A plug-type chemical water plugging process for fracturing main fractures of a perforation completion horizontal well in a water flooding oilfield

Abstract

The present application relates to a kind of plugging water drive oilfield perforation completion horizontal well fracturing main fracture plug type chemical water shutoff process.Mainly solve the problem that existing water shutoff control water mode cannot plug perforation completion fracturing horizontal well water breakthrough fracture.It includes the following steps:1) preferably chemical water shutoff target horizontal well;Lower into construction pipe column;2) determine to inject three plugs and the chemical plugging agent dosage of each plug;3) sequentially inject first plug, second plug, third plug chemical plugging agent;4) inject polyacrylamide polymer solution to displace, until chemical plugging agent is extrapolated to 5-10 meters outside perforation gun;5) shut-in waiting for 48-72 hours;6) verify process effectiveness;7) lift construction pipe column, lower into production pipe column and normally produce.The chemical water shutoff process can effectively plug the high water cut fracturing main fracture of horizontal well, while protecting the oil flow channel established by fracturing branch crack, increase the flow distance of injected water, expand water drive sweep range.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oilfield exploration and development, in particular to a slug type chemical water plugging process for plugging the perforation completion and horizontal well fracturing main fracture of a water drive oilfield. BACKGROUND

[0002] With the development of water injection in low-permeability oilfield horizontal wells, the water drive front communicates with the fracturing fractures, forming a water flow dominant channel, which makes the injected water mainly flow into the horizontal wellbore along the dominant channel and be produced, resulting in early water breakthrough in the horizontal well and high water cut soon, reducing the water drive sweep range, and making the remaining oil in the fracture sides, low water cut fracture sections and other water injection directions in the well area unable to be effectively produced, which seriously affects the water drive development effect. In order to improve the development effect, the reservoir engineering often uses water injection adjustment to control water and increase oil, and the effect is good in the early stage of water injection adjustment. After the horizontal well sees water in multiple sections and multiple directions, the effect of multiple rounds of water injection adjustment gradually deteriorates. The mechanical water plugging is often used in oil production engineering to control water, but the mechanical water plugging technology has limitations and can only plug water from the wellbore. Water flow can easily channel to other fracture sections along the casing outside, resulting in rapid high water cut in the horizontal well again. In recent years, chemical water plugging technology is used to control water, but the chemical plugging agent with low strength cannot plug the water breakthrough fracture, and the chemical plugging agent with high strength can easily plug the oil flow channel, plugging water and oil at the same time, failing to achieve the purpose of controlling water and increasing oil. In addition, the plugging agent is left in the wellbore and welded to the wellbore, causing the construction pipe string to be unable to be safely pulled out, resulting in overhaul and seriously affecting the production effect. SUMMARY

[0003] The present application overcomes the problem in the background art that the existing water plugging and control method cannot plug the water breakthrough fracture of the perforation completion and horizontal well fracturing, and provides a slug type chemical water plugging process for plugging the perforation completion and horizontal well fracturing main fracture of a water drive oilfield. The slug type chemical water plugging process for plugging the perforation completion and horizontal well fracturing main fracture of a water drive oilfield is suitable for the perforation completion and horizontal well fracturing of a low-permeability water drive oilfield with a water breakthrough fracture section, which can effectively plug the high water cut fracturing main fracture of the horizontal well, protect the oil flow channel established by the fracturing branch fractures, increase the flow distance of the injected water, and expand the water drive sweep range.

[0004] The present application solves the problem by the following technical scheme: the slug type chemical water plugging process for plugging the perforation completion and horizontal well fracturing main fracture of a water drive oilfield, comprising the following steps:

[0005] (1) selecting a chemical water plugging target horizontal well;

[0006] (2) running a construction pipe string;

[0007] (3) determining that the injected chemical plugging agent slug section number is three, which are a first slug, a second slug and a third slug; and determining the chemical plugging agent dosage of the three slugs;

[0008] (4) injecting the first, second and third segment chemical plugging agents in sequence;

[0009] (5) injecting polyacrylamide polymer solution to displace the chemical plugging agents until the chemical plugging agents are extruded to 5-10 meters outside the perforation gun;

[0010] (6) shutting down the well and waiting for 48-72 hours;

[0011] (7) verifying the effectiveness of the process; if the process is effective, the next step of construction can be performed; if the process is ineffective, it indicates that the fractures are not plugged, and the second and third segments are re-injected according to the above step (4);

[0012] (8) pulling out the construction string and lowering the production string for normal production.

