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

Abstract

The invention discloses a composite water plugging agent system which comprises a nanoscale water plugging agent XSYD-1, a micron-sized water plugging agent XSYD-2, a selective gel type composite water plugging agent XSYNJ-3, a high-strength thermosetting resin system XSYFK-4 and a weak gel system XSYDT-5. The nano-scale water plugging agent XSYD-1, the micron-scale water plugging agent XSYD-2, the selective gel type composite water plugging agent XSYNJ-3, the high-strength thermosetting resin system XSYFK-4 and the weak gel system XSYDT-5 respectively correspond to five slugs according to a well entering sequence; the five slugs are respectively a front slug, a main body slug, a rear slug, a sealing slug and a displacement slug according to a well entering sequence. The system can achieve the purpose of deep plugging of an oil layer, and the water plugging validity period is greatly prolonged. The invention further provides a multi-slug water plugging method.

Description

Technical Field

[0001] The invention belongs to the technical field of oil well water plugging in the process of oil and gas field development, and particularly relates to a composite water plugging agent system and a multi-stage plugging water plugging method. Background Art

[0002] As the development time of oil fields increases, the formation pressure continues to decline. Most oil fields mainly use the "secondary oil recovery" method of water injection development to increase production and crude oil recovery. For an oil field that has been developed by water injection for a long time, due to the horizontal and vertical heterogeneity of the reservoir and the difference in oil and water viscosity, the injected water will inevitably rush and flow along the high permeability zone to the production well, resulting in inefficient or ineffective circulation of the injected water. After decades of intensive exploitation, many oil fields in my country have entered the medium and high water content period. At this time, the underground recoverable reserves are still large, and there are still about 40% of the water injection reserves that have not been used. However, the efficiency of the production and injection measures that were widely used under water injection conditions has become increasingly low, and the situation of "high water content, high input, and low output" has emerged. The technical difficulty is getting greater and greater, the output is decreasing, the water production is greatly increasing, and the economic benefits are poor. At the same time, fracturing, acidification, and high-intensity mining will cause problems such as injected water tongue, edge water intrusion, bottom water cone intrusion, and external water intrusion, which not only affects the recovery of crude oil, but also consumes energy, increases the cost of processing the produced fluid, and causes corrosion of pipelines, thereby increasing the cost of crude oil recovery and causing environmental pollution. Some oil wells may also experience explosive flooding, resulting in the closure of oil wells and a large waste of resources. Therefore, how to effectively block water has become a serious problem faced in oil field development.

[0003] At present, water plugging technology is mainly divided into two categories: mechanical water plugging and chemical water plugging. The so-called mechanical water plugging technology is to use a packer to block the water-producing layer in the wellbore to prevent water from flowing into the well and block the water-producing layer section in the oil well. The water plugging methods are divided into sealing the upper and blocking the lower, sealing the lower and blocking the upper, sealing the middle and mining at both ends, and sealing the two ends and mining in the middle. This technology requires the packer seat to be tightly and accurately sealed, which is the guarantee for the success of mechanical water plugging. The mechanical water plugging method is simple and easy, low cost and effective, but it is not easy to use in oil wells where the lower packer or other reasons cannot separate oil and water. Oil well chemical water plugging is a process technology that injects chemicals into the high permeability water-producing layer section through the oil well to reduce the water phase permeability of the near-well zone, control the output of injected water, bottom water and edge water, and thus increase crude oil production. The chemical method does not require well repair equipment, the operation is economical and convenient, and it is widely used. The chemical agent used in chemical water plugging is called a water plugging agent. At present, there are three main types of water plugging agents, namely polymer gel plugging agents (jelly gel type), water glass calcium chloride precipitation plugging agents (water expanded body type), cement type, etc., but all of them have certain limitations. At the same time, most of the current water plugging agents are of one type, and the water plugging process can only plug one type of pores or cracks, which has problems such as small plugging radius, poor pressure bearing capacity, and short validity period. Summary of the invention

[0004] The first object of the present invention is to provide a composite water plugging agent system, which can effectively plug not only the distal microcracks and pores and the sub-distal slightly larger cracks, but also the front section of the main cracks, large cracks and high permeability channels by adopting a multi-stage plugging water plugging process, so as to achieve the purpose of deep plugging of the oil layer and greatly increase the effective period of water plugging.

[0005] The second object of the present invention is to provide a multi-stage plugging method for water blocking.

[0006] The first technical solution adopted by the present invention is that the composite water plugging agent system includes nano-scale water plugging agent XSYD-1, micron-scale water plugging agent XSYD-2, selective gel composite water plugging agent XSYNJ-3, high-strength thermosetting resin system XSYFK-4 and weak gel system XSYDT-5; the nano-scale water plugging agent XSYD-1, the micron-scale 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 segment plugs according to the order of entering the well; the five segment plugs according to the order of entering the well are: front segment plug, main segment plug, rear segment plug, sealing segment plug and replacement segment plug.

[0007] The present invention is also characterized in that

[0008] Nano-scale water plugging agent XSYD-1 includes the following components in parts by weight: 5 to 8 parts of white oil, 30 to 40 parts of copolymer monomers, 10 to 14 parts of composite emulsifiers, 20 to 26 parts of composite monomers, 20 to 26 parts of deionized water, 0.2 to 0.3 parts of cross-linking agents, 2 to 3 parts of rhamnolipids, 2 to 3 parts of phosphatidylethanolamine, and 0.02 to 0.03 parts of initiators. The copolymer monomer is composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic 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 azobisisoheptanenitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanenitrile, and the volume ratio of the two in the mixture is 1:1;

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

[0010] Step 1, adding a copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in any ratio into white oil, stirring evenly, and then adding a composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare an oil phase; Step 2, weighing a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in any ratio, dissolving it in deionized water, and then adding N,N'-methylenebisacrylamide in turn. The crosslinking agent, rhamnolipid and phosphatidylethanolamine are mixed and stirred evenly to prepare an aqueous phase; step 3, the oil phase is placed in a reaction kettle, the solution is stirred evenly with a magnetic stirring needle, and the aqueous phase is slowly added for emulsification, stirring while adding, the rotation speed is 150rpm-200rpm, and the emulsification time is 0.5 hour-1 hour; step 4, after the emulsification is completed, the reactor is heated to 30°C, and nitrogen is introduced for 0.5 hour-1 hour for deoxygenation; step 5, after the temperature is raised to 60°C, azobisisobutyronitrile or azobisisoheptanenitrile initiator is added to initiate a polymerization reaction, and the temperature is kept for 2 hours-3 hours;

[0011] Step 6, obtaining the nano-scale water plugging agent by centrifugal separation; specifically, after cooling to room temperature, centrifuging the liquid obtained in step 5 after the polymerization reaction with anhydrous ethanol at a speed of 6000rpm-8000rpm and a centrifugal time of 10 minutes-15 minutes.

[0012] The raw material components and proportions of the micron-level water plugging agent XSYD-2 are the same as those of the nano-level water plugging agent XSYD-1; the preparation method of the micron-level water plugging agent XSYD-2 is the same as steps 1 to 5 of the preparation method of the nano-level water plugging agent XSYD-1, and the difference lies in step 6; step 6 of the preparation method of the micron-level water plugging agent XSYD-2 is: after cooling to room temperature, centrifuging the liquid after the polymerization reaction obtained in step 5 with anhydrous ethanol, adjusting the speed to 2000rpm-3000rpm, and the centrifugation time is 8 minutes-10 minutes.

[0013] The selective gel composite water plugging agent XSYNJ-3 includes 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 N,N'-methylenebisacrylamide crosslinking agent, 0.03-0.05 parts by weight of N-vinylpyrrolidone stabilizer, and 95-98 parts by weight of deionized water.

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

[0015] Formula of high-strength thermosetting resin system XSYFK-4:

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

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

[0018]

[0019] (3) The curing agent is 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 by weight: 40%-50% silicone oil, 20%-30% sodium stearate, and 20%-30% hydrophobic silica, and the sum of the weight percentages of the above components is 100%.

[0023] The micron-scale expansion water plugging agent XSYD-2 is diluted to obtain a solution with a concentration of only 20% of the micron-scale expansion water plugging agent XSYD-2, and the solution is the weak gel system XSYDT-5. The weak gel system XSYDT-5 includes the following components by weight: 5 to 8 parts of white oil, 30 to 40 parts of comonomers, 10 to 14 parts of composite emulsifiers, 20 to 26 parts of composite monomers, 100 to 130 parts of deionized water, 0.2 to 0.3 parts of crosslinking agents, 2 to 3 parts of rhamnolipids, 2 to 3 parts of phosphatidylethanolamine, and 0.02 to 0.03 parts of initiators.

[0024] The second technical solution adopted by the present invention is a multi-stage plugging water plugging method, which adopts the above-mentioned composite water plugging agent system and is implemented according to the following steps: pulling up the pipe string, clearing the well, washing the well, casing pressure testing and multi-stage plugging water plugging operations.

