CN111778005A - Method for reducing pressure and increasing injection of hydrophobic modified nano silicon dioxide fluid - Google Patents
Method for reducing pressure and increasing injection of hydrophobic modified nano silicon dioxide fluid Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 147
- 239000012530 fluid Substances 0.000 title claims abstract description 86
- 238000002347 injection Methods 0.000 title claims abstract description 75
- 239000007924 injection Substances 0.000 title claims abstract description 75
- 238000000034 method Methods 0.000 title claims abstract description 32
- 230000002209 hydrophobic effect Effects 0.000 title claims abstract description 23
- 239000005543 nano-size silicon particle Substances 0.000 title abstract description 19
- 235000012239 silicon dioxide Nutrition 0.000 title description 21
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 102
- 229910052681 coesite Inorganic materials 0.000 claims abstract description 82
- 229910052906 cristobalite Inorganic materials 0.000 claims abstract description 82
- 229910052682 stishovite Inorganic materials 0.000 claims abstract description 82
- 229910052905 tridymite Inorganic materials 0.000 claims abstract description 82
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000002270 dispersing agent Substances 0.000 claims abstract description 30
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- 230000015572 biosynthetic process Effects 0.000 claims abstract description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical group CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 41
- 238000003756 stirring Methods 0.000 claims description 27
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 24
- 239000000725 suspension Substances 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 22
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical group [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 15
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 claims description 13
- 239000012153 distilled water Substances 0.000 claims description 9
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- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
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- 230000003075 superhydrophobic effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
Abstract
A method for lowering pressure and increasing injection of hydrophobized modified nano-silicon dioxide fluid comprises the following step of mixing 0.1-0.5% of modified nano-SiO20.3 to 1 percent of dispersant, 0.1 to 0.5 percent of dispersing auxiliary agent and the balance of water are evenly mixed to obtain SiO2A nanofluid; mixing nano SiO2Fluid is added to the injection system and pumped into the target formation. After the nano-fluid with the functions of reducing pressure and increasing injection is injected into the stratum, the nano-SiO2The particles can be well adsorbed on the surface of the rock core to form an interface micron-scale morphology constructed by spreading of the nanoparticles, namely a micro-nano dual structure, the wettability of the particles is changed from strong hydrophilicity to hydrophobicity, water injection displacement experiments show that the surface wetting is reversed, the strong hydrophobicity of the nanoparticles and a nano lattice structure generate a remarkable hydrophobic sliding effect, the water flow resistance and the injection pressure are reduced, the water phase permeability is remarkably improved, the average improvement is 40.3%, and the pressure reduction is remarkableAnd (4) injection enhancement.
Description
Technical Field
The invention belongs to the technical field of oil field chemicals, and relates to a method for reducing pressure and increasing injection of a hydrophobic modified nano silicon dioxide fluid, which is suitable for water injection operation of an ultra-low permeability oil reservoir.
Background
At present, the main problems of oil extraction operation of low-permeability and ultra-low-permeability oil fields are that the water injection pressure is higher, the water injection quantity is seriously insufficient, and the development and the extraction operation of the oil fields are seriously restricted. Because the energy of the compact oil stratum is insufficient, water injection development is mainly adopted after the fracturing operation is carried out. Under the condition of soaking formation water for a long time and washing injected water, the rock surface around the water injection well becomes water wet, and a layer of hydration film is arranged on the surface of the rock surface. The existence of the hydration film reduces the effective flowing radius of injected water, increases the water flow resistance and the water injection pressure, makes water injection very difficult and reduces the development efficiency of oil fields. The method is characterized in that the problem of high resistance of a reservoir microchannel is generally solved by two methods, namely, the reservoir is subjected to acidification modification to enlarge the aperture of the reservoir; and secondly, modifying the surface of the micro-channel to realize the reversal of the wettability of the wall surface. Because the micro-channel structure of the reservoir is complex, tortuous and inextensible, the reservoir can be seriously damaged once the reconstruction fails. The super-hydrophobic interface has a self-cleaning characteristic, and is constructed on the wall surface of the reservoir core, so that the strong hydrophobic property of the super-hydrophobic interface effectively reduces the water flow resistance and improves the water injection rate, thereby being concerned by many scholars. In 2000, nanometer SiO was introduced from Russia in China2The injection increasing technology reduces the flow resistance of injected water, and succeeds in field experiments, but fails to disclose the mechanism of pressure reduction and injection increasing in detail. Since 2002, domestic Diqin Feng scientific research groups do a certain work on the hydrophobic surface, and the action principle of the hydrophobic surface is disclosed from the aspect of mechanics. However, a great deal of mature technical development is still needed to move the pressure reduction and injection increase technology from the laboratory to the field practice.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for reducing pressure and increasing injection of a hydrophobization modified nano-silica fluid, which is suitable for the water injection operation of an ultra-low permeability reservoir.
