Rock core injection method for improving temperature resistance and salt resistance of polymer-containing profile control and flooding agent

Abstract

The invention provides a rock core injection method for improving temperature resistance and salt resistance of a polymer-containing modifying and flooding agent, and particularly relates to the technical field of oil reservoir development. The polymer-containing modifying and flooding agent is a water-soluble polymer microsphere or a non-water-soluble polymer microsphere; when the polymer-containing modifying and flooding agent is a water-soluble polymer, the method comprises the following steps: mixing the polymer-containing modifying and flooding agent, silicate and first injection water to form a polymer-containing modifying and flooding agent-silicate composite gel solution; alternately injecting the polymer-containing modifying and flooding agent-silicate composite gel liquid and second injection water into a rock core; when the polymer-containing modifying and flooding agent is a water-insoluble polymer microsphere, the method comprises the following steps: mixing the polymer-containing modifying and flooding agent with injected water to form a polymer-containing modifying and flooding agent suspension; mixing silicate and injection water to form a silicate solution; and alternately injecting the suspension containing the polymer modifying and flooding agent and the silicate solution into the rock core. Sodium silicate reacts with Ca < 2 + > and Mg < 2 + > to generate inorganic gel, so that the salt tolerance of the polymer-containing modifying and flooding agent is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of reservoir development, and particularly relates to a method for injecting cores to improve the temperature and salt resistance of a polymer-containing profile control agent. Background Art

[0002] For a long time, the domestic oil consumption and import volume have shown a gradually increasing trend. The efficient development of high water cut old oilfields is of great practical significance for reducing oil imports and ensuring national energy security. However, most domestic oilfields belong to continental sedimentary reservoirs, which are characterized by strong reservoir heterogeneity. After long-term high-intensity water injection development, the reservoir heterogeneity is further aggravated, and the phenomenon of inefficient and ineffective circulation of injected water in high-permeability layers or large channels has become increasingly serious, seriously affecting the swept efficiency of injected water.

[0003] In order to improve the effect of water injection development, a profile control agent is usually injected into injection wells. However, for traditional injection methods, the profile control agent has a low permeability to injection wells, thereby reducing the core plugging effect. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for injecting cores to improve the temperature and salt resistance of a polymer-containing profile control agent. The method provided by the present invention can improve the permeability of traditional profile control agents to injection wells, improve the core plugging effect, and is conducive to the stable operation of oilfields.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for injecting cores to improve the temperature and salt resistance of a polymer-containing profile control agent, and the polymer-containing profile control agent is a water-soluble polymer or a water-insoluble polymer microsphere;

[0007] When the polymer-containing profile control agent is a water-soluble polymer, the method comprises the following steps:

[0008] Mix a polymer-containing profile control agent, a silicate, and a first injection water to form a polymer-containing profile control agent-silicate composite gel solution;

[0009] Alternately inject the polymer-containing profile control agent-silicate composite gel solution and a second injection water into a core;

[0010] When the polymer-containing profile control agent is a water-insoluble polymer microsphere, the method comprises the following steps:

[0011] Mix a polymer-containing profile control agent and an injection water to form a polymer-containing profile control agent suspension;

[0012] Mix a silicate and water to form a silicate solution;

[0013] Alternately inject the polymer-containing profile control agent suspension and the silicate solution into a core;

[0014] When the polyacrylamide-based profile control and displacement agent is a water-soluble polymer, the Ca content in the first injection water and the second injection water is > 500 mg / L, and the Mg content is > 200 mg / L; or when the polyacrylamide-based profile control and displacement agent is a water-insoluble polymer microsphere, the Ca content in the injection water is > 500 mg / L, and the Mg content is > 200 mg / L. 2+ content > 500mg / L, Mg 2+ content > 200mg / L; or when the polyacrylamide-based profile control and displacement agent is a water-insoluble polymer microsphere, the Ca 2+ content > 500mg / L, Mg 2+ content > 200mg / L.

[0015] Preferably, the mass concentration of the polyacrylamide-based profile control and displacement agent in the polyacrylamide-based profile control and displacement agent-silicate composite gel solution is 0.01 - 0.30%;

[0016] the mass concentration of silicate in the polyacrylamide-based profile control and displacement agent-silicate composite gel solution is 0.01 - 10%.

[0017] Preferably, when the polyacrylamide-based profile control and displacement agent is a water-soluble polymer, the ratio of the total injection volume of the polyacrylamide-based profile control and displacement agent-silicate composite gel solution to the pore volume of the core is 3 - 8:1; the volume ratio of the polyacrylamide-based profile control and displacement agent-silicate composite gel solution to the second injection water is 1 - 2:1.

[0018] Preferably, any one of Method 1, Method 2, and Method 3 is used for mixing the polyacrylamide-based profile control and displacement agent, silicate, and the first injection water:

[0019] Method 1 includes: dissolving the polyacrylamide-based profile control and displacement agent in a part of the first injection water to obtain a polyacrylamide-based profile control and displacement agent solution; dissolving the silicate in the remaining first injection water to obtain a silicate solution; using a drip pump to add the polyacrylamide-based profile control and displacement agent solution and the silicate solution to the high-pressure water injection pipeline and mixing them through a static mixer;

[0020] Method 2 includes: dissolving the polyacrylamide-based profile control and displacement agent in the first injection water to obtain a polyacrylamide-based profile control and displacement agent solution; using a drip pump to add the polyacrylamide-based profile control and displacement agent solution to the high-pressure water injection pipeline, adding silicate to the high-pressure water injection pipeline, and mixing them through a static mixer;

[0021] Method 3 includes: dissolving the silicate in the first injection water to obtain a silicate solution; using a drip pump to add the silicate solution to the high-pressure water injection pipeline, adding the polyacrylamide-based profile control and displacement agent to the high-pressure water injection pipeline, and mixing them through a static mixer.