[0025] The present invention is also characterized in that

[0026] The multi-stage plugging operation is carried out in the following steps:

[0027] The first step is to lower the water plugging drill bit, set the wellhead, and connect the ground spray line; the second step is to close the casing gate and use the tubing positive squeeze method to pump in the nano-scale water plugging agent XSYD-1 for the first section of the front slug, with a displacement of 800L / min-1000L / min, a pressure of less than 25MPa, and a liquid volume designed according to the well conditions; the third step is to continue to use the tubing positive squeeze method to pump in the micron-scale expansion water plugging agent XSYD-2 for the second section of the main slug, with a displacement of 700L / min-1 200L / min, pressure less than 25MPa, the liquid volume is designed according to the well conditions; the fourth step, continue to use the tubing positive squeeze method to pump in the selective gel composite water plugging agent XSYNJ-3 for the third section rear slug, with a displacement of 700L / min-1200L / min, pressure less than 25MPa, and the liquid volume is designed according to the well conditions; the fifth step, continue to use the tubing positive squeeze method to pump in the high-strength thermosetting resin system XSYFK-4 for the fourth section sealing slug, with a displacement of 500 L / min-1000L / min, pressure is less than 25MPa, the liquid volume is designed according to the well conditions, or intermittent displacement is adopted to ensure that the pressure gradually increases. After stopping the pump, the pressure drop is less than 3Mpa; in the fifth step, the intermittent displacement sealing method is used, that is, the displacement is not completed this time, but multiple displacements are used, and the displacement is replaced every 10min-20min, with an interval of 10min-15min each time. After the high-strength thermosetting resin system XSYFK-4 is solidified and the pressure is raised, the displacement is continuously increased. pressure, and finally replace the designed amount; the sixth step is to continue to use the tubing positive squeeze method to pump in the weak gel system XSYDT-5 used for the fifth section to replace the plug, with a displacement of 500L / min-600L / min and a pressure less than 25MPa. The liquid volume is designed according to the well conditions to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is squeezed into the formation. When the pressure starts to exceed 20MPa, shut in the well and wait for 72-96 hours. The seventh step is to complete the water plugging measures, shut down the well and wait for 72 hours to 96 hours, then control the blowout, depending on the pressure drop: the blowout is divided into four stages: the first stage uses a 4mm-5mm nozzle to blow out until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to blow out until the wellhead pressure is less than 3MPa; the third stage uses a 10mm-12mm nozzle to blow out until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for open release, and accurately measure the amount of discharged liquid; the eighth step is fracturing construction, flowback, and pumping and completion according to geological requirements.

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

[0029] (1) The composite water plugging agent system of the present invention is mainly composed of nanometer-level plugging agents, micrometer-level expansion plugging agents, selective gel plugging agents and high-strength plugging agents. It adopts a multi-stage plugging process, which can not only effectively plug the distal microcracks and pores and the slightly larger cracks at the secondary distal end, but also plug the front section of the main crack, large cracks and high-permeability channels. The multi-stage plug design is from weak to strong, which can effectively plug the end, branch cracks, main cracks, etc., and has a large plugging radius, which can achieve the purpose of deep plugging of the oil layer and greatly improve the effective period of water plugging.

[0030] (2) In the composite water plugging agent system of the present invention, the nano-scale water plugging agent XSYD-1 and the micron-scale swelling water plugging agent XSYD-2 have low initial viscosity, are easy to pump into the formation, have stable performance after swelling, and can effectively plug high water-content oil wells.

[0031] (3) In the composite water plugging agent system of the present invention, the selective gel composite water plugging agent XSYNJ-3 has good injection selectivity for the target layer, has the characteristics of high strength and good rheology, and can preferentially enter the large pores or high permeability layers. The development of reservoir microcracks or the number of artificial cracks have requirements for the plugging amount. For reservoirs with small horizontal stress differences and large microcracks, multiple artificial cracks are formed after fracturing. For such wells, the plugging amount should be increased to achieve the effect of water plugging and oil increase.

[0032] (4) The optimization of the oil well water plugging process of the present invention can effectively improve the water plugging effect by using methods such as low-displacement squeeze injection, segmented plug squeeze injection, and variable viscosity alternating squeeze injection. The corresponding water injection well should be stopped before water plugging, which can effectively expand the direction of the plugging agent, thereby improving the water plugging effect. If the corresponding water injection well is not stopped, since the water-flooded cracks still have high pressure, the plugging agent enters the water-flooded channel very little, thus affecting the plugging efficiency.

[0033] (5) The method of the present invention can improve the injection and production effect of the well group by plugging water in the oil well, and improve the effectiveness of water injection in the well group. Water plugging can be used in combination with diversion fracturing, acidizing and other technologies to achieve the purpose of "reducing water and increasing oil production".

[0034] (6) The purpose of the multi-stage plug design of the method of the present invention is generally three-fold: first, to allow the plugging agent to make its own selection and give priority to plugging the water phase seepage channel; second, to allow the plugging agent to reach the strength designed in the scheme; and third, to allow the plugging strength to have a hierarchical alternation between "strong" and "weak" so as to better play their respective roles. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 2 This is a microscopic morphology of the nanoscale water plugging agent XSYD-1 of the present invention;

[0037] Figure 3 This is a microscopic morphology of the micron-scale expansion water plugging agent XSYD-2 in the present invention;

[0038] Figure 4 The evaluation results of the gelling performance of the selective gel composite water plugging agent XSYNJ-3 in Example 1;

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

[0040] In the figure, 1. front segment plug, 2. main segment plug, 3. rear segment plug, 4. sealing segment plug, 5. displacement segment plug, 6. water well, 7. oil well. DETAILED DESCRIPTION

[0041] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] The present invention provides a composite water plugging agent system, comprising a nano-scale water plugging agent XSYD-1, a micron-scale 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 nano-scale water plugging agent XSYD-1, the micron-scale 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 segment plugs according to the order of entering the well; Figure 1 As shown, the five slugs are respectively: a front slug 1, a main slug 2, a rear slug 3, a sealing slug 4 and a displacement slug 5 in the order of entering the well. The front slug 1 is close to the water well 6, and the displacement slug 5 is close to the oil well 7.

[0043] The first slug is the front slug, which uses nano-scale water plugging agent XSYD-1. The water plugging agent is composed of polymer microspheres, which are only nano-scale, such as Figure 2 As shown in the figure, the particle size range is 100-800 nanometers, and it can swell when it comes into contact with water, so it can achieve the blocking of the pore throat of the formation. In the early stage of injection, since the original size of the microspheres is only nanometers, which is much smaller than the size of the pore throat of the formation, it can smoothly enter the deep formation with the injected water. As the injection time continues to increase, the microspheres continue to hydrate and swell, and the final expansion system can reach 100 times the initial volume, thereby blocking large pores or high permeability layers and improving the liquid production profile.

[0044] Nano-scale water plugging agent XSYD-1 includes the following components by weight: 5-8 parts of white oil, 30-40 parts of comonomer, 10-14 parts of composite emulsifier, 20-26 parts of composite monomer, 20-26 parts of deionized water, 0.2-0.3 parts of crosslinking agent, 2-3 parts of rhamnolipid, 2-3 parts of phosphatidylethanolamine, 0.02-0.03 parts of initiator. The comonomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkyl sulfonic acid 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-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid in any ratio. The crosslinking agent is N,N'-methylenebisacrylamide. The initiator is azobisisobutyronitrile or azobisisoheptanitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanitrile, and the volume ratio of the two in the mixture is 1:1.

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

[0046] Step 1: Add the copolymer monomers composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in any ratio into the white oil, stir evenly, and then add the composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare the oil phase. Step 2: Weigh the composite monomers composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone, and ethylenediaminetetraacetic acid in any ratio, dissolve in deionized water, and then add the crosslinking agent of N,N'-methylenebisacrylamide, rhamnolipid, and phosphatidylethanolamine in sequence, mix and stir evenly, and prepare the water phase. Step 3, placing the oil phase in a reactor, stirring the solution evenly with a magnetic stirring needle, and then slowly adding the water phase for emulsification, stirring while adding, the rotation speed is 150rpm-200rpm, and the emulsification time is 0.5 hour-1 hour; Step 4, after the emulsification is completed, the reactor is heated to 30°C, and nitrogen is introduced for 0.5 hour-1 hour for deoxygenation; Step 5, after heating to 60°C, azobisisobutyronitrile or azobisisoheptanenitrile initiator is added to initiate a polymerization reaction, and the temperature is kept for 2 hours-3 hours; Step 6, a nano-scale water plugging agent is obtained by centrifugation; specifically, after cooling to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol, the rotation speed is 6000rpm-8000rpm, and the centrifugation time is 10 minutes-15 minutes, so as to obtain nano-scale polymer microspheres with a particle size range of 100 nanometers-800 nanometers.

