Nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs and preparation method thereof

Abstract

The present invention provides a nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs and a preparation method thereof, comprising enzymes, polysorbate, modified nano-ZnO, Span, modified nano-SiO2, sodium hydroxide, anhydrous ethanol and water. The nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs is an organic fusion of enzymes, esters and nanotechnology, which not only improves the adsorption capacity of rocks to crude oil from the formation matrix, but also disperses oil and water into tiny droplets, thereby increasing the fluidity of oil and water in pores and ducts, achieving water well injection and oil well production increase. When injected, the nano-dispersed storage enhancer can be used alone or in combination with a nano-pressure-reducing storage enhancer. The present invention utilizes oil layer microscopic seepage technology and is the first to use enzymes, esters and nanomaterials to solve the problem of difficult micropore seepage in low-permeability water-sensitive oil reservoirs from the formation matrix.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to a nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs and a preparation method thereof. Background Art

[0002] Because low-permeability, water-sensitive reservoirs contain water-sensitive minerals or have small pores, clay absorbs water and expands during the waterflooding phase, resulting in pore throat shrinkage. This can lead to water wells failing to inject water or insufficiently injecting water, resulting in no oil production, low production capacity, and rapid energy decline. This leads to declining oilfield production and increasing production costs year after year. The main targeted recovery methods, including water flooding, active water flooding, fracturing, air flooding, and periodic well drilling, are limited by their cost and production cycle, and cannot meet the needs of efficient oilfield development.

[0003] The key to this invention is how to modify the reservoir's seepage conditions, increase reservoir permeability, improve fluid mobility, and better utilize the remaining oil. Our nano-dispersed reservoir enhancer for low-permeability, water-sensitive reservoirs, when injected into the formation, effectively increases the well's oil control radius, enhances reservoir imbibition efficiency, improves fluid conditions, and increases oilfield productivity. The technical approach is as follows:

[0004] First, according to the capillary seepage mechanics formula, it can be concluded that what needs to be done to reduce the capillary force is: reduce the interfacial tension between the two fluids, change the solid-liquid contact angle, and increase the capillary radius.

[0005] Capillary force formula p=2σcosθ / r

[0006] Where P is the capillary force, σ is the interfacial tension between the two fluids, θ is the contact angle of the system, and r is the capillary radius.

[0007] (1) P is inversely proportional to the capillary radius r. The smaller r is, the larger P is.

[0008] (2) P is proportional to σ. The larger σ is, the larger P is.

[0009] (3) P is proportional to cosθ. When θ < 90°, the capillary pores are hydrophilic, the capillary force P is positive, and the water surface rises spontaneously. When θ > 90°, the capillary pores are lipophilic, the capillary force Pc is negative, and the water surface drops spontaneously.

[0010] Second, a large amount of research data has proven that the increase in production capacity through throughput production and pressure drive is influenced by three factors in the following order: ability to change rock wettability > reducing oil-water interfacial tension > ability to emulsify and disperse crude oil.

[0011] Third, by reducing the water film thickness (increasing the capillary radius), the fluid seepage resistance can be greatly reduced.

[0012] Certain nanoparticles are adsorbed to form a nanofilm, reducing the contact area between the water phase and the rock, and the thickness of the water film becomes thinner; zeta potential theory calculations found that after the nanoparticles are injected into the core, the interaction energy of crude oil on the rock surface is reduced, and the crude oil is stripped off.

[0013] Fourth, improve the self-priming ability of the capillary and reduce the surface tension of the fluid.

[0014] The phenomenon of plant nutrient solution self-absorption shows that self-absorption ability depends on the wettability of the solid and the surface tension of the liquid. The stronger the wettability of the solid (rock) surface, the greater its attraction to water; the smaller the surface tension of the liquid, the greater the relative attraction between the solid molecules inside the tubular object.

