Composite water shutoff agent system and multi-slug water shutoff method

Abstract

The application discloses a composite water plugging agent system, which comprises a nanometer water plugging agent XSYD-1, a micrometer water plugging agent XSYD-2, a selective gel composite water plugging agent XSYNJ-3, a high-strength thermosetting resin system XSYFK-4 and a weak gel system XSYDT-5; the nanometer water plugging agent XSYD-1, the micrometer water plugging agent XSYD-2, the selective gel composite water plugging agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4 and the weak gel system XSYDT-5 correspond to five spacers in the order of injection into a well; and the five spacers in the order of injection into the well are respectively a pre-spacer, a main-spacer, a post-spacer, a sealing-spacer and a displacement-spacer. The system can achieve the purpose of deep plugging of an oil layer and greatly improve the effective period of water plugging. A multi-spacer water plugging method is also provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water plugging in oil and gas field development, and particularly relates to a composite water plugging agent system and a multi-slug water plugging method. BACKGROUND

[0002] With the extension of oilfield development time, the formation pressure is continuously reduced, and most of the oilfields mainly use the "secondary oil recovery" mode through water injection development to improve the production and the oil recovery ratio. For an oilfield developed by water injection for a long time, due to the heterogeneity of the reservoir plane and the vertical direction and the difference in oil and water viscosity, the injected water will inevitably rush to the production well along the high permeability zone and channel, thus causing the inefficient or ineffective circulation of the injected water. After decades of intensified development, many oilfields in China have entered the medium-high water cut stage, at which time the underground recoverable reserves are still large, and about 40% of the water injection development reserves are still unused. At the same time, the efficiency of the measures for increasing production and injection widely used under the original water injection conditions is getting lower and lower, and the situation of "high water cut, high investment and low output" appears, the technical difficulty is getting higher and higher, the production is decreasing, the water production is greatly increased, and the economic benefit is poor. Meanwhile, fracturing, acidizing and high-intensity development will cause the problems of injected water tongue, edge water breakthrough, bottom water coning and the channeling of external water, which not only affects the oil production, but also consumes energy, increases the processing cost of the produced liquid and causes pipeline corrosion, thus increasing the cost of oil production and causing environmental pollution. Some oil wells may also appear explosive water flooding, which leads to the shutdown of the oil well and causes a large amount of resource waste. Therefore, how to effectively plug water has become a serious problem in oilfield development.

[0003] The current water plugging technology mainly includes mechanical water plugging and chemical water plugging. The so-called mechanical water plugging technology is to use a packer to block the water outflow layer in the wellbore to prevent water from flowing into the well, and to block the water outflow layer in the oil well. The water plugging method includes blocking the upper part, blocking the lower part, blocking the middle part and producing from both ends, and blocking both ends and producing from the middle. The packer is required to be tightly and accurately sealed, which is the guarantee for the success of mechanical water plugging. The mechanical water plugging method is simple, easy to operate, low in cost and high in effect, but it cannot be used in oil wells where the packer cannot be sealed or the oil and water cannot be separated due to other reasons. Oil well chemical water plugging is a process technology that injects a chemical agent into the high permeability water outflow layer through an oil well to reduce the water phase permeability in the near wellbore zone and control the production of injected water, bottom water and edge water, so as to improve the oil production. The chemical method does not require workover equipment, is economical and convenient to operate, and is widely used. The chemical agent used in chemical water plugging is called water plugging agent. At present, there are three types of water plugging agents, namely polymer gel plugging agent (gel gel type), water glass calcium chloride precipitation type plugging agent (water swelling type) and cement type, but they all have certain limitations. At the same time, the current water plugging agent is mainly one type of plugging agent, and the water plugging process can only seal one type of pore or crack, which has the problems of small sealing radius, poor pressure-bearing capacity, short effective period, etc. SUMMARY

[0004] The first object of the present application is to provide a composite water plugging agent system, which can not only effectively plug the far-end micro-cracks and pores, the slightly larger cracks of the sub-far-end, but also plug the front section of the main cracks, the large cracks and the high permeation channels by using the multi-slug water plugging process, so as to achieve the purpose of deep plugging of the oil layer and greatly improve the effective period of water plugging.

[0005] The second object of the present application is to provide a multi-slug water plugging method.

[0006] The first technical solution adopted by the present application is a composite water plugging agent system, which comprises a nanoscale water plugging agent XSYD-1, a microscale water plugging agent XSYD-2, a selective gel composite water plugging agent XSYNJ-3, a high-strength thermosetting resin system XSYFK-4 and a weak gel system XSYDT-5; the nanoscale water plugging agent XSYD-1, the microscale water plugging agent XSYD-2, the selective gel composite water plugging agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4 and the weak gel system XSYDT-5 correspond to five slugs in the order of entering the well; the five slugs in the order of entering the well are respectively a pre-slug, a main slug, a post-slug, a sealing slug and a displacement slug.

[0007] The present application is further characterized in that,

[0008] The nanoscale water plugging agent XSYD-1 comprises the following components by weight: 5-8 parts of white oil, 30-40 parts of a copolymer monomer, 10-14 parts of a composite emulsifier, 20-26 parts of a composite monomer, 20-26 parts of deionized water, 0.2-0.3 parts of a crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidyl ethanolamine, and 0.02-0.03 parts of an initiator. The copolymer monomer is composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide, and alkyl succinate sulfonate in any ratio; the composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio; the composite monomer is composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid in any ratio; the crosslinking agent is N,N'-methylenebisacrylamide; and the initiator is azobisisobutyronitrile or azobisisoheptyl nitrile, or a mixture of azobisisobutyronitrile and azobisisoheptyl nitrile, and the volume ratio of the two in the mixture is 1:1.

[0009] The preparation method of the nanoscale water plugging agent XSYD-1 specifically comprises the following steps:

[0010] Step 1, add the comonomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonate acetamide, alkyl succinate sulfonate into the white oil, stir evenly, then add the composite emulsifier mixed by sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether, and prepare the oil phase; Step 2, weigh the composite monomer mixed by acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid, and dissolve in deionized water, then sequentially add the crosslinking agent of N,N'-methylenebisacrylamide, rhamnolipid, and phosphatidylethanolamine, mix and stir evenly, and prepare the water phase; Step 3, place the oil phase in a reaction kettle, stir the solution evenly by using a magnetic stirring needle, then slowly add the water phase for emulsification, stir while adding, the stirring speed is 150 rpm-200 rpm, and the emulsification time is 0.5 hour-1 hour; Step 4, after the emulsification is completed, the reaction kettle is heated to 30℃, and nitrogen is introduced for 0.5 hour-1 hour to remove oxygen; Step 5, after being heated to 60℃, the initiator of azobisisobutyronitrile or azobisisoheptyl nitrile is added to initiate the polymerization reaction, and the temperature is kept for 2 hours-3 hours;

[0011] Step 6, the nanoscale water plugging agent is obtained by using centrifugal separation; specifically, after being cooled to room temperature, the liquid after the polymerization reaction obtained in Step 5 is centrifuged by using anhydrous ethanol, the speed is 6000 rpm-8000 rpm, and the centrifugation time is 10 minutes-15 minutes.

[0012] The raw material components and the proportion of the microscale water plugging agent XSYD-2 are the same as those of the nanoscale water plugging agent XSYD-1; the preparation method of the microscale water plugging agent XSYD-2 is the same as Steps 1-5 of the preparation method of the nanoscale water plugging agent XSYD-1, and the difference lies in Step 6; Step 6 of the preparation method of the microscale water plugging agent XSYD-2 is: after being cooled to room temperature, the liquid after the polymerization reaction obtained in Step 5 is centrifuged by using anhydrous ethanol, the speed is adjusted to 2000 rpm-3000 rpm, and the centrifugation time is 8 minutes-10 minutes.

[0013] The selective gel composite water plugging agent XSYNJ-3 comprises the following components by weight: 0.6-1.2 parts by weight of modified polyacrylamide, 0.6-1.5 parts by weight of the crosslinking agent of N,N'-methylenebisacrylamide, 0.03-0.05 parts by weight of the stabilizer of N-vinylpyrrolidone, and 95-98 parts by weight of deionized water.

[0014] The high-strength thermosetting resin system XSYFK-4 has the following formula: based on 100 parts by weight of micro-swelling early-strength Portland cement, the micro-swelling early-strength Portland cement is 100 parts, the high-strength thermosetting resin is 300 parts, the curing agent is 30-48 parts, the fluid loss additive is 2-3 parts, the setting regulator is 0-10 parts, the defoaming agent is 0.5-1 part, and the water is 35-120 parts.

[0015] The high-strength thermosetting resin system XSYFK-4 formula comprises:

[0016] (1) Micro-swelling early-strength Portland cement, which is composed of the following components in percentage by weight: 96-97% G-grade cement, 1.2-1.5% expanding agent F17A-1, 1.8-2.0% early-strength agent GJ-F, and 0.3-0.5% drag-reducing agent USZ, and the sum of the mass percentages of the above components is 100%;

[0017] (2) The chemical formula of the high-strength thermosetting resin is as follows:

[0018]

[0019] (3) The curing agent is an acid anhydride;

[0020] (4) The fluid loss reducer is modified cellulose CMC;

[0021] (5) The coagulant is trisodium citrate;

[0022] (6) The defoaming agent is composed of the following components in percentage by weight: 40%-50% silicone oil, 20%-30% sodium tetroxide, and 20%-30% hydrophobic silicon dioxide, and the sum of the mass percentages of the above components is 100%.