[0047] The second segment plug is the main segment plug, which uses micron-grade water plugging agent XSYD-2 to plug the crack to 25 meters of the perforation hole and increase the static pressure in the crack. A self-controlled volume water absorption and expansion plugging agent is designed. The volume expands greatly by absorbing water, and the particles still have a certain elasticity after absorbing water, which can be deformed and squeezed into the leakage cracks of the formation to form a plugging layer with high strength and toughness. It can be evenly dispersed in water at any concentration and expand dozens or even hundreds of times after absorbing water. XSYD-2 water plugging agent overcomes the shortcomings of inorganic profile control agents that are dead, shallow, immobile, and not conducive to deep profile control and repeated profile control, and avoids the weaknesses of organic profile control agents that are low in strength and cannot block high permeability zones; at the same time, it absorbs the advantages of organic and inorganic profile control agents, can effectively block high permeability zones, and can maintain the characteristics of deformability and diffusibility, and migrate to the deep formation under the action of formation pressure and fluid dynamics. The main purpose of XSYD-2 water plugging agent is to plug micro cracks. It is composed of micron-sized expandable microsphere water plugging agent, which is composed of micron-sized polymer microspheres, which are micron-sized polymer gel spheres. A three-dimensional optical microscope is used to conduct microscopic analysis of the appearance and expanded morphology of the polymer microspheres, such as Figure 2 As shown. It can be seen that the microspheres are relatively uniform in size, high in sphericity, and have good dispersibility and suspension in the solution. The particle size of the micron-level polymer gel spheres in this area is 10-30 microns. They can be evenly dispersed in water at any concentration and expand dozens or even hundreds of times after absorbing water. Let it play the advantage of small particle size, while protecting the low permeability oil flow channel from pollution and blocking the relatively large water phase seepage channel.

[0048] The composition of the micron-level water plugging agent XSYD-2 is the same as that of the nano-level water plugging agent XSYD-1. The preparation method of the micron-level water plugging agent XSYD-2 is the same as steps 1 to 5 of the preparation method of the nano-level water plugging agent XSYD-1, and the difference lies in step 6; step 6 of the preparation method of the micron-level water plugging agent XSYD-2 is: after cooling to room temperature, centrifuging the liquid after the polymerization reaction obtained in step 5 with anhydrous ethanol, adjusting the speed to 2000rpm-3000rpm, the centrifugation time is 8 minutes-10 minutes, controlling the polymer microspheres to be micron-level, and the particle size range is 10-30 microns, to obtain the XSYD-2 water plugging agent.

[0049] The second section of the plug uses micron-grade expansion plugging agents to block large pores and micro cracks. The pressure rise is small during injection and the injection is smooth.

[0050] The third segment plug is a post-stage segment plug, which uses a selective gel composite water plugging agent XSYNJ-3, which is a gel system with a three-dimensional network structure formed by polymers and cross-linking agents, mainly intermolecular cross-linking and supplemented by intramolecular cross-linking. It blocks the main fractures and can effectively enter the fractures and then form gels. After gelling, it must have a certain strength. The system is a water-soluble substance before cross-linking, and produces lipophilic groups after cross-linking, thereby forming a mesh gel structure in the formation that allows oil to pass but blocks water.

[0051] The selective gel composite water plugging agent XSYNJ-3 includes 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 N,N'-methylenebisacrylamide crosslinking agent, 0.03-0.05 parts by weight of N-vinylpyrrolidone stabilizer, and 95-98 parts by weight of deionized water.

[0052] The preparation method of the selective gel composite water plugging agent XSYNJ-3 is as follows: 0.6-1.2 parts by weight of modified polyacrylamide, 0.6-1.5 parts by weight of N,N'-methylenebisacrylamide crosslinking agent and 0.03-0.05 parts by weight of N-vinyl pyrrolidone stabilizer are mixed with 95-98 parts by weight of deionized water to form a solution, stirred evenly, and after sufficient reaction for 1 hour to 1.5 hours, the selective gel composite water plugging agent XSYNJ-3 is generated.

[0053] The third section of the plug gradually blocks the water-producing fracture group and the high-permeability channel to achieve complete blocking. A gel-type plugging agent is used to block the front end of the main fracture, and the injection pressure increases by 3MPa-5MPa.

[0054] The fourth segment plug is a sealing segment plug, which uses a high-strength thermosetting resin system XSYFK-4 as a sealing agent. The formula of the high-strength thermosetting resin system XSYFK-4 is: based on 100 parts of the weight of micro-expanding early-strength silicate cement, 100 parts of micro-expanding early-strength silicate cement, 300 parts of high-strength thermosetting resin, 30-48 parts of curing agent, 2-3 parts of fluid loss reducer, 0-10 parts of setting regulator, 0.5-1 part of defoaming agent, and 35-120 parts of water.

[0055] The preparation method of the high-strength thermosetting resin system XSYFK-4 is as follows: the components including the high-strength thermosetting resin emulsion, the micro-expansion early-strength silicate cement, the curing agent, the fluid loss reducing agent, the setting regulator, the defoaming agent and the water are mixed evenly to obtain the high-strength thermosetting resin system XSYFK-4.

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

[0057]

[0058] The curing agent is anhydride.

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

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

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

[0062] The high-strength thermosetting resin reacts chemically with the curing agent, undergoes ring-opening, addition, and condensation reactions, and cross-links to form a dense, solid polymer body.

[0063] The best ratio is high-strength thermosetting resin emulsion: curing agent dosage = 100:10-16. The high-strength thermosetting resin slurry also has 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% G-grade cement, 1.2-1.5% expansion agent F17A-1, 1.8-2.0% early strength agent GJ-F, 0.3-0.5% drag reducer USZ, the sum of the mass percentages of the above components is 100%; it is a micro-expansion, early strength, silicate cement system. After the cement system is mixed, the water-cement ratio is calculated by weight, and the ratio of the cement system to water is 4:10. After solidification, the compressive strength can reach 29MPa; the initial setting time is controllable and adjustable within the range of 70-150min, the volume is slightly expanded by 0.2%, and a good bonding interface can be formed. It has the characteristics of no shrinkage after solidification, tight sealing, and continuous expansion force at the sealing point.

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

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

[0067] The fourth section plug is used to seal the large water-generating cracks and high-permeability channels with high-strength plugging agents. The section plug is designed from weak to strong to achieve effective sealing of the main seams, branch seams and ends. The injection methods mainly adopt two injection methods: water plugging truck and plunger pump, to achieve deep sealing of the oil layer and extend the effective period of water plugging.

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

[0069] The preparation method of the weak gel system XSYDT-5 is as follows: the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water-plugging agent XSYD-2 in the present invention, and its preparation method is the same as that of the micron-sized expansive water-plugging agent XSYD-2, that is, the deionized water in the micron-sized expansive water-plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water-plugging agent XSYD-2, and the concentration is only 20% of that of the micron-sized expansive water-plugging agent XSYD-2.

[0070] The segment plug can ensure that the high-strength thermosetting resin system XSYFK-4 reaches the accurate sealing position, and provides a stable working environment without water dilution and liquid flow during the curing of the sealing agent, ensuring a tight seal without external interference.

[0071] The weak gel system XSYDT-5 has a certain viscosity, which can well separate the high-strength thermosetting resin system XSYFK-4 from water during the displacement process, avoiding the continuous influx of water due to the influence of displacement pressure and pumping speed during the displacement process, affecting the sealing condition of the high-strength thermosetting resin system XSYFK-4, and ensuring the sealing strength and sealing performance.

[0072] The present invention also provides a multi-stage plugging method, which uses the above-mentioned combined water plugging agent system;

[0073] ① Pull out the tubing string: Pull out the tubing rods and accessories from the original well, rinse them with hot steam, and replace the unqualified tubing.

[0074] ②Well cleaning and well washing: Use a well cleaning gauge of appropriate specifications to clean the well to the bottom of the artificial well. Use positive circulation to clean the well, with a well cleaning fluid of 30-50m 3 (Adjust according to the well depth and well conditions), the well washing displacement is 400-500L / min, the water color of the returned well washing fluid inlet and outlet is consistent, and the actual sand surface or artificial well bottom operation is carried out again. If there is an obstruction during the well cleaning, the wellbore should be processed first, and then the well cleaning will continue.

[0075] ③Casing pressure test: The casing above the perforation section is tested by lowering the pressure test drill bit, and the pressure test is 20-25MPa with clean water. If the pressure drop is less than 0.5MPa in 20-30 minutes, it is qualified. Otherwise, double seal leak detection or cable logging and other casing damage well leak detection operations are carried out.

[0076] ④Multi-stage plugging and water blocking operation

[0077] The first step is to lower the water plugging drilling tool, set up the wellhead, and connect the ground spraying pipe line. The tool must not be put into the well for more than 24 hours before construction. The pipe string must be accurately measured to ensure the correct position of the tool. The KQ65 / 70 wellhead is used for water plugging construction. The pipe string structure (from bottom to top): 45° inclined tip (determined according to the wellbore structure) + external thickened oil pipe (smooth oil pipe) to the wellhead.

[0078] The second step is to close the casing gate and use the tubing positive squeeze method to pump in the first section of the front plug (nano-grade water plugging agent XSYD-1) with a displacement of 800-1000L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions. At the same time, the water absorption index is calculated and recorded.