[0015] Based on the above ideas, the present invention provides a composite dispersed reserve-increasing treatment agent with enzyme ester nanoparticles as the core, which is specifically designed for low permeability water-sensitive oil reservoirs; it can achieve "one dose with multiple functions and one dose with multiple uses" and is a disruptive product with great development potential - a nano-dispersed reserve-increasing agent for low permeability water-sensitive oil reservoirs. Summary of the Invention

[0016] The purpose of the present invention is to provide a nano-dispersed reserve enhancer for low-permeability water-sensitive oil reservoirs and a preparation method thereof. After the enzyme ester nanoemulsion enters the formation, its hydrophobic nano-particles can use their advantages to strongly adhere to the rock wall to peel off the water film. The enzymes and esters carried in the outer layer can change the crystallization state of paraffin and effectively reduce the interaction between colloid and asphaltene molecules, break up large molecular clusters, disperse the crude oil, present an oil-in-water state, improve the fluid flow capacity, and increase the ultimate recovery rate of the oil field.

[0017] A nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs comprises enzyme, polysorbate, modified nano-ZnO, Span, nano-SiO2, sodium hydroxide, anhydrous ethanol and water.

[0018] Preferably, the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs described in the present invention comprises the following components, calculated by mass percentage: 30%-35% of enzyme, 9%-12% of polysorbate, 0.1%-0.5% of modified nano-ZnO, 0.6-1.2% of Span, 0.2%-0.4% of modified nano-SiO2, 0.5%-1% of sodium hydroxide, 1.5%-5% of anhydrous ethanol, and the balance being water.

[0019] Preferably, the enzyme of the present invention is at least one of polyphenol oxidase, catalase, and lipase, which can reduce the interaction between hydrocarbon, wax, and colloid asphaltene molecules, break up molecular clusters, and improve the fluidity of crude oil in the pores and pore throats of low permeability water-sensitive reservoirs.

[0020] Preferably, the polysorbate is an organic compound with the chemical formula C 64 H 124 O26 It is a non-ionic surfactant, at least one of polysorbate 21-81, and can be mixed with other surfactants. It has high stability, good water solubility, and is non-toxic and harmless.

[0021] Preferably, the Span is a compound having the chemical formula C 24 H 44 O6 is a non-ionic surfactant, which is at least one of Span 60-85. It can be mixed with other surfactants. It has high stability and can be well dispersed in oil, paraffin and organic solvents. It is dispersed in hot water and is non-toxic and harmless.

[0022] Preferably, the modified nanomaterial is a modified hyperbranched nanomaterial that can smoothly enter the low permeability reservoir, including modified nano-SiO2 particles and modified nano-ZnO particles, wherein the modified nano-SiO2 particles are an amorphous white powder nanomaterial modified with SiO2 as the main component, and the particle size is 5-20nm, and the modified nano-ZnO particles are white hexagonal or spherical particles modified with ZnO as the main component, with an average particle size of 50nm.

[0023] Preferably, the water is purified water that meets the specifications of the national standard GB6682-2008.

[0024] The present invention also provides a method for preparing the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs, comprising the following steps:

[0025] Step (1) adding the formulated amount of enzyme and polysorbate to a large stirred reactor at room temperature, stirring uniformly at 120 rpm and 10-30° C. for 1-2 hours;

[0026] Step (2) Place modified nano-ZnO, modified nano-SiO2, sodium hydroxide, Span, and anhydrous ethanol in a small stirred reactor according to the formula amount, and stir and react at a constant temperature of 80°C and a speed of 2000 rpm for 10 minutes;

[0027] Step (3) The reactants in the small stirred reactor are quickly poured into the large stirred reactor, and the mixture is stirred uniformly at a speed of 120 rpm and a constant temperature of 30°C for another 2 hours. Water is added according to the formula amount and stirring is continued for 30 minutes. After that, heating is stopped and the mixture is cooled to room temperature to obtain a low permeability water-sensitive oil reservoir nano-dispersion storage enhancer.

[0028] Preferably, in step (1), the reaction time is 1 hour.

[0029] A method for using a nano-dispersed storage-enhancing agent for low-permeability water-sensitive oil reservoirs, comprising injecting the nano-dispersed storage-enhancing agent for low-permeability water-sensitive oil reservoirs and using it in combination with a nano-pressure-reducing storage-enhancing agent, wherein the nano-pressure-reducing storage-enhancing agent comprises any one or more of enzymes, nano-SiO2 particles, polyethoxylated fatty alcohols, surface modifier S1-69, and water.