The invention is realized by the following technical scheme:
a method for reducing pressure and increasing injection of a hydrophobic modified nano-silica fluid comprises the following steps:
step 1, according to the mass percentage, the content of the active ingredients is 0.1 to 0.5 percentModified nano SiO20.3 to 1 percent of dispersant, 0.1 to 0.5 percent of dispersing auxiliary agent and the balance of water are evenly mixed to obtain SiO2A nanofluid;
step 2, mixing the nano SiO2And adding the fluid into a water injection system, and pumping the fluid into a target stratum, wherein the injection amount of the nano silicon dioxide fluid is 8-10 times of the volume of the core in the target stratum.
The further improvement of the invention is that in the step 1, the uniform mixing is realized by stirring for 10-12min at the temperature of 6500-7000 r/min.
In a further improvement of the invention, in step 1, the dispersant is sodium dodecyl sulfate.
In a further improvement of the invention, in step 1, the dispersing aid is ethanol or sodium hydroxide.
The invention has the further improvement that in the step 1, the nano SiO is modified2Is prepared by the following steps:
1) drying the nano SiO2Adding into absolute ethyl alcohol, dispersing uniformly to obtain nano SiO2A suspension;
2) to nano SiO2Adding dichlorodimethylsilane into the suspension, dripping distilled water, and refluxing at 125-130 deg.C for 50-60min to obtain modified nanometer SiO2。
The invention further improves that in the step 1), the nano SiO2The particle size is 30-40 nm.
The invention further improves that in the step 1), the nano SiO2Nano SiO in suspension2The mass fraction of (A) is 4.8-5.0%.
The further improvement of the invention is that in the step 2), the addition amount of dichlorodimethylsilane is nano SiO216-18% of the mass.
The further improvement of the invention is that in the step 2), the volume ratio of the distilled water to the absolute ethyl alcohol is (10-15): (120-125).
The further improvement of the invention is that in the step 2), the injection amount of the nano silicon dioxide fluid is 8-10 times of the core volume in the target stratum.
Compared with the prior art, the invention has the beneficial effects that:
in the invention, modified SiO is adopted2The prepared nano fluid is dispersed in water base, and is environment-friendly and good in stability. Modified nano SiO in the invention2Has better dispersion stability and uniform distribution, and has no precipitation after being placed for 30 days at normal temperature. The preparation process of the nanometer fluid for reducing the pressure and increasing the injection is simple, the sources of the required dispersing agent and dispersing auxiliary agent are wide, and the price is low; the preparation is convenient, can be prepared and used on site, and is convenient for large-scale construction.
After the nano-fluid with the functions of reducing pressure and increasing injection is injected into the stratum, the nano-SiO2The particles can be well adsorbed on the surface of the rock core to form an interface micron-scale morphology constructed by spreading of the nanoparticles, namely a micro-nano dual structure, the wettability of the micro-nano dual structure is changed from strong hydrophilicity to hydrophobicity, and the surface contact angle is increased from 59.1 degrees to 105.9 degrees. The water injection displacement experiment shows that the hydrophobic nano SiO is adsorbed2The surface of the reservoir rock core of the particles forms a layer of compact hydrophobic interface with a micro-nano dual structure, the surface wetting is reversed, the strong hydrophobicity of the nano particles and the nano lattice structure generate obvious hydrophobic sliding effect, the water flow resistance and the injection pressure are reduced, the water phase permeability is obviously improved, the average permeability is improved by 40.3%, and the pressure reduction and injection increase effects are obvious.
Furthermore, the particle size of the silicon dioxide is 30-40nm, and the distribution is uniform, so that the prepared SiO2The dispersion stability of the nano fluid is better.
Drawings
Fig. 1 is a schematic view of an action mechanism of a rock core after being treated by depressurization and injection-increasing nano-fluid.