[0079] In the third step, the tubing forward extrusion method is still used to pump in the second main section plug (micron-grade expansion water plugging agent XSYD-2), with a displacement of 700-1200L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions.

[0080] The fourth step is to continue to use the tubing forward extrusion method to pump in the third section of the rear plug (selective gel composite water plugging agent XSYNJ-3) with a displacement of 700-1200L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions.

[0081] The fifth step is to continue to use the tubing forward extrusion method to pump in the fourth sealing section plug (high-strength thermosetting resin system XSYFK-4) with a displacement of 500-1000L / min and a pressure less than 25MPa. The liquid volume is designed according to the well conditions. Intermittent displacement can also be used to ensure that the pressure increases gradually. After stopping the pump, the pressure drop is less than 3MPa.

[0082] Intermittent replacement sealing method, that is, not using the one-time replacement completion method, but multiple replacements, once every 10-20 minutes, each interval of 10-15 minutes, after the high-strength thermosetting resin system XSYFK-4 solidifies and pressurizes, continuously increase the replacement pressure, and finally replace the designed amount.

[0083] Step 6: Continue to use the tubing positive squeeze method to pump in the fifth section displacement plug (weak gel system XSYDT-5) with a displacement of 500-600L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and the excess high-strength thermosetting resin system XSYFK-4 is squeezed into the formation. When the pressure is above 20MPa, shut in the well and wait for 72-96 hours.

[0084] Step 7: After the water plugging measures are completed, the well is shut down for 72-96 hours and then the controlled release is carried out. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4-5mm nozzle to release until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release until the wellhead pressure is less than 3MPa; the third stage uses a 10-12mm nozzle to release until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release and accurately measure the amount of discharged fluid. Take samples for testing every shift and prepare a production status report. The subsequent fracturing construction process is determined based on the discharge situation.

[0085] The eighth step is fracturing construction, flowback, and pumping and completion according to geological requirements.

[0086] Example 1

[0087] L141-× Oil well water plugging operation

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

[0089] 1) Preparation: Prepare 50m3 of liquid 3 15 large tanks (1 for collecting residual liquid), 30m 3 1 large tank, the rear ends of all tanks must be raised, and the inside of the tank must be cleaned. High-pressure hoses, joints, and elbows are complete and intact (strength test pressure required is 25.0MPa). Prepare a Φ73mm bevel tip, a Φ118mm×1.5m well gauge, a GX-T140 scraper, 2000m of Φ73mm external thickened oil pipe, a KQ65 / 70 fracturing wellhead (the gate must be complete and intact), a K344-114 packer, a 5 1 / 2" hydraulic anchor, a Φ24mm straight nozzle, and several short sections. Before construction, prepare a 700-type pump truck for water supply and a liquid distribution funnel. Common tools and fire-fighting equipment are fully prepared according to normal construction needs. Labor protection equipment (rubber gloves, gas masks, goggles, masks, towels, etc.) is complete.

[0090] 2) Pull out the tubing string: Pull out the tubing rods and accessories from the original well, rinse them with hot steam, and replace the unqualified tubing.

[0091] 3) Well cleaning and well washing: Use a Φ118mm×1.5m well cleaning gauge to clean the well to the bottom of the artificial well, and use 30m of well washing fluid. 3 , the well washing displacement is 500L / min, the water color of the returned well washing fluid inlet and outlet is consistent, and the sand surface or artificial well bottom is explored again. (If there is an obstruction during the well cleaning, first deal with the wellbore and then continue to clean the well).

[0092] 4) Casing pressure test: The casing above the perforation section is pressure tested by the lower pressure test drill bit, and the clean water pressure test is 25MPa. It is qualified if the pressure drop is less than 0.5MPa in 30 minutes.

[0093] 5) Preparation for water plugging construction: lower the water plugging drill, set up the wellhead, and connect the ground spraying pipe line. (The tool must not be put into the well for more than 24 hours before construction, and the pipe string must be accurately measured to ensure the tool position is accurate). KQ65 / 70 wellhead is used for water plugging construction.

[0094] 6) Water plugging pump: Close the casing gate, use the tubing positive extrusion method, pump in the nano-scale water plugging agent XSYD-1 for the first section front plug, with a displacement of 850L / min, a pressure of less than 25MPa, and a liquid volume of 100 cubic meters. Then continue to use the tubing positive extrusion method to pump in the micron-level expansion water plugging agent XSYD-2) for the second section main section plug, with a displacement of 750L / min, a pressure of less than 25MPa, and a liquid volume of 160 cubic meters. Then, continue to use the tubing positive extrusion method to pump in the selective gel composite water plugging agent XSYNJ-3 for the third section rear plug, with a displacement of 780L / min, a pressure of less than 25MPa, and a liquid volume of 240 cubic meters. Then continue to use the tubing positive extrusion method to pump in the high-strength thermosetting resin system XSYFK-4 for the fourth section sealing plug, with a displacement of 600L / min, a pressure of less than 25MPa, and a liquid volume of 3 cubic meters, to ensure that the pressure gradually increases, and after stopping the pump, the pressure drop is less than 3MPa. Then continue to use the tubing forward squeeze method to pump in the weak gel system XSYDT-5 for the fifth section replacement plug, with a displacement of 500L / min, a pressure of less than 25MPa, and a liquid volume of 10 cubic meters to ensure that the wellbore is completely filled with the weak gel system XSYDT-5 and squeeze the excess high-strength thermosetting resin system XSYFK-4 into the formation.

[0095] 7) When the pressure reaches above 20MPa, shut in the well and wait for 72 hours. During the period of shutting in the well and waiting for condensation, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water supply before construction.

[0096] 8) After the water plugging measures are completed, the well is shut down and waited for 72 hours, and then the controlled release is carried out. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4mm nozzle to release until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release until the wellhead pressure is less than 3MPa; the third stage uses a 12mm nozzle to release until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release, and accurately measure the amount of discharged liquid. Take samples for testing every shift, prepare a production status report, and report the production results in a timely manner. Decide on water plugging and fracturing construction based on the discharge situation.

[0097] (9) Test well results: L141-X well produced 2.16m3 of fluid per day before water plugging and fracturing 3 , daily oil production 0.3t, water content 83.7%; after water plugging test, liquid production 3.72m 3 , daily oil production is 1.4 tons, with a water content of 71.6%; daily production increased by 1.1 tons, and the water content decreased by 12.1%.

[0098] The preparation method of the nano-scale water plugging agent XSYD-1 used in the front slug is as follows: first, 30 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in equal weight ratios are added to 5 parts by weight of white oil, and the mixture is stirred evenly, and then 10 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase;

[0099] Then, 20 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone and ethylenediaminetetraacetic acid in equal weight ratios were 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 phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0100] Then, the oil phase was placed in a reaction kettle, and after the solution was stirred evenly with a magnetic stirring needle, the water phase was slowly added for emulsification, stirring while adding, and the emulsification time was 0.5 hours;

[0101] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 0.5 hours to deoxygenate.

[0102] After the temperature was raised to 60° C., 0.02 parts by weight of azobisisobutyronitrile initiator was added to initiate the polymerization reaction, and the temperature was kept for 3 hours.

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

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

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

[0106] Table 1 Test results of nano-scale water plugging agent XSYD-1 in Example 1

[0107] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 30.2 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.02 4 Original size of micelle (nm) 300±20 302

[0108] The preparation method of the micron-scale water plugging agent XSYD-2 used in the main segment plug is different from that of the nano-scale water plugging agent XSYD-1 in that after the solution is cooled to room temperature, the nano-scale water plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 3000 rpm for 10 minutes. The morphology of the micron-scale water plugging agent XSYD-2 is as follows: Figure 3The specific test data are shown in Table 2.

[0109] Table 2 Test results of micron-grade water plugging agent XSYD-2 in Example 1

[0110] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥26 58.6 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.92-1.15 1.08 4 Original size of micelle (μm) 250±30 265

[0111] The preparation method of the selective gel composite water plugging agent XSYNJ-3 used for the post-stage plug is to mix 0.6 parts by weight of modified polyacrylamide, 0.6 parts by weight of N,N'-methylenebisacrylamide crosslinking agent and 0.03 parts by weight of N-vinyl pyrrolidone stabilizer with 95 parts by weight of deionized water to form a solution, stir evenly, and wait for full reaction for 1 hour to obtain the solution. The gelling property and stability evaluation are shown in Figure 4 and Figure 5 As shown, the test conditions are: C poly: 1200 mg / l, C cross: 60 mg / l, mineralization 12×10 4 mg / l. The gelation test results show that as the temperature rises, the gelation speed of the system accelerates and the gelation time becomes shorter, but it can still maintain a long gelation time at 90°C. The long-term stability of weak gel is an important indicator for evaluating its performance. From the experimental temperature of 90°C, it can be concluded that the viscosity retention rate of weak gel is still above 90% at 90 days.