[0023] The micron-sized swelling water shutoff agent XSYD-2 is diluted to obtain a solution with a concentration of only 20% of the micron-sized swelling water shutoff agent XSYD-2, and the solution is the weak gel system XSYDT-5. The weak gel system XSYDT-5 comprises the following components in parts by weight: 5-8 parts of white oil, 30-40 parts of a copolymer monomer, 10-14 parts of a composite emulsifier, 20-26 parts of a composite monomer, 100-130 parts of deionized water, 0.2-0.3 parts of a crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidyl ethanolamine, and 0.02-0.03 parts of an initiator.

[0024] The second technical solution adopted by the present application is a multi-section plug water method, which uses the above-mentioned composite water shutoff agent system and is implemented according to the following steps: running the pipe string, well flushing, well washing, casing pressure test, and multi-section plug water operation.

[0025] The present application is also characterized in that,

[0026] The multi-section plug water operation is implemented according to the following steps:

[0027] The first step is to lower the water plugging drill, seat the wellhead, and connect the surface blowout line; the second step is to close the casing gate, adopt the tubing positive displacement mode, pump the nanometer water plugging agent XSYD-1 used in the first preflush plug, the displacement is 800L / min-1000L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; the third step is to continue to adopt the tubing positive displacement mode, pump the micron water plugging agent XSYD-2 used in the second main plug, the displacement is 700L / min-1200L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; the fourth step is to continue to adopt the tubing positive displacement mode, pump the selective gel composite water plugging agent XSYNJ-3 used in the third postflush plug, the displacement is 700L / min-1200L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; the fifth step is to continue to adopt the tubing positive displacement mode, pump the high-strength thermosetting resin system XSYFK-4 used in the fourth sealing plug, the displacement is 500L / min-1000L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition, or the intermittent displacement mode is adopted to ensure that the pressure gradually increases, and after the pump is stopped, the pressure drop is less than 3Mpa; in the fifth step, the intermittent displacement sealing mode is adopted, that is, the displacement is completed multiple times without adopting this displacement completion mode, and the displacement is carried out every 10min-20min, and every time interval is 10min-15min, after the high-strength thermosetting resin system XSYFK-4 is cured and the pressure is raised, the displacement pressure is continuously increased, and finally the designed amount is displaced; the sixth step is to continue to adopt the tubing positive displacement mode, pump the weak gel system XSYDT-5 used in the fifth displacement plug, the displacement is 500L / min-600L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition, to ensure that the wellbore is filled with the weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is squeezed into the formation, and after the pressure is raised to 20MPa or more, the well is closed and cured for 72-96 hours; the seventh step is to close the well and cure for 72-96 hours after the water plugging measure is completed, and the blowout is controlled, and the pressure drop is observed: the blowout is controlled in four stages: the first stage adopts a 4mm-5mm nozzle to blow out until the wellhead pressure is less than 5MPa; the second stage adopts an 8mm nozzle to blow out until the wellhead pressure is less than 3MPa; the third stage adopts a 10mm-12mm nozzle to blow out until the wellhead pressure is less than 1MPa; the fourth stage: completely open the wellhead gate for open blowout, and accurately measure the liquid amount; the eighth step is to carry out fracturing construction, flowback, and pump down according to the geological requirements.

[0028] The beneficial effects of the present application are:

[0029] (1) The composite water plugging agent system of the present application is mainly composed of nano-level plugging agent, micron-level swelling plugging agent, selective gel plugging agent and high-strength plugging agent, and a multi-slug water plugging process is adopted, which can not only effectively plug the far-end micro-cracks and pores and the slightly larger cracks of the next far-end, but also plug the front section of the main cracks, large cracks and high permeation channels; the multi-slug design is from weak to strong, which realizes effective plugging of the end, branch cracks and main cracks, has a large plugging radius and can achieve the purpose of deep plugging of the oil layer, and greatly improves the effective period of water plugging.

[0030] (2) In the composite water plugging agent system of the present application, the initial viscosity of the nano-level water plugging agent XSYD-1 and the micron-level swelling water plugging agent XSYD-2 is low, which is easy to pump into the stratum, and the performance is stable after swelling, so that the high water cut oil well can be effectively plugged.

[0031] (3) In the composite water plugging agent system of the present application, the selective gel composite water plugging agent XSYNJ-3 has good injection selectivity to the target layer, has the characteristics of high strength and good rheological property, and can preferentially enter large pores or high permeation layer. The development of micro-cracks in the reservoir or the number of artificial cracks requires the amount of plugging agent. For the reservoir with small difference in horizontal stress and large micro-cracks, multiple artificial cracks are formed after fracturing. For such wells, the amount of plugging agent should be increased to achieve the effect of water plugging and oil increasing.

[0032] (4) In the aspect of optimization of the oil well water plugging process of the present application, the methods such as low displacement squeeze, segmented plug squeeze and variable viscosity alternate squeeze can effectively improve the water plugging effect. The corresponding injection well should be stopped before water plugging, which can effectively expand the plugging agent's range and improve the water plugging effect. Without stopping the corresponding injection well, the plugging agent enters the water-flooded channel rarely due to the high pressure of the water-flooded cracks, so the plugging efficiency is affected.

[0033] (5) The method of the present application can improve the injection and production effect of the well group and improve the injection effect of the well group by water plugging. The combination of water plugging and steering fracturing, acidification and other technologies can achieve the purpose of "reducing water and increasing oil".

[0034] (6) The purpose of the multi-slug design of the method of the present application has three aspects in general: first, to let the plugging agent select independently and preferentially plug the water phase permeation channel, second, to let the plugging agent reach the strength designed in the scheme, and third, to let the plugging strength have a level between "strong" and "weak" for better playing the respective roles. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of the slug water plugging of the multi-composite water plugging agent system of the present application;

[0036] Figure 2 It is a micro-morphology diagram of the nano-level water plugging agent XSYD-1 in the present application;

[0037] Figure 3 The micrograph of the micron-sized swelling water shutoff agent XSYD-2 in the present application is shown in the figure;

[0038] Figure 4 The gelation performance evaluation results of the selective gel composite water shutoff agent XSYNJ-3 selected in Example 1 are shown in the table;

[0039] Figure 5 The stability performance evaluation results of the selective gel composite water shutoff agent XSYNJ-3 selected in Example 1 are shown in the table.

[0040] In the figure, 1 is a preflush, 2 is a main slug, 3 is a postflush, 4 is a sealing slug, 5 is a displacement slug, 6 is a water well, and 7 is an oil well. DETAILED DESCRIPTION

[0041] The present application will be described in detail below in combination with the figures and specific embodiments.

[0042] The present application provides a composite water shutoff agent system, which comprises a nanoscale water shutoff agent XSYD-1, a micron-sized water shutoff agent XSYD-2, a selective gel composite water shutoff agent XSYNJ-3, a high-strength thermosetting resin system XSYFK-4, and a weak gel system XSYDT-5. The nanoscale water shutoff agent XSYD-1, the micron-sized water shutoff agent XSYD-2, the selective gel composite water shutoff agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4, and the weak gel system XSYDT-5 correspond to five slugs in the order of injection into a well, respectively. Figure 1 As shown in the figure, the five slugs in the order of injection into a well are a preflush 1, a main slug 2, a postflush 3, a sealing slug 4, and a displacement slug 5. The preflush 1 is close to the side of a water well 6, and the displacement slug 5 is close to the side of an oil well 7.

[0043] The first slug is a preflush, which adopts the nanoscale water shutoff agent XSYD-1. The water shutoff agent is composed of polymer microspheres, which are only nanoscale, as shown in the figure, with a particle size range of 100-800 nanometers, and can swell when encountering water, so that the plugging of formation pore throats can be achieved. In the initial injection period, the original size of the microspheres is only nanoscale, which is much smaller than the size of the formation pore throats, so the microspheres can enter the deep part of the formation along with the injected water. With the continuous extension of the injection time, the microspheres continuously hydrate and swell, and the swelling system can reach 100 times the initial volume, thereby plugging large pores or high permeability layers and improving the liquid production profile. Figure 2

[0044] ​The nanoscale water plugging agent XSYD-1 comprises the following components by weight: 5-8 parts of white oil, 30-40 parts of a copolymer monomer, 10-14 parts of a composite emulsifier, 20-26 parts of a composite monomer, 20-26 parts of deionized water, 0.2-0.3 parts of a crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidyl ethanolamine, and 0.02-0.03 parts of an initiator. The copolymer monomer is composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkylsulfonic acid-based acetamide, and alkyl succinate sulfonate in any ratio. The composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio. The composite monomer is composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid in any ratio. The crosslinking agent is N,N'-methylenebisacrylamide. The initiator is azobisisobutyronitrile or azobisisoheptyl nitrile, or a mixture of azobisisobutyronitrile and azobisisoheptyl nitrile, and the volume ratio of the two in the mixture is 1:1.

[0045] The preparation method of the nanoscale water plugging agent XSYD-1 specifically comprises the following steps:

[0046] Step 1: The white oil is added into the copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkylsulfonic acid-based acetamide, and alkyl succinate sulfonate in any ratio, and stirred uniformly, and then the composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio is added to prepare an oil phase. Step 2: The composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid in any ratio is weighed and dissolved in deionized water, and then the crosslinking agent N,N'-methylenebisacrylamide, rhamnolipid, and phosphatidyl ethanolamine are sequentially added and stirred uniformly to prepare an aqueous phase. Step 3: The oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and then the aqueous phase is slowly added for emulsification, with stirring at a speed of 150 rpm-200 rpm for 0.5-1 hour. Step 4: After the emulsification is completed, the reaction kettle is heated to 30°C, and nitrogen is introduced for 0.5-1 hour to remove oxygen. Step 5: After being heated to 60°C, the initiator azobisisobutyronitrile or azobisisoheptyl nitrile is added to initiate the polymerization reaction, and the temperature is maintained for 2-3 hours. Step 6: The nanoscale water plugging agent is obtained by centrifugal separation. Specifically, after being cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged at a speed of 6000 rpm-8000 rpm for 10-15 minutes using anhydrous ethanol to obtain nanoscale polymer microspheres with a particle size range of 100-800 nanometers.