[0022] Preferably, the mixing speed in Method 1, Method 2, and Method 3 is 200 - 500 rpm, and the shearing time is 2 - 4 h.

[0023] Preferably, the mass concentration of the polyacrylamide-based profile control and displacement agent in the polyacrylamide-based profile control and displacement agent suspension is 0.01 - 0.30%;

[0024] The mass concentration of silicate in the silicate solution is 0.01-10%.

[0025] Preferably, when the polymer-containing profile control and displacement agent is a polymer microsphere, the ratio of the total injection volume of the polymer-containing profile control and displacement agent suspension to the pore volume of the core is 2-5:1; the volume ratio of the polymer-containing profile control and displacement agent suspension to the silicate solution is 1-2:1.

[0026] Preferably, the silicate includes sodium silicate and / or potassium silicate.

[0027] Preferably, when the polymer-containing profile control and displacement agent is a water-soluble polymer or a water-insoluble polymer microsphere, the number of times of alternating injection is 4-8 times.

[0028] Preferably, the water used when mixing silicate and water is softened water or injection water. When it is softened water, the Ca 2+ content < 40 mg / L, and the Mg 2+ content < 30 mg / L. When it is injection water, the Ca 2+ content > 500 mg / L, and the Mg 2+ content > 200 mg / L.

[0029] The present invention provides a method for injecting a polymer-containing profile control and displacement agent into a core. The polymer-containing profile control and displacement agent is a water-soluble polymer or a water-insoluble polymer microsphere; when the polymer-containing profile control and displacement agent is a water-soluble polymer, the method includes the following steps: mixing the polymer-containing profile control and displacement agent, silicate and first injection water to form a polymer-containing profile control and displacement agent-silicate composite gel solution; alternately injecting the polymer-containing profile control and displacement agent-silicate composite gel solution and second injection water into the core; when the polymer-containing profile control and displacement agent is a water-insoluble polymer microsphere, the method includes the following steps: mixing the polymer-containing profile control and displacement agent and injection water to form a polymer-containing profile control and displacement agent suspension; mixing silicate and injection water to form a silicate solution; alternately injecting the polymer-containing profile control and displacement agent suspension and the silicate solution into the core; when the polymer-containing profile control and displacement agent is a water-soluble polymer, the Ca 2+ content in the first injection water and the second injection water > 500 mg / L, and the Mg 2+ content > 200 mg / L; or when the polymer-containing profile control and displacement agent is a water-insoluble polymer microsphere, the Ca 2+ content in the injection water > 500 mg / L, and the Mg 2+ content > 200 mg / L. In the present invention, silicate reacts with Ca 2+ and Mg 2+ in the injection water to generate calcium silicate or magnesium silicate gel (inorganic gel), so that Ca 2+ and Mg 2+The reduction in content increases the viscosity of the polymer solution or increases the median value of the hydrated swelling particle size of the polymer microspheres, thereby enhancing the retention and fluid diversion effects in the porous medium. When directly injecting the agent in a conventional single slug, the agent remains at the core end face and it is difficult to enter the deep reservoir. However, multi-round alternating injection can gradually make the agent enter the core interior, achieving uniform retention along the way and better plugging effect.

[0030] In addition, the calcium silicate or magnesium silicate gel (inorganic gel) formed by the reaction of silicate with Ca 2+ and Mg 2+ in the injected water has good temperature and salt tolerance properties, improving the temperature and salt tolerance of the polymer-containing profile control agent, enabling the polymer-containing profile control agent to withstand a high temperature of 200 °C.

[0031] Furthermore, the present invention controls the concentrations of the polymer-containing profile control agent and silicate to increase the plugging rate after water injection and achieve the retention effect of the polymer-containing profile control agent. According to the data of the examples, the plugging rate after water injection by the method provided by the present invention is 91-95%. Brief Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 It is a relationship diagram between different sodium silicate concentrations and the volume of inorganic gel;

[0034] Figure 2 It is a relationship diagram between the viscosity and the mixing method in the polymer / sodium silicate composite gel solution with different sodium silicate concentrations;

[0035] Figure 3 It is the viscosity, viscosity loss rate and shear time in the polymer / sodium silicate composite gel solution;

[0036] Figure 4 It is the PV and pressure changes during the injection sample and subsequent water injection processes of Comparative Examples 1-2 of the present invention;

[0037] Figure 5 It is the PV and pressure changes during the injection sample and subsequent water injection processes of the composite gel solution with different sodium silicate concentrations in the comparative examples of the present invention;

[0038] Figure 6 It is the PV and pressure changes during the injection sample and subsequent water injection processes of alternating injection and overall injection;

[0039] Figure 7PV and pressure changes of polymer microsphere / sodium silicate composite systems with different sodium silicate concentrations during sample injection and subsequent water injection. Detailed implementation manners

[0040] The present invention provides a method for injecting a polymer-containing profile control agent into a core to improve its temperature and salt tolerance. The polymer-containing profile control agent is a water-soluble polymer or a water-insoluble polymer microsphere.

