Packing gravel for sand prevention of polymer injection benefit well and preparation and construction method thereof

Abstract

The invention discloses a preparation and construction method of filled gravel for sand prevention of a polymer injection benefit well, the filled gravel for sand prevention comprises an internal sand core material and a coating layer wrapping a sand core, the sand core material is quartz sand, and the coating layer comprises resin, an initiator, an accelerant, a filler and a coupling agent. The preparation method comprises the following steps: uniformly mixing a resin solution, an initiator, an accelerant, a filler and the like according to a ratio, respectively carrying out screen analysis on quartz sand of two specifications, heating, putting the heated quartz sand of the same specification into a sugar coating machine, stirring with the uniformly mixed coating solution, and adding a coupling agent according to a required ratio before stirring. And drying and screening after stirring for a certain time. The method has the beneficial effects that the cost is low, the breakage rate is small, polymers are not prone to being adsorbed, and the method can be applied and popularized on a large scale in a polymer injection benefited sand production well, the sand prevention validity period of the polymer injection area sand production well is further prolonged, and the whole life cycle of the oil well is prolonged.

Description

Technical Field

[0001] The invention relates to the field of oil and natural gas exploitation, and in particular to a filling gravel for sand prevention in a polymer injection benefit well and a preparation and construction method thereof. Background Art

[0002] Loose sandstone reservoirs are prone to serious sand production problems during development due to good reservoir permeability and loose rock cementation. At present, gravel packing mechanical sand control technology is a relatively effective means of controlling sand production. The performance indicators of filling gravel directly affect the development effect of oil and water wells. At present, the gravel used for gravel packing sand control is mainly quartz sand, ceramsite and other chemical sand control materials used in special well conditions. Although ceramsite is better than quartz sand in all aspects of performance indicators, quartz sand is cheap, which reduces the development cost in oil and gas well development and has been widely used in gravel packing sand control. For example, Dagang Oilfield consumes about 3,000 tons of quartz sand for sand control every year.

[0003] According to the tracking and analysis of the effects of 203 polymer injection sand control wells at the oil field, the performance indicators of quartz sand gradually show their influence on the sand control effect under certain well conditions. Under high stress, the crushing rate of quartz sand is high. Indoor studies have shown that under 20MPa pressure, the conductivity of the quartz sand filling belt will drop by about one-third compared with that under 14MPa, and under 28MPa, the conductivity will drop by more than half; and the dust in the quartz sand will enter the reservoir with the sand liquid during construction, causing pollution; when quartz sand is used in polymer injection sand wells, the tip of the quartz sand is easy to break and block the pores, and the polymer adsorbs a large amount of mud, fine silt and other substances on its surface to block the filling belt, resulting in a decrease in the liquid production of the sand control well after it is put into production.

[0004] Although ceramsite is better than quartz sand in terms of sphericity and crushing rate, its price is 3 to 4 times that of quartz sand, which cannot meet the requirements of low-cost development of sand-producing reservoirs in injection and polymerizing blocks. Other filling gravel materials rarely have the function of reducing polymer adsorption; for example, CN215804488U provides a multifunctional particle suitable for filling in the formation, which is coated with a heating layer and a suspended filling layer on the outside of the lightweight ceramsite, and is mainly used in the field of natural gas hydrate exploitation, but not suitable for sand control in production wells in injection and polymerizing areas; CN112175599A provides an alkali-resistant coated sand and its preparation method and application, which is coated with epoxy resin and oil-soluble curing agent on the surface of quartz sand or ceramsite, and is only suitable for alkali injection and production wells; CN110423604A provides a sand-proof proppant and its preparation method and application, which forms a resin film on the surface of the supporting aggregate to increase the adhesion between the proppants, and is mostly used in fracturing wells to prevent the proppant from flowing back.

[0005] Therefore, developing a relatively low-cost alternative product with better performance indicators than quartz sand as a gravel filling sand control material in the injection area can further improve the sand control effect. Summary of the invention

[0006] The purpose of the present invention is to provide a filling gravel for sand prevention in polymer injection benefiting wells and its preparation method and construction process, so as to solve the problems that conventional filling gravel for sand production in polymer injection benefiting wells has high crushing rate and easy adsorption of polymer, resulting in serious blockage in the near-well area and serious drop in liquid volume after well opening, so as to achieve long-term control of sand production wells in polymer injection areas of loose sandstone reservoirs.