[0030] Preferably, the nano-dispersed reserve-increasing agent for low permeability water-sensitive oil reservoirs and the nano-pressure-reducing reserve-increasing agent are used in combination as follows: the nano-dispersed reserve-increasing agent for low permeability water-sensitive oil reservoirs is first injected to decompose the crude oil near the wellbore, and then the nano-pressure-reducing reserve-increasing agent is injected to remove blockage and increase reserves in the deep area.

[0031] Preferably, the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs is suitable for low permeability water-sensitive oil reservoirs.

[0032] The innovation of the present invention is:

[0033] The present invention utilizes oil layer microscopic seepage technology and is the first to use enzymes, esters and nanomaterials to solve the problem of micropore seepage in low permeability water-sensitive oil reservoirs from the formation matrix;

[0034] Modified nanoparticles, carrying OH-, can easily pin to the rock surface, reduce the water film thickness, and increase the pore throat radius. The enzymes and esters in the nano outer layer can change the flow state of underground fluids, thereby achieving the effect of increasing water well injection and oil well production.

[0035] The multi-property material fusion technology used in the present invention is to fuse the multi-property materials to form an emulsion that is temperature-resistant, salt-resistant, large in quantity, has a wide range of action, and is well compatible with oilfield water. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a composition diagram of the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs of the present invention;

[0037] Figure 2 This is a compatibility test diagram of the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula described in Example 2 in Experimental Example 1 of the present invention before it is put into the well;

[0038] Figure 3 This is a graph showing the effect of a rock permeability channel experiment under a 10,000x microscope using the nano-dispersed reserve enhancer for low-permeability water-sensitive oil reservoirs prepared according to the formula described in Example 2 of the present invention, with the crude oil kept at a constant temperature of 80°C and the agent concentration of 0.5%;

[0039] Figure 4 The interfacial tension of the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs prepared according to the formula described in Example 2 of the present invention was measured under the conditions of a constant crude oil temperature of 80°C and an agent concentration of 0.3%;

[0040] Figure 5 The capillary self-imbibition height of the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula described in Example 2 of the present invention is measured under the conditions of a constant crude oil temperature of 80°C and an agent concentration of 0.3%;

[0041] Figure 6 The contact angle of the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula described in Example 2 of the present invention was measured under the conditions of a constant crude oil temperature of 80°C and an agent concentration of 0.3%;

[0042] Figure 7 This is a comparison chart of the experimental effects of crude oil fluidity before and after adding the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula described in Example 2 in Experimental Example 2 of the present invention;

[0043] Figure 8 This is a diagram showing the instantaneous water injection volume after the construction of the Y12-16 well in the field application of the present invention;

[0044] Figure 9 This is a graph showing the construction effect of oil well Q20-8 in the field application of the present invention. DETAILED DESCRIPTION

[0045] The following will be a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] It should be noted that the various technical terms mentioned in the present invention are technical terms that have long been clearly known in the relevant technical field, so no further explanation will be given.

[0047] Table 1 List of manufacturers purchasing raw materials for nano-dispersed storage enhancers for low permeability water-sensitive oil reservoirs

[0048]

[0049]

[0050] Example 1

[0051] The nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in Example 1 is composed of the following raw materials, calculated by mass percentage: 30% enzyme (the enzyme in this example is catalase), 9% polysorbate, 0.1% modified nano-ZnO, 0.6% Span, 0.2% modified nano-SiO2, 0.5% sodium hydroxide, 1.5% anhydrous ethanol, and the remainder is purified water that meets the specifications of the national standard GB6682-2008.

[0052] The preparation method of the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs comprises the following steps: (1) adding 30% of catalase and 9% of polysorbate to a large stirred reactor at room temperature, and uniformly stirring the mixture at a rotation speed of 120 rpm and a temperature of 25° C. for reaction for 1 hour; (2) adding 0.1% of modified nano-ZnO, 0.2% of modified nano-SiO2, 0.5% of sodium hydroxide, and 1.5% of anhydrous ethanol to a small stirred reactor, and stirring the mixture at a constant temperature of 80° C. and a rotation speed of 2000 rpm for reaction for 10 minutes; (3) quickly pouring the reactants in the small stirred reactor into the large stirred reactor, and uniformly stirring the mixture at a rotation speed of 120 rpm and a constant temperature of 30° C. for reaction for another 2 hours, adding the remainder of purified water that meets the specifications of national standard GB6682-2008, continuing stirring for 30 minutes, stopping heating, and cooling to room temperature to obtain a low permeability water-sensitive oil reservoir nano-dispersed storage enhancer stock solution.