[0047] The second plug is a main plug, which uses micron water plugging agent XSYD-2 to plug the fractures to 25 meters from the perforation hole and to increase the static pressure in the fractures. A self-controlled volume water absorbing and swelling plugging agent is designed. The volume is greatly expanded by absorbing water, and the particles also have a certain elasticity after absorbing water, which can deform and extrude into the leakage fractures of the formation to form a plugging layer with high strength and toughness. The micron water plugging agent XSYD-2 can overcome the shortcomings of inorganic profile control agents, such as being dead and shallow, not moving, and being not conducive to deep profile control and repeated profile control. The micron water plugging agent XSYD-2 can also avoid the weaknesses of organic profile control agents, such as low strength and being unable to plug high permeability zones. At the same time, the micron water plugging agent XSYD-2 can absorb the advantages of organic and inorganic profile control agents, effectively plug high permeability zones, and maintain the characteristics of deformability and diffusibility, and migrate to the deep part of the formation under the action of formation pressure and fluid power. The main purpose of the micron water plugging agent XSYD-2 is to plug micro fractures, and the composition is micron expanded microsphere water plugging agent, which is composed of micron polymer microspheres and is a micron polymer gel sphere. The appearance and expanded morphology of the polymer microspheres are analyzed by three-dimensional optical microscopy, as shown in FIG. 1. Figure 2 As can be seen from FIG. 1, the particle size of the microspheres is relatively uniform, the sphericity is high, and the dispersibility and suspensibility in the solution are good. The particle size of the micron polymer gel sphere in this area is 10-30 microns. The micron water plugging agent XSYD-2 can be uniformly dispersed in water at any concentration, and can expand by tens or even hundreds of times after absorbing water. The micron water plugging agent XSYD-2 can take advantage of small particle size, and at the same time, protect the low permeability oil flow channel from being contaminated, and plug the relatively large water permeation channel.

[0048] The composition of the micron water plugging agent XSYD-2 is the same as that of the nanometer water plugging agent XSYD-1, the steps 1-5 of the preparation method of the micron water plugging agent XSYD-2 are the same as those of the preparation method of the nanometer water plugging agent XSYD-1, and the difference lies in the step 6. The step 6 of the preparation method of the micron water plugging agent XSYD-2 is: after being reduced to room temperature, the liquid obtained after the polymerization reaction in step 5 is centrifuged with anhydrous ethanol, the speed is adjusted to 2000 rpm-3000 rpm, and the centrifugation time is 8 minutes-10 minutes, so that the polymer microspheres are micron, and the particle size range is 10-30 microns, to obtain the micron water plugging agent XSYD-2.

[0049] The second plug uses micron expanded plugging agent to plug large channels and micro fractures, and the pressure rise amplitude is small during injection, and the injection is stable.

[0050] The third plug is a post-plug, which uses a selective gel composite water plugging agent XSYNJ-3. The selective gel composite water plugging agent XSYNJ-3 is a three-dimensional network structure gel system formed by polymers and crosslinking agents, which mainly crosslinks between molecules and secondarily crosslinks within molecules. The selective gel composite water plugging agent XSYNJ-3 plugs the main fractures, can effectively enter the fractures and then gel, and has a certain strength after gelling. The system is a water-soluble substance before crosslinking, and generates lipophilic groups after crosslinking, so as to form a network gel structure in the formation, which allows oil to pass but blocks water.

[0051] The selective gel type composite water plugging agent XSYNJ-3 comprises the following components in parts by weight: 0.6-1.2 parts by weight of modified polyacrylamide, 0.6-1.5 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 0.03-0.05 parts by weight of a stabilizer of N-vinylpyrrolidone, and 95-98 parts by weight of deionized water.

[0052] The selective gel type composite water plugging agent XSYNJ-3 is prepared by mixing 0.6-1.2 parts by weight of modified polyacrylamide, 0.6-1.5 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, and 0.03-0.05 parts by weight of a stabilizer of N-vinylpyrrolidone with 95-98 parts by weight of deionized water into a solution, uniformly stirring, and allowing the solution to react for 1-1.5 hours to generate the selective gel type composite water plugging agent XSYNJ-3.

[0053] The third plug gradually seals the water fracture group and the high-permeability channel to achieve complete sealing, the gel type plugging agent is used to seal the front end of the main fracture, and the injection pressure rises by 3-5 MPa.

[0054] The fourth plug is a sealing plug, and a high-strength thermosetting resin system XSYFK-4 is used as the sealing agent. The high-strength thermosetting resin system XSYFK-4 has the following formulation: based on 100 parts by weight of micro-swelling early-strength Portland cement, the micro-swelling early-strength Portland cement is 100 parts, the high-strength thermosetting resin is 300 parts, the curing agent is 30-48 parts, the fluid loss additive is 2-3 parts, the setting regulator is 0-10 parts, the defoaming agent is 0.5-1 part, and the water is 35-120 parts.

[0055] The high-strength thermosetting resin system XSYFK-4 is prepared by mixing the components including the high-strength thermosetting resin emulsion, the micro-swelling early-strength Portland cement, the curing agent, the fluid loss additive, the setting regulator, the defoaming agent, and the water, and uniformly mixing to obtain the high-strength thermosetting resin system XSYFK-4.

[0056] The chemical formula of the high-strength thermosetting resin is as follows:

[0057]

[0058] The curing agent is an acid anhydride.

[0059] The fluid loss additive is modified cellulose CMC (carboxymethyl cellulose).

[0060] The setting regulator is trisodium citrate [HC(COONa)CH2(OONa)2·2H2O].

[0061] The defoamer is composed of the following components by weight percentage: 40%-50% silicone oil, 20%-30% sodium stearate, and 20%-30% hydrophobic silica, with the sum of the mass percentages of the above components being 100%.

[0062] High-strength thermosetting resin reacts chemically with curing agent, undergoing ring-opening, addition, and condensation reactions to crosslink and form a dense, three-dimensional polymer cured body.

[0063] The optimal ratio of high-strength thermosetting resin emulsion to curing agent is 100:10-16. High-strength thermosetting resin slurry also exhibits the right-angle thickening characteristics of cement slurry.

[0064] Micro-expansion, early-strength silicate cement is composed of the following components by weight percentage: 96-97% Grade G cement, 1.2-1.5% expansion agent F17A-1, 1.8-2.0% early-strength agent GJ-F, and 0.3-0.5% drag-reducing agent USZ, with the sum of the mass percentages of the above components being 100%. It is a micro-expansion, early-strength silicate cement system. After mixing, the water-cement ratio, calculated by weight, is 4:10 (cement to water). After curing, the compressive strength can reach 29 MPa. The initial setting time is controllable and adjustable within the range of 70-150 minutes, with a slight volume expansion of 0.2%, forming a good bonding interface. It features no shrinkage after curing, tight sealing, and continuous expansion force at the sealed area.

[0065] The high-strength thermosetting resin system XSYFK-4 can seal large cracks and high-permeability channels in water outlets. It has high rigidity, high hardness, high temperature resistance, and micro-expansion effect, which greatly improves the pressure resistance and sealing performance of the sealing opening.

[0066] The high-strength thermosetting resin system XSYFK-4, when cured at 162°F (72°C) for 48 hours and subjected to a compressive strength test at 72°C, exhibits a strength of up to 8200 psi and retains high elasticity even with a deformation of nearly 20%.

[0067] The fourth sluice plug seals the large fractures and high-permeability channels at the water outlet using a high-strength sealing agent. The sluice plug is designed from weak to strong to effectively seal the main fracture, branch fracture, and end fracture. The injection methods mainly adopt two injection methods: water-stopping truck and plunger pump, to achieve deep sealing of the oil layer and extend the effective period of water shut-off.

[0068] The fifth slug is a displacement slug, using the weak gel system XSYDT-5 as the final displacement agent. The weak gel system XSYDT-5 comprises the following components by weight: 5–8 parts white oil, 30–40 parts comonomer, 10–14 parts complex emulsifier, 20–26 parts complex monomer, 100–130 parts deionized water, 0.2–0.3 parts crosslinking agent, 2–3 parts rhamnolipid, 2–3 parts phosphatidylethanolamine, and 0.02–0.03 parts initiator.

[0069] The preparation method of the weak gel system XSYDT-5 is as follows: the preparation method of the weak gel system XSYDT-5 is the same as that of the micro-scale swelling water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is 5 times that of the micro-scale swelling water plugging agent XSYD-2, and the concentration is only 20% of that of the micro-scale swelling water plugging agent XSYD-2.

[0070] The plug can ensure that the high-strength thermosetting resin system XSYFK-4 reaches the accurate position of the seal, and provide a stable working condition environment in which the sealant is not diluted by water and no liquid flows, so that the seal is tight and is not disturbed by the outside world.

[0071] The weak gel system XSYDT-5 has a certain viscosity, and can well separate the high-strength thermosetting resin system XSYFK-4 from water during the displacement process, so that water is prevented from continuously entering due to the influence of displacement pressure and pumping speed during the displacement process, the sealing condition of the high-strength thermosetting resin system XSYFK-4 is affected, and the sealing strength and sealing performance are ensured.

[0072] The application also provides a multi-plug water plugging method, which adopts the above-mentioned water plugging agent system.

[0073] ①Lifting pipe column: lifting out the original well pipe rod and accessories, cleaning with hot steam, and replacing unqualified pipes.