[0112] The preparation method of the high-strength thermosetting resin system XSYFK-4 used for the sealing section plug is as follows: based on 100 parts of the weight of the micro-expanding early-strength silicate cement, 100 parts of the micro-expanding early-strength silicate cement, 300 parts of the high-strength thermosetting resin, 30 parts of phthalic anhydride, 2 parts of modified cellulose CMC, 1 part of trisodium citrate, 0.5 parts of the defoamer and 35 parts of water are uniformly mixed to obtain the obtained product; wherein the defoamer is composed of the following components by weight percentage: 40% silicone oil, 30% sodium stearate, 30% hydrophobic silica, and the sum of the mass percentages of the above components is 100%; the micro-expanding early-strength silicate cement is composed of the following components by weight percentage: 96% G-grade cement, 1.5% expansion agent F17A-1, 2.0% early strength agent GJ-F, 0.5% drag reducer 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] project 24h compressive strength (MPa) 24h bonding strength (MPa) Permeability (mD) data 39.7 3.36 0

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

[0116] Determine the location upper part Central lower part <![CDATA[Density (g / cm 3 )]]> 1.86 1.86 1.86

[0117] The preparation method of the weak gel system XSYDT-5 used for replacing the segment plug is as follows: the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water-plugging agent XSYD-2 in the present invention, and its preparation method is the same as that of the micron-sized expansive water-plugging agent XSYD-2, that is, the deionized water in the micron-sized expansive water-plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water-plugging agent XSYD-2, and the concentration is only 20% of that of the micron-sized expansive water-plugging agent XSYD-2.

[0118] Example 2

[0119] L139-× Oil well water plugging operation

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

[0121] 1) Preparation: Prepare 50m3 of liquid 3 15 large tanks (1 for collecting residual liquid), 30m 3 1 large tank, the rear ends of all tanks must be raised, and the inside of the tank must be cleaned. High-pressure hoses, joints, and elbows are complete and intact (strength test pressure required is 25.0MPa). Prepare a Φ73mm bevel tip, a Φ118mm×1.5m well gauge, a GX-T140 scraper, 2000m of Φ73mm external thickened oil pipe, a KQ65 / 70 fracturing wellhead (the gate must be complete and intact), a K344-114 packer, a 5 1 / 2" hydraulic anchor, a Φ24mm straight nozzle, and several short sections. Before construction, prepare a 700-type pump truck for water supply and a liquid distribution funnel. Common tools and fire-fighting equipment are fully prepared according to normal construction needs. Labor protection equipment (rubber gloves, gas masks, goggles, masks, towels, etc.) is complete.

[0122] 2) Lift the tubing string: lift the tubing rod and accessories, rinse them with hot steam, and replace the unqualified tubing.

[0123] 3) Well cleaning and well washing: Use a Φ118mm×1.5m well cleaning gauge to clean the well to the bottom of the artificial well, and use 30m of well washing fluid. 3 , the well washing displacement is 500L / min, the water color of the returned well washing fluid inlet and outlet is consistent, and the sand surface or artificial well bottom is explored again. (If there is an obstruction during the well cleaning, first deal with the wellbore and then continue to clean the well).

[0124] 4) Casing pressure test: The casing above the perforation section is pressure tested by the lower pressure test drill bit, and the clean water pressure test is 25MPa. It is qualified if the pressure drop is less than 0.5MPa in 30 minutes.

[0125] 5) Preparation for water plugging construction: lower the water plugging drill, set up the wellhead, and connect the ground spraying pipe line. (The tool must not be put into the well for more than 24 hours before construction, and the pipe string must be accurately measured to ensure the tool position is accurate). KQ65 / 70 wellhead is used for water plugging construction.

[0126] 6) Water plugging pump injection: Close the casing gate, use tubing positive extrusion to pump in the first section of the front plug (nano-grade water plugging agent XSYD-1), with a displacement of 900L / min, a pressure of less than 25MPa, and a liquid volume of 140 cubic meters. Then continue to use tubing positive extrusion to pump in the second section of the main plug (micron-grade expansion water plugging agent XSYD-2), with a displacement of 800L / min, a pressure of less than 25MPa, and a liquid volume of 200 cubic meters. Then, continue to use tubing positive extrusion to pump in the third section of the rear plug (selective gel composite water plugging agent XSYNJ-3), with a displacement of 800L / min, a pressure of less than 25MPa, and a liquid volume of 260 cubic meters. Then continue to use the tubing forward extrusion method to pump in the fourth section of the sealing plug (high-strength thermosetting resin system XSYFK-4), with a displacement of 550L / min, a pressure of less than 25MPa, and a liquid volume of 5 cubic meters, to ensure that the pressure gradually increases. After stopping the pump, the pressure drop is less than 3MPa. Then continue to use the tubing forward extrusion method to pump in the fifth section of the displacement plug (weak gel system XSYDT-5), with a displacement of 500L / min, a pressure of less than 25MPa, and a liquid volume of 10 cubic meters, to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and squeeze the excess high-strength thermosetting resin system XSYFK-4 into the formation.

[0127] 7) When the pressure reaches above 20MPa, shut in the well and wait for 72 hours. During the period of shutting in the well and waiting for condensation, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water supply before construction.

[0128] 8) After the water plugging measures are completed, the well is shut down and waited for 72 hours, and then the controlled release is carried out. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4mm nozzle to release until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release until the wellhead pressure is less than 3MPa; the third stage uses a 12mm nozzle to release until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release, and accurately measure the amount of discharged liquid. Take samples for testing every shift, prepare a production status report, and report the production results in a timely manner. Decide on water plugging and fracturing construction based on the discharge situation.

[0129] (9) Test well results: L139-X well produced 4.24m3 of fluid per day before water plugging and fracturing 3 , daily oil production 0t, water content 100%; after water plugging test, liquid production 3.53m 3 , daily oil production is 2.3 tons, with a water content of 39.5%; daily production increased by 2.3 tons, and the water content decreased by 60.5%.

[0130] The preparation method of the nano-scale water plugging agent XSYD-1 used in the front slug is as follows: first, 40 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in equal weight ratios are added to 8 parts by weight of white oil, and the mixture is stirred evenly, and then 14 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase;

[0131] Then, 26 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were 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 phosphatidylethanolamine were added in sequence, mixed and stirred evenly to prepare an aqueous phase;

[0132] Then, the oil phase was placed in a reaction kettle, and after the solution was stirred evenly with a magnetic stirring needle, the water phase was slowly added for emulsification, stirring while adding, and the emulsification time was 1 hour;

[0133] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 1 hour to deoxygenate.

[0134] After the temperature was raised to 60° C., 0.02 parts by weight of azobisisoheptanenitrile initiator was added to initiate the polymerization reaction, and the temperature was kept for 3 hours.

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

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

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

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

[0139] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 35.8 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.06 4 Original size of micelle (nm) 300±20 314

[0140] The difference between the preparation method of the micron-grade water-plugging agent XSYD-2 used in the main section plug and the nano-grade water-plugging agent XSYD-1 is that after the solution is cooled to room temperature, the nano-grade water-plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a rotation speed of 2500 rpm and a centrifugation time of 9 minutes.

[0141] Table 5 Test results of micron-grade water plugging agent XSYD-2 in Example 2

[0142] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥26 60.1 3 <![CDATA[Density, g / cm 3 (at 25°C)]]> 0.92-1.15 1.05 4 Original size of micelle (μm) 250±30 255

[0143] The preparation method of the selective gel composite water plugging agent XSYNJ-3 used for the post-stage plug is as follows: 1.0 weight part of modified polyacrylamide, 1.0 weight part of N,N'-methylenebisacrylamide crosslinking agent and 0.04 weight part of N-vinyl pyrrolidone stabilizer are mixed with 96 weight parts of deionized water to form a solution, stirred evenly, and fully reacted for 1 hour to obtain the solution. The test conditions for gelling and stability evaluation are: C poly: 1200mg / l, C crosslinking: 60mg / l, mineralization degree 12×10 4 mg / l. The gelation test results show that as the temperature rises, the gelation speed of the system accelerates and the gelation time becomes shorter, but it can still maintain a long gelation time at 90°C. The long-term stability of weak gel is an important indicator for evaluating its performance. From the experimental temperature of 90°C, it can be concluded that the viscosity retention rate of weak gel is still above 90% at 90 days.

[0144] The preparation method of the high-strength thermosetting resin system XSYFK-4 used for the sealing section plug is as follows: based on 100 parts of the weight of the micro-expanding early-strength silicate cement, 100 parts of the micro-expanding early-strength silicate cement, 300 parts of the 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 the defoamer and 50 parts of water are uniformly mixed to obtain the obtained product; wherein the defoamer is composed of the following components by weight percentage: 50% silicone oil, 25% sodium stearate, and 25% hydrophobic silica, and the sum of the mass percentages of the above components is 100%; the micro-expanding early-strength silicate cement is composed of the following components by weight percentage: 96.7% G-grade cement, 1.2% expansion agent F17A-1, 1.8% early strength agent GJ-F, 0.3% drag reducer USZ, and the ratio of the cement system to water is 4:10.