[0053] Example 2

[0054] The nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in Example 2 is composed of the following raw materials, calculated by mass percentage: 35% enzyme (the enzyme in this example is catalase), 12% polysorbate, 0.5% modified nano-ZnO, 1.2% Span, 0.4% modified nano-SiO2, 1% sodium hydroxide, 5% anhydrous ethanol, and the remainder is purified water that meets the specifications of the national standard GB6682-2008.

[0055] The preparation steps of the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs described in Example 2 are the same as those in Example 1.

[0056] Comparative Example 1

[0057] The preparation method of the nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in this comparative example 1 is the same as that in Example 1, except that the raw material composition is different. No enzyme is added to the nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in this comparative example 1. The nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in this comparative example 1 is composed of the following raw materials, by mass percentage: 9% polysorbate, 0.1% modified nano-ZnO, 0.8% Span, 0.2% modified nano-SiO2, 0.5% sodium hydroxide, 1.5% anhydrous ethanol, and the remainder is purified water that meets the specifications of the national standard GB6682-2008.

[0058] Comparative Example 2

[0059] The preparation method of the nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in this comparative example 2 is the same as that in Example 1, except that the raw material composition is different. No modified nanoparticles are added to the nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs described in this comparative example 2. The nano-dispersed storage enhancer is composed of the following raw materials, by mass percentage: 30% enzyme (the enzyme in this example is catalase), 9% polysorbate, 1.0% Span, 0.5% sodium hydroxide, 1.5% anhydrous ethanol, and the remainder is purified water that meets the national standard GB6682-2008.

[0060] In order to avoid wasting manpower and material resources, it is necessary to conduct crude oil experiments to verify its feasibility and determine the optimal formula and ratio before putting it into use in the well, as follows:

[0061] Experimental Example 1

[0062] Pre-well test: In Experimental Example 1, compatibility tests were conducted on the nano-dispersed storage enhancers for low permeability water-sensitive oil reservoirs described in the embodiment and the comparative example.

[0063] 500ml of crude oil and its free water (mineralization 185,000 mg / L) were placed in five beakers. The beakers were then placed in a 50°C thermostat for 60 minutes. Small amounts of the nano-dispersed storage enhancers for low-permeability, water-sensitive oil reservoirs prepared in the two examples and three comparative examples of the present invention were then slowly poured into the crude oil. After gentle stirring, the crude oil was well dispersed. After 5 minutes of stagnation, no precipitation was observed in the examples, while a small amount was observed in the comparative examples. See Table 2 for details.

[0064] The experimental results show that the low permeability water-sensitive oil reservoir nano-dispersion storage enhancer formed by the fusion of multi-property materials containing enzymes, polysorbates and modified nano-SiO2 particles in the raw materials using multi-property material fusion technology has good compatibility with oilfield water and no precipitation. Among them, the low permeability water-sensitive oil reservoir nano-dispersion storage enhancer prepared according to the formula described in Example 2 has the best compatibility effect. Figure 2 As shown ( Figure 2 The figure shows the state of the crude oil after the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula of Example 2 is mixed with crude oil and stirred and then left to stand for 5 minutes.

[0065] Table 2 Compatibility test results

[0066] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Compatibility better good Difference Poor

[0067] Experimental Example 2

[0068] Test before entering the well: The compatibility experiment in Experimental Example 1 shows that the nano-dispersed reserve enhancer for low permeability water-sensitive oil reservoirs prepared according to the formula described in Example 2 has the best effect. The modified nanoparticles contained therein carry OH- and can easily pin on the rock surface, peel off the water film, and increase the pore throat radius; and the enzymes and esters in the nano outer layer can decompose the crude oil into small droplets, making the crude oil more fluid, thereby achieving the effect of increasing water well injection and oil well production. We verified the ability of this agent to improve low permeability water-sensitive oil reservoirs and their oil and water flow conditions by adding nano-dispersed reserve enhancer to low permeability water-sensitive oil reservoirs and conducting tests on indicators such as the interfacial tension, capillary self-imbibition height, and contact angle of crude oil. As Figure 3 As shown in the figure, under a 10,000x microscope, the rock pore map before and after adding 0.5% concentration of nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs shows that the nanoparticles after adding the nano-dispersant are adsorbed and pinned on the rock to present a smooth surface distribution.