[0074] ②Well passing and well washing: lowering a well passing rule of appropriate specification, and performing well passing and washing operations to the artificial well bottom. The well washing is performed by using positive circulation, the well washing fluid is 30-50 m 3 (adjusting according to the well depth and well condition), the well washing displacement is 400-500 L / min, the inlet and outlet water colors of the returned well washing fluid are consistent, and the artificial well bottom operation is performed again. If resistance is encountered in the well passing, the well hole is treated first, and then the well passing is continued.

[0075] ③Casing pressure test: lowering a pressure test drilling tool to test the casing above the perforation section, and using clean water to test the pressure to 20-25 MPa. If the pressure drop is less than 0.5 MPa within 20-30 minutes, the test is qualified. Otherwise, a double sealing leak finding operation or a cable logging leak finding operation is performed.

[0076] ④Multi-plug water plugging operation

[0077] First step, lowering the water plugging drilling tool, seating the well mouth, and connecting the ground blowout pipeline. The tool is not allowed to be put into the well for more than 24 hours before construction, the pipe column is required to be accurately measured to ensure that the tool position is accurate and correct. The KQ65 / 70 type well mouth is used in the water plugging construction, and the pipe column structure (from bottom to top) is as follows: 45° oblique tip (determined according to the well body structure) + external thickening oil pipe (plain oil pipe) to the well mouth.

[0078] The second step is to close the sleeve gate and adopt the oil pipe positive extrusion mode to pump the first section pre-plug (nanometer water shutoff agent XSYD-1) with a displacement of 800-1000 L / min, a pressure less than 25 MPa, and a liquid volume designed according to the well condition, and to calculate the water absorption index and make a record.

[0079] The third step is to continue to adopt the oil pipe positive extrusion mode to pump the second section main plug (micron water shutoff agent XSYD-2) with a displacement of 700-1200 L / min, a pressure less than 25 MPa, and a liquid volume designed according to the well condition.

[0080] The fourth step is to continue to adopt the oil pipe positive extrusion mode to pump the third section post-plug (selective gel composite water shutoff agent XSYNJ-3) with a displacement of 700-1200 L / min, a pressure less than 25 MPa, and a liquid volume designed according to the well condition.

[0081] The fifth step is to continue to adopt the oil pipe positive extrusion mode to pump the fourth section sealing plug (high-strength thermosetting resin system XSYFK-4) with a displacement of 500-1000 L / min, a pressure less than 25 MPa, and a liquid volume designed according to the well condition, or to adopt the intermittent displacement mode to ensure that the pressure gradually increases, and the pressure drop is less than 3 MPa after the pump is stopped.

[0082] The intermittent displacement sealing mode is to displace multiple times without adopting this displacement completion mode, to displace once every 10-20 min, to interval for 10-15 min each time, to continuously increase the displacement pressure after the high-strength thermosetting resin system XSYFK-4 is cured and the pressure is built up, and finally to displace the designed amount.

[0083] The sixth step is to continue to adopt the oil pipe positive extrusion mode to pump the fifth section displacement plug (weak gel system XSYDT-5) with a displacement of 500-600 L / min, a pressure less than 25 MPa, and a liquid volume designed according to the well condition, to ensure that the wellbore is fully filled with the weak gel system XSYDT-5, and to extrude the excess high-strength thermosetting resin system XSYFK-4 into the formation. After the pressure is built up to more than 20 MPa, the well is closed for curing for 72-96 hours.

[0084] The seventh step is to close the well for curing for 72-96 hours after the water shutoff measures are completed, to control the blowout, and to perform the blowout in four stages according to the pressure drop: the first stage is to use a 4-5 mm choke to blow out until the wellhead pressure is less than 5 MPa; the second stage is to use an 8 mm choke to blow out until the wellhead pressure is less than 3 MPa; the third stage is to use a 10-12 mm choke to blow out until the wellhead pressure is less than 1 MPa; and the fourth stage is to completely open the wellhead gate for open blowout to accurately measure the liquid volume. The sample is taken for testing every shift, the production condition shift report is prepared, and the subsequent fracturing construction process is determined according to the liquid discharge.

[0085] Step 8, fracturing operation, flowback, and pumping according to geological requirements.

[0086] Example 1

[0087] Water plugging operation of L141-X oil well

[0088] First, according to the formation pressure coefficient and well structure of L141-X well, the required slug amount is calculated; then, five slug liquid is prepared; finally, water plugging operation is carried out. The specific operation steps are as follows:

[0089] 1) Preparation: 50m 3 large tank 15 (1 for collecting residual liquid), 30m 3 large tank 1, all tank rear end must be padded, tank must be cleaned. High pressure water hose, joint, elbow complete and good (require strength test pressure 25.0MPa). Prepare Φ73mm oblique tip one, Φ118mm×1.5m through well gauge one, GX-T140 scraper one, Φ73mm external thickening oil pipe 2000m, KQ65 / 70 type fracturing wellhead (require complete and good gate), K344-114 packer 1, 5 1 / 2" hydraulic anchor 1, Φ24mm straight nozzle 1, short section several. Before construction, prepare 700 type pump truck 1 for water, liquid distribution funnel one. Common tools and fire fighting equipment are prepared according to the normal construction needs. Labor protection tools (rubber gloves, gas mask, goggles, mask, towel, etc.) complete.

[0090] 2) Pipe string: pull out the original well tubing rod and accessories, hot steam flushing clean, and replace unqualified oil pipe.

[0091] 3) Through well, well washing: down Φ118mm×1.5m through well gauge through well to artificial well bottom, well washing fluid 30m 3 , well washing displacement 500L / min, the inlet and outlet water color of well washing fluid is consistent, and the sand surface or artificial well bottom is explored again. (If resistance is encountered during through well, the wellbore is treated first, and then the through well is continued).

[0092] 4) Casing pressure test: down the pressure test drill string to test the casing above the perforation section, clear water pressure test 25MPa, 30 minutes pressure drop less than 0.5MPa is qualified.

[0093] 5) Water plugging construction preparation: down water plugging drill string, seat wellhead, connect ground blowout pipeline. (The tool into the well time before construction should not exceed 24 hours, the pipe string should be accurately measured to ensure the tool position is accurate and correct). Water plugging construction uses KQ65 / 70 type wellhead.

[0094] 6) Water plugging pump injection: close the casing gate, adopt the oil pipe positive extrusion mode, pump the nanometer water plugging agent XSYD-1 used in the first pre-pad into, the displacement is 850 L / min, the pressure is less than 25 MPa, the liquid volume is 100 cubic meters. Then continue to adopt the oil pipe positive extrusion mode, pump the micron water plugging agent XSYD-2 used in the second main pad into, the displacement is 750 L / min, the pressure is less than 25 MPa, the liquid volume is 160 cubic meters. Then, continue to adopt the oil pipe positive extrusion mode, pump the selective gel composite water plugging agent XSYNJ-3 used in the third post-pad into, the displacement is 780 L / min, the pressure is less than 25 MPa, the liquid volume is 240 cubic meters. Then continue to adopt the oil pipe positive extrusion mode, pump the high-strength thermosetting resin system XSYFK-4 used in the fourth sealing pad into, the displacement is 600 L / min, the pressure is less than 25 MPa, the liquid volume is 3 cubic meters, and the pressure is gradually increased. After stopping the pump, the pressure drop is less than 3 MPa. Then continue to adopt the oil pipe positive extrusion mode, pump the weak gel system XSYDT-5 used in the fifth displacement pad into, the displacement is 500 L / min, the pressure is less than 25 MPa, the liquid volume is 10 cubic meters, and the wellbore is filled with the weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is extruded into the formation.

[0095] 7) When the pressure starts and stops above 20 MPa, shut in and wait for 72 hours. During the shut-in and waiting period, the wellhead tubing pressure and casing pressure are closely monitored, and a 700-type pump truck is prepared for water injection before construction.

[0096] 8) After the water plugging measure is completed, shut in and wait for 72 hours, and then control the blowout according to the pressure drop: in the first stage, use a 4mm nozzle to blow out until the wellhead pressure is less than 5 MPa; in the second stage, use an 8mm nozzle to blow out until the wellhead pressure is less than 3 MPa; in the third stage, use a 12mm nozzle to blow out until the wellhead pressure is less than 1 MPa; in the fourth stage: completely open the wellhead gate for open blowout, and accurately measure the liquid volume. Sample and test every shift, complete the production situation shift report, and report the production results in a timely manner. Determine the water plugging and fracturing construction according to the liquid discharge.

[0097] (9) Test well effect: before water plugging and fracturing, the daily liquid production of L141-X well was 2.16m 3 , the daily oil production was 0.3t, and the water content was 83.7%; after water plugging test, the liquid production was 3.72m 3 , the daily oil production was 1.4t, and the water content was 71.6%; the daily production increased by 1.1 tons, and the water content decreased by 12.1%.

[0098] The preparation method of the nanoscale water shutoff agent XSYD-1 used in the preflush is as follows: first, 5 parts by weight of white oil is added with 30 parts of a copolymer monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acid-based acetamide and alkyl succinate sulfonate, and stirred uniformly, and then 10 parts by weight of a composite emulsifier composed of equal mass ratio of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether is added, to prepare an oil phase;

[0099] Then, 20 parts by weight of a composite monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone and ethylenediaminetetraacetic acid is weighed and dissolved in 20 parts of deionized water, and then 0.2 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2 parts by weight of rhamnolipid and 2 parts by weight of phosphatidyl ethanolamine are sequentially added, and mixed and stirred uniformly to prepare an aqueous phase;

[0100] Then, the oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and then the aqueous phase is slowly added for emulsification, and stirring is performed during the addition, and the emulsification time is 0.5 hours.