[0013] Preferably, the chemical plugging agent of the three segments is used in an amount of 4-12 parts by volume for the first segment, 32-90 parts by volume for the second segment, and 2-8 parts by volume for the third segment; the amount of the chemical plugging agent is the sum of the theoretical amount and the filtration loss amount;

[0014] and / or,

[0015] The method for injecting the first, second and third segment chemical plugging agents is: the first segment is injected in sequence, the second segment is injected when the injection pressure is 16-20 MPa and the pressure rise rate slows down, and the third segment chemical plugging agent is injected when the injection pressure is stable and maintained at 22-25 MPa.

[0016] Preferably, the first segment is a suspendable self-softening particle for temporary plugging of branch fractures; the suspendable self-softening particle comprises self-softening particles and a suspending agent.

[0017] and / or,

[0018] The mass concentration of the self-softening particles and the suspending agent is: 10%-30% of the self-softening particles and 70%-90% of the suspending agent.

[0019] Preferably, the self-softening particles are resin-based plugging agents, the self-softening particles are larger than the matrix pore throat radius of the target layer and smaller than 1 / 3 of the main fracture pore throat radius, so that the particles can enter the fractures but not the matrix of the target layer, plugging the fractures while not blocking the matrix oil flow channels; the self-softening particles have a softening point that is 5-10°C lower than the temperature of the target layer, so that the particles deform and plug the micro-fractures and secondary fractures after entering the target layer, enhancing the plugging effect.

[0020] and / or,

[0021] The suspension agent is a weak gel with viscosity of 100-200 mPa.s, which is used to suspend particles, and after the suspension agent carrying the softened particles into the formation, the suspension agent breaks, the particles soften and deform under the temperature condition of the formation, and block the micro cracks and secondary cracks, and are mutually soluble with oil, so that the oil flow can pass through, and are not mutually soluble with water, so as to prevent the water phase from passing through, and play a role of protecting the oil flow channel.

[0022] Preferably, the resin plugging agent is any one of chlorovinyl resin, phenolic resin, and oil-soluble resin modified by rosin;

[0023] and / or,

[0024] The weak gel is a phenolic resin gel or a chromium gel.

[0025] Preferably, the second plug is an organic gel, which is used to block the main cracks.

[0026] and / or,

[0027] The initial viscosity of the organic gel is less than 200 mPa.s, which is easy to flow in the wellbore, so as to ensure the smooth pumping during construction; the gel strength is greater than 50000 mPa.s, which can block the cracks and prevent the water flow from breaking through; and the gelation time is between 30-72 hours, which ensures that the gel does not solidify during the injection process, and the well can be produced within 72 hours after the injection.

[0028] Preferably, the organic gel is prepared by mixing and curing 0.1%-0.5% zwitterionic polyacrylamide, 0.2%-0.5% m-dihydroxybenzene, and 0.02%-0.05% oxalic acid at the temperature of the target layer.

[0029] Preferably, the third plug is a high-strength organic gel, which plays a role of sealing to prevent the aforementioned plug from returning.

[0030] The third plug is prepared by mixing and curing 0.5%-0.7% zwitterionic polyacrylamide and 0.25%-0.6% m-dihydroxybenzene at the temperature of the target layer.

[0031] Preferably, the initial viscosity of the high-strength organic gel is greater than 250 mPa.s, which can flow in the wellbore, so as to ensure the smooth pumping during construction, and at the same time, the aforementioned plug is uniformly pushed to the formation; the gel strength is greater than 140000 mPa.s, which ensures that the aforementioned plug does not return; and the gelation time is between 5-20 hours, which ensures that the gel does not solidify during the injection process, and the plug does not return.

[0032] Preferably, the selection principle of the chemical water plugging target horizontal well is that the daily liquid production is greater than or equal to 2 tons, the water cut is greater than or equal to 80%, the water breakthrough crack section is clear, the chemical water plugging target layer section has qualified cementing quality, and there is no casing deformation and casing damage.