[0007] In order to solve the above technical problems, the first technical solution adopted by the present invention is: a filling gravel for sand prevention in polymer injection benefit wells, including an internal sand core material and an external coating layer wrapping the sand core, and the coating layer includes resin, initiator, promoter, filler, and coupling agent.

[0008] The mass ratio of the sand core material, the resin, the initiator, the accelerator, the filler and the coupling agent is 100: 1-20: 0.1-1.5: 0.01-0.1: 0.5-1.5: 0.1-2.0.

[0009] The sand core material is quartz sand.

[0010] The quartz sand particle sizes preferably have two types, namely φ0.425mm~φ0.85mm and φ0.6mm~φ1.18mm.

[0011] The resin is unsaturated polyester resin, the initiator is dibenzoyl peroxide, the accelerator is N,N-dimethylaniline, the filler is polyvinyl acetal and glass powder mixed in a ratio of 1: (1-5), and the coupling agent is silane coupling agent KH-570.

[0012] The second technical solution of the present invention is: a method for preparing filling gravel for sand control in a polymer injection benefit well, the steps are as follows:

[0013] Step 1: firstly mix the resin solution, initiator, accelerator and filler in proportion;

[0014] Step 2: Screen the sand core materials with the same particle size and heat them for 1 to 2 hours to 60 to 90° C.

[0015] Step 3: Put the coating solution prepared in proportion and the heated sand core material into the sugar coating machine mixer to mix, add the coupling agent in the required proportion before stirring, and stir for 40 to 60 minutes;

[0016] Step 4: Dry the mixture obtained in step 3 for 2 to 4 hours, and sieve it with an electric vibrating screen to obtain filling gravel.

[0017] The third technical solution of the present invention is: a method for filling gravel for sand prevention in a polymer injection benefit well, comprising the following steps:

[0018] (1) Preparation work before using gravel for sand control in polymer injection benefit wells:

[0019] 1) Perform sand flushing operations on the sand-producing wells in the injection zone to remove the original formation sand in the perforated layer of the wellbore. The sand flushing displacement is 0.4m 3 / min or more, after flushing the sand clean, wash the well for more than 2 weeks;

[0020] 2) A sand control string is run into the sand well of the polymer injection block, which can prevent the filling gravel with a particle size of φ0.425mm to φ0.85mm from entering the screen pipe. The screen pipe is located 4 to 5 meters above the top and bottom of the production oil layer, and the sand control string string is required to be disconnected from top to bottom before gravel filling. Finally, the construction string is run in, and the distance between the bell mouth at the lower end of the construction string and the sand control string in the oil layer section is 50m to 60m;

[0021] (2) Carry out gravel filling operation for sand prevention in the well benefiting from polymer injection:

[0022] 1) Connect the fracturing pump truck, sand mixer and other equipment on the ground, and use the pump truck to pump sand-carrying fluid containing gravel for sand prevention of the polymer injection benefit well into the oil pipe, with a displacement of 1.8 to 2.5 m 3 / min, then pump 30-50m into the oil layer. 3 The gravel pre-fluid for sand prevention of the benefit wells without polymer injection is used to flush the blasthole and remove pollutants in the near-wellbore area;

[0023] 2) Displacement increased by 2.5m 3 / min remains unchanged, the construction pressure is controlled to be less than the formation fracture pressure, the initial sand ratio is set to 5%, first add φ0.425mm~φ0.85mm filling gravel for sand prevention in the benefiting wells of polymer injection, and when there is no obvious change in oil pressure and casing pressure, continue to increase the sand ratio by 5%-8%-12%-16%-20%. The total amount of sand added in this stage is 3-4 times the thickness of the oil layer to establish the first-level sand barrier; then, the particle size of the filling gravel for sand prevention in the benefiting wells of polymer injection is adjusted from φ0.425mm~φ0.85mm to φ0.6mm~φ1.18mm, and the sand ratio is continuously increased by 20%-25%-30%. In the process of increasing the sand ratio, the displacement is increased from 2.5m 3 / min-1.8m 3 / min-1.5m 3 / min is gradually reduced. The amount of sand added in this stage is 1 to 1.5 times the thickness of the oil layer to establish the second-level sand barrier;

[0024] 3) Pump in an appropriate amount of clean water to displace the sand-carrying fluid out of the construction oil pipe, stop the pump, and complete the gravel filling operation for sand prevention in the well benefiting from the polymer injection.