[0041] In the present invention, unless otherwise specified, the raw materials and equipment used are all well-known commercially available products in the art.

[0042] In the present invention, when the polymer-containing profile control agent is a water-soluble polymer, the water-soluble polymer preferably includes one of ordinary polymers, hydrophobically associating polymers, polymer surfactants, branched polymers, and other salt-resistant polymers. In the present invention, the ordinary polymer is preferably partially hydrolyzed polyacrylamide; the hydrophobically associating polymers can be classified into polyacrylamide-based, cellulose-based, polyvinyl alcohol-based, polyelectrolyte-based, block copolymer-based, natural polymer-based, fluorocarbon-based, and silicone-based according to their main chain structures, hydrophobic group types, and application fields; the polymer surfactant is preferably an alkyl-based polymer surfactant, an aryl-based polymer surfactant, a fluorocarbon-based polymer surfactant, or a silicone-based polymer surfactant; the branched polymer is preferably a star polymer, a comb polymer, a dendrimer, or a hyperbranched polymer.

[0043] In the present invention, when the polymer-containing profile control agent is a water-soluble polymer, the method for injecting the polymer-containing profile control agent into the core includes: mixing the polymer-containing profile control agent, silicate, and first injection water to form a polymer-containing profile control agent-silicate composite gel solution;

[0044] Alternately injecting the polymer-containing profile control agent-silicate composite gel solution and second injection water into the core.

[0045] The present invention mixes the polymer-containing profile control agent, silicate, and first injection water to form a polymer-containing profile control agent-silicate composite gel solution.

[0046] In the present invention, the Ca 2+ content in the first injection water > 500 mg / L. In the detailed implementation manners, the Ca 2+ content in the first injection water can be 500 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, or 1000 mg / L; the Mg 2+ content in the first injection water > 200 mg / L. In the detailed implementation manners, the Mg 2+ content in the first injection water can be 200 mg / L, 300 mg / L, 500 mg / L, 600 mg / L, or 700 mg / L. The Ca 2+ and Mg 2+The calcium silicate or magnesium silicate gel (inorganic gel) formed by reacting with sodium silicate enables the overall temperature resistance of the polymer-containing profile control and displacement agent to exceed 200 °C.

[0047] In the present invention, the silicate preferably includes sodium silicate and / or potassium silicate.

[0048] In the present invention, the polymer-containing profile control and displacement agent, silicate, and the first injection water are mixed using any one of Method 1, Method 2, and Method 3.

[0049] First, Method 1 will be described below.

[0050] The Method 1 preferably includes: dissolving the polymer-containing profile control and displacement agent in part of the first injection water to obtain a polymer-containing profile control and displacement agent solution; dissolving the silicate in the remaining first injection water to obtain a silicate solution; using a drip pump to add the polymer-containing profile control and displacement agent solution and the silicate solution to the high-pressure water injection pipeline, and mixing them through a static mixer.

[0051] The present invention has no special requirements for the concentrations of the polymer-containing profile control and displacement agent solution and the silicate solution, as long as the concentration requirements of the polymer-containing profile control and displacement agent and the silicate in the polymer-containing profile control and displacement agent-silicate composite gel solution are met.

[0052] In the present invention, the Method 2 preferably includes: dissolving the polymer-containing profile control and displacement agent in the first injection water to obtain a polymer-containing profile control and displacement agent solution; using a drip pump to add the polymer-containing profile control and displacement agent solution to the high-pressure water injection pipeline, and adding the silicate to the high-pressure water injection pipeline, and mixing them through a static mixer.

[0053] In the present invention, the Method 3 preferably includes: dissolving the silicate in the first injection water to obtain a silicate solution; using a drip pump to add the silicate solution to the high-pressure water injection pipeline, and adding the polymer-containing profile control and displacement agent to the high-pressure water injection pipeline, and mixing them through a static mixer.

[0054] In the present invention, the mixing speed in Method 1, Method 2, and Method 3 is preferably 200 - 500 rpm. In specific embodiments, the mixing speed is preferably 200 rpm, 300 rpm, 400 rpm, or 500 rpm; the shearing time is preferably 2 - 4 h. In specific embodiments, the shearing time of the mixing can be 2 h, 2.5 h, 3 h, 3.5 h, or 4 h.

[0055] In the present invention, the mass concentration of the polymer-containing profile control and displacement agent in the polymer-containing profile control and displacement agent-silicate composite gel solution is preferably 0.01 - 0.30%. In specific embodiments, the mass concentration of the polymer-containing profile control and displacement agent in the polymer-containing profile control and displacement agent-silicate composite gel solution can be 0.01%, 0.05%, 0.1%, 0.2%, or 0.30%.

[0056] In the present invention, the mass concentration of silicate in the polyacrylamide profile control agent-silicate composite gel solution is preferably 0.01-10%. In specific embodiments, the mass concentration of silicate in the polyacrylamide profile control agent-silicate composite gel solution can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5% or 10%.

[0057] After obtaining the polyacrylamide profile control agent-silicate composite gel solution, the present invention alternately injects the polyacrylamide profile control agent-silicate composite gel solution and the second injection water into the core.

[0058] In the present invention, the Ca 2+ content in the second injection water > 500 mg / L, and the Mg 2+ content in the second injection water > 200 mg / L.