[0069] This experimental example 2 is to carry out the evaluation experiment of interfacial tension, capillary self-imbibition height, and contact angle. It mainly tests the relationship between interfacial tension, capillary self-imbibition height, and contact angle of the low permeability water-sensitive oil reservoir nano-dispersed storage enhancer prepared according to the formula described in Example 2 at different concentrations and different temperatures. The specific results are as follows:

[0070] 250 ml of crude oil was placed in a beaker and kept in a constant temperature oven at different temperatures for 60 minutes. Then, a 0.3% concentration of nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs was added. The interfacial tension, capillary self-absorption height, and contact angle of crude oil at different temperatures were measured. Table 3 shows the interfacial tension, capillary self-absorption height, and contact angle of crude oil at different temperatures. This experimental example shows that the interfacial tension of crude oil at temperatures of 60°C and above can reach 10 -2 mN / m, capillary self-imbibition height above 20mm, contact angle <30°, and can improve the core wettability from neutral to strongly water-wet. This indicates that the nano-dispersed reservoir enhancer for low permeability, water-sensitive reservoirs can strip the water film, increase the pore throat radius, and decompose the fluid into small droplets, solving the problem of micropore seepage in low permeability, water-sensitive reservoirs from the formation matrix. It also demonstrates its temperature and salt tolerance, high quantity, and wide range of effects at relatively low concentrations.

[0071] Figure 4 、 Figure 5 、 Figure 6 The results show that after adding 0.3% of the low permeability water-sensitive oil reservoir nanodispersion storage enhancer prepared according to the formula described in Example 2 to crude oil at a constant temperature of 80°C, the interfacial tension, capillary self-imbibition height and contact angle were measured. Figure 4 is the measured interfacial tension, Figure 5 To measure the capillary self-priming height, Figure 6 is the measured contact angle.

[0072] Table 3 Crude oil data at different temperatures

[0073] Temperature (℃) 90 80 70 60 Interfacial tension, mN / m 0.01 0.037 0.038 0.039 Capillary self-priming height (mm) 25 25 23 24 Contact angle° 26.69 25.6 25.55 24.6

[0074] (2) When the temperature is 60°C, 0.1%, 0.3%, and 0.5% of the low permeability water-sensitive reservoir nanodispersed storage enhancer were added to the crude oil, and the interfacial tension, capillary self-imbibition height, and contact angle of the crude oil were measured at a temperature of 45-60°C, as shown in Table 4:

[0075] Through this experimental example, it can be seen that after adding 0.5% concentration of nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs, the interfacial tension, capillary self-imbibition height, and contact angle change effects are the best, and the fluidity of crude oil is the best; the fluidity effect is as follows Figure 7 As shown: the left side of the figure shows the fluidity of crude oil, and the right side shows the fluidity of crude oil after adding 0.5% concentration of nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs. It can be clearly seen that the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs increases the fluidity of crude oil.

[0076] Table 4 Crude oil changes at different concentrations

[0077]

[0078] (3) 0.5% concentration of the agent was prepared according to the formulas described in the Example and the Comparative Example, and its effect was tested at 60°C, which reversely verified that Example 2 of the present invention is indeed the optimal formula for the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs. See Table 5 for details.

[0079] Table 5 Test results of different agents at 0.5% concentration

[0080] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Temperature (℃) 60 60 60 60 Interfacial tension after adding the agent, mN / m 0.0098 0.0071 0.156 0.233 Capillary self-priming height, mm 26 28 15 18 Contact angle, ° 27.22 28.9 26.22 35

[0081] After laboratory testing of the nano-dispersed reservoir enhancer in low-permeability, water-sensitive reservoirs to verify its interfacial tension, capillary self-imbibition height, and contact angle, it was put into field use. It was used in conjunction with a nano-pressure-reducing reservoir enhancer in water injection wells to conduct pressure-reduction and injection-increasing reservoir enhancement tests. It was also used alone in oil wells to conduct huff-and-puff production tests.