[0101] Then, after the emulsification is completed, the reaction kettle is heated to 30°C, and nitrogen is introduced for 0.5 hours to remove oxygen.

[0102] After being heated to 60°C, 0.02 parts by weight of an azobisisobutyronitrile initiator is added to initiate the polymerization reaction, and the temperature is maintained for 3 hours.

[0103] Finally, after the solution is cooled to room temperature, the nanoscale water shutoff agent is obtained by centrifugation, specifically, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 8000 rpm for 15 minutes.

[0104] As shown in Figure 2 , the original size of the nanoscale water shutoff agent micelle prepared is 302 nm.

[0105] The detection results are shown in Table 1.

[0106] Table 1 Test results of the nanoscale water shutoff agent XSYD-1 of Example 1

[0107] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥18 30.2 3 Density, g / cm 3 (25°C) 0.85-1.1 1.02 4 Gel particle original size (nm) 300±20 302

[0108] The preparation method of the microscale water shutoff agent XSYD-2 used in the main body plug is different from that of the nanoscale water shutoff agent XSYD-1 in that, after the solution is cooled to room temperature, the nanoscale water shutoff agent is obtained by centrifugation, specifically, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 3000 rpm for 10 minutes, and the morphology of the microscale water shutoff agent XSYD-2 is as shown in Figure 3The test data is shown in Table 2.

[0109] Table 2 Test results of micrometer-sized water shutoff agent XSYD-2 of Example 1

[0110] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥26 58.6 3 Density, g / cm 3 (25 °C) 0.92-1.15 1.08 4 Gel particle original size (μm) 250±30 265

[0111] The preparation method of the selective gel composite water shutoff agent XSYNJ-3 used in the post-plug is as follows: 0.6 parts by weight of modified polyacrylamide, 0.6 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide and 0.03 parts by weight of a stabilizer of N-vinylpyrrolidone are mixed with 95 parts by weight of deionized water to form a solution, which is uniformly stirred and allowed to react for 1 hour, and then the product is obtained. The gelation property and stability evaluation is shown in Table 3. Figure 4 and Figure 5 The test conditions are as follows: Cpoly: 1200 mg / l, Ccross: 60 mg / l, salinity 12 x 10 4 The gelation property test results show that the gelation speed of the system is accelerated and the gelation time is shortened with the increase of temperature, but the system can still maintain a relatively long gelation time at 90°C. The long-term stability of the weak gel is an important indicator for evaluating its performance. The viscosity retention rate of the weak gel is still above 90% at 90 days according to the experimental temperature of 90°C.

[0112] The preparation method of the high-strength thermosetting resin system XSYFK-4 used in the sealing plug is as follows: 100 parts of micro-swelling early-strength Portland cement, 300 parts of high-strength thermosetting resin, 30 parts of phthalic anhydride, 2 parts of modified cellulose CMC, 1 part of trisodium citrate, 0.5 part of defoaming agent and 35 parts of water are uniformly mixed to obtain the product, with the weight of the micro-swelling early-strength Portland cement as the basis; the defoaming agent is composed of 40% silicone oil, 30% sodium tetroxide and 30% hydrophobic silicon dioxide, and the sum of the mass percentages of the above components is 100%; the micro-swelling early-strength Portland cement is composed of 96% G-grade cement, 1.5% expanding agent F17A-1, 2.0% early-strength agent GJ-F and 0.5% drag-reducing agent USZ, and the ratio of the cement system to water is 4:10.

[0113] Table 3 Formulation and performance evaluation of high-strength thermosetting resin system XSYFK-4

[0114] Item 24h compressive strength (MPa) 24h cementation strength (MPa) Permeability (mD) Data 39.7 3.36 0

[0115] Table 4 Settlement stability of high-strength thermosetting resin system XSYFK-4

[0116] Measurement position Upper part Middle part Lower part Density (g / cm 3 )]]> 1.86 1.86 1.86

[0117] The preparation method of the weak gel system XSYDT-5 used in the displacement slug is as follows: the preparation method of the weak gel system XSYDT-5 is the same as that of the micro-scale swelling water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is 5 times that in the micro-scale swelling water plugging agent XSYD-2, and the concentration is only 20% of that of the micro-scale swelling water plugging agent XSYD-2.

[0118] Example 2

[0119] Water plugging operation of L139-X oil well

[0120] Firstly, the required slug amount is calculated according to the formation pressure coefficient and the well structure of the L139-X well; then, five slugs are prepared; finally, the water plugging operation is carried out. The specific operation steps are as follows:

[0121] 1) Preparation work: 50m 3 large tanks (1 for collecting residual liquid), 30m 3 large tank, the rear end of all tanks must be padded, and the tanks must be cleaned. High-pressure water hose, joints and elbows are complete and in good condition (the strength test pressure is required to be 25.0MPa). Prepare one Φ73mm oblique tip, one Φ118mmx1.5m through well gauge, one GX-T140 scraper, 2000m of Φ73mm external thickening oil pipe, one KQ65 / 70 type fracturing wellhead (the gate is required to be complete and in good condition), one K344-114 packer, one 5 1 / 2" hydraulic anchor, one Φ24mm straight nozzle, and several short joints. Before construction, prepare one 700 type pump truck for water supply and one liquid preparation funnel. Common tools and fire fighting equipment are prepared in accordance with the normal construction needs. Labor protection tools (rubber gloves, gas mask, goggles, mask, towel, etc.) are complete.

[0122] 2) Pipe string lifting: lift out the oil pipe rod and accessories, and clean with hot steam. Replace unqualified oil pipes.

[0123] 3) Well passing and well washing: pass the well with Φ118mmx1.5m through well gauge to the artificial well bottom, and wash the well with 30m 3 of well washing fluid at a flow rate of 500L / min. The inlet and outlet water colors of the well washing fluid are consistent, and the sand face or artificial well bottom is explored again. (If resistance is encountered during well passing, the wellbore is treated first, and then the well passing is continued.)

[0124] 4) Casing pressure test: test the casing above the perforation section with the test pressure drilling tool. The water pressure test is 25MPa, and the pressure drop is less than 0.5MPa for 30 minutes, which is qualified.

[0125] 5) Water plugging construction preparation: down the water plugging tool, seat the wellhead, connect the ground blowout pipeline. (The tool into the well time before construction should not exceed 24 hours, accurate measurement of the pipe string is required to ensure the accuracy of the tool position.) KQ65 / 70 type wellhead is used for water plugging construction.

[0126] 6) Water plugging pump injection: close the casing gate, use the tubing positive displacement method, pump the first prepad slug (nanometer water plugging agent XSYD-1), displacement 900 L / min, pressure less than 25 MPa, liquid volume 140 cubic meters. Then continue to use the tubing positive displacement method, pump the second main slug (micron expanded water plugging agent XSYD-2), displacement 800 L / min, pressure less than 25 MPa, liquid volume 200 cubic meters. Then, continue to use the tubing positive displacement method, pump the third postpad slug (selective gel composite water plugging agent XSYNJ-3), displacement 800 L / min, pressure less than 25 MPa, liquid volume 260 cubic meters. Then continue to use the tubing positive displacement method, pump the fourth sealing slug (high-strength thermosetting resin system XSYFK-4), displacement 550 L / min, pressure less than 25 MPa, liquid volume 5 cubic meters, ensure that the pressure gradually increases, after stopping the pump, the pressure drop is less than 3 MPa. Then continue to use the tubing positive displacement method, pump the fifth displacement slug (weak gel system XSYDT-5), displacement 500 L / min, pressure less than 25 MPa, liquid volume 10 cubic meters, ensure that the wellbore is completely filled with weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is squeezed into the formation.

[0127] 7) Wait for the pressure to start and stop above 20 MPa, shut in and wait for 72 hours. During the shut-in and waiting period, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water injection before construction.

[0128] 8) After the water plugging measures are completed, shut in and wait for 72 hours, then control the blowout, according to the pressure drop: control the blowout in four stages: the first stage uses a 4mm choke to blowout until the wellhead pressure is less than 5MPa; the second stage uses an 8mm choke to blowout until the wellhead pressure is less than 3MPa; the third stage uses a 12mm choke to blowout until the wellhead pressure is less than 1MPa; the fourth stage: completely open the wellhead gate for open blowout, accurately measure the liquid volume. Sample and test every shift, complete the production report, report the production results in time. According to the liquid discharge, decide the water plugging and fracturing construction.

[0129] (9) Test well effect: L139-X well before water plugging and fracturing, daily fluid production 4.24m 3 , daily oil production 0t, water content 100%; after water plugging test, fluid production 3.53m 3 , daily oil production 2.3t, water content 39.5%; daily production increase 2.3 tons, water content decrease 60.5%.

[0130] The preparation method of the nanoscale water plugging agent XSYD-1 used in the pre-slug is as follows: first, 8 parts by weight of white oil is added with 40 parts of a copolymer monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide, and alkyl succinate sulfonate, and stirred uniformly, and then 14 parts by weight of a composite emulsifier composed of equal mass ratio of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether is added to prepare an oil phase;

[0131] Then, 26 parts by weight of a composite monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid is weighed and dissolved in 26 parts of deionized water, and then 0.3 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 3 parts by weight of rhamnolipid, and 3 parts by weight of phosphatidyl ethanolamine are sequentially added and mixed and stirred uniformly to prepare an aqueous phase;

[0132] Then, the oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and then the aqueous phase is slowly added for emulsification, and stirring is performed during the addition, and the emulsification time is 1 hour.

[0133] Then, after the emulsification is completed, the reaction kettle is heated to 30°C, and nitrogen is introduced for 1 hour to remove oxygen.