[0033] Compared with the above background art, the present application can have the following beneficial effects:

[0034] The plug-type chemical water plugging process for fracturing main fractures of perforation completion horizontal wells in water drive oilfields of the present application is suitable for plugging the fracturing fractures of perforation completion horizontal wells in water drive oilfields. The first plug solves the problem of blocking the oil flow channel, the second plug ensures the plugging strength of the plugged fractures, and the third plug solves the problem of backflow of the plugging agent. The injection of polyacrylamide polymer solution over displacement can prevent the plugging agent from welding the wellbore and improve the safety and reliability of the running and pulling of the work string. By injecting different properties of plugging agents through the plug, the high water cut fracturing main fractures of the horizontal well are effectively plugged, the oil flow channel established by the fracturing branch fractures is protected, effective displacement between the oil and water wells can still be established after chemical water plugging, the water drive sweep range is expanded, the remaining oil on both sides of the water breakthrough fracture, the low water cut fracture section and other water injection directions in the well area of the horizontal well is tapped, and the water drive recovery efficiency is improved. At the same time, the plugging agent can prevent the wellbore from being welded, and the safety and reliability of the running and pulling of the work string are improved. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application embodiments will be further described in detail below.

[0036] The present application effectively plugs the high water cut fracturing main fractures of the horizontal well by injecting different properties of plugging agents through the plug, protects the oil flow channel established by the fracturing branch fractures, enables effective displacement between the oil and water wells after chemical water plugging, expands the water drive sweep range, taps the remaining oil on both sides of the water breakthrough fracture, the low water cut fracture section and other water injection directions in the well area of the horizontal well, and improves the water drive recovery efficiency. At the same time, the plugging agent can prevent the wellbore from being welded, and the safety and reliability of the running and pulling of the work string are improved.

[0037] The injected plugging agent of the present application is divided into three plugs:

[0038] (1) The first plug is a suspendable self-softening particle for temporarily plugging the branch cracks. The suspendable self-softening particle comprises 10% to 30% self-softening particles and the rest is a suspending agent. The self-softening particle refers to one of chlorovinyl resin, phenolic resin and rosin modified oil-soluble resin. The particle radius is required to be greater than the matrix pore throat radius of the target layer and less than 1 / 3 of the main crack pore throat radius, so that the particle can enter the cracks but not the target layer matrix, plugging the cracks while not blocking the oil flow passage of the matrix; the particle softening point is required to be 5-10℃ lower than the temperature of the target layer, so that the particle softens and deforms after entering the target layer, plugging the micro cracks and secondary cracks and enhancing the plugging effect. The suspending agent is a phenolic resin gel or a chromium gel with a viscosity of 100-200 mPa.s, which is used to suspend the particles. After the suspending agent carrying the self-softening particles enters the formation, the suspending agent breaks, the particles soften and deform under the temperature condition of the formation, plugging the micro cracks and secondary cracks, and the particles are mutually soluble with oil, so that the oil flow can pass through, and the particles are not mutually soluble with water, preventing the water from passing through, thus protecting the oil flow passage.

[0039] (2) The second plug is an organic gel for plugging the main cracks. The organic gel is prepared by mixing and curing 0.1%-0.5% zwitterionic polyacrylamide, 0.2%-0.5% m-dihydroxybenzene and 0.02%-0.05% oxalic acid at the temperature of the target layer. The initial viscosity of the organic gel is required to be less than 200 mPa.s, so that the organic gel can flow easily in the wellbore, ensuring the smooth pumping during the construction; the gel strength is required to be greater than 50000 mPa.s, so that the organic gel can plug the cracks and the water flow cannot break through; the gelation time is required to be between 30 and 72 hours, so that the organic gel does not solidify during the injection and the well can be produced within 72 hours after the injection.

[0040] (3) The third plug is a high-strength organic gel for sealing and preventing the previous plugs from backflowing. The high-strength organic gel is prepared by mixing and curing 0.5%-0.7% zwitterionic polyacrylamide and 0.25%-0.6% m-dihydroxybenzene at the temperature of the target layer. The initial viscosity of the high-strength organic gel is required to be greater than 250 mPa.s, so that the high-strength organic gel can flow in the wellbore, ensuring the smooth pumping during the construction and uniformly pushing the previous plugs to the formation; the gel strength is required to be greater than 140000 mPa.s, so that the high-strength organic gel can prevent the previous plugs from backflowing; the gelation time is required to be between 5 and 20 hours, so that the high-strength organic gel does not solidify during the injection and the high-strength organic gel does not backflow.

[0041] The implementation steps of the present application are as follows:

[0042] (1) Preferably, the chemical water plugging target horizontal well is selected. The well selection principle is that the daily liquid production is greater than or equal to 2 tons, the water cut is greater than or equal to 80%, the water breakthrough crack segment is clear, the chemical water plugging target layer segment is cemented with qualified quality, and there is no casing deformation and casing damage.