[0082] The application cases of the technical solution of this application are as follows:

[0083] On-site well application case 1:

[0084] The nano-dispersed storage-increasing agent for low-permeability water-sensitive oil reservoirs prepared in Example 2 of the present invention, which has the best effect, was selected and combined with the nano-pressure-reducing storage-increasing agent and put into use on site.

[0085] Construction oil fields:

[0086] The Moliqing Oilfield in Yitong County, Jilin Province was selected. The regional structure is located in the southwest of the Moliqing fault depression in the Yitong Basin, with an oil-bearing area of ​​41.67 km 2, geological reserves of 2710.78×10 4 t / km 2 The main characteristics of the oilfield are: poor reservoir properties, low porosity and low permeability, with an average porosity of 11.1% and an average permeability of 0.8×10 -3 μm 2 The average throat radius is 0.43-1.17μm; the clay mineral content is high, and it is highly water-sensitive and acid-sensitive; the crude oil has a high wax content, with an average wax content of 32.1%; the colloid content is 13.6%, the asphaltene content is 0.9%, and the freezing point is relatively high; during development, as water injection development begins, the pressure of the water injection wells continues to rise, the oil wells are ineffective, and the water injection and oil production development effects are affected.

[0087] The main problem faced is that more than 55% of the injection wells in the Moriqing Oilfield have an injection pressure of more than 25 MPa, and only 12% of the wells have an injection pressure of less than 20 MPa. The high injection pressure makes injection difficult, and the oil wells have long-term insufficient and ineffective fluid supply, which cannot meet the needs of rapid development.

[0088] Condition of the well before using the agent:

[0089] The water well layer data and water injection conditions before the use of the agent are shown in Tables 6 and 7. The original water injection pressure of wells 12-16 was 28 MPa, and the daily water injection volume was 20 cubic meters.

[0090] Table 6 Water well layer data before using the agent

[0091] Small layer number Perforation section (mm) Effective thickness (m) / number of layers Remark 1-2 2937.6-2968.5 9 / 5 Perforation only, no fracturing 3、6-8 2984.4-3120.1 17.6 / 5 Perforation fracturing total 26.6 / 10

[0092] Table 7 Water injection before using the reagent

[0093]

[0094] Construction method:

[0095] The staged water injection method was adopted. The nano-dispersed storage-increasing agent (Agent) for low-permeability water-sensitive oil reservoirs and the nano-pressure-reducing storage-increasing agent (B Agent) of the present invention were selected and used in combination in the water injection well. Pressure-reducing and plugging-removing injection was carried out in the first and second sections respectively. First, the nano-dispersed storage-increasing agent (Agent) for low-permeability water-sensitive oil reservoirs was injected into the second section through the oil pipe. Then, the nano-pressure-reducing storage-increasing agent (B Agent) was injected through the oil pipe. Then, the agent A and the agent B were injected into the first section through the casing. A total of 6.8 tons of agents were injected. The details are shown in Table 8:

[0096] Table 8 Construction status of Y12-16 well

[0097]

[0098] Comparison of water injection well effects before and after using the agent:

[0099] After the Y12-16 well was constructed on June 16, 2023, it was put into normal water injection. The nano-dispersed storage agent for low permeability water-sensitive reservoirs played a leading role in the water injection effect. The water injection volume was as follows: Figure 8 The field test water injection effect is shown in Table 9 below:

[0100] Table 9Y12-16 Water Well Water Injection Effect

[0101]

[0102] From Table 8, we can conclude that before construction, the second layer did not flow in at a pressure of 30 MPa, with a daily water injection of 0 cubic meters. After construction, the test stopped at a pressure of 25 MPa, and the hourly water injection rate reached 4.74 cubic meters at a pressure of 26.5 MPa (see Figure 8 The high-pressure water meter value on the left) is converted into a daily water injection capacity of 113 cubic meters, and the water injection is stable; the pressure of layer 1 before construction was 28MPa, with a daily water injection of 20 cubic meters. After construction, the test stopped at a pressure of 25MPa. At a pressure of 27MPa, the water injection rate can reach 4.47 cubic meters per hour (see Figure 8 The high-pressure water meter value on the right) is converted into a daily water injection capacity of 107 cubic meters, and the water injection is stable.