[0145] The preparation method of the weak gel system XSYDT-5 used for replacing the segment plug is the same as that of the micron-sized expansive water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water plugging agent XSYD-2 in the present invention, that is, the deionized water in the micron-sized expansive water plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water plugging agent XSYD-2, and the concentration is only 20% of that of the micron-sized expansive water plugging agent XSYD-2.

[0146] Example 3

[0147] L148-× Oil well water plugging operation

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

[0149] 1) Preparation: Prepare 50m3 of liquid 3 15 large tanks (1 for collecting residual liquid), 30m 3 1 large tank, the rear ends of all tanks must be raised, and the inside of the tank must be cleaned. High-pressure hoses, joints, and elbows are complete and intact (strength test pressure required is 25.0MPa). Prepare a Φ73mm bevel tip, a Φ118mm×1.5m well gauge, a GX-T140 scraper, 2000m of Φ73mm external thickened oil pipe, a KQ65 / 70 fracturing wellhead (the gate must be complete and intact), a K344-114 packer, a 5 1 / 2" hydraulic anchor, a Φ24mm straight nozzle, and several short sections. Before construction, prepare a 700-type pump truck for water supply and a liquid distribution funnel. Common tools and fire-fighting equipment are fully prepared according to normal construction needs. Labor protection equipment (rubber gloves, gas masks, goggles, masks, towels, etc.) is complete.

[0150] 2) Pull out the tubing string: Pull out the tubing rods and accessories from the original well, rinse them with hot steam, and replace the unqualified tubing.

[0151] 3) Well cleaning and well washing: Use a Φ118mm×1.5m well cleaning gauge to clean the well to the bottom of the artificial well, and use 30m of well washing fluid. 3 , the well washing displacement is 500L / min, the water color of the returned well washing fluid inlet and outlet is consistent, and the sand surface or artificial well bottom is explored again. (If there is an obstruction during the well cleaning, first deal with the wellbore and then continue to clean the well).

[0152] 4) Casing pressure test: The casing above the perforation section is pressure tested by the lower pressure test drill bit, and the clean water pressure test is 25MPa. It is qualified if the pressure drop is less than 0.5MPa in 30 minutes.

[0153] 5) Preparation for water plugging construction: lower the water plugging drill, set up the wellhead, and connect the ground spraying pipe line. (The tool must not be put into the well for more than 24 hours before construction, and the pipe string must be accurately measured to ensure the tool position is accurate). KQ65 / 70 wellhead is used for water plugging construction.

[0154] 6) Water plugging pump injection: Close the casing gate, use tubing positive extrusion to pump in the first section of the front plug (nano-grade water plugging agent XSYD-1), with a displacement of 860L / min, a pressure of less than 25MPa, and a liquid volume of 120 cubic meters. Then continue to use tubing positive extrusion to pump in the second section of the main plug (micron-grade expansion water plugging agent XSYD-2), with a displacement of 830L / min, a pressure of less than 25MPa, and a liquid volume of 120 cubic meters. Then, continue to use tubing positive extrusion to pump in the third section of the rear plug (selective gel composite water plugging agent XSYNJ-3), with a displacement of 750L / min, a pressure of less than 25MPa, and a liquid volume of 220 cubic meters. Then continue to use the tubing positive squeeze method to pump in the fourth section of the sealing plug (high-strength thermosetting resin system XSYFK-4), with a displacement of 550L / min, a pressure of less than 25MPa, and a liquid volume of 3 cubic meters, to ensure that the pressure gradually increases. After stopping the pump, the pressure drop is less than 3MPa. Then continue to use the tubing positive squeeze method to pump in the fifth section of the displacement plug (weak gel system XSYDT-5), with a displacement of 500L / min, a pressure of less than 25MPa, and a liquid volume of 10 cubic meters, to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and squeeze the excess high-strength thermosetting resin system XSYFK-4 into the formation.

[0155] 7) When the pressure reaches above 20MPa, shut in the well and wait for 72 hours. During the period of shutting in the well and waiting for condensation, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water supply before construction.

[0156] 8) After the water plugging measures are completed, the well is shut down and waited for 72 hours, and then the controlled release is carried out. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4mm nozzle to release until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release until the wellhead pressure is less than 3MPa; the third stage uses a 12mm nozzle to release until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release, and accurately measure the amount of discharged liquid. Take samples for testing every shift, prepare a production status report, and report the production results in a timely manner. Decide on water plugging and fracturing construction based on the discharge situation.

[0157] (9) Test well results: L148-X well produced 5.36m3 of fluid per day before water plugging and fracturing 3 , daily oil production 0t, water content 100%; after water plugging test, liquid production 3.86m 3 , daily oil production is 1.6 tons, with a water content of 65.5%; daily production increased by 1.6 tons, and the water content decreased by 34.5%.

[0158] The preparation method of the nano-scale water plugging agent XSYD-1 used in the front slug is as follows: first, 35 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in equal weight ratios are added to 6 parts by weight of white oil, and the mixture is stirred evenly, and then 12 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase;

[0159] Then, 22 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were weighed and dissolved in 22 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 phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0160] Then, the oil phase was placed in a reaction kettle, and the solution was stirred evenly with a magnetic stirring needle, and then the water phase was slowly added for emulsification, with stirring during the addition, and the emulsification time was 0.75 hours;

[0161] Then, after the emulsification was completed, the reactor was heated to 30°C and nitrogen was introduced for 0.5 hours to deoxygenate.

[0162] After the temperature was raised to 60° C., 0.025 parts by weight of an initiator consisting of azobisisobutyronitrile and azobisisoheptanenitrile in an equal volume ratio was added to initiate a polymerization reaction, and the temperature was kept for 2.5 hours.

[0163] Finally, after the solution is cooled to room temperature, the nanoscale water plugging agent is obtained by centrifugation. Step 6 is specifically as follows: after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 7000 rpm for 12 minutes.

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

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

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

[0167] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 36.2 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.03 4 Original size of micelle (nm) 300±20 310

[0168] The difference between the preparation method of the micron-grade water-plugging agent XSYD-2 used in the main section plug and the nano-grade water-plugging agent XSYD-1 is that after the solution is cooled to room temperature, the nano-grade water-plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid after the polymerization reaction obtained in step 5 is centrifuged with anhydrous ethanol at a rotation speed of 3000 rpm and a centrifugation time of 10 minutes.

[0169] Table 6 Test results of micron-grade water plugging agent XSYD-2 in Example 1

[0170] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥26 39.2 3 <![CDATA[Density, g / cm 3 (at 25°C)]]> 0.92-1.15 0.98 4 Original size of micelle (μm) 250±30 248

[0171] The preparation method of the selective gel composite water plugging agent XSYNJ-3 used for the post-stage plug is as follows: 1.2 parts by weight of modified polyacrylamide, 1.5 parts by weight of N,N'-methylenebisacrylamide crosslinking agent and 0.05 parts by weight of N-vinyl pyrrolidone stabilizer are mixed with 98 parts by weight of deionized water to form a solution, stirred evenly, and allowed to fully react for 1 hour to obtain the solution. The test conditions for gelling and stability evaluation are: C poly: 1200 mg / l, C crosslinking: 60 mg / l, mineralization degree 12×10 4 mg / l. The gelation test results show that as the temperature rises, the gelation speed of the system accelerates and the gelation time becomes shorter, but it can still maintain a long gelation time at 90°C. The long-term stability of weak gel is an important indicator for evaluating its performance. From the experimental temperature of 90°C, it can be concluded that the viscosity retention rate of weak gel is still above 90% at 90 days.

[0172] The preparation method of the high-strength thermosetting resin system XSYFK-4 used for the sealing section plug is as follows: based on 100 parts of the weight of the micro-expanding early-strength silicate cement, 100 parts of the micro-expanding early-strength silicate cement, 300 parts of the high-strength thermosetting resin, 48 parts of phthalic anhydride, 3 parts of modified cellulose CMC, 10 parts of trisodium citrate, 1 part of the defoamer and 120 parts of water are uniformly mixed to obtain the obtained product; wherein the defoamer is composed of the following components by weight percentage: 45% silicone oil, 27.5% sodium stearate, 27.5% hydrophobic silica, and the sum of the mass percentages of the above components is 100%; the micro-expanding early-strength silicate cement is composed of the following components by weight percentage: 96.6% G-grade cement, 1.2% expansion agent F17A-1, 1.8% early strength agent GJ-F, 0.4% drag reducer USZ, and the ratio of the cement system to water is 4:10.

[0173] The preparation method of the weak gel system XSYDT-5 used for replacing the segment plug is the same as that of the micron-sized expansive water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water plugging agent XSYD-2 in the present invention, that is, the deionized water in the micron-sized expansive water plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water plugging agent XSYD-2, and the concentration is only 20% of that of the micron-sized expansive water plugging agent XSYD-2.