[0043] (2) The construction pipe string is lowered;

[0044] (3) calculating the amount of chemical plugging agent; the amount of chemical plugging agent is calculated by volume, including 4-12 parts of the first slug, 32-90 parts of the second slug and 2-8 parts of the third slug; the total amount of chemical plugging agent is the sum of the theoretical amount and the filtration loss.

[0045] The theoretical amount is calculated by the following formula:

[0046] Q=2LEh

[0047] In the formula: Q-theoretical amount, m 3 ;

[0048] L-plugging radius, m;

[0049] E-fracture width, m;

[0050] h-fracture height, m.

[0051] The filtration loss is calculated by the following formula:

[0052]

[0053] In the formula: V-filtration loss, m 3 ;

[0054] C I -filtration coefficient;

[0055] L-plugging radius, m;

[0056] t, τ-injection time, h;

[0057]

[0058] In the formula: C I -filtration coefficient;

[0059] μ f -liquid viscosity in the fracture, mPa·s;

[0060] ΔP-pressure difference inside and outside the fracture, MPa;

[0061] k-permeability of the vertical fracture wall, μm2;

[0062] φ-porosity of the formation, decimal.

[0063] (4) injecting the first slug in sequence, when the injection pressure is 16-20 MPa and the pressure rise rate slows down, injecting the second slug, until the injection pressure is stable and maintained at 22 MPa-25 MPa, injecting the third slug of chemical plugging agent.

[0064] (5) injecting polyacrylamide polymer solution to displace, and extrapolating the chemical plugging agent to 5-10 meters outside the perforation hole.

[0065] (6) Wait for 48-72 hours for condensation after closing the well;

[0066] (7) Inject clean water to verify the effectiveness of the process. If no injection volume of clean water is observed, it indicates that the fracture has been plugged and the process is effective, and the next step can be performed; if injection volume of clean water is observed, it indicates that the fracture has not been plugged, and the second and third packers are re-injected according to the above step (4).

[0067] (8) Lift the working string and lower the production string for normal production.

[0068] The method is suitable for plugging the fractured cracks of the perforation completion horizontal well in the water flooding oilfield. The first packer solves the problem of blocking the oil flow channel, the second packer ensures the plugging strength of the plugged fracture, and the third packer solves the problem of backflow of the plugging agent. The injection of the polyacrylamide polymer solution can prevent the plugging agent from welding the wellbore and improve the safety and reliability of the working string.

[0069] Example 1

[0070] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the following detailed description of the technical solution is provided below, but it should not be understood as limiting the scope of the present application.

[0071] Well NP297 is a perforation completion and fracturing horizontal well in AN oilfield, which is fractured in 4 sections. Through the injection adjustment of surrounding water wells, it is clear that the water breakthrough in the fourth section of the well is the cause of high water cut. The cementing quality of the upper and lower layers of the fourth section of the well is excellent, and the daily liquid production before chemical water plugging is 3.8 tons, the water cut is 99.9%, and there is no casing deformation and casing damage, which meets the requirements of chemical water plugging well selection. Therefore, well NP297 is selected as the target horizontal well for chemical water plugging, and the fourth section of the fractured crack is chemically plugged.

[0072] The field construction is carried out according to the industry standard, the original pump string is lifted, the working string is lowered, and the target layer is accurately sealed.

[0073] The dosage of the chemical plugging agent is the sum of the theoretical dosage and the filtration loss, and the theoretical dosage is calculated according to the following formula:

[0074] Q = 2LEh

[0075] In the formula: Q - theoretical dosage, m 3 ;

[0076] L - plugging radius, m;

[0077] E - fracture width, m;

[0078] h - fracture height, m.

[0079] The numerical simulation determines that the plugging radius of the well is 220 m; referring to the fracturing construction guide book of well NP297, the fracture width of the fourth section is 0.0053 m, and the fracture height is 16.5 m; the theoretical dosage is calculated to be 39 m 3 .

[0080] The fluid loss is calculated by the following formula:

[0081]

[0082] In the formula, V is the fluid loss, m 3 ;

[0083] C I is the fluid loss coefficient;

[0084] L is the plugging radius, m;

[0085] t and τ are the injection time, h;

[0086]

[0087] In the formula, C I is the fluid loss coefficient;

[0088] μ f is the viscosity of the liquid in the fracture, MPa·s;

[0089] ΔP is the pressure difference between the inside and outside of the fracture, MPa;

[0090] k is the permeability of the vertical fracture wall, μm 2 ;

[0091] φ is the porosity of the formation, decimal.