FIG. 2 shows unmodified SiO2Contact angle of the nanoparticles.
FIG. 3 is the hydrophobically modified SiO solid of example 22Contact angle of the nanoparticles.
Fig. 4 is a core SEM image before the hydrophobic nano silica fluid is not adsorbed and a core SEM image after the pressure-reducing and injection-increasing nano fluid treatment of example 2, in which (a) is the core SEM image before the hydrophobic nano silica is not adsorbed, and (b) is the core SEM image after the pressure-reducing and injection-increasing nano fluid treatment of example 2.
Fig. 5 is the contact angle of a water drop on a core slice and the core surface contact angle after the treatment of the depressurization and injection-increasing nano-fluid of example 2. Wherein, (a) is the contact angle of water drops on the core slice, and (b) is the core surface contact angle after being treated by the depressurization and injection-increasing nano-fluid in the example 2.
FIG. 6 shows the nano SiO after hydrophobic modification in example 42SEM scan of spherical particles.
Detailed Description
The invention explores a set of novel nano-fluid water injection pressure reduction and injection increase technology for the water injection operation of the ultra-low permeability reservoir. The present invention will be described in further detail with reference to specific examples.
The principle of the invention is as follows: the invention is based on modified nano SiO2The adsorption behavior of the fluid on the surface of the rock core constructs a hydrophobic surface of a reservoir with a micro-nano dual structure so as to achieve the effects of reducing pressure and drag, thereby solving the dilemma that the pressure of the oil and gas exploitation water injection operation of the ultra-low permeability oil reservoir is high and does not decrease. Tetraethyl orthosilicate (TEOS) is used as a silicon source
The method prepares nano SiO with even distribution and controllable grain size2The particles are prepared by adding dichlorodimethylsilane (DMDCS) in different amounts to nano SiO2And (5) modifying the surface.
The specific process of the hydrophobization modified nano silicon dioxide fluid pressure reduction and injection increase method is as follows:
(1) hydrophobically modified nano SiO2Method for producing fluid
With nano SiO2Is prepared from nano SiO through preparing raw material, alcohol as solvent, dichlorodimethylsilane as modifier, water as modifying assistant2The surface is modified.
Step 1, weighing the nano SiO in the required amount2Stirring and heating to 120 ℃, and drying at constant temperature. After the drying is finished, adding 120-125mL of absolute ethyl alcohol, continuing stirring, uniformly dispersing, and preparing into the product with the mass fraction of 4.8-5.0%Nano SiO 22And (3) suspension. Wherein, the nano SiO2The particle size is 30-40 nm.
Step 2, adding nano SiO2Adding dichlorodimethylsilane into the suspension at one time, slowly dripping 10-15mL of distilled water, heating to 125-2. Wherein the addition amount of dichlorodimethylsilane is nano SiO216-18% of the mass;
(2) the pressure reduction and injection increase method of the hydrophobization modified nano silicon dioxide fluid suitable for the water injection operation of the ultra-low permeability reservoir comprises the following steps:
step 1, preparing SiO2Nano fluid, based on mass percentage, modifying nano SiO20.1 to 0.5 percent of dispersing agent, 0.3 to 1 percent of dispersing auxiliary agent, 0.1 to 0.5 percent of dispersing auxiliary agent and the balance of water, and stirring the mixture by a high-speed stirrer at the speed of 6500 and 7000r/min for 10 to 12min so as to ensure that the nano particles can be fully and uniformly dispersed to obtain the SiO2A nanofluid;
step 2, preparing the prepared nano SiO2And adding the fluid into a water injection system, wherein the injection amount of the nano silicon dioxide fluid is 8-10 times of the volume of the rock core. Pumped into the target formation.
Wherein the dispersant is Sodium Dodecyl Sulfate (SDS). Because the nano silicon dioxide has strong hydrophobicity, the contact angle can reach 141.7 ℃, and preferably, the dispersing agent is sodium dodecyl sulfate with the highest hydrophilic-lipophilic balance value.
The dispersing auxiliary agent is ethanol or sodium hydroxide.
The hydrophobic nano SiO of the invention2After the fluid is pumped into a target oil reservoir, the fluid can be well adsorbed on the surface of the rock core to form an interface micron-scale morphology constructed by spreading of nano particles, namely a micro-nano dual structure, and the wettability of the micro-nano dual structure is changed from hydrophilicity to hydrophobicity.