[0059] In the present invention, the volume ratio of the polyacrylamide profile control agent-silicate composite gel solution to the second injection water is preferably 1-2:1. In specific embodiments, the volume ratio of the polyacrylamide profile control agent-silicate composite gel solution to the second injection water can be 1:1 or 2:1.

[0060] In the present invention, the ratio of the total injection volume of the polyacrylamide profile control agent-silicate composite gel solution to the pore volume of the core is preferably 3-8:1. In specific embodiments, the ratio of the total injection volume of the polyacrylamide profile control agent-silicate composite gel solution to the pore volume of the core can be 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1.

[0061] In the present invention, the number of times of alternate injection is preferably 4-8 times. In specific embodiments, the number of times of alternate injection can be 4 times, 5 times, 6 times, 7 times or 8 times. In specific embodiments of the present invention, the polyacrylamide profile control agent-silicate composite gel solution is preferably injected into the core, and the volume of the polyacrylamide profile control agent-silicate composite gel solution injected at one time is controlled to be < 1 times the pore volume of the core. After stopping the injection of the polyacrylamide profile control agent-silicate composite gel solution, water injection into the core is started; when injecting water, the volume of water injected at one time is controlled to be the same as the volume of the polyacrylamide profile control agent-silicate composite gel solution injected. From the start of injecting the polyacrylamide profile control agent-silicate composite gel solution to the stop of water injection, it is one alternate injection. And so on, until the total injection volume of the polyacrylamide profile control agent-silicate composite gel solution reaches 3-8 times the pore volume of the core, the alternate injection is stopped.

[0062] In the present invention, when the polyacrylamide profile control agent is a water-insoluble polymer microsphere, the method preferably includes: mixing the polyacrylamide profile control agent and injection water to form a polyacrylamide profile control agent suspension;

[0063] mixing the silicate and water to form a silicate solution;

[0064] Inject the polymer flooding agent suspension and the silicate solution into the core alternately.

[0065] The present invention has no special requirements for the mixing method, and common technical methods in the art can be used.

[0066] In the present invention, the Ca content in the injection water 2+ > 500 mg / L, and the Mg content in the injection water 2+ > 200 mg / L. In the present invention, the water is preferably softened water, and the Ca content in the softened water 2+ is preferably < 40 mg / L, and the Mg content 2+ is preferably < 30 mg / L. When the water is injection water, the Ca content in the injection water 2+ > 500 mg / L, and the Mg content 2+ > 200 mg / L.

[0067] In the present invention, the mass concentration of the polymer flooding agent in the polymer flooding agent suspension is preferably 0.01 - 0.30%; in specific embodiments, the mass concentration of the polymer flooding agent in the polymer flooding agent suspension can be 0.01%, 0.05%, 0.1%, 0.2% or 0.30%. In the present invention, the mass concentration of the silicate in the silicate solution is 0.01 - 10%, and in specific embodiments, the mass concentration of the silicate in the silicate solution can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 5% or 10%.

[0068] In the present invention, the volume ratio of the polymer flooding agent suspension to the silicate solution is preferably 1 - 2:1, and in specific embodiments, the volume ratio of the polymer flooding agent suspension to the silicate solution can be 1:1 or 2:1.

[0069] In the present invention, the ratio of the total injection volume of the polymer flooding agent suspension to the pore volume of the core is preferably 2 - 5:1, and in specific embodiments, the ratio of the total injection volume of the polymer flooding agent suspension to the pore volume of the core can be 2:1, 3:1, 4:1 or 5:1.

[0070] In the present invention, when the polymer flooding agent is a water-insoluble polymer microsphere, the polymer flooding agent suspension is preferably injected into the core first, and the volume of each injection of the polymer flooding agent suspension and the volume of the silicate solution are controlled, and the volume of each injection of the polymer flooding agent suspension < 1 times the pore volume of the core, until the total injection volume of the polymer flooding agent suspension is 2 - 5 times the pore volume of the core, and then stop the alternate injection. From the start of injecting the polymer flooding agent suspension to the stop of injecting the silicate solution, it is considered as 1 alternation.

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in combination with specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Any modifications, equivalent replacements, improvements, etc. made to the embodiments of the present invention based on the technical essence and general principles of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0072] Polymer flooding agent-silicate composite gel solution

[0073] Preparation of inorganic gel

[0074] Mix sodium silicate (Na2SiO3·9H2O) with the injection water of SZ36-1 oilfield to prepare a sodium silicate solution with a concentration of 500 mg / L (1000 mg / L, 1500 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L, or 5000 mg / L), and let it stand for 30 min to obtain an inorganic gel.

[0075] The reaction between sodium silicate and divalent metal ions in solvent water can generate an inorganic gel, whose density is greater than that of water and whose appearance is milky white. At the initial stage and under low-concentration conditions, the sizes of inorganic gel aggregates are small, and they are in a suspended state in water. After that, the aggregates will coalesce and form precipitates.

[0076] Compare the relationship between the concentration of sodium silicate and the volume of the obtained inorganic gel to obtain Table 1.