[0134] After being heated to 60°C, 0.02 parts by weight of an azobisdimethyl isopentyl cyanide initiator is added to initiate the polymerization reaction, and the temperature is maintained for 3 hours.

[0135] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation, specifically: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 6000 rpm for 10 minutes.

[0136] The original size of the nanoscale water plugging agent micelles prepared is 314 nm.

[0137] The detection results are shown in Table 5.

[0138] Table 5 Test results of nanoscale water plugging agent XSYD-1 of Example 2

[0139] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥18 35.8 3 Density, g / cm 3 (25°C) 0.85-1.1 1.06 4 Gel particle original size (nm) 300±20 314

[0140] The preparation method of the microscale water plugging agent XSYD-2 used in the main slug is different from that of the nanoscale water plugging agent XSYD-1 in that, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation, specifically: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 2500 rpm for 9 minutes.

[0141] Table 5 Test results of micron-sized water shutoff agent XSYD-2 of Example 2

[0142] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥26 60.1 3 Density, g / cm 3 (25°C) 0.92-1.15 1.05 4 Gel particle original size (μm) 250±30 255

[0143] The preparation method of the selective gel composite water shutoff agent XSYNJ-3 used in the post-plug, which comprises mixing 1.0 parts by weight of modified polyacrylamide, 1.0 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide and 0.04 parts by weight of a stabilizer of N-vinylpyrrolidone with 96 parts by weight of deionized water into a solution, uniformly stirring, and obtaining after 1 hour of sufficient reaction. 4 The gelation test results show that, as the temperature increases, the gelation speed of the system increases and the gelation time becomes shorter, but the system can still maintain a relatively long gelation time at 90℃. The long-term stability of the weak gel is an important indicator for evaluating its performance. According to the experimental temperature of 90℃, the viscosity retention rate of the weak gel is still above 90% after 90 days.

[0144] The preparation method of the high-strength thermosetting resin system XSYFK-4 used in the sealing plug, which comprises mixing 100 parts by weight of micro-swelling early-strength Portland cement, 300 parts of high-strength thermosetting resin, 35 parts of phthalic anhydride, 2.5 parts of modified cellulose CMC, 5 parts of trisodium citrate, 0.8 parts of defoaming agent and 50 parts of water uniformly, wherein the defoaming agent is composed of 50% silicone oil, 25% sodium hydroxide and 25% hydrophobic silicon dioxide by weight percentage, and the total mass percentage of the above components is 100%; the micro-swelling early-strength Portland cement is composed of 96.7% G-grade cement, 1.2% expanding agent F17A-1, 1.8% early-strength agent GJ-F and 0.3% drag-reducing agent USZ by weight percentage, and the ratio of the cement system to water is 4:10.

[0145] The preparation method of the weak gel system XSYDT-5 used in the displacement plug, which is the same as that of the micron-sized swelling water shutoff agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is 5 times that in the micron-sized swelling water shutoff agent XSYD-2, and the concentration is only 20% of that in the micron-sized swelling water shutoff agent XSYD-2.

[0146] Example 3

[0147] L148-× oil well water shutoff operation

[0148] First, according to the formation pressure coefficient and well structure of L148-X well, the slug dosage required is calculated; then, five slug liquid is prepared; finally, water plugging operation is carried out. The specific operation steps are as follows:

[0149] 1) Preparation: 50m 3 large tank 15 (1 for collecting residual liquid), 30m 3 large tank 1, all tanks must be padded at the rear end, and the tank must be cleaned. High-pressure water hose, joint, elbow are complete and good (require strength test pressure 25.0MPa). Prepare Φ73mm oblique tip one, Φ118mm×1.5m through well gauge one, GX-T140 scraper one, Φ73mm external thickening oil pipe 2000m, KQ65 / 70 type fracturing wellhead (require complete and good gate), K344-114 packer 1, 5 1 / 2" hydraulic anchor 1, Φ24mm straight nozzle 1, short section several. Before construction, prepare 700 type pump truck 1 for water, and prepare a liquid distribution funnel. Common tools and fire fighting equipment are prepared according to normal construction needs. Labor protection tools (rubber gloves, gas mask, goggles, mask, towel, etc.) are complete.

[0150] 2) Pipe string: the original well tubing rod and accessories are pulled out, hot steam is washed clean, and unqualified oil pipe is replaced.

[0151] 3) Well passing and well washing: pass the well with Φ118mm×1.5m through well gauge to the artificial well bottom, wash the well with 30m 3 of washing fluid, the washing displacement is 500L / min, the inlet and outlet water of washing fluid is consistent, and the sand surface or artificial well bottom is explored again. (If resistance is encountered during well passing, the wellbore is treated first, and then the well passing is continued).

[0152] 4) Casing pressure test: the casing above the perforation section is tested by lowering the pressure test drill pipe, and the water pressure test is 25MPa. The pressure drop is less than 0.5MPa for 30 minutes, which is qualified.

[0153] 5) Water plugging construction preparation: lower the water plugging drill pipe, seat the wellhead, and connect the ground blowout pipeline. (The tool in the well before construction should not exceed 24 hours, and the pipe string should be accurately measured to ensure accurate tool position). KQ65 / 70 type wellhead is used for water plugging construction.

[0154] 6) Water plugging pump injection: close the casing gate, adopt the oil pipe positive extrusion mode, pump in the first segment pre-plug (nanometer water plugging agent XSYD-1), displacement 860 L / min, pressure less than 25 MPa, liquid volume 120 m3. Then continue to adopt the oil pipe positive extrusion mode, pump in the second segment main plug (micron expanded water plugging agent XSYD-2), displacement 830 L / min, pressure less than 25 MPa, liquid volume 120 m3. Then, continue to adopt the oil pipe positive extrusion mode, pump in the third segment post-plug (selective gel composite water plugging agent XSYNJ-3), displacement 750 L / min, pressure less than 25 MPa, liquid volume 220 m3. Then continue to adopt the oil pipe positive extrusion mode, pump in the fourth segment sealing plug (high-strength thermosetting resin system XSYFK-4), displacement 550 L / min, pressure less than 25 MPa, liquid volume 3 m3, ensure that the pressure gradually increases, after stopping the pump, the pressure drop is less than 3 MPa. Then continue to adopt the oil pipe positive extrusion mode, pump in the fifth segment displacement plug (weak gel system XSYDT-5), displacement 500 L / min, pressure less than 25 MPa, liquid volume 10 m3, ensure that the wellbore is filled with weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is extruded into the formation.

[0155] 7) Wait for the pressure to start and stop above 20 MPa, shut in and wait for 72 hours. During the shut-in and waiting period, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water injection before construction.

[0156] 8) After the water plugging measure is completed, shut in and wait for 72 hours, then control the blowout, according to the pressure drop: control the blowout in four stages: the first stage uses a 4 mm choke to blow out until the wellhead pressure is less than 5 MPa; the second stage uses an 8 mm choke to blow out until the wellhead pressure is less than 3 MPa; the third stage uses a 12 mm choke to blow out until the wellhead pressure is less than 1 MPa; the fourth stage: completely open the wellhead gate for open blowout, accurately measure the liquid volume. Sample and test every shift, complete the production situation shift report, and report the production results in a timely manner. Determine the water plugging and fracturing construction according to the liquid discharge.

[0157] (9) Test well effect: L148-X well before water plugging and fracturing, daily fluid production 5.36 m 3 , daily oil production 0 t, water content 100%; after water plugging test, fluid production 3.86 m 3 , daily oil production 1.6 t, water content 65.5%; daily production increase 1.6 tons, water content decrease 34.5%.

[0158] The preparation method of the nanoscale water shutoff agent XSYD-1 used in the preflush is as follows: first, 6 parts by weight of white oil is added with 35 parts of a copolymer monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide and alkyl succinate sulfonate, and stirred uniformly, then 12 parts by weight of a composite emulsifier composed of equal mass ratio of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether is added, and an oil phase is prepared;

[0159] Then, 22 parts by weight of a composite monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid is weighed and dissolved in 22 parts of deionized water, then 0.25 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2.5 parts by weight of rhamnolipid and 2.5 parts by weight of phosphatidyl ethanolamine are sequentially added, and stirred and mixed uniformly to prepare an aqueous phase;

[0160] Then, the oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and the aqueous phase is slowly added for emulsification, and stirring is performed during the addition, and the emulsification time is 0.75 hours.

[0161] Then, after the emulsification is completed, the reaction kettle is heated to 30°C, and nitrogen is introduced for 0.5 hours to remove oxygen.

[0162] After being heated to 60°C, 0.025 parts by weight of an initiator composed of equal volume ratio of azobisisobutyronitrile and azobisisoheptyl nitrile is added to initiate the polymerization reaction, and the temperature is maintained for 2.5 hours.

[0163] Finally, after the solution is cooled to room temperature, the nanoscale water shutoff agent is obtained by centrifugation, and the step 6 is specifically as follows: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol, the rotation speed is 7000 rpm, and the centrifugation time is 12 minutes.

[0164] The original size of the nanoscale water shutoff agent micelles prepared is 308 nm.

[0165] The detection results are shown in Table 5.

[0166] Table 5 Test results of the nanoscale water shutoff agent XSYD-1 of Example 3

[0167] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥18 36.2 3 Density, g / cm 3 (25°C) 0.85-1.1 1.03 4 Gel particle original size (nm) 300±20 310

[0168] The preparation method of the microscale water shutoff agent XSYD-2 used in the main body plug is different from that of the nanoscale water shutoff agent XSYD-1, and the nanoscale water shutoff agent is obtained by centrifugation after the solution is cooled to room temperature, and the step is specifically as follows: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol, the rotation speed is 3000 rpm, and the centrifugation time is 10 minutes.