[0174] Example 4

[0175] L146-× Oil well water plugging operation

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

[0177] 1) Preparation: Prepare 50m3 of liquid 3 15 large tanks (1 for collecting residual liquid), 30m 3 1 large tank, the rear ends of all tanks must be raised, and the inside of the tank must be cleaned. High-pressure hoses, joints, and elbows are complete and intact (strength test pressure required is 25.0MPa). Prepare a Φ73mm bevel tip, a Φ118mm×1.5m well gauge, a GX-T140 scraper, 2000m of Φ73mm external thickened oil pipe, a KQ65 / 70 fracturing wellhead (the gate must be complete and intact), a K344-114 packer, a 5 1 / 2" hydraulic anchor, a Φ24mm straight nozzle, and several short sections. Before construction, prepare a 700-type pump truck for water supply and a liquid distribution funnel. Common tools and fire-fighting equipment are fully prepared according to normal construction needs. Labor protection equipment (rubber gloves, gas masks, goggles, masks, towels, etc.) is complete.

[0178] 2) Pull out the tubing string: Pull out the tubing rods and accessories from the original well, rinse them with hot steam, and replace the unqualified tubing.

[0179] 3) Well cleaning and well washing: Use a Φ118mm×1.5m well cleaning gauge to clean the well to the bottom of the artificial well, and use 30m of well washing fluid. 3 , the well washing displacement is 500L / min, the water color of the returned well washing fluid inlet and outlet is consistent, and the sand surface or artificial well bottom is explored again. (If there is an obstruction during the well cleaning, first deal with the wellbore and then continue to clean the well).

[0180] 4) Casing pressure test: The casing above the perforation section is pressure tested by the lower pressure test drill bit, and the clean water pressure test is 25MPa. It is qualified if the pressure drop is less than 0.5MPa in 30 minutes.

[0181] 5) Preparation for water plugging construction: lower the water plugging drill, set up the wellhead, and connect the ground spraying pipe line. (The tool must not be put into the well for more than 24 hours before construction, and the pipe string must be accurately measured to ensure the tool position is accurate). KQ65 / 70 wellhead is used for water plugging construction.

[0182] 6) Water plugging pump injection: Close the casing gate, use tubing positive extrusion to pump in the first section of the front plug (nano-grade water plugging agent XSYD-1), with a displacement of 820L / min, a pressure of less than 25MPa, and a liquid volume of 140 cubic meters. Then continue to use tubing positive extrusion to pump in the second section of the main plug (micron-grade expansion water plugging agent XSYD-2), with a displacement of 800L / min, a pressure of less than 25MPa, and a liquid volume of 140 cubic meters. Then, continue to use tubing positive extrusion to pump in the third section of the rear plug (selective gel composite water plugging agent XSYNJ-3), with a displacement of 700L / min, a pressure of less than 25MPa, and a liquid volume of 200 cubic meters. Then continue to use the tubing forward extrusion method to pump in the fourth section of the sealing plug (high-strength thermosetting resin system XSYFK-4), with a displacement of 500L / min, a pressure of less than 25MPa, and a liquid volume of 3 cubic meters, to ensure that the pressure gradually increases. After stopping the pump, the pressure drop is less than 3MPa. Then continue to use the tubing forward extrusion method to pump in the fifth section of the displacement plug (weak gel system XSYDT-5), with a displacement of 560L / min, a pressure of less than 25MPa, and a liquid volume of 8 cubic meters, to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and squeeze the excess high-strength thermosetting resin system XSYFK-4 into the formation.

[0183] 7) When the pressure reaches above 20MPa, shut in the well and wait for 72 hours. During the period of shutting in the well and waiting for condensation, closely monitor the wellhead tubing pressure and casing pressure, and prepare a 700-type pump truck for water supply before construction.

[0184] 8) After the water plugging measures are completed, the well is shut down and waited for 72 hours, and then the controlled release is carried out. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4mm nozzle to release until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release until the wellhead pressure is less than 3MPa; the third stage uses a 12mm nozzle to release until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release, and accurately measure the amount of discharged liquid. Take samples for testing every shift, prepare a production status report, and report the production results in a timely manner. Decide on water plugging and fracturing construction based on the discharge situation.

[0185] (9) Test well results: L146-X well produced 6.87m3 of fluid per day before water plugging and fracturing 3 , daily oil production 0.6t, water content 95.2%; after water plugging test, liquid production 4.53m 3 , daily oil production is 2.8 tons, with a water content of 39.5%; daily production increased by 2.2 tons, and the water content decreased by 55.7%.

[0186] The preparation method of the nano-scale water plugging agent XSYD-1 used in the front slug is as follows: first, 36 parts of copolymer monomers composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkyl sulfonic acetamide, and alkyl succinate sulfonate in equal weight ratios are added to 7 parts by weight of white oil, and the mixture is stirred evenly, and then 13 parts by weight of a composite emulsifier composed of a mixture of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in equal weight ratios is added to prepare an oil phase;

[0187] Then, 23 parts by weight of a composite monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid in equal weight ratios were weighed and 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 phosphatidylethanolamine were added in sequence, and the mixture was mixed and stirred evenly to prepare an aqueous phase;

[0188] Then, the oil phase was placed in a reaction kettle, and the solution was stirred evenly with a magnetic stirring needle, and then the water phase was slowly added for emulsification, with stirring during the addition, and the emulsification time was 0.75 hours;

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

[0190] After the temperature was raised to 60° C., 0.025 parts by weight of azobisisoheptanenitrile initiator was added to initiate the polymerization reaction, and the temperature was kept 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 the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a speed of 6500 rpm for 15 minutes.

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

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

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

[0195] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥18 33.5 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.85-1.1 1.05 4 Original size of micelle (nm) 300±20 309

[0196] The difference between the preparation method of the micron-grade water-plugging agent XSYD-2 used in the main section plug and the nano-grade water-plugging agent XSYD-1 is that after the solution is cooled to room temperature, the nano-grade water-plugging agent is obtained by centrifugation. Specifically, after the solution is cooled to room temperature, the liquid obtained in step 5 after the polymerization reaction is centrifuged with anhydrous ethanol at a rotation speed of 3000 rpm and a centrifugation time of 8 minutes.

[0197] Table 8 Test results of micron-grade water plugging agent XSYD-2 in Example 1

[0198] Serial number project index Test results 1 Appearance White or brownish yellow emulsion qualified 2 Separable solid content, % ≥26 54.3 3 <![CDATA[Density, g / cm 3 (at 25 °C)]]> 0.92-1.15 1.04 4 Original size of micelle (μm) 250±30 274

[0199] The preparation method of the selective gel composite water plugging agent XSYNJ-3 used for the post-stage plug is as follows: 1.2 parts by weight of modified polyacrylamide, 1.5 parts by weight of N,N'-methylenebisacrylamide crosslinking agent and 0.05 parts by weight of N-vinyl pyrrolidone stabilizer are mixed with 97 parts by weight of deionized water to form a solution, stirred evenly, and fully reacted for 1 hour to obtain the solution. The test conditions for gelling and stability evaluation are: C poly: 1200mg / l, C crosslinking: 60mg / l, mineralization 12×10 4 mg / l. The gelation test results show that as the temperature rises, the gelation speed of the system accelerates and the gelation time becomes shorter, but it can still maintain a long gelation time at 90°C. The long-term stability of weak gel is an important indicator for evaluating its performance. From the experimental temperature of 90°C, it can be concluded that the viscosity retention rate of weak gel is still above 90% at 90 days.

[0200] The preparation method of the high-strength thermosetting resin system XSYFK-4 used for the sealing section plug is as follows: based on 100 parts of the weight of the micro-expanding early-strength silicate cement, 100 parts of the micro-expanding early-strength silicate cement, 300 parts of the high-strength thermosetting resin, 47 parts of phthalic anhydride, 3 parts of modified cellulose CMC, 10 parts of trisodium citrate, 1 part of the defoamer and 100 parts of water are uniformly mixed to obtain the obtained product; wherein the defoamer is composed of the following components by weight percentage: 45% silicone oil, 27.5% sodium stearate, 27.5% hydrophobic silica, and the sum of the mass percentages of the above components is 100%; the micro-expanding early-strength silicate cement is composed of the following components by weight percentage: 96.6% G-grade cement, 1.2% expansion agent F17A-1, 1.8% early strength agent GJ-F, 0.4% drag reducer USZ, and the ratio of the cement system to water is 4:10.

[0201] The preparation method of the weak gel system XSYDT-5 used for replacing the segment plug is the same as that of the micron-sized expansive water plugging agent XSYD-2 except that the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water plugging agent XSYD-2 in the present invention, that is, the deionized water in the micron-sized expansive water plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water plugging agent XSYD-2, and the concentration is only 20% of that of the micron-sized expansive water plugging agent XSYD-2.

Claims

1. Composite water plugging agent system, characterized in that: It includes nano-scale water plugging agent XSYD-1, micron-scale water plugging agent XSYD-2, selective gel composite water plugging agent XSYNJ-3, high-strength thermosetting resin system XSYFK-4 and weak gel system XSYDT-5; nano-scale water plugging agent XSYD-1, micron-scale water plugging agent XSYD-2, selective gel composite water plugging agent XSYNJ-3, high-strength thermosetting resin system XSYFK-4 and weak gel system XSYDT-5 correspond to five segment plugs according to the order of entering the well; the five segment plugs according to the order of entering the well are: front segment plug, main segment plug, rear segment plug, sealing segment plug and replacement segment plug.