[0092] Referring to the performance of the second plug chemical plugging agent, the viscosity of the liquid in the fracture is 200 MPa·s, the pressure difference between the inside and outside of the fracture is 10 MPa, the permeability of the vertical fracture wall is 0.01332 μm 2 , the porosity of the formation is 0.175, and the injection time is 5 h; the theoretical dosage is calculated to be 36 m 3 . The dosage of the chemical plugging agent is finally determined to be 75 m 3 . The volume ratio of the three plugs is 2:8:1, so that the dosage of the first plug is 7 m 3 , the dosage of the second plug is 64 m 3 , and the dosage of the third plug is 4 m 3 . In order to meet the requirements of the injection pressure of each plug in the field construction, the dosages of the plugs can be adjusted slightly within the range.

[0093] The radius of the self-softening particle is required to be greater than the matrix pore throat radius of the target layer and less than 1 / 3 of the main fracture pore throat radius, and the matrix pore throat radius of the target layer and the main fracture pore throat radius are calculated by the following formula:

[0094]

[0095] where: r - pore throat radius, μm

[0096] K - matrix or main fracture permeability, μm 2 ;

[0097] τ - tortuosity

[0098] φ - formation porosity, fraction

[0099] The matrix permeability is 0.01332 μm 2 ; according to the indoor core test simulation AN oilfield reservoir properties and NP297 well fracturing parameters, the permeability of the artificial core obtained by the physical model is 1.1 μm 2 ; the porosity is 0.175; the tortuosity is 65; the matrix pore throat radius of the calculated target layer is 51 μm, the 1 / 3 main fracture pore throat radius is 146 μm, and the self-softening particle radius is determined as 100 μm.

[0100] The connecting pipeline is tested for water injection; a first plug is injected, which is 10% chlorovinyl acetate resin particles suspended in a phenolic resin gel with a viscosity of 200 mPa.s, after 3 cubic meters of injection, the injection pressure rises to 18 MPa and the increase slows down; a second plug is injected, which is a mixture of 0.3% zwitterionic polyacrylamide, 0.3% m-dihydroxybenzene and 0.02% oxalic acid, after 68 cubic meters of injection, the pressure is stably maintained between 24-25 MPa; a third plug is injected, which is a mixture of 0.3% zwitterionic polyacrylamide and 0.3% m-dihydroxybenzene, the injection amount is 4 cubic meters; the polyacrylamide polymer solution is injected to displace the top, and the chemical plugging agent is extrapolated to 5-10 meters outside the perforation gun, leaving the perforation gun, so that the remaining oil on both sides of the plugged fracture can flow into the wellbore, and the polymer solution has high displacement efficiency, which can effectively prevent the plugging agent from remaining and welding the wellbore; after the well is closed for 72 hours, clean water is injected, and there is no injection amount, which proves that the chemical water plugging process is effective; the working string is pulled out, the production string is lowered, and normal production is carried out.

[0101] The plug type chemical water plugging process for plugging the perforation completion horizontal well fracturing main fracture of the water flooding oilfield is applied in the NP297 well, and after the chemical water plugging, the water cut of the well is reduced from 99.9% to 65.6%; the oil well NP295 in the horizontal well area of other water injection directions recovers the liquid supply after the chemical water plugging of the NP297 well, and the daily oil increment is 0.3 tons / day.

[0102] The plug-type chemical water shutoff process for fracturing main fractures of perforation completion horizontal wells in water drive oilfields has been field tested in 3 wells, the operation string is all safely tripped in and out, the risk of horizontal well overhaul is reduced, the cumulative oil increment of 1068.5t in the well area is realized, which shows that the plug-type chemical water shutoff process can effectively plug the water breakthrough fractures of horizontal wells, expand the water injection swept area, effectively tap the remaining oil in the water breakthrough horizontal wells and other water injection directions in the horizontal well area, realize water control and oil increment, and has good application prospect.