[0169] Table 6 Test results of micron-sized water shutoff agent XSYD-2 of Example 1

[0170] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥26 39.2 3 Density, g / cm 3 (25°C) 0.92-1.15 0.98 4 Gel particle original size (μm) 250±30 248

[0171] The preparation method of the selective gel composite water shutoff agent XSYNJ-3 used in the post-plug, which comprises mixing 1.2 parts by weight of modified polyacrylamide, 1.5 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide and 0.05 parts by weight of a stabilizer of N-vinylpyrrolidone with 98 parts by weight of deionized water into a solution, uniformly stirring, and obtaining after 1 hour of sufficient reaction. 4 The gelation property test results show that as the temperature increases, the gelation speed of the system increases and the gelation time becomes shorter, but the system can still maintain a relatively long gelation time at 90°C. The long-term stability of the weak gel is an important indicator for evaluating its performance. According to the experimental temperature of 90°C, the viscosity retention rate of the weak gel is still above 90% after 90 days.

[0172] The preparation method of the high-strength thermosetting resin system XSYFK-4 used in the sealing plug, which comprises mixing 100 parts by weight of micro-swelling early-strength Portland cement, 300 parts of high-strength thermosetting resin, 48 parts of phthalic anhydride, 3 parts of modified cellulose CMC, 10 parts of trisodium citrate, 1 part of defoaming agent and 120 parts of water uniformly, and obtaining; wherein the defoaming agent is composed of 45% silicone oil, 27.5% sodium hydroxide, 27.5% hydrophobic silicon dioxide by weight percentage, and the sum of the mass percentages of the above components is 100%; the micro-swelling early-strength Portland cement is composed of 96.6% G-grade cement, 1.2% expanding agent F17A-1, 1.8% early-strength agent GJ-F and 0.4% drag-reducing agent USZ by weight percentage, and the ratio of the cement system to water is 4:10.

[0173] The preparation method of the weak gel system XSYDT-5 used in the displacement plug, which is different from the micron-sized swelling water shutoff agent XSYD-2 in the amount of deionized water, and the preparation method is the same as that of the micron-sized swelling water shutoff agent XSYD-2, that is, the amount of deionized water in the weak gel system XSYDT-5 is increased to 5 times that of the micron-sized swelling water shutoff agent XSYD-2, and the concentration is only 20% of that of the micron-sized swelling water shutoff agent XSYD-2.

[0174] Example 4

[0175] L146-× oil well water shutoff operation

[0176] First, according to the formation pressure coefficient and well structure of L146-X well, the slug amount required is calculated; then, five slug liquid is prepared; finally, water plugging operation is carried out. The specific operation steps are as follows:

[0177] 1) Preparation: 50m 3 large tank 15 (1 for collecting residual liquid), 30m 3 large tank 1, all tanks must be padded at the rear end, and the tank must be cleaned. High-pressure water hose, joint, elbow are complete and good (require strength test pressure 25.0MPa). Prepare Φ73mm oblique tip one, Φ118mm×1.5m through well gauge one, GX-T140 scraper one, Φ73mm external thickening oil pipe 2000m, KQ65 / 70 type fracturing wellhead (require complete and good gate), K344-114 packer 1, 5 1 / 2" hydraulic anchor 1, Φ24mm straight nozzle 1, short section several. Before construction, prepare 700 type pump truck 1 for water, liquid distribution funnel one. Common tools and fire fighting equipment are prepared according to normal construction needs. Labor protection tools (rubber gloves, gas mask, goggles, mask, towel, etc.) are complete.

[0178] 2) Pipe string: the original oil pipe rod and accessories are pulled out, hot steam is washed clean, and unqualified oil pipe is replaced.

[0179] 3) Through well, well washing: down Φ118mm×1.5m through well gauge to the artificial well bottom, 30m 3 of washing fluid, washing displacement 500L / min, the inlet and outlet water of washing fluid is consistent, and the sand surface or artificial well bottom is explored again. (If resistance is encountered during through well, the wellbore is treated first, and then the through well is continued.)

[0180] 4) Casing pressure test: down the pressure test drill string to test the casing above the perforation section, water pressure test 25MPa, 30 minutes pressure drop less than 0.5MPa is qualified.

[0181] 5) Water plugging construction preparation: down the water plugging drill string, seat the wellhead, and connect the ground blowout pipeline. (The tool into the well time before construction should not exceed 24 hours, and the pipe string should be accurately measured to ensure accurate tool position.) KQ65 / 70 type wellhead is used for water plugging construction.

[0182] 6) Water plugging pump injection: close the casing gate, adopt the oil pipe positive extrusion mode, pump the first segment pre-plug (nanometer water plugging agent XSYD-1), displacement 820 L / min, pressure less than 25 MPa, liquid volume 140 cubic meters. Then continue to adopt the oil pipe positive extrusion mode, pump the second segment main plug (micron expansion type water plugging agent XSYD-2), displacement 800 L / min, pressure less than 25 MPa, liquid volume 140 cubic meters. Then, continue to adopt the oil pipe positive extrusion mode, pump the third segment post-plug (selective gel type composite water plugging agent XSYNJ-3), displacement 700 L / min, pressure less than 25 MPa, liquid volume 200 cubic meters. Then continue to adopt the oil pipe positive extrusion mode, pump the fourth segment sealing plug (high-strength thermosetting resin system XSYFK-4), displacement 500 L / min, pressure less than 25 MPa, liquid volume 3 cubic meters, ensure that the pressure gradually increases, after stopping the pump, the pressure drop is less than 3 MPa. Then continue to adopt the oil pipe positive extrusion mode, pump the fifth segment displacement plug (weak gel system XSYDT-5), displacement 560 L / min, pressure less than 25 MPa, liquid volume 8 cubic meters, ensure that the wellbore is filled with weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is extruded into the formation.

[0183] 7) Wait for the pressure to start and stop above 20 MPa, shut in and wait for 72 hours. During the shut-in and waiting period, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water injection before construction.

[0184] 8) After the water plugging measure is completed, shut in and wait for 72 hours, then control the blowout, according to the pressure drop: control the blowout in four stages: the first stage uses a 4mm nozzle to blowout until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to blowout until the wellhead pressure is less than 3MPa; the third stage uses a 12mm nozzle to blowout until the wellhead pressure is less than 1MPa; the fourth stage: completely open the wellhead gate for open blowout, accurately measure the liquid volume. Sample and test every shift, complete the production situation shift report, and report the production results in a timely manner. Determine the water plugging and fracturing construction according to the liquid discharge.

[0185] (9) Test well effect: L146-X well before water plugging and fracturing, daily fluid production 6.87m 3 , daily oil production 0.6t, water content 95.2%; after water plugging test, fluid production 4.53m 3 , daily oil production 2.8t, water content 39.5%; daily production increase 2.2 tons, water content decrease 55.7%.

[0186] The preparation method of the nanoscale water plugging agent XSYD-1 used in the pre-plug is as follows: first, 7 parts by weight of white oil is added with 36 parts of a copolymer monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide, and alkyl succinate sulfonate, and stirred uniformly, and then 13 parts by weight of a composite emulsifier composed of equal mass ratio of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether is added to prepare an oil phase;

[0187] Then, 23 parts by weight of a composite monomer composed of equal mass ratio of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid is dissolved in 23 parts of deionized water, and then 0.25 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 2.5 parts by weight of rhamnolipid, and 2.5 parts by weight of phosphatidyl ethanolamine are sequentially added and mixed and stirred uniformly to prepare an aqueous phase;

[0188] Then, the oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and then the aqueous phase is slowly added for emulsification, and the emulsification is stirred for 0.75 hours.

[0189] Then, after the emulsification is completed, the reaction kettle is heated to 30°C, and nitrogen is introduced for 0.75 hours to remove oxygen.

[0190] After being heated to 60°C, 0.025 parts by weight of an azobisdimethyl isopentylnitrile initiator is added to initiate the polymerization reaction, and the temperature is maintained for 2.5 hours.

[0191] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation, specifically: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 6500 rpm for 15 minutes.

[0192] The original size of the nanoscale water plugging agent micelles prepared is 309 nm.

[0193] The detection results are shown in Table 7.

[0194] Table 7 Test results of nanoscale water plugging agent XSYD-1 of Example 4

[0195] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥18 33.5 3 Density, g / cm 3 (25°C) 0.85-1.1 1.05 4 Gel particle original size (nm) 300±20 309

[0196] The preparation method of the microscale water plugging agent XSYD-2 used in the main plug is different from that of the nanoscale water plugging agent XSYD-1 in that after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation, specifically: after being cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 3000 rpm for 8 minutes.

[0197] Table 8 Test results of micron-sized water shutoff agent XSYD-2 of Example 1

[0198] No. Item Index Test result 1 Appearance White or brownish yellow emulsion Pass 2 Separable solid content, % ≥26 54.3 3 Density, g / cm 3 (25°C) 0.92-1.15 1.04 4 Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (nm) No. Item Index Test result Appearance White or brownish yellow emulsion Pass Separable solid content, % Gel particle original size (μm) No. Item Index Test result Appearance White or brownish yellow 250±30 274

[0199] The preparation method of the selective gel composite water shutoff agent XSYNJ-3 used in the post-plug, which is prepared by mixing 1.2 parts by weight of modified polyacrylamide, 1.5 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, and 0.05 parts by weight of a stabilizer of N-vinylpyrrolidone, with 97 parts by weight of deionized water into a solution, stirring uniformly, and obtaining after 1 hour of sufficient reaction. 4 The gelation test results show that as the temperature increases, the gelation speed of the system increases and the gelation time becomes shorter, but the system can still maintain a relatively long gelation time at 90°C. The long-term stability of the weak gel is an important indicator for evaluating its performance. According to the experimental temperature of 90°C, the viscosity retention rate of the weak gel is still above 90% after 90 days.