2. The composite water plugging agent system according to claim 1, characterized in that: The nanoscale water plugging agent XSYD-1 comprises the following components by weight: 5 to 8 parts of white oil, 30 to 40 parts of comonomer, 10 to 14 parts of composite emulsifier, 20 to 26 parts of composite monomer, 20 to 26 parts of deionized water, 0.2 to 0.3 parts of crosslinking agent, 2 to 3 parts of rhamnolipid, 2 to 3 parts of phosphatidylethanolamine, and 0.02 to 0.03 parts of initiator; The copolymer monomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, alkyl sulfonic acetamide and alkyl succinate sulfonate in any proportion; the composite emulsifier is composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any proportion; the composite monomer is composed of acrylamide, 2-acrylamide-2-methylpropanesulfonic acid, N-vinyl pyrrolidone and ethylenediaminetetraacetic acid in any proportion; the crosslinking agent is N,N'-methylenebisacrylamide; the initiator is azobisisobutyronitrile or azobisisoheptanenitrile, or a mixture of azobisisobutyronitrile and azobisisoheptanenitrile, and the volume ratio of the two in the mixture is 1:

1.

3. The composite water plugging agent system according to claim 2, characterized in that: The preparation method of the nano-scale water plugging agent XSYD-1 specifically comprises the following steps: Step 1, adding a copolymer monomer composed of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, alkylsulfonic acetamide, and alkyl succinate sulfonate in any ratio into white oil, stirring evenly, and then adding a composite emulsifier composed of sorbitan fatty acid ester and sorbitan monooleate polyoxyethylene ether in any ratio to prepare an oil phase; Step 2, weighing a composite monomer of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinylpyrrolidone, and ethylenediaminetetraacetic acid mixed in any ratio, dissolving it in deionized water, and then sequentially adding a crosslinker of N,N'-methylenebisacrylamide, rhamnolipid, and phosphatidylethanolamine, mixing and stirring evenly to prepare an aqueous phase; Step 3, placing the oil phase in a reaction kettle, stirring the solution evenly with a magnetic stirring needle, and then slowly adding the water phase for emulsification, stirring while adding, the rotation speed is 150rpm-200rpm, and the emulsification time is 0.5 hour-1 hour; Step 4: After emulsification is completed, the reactor is heated to 30°C and nitrogen is introduced for 0.5-1 hour to remove oxygen; Step 5, after heating to 60° C., add azobisisobutyronitrile or azobisisoheptanenitrile initiator to initiate polymerization reaction, and keep warm for 2 to 3 hours; Step 6, obtaining the nano-scale water plugging agent by centrifugal separation; specifically, after cooling to room temperature, centrifuging the liquid obtained in step 5 after the polymerization reaction with anhydrous ethanol at a speed of 6000rpm-8000rpm and a centrifugal time of 10 minutes-15 minutes.

4. The composite water plugging agent system according to claim 3, characterized in that: The raw material components and proportions of the micron-level water plugging agent XSYD-2 are the same as those of the nano-level water plugging agent XSYD-1; the preparation method of the micron-level water plugging agent XSYD-2 is the same as steps 1 to 5 of the preparation method of the nano-level water plugging agent XSYD-1, and the difference lies in step 6; step 6 of the preparation method of the micron-level water plugging agent XSYD-2 is: after cooling to room temperature, centrifuging the liquid after the polymerization reaction obtained in step 5 with anhydrous ethanol, adjusting the speed to 2000rpm-3000rpm, and the centrifugation time is 8 minutes-10 minutes.

5. The composite water plugging agent system according to claim 1, characterized in that: 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 N,N'-methylenebisacrylamide crosslinking agent, 0.03-0.05 parts by weight of N-vinylpyrrolidone stabilizer, and 95-98 parts by weight of deionized water.

6. The composite water plugging agent system according to claim 1, characterized in that: The formula of the high-strength thermosetting resin system XSYFK-4 is: based on 100 parts of the weight of the micro-expanding early-strength silicate cement, 100 parts of the micro-expanding early-strength silicate cement, 300 parts of the high-strength thermosetting resin, 30-48 parts of the curing agent, 2-3 parts of the fluid loss reducer, 0-10 parts of the setting regulator, 0.5-1 part of the defoaming agent, and 35-120 parts of water.

7. The composite water plugging agent system according to claim 6, characterized in that: Formula of high-strength thermosetting resin system XSYFK-4: (1) Micro-expanding early-strengthening silicate cement, which is composed of the following components by weight percentage: 96-97% of G-grade cement, 1.2-1.5% of expansion agent F17A-1, 1.8-2.0% of early-strength agent GJ-F, and 0.3-0.5% of drag reducer USZ, and the sum of the mass percentages of the above components is 100%; (2) The chemical formula of high-strength thermosetting resin is as follows: (3) The curing agent is anhydride; (4) The fluid loss reducer is modified cellulose CMC; (5) The coagulant is trisodium citrate; (6) The defoaming agent is composed of the following components by weight: 40%-50% silicone oil, 20%-30% sodium stearate, and 20%-30% hydrophobic silica, and the sum of the weight percentages of the above components is 100%.

8. The composite water plugging agent system according to claim 4, characterized in that: The weak gel system XSYDT-5 comprises the following components in parts by weight: 5 to 8 parts of white oil, 30 to 40 parts of comonomers, 10 to 14 parts of composite emulsifiers, 20 to 26 parts of composite monomers, 100 to 130 parts of deionized water, 0.2 to 0.3 parts of crosslinking agent, 2 to 3 parts of rhamnolipid, 2 to 3 parts of phosphatidylethanolamine, and 0.02 to 0.03 parts of initiator; The preparation method of the weak gel system XSYDT-5 is as follows: except that the amount of deionized water in the weak gel system XSYDT-5 is different from that of the micron-sized expansive water-plugging agent XSYD-2 in the present invention, the preparation method is the same as that of the micron-sized expansive water-plugging agent XSYD-2, that is, the deionized water in the micron-sized expansive water-plugging agent XSYD-2 is increased to 5 times the deionized water in the micron-sized expansive water-plugging agent XSYD-2.

9. A multi-stage plugging method, characterized in that: The composite water plugging agent system according to any one of claims 1 to 8 is used and implemented according to the following steps: pipe string lifting, well clearing, well washing, casing pressure testing and multi-stage plugging and water plugging operations.

10. The multi-stage plugging method according to claim 9, characterized in that: The multi-stage plugging operation is specifically implemented according to the following steps: The first step is to lower the water-blocking drill bit, set up the wellhead, and connect the ground spray line; The second step is to close the casing gate and use the tubing positive squeeze method to pump in the nano-scale water plugging agent XSYD-1 used for the first section of the front slug, with a displacement of 800L / min-1000L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions. In the third step, the tubing forward squeezing method is still used to pump in the micron-grade expansion water plugging agent XSYD-2 used for the second main section plug, with a displacement of 700L / min-1200L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions. The fourth step is to continue to use the tubing forward squeezing method to pump in the selective gel composite water plugging agent XSYNJ-3 for the third section rear plug, with a displacement of 700L / min-1200L / min, a pressure of less than 25MPa, and a liquid volume designed according to the well conditions; Step 5: Continue to use the tubing forward extrusion method to pump in the high-strength thermosetting resin system XSYFK-4 used for the fourth section sealing plug, with a displacement of 500L / min-1000L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions, or an intermittent displacement method is used to ensure that the pressure gradually increases. After stopping the pump, the pressure drop is less than 3Mpa. In the fifth step, the intermittent replacement sealing method, that is, not using the replacement completion method, but multiple replacements, replacement every 10min-20min, each interval of 10min-15min, after the high-strength thermosetting resin system XSYFK-4 is solidified and pressurized, the replacement pressure is continuously increased, and finally the design amount is replaced; Step 6: Continue to use the tubing positive squeeze method to pump in the weak gel system XSYDT-5 for the fifth section to replace the plug, with a displacement of 500L / min-600L / min and a pressure of less than 25MPa. The liquid volume is designed according to the well conditions to ensure that the wellbore is completely filled with the weak gel system XSYDT-5, and squeeze the excess high-strength thermosetting resin system XSYFK-4 into the formation. When the pressure starts to exceed 20MPa, shut in the well and wait for 72-96 hours; Step 7: After the water plugging measures are completed, the well is shut down for 72 to 96 hours and then controlled to release the fluid. Depending on the pressure drop, the controlled release is divided into four stages: the first stage uses a 4mm-5mm nozzle to release the fluid until the wellhead pressure is less than 5MPa; the second stage uses an 8mm nozzle to release the fluid until the wellhead pressure is less than 3MPa; the third stage uses a 10mm-12mm nozzle to release the fluid until the wellhead pressure is less than 1MPa; the fourth stage: fully open the wellhead gate for release and accurately measure the amount of discharged fluid; The eighth step is fracturing construction, flowback, and pumping and completion according to geological requirements.

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