[0025] The beneficial effects of the present invention are as follows: the filling gravel provided by the present invention is suitable for sand-producing oil wells in loose sandstone injection and polymer injection areas. Compared with conventional expanded clay and quartz sand filling gravel, the filling gravel has the advantages of low cost, low breakage rate, and low polymer adsorption. It can be widely promoted and applied in sand-producing wells that benefit from injection and polymer injection, further improving the effective period of sand prevention of sand-producing oil wells in injection and polymer injection areas and extending the entire life cycle of the oil wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of gravel filling for sand control in the well benefiting from polymer injection;

[0027] Figure 2 It is a schematic diagram of the filling operation of filling gravel for sand prevention in the polymer injection benefiting well of the present invention.

[0028] In the figure:

[0029] 1. Sand core material 2. Coating layer 3. Sand control column 4. Screen pipe

[0030] A. Filling zone formed by filling gravel for sand control in the well with fine-grained polymer injection near the wellbore

[0031] B. The filling zone formed by the coarse-grained polymer injection in the screen annulus and the sand control in the well. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0033] The gravel for sand prevention in the polymer injection benefit well of the present invention is as follows: Figure 1 As shown, the filling gravel for sand control in the polymer injection benefit well is composed of a sand core material 1 and a sand core coating layer 2.

[0034] The sand core coating layer 2 is composed of resin, initiator, promoter, filler and coupling agent. The resin is mainly unsaturated polyester resin. Compared with epoxy resin, unsaturated polyester resin has the advantages of relatively low price and can be cured at room temperature, flexible process performance and high safety. After the resin coating is applied on the surface of quartz sand, its mechanical properties can be further improved, the crushing rate can be reduced, and the probability of blockage of the seepage channel of the production oil layer and adsorption by polymer can be reduced. The initiator in the coating layer is benzoyl peroxide (BPO). Benzoyl peroxide can be decomposed under medium and low temperature conditions. The free radicals generated trigger the free radical polymerization reaction of unsaturated polyester resin. The released reaction heat promotes the continuous reaction of polyester resin, and the gel time and curing time of benzoyl peroxide are relatively short. The accelerator in the coating layer is N, N-dimethylaniline, which is mainly a 10% styrene solution, used together with benzoyl peroxide. Its main function is to activate benzoyl peroxide and form free radicals below the critical temperature. The molecular structure of the polyester resin molecular chain contains large molecular branches, which is an effective curing system. Through the joint action of benzoyl peroxide and N, N-dimethylaniline, room temperature curing is achieved. The fillers in the coating layer are preferably polyvinyl acetal of organic polymer compounds and glass powder of inorganic filler. Since the volume shrinkage of polyester resin is very large when it is cured, about 10% to 15%, which is 1 to 4 times higher than that of epoxy resin, it will produce great internal stress, which will reduce the bonding strength and easily crack, affecting the curing performance; polyvinyl acetal has good toughness, fire resistance and moisture resistance, and enhances the adhesion of the coating layer; the glass powder has a small particle size, good dispersibility, high transparency, and has an anti-settling effect; by adding thermoplastic polymer polyvinyl acetal and inorganic filler glass powder to the unsaturated resin solution, the polyester resin solution can be dispersed more evenly, while reducing the shrinkage rate of the polyester resin when it is cured and improving the bonding strength. The coupling agent in the coating layer is KH-570. Since the resin system is an organic material and the quartz sand core is an inorganic material, a coupling agent is required when the polyester resin solution is evenly coated on the surface of the quartz sand. One end of the silane coupling agent is an organic functional group such as vinyl, amino, epoxy, etc., which can react with the resin, and the other end is an inorganic functional group such as chlorine, methoxy, ethoxy, etc., which can form siloxane when combined with inorganic substances; KH-570 silane coupling agent, γ-methacryloxypropyltrimethoxysilane is an organic functional group silane coupling agent that can improve the mechanical properties of thermosetting resins, especially through curing through active free radical reactions, which can effectively improve the bonding properties of organic materials and inorganic materials.

[0035] Embodiment 1:

[0036] The filling gravel for sand prevention of the polymer injection benefit well in this embodiment is mainly composed of a sand core material and a sand core coating layer, and the sand core coating layer is composed of a resin, an initiator, a promoter, a filler and a coupling agent. The resin is an unsaturated polyester resin, the initiator is dibenzoyl peroxide, the promoter is N, N-dimethylaniline, the filler is polyvinyl acetal and glass powder mixed in a ratio of 1:2, and the coupling agent is KH570. The mass ratio of the resin, initiator, promoter, filler and coupling agent in the sand core material coating layer is 100:12:0.3:0.04:0.5:0.8.