[0200] The preparation method of the high-strength thermosetting resin system XSYFK-4 used in the sealing plug, which is prepared by mixing 100 parts of micro-swelling early-strength Portland cement, 300 parts of high-strength thermosetting resin, 47 parts of phthalic anhydride, 3 parts of modified cellulose CMC, 10 parts of trisodium citrate, 1 part of defoaming agent, and 100 parts of water uniformly based on the weight of 100 parts of micro-swelling early-strength Portland cement; wherein the defoaming agent is composed of 45% silicone oil, 27.5% sodium hydroxide, and 27.5% hydrophobic silicon dioxide by weight percentage, and the sum of the mass percentages of the above components is 100%; the micro-swelling early-strength Portland cement is composed of 96.6% G-grade cement, 1.2% expanding agent F17A-1, 1.8% early-strength agent GJ-F, and 0.4% drag-reducing agent USZ by weight percentage, and the ratio of the cement system to water is 4:10.

[0201] The preparation method of the weak gel system XSYDT-5 used in the displacement plug, which is the same as that of the micron-sized swelling water shutoff agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is 5 times that in the micron-sized swelling water shutoff agent XSYD-2, and the concentration is only 20% of that in the micron-sized swelling water shutoff agent XSYD-2.

Claims

1. A composite water shutoff agent system, characterized in that, The nanoscale water plugging agent XSYD-1, the microscale water plugging agent XSYD-2, the selective gel composite water plugging agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4 and the weak gel system XSYDT-5; the nanoscale water plugging agent XSYD-1, the microscale water plugging agent XSYD-2, the selective gel composite water plugging agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4 and the weak gel system XSYDT-5 correspond to five slugs in the order of entering the well; the five slugs in the order of entering the well are: a preflush slug, a main slug, a postflush slug, a sealing slug and a displacement slug; The nanoscale water plugging agent XSYD-1 comprises the following components by weight: 5-8 parts of white oil, 30-40 parts of a copolymer monomer, 10-14 parts of a composite emulsifier, 20-26 parts of a composite monomer, 20-26 parts of deionized water, 0.2-0.3 parts of a crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidyl ethanolamine and 0.02-0.03 parts of an initiator; The copolymer monomer is composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide and alkyl succinate sulfonate in any ratio; the composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio; the composite monomer is composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid in any ratio; the crosslinking agent is N,N'-methylene bisacrylamide; and the initiator is azobisisobutyronitrile or azobisisoheptyl nitrile, or a mixture of azobisisobutyronitrile and azobisisoheptyl nitrile, and the volume ratio of the two in the mixture is 1:1; The preparation method of the nanoscale water plugging agent XSYD-1 specifically comprises the following steps: Step 1, the copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, alkyl sulfonic acid-based acetamide and alkyl succinate sulfonate in any ratio is added into white oil, stirred uniformly, and then the composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio is added to prepare an oil phase; Step 2, the composite monomer composed of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid in any ratio is weighed, dissolved in deionized water, and then the crosslinking agent N,N'-methylene bisacrylamide, rhamnolipid and phosphatidyl ethanolamine are sequentially added and stirred uniformly to prepare an aqueous phase; Step 3, the oil phase is placed in a reaction kettle, the solution is stirred uniformly by a magnetic stirring needle, and then the aqueous phase is slowly added for emulsification, while stirring, the stirring speed is 150 rpm-200 rpm, and the emulsification time is 0.5-1 hour; Step 4, after the emulsification is completed, the reaction kettle is heated to 30℃, and nitrogen is introduced for 0.5-1 hour to remove oxygen; Step 5, after being heated to 60℃, the initiator azobisisobutyronitrile or azobisisoheptyl nitrile is added to initiate the polymerization reaction, and the temperature is kept for 2-3 hours; Step 6, the nanoscale water plugging agent is obtained by centrifugation; specifically, after being cooled to room temperature, the liquid after polymerization obtained in step 5 is centrifuged with anhydrous ethanol at a speed of 6000 rpm-8000 rpm for 10-15 minutes; The raw material components and the ratio of the microscale water plugging agent XSYD-2 are the same as those of the nanoscale water plugging agent XSYD-1; the preparation method of the microscale water plugging agent XSYD-2 is the same as steps 1-5 of the preparation method of the nanoscale water plugging agent XSYD-1, and the difference lies in step 6; step 6 of the preparation method of the microscale water plugging agent XSYD-2 is: after being cooled to room temperature, the liquid after polymerization obtained in step 5 is centrifuged with anhydrous ethanol, and the speed is adjusted to 2000 rpm-3000 rpm, and the centrifugation time is 8-10 minutes; The selective gel composite water plugging agent XSYNJ-3 comprises the following components in parts by weight: 0.6-1.2 parts by weight of modified polyacrylamide, 0.6-1.5 parts by weight of a crosslinking agent of N,N'-methylenebisacrylamide, 0.03-0.05 parts by weight of a stabilizer of N-vinylpyrrolidone, and 95-98 parts by weight of deionized water; The high-strength thermosetting resin system XSYFK-4 has the following formula: based on 100 parts by weight of micro-swelling early-strength Portland cement, 100 parts of micro-swelling early-strength Portland cement, 300 parts of high-strength thermosetting resin, 30-48 parts of curing agent, 2-3 parts of fluid loss additive, 0-10 parts of setting regulator, 0.5-1 part of defoaming agent, and 35-120 parts of water; In the formula of the high-strength thermosetting resin system XSYFK-4: (1) The micro-swelling early-strength Portland cement is composed of the following components in percentage by weight: 96-97% G-grade cement, 1.2-1.5% expanding agent, 1.8-2.0% early-strength agent, and 0.3-0.5% drag-reducing agent, and the sum of the mass percentages of the above components is 100%; (2) The chemical formula of the high-strength thermosetting resin is as follows: (3) The curing agent is an acid anhydride; (4) The fluid loss additive is modified cellulose CMC; (5) The setting regulator is trisodium citrate; (6) The defoaming agent is composed of the following components in percentage by weight: 40%-50% silicone oil, 20%-30% sodium tetraborate, and 20%-30% hydrophobic silicon dioxide, and the sum of the mass percentages of the above components is 100%; The weak gel system XSYDT-5 comprises the following components in parts by weight: 5-8 parts of white oil, 30-40 parts of a copolymer monomer, 10-14 parts of a composite emulsifier, 20-26 parts of a composite monomer, 100-130 parts of deionized water, 0.2-0.3 parts of a crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidyl ethanolamine, and 0.02-0.03 parts of an initiator. The preparation method of the weak gel system XSYDT-5 is as follows: the preparation method of the weak gel system XSYDT-5 is the same as that of the micron-sized swelling water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is 5 times that in the micron-sized swelling water plugging agent XSYD-2.

2. A method of water shutoff with multiple packers, characterized in that, The composite water plugging agent system of claim 1 is implemented according to the following steps: starting the pipe column, passing through the well, washing the well, testing the casing pressure and performing the multi-packer water plugging operation.

3. The method of water shutoff with multiple plugs of claim 2, wherein, The multi-packer water plugging operation is implemented according to the following steps: First step, lower the water plugging drilling tool, seat the wellhead, and connect the ground blowout line; Second step, close the casing gate, use the tubing positive displacement method, pump the nanoscale water plugging agent XSYD-1 used for the first pre-pad, the displacement is 800L / min-1000L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; Third step, then still use the tubing positive displacement method, pump the micron-sized swelling water plugging agent XSYD-2 used for the second main pad, the displacement is 700L / min-1200L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; Fourth step, then continue to use the tubing positive displacement method, pump the selective gel composite water plugging agent XSYNJ-3 used for the third post-pad, the displacement is 700L / min-1200L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition; Fifth step, then continue to use the tubing positive displacement method, pump the high-strength thermosetting resin system XSYFK-4 used for the fourth sealing pad, the displacement is 500L / min-1000L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition, and the intermittent displacement method is used to ensure that the pressure gradually increases, and the pressure drop is less than 3MPa after the pump is stopped; In the fifth step, the intermittent displacement sealing method is used, that is, instead of using this displacement completion method, the displacement is performed multiple times, and the displacement is performed every 10min-20min, and every time interval is 10min-15min, and after the high-strength thermosetting resin system XSYFK-4 is cured and the pressure is raised, the displacement pressure is continuously increased, and finally the designed amount is displaced; Sixth step, then continue to use the tubing positive displacement method, pump the weak gel system XSYDT-5 used for the fifth displacement pad, the displacement is 500L / min-600L / min, the pressure is less than 25MPa, and the liquid amount is designed according to the well condition, and the weak gel system XSYDT-5 is ensured to fill the wellbore, and the excess high-strength thermosetting resin system XSYFK-4 is squeezed into the formation, and the pressure is raised to 20MPa or more, and the well is closed for 72-96 hours for curing. The seventh step, the water plugging measure is ended, the well is closed for 72-96 hours, and the control is conducted after the well is opened. According to the pressure drop, the control is conducted in four stages: the first stage is conducted by using a 4-5 mm nozzle to open the well until the wellhead pressure is less than 5 MPa; the second stage is conducted by using an 8 mm nozzle to open the well until the wellhead pressure is less than 3 MPa; the third stage is conducted by using a 10-12 mm nozzle to open the well until the wellhead pressure is less than 1 MPa; and the fourth stage is conducted by opening the well gate to open the well and accurately measure the discharge liquid volume. The eighth step is fracturing construction, flowback, and pumping according to the geological requirements to complete the well.

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