plugging the anti-scaling agent in the oil and gas channel;
the anti-scaling liquid comprises water and an anti-scaling agent, and the concentration of the anti-scaling agent in the anti-scaling liquid is 40 kg/square water-70 kg/square water;
the anti-scaling agent comprises the following components in percentage by weight: 20-30% of imidazoline, 40-60% of sodium polyacrylate, 3-5% of kaolinite and the balance of water.
In one possible design, 15-18 volumes of the flushing fluid are injected per 1000m well depth.
In one possible design, the displacement to flush the target well is set to 4.5-10 square/hour.
In one possible design, the pad has an injection volume of 1.5 square to 2.5 square.
In one possible design, the pad includes a clay anti-swelling agent, potassium chloride, a demulsifier, and water;
the concentration of the clay anti-swelling agent in the pad fluid is 4.5 kg/square water-5.5 kg/square water, the concentration of the potassium chloride in the pad fluid is 2.5 kg/square water-3.5 kg/square water, and the concentration of the demulsifier in the pad fluid is 11.5 kg/square water-12.5 kg/square water.
In one possible design, the antiscaling agent comprises 19-21 wt% of imidazoline, 40-41 wt% of sodium polyacrylate, 3.0-3.1 wt% of kaolinite, and the balance of water.
In one possible design, the antiscaling agent comprises 29-30% of imidazoline, 49-51% of sodium polyacrylate, 4.9-5.0% of kaolinite and the balance of water in percentage by weight.
In one possible design, the injection volume of the antiscaling liquid is 5-10 square.
In one possible design, the injection volume of the post-liquid is 1.5 square to 2.5 square.
In one possible design, the post-liquid includes: clay anti-swelling agent, potassium chloride, demulsifier, water shutoff agent and water;
the concentration of the clay anti-swelling agent in the postposition liquid is 4.5 kg/square water to 5.5 kg/square water, the concentration of the potassium chloride in the postposition liquid is 3.5 kg/square water to 4.5 kg/square water, the concentration of the demulsifier in the postposition liquid is 7.5 kg/square water to 9.5 kg/square water, and the concentration of the water shutoff agent in the postposition liquid is 4.5 kg/square water to 5.5 kg/square water.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
according to the oil well anti-scaling method provided by the embodiment of the invention, the anti-scaling agent is blocked in the oil gas channel of the near-well stratum, so that the near-well stratum can be prevented from scaling, underground fluid can be carried into the shaft, and further the shaft and well facilities can be prevented from scaling.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail below.
The embodiment of the invention provides an oil well scale prevention method, which comprises the following steps:
step 101, injecting a well washing liquid into a casing of a target oil well, and performing well washing.
And step 102, after well washing is finished, injecting a pad fluid into a near-well stratum of the target oil well through the casing, and cleaning an oil-gas channel of the near-well stratum.
103, after the cleaning of the oil-gas channel is finished, sequentially injecting scale prevention liquid and postposition liquid into the near-well stratum through a sleeve to realize scale prevention of the near-well stratum;
104, opening the well and exploiting the target oil well so as to utilize the produced liquid to carry the antiscaling agent in the antiscaling liquid into the shaft of the target oil well and realize the antiscaling of the shaft; .
Wherein the post-posed liquid is used for plugging the antiscaling agent in the oil-gas channel; the anti-scaling liquid comprises water and an anti-scaling agent, and the concentration of the anti-scaling agent in the anti-scaling liquid is 40 kg/square water to 70 kg/square water; the anti-scaling agent comprises the following components in percentage by weight: 20-30% of imidazoline, 40-60% of sodium polyacrylate, 3-5% of kaolinite and the balance of water.
The following description is directed to the method of preventing scale in a near-wellbore formation, a wellbore, and a downhole facility of a target well.
The antiscaling agent firstly enters the oil gas channel of the near-well stratum in a physical adsorption form or a precipitation forming mode, and then is blocked in the oil gas channel of the near-well stratum by using the postposition liquid. When the target oil well is produced, underground fluid (namely oil well produced liquid) passes through an oil gas channel of the near-well stratum, and the anti-scaling agent blocked in the oil gas channel is slowly released and dissolved in the underground fluid; wherein a portion of the scale inhibitor interacts with the near-well formation to prevent the harmful components of the subterranean fluid from causing the near-well formation to scale, and another portion of the scale inhibitor is carried by the subterranean fluid into the wellbore and interacts with the wellbore and the well facility to prevent the harmful components of the subterranean fluid from causing the wellbore and the well facility to scale. Therefore, the method provided by the embodiment of the invention not only can effectively prevent the scaling of the shaft and the facility in the well, but also can effectively prevent the scaling of the stratum near the well.