[0077] Table 1 Relationship between sodium silicate concentration and inorganic gel volume

[0078] Concentration (mg / L) 500 1000 1500 2000 3000 4000 5000 Gel volume (mL) 6.0 9.0 15.0 19.0 26.0 35.0 37.0

[0079] Observe the appearance and morphology of the inorganic gel, as Figure 1 shown. It can be seen from Table 1 and Figure 1 that as the concentration of sodium silicate increases, the volume of the generated inorganic gel increases. When the concentration is greater than 4000 mg / L, the increment of the generated inorganic gel tends to level off. It shows that the maximum volume of the generated inorganic gel depends on the content of divalent metal ions in the solvent water, that is, the higher the concentration of divalent metal ions, the larger the maximum volume of the generated inorganic gel and the stronger the plugging ability. Further analysis shows that the inorganic gel is composed of calcium silicate hydrate C-S-H, and the precipitate mainly reduces the pore throat size and plugs the pores by attaching to the surface of the core to form a coating, thereby achieving the profile control and displacement effect. Therefore, the larger the gel volume generated, the stronger the plugging ability.

[0080] Preparation of polymer flooding agent-silicate composite gel solution

[0081] Polymer solution / sodium silicate solution composite gel solution

[0082] Mix the "high molecular weight" polymer ((C3H5NO) n , with a relative molecular weight of (2000 - 2500)×10 4 , from CNOOC Tianjin Branch with an effective content of 90%) with the injection water of SZ36 - 1 oilfield to prepare a polymer solution with a concentration of 4000 mg / L;

[0083] Mix the sodium silicate solution (sodium silicate and injection water) with a concentration of 2000 mg / L (4000 mg / L, 6000 mg / L, 8000 mg / L or 10000 mg / L) and the polymer solution, control the volume ratio of the sodium silicate solution to the polymer solution to be 1:1, and the mass ratio of sodium silicate to polymer to be 1:2, 1:1, 1.5:1, 2:1 and 2.5:1. Stir with a magnetic stirrer at 300 rpm for 2.5 h to obtain a polymer - containing profile control and displacement agent - silicate composite gel solution, denoted as the polymer solution / sodium silicate solution composite gel solution.

[0084] The ion composition of the injection water in SZ36 - 1 oilfield is shown in Table 2.

[0085] Table 2 Ion composition of the injection water in SZ36 - 1 oilfield

[0086]

[0087] Polymer solution / sodium silicate dry powder composite gel solution

[0088] Mix the "high molecular weight" polymer ((C3H5NO) n , with a molecular weight of (2000 - 2500)×10 4 , from CNOOC Tianjin Branch with an effective content of 90%) with the injection water of SZ36 - 1 oilfield to prepare a polymer solution with a concentration of 2000 mg / L;

[0089] Mix the 2000 mg / L polymer solution with sodium silicate dry powder, the concentration of sodium silicate is 1000 mg / L (2000 mg / L, 3000 mg / L, 4000 mg / L or 5000 mg / L), control the mass ratio of sodium silicate to polymer to be 1:2, 1:1, 1.5:1, 2:1 and 2.5:1. Stir with a magnetic stirrer at 300 rpm for 2.5 h to obtain a polymer - containing profile control and displacement agent - silicate composite gel solution, denoted as the polymer solution / sodium silicate dry powder composite gel solution.

[0090] Polymer dry powder / sodium silicate solution composite gel solution

[0091] Injecting water was used to prepare sodium silicate solutions (1000 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L, and 5000 mg / L) respectively, and then polymer dry powder (2000 mg / L) was added. The mass ratio of polymer to sodium silicate was controlled at 1:2, 1:1, 1.5:1, 2:1, and 2.5:1. A magnetic stirrer was used to stir at 300 rpm for 2.5 h to obtain a polymer-containing profile control and flooding agent - silicate composite gel solution, denoted as polymer dry powder / sodium silicate solution composite gel solution.

[0092] Using a Brookfield viscometer, the viscosities of the polymer-containing profile control and flooding agent - silicate composite gel solutions obtained by three different mixing methods were compared with the mixing methods and sodium silicate concentrations to obtain Figure 2 . From Figure 2 it can be seen that among the three mixing methods, the viscosity of the polymer dry powder / sodium silicate solution composite gel solution is relatively high, and the viscosities of the other methods are relatively low. When the sodium silicate concentration is greater than 3000 mg / L, the growth rate of the composite gel solution viscosity shows an accelerating trend. It is considered that "the mixing method of the polymer dry powder / sodium silicate solution composite gel solution is to first dissolve sodium silicate in water. During this period, sodium silicate reacts with calcium and magnesium ions in the injected water, resulting in a decrease in calcium and magnesium ions in the injected water. The polymer dry powder is dispersed, swollen, and dissolved in water with low (or no) calcium and magnesium ions. Therefore, the viscosity of the polymer dry powder / sodium silicate solution composite gel solution is relatively high.

[0093] Different shear times

[0094] Mix the "high molecular weight" polymer ((C3H5NO) n , with a molecular weight of 2000 - 2500×10 4 , from CNOOC Tianjin Branch, with an effective content of 90%) with the injection water of SZ36 - 1 oilfield to prepare a polymer solution with a concentration of 2000 mg / L.

[0095] Mix 1000 mg / L sodium silicate solution and 2000 mg / L polymer solution, and use a Waring blender to shear at 5000 rpm for 5 s (10 s, 20 s, 30 s, 50 s, and 60 s) to obtain a polymer-containing profile control and flooding agent - silicate composite gel solution.