[0037] The sand core material is quartz sand, and there are two types of quartz sand particle sizes, namely φ0.425mm~φ0.85mm and φ0.6mm~φ1.18mm.

[0038] First, mix the resin solution, initiator, accelerator, filler, etc. in proportion, then screen and heat the two specifications of quartz sand respectively, the heating time is required to be 1 hour, and the temperature reaches 80°C. Then put the heated quartz sand of the same specification in the sugar coating machine and stir it with the above mixed coating solution, and add the required proportion of coupling agent before stirring. The stirring time is 40 minutes, and after stirring evenly, dry and screen, and the required drying time is 2 hours.

[0039] Gravel filling operation method for sand control in polymer injection benefit wells, such as Figure 2 As shown, the following steps are included:

[0040] (1) Wellbore preparation before filling with gravel for sand prevention in polymer injection benefit wells

[0041] 1) Perform sand flushing operations on the sand-producing wells in the injection zone to remove the original formation sand in the perforated layer of the wellbore. The sand flushing displacement is required to be 0.4m 3 / min or more, after sand flushing, the well washing time is more than 2 weeks;

[0042] 2) A sand control pipe string 3, such as a slotted screen or a wire-wound screen, is lowered into the sand-producing well of the polymer injection block to prevent the filling gravel with a particle size of φ0.425mm to φ0.85mm from entering the screen pipe 4, and the screen pipe has a surplus of 4m at the top and bottom of the production oil layer. Before gravel filling, the sand control pipe string is required to be disconnected from top to bottom; the distance between the bell mouth at the lower end of the construction pipe string and the top of the inserted sand control pipe string is 50m.

[0043] (2) Carry out gravel filling operations for sand prevention in wells benefiting from polymer injection

[0044] 1) Connect the fracturing pump truck, sand mixer and other equipment on the ground, and use the pump truck to pump sand-carrying fluid containing gravel for sand prevention of the polymer injection benefit well into the oil pipe, with a displacement of 1.8 to 2.2 m 3 / min, then pump 30m into the oil layer 3The wells that do not contain polymer injection are filled with gravel pre-fluid for sand control, flushing the blasthole and removing pollutants in the near-wellbore area.

[0045] 2) The displacement remains unchanged, and the initial sand ratio is set to 5%. First, add φ0.425mm~φ0.85mm gravel for sand prevention in the benefiting wells of polymer injection. When there is no obvious change in oil pressure and casing pressure, continue to increase the sand ratio by 5%-8%-12%-16%-20%. The total amount of sand added in this stage is required to be 3-4 times the thickness of the oil layer to establish the first-level sand barrier; then, adjust the particle size of the gravel for sand prevention in the benefiting wells of polymer injection from φ0.425mm~φ0.85mm to φ0.6mm~φ1.18mm, and continue to increase the sand ratio by 20%-25%-30%. In the process of increasing the sand ratio, the displacement is increased from 2.0m 3 / min-1.8m 3 / min-1.5m 3 / min is gradually reduced. In this stage, the amount of sand added is 1 to 1.5 times the thickness of the oil layer to build a second-level sand barrier. Finally, an appropriate amount of clean water is pumped in to displace the sand-carrying liquid out of the construction oil pipe, and the pump is stopped to complete the gravel filling operation for sand prevention in the polymer injection benefiting wells. Figure 2 A in the middle is the filling zone formed by the filling gravel for sand control in the well with fine particle size near the wellbore, and B is the filling zone formed by the filling gravel for sand control in the well with coarse particle size in the screen annulus.

[0046] Embodiment 2:

[0047] The filling gravel for sand prevention of the injection benefit well in this embodiment is mainly composed of a sand core material and a sand core coating layer, and the sand core coating layer is composed of a resin, an initiator, a promoter, a filler and a coupling agent. The resin is an unsaturated polyester resin, the initiator is dibenzoyl peroxide, the promoter is N, N-dimethylaniline, the filler is polyvinyl acetal and glass powder mixed in a ratio of 1:5, and the coupling agent is KH570. The mass ratio of the resin, initiator, promoter, filler and coupling agent in the sand core material coating layer is 100:15:0.2:0.06:0.7:1.0.

[0048] The sand core material is quartz sand, and there are two types of quartz sand particle sizes, namely φ0.425mm~φ0.85mm and φ0.6mm~φ1.18mm.