Imidazoline in the antiscaling agent can form a firm surface reaction film on the surface of metal and the surface of a near-well stratum, and a corrosive medium is isolated, so that scaling of downhole equipment, a shaft and the near-well stratum can be prevented; the sodium polyacrylate has larger adsorption capacity due to the sodium ions, and the sodium polyacrylate is an acidic solution and can react with carbonate ions to generate water and carbon dioxide, so that the binding probability of scaling ions is reduced, and further scale prevention can be realized; the kaolinite has good compatibility with a near-well stratum, and can improve the adsorption capacity of the antiscaling agent in the near-well stratum. Therefore, the anti-scaling agent used in the embodiment of the invention not only can be firmly adsorbed on the near-well stratum, but also can effectively prevent the near-well stratum, the shaft and the inner arrangement of the well from scaling.
According to the oil well anti-scaling method provided by the embodiment of the invention, the anti-scaling agent is blocked in the oil gas channel of the near-well stratum, so that the near-well stratum can be prevented from scaling, underground fluid can be carried into the shaft, and further the shaft and well facilities can be prevented from scaling.
The following will explain the steps of the method for scale prevention of an oil well according to the embodiment of the present invention:
in step 101, a well-flushing fluid is injected into the casing of the target well to flush the well.
The purpose of this step is to utilize the flushing fluid to remove crude oil and impurity in the pit shaft, carry out the preliminary treatment to the pit shaft of target oil well. The method comprises the following steps of injecting a well washing liquid into a casing of a target oil well, and performing reverse circulation well washing for many times until crude oil and impurities in a shaft are effectively removed.
Wherein, the three factors of the injection amount of the flushing fluid, the flushing time and the type all influence the flushing effect, and the three factors are described one by one as follows:
regarding the injection amount, if the injection amount of the flushing fluid is too small, crude oil and impurities in the shaft cannot be effectively removed; and too much of the water can cause the waste of the well-flushing liquid and increase the anti-scaling cost of the oil well. In order to solve the problem, in the embodiment of the present invention, the injection volume of the flushing fluid is set according to the well depth of the target oil well, specifically, 15-18 (for example, 15, 16, 17, 18, etc.) flushing fluids are injected every 1000m well depth.
Note that 1 st is equal to 1000 liters.
Regarding the well flushing time, in order to effectively remove crude oil and impurities in the well bore and reduce the operation time, in the embodiment of the invention, the well flushing displacement of the target oil well is set to be 4.5 square/hour to 10 square/hour, for example, the well flushing displacement can be set to be 4.5 square/hour, 5.6 square/hour, 6.7 square/hour, 7.8 square/hour, 8.9 square/hour, 10 square/hour, and the like).
As for the kind of the flushing fluid, the flushing fluid for removing crude oil and impurities in the wellbore may be provided in various types, for example, the flushing fluid in the embodiment of the present invention may be provided as a surfactant bio-enzyme solution (for example, the bio-enzyme solution may be provided as BERO produced by excellent oil technology corporation) TM Enzyme) can not only effectively remove crude oil and impurities in the shaft, but also can not cause damage to the shaft if the well washing solution is retained in the shaft due to improper operation. The concentration of the bio-enzyme in the bio-enzyme solution can be set to 0.2L/square water to 0.3L/square water, for example, the concentration can be set to 0.21L/square water, 0.22L/square water, 0.23L/square water, 0.24L/square water, 0.25L/square water, 0.26L/square water, 0.27L/square water, 0.28L/square water, 0.29L/square water, 0.3L/square water, etc.
The concentration of the above-mentioned biological enzyme means the number of liters of the biological enzyme per 1 water.
In step 102, after the well is washed, a pad fluid is injected into the near-well stratum of the target oil well through the casing pipe to clean the oil and gas channel of the near-well stratum.
In the production process of a target oil well, a viscous blockage is usually filled in an oil gas channel of a near-well stratum, the pore diameter of the oil gas channel is reduced by the viscous blockage, and the construction pressure is high due to the small oil gas channel, so that the anti-scaling liquid is not favorably injected into the oil gas channel of the near-well stratum. Therefore, a pad fluid may be injected into the near-well formation to clean the near-well formation of the hydrocarbon channels prior to injecting the scale inhibitor fluid.