[0096] By increasing the shear force, the influence of the porous medium of the core on the viscosity of the polymer-containing profile control and flooding agent - silicate composite gel solution during the injection and storage process was simulated. Using a Brookfield viscometer, the viscosity and shear time of the polymer-containing profile control and flooding agent - silicate composite gel solution prepared in Example 4 were compared to obtain Figure 3 . From Figure 3It can be seen that as the shear time increases, the sizes of the polymer molecular aggregates and inorganic gel aggregates in the polymer flooding agent-silicate composite gel solution after shearing decrease, and the mixing effect and injectability of the two are improved. When the shear time is less than 15 s, the inorganic gel and the polymer solution are less affected by the shearing action, and the viscosity loss rate of the composite gel solution is relatively low.

[0097] The "high molecular weight" polymer ((C3H5NO) n , with a molecular weight of (2000 - 2500)×10 4 , from CNOOC Tianjin Branch, with an effective content of 90%) was mixed with the injection water of SZ36-1 oilfield to prepare a polymer solution with a concentration of 2000 mg / L. The measured viscosity was 11.9 mPa·s, and after shearing at 5000 rpm for 15 s using a Waring blender, the viscosity was 3.3 mPa·s, with a viscosity decrease of 9.6 mPa·s.

[0098] A 1000 mg / L sodium silicate solution and a 2000 mg / L polymer solution were mixed, and the measured viscosity was 13.5 mPa·s. After shearing at 5000 rpm for 15 s using a Waring blender, the viscosity was 7.4 mPa·s, with a viscosity decrease of only 6.1 mPa·s. This indicates that the "high molecular weight" polymer shows enhanced salt resistance after being added to the sodium silicate solution.

[0099] Example 1

[0100] A polymer flooding agent-silicate composite gel solution was prepared from a 2000 mg / L polymer solution and a 500 mg / L sodium silicate solution, with a volume ratio of the sodium silicate solution to the polymer solution of 1:1. The polymer flooding agent-silicate composite gel solution and the injection water were alternately injected into the core at an injection rate of 0.3 mL / min, with a volume ratio of the polymer flooding agent-silicate composite gel solution to the injection water of 1:1. The total injection volume of the composite gel solution was 5 PV (PV is the pore volume multiple of the core, with the core pore volume as the unit one, and all injection liquid volumes are calculated according to the core volume multiple). After the alternating injection of the composite gel solution and the injection water into the core was completed, water was continuously injected into the core alone.

[0101] The core was a quartz sand epoxy resin cemented artificial columnar core, with core geometric dimensions: diameter × length = 2.5 cm × 10 cm. The permeability details are shown in the relevant experimental result analysis.

[0102] Comparative Example 1

[0103] A 2000 mg / L polymer solution was injected into the core at 0.3 mL / min, and the total injection volume of the polymer solution was 5 PV. After the injection of the polymer solution sample was completed, water was continuously injected into the core.

[0104] Comparative Example 2

[0105] Prepare a polymer flooding and profile control agent - silicate composite gel solution by mixing a 4000 mg / L polymer solution with a sodium silicate solution at different concentrations (200 mg / L, 600 mg / L, or 1000 mg / L). The volume ratio of the sodium silicate solution to the polymer solution is 1:1. Inject the composite gel solution into the core as a whole at a rate of 0.3 mL / min, and the total injection volume of the composite gel solution is 5 PV. After the injection of the composite gel solution is completed, continue to inject water into the core.

[0106] Measure the permeability K of the core g , the resistance coefficient (F R ) after injecting the composite gel solution, and the residual resistance coefficient (F RR ) and plugging rate measured by continuing to inject water after injecting the composite gel solution. Summarize the permeability K g , resistance coefficient (F R ), residual resistance coefficient (F RR ) and plugging rate data measured in Example 1 and Comparative Examples 1 - 2 to obtain Table 3.

[0107] Table 3 Relevant parameters of Example 1 and Comparative Examples 1 - 2

[0108]

[0109] It can be seen from Table 3 that compared with the polymer solution, the composite gel solution has larger resistance coefficient, residual resistance coefficient and plugging rate. Compare the PV and pressure changes during the injection and subsequent water injection processes of Comparative Examples 1 - 2 to obtain Figure 4 . It can be seen from Figure 4 that when injecting the polymer solution, the pressure change in the core is small; when injecting the composite gel solution, the core pressure increases with the increase of the injection volume of the composite gel solution, but in the subsequent water injection stage, the pressure drop rate is fast, but the final core pressure is still greater than that of the polymer solution. It is considered that in addition to the polymer solution, the composite gel solution also contains inorganic gel, and the overall retention level of the two is relatively high. At the same time, the retention amount remains at a relatively high level at the end of the subsequent water flooding, so the resistance coefficient, residual resistance coefficient and plugging rate are relatively large.