[0049] First, mix the resin solution, initiator, accelerator, filler, etc. in proportion, then screen and heat the two specifications of quartz sand respectively, the required heating time is 1.8 hours, and the temperature reaches 90°C. Then put the heated quartz sand of the same specification in the sugar coating machine and stir it with the above mixed coating solution, and add the required proportion of coupling agent before stirring. The stirring time is 60 minutes, and after stirring evenly, dry and screen, and the drying time is 3.5 hours.

[0050] The method for filling gravel for sand prevention in a polymer injection benefit well comprises the following steps:

[0051] (1) Wellbore preparation before filling with gravel for sand prevention in polymer injection benefit wells

[0052] 1) Perform sand flushing operations on the sand-producing wells in the injection zone to remove the original formation sand in the perforated layer of the wellbore. The sand flushing displacement is required to be 0.4m 3 / min or more, after sand flushing, the well washing time is more than 2 weeks;

[0053] 2) A sand control pipe string, such as a slotted screen or a wire-wound screen, is placed in the sand-producing well of the polymer injection block to prevent the filling gravel with a particle size of φ0.425mm to φ0.85mm from entering the screen pipe, and the screen pipe has a surplus of 5m at the top and bottom of the production oil layer. Before gravel filling, the sand control pipe string is required to be disconnected from top to bottom; the distance between the bell mouth at the lower end of the construction pipe string and the top of the inserted sand control pipe string is 60m.

[0054] (2) Carry out gravel filling operations for sand prevention in wells benefiting from polymer injection

[0055] 1) Connect the fracturing pump truck, sand mixer and other equipment on the ground, and use the pump truck to pump sand-carrying fluid containing gravel for sand prevention of the polymer injection benefit well into the oil pipe, with a displacement of 2.0-2.5m 3 / min, then pump 50m into the oil layer 3 The wells that do not contain polymer injection are filled with gravel pre-fluid for sand control, flushing the blasthole and removing pollutants in the near-wellbore area.

[0056] 2) The displacement remains unchanged, and the initial sand ratio is set to 8%. First, add φ0.425mm~φ0.85mm gravel for sand prevention in the benefiting wells of polymer injection. When there is no obvious change in oil pressure and casing pressure, continue to increase the sand ratio by 8%-15%-20%-25%. The total amount of sand added in this stage is required to be 4-5 times the thickness of the oil layer to establish the first-level sand barrier; then, adjust the particle size of the gravel for sand prevention in the benefiting wells of polymer injection from φ0.425mm~φ0.85mm to φ0.6mm~φ1.18mm, and continue to increase the sand ratio by 25%-30%-40%. In the process of increasing the sand ratio, the displacement is increased from 2.5m 3 / min-2.0m 3 / min-1.5m 3 / min-1.2m 3 / min is gradually reduced. In this stage, the amount of sand added is 1.5-2.0 times the thickness of the oil layer to build a second-level sand barrier. Finally, an appropriate amount of clean water is pumped in to displace the sand-carrying liquid out of the construction oil pipe, and the pump is stopped to complete the gravel filling operation for sand prevention in the polymer injection benefiting wells.

[0057] The filling gravel for sand control of polymer injection benefiting wells provided in Example 1 of the present invention was used in the GX-2 well in the GX polymer injection sand producing block of Dagang Oilfield. The well had previously used conventional quartz sand for mechanical sand control, with a daily liquid production of 10.1 cubic meters and a daily oil production of 1.2 tons. The polymer concentration detected at the wellhead was 4 ppm and the dynamic liquid level was 680 m. After sand control operations were carried out, after the well was opened, the daily liquid production was 22.3 cubic meters and the daily oil production was 2.5 tons. The polymer concentration at the wellhead was 12 ppm and the dynamic liquid level was 220 m. The efficient production period has exceeded 26 months.

[0058] The filling gravel for sand control of polymer injection benefiting wells provided in Example 2 of the present invention was used in the SX-3 well in the GX polymer injection sand producing block of Shengli Oilfield. The well had previously used conventional quartz sand for mechanical sand control, with a daily liquid production of 13.4 cubic meters and a daily oil production of 2.2 tons. The polymer concentration detected at the wellhead was 16 ppm and the dynamic liquid level was 768 m. After sand control operations were carried out, after the well was opened, the daily liquid production was 30.2 cubic meters and the daily oil production was 4.8 tons. The polymer concentration at the wellhead was 42 ppm and the dynamic liquid level was 340 m. The efficient production period has exceeded 18 months.

[0059] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The content of this specification should not be understood as limiting the present invention.