In order to effectively remove the viscous blockage in the oil-gas channel and avoid waste of the pad fluid, in the embodiment of the invention, the injection volume of the pad fluid is 1.5-2.5, for example, the injection volume of the pad fluid can be set to be 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, and the like.
The pad fluid which can be used for removing the viscous blockage in the oil and gas channel can be arranged into various types, for example, in the embodiment of the invention, the pad fluid comprises a clay anti-swelling agent, potassium chloride, a demulsifier and water; the concentration of the clay anti-swelling agent in the pad fluid is 4.5 kg/square water to 5.5 kg/square water (for example, 4.5 kg/square water, 4.7 kg/square water, 4.9 kg/square water, 5.1 kg/square water, 5.3 kg/square water, 5.5 kg/square water, etc.) and the concentration of potassium chloride in the pad fluid is 2.5 kg/square water to 3.5 kg/square water (for example, 2.5 kg/square water, 2.7 kg/square water, 2.9 kg/square water, 3.1 kg/square water, 3.3 kg/square water, 3.5 kg/square water, etc.) and the concentration of the demulsifier in the pad fluid is 11.5 kg/square water to 12.5 kg/square water (for example, 11.5 kg/square water, 11.7 kg/square water, 11.9 kg/square water, 12.1 kg/square water, 12.5 kg/square water, etc.).
It is understood that the solute of the pad fluid is clay anti-swelling agent, potassium chloride and demulsifier, and the solvent is water. The clay anti-swelling agent is used for preventing foreign substances from damaging rock and soil minerals of the near-well stratum, protecting the structure of the near-well stratum and avoiding pollution to the near-well stratum, and can be set into small organic cations or potassium chloride; the demulsifier is used for better separating oil from water in the produced liquid and can effectively remove the blockage of the near-well stratum, and the demulsifier can be set into polyethylene oxide or polypropylene oxide.
In addition, in order to effectively clean the oil-gas channel of the near-well stratum, after the pad fluid is injected into the near-well stratum of the target oil well and acts with the viscous blockage in the oil-gas channel for 5-10 min, the cleaning of the oil-gas channel can be considered to be finished.
In step 103, after the oil-gas channel is cleaned, scale prevention liquid and post-positioned liquid are sequentially injected into the near-well stratum through the casing pipe, and the well is closed for a preset time, so that scale prevention of the near-well stratum is achieved.
It should be noted that the antiscaling liquid and the post-fluid in step 103 are sequentially injected into the near-wellbore stratum of the target oil well, and after all the antiscaling liquid is injected into the stratum, the post-fluid should be injected into the near-wellbore stratum immediately.
Based on the above description of the components of the scale inhibitor, it is known that both sodium polyacrylate and kaolinite of the scale inhibitor can improve the adsorption capacity of the scale inhibitor in the oil and gas channels of the near-well stratum.
Wherein the molecular structural formula of the sodium polyacrylate is shown in the specification
N in the molecular structural formula can be 22-32, for example, the value of n can be set to 22, 24, 26, 28, 30, 32, etc. Since the synthesis method of sodium polyacrylate is well known in the art, the synthesis method is not described herein.
It should be noted that kaolinite is a common clay mineral located in underground rocks, and the main components of kaolinite are feldspar and silicate minerals, which have the function of preventing swelling. Thus, the composition of kaolinite is clear to the skilled person.
Regarding the component arrangement of the anti-scaling agent, the embodiment of the invention provides two realization modes:
in a first implementation, the anti-fouling agent comprises the following components in percentage by weight: 19 to 21 percent of imidazoline, 40 to 41 percent of sodium polyacrylate, 3.0 to 3.1 percent of kaolinite and the balance of water.
In a second implementation, the anti-fouling agent comprises the following components in percentage by weight: 29-30% of imidazoline, 49-51% of sodium polyacrylate, 4.9-5.0% of kaolinite and the balance of water.
In order to ensure that the antiscaling agent is adsorbed in the oil and gas channel of the near-well stratum and no antiscaling agent is wasted, in the embodiment of the invention, the injection volume of the antiscaling solution is 5-10, for example, the injection volume can be set to be 5, 6, 7, 8, 9, 10, and the like.