[0103] The effectiveness of the oil wells after the construction reflects the synergistic effect of the combined use of nano-dispersed reserve-increasing agent and nano-pressure-reducing reserve-increasing agent in low permeability water-sensitive reservoirs in increasing oil well production, as shown in Table 10:

[0104] The Y12-16 water well corresponds to a total of 5 oil wells. The oil well production from April to June 2023 before construction is compared with the production from July to December after construction. Before the 5 oil wells took effect, the daily liquid production was 26.2 tons and the daily oil production was 16.2 tons. After the effect came out, the daily liquid production was 33.4 tons and the daily oil production was 22.3 tons. The daily liquid production increased by 7.2 tons and the daily oil production increased by 6.1 tons. As of December 2023, the cumulative oil production increased by 375 tons.

[0105] Table 10 Effectiveness of the oil wells corresponding to Well Y12-16

[0106]

[0107] It can be seen that the synergistic effect of the nano-dispersed reserve enhancer (Agent A) and the nano-pressure-reducing reserve enhancer (Agent B) for low permeability water-sensitive reservoirs is significant. When used in combination, the fluidity of crude oil is increased, the permeability of the formation is improved, the water injection pressure of the oil field is reduced, the water injection volume is increased, and the oil production is increased. The cumulative oil production increase is 375t, with significant economic benefits.

[0108] On-site well application case 2:

[0109] The nano-dispersed reserve-enhancing agent for low-permeability water-sensitive oil reservoirs prepared in Example 2 of the present invention, which has the best effect, was selected and applied to low-permeability water-sensitive oil reservoir wells, and the bio-nano pulse energy replenishment and reserve-enhancing technology for low-permeability water-sensitive oil reservoir wells was put into use on-site.

[0110] Construction oil fields:

[0111] The Changqing Jing'an Oilfield in Jingbian County, Shaanxi Province was selected. The regional structure is located in the central part of the Ordos Basin, with an oil-bearing area of ​​26.55 km 2 , geological reserves of 785.6×10 4 The main characteristics of the oilfield are: poor reservoir properties, low porosity and low permeability, with an average porosity of 9.8% and an average permeability of 1.67×10 -3 μm 2 The average throat radius is 0.52-1.23μm; the clay mineral content is high and it is highly water-sensitive; the average wax content of crude oil is 21%; the colloid asphaltene content is 12.1%, and the freezing point is 30℃; there is no corresponding water well during development, and the oil wells rely on natural energy for extraction, and the output declines rapidly, affecting the oil production and development effect.

[0112] The main problems faced are: the well is located in an independent fault block, there are no corresponding water wells around it, the oil well has no energy replenishment, and the long-term fluid supply is insufficient, which cannot meet the needs of high-speed development.

[0113] Oil well condition before using the agent:

[0114] The oil well formation data before using the agent are shown in Table 11 and Table 12:

[0115] Table 11 Oil well layer data before using the agent

[0116] Small layer number Perforation section (mm) Effective thickness (m) / number of layers 2-3 1352.3-1359.6 4.4 / 2 5-6 1404.2-1411.8 4.0 / 2 total 8.4 / 4

[0117] Table 12 Oil production before using chemicals

[0118] Oil well number Production time Stratum Nissan oil t Nissan water t Water content Cumulative oil production Q20-8 201707 2-6 1.1 5.5 82 1322

[0119] Construction method:

[0120] The nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs of the present invention was selected for the oil well and injected through the oil pipe. A total of 4 tons of the agent was injected. The well was sealed for 15 days after the construction. See Table 13 for details:

[0121] Table 13Q20-8 Well Construction Status

[0122]

[0123] Comparison of oil well effects before and after using the agent:

[0124] The Q20-8 oil well was constructed in November 2023, using nano-dispersed reservoir enhancer for low permeability water-sensitive reservoirs. The results after construction are as follows: Figure 9 , as shown in Table 14:

[0125] Table 14Q20-8 Oil Well Results

[0126]

[0127] It can be concluded from Table 14 that before construction, the well produced 1.1 tons of oil and 5.5 tons of water per day, with a water content of 82%; after construction, the well produced a stable daily oil output of 10 tons, with a daily increase of 8.9 tons, and is currently continuing to be effective. Figure 9 The graph shows the construction effect before and after the nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs prepared in Example 2 was added to the Q20-8 well in Jing'an Oilfield.