Claims

1. A filling gravel for sand prevention in a polymer injection benefit well, characterized by: It comprises an internal sand core material (1) and an external coating layer (2) wrapping the sand core, wherein the coating layer comprises resin, initiator, accelerator, filler and coupling agent.

2. The gravel filling for sand control in polymer injection benefit wells according to claim 1 is characterized in that: The mass ratio of the sand core material, the resin, the initiator, the accelerator, the filler and the coupling agent is 100: 1-20: 0.1-1.5: 0.01-0.1: 0.5-1.5: 0.1-2.

0.

3. The gravel filling for sand control in polymer injection benefit wells according to claim 1 is characterized by: The sand core material is quartz sand.

4. The gravel filling for sand control in a polymer injection benefit well according to claim 3 is characterized by: The quartz sand particle sizes preferably have two types, namely φ0.425mm~φ0.85mm and φ0.6mm~φ1.18mm.

5. The gravel filling for sand control in polymer injection benefit wells according to claim 1 is characterized by: The resin is unsaturated polyester resin, the initiator is dibenzoyl peroxide, the accelerator is N,N-dimethylaniline, the filler is polyvinyl acetal and glass powder mixed in a ratio of 1: (1-5), and the coupling agent is silane coupling agent KH-570.

6. A method for preparing gravel for sand control in polymer injection benefit wells according to claim 1, characterized in that the steps are: as follows: Step 1: firstly mix the resin solution, initiator, accelerator and filler in proportion; Step 2: Screen the sand core materials with the same particle size and heat them for 1 to 2 hours to 60 to 90° C. Step 3: Put the coating solution prepared in proportion and the heated sand core material into the sugar coating machine mixer to mix, add the coupling agent in the required proportion before stirring, and stir for 40-60 minutes; Step 4: Dry the mixture obtained in step 3 for 2 to 4 hours, and sieve it with an electric vibrating screen to obtain filling gravel.

7. A method for filling gravel for sand prevention in a polymer injection benefit well according to claim 1, characterized in that: The steps include: (1) Preparation work before using gravel for sand control in polymer injection benefit wells: 1) Perform sand flushing operations on the sand-producing wells in the injection zone to remove the original formation sand in the perforated layer of the wellbore. The sand flushing displacement is 0.4m 3 / min or more, after flushing the sand clean, wash the well for more than 2 weeks; 2) A sand control string is run into the sand well of the polymer injection block, which can prevent the filling gravel with a particle size of φ0.425mm to φ0.85mm from entering the screen pipe. The screen pipe is located 4 to 5 meters above the top and bottom of the production oil layer, and the sand control string string is required to be disconnected from top to bottom before gravel filling. Finally, the construction string is run in, and the distance between the bell mouth at the lower end of the construction string and the sand control string in the oil layer section is 50m to 60m; (2) Carry out gravel filling operation for sand prevention in the well benefiting from polymer injection: 1) Connect the fracturing pump truck, sand mixer and other equipment on the ground, and use the pump truck to pump sand-carrying fluid containing gravel for sand prevention of the polymer injection benefit well into the oil pipe, with a displacement of 1.8 to 2.5 m 3 / min, then pump 30-50m into the oil layer. 3 The gravel pre-fluid for sand prevention of the benefit wells without polymer injection is used to flush the blasthole and remove pollutants in the near-wellbore area; 2) Displacement increased by 2.5m 3 / min remains unchanged, the construction pressure is controlled to be less than the formation fracture pressure, the initial sand ratio is set to 5%, first add φ0.425mm~φ0.85mm filling gravel for sand prevention in the benefiting wells of polymer injection, and when there is no obvious change in oil pressure and casing pressure, continue to increase the sand ratio, 5%-8%-12%-16%-20%, the total amount of sand added in this stage is 3-4 times the thickness of the oil layer, and the first-level sand barrier is established; then, the particle size of the filling gravel for sand prevention in the benefiting wells of polymer injection is adjusted from φ0.425mm~φ0.85mm to φ0.6mm~φ1.18mm, and the sand ratio is continuously increased by 20%-25%-30%. In the process of increasing the sand ratio, the displacement is increased from 2.5m 3 / min-1.8m 3 / min-1.5m 3 / min is gradually reduced. The amount of sand added in this stage is 1 to 1.5 times the thickness of the oil layer to establish the second-level sand barrier; 3) Pump in an appropriate amount of clean water to displace the sand-carrying fluid out of the construction oil pipe, stop the pump, and complete the gravel filling operation for sand prevention in the well benefiting from the polymer injection.

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