Based on the above description of the principle of the oil well scale prevention method, it can be known that the post-liquid has the function of plugging the scale preventive agent in the oil and gas channel, and the principle can be described as follows: the afterflush provides adhesion to the anti-fouling agent such that the anti-fouling agent is secured to the walls of the oil and gas channel of the near-wellbore formation by the adhesion. The injection volume and the type of the post liquid influence the effect of plugging the anti-scaling agent in the oil and gas channel, and the injection volume and the type of the post liquid are explained one by one.
Regarding the injection volume of the post fluid, in order to effectively block the scale inhibitor in the oil gas channel and not to cause waste of the post fluid, in the embodiment of the present invention, the injection volume of the post fluid is 1.5-2.5, for example, the injection volume of the post fluid may be set to 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, etc.
The postposition liquid which can be used for plugging the scale inhibitor in the oil and gas channel can be arranged into various types, for example, in the embodiment of the invention, the postposition liquid comprises a clay anti-swelling agent, potassium chloride, a demulsifier, a water plugging agent and water; the concentration of the clay anti-swelling agent in the post-fluid is 4.5 kg/square water to 5.5 kg/square water (for example, 4.5 kg/square water, 4.7 kg/square water, 4.9 kg/square water, 5.1 kg/square water, 5.3 kg/square water, 5.5 kg/square water, etc.) and the concentration of potassium chloride in the post-fluid is 3.5 kg/square water to 4.5 kg/square water (for example, 3.5 kg/square water, 3.7 kg/square water, 3.9 kg/square water, 4.1 kg/square water, 4.3 kg/square water, 4.5 kg/square water, etc.), the concentration of the demulsifier in the post-fluid is 7.5 kg/square water to 9.5 kg/square water (for example, 7.5 kg/square water, 8.0 kg/square water, 8.5 kg/square water, 9.0 kg/square water, 9.5 kg/square water, 5 kg/square water, etc.), and the concentration of the water in the post-fluid is 7.5 kg/square water, 4.5 kg/square water, 5 kg/square water (for example, 4.5 kg/square water, 5 kg/square water, etc.).
It can be understood that the solutes of the post-fluid are anti-swelling agent, potassium chloride, demulsifier and water shutoff agent, and the solvent is water. The clay anti-swelling agent is used for preventing foreign substances from damaging rock and soil minerals of the near-well stratum, protecting the structure of the near-well stratum and avoiding pollution to the near-well stratum, and can be set into small organic cations; the demulsifier is used for better separating oil and water in the produced liquid and can effectively remove blockage of the near-well stratum, and the demulsifier can be set into polyethylene oxide or polypropylene oxide; the water shutoff agent is used for plugging an antiscaling agent in an oil-gas channel, and can be polyacrylamide.
In order to improve the effect of plugging the scale inhibitor in the oil and gas channel by the post-fluid and enable the post-fluid and the scale inhibitor to fully act without prolonging the operation time, in the embodiment of the invention, after the post-fluid is injected into a target oil well, the well is closed for 4 to 6 days, for example, the well can be closed for 4, 5, 6 days and the like.
It should be noted that the water used in the flushing fluid, the pad fluid, the antiscale fluid and the post fluid can be taken from the produced water of the stratum (with the temperature of 40-50 ℃), on one hand, the water is close to the temperature of the near-well stratum, and if the temperature difference is large, the stratum can be damaged; on the other hand, the well flushing is convenient, the temperature of the stratum produced water can effectively warm the crude oil, and the performance of the well flushing fluid is improved.
In addition, in the process of injecting the well washing liquid, the pre-positioned liquid, the scale prevention liquid and the post-positioned liquid into the casing, in order to reduce oxidation components and aerobic bacteria carried to a near-well stratum by the externally-applied well washing liquid, a certain amount of deoxidizer can be added into each liquid, and the adding volume of the deoxidizer is 0.1 to 0.3 liter per 1 square of each liquid.
In step 104, a well is opened and the target oil well is produced, so that the produced fluid is used for carrying the antiscaling agent in the antiscaling fluid into a shaft of the target oil well, and the shaft is prevented from being scaled.
The purpose of this step is that the underground fluid carries the anti-scaling agent blocked in the oil gas channel to the shaft, and then can play the effect of anti-scaling to shaft and well facility.
Sampling is carried out in the production process to monitor the concentration of the brought anti-scaling agent, and the service life of the anti-scaling agent is further determined.
All the above optional technical solutions may be combined arbitrarily to form the optional embodiments of the present disclosure, and are not described herein again.