[0128] The effectiveness of the oil wells after construction reflects the effect of using nano-dispersed reserve enhancers in low permeability water-sensitive reservoirs in increasing oil well production.

[0129] It can be seen that the nano-dispersed reserve enhancer in low permeability water-sensitive reservoirs has a significant effect, increasing crude oil fluidity, improving formation permeability, and increasing oil field production, with a cumulative increase of 482 tons of oil, and significant economic benefits.

[0130] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention may be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the foregoing description. It is intended that all variations that fall within the meaning and range of equivalents of the claims be embraced within the present invention. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0131] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent replacements, and improvements made to the above embodiments based on the technical essence of the present invention shall be included in the scope of protection of the technical solution of the present invention.

Claims

1. A nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs, characterized in that: The composition comprises the following components by mass percentage: 30%-35% enzyme, 9%-12% polysorbate, 0.1%-0.5% modified nano ZnO, 0.6-1.2% Span, 0.2%-0.4% modified nano SiO2, 0.5%-1% sodium hydroxide, 1.5%-5% anhydrous ethanol, and the balance is water; The enzyme is at least one of polyphenol oxidase, catalase, and lipase; The polysorbate is at least one of polysorbate 21-81; The Span is at least one of Span 60-85; The modified nano-SiO2 particles are an amorphous white powder nano-material modified with SiO2 as the main component, and the particle size is 5-20nm; The modified nano ZnO particles are white hexagonal or spherical particles with ZnO as the main component and an average particle size of 50 nm. The model of the modified nano ZnO is DXN-GY120; The model of the modified nano-SiO2 is TSP-L12; The preparation method of the storage agent comprises the following steps: Step (1) adding the formulated amount of enzyme and polysorbate to a large stirred reactor at room temperature, stirring uniformly at 120 rpm and 10-30°C for 1-2 hours; Step (2) Place modified nano-ZnO, modified nano-SiO2, sodium hydroxide, Span, and anhydrous ethanol in a small stirred reactor according to the formula amount, and stir and react at a constant temperature of 80°C and a speed of 2000 rpm for 10 minutes; Step (3) The reactants in the small stirred reactor are quickly poured into the large stirred reactor, and the mixture is stirred uniformly at a speed of 120 rpm and a constant temperature of 30°C for another 2 hours. Water is added according to the formula amount and stirring is continued for 30 minutes. After that, heating is stopped and the mixture is cooled to room temperature to obtain a nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs. The reaction time in step (1) of the preparation method is 1 h; The method for using the reserve-increasing agent comprises: injecting the low permeability water-sensitive reservoir nano-dispersed reserve-increasing agent and the nano-pressure-reducing reserve-increasing agent together, wherein the nano-pressure-reducing reserve-increasing agent comprises any one or more of enzyme, modified nano-SiO2 particles, polyethoxylated fatty alcohol, surface modifier S1-69 and water; The nano-dispersed reserve-increasing agent for low-permeability water-sensitive oil reservoirs and the nano-pressure-reducing reserve-increasing agent are used in combination as follows: the nano-dispersed reserve-increasing agent for low-permeability water-sensitive oil reservoirs is first injected to decompose the crude oil near the wellbore, and then the nano-pressure-reducing reserve-increasing agent is injected to remove blockage and increase injection in depth.

2. The nano-dispersed storage enhancer for low permeability water-sensitive oil reservoirs according to claim 1, characterized in that: The nano-dispersed storage enhancer for low-permeability water-sensitive oil reservoirs is suitable for low-permeability water-sensitive oil reservoirs.

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