The following are specific examples.
Comparative example 1
The SiO2The preparation method of the nano fluid comprises the following steps：
Step one, weighing the nano SiO2Stirring and heating to 120 ℃, and drying at constant temperature. After the drying is finished, a certain amount of absolute ethyl alcohol is measured to prepare nano SiO with the mass fraction of 4.8%2And (3) suspension.
Step two, preparing SiO2The nano fluid comprises the following raw materials in percentage by mass: unmodified nano SiO20.1 percent of dispersant, 0.3 percent of dispersing aid, 0.1 percent of dispersing aid, SDS, sodium hydroxide and the balance of water.
And step three, stirring for 12min at 6500r/min by using a high-speed stirrer to ensure that the nano particles can be fully and uniformly dispersed.
Comparative example 2
The SiO2The preparation method of the nanofluid comprises the following steps:
step one, weighing the nano SiO2Stirring and heating to 120 ℃, and drying at constant temperature. After the drying is finished, a certain amount of absolute ethyl alcohol is measured to prepare nano SiO with the mass fraction of 4.9%2And (3) suspension.
Step two, preparing SiO2The nano fluid comprises the following raw materials in percentage by mass: unmodified nano SiO20.3 percent of dispersant, 0.6 percent of dispersant, 0.3 percent of dispersing auxiliary agent, SDS as dispersant, ethanol as dispersing auxiliary agent and water as the rest.
And step three, stirring for 11min at the speed of 6750r/min by using a high-speed stirrer to ensure that the nano particles can be fully and uniformly dispersed.
Comparative example 3
The SiO2The preparation method of the nanofluid comprises the following steps:
step one, weighing the nano SiO2Stirring and heating to 120 ℃, and drying at constant temperature. After the drying is finished, a certain amount of absolute ethyl alcohol is measured to prepare nano SiO with the mass fraction of 4.8%2And (3) suspension.
Step two, preparing SiO2The amount of the nano-fluid,the raw materials comprise the following components in percentage by mass: unmodified nano SiO20.5 percent of dispersant, 0.9 percent of dispersing aid, 0.5 percent of dispersing aid, SDS, ethanol and water in balance.
And step three, stirring for 10min at the speed of 70000r/min by using a high-speed stirrer so as to ensure that the nano particles can be fully and uniformly dispersed.
Example 1
The modified nano SiO2The preparation method of the particles comprises the following steps: using nano SiO with grain diameter of 30-40nm2Adopts a wet process to prepare nano SiO by using ethanol as a solvent, dichlorodimethylsilane as a modifier and water as a modification auxiliary agent as raw materials2The surface is modified.
Step one, weighing the nano SiO2Heating to 120 deg.C with stirring in a three-neck flask, and drying at constant temperature for 50 min. After drying, 120mL of absolute ethyl alcohol is measured, stirring and dispersing are continued for 10min, and nano SiO with the mass fraction of 4.8% is prepared2And (3) suspension.
Step two, to nano SiO2Nano SiO is added into the suspension liquid at one time2And (3) slowly adding 10mL of distilled water dropwise into dichlorodimethylsilane with the mass of 15%, heating to 130 ℃ after the dropwise addition is finished, and refluxing for 50 min.
Step three, after the reaction is finished, centrifugally washing the suspension liquid for 3 times by using absolute ethyl alcohol, and drying to constant weight to obtain the modified nano SiO2And (3) granules.
Example 2
This example uses the modified nano-SiO obtained in example 12The particles are used for preparing the pressure-reducing injection-increasing nanofluid.
Step one, preparing a pressure-reducing injection-increasing nano fluid, and mixing the following raw materials in percentage by mass: modified nano SiO20.1 percent of dispersant, 0.3 percent of dispersing agent, 0.1 percent of dispersing auxiliary agent, SDS as dispersant and the balance of water. Wherein the dispersing assistant is sodium hydroxide.
And step two, adding the raw materials into a high-speed stirrer for stirring, and stirring for 12min at the speed of 6500r/min by adopting the high-speed stirrer so as to ensure that the nano particles can be fully and uniformly dispersed, thereby obtaining the pressure-reducing and injection-increasing nano fluid.
Example 3
This example uses the modified nano-SiO obtained in example 12The particles are used for preparing the pressure-reducing injection-increasing nanofluid.