The invention will be further described by means of specific examples.
In the following examples, those whose operations are not subject to the conditions indicated, are carried out according to the conventional conditions or conditions recommended by the manufacturer. The raw materials are all conventional products which can be obtained by market without indicating manufacturers and specifications.
Wherein imidazoline is purchased from Tianjin Xinxiang oil gas technology, inc.; the organic small cation ammonium salt is purchased from Tianjin Xinxiang oil gas technology, inc.; HR-9 type emulsifiers were purchased from Petroleum Tiancheng Industrial group, inc., north China, hebei; phenolic resin cross-linking agents were purchased from Xin Shun chemical Co., ltd; the sodium polyacrylate is prepared and obtained by a laboratory, wherein n in the molecular structural formula of the sodium polyacrylate is 26.
Example 1
The embodiment provides a method for preventing scale of an oil well, which comprises the following steps: and injecting a surfactant bio-enzyme solution with the bio-enzyme concentration of 0.2L/square water into the casing of the target oil well for well washing. Wherein, 16 sides of flushing fluid is injected into each 1000m of well depth, and the well depth of the target oil well is 1500m; the well flushing displacement is 5 square/hour.
And injecting 2-square pad fluid into the near-well stratum of the target oil well through the casing pipe to clean an oil-gas channel of the near-well stratum. Wherein the pad fluid comprises an organic small cation ammonium salt clay anti-swelling agent, potassium chloride, an HR-9 type demulsifier and water; the concentration of the clay anti-swelling agent is 4.5 kg/square water, the concentration of the potassium chloride is 2.5 kg/square water, and the concentration of the demulsifier is 11.5 kg/square water. After 20min, the oil-gas channel is considered to be cleaned.
Injecting 6-square antiscaling liquid into the near-well stratum through a casing, wherein the concentration of an antiscaling agent in the antiscaling liquid is 40 kg/square of water, and the antiscaling agent comprises the following components in percentage by weight: 20% of imidazoline, 40% of sodium polyacrylate, 3% of kaolinite and the balance of water.
Injecting 1.5 square of post-fluid into the near-well stratum through a casing, wherein the post-fluid comprises an organic small cation ammonium salt type clay anti-swelling agent, potassium chloride, an HR-9 type demulsifier, a phenolic resin cross-linking agent and water. The concentration of the clay anti-swelling agent is 4.5 kg/square water, the concentration of potassium chloride is 3.5 kg/square water, the concentration of the demulsifier is 7.5 kg/square water, and the concentration of the water shutoff agent is 4.5 kg/square water.
The well was shut in for 4 days, after which the well was opened and the target well was produced.
Example 2
The embodiment provides a method for preventing scale of an oil well, which comprises the following steps: and injecting a surfactant bio-enzyme solution with the bio-enzyme concentration of 0.3L/square water into the casing of the target oil well for well washing. Wherein, 18 square flushing fluid is injected into each 1000m of well depth, and the well depth of the target oil well is 1200m; the well flushing displacement is 7 square/hour.
And 2.5 square of pad fluid is injected into the near-well stratum of the target oil well through the casing pipe, and an oil-gas channel of the near-well stratum is cleaned. Wherein the pad fluid comprises an organic small cation ammonium salt clay anti-swelling agent, potassium chloride, an HR-9 type demulsifier and water; the concentration of the clay anti-swelling agent is 5 kg/square water, the concentration of the potassium chloride is 3 kg/square water, and the concentration of the demulsifier is 12 kg/square water. After 30min, the oil-gas channel is considered to be cleaned.
Injecting 9-square antiscaling liquid into the near-well stratum through a casing, wherein the concentration of an antiscaling agent in the antiscaling liquid is 60 kg/square of water, and the antiscaling agent comprises the following components in percentage by weight: 30% of imidazoline, 50% of sodium polyacrylate, 5% of kaolinite and the balance of water.
Injecting 2 square postposition liquid into the near-well stratum through a casing, wherein the postposition liquid comprises an organic small cation ammonium salt type clay anti-swelling agent, potassium chloride, an HR-9 type demulsifier, a phenolic resin cross-linking agent and water. The concentration of the clay anti-swelling agent is 5 kg/square water, the concentration of the potassium chloride is 4 kg/square water, the concentration of the demulsifier is 9 kg/square water, and the concentration of the water shutoff agent is 5 kg/square water.