Claims

1. A plug-type chemical water shutoff process for fracturing a main fracture section of a water-drive oilfield perforation completion horizontal well, characterized in that: It comprises the following steps: (1) selecting a chemical water plugging target horizontal well; (2) lowering a construction pipe string; (3) determining that the injection chemical plugging slug section number is three, which are respectively a first slug, a second slug and a third slug; and determining the chemical plugging agent dosage of the three slugs; (4) sequentially injecting the first slug, the second slug and the third slug chemical plugging agent; (5) injecting polyacrylamide polymer solution to displace until the chemical plugging agent is pushed out to 5-10 meters outside the perforation gun; (6) closing the well for 48-72 hours; (7) verifying the effectiveness of the process; if the process is effective, the next step is carried out; if the process is not effective, it means that the fracture is not plugged, and the second slug and the third slug are re-injected according to the above step (4); (8) lifting the construction pipe string and lowering the production pipe string for normal production; The first slug is a suspendable self-softening particle for temporary plugging of branch fractures; the suspendable self-softening particle comprises a self-softening particle and a suspending agent; The self-softening particle is a resin-based plugging agent, the self-softening particle is greater than the matrix pore throat radius of the target layer and less than 1 / 3 of the main fracture pore throat radius, which ensures that the particle can enter the fracture but not the target layer matrix, plugging the fracture while not blocking the matrix oil flow channel; the self-softening particle softening point is 5-10℃ lower than the target layer temperature, so that the particle softens and deforms after entering the target layer, plugging micro-fractures and secondary fractures and enhancing the plugging effect; And / or, The suspending agent is a weak gel with a viscosity of 100-200 mPa.s for suspending particles; after the suspending agent carrying the self-softening particle enters the formation, the suspending agent breaks, the particle softens and deforms under the formation temperature condition, plugging micro-fractures and secondary fractures, and is mutually soluble with oil, so that oil flow can pass through, and is not mutually soluble with water, preventing water phase from passing through, thereby playing a role in protecting the oil flow channel; The second slug is an organic gel for plugging the main fracture; The initial viscosity of the organic gel is less than 200 mPa.s, which is easy to flow in the wellbore to ensure smooth pumping; the gel strength is greater than 50000 mPa.s, which can plug the fracture and the water flow is not easy to break through; the gelation time is between 30-72 hours, which ensures that it does not solidify during injection and is produced within 72 hours after injection.

2. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 1, characterized in that: The chemical plugging agent dosage of the three slugs is calculated by volume: the first slug is 4-12 parts; the second slug is 32-90 parts; the third slug is 2-8 parts; the chemical plugging agent dosage is the sum of the theoretical dosage and the filtration loss; And / or, The method for injecting the first slug, the second slug and the third slug chemical plugging agent is: The first slug is sequentially injected; when the injection pressure is 16-20 MPa and the pressure rise rate slows down, the second slug is injected; until the injection pressure is stable and maintained between 22 MPa-25 MPa, the third slug chemical plugging agent is injected.

3. The slug type chemical water plugging process for plugging the main fracture of the perforation completion horizontal well of the water drive oilfield according to claim 2, characterized in that: The mass concentration of the self-softening particle and the suspending agent is: the self-softening particle is 10%-30%, and the suspending agent is 70%-90%.

4. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 1, characterized in that: The resin-based plugging agent is any one of chlorovinyl resin, phenolic resin and oil-soluble resin modified from pine resin; And / or, The weak gel is a phenolic resin gel or a chromium gel.

5. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 1, characterized in that: The organic gel is mixed and maintained at the temperature of the target layer by 0.1%-0.5% zwitterionic polyacrylamide, 0.2%-0.5% m-dihydroxybenzene and 0.02%-0.05% oxalic acid.

6. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 1, characterized in that: The third plug is a high-strength organic gel, which plays a sealing role and prevents the aforementioned plug from flowing back. The third plug is mixed and maintained at the temperature of the target layer by 0.5%-0.7% zwitterionic polyacrylamide and 0.25%-0.6% m-dihydroxybenzene.

7. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 6, characterized in that: The initial viscosity of the high-strength organic gel is greater than 250 mPa.s, which can flow in the wellbore, ensure smooth pumping and push the aforementioned plug to the formation uniformly; the gel strength is greater than 140000 mPa.s, which ensures that the aforementioned plug does not flow back; the gelation time is between 5 and 20 hours, which ensures that the gel does not solidify during injection and the plug does not flow back.

8. The plug chemical water shutoff process for fracturing main fracture of the water drive oilfield perforation completion horizontal well of claim 1, characterized in that: The target horizontal well for chemical water shutoff should meet the following conditions: daily liquid production is greater than or equal to 2 tons, water cut is greater than or equal to 80%, the water breakthrough fracture section is clear, the chemical water shutoff target layer section has qualified cementing quality and there is no casing deformation or damage.

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