[0110] It can be seen from the data of Comparative Example 2 in Table 3 that with the increase of the sodium silicate concentration, the resistance coefficient increases, while the residual resistance coefficient and plugging rate show a trend of "first increasing and then decreasing". It is considered that when the sodium silicate concentration is relatively low, the total amount of inorganic gel generated in the composite gel solution is relatively low, and the retention amount of inorganic gel in the core is proportional to the sodium silicate concentration. Summarize the PV and pressure changes during the injection and subsequent water injection processes of Comparative Example 2 to obtain Figure 5 . It can be seen from Figure 5It can be seen that at the same injection volume, as the concentration of sodium silicate increases, the pressure gradually increases. However, during the subsequent water injection process, the pressure first increases and then decreases. This indicates that when the concentration of sodium silicate increases and reaches a relatively high level (exceeding 300 mg / L), not only is the total amount of inorganic gel relatively large but also the aggregate size is larger, resulting in a poorer compatibility with the core pores. The inorganic gel is retained at the core end face (and the amount retained in the deep part of the core decreases accordingly), so the injection pressure is relatively high and the resistance coefficient is relatively large. During the subsequent water flooding stage, water enters the core interior from the area lacking retention substances at the core end face, so the injection pressure is relatively low, and the residual resistance coefficient and plugging rate are relatively small. Data prove that when the dosage of sodium silicate is relatively large, the method of alternating injection can better retain the plugging effect.

[0111] As can be seen from Table 3, when the composite gel solution and injection water are injected into the core by the alternating injection method, the plugging rate reaches the maximum, 95.2%. Combining Figure 6 Based on the PV and pressure changes during the sample injection and subsequent water injection processes with different injection methods, compared with the overall injection of the composite gel solution slug, the residual resistance coefficient and plugging rate are higher when alternating injection with water. It is analyzed that when injecting the slug as a whole, the inorganic gel is likely to be retained at the injection end face of the core and cause difficulties in liquid injection. Different from the overall injection, during alternating injection, the water slug can dilute the partially retained inorganic gel at the injection end and push it into the deep part of the core and retain it, so the residual resistance coefficient and plugging rate of alternating injection are larger.

[0112] The composite gel solution obtained in the present invention, compared with the conventional polymer-containing profile control agent, the inorganic gel and polymer solution or polymer microspheres in the composite gel solution are retained together in the core, increasing the resistance coefficient, residual resistance coefficient and plugging rate. Compared with the overall injection, during alternating injection, water can push the partially retained microspheres and inorganic gel in the injection end or nearby area of the core into the deep part of the core, resulting in an increase in the residual resistance coefficient and plugging rate.

[0113] Polymer microsphere / sodium silicate composite system

[0114] Preparation of polymer microsphere / sodium silicate composite system

[0115] Mix the polymer microspheres (CNOOC Tianjin Branch, effective content 30%) with the injection water of SZ36-1 oilfield to prepare a polymer microsphere solution with a concentration of 6000 mg / L;

[0116] Mix the sodium silicate solution with a concentration of 1000 mg / L (2000 mg / L, 4000 mg / L, 6000 mg / L, 8000 mg / L or 10000 mg / L) and the polymer microsphere solution, and the volume ratio of the sodium silicate solution to the polymer microsphere solution is 1:1. Stir evenly to obtain the polymer microsphere / sodium silicate composite system.

[0117] Median diameter of microspheres at the initial stage of the test and at 7 d. The results show that with the increase in the concentration of sodium silicate in the solvent water, the median diameter of the microspheres increases. When the concentration of sodium silicate is less than 3000 mg / L, the microspheres can maintain a spherical shape; otherwise, the oil film of the microspheres will rupture. The initial median diameter of the microspheres is 3.52 μm. When the concentrations of sodium silicate are 500 mg / L, 1000 mg / L, and 2000 mg / L respectively, the median diameters of the microspheres are 4.87 μm, 8.66 μm, and 9.74 μm respectively.

[0118] Example 2

[0119] Mix the polymer microspheres (CNOOC Tianjin Branch, effective content 30%) with the injection water of SZ36-1 oilfield to prepare a polymer microsphere solution with a concentration of 3000 mg / L;

[0120] Mix sodium silicate (Na2SiO3·9H2O) with softened water to prepare a sodium silicate solution with a concentration of 300 mg / L (500 mg / L, 700 mg / L, or 900 mg / L);

[0121] Alternately inject the 3000 mg / L polymer solution and the sodium silicate solution with different concentrations into the core for 5 cycles, 0.04 PV of microspheres and 0.02 PV of sodium silicate solution each time.

[0122] Comparative Example 3

[0123] Alternately inject the 3000 mg / L polymer solution and the injection water into the core for 5 cycles, 0.04 PV of microspheres and 0.02 PV of injection water each time.

[0124] Test the permeability K of the core g and the resistance coefficient (F R ) after injecting the composite system, and the residual resistance coefficient (F RR ) and the plugging rate measured by continuous water injection after injecting the composite system. Summarize the permeability K g , resistance coefficient (F R ), residual resistance coefficient (F RR ) and plugging rate data measured in Application Example 2 and Comparative Application Example 3 to obtain Table 4.

[0125] Table 4 Relevant parameters of Example 2 and Comparative Example 3

[0126]