The well was shut in for 6 days, after which the well was opened and the target well was produced.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. A method of scale control for an oil well, the method comprising:
injecting a well washing liquid into a casing of the target oil well, and performing reverse circulation well washing for many times until crude oil and impurities in a shaft are removed;
after the well washing is finished, injecting a pad fluid into the near-well stratum of the target oil well through the casing to clean an oil gas channel of the near-well stratum;
after the oil gas channel is cleaned, sequentially injecting an anti-scaling liquid into the near-well stratum through the casing pipe, wherein an anti-scaling agent in the anti-scaling liquid can enter the oil gas channel of the near-well stratum in a physical adsorption or precipitation forming mode;
after the antiscaling liquid is completely injected into the stratum, injecting a post-positioned liquid into the near-well stratum through the casing pipe, and closing the well for a preset time, wherein the post-positioned liquid is used for providing adhesion for the antiscaling agent so that the antiscaling agent can be fixed on the wall of an oil and gas channel of the near-well stratum, and thus the antiscaling agent is blocked in the oil and gas channel;
opening and producing the target well, wherein when production fluid passes through oil and gas passages of the near-well formation, the anti-scale agent is released and dissolved in the production fluid, so that one part of the anti-scale agent reacts with the near-well formation to realize anti-scale of the near-well formation, and the other part of the anti-scale agent is carried into a wellbore of the target well by the production fluid and reacts with the wellbore and well facilities to realize anti-scale of the wellbore and the well facilities;
sampling and monitoring the brought-out concentration of the anti-scaling agent in the mining process, and further determining the service life of the anti-scaling agent;
the well flushing fluid is a surfactant biological enzyme solution, the concentration of biological enzyme in the biological enzyme solution is 0.2L/square water to 0.3L/square water, and 15-18 square of the well flushing fluid is injected into each 1000m of well depth;
the injection volume of the antiscaling liquid is 5-10 square, the antiscaling liquid comprises water and the antiscaling agent, and the concentration of the antiscaling agent in the antiscaling liquid is 40-70 kg/square water; the anti-scaling agent comprises the following components in percentage by weight: 20-30% of imidazoline, 40-60% of sodium polyacrylate, 3-5% of kaolinite and the balance of water, wherein the imidazoline can form a surface reaction film on a metal surface and the surface of the near-well stratum so as to isolate a corrosive medium;
the injection volume of the pad fluid is 1.5-2.5, and the pad fluid comprises a clay anti-swelling agent, potassium chloride, a demulsifier and water; the concentration of the clay anti-swelling agent in the pad fluid is 4.5 kg/square water to 5.5 kg/square water, the concentration of the potassium chloride in the pad fluid is 2.5 kg/square water to 3.5 kg/square water, and the concentration of the demulsifier in the pad fluid is 11.5 kg/square water to 12.5 kg/square water;
the injection volume of the post liquid is 1.5-2.5, and the post liquid comprises a clay anti-swelling agent, potassium chloride, a demulsifier, a water shutoff agent and water; the concentration of the clay anti-swelling agent in the postposition liquid is 4.5 kg/square water to 5.5 kg/square water, the concentration of the potassium chloride in the postposition liquid is 3.5 kg/square water to 4.5 kg/square water, the concentration of the demulsifier in the postposition liquid is 7.5 kg/square water to 9.5 kg/square water, and the concentration of the water shutoff agent in the postposition liquid is 4.5 kg/square water to 5.5 kg/square water;
wherein the water used in the flushing fluid, the pad fluid, the antiscaling fluid and the post fluid is taken from the produced water of the stratum, and the temperature of the produced water of the stratum is 40-50 ℃;
the flushing fluid, the pad fluid, the scale prevention fluid and the post fluid all comprise a deoxidizer, wherein the adding volume of the deoxidizer is 0.1L/square liquid to 0.3L/square liquid, and the liquid is the flushing fluid, the pad fluid, the scale prevention fluid or the post fluid.
2. The method of claim 1, wherein the target well is flushed at a rate of 4.5-10 square/hour.
3. The method of claim 1, wherein the anti-scalant comprises the following components in weight percent: 19 to 21 percent of imidazoline, 40 to 41 percent of sodium polyacrylate, 3.0 to 3.1 percent of kaolinite and the balance of water.
4. The method of claim 1, wherein the anti-scalant comprises the following components in weight percent: 29-30% of imidazoline, 49-51% of sodium polyacrylate, 4.9-5.0% of kaolinite and the balance of water.
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