[0127] As can be seen from Table 4, compared with the alternate injection of "polymer microspheres and injected water", the resistance coefficient, residual resistance coefficient and plugging rate of the alternate injection of "polymer microspheres and sodium silicate solution" are larger. It is analyzed that due to the relatively high core permeability and large pore throat size, the retention level of polymer microspheres is relatively low, and the "resistance increasing and permeability decreasing" effect is poor. In the alternate injection of "polymer microspheres and sodium silicate solution", on the one hand, sodium silicate reacts with calcium and magnesium ions in the polymer microsphere carrying fluid (injected water) to form inorganic gel, and the synergistic retention of the two enhances the "resistance increasing and permeability decreasing" effect. On the other hand, the decrease in the concentration of calcium and magnesium ions in the carrying fluid increases the hydration swelling multiple of the microspheres, increasing the trapping and retention level of the microspheres in the core, that is, the "resistance increasing and permeability decreasing" effect, so the resistance coefficient, residual resistance coefficient and plugging rate are larger. With the increase of the sodium silicate concentration, the resistance coefficient increases, while the residual resistance coefficient and plugging rate show a trend of "increasing first and then decreasing". It is analyzed that when the sodium silicate concentration is lower than 900 mg / L, the amount of inorganic gel generated is less and the aggregate size is also smaller. Its compatibility with the core pores is better, and the seepage resistance increases with the increase of the sodium silicate concentration. Combining Figure 7 Analysis of the PV and pressure changes during the injection of polymer microsphere / sodium silicate composite systems with different concentrations and subsequent water injection shows that when the sodium silicate concentration reaches 900 mg / L, the amount of inorganic gel generated and the aggregate size increase significantly. Its compatibility with the core pores becomes poor, resulting in an increase in the retention amount of inorganic gel at the injection end face of the core and a rapid increase in the injection pressure. In the subsequent water flooding stage, water enters the core from the area where there is no retention at the core end face, so the injection pressure is relatively low, and the residual resistance coefficient and plugging rate are small.

[0128] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the temperature and salt resistance of polymer-containing displacement agents for injection into cores, characterized in that: The polymer-containing displacement agent is a water-soluble polymer or a water-insoluble polymer microsphere; When the polymer-containing displacement agent is a water-soluble polymer, the method The following steps are involved: Mixing the polymer-containing displacement agent, silicate and first injection water to form a polymer-containing displacement agent-silicate composite gel solution; Alternately injecting the polymer-containing displacement agent-silicate composite gel solution and the second injection water into the core; When the polymer-containing displacement agent is a water-insoluble polymer microsphere, the method The following steps are involved: Mixing the polymer-containing displacement agent and injection water to form a suspension of the polymer-containing displacement agent; mixing silicate and water to form a silicate solution; Alternately injecting the polymer-containing displacement agent suspension and the silicate solution into the core; When the polymer-containing displacement agent is a water-soluble polymer, the Ca in the first injection water and the second injection water 2+ Content>500mg / L, Mg 2+ content>200mg / L; or when the polymer-containing displacement agent is a water-insoluble polymer microsphere, the Ca in the injected water 2+ Content>500mg / L, Mg 2+ Content>200mg / L.

2. The method according to claim 1, characterized in that The mass concentration of the polymer-containing displacement agent in the polymer-containing displacement agent-silicate composite gel solution is 0.01-0.30%; The mass concentration of silicate in the polymer-containing displacement agent-silicate composite gel solution is 0.01-10%.

3. The method according to claim 1 or 2, characterized in that: When the polymer-containing displacement agent is a water-soluble polymer, the ratio of the total injected volume of the polymer-containing displacement agent-silicate composite gel solution to the pore volume of the core is 3-8:1; the volume ratio of the polymer-containing displacement agent-silicate composite gel solution to the second injected water is 1-2:

1.

4. The method according to claim 1 or 2, characterized in that: The polymer-containing displacement agent, silicate and first injection water are mixed using any one of method 1, method 2 and method 3: The method comprises: dissolving a polymer-containing displacement agent in a portion of first injected water to obtain a polymer-containing displacement agent solution; dissolving silicate in the remaining first injected water to obtain a silicate solution; adding the polymer-containing displacement agent solution and the silicate solution to a high-pressure water injection pipeline by using a drip pump, and mixing them through a static mixer; The second method comprises: dissolving a polymer-containing control and displacement agent in first injection water to obtain a polymer-containing control and displacement agent solution; adding the polymer-containing control and displacement agent solution to a high-pressure water injection pipeline by using a drip pump, adding silicate to the high-pressure water injection pipeline, and mixing through a static mixer; The third method comprises: dissolving silicate in first injected water to obtain a silicate solution; adding the silicate solution to a high-pressure water injection pipeline by using a drip pump, adding a polymer-containing displacement agent to the high-pressure water injection pipeline, and mixing through a static mixer.

5. The method according to claim 4, characterized in that The mixing rotation speed in the method 1, the method 2 and the method 3 is 200-500 rpm, and the shearing time is 2-4 hours.

6. The method according to claim 1, characterized in that The mass concentration of the polymer-containing displacement agent in the polymer-containing displacement agent suspension is 0.01 to 0.30%; The mass concentration of silicate in the silicate solution is 0.01-10%.

7. The method according to claim 1 or 6, characterized in that: When the polymer-containing displacement agent is polymer microspheres, the ratio of the total injected volume of the polymer-containing displacement agent suspension to the pore volume of the core is 2-5:1; the volume ratio of the polymer-containing displacement agent suspension to the silicate solution is 1-2:

1.

8. The method according to claim 1, 2 or 6, characterized in that: The silicate includes sodium silicate and / or potassium silicate.

9. The method according to claim 1, characterized in that: When the polymer-containing displacement agent is a water-soluble polymer or a water-insoluble polymer microsphere, the number of times of the alternating injection is 4 to 8 times.

10. The method according to claim 1, characterized in that When silicate and water are mixed, the water used is softened water or injection water. When softened water is used, Ca 2+ Content <40mg / L, Mg 2+ Content <30mg / L, when it is injected water, Ca 2+ Content>500mg / L, Mg 2+ Content>200mg / L.

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