Step one, preparing a pressure-reducing injection-increasing nano fluid, and mixing the following raw materials in percentage by mass: modified nano SiO20.1 percent, 0.3 percent of dispersant, 0.3 percent of dispersing auxiliary agent, SDS as dispersant, ethanol as dispersing auxiliary agent and water as the rest.
And step two, adding the raw materials into a high-speed stirrer for stirring, and stirring for 11min at the speed of 6750r/min by adopting the high-speed stirrer so as to ensure that the nano particles can be fully and uniformly dispersed, thereby obtaining the nano fluid for reducing the pressure and increasing the injection.
Example 4
This example uses the modified nano-SiO obtained in example 12The particles are used for preparing the pressure-reducing injection-increasing nanofluid.
Step one, preparing a pressure-reducing injection-increasing nano fluid, wherein the nano fluid comprises the following raw materials in percentage by mass: modified nano SiO20.5 percent of dispersing agent, 0.9 percent of dispersing agent, 0.5 percent of dispersing auxiliary agent, SDS (sodium dodecyl sulfate) and ethanol as dispersing auxiliary agent. The balance of water.
And step two, adding the raw materials into a high-speed stirrer for stirring, and stirring at 7000r/min for 10min to ensure that the nanoparticles can be fully and uniformly dispersed, so as to obtain the pressure-reducing injection-increasing nano fluid.
The following are performance tests.
1. Indoor core displacement experiment:
the core displacement experiment step comprises the following steps:
firstly, preparing ultra-low permeability reservoir core samples A, B and C, wherein the ultra-low permeability reservoir core has large porosity span which can be divided into a plurality of numerical sections of 5-10, 10-15 and 15-20, and the experiment selects the numerical sections of 10-15 and 15-20, so that the pressure reduction and injection increase effects of different porosities can be measured conveniently. The core sample a (L5.04 cm × W2.49 cm) had an original porosity of 11.33% and the core sample B (L5.08cm × W2.44cm) had an original porosity of 15.49%, and the core sample C (L5.55cm × W2.48cm) had an original porosity of 17.49%;
injecting dehydrated and degassed experimental simulation oil into the core sample, preparing the experimental simulation oil (a sample is prepared from degassed crude oil in a research area according to the ratio of diesel oil to crude oil of 2:8, and the viscosity of the simulation oil at 25 ℃ is measured to be 12mPa & s), and measuring the injection pressure P1 after the sample is stabilized;
and step three, injecting the prepared silicon dioxide nano fluid into a water injection system under the same injection pressure and the same displacement time, performing modified nano fluid displacement operation on core samples (corresponding relations are shown as the following: comparative example 1, example 2 for core sample A, comparative example 2, example 3 for core sample B, and comparative example 3 and example 4 for core sample C), realizing displacement balance of injected water for simulated oil in the core, and recording the injection pressure P2 after stabilization. By the formula: the pressure reduction rate after the treatment of the pressure reduction injection fluid is calculated according to the pressure reduction rate (P1-P2)/P1 multiplied by 100 percent, and the water phase permeability and the pressure reduction effect are examined. The experimental relevant parameters are shown in table 1.
TABLE 1 parameters relating to comparative examples 1-3, examples 2-4
Note: the calculation method of the water phase permeability comprises the following steps: the water phase permeability of comparative examples 1, 2 and 3 was calculated as W1, and the water phase permeability of examples 2 and 3 was calculated as W2, according to the core displacement experiment control relation, by the formula: and calculating the relative change rate of the water phase permeation after the treatment of the nano fluid with pressure reduction and injection enhancement according to the relative change rate of the water phase permeation (W2-W1)/W1 multiplied by 100 percent.
2. Evaluation of displacement, pressure reduction and injection enhancement effects of silicon dioxide nanofluid on rock core sample before and after modification
Water injection displacement experiments show that when the nano particles are completely contacted with water, the strong hydrophobicity and the nano lattice structure of the nano particles generate a remarkable hydrophobic sliding effect (as shown in figure 1), and the nano hydrophobic layer is arranged in a modeFor the dot matrix arrangement, the injected water can let rivers shrink to central pore through the nanometer dot matrix, lets rivers can't adsorb on hydrophilic rock surface, and the nanoparticle is arranged the chance that the interval is little can reduce rivers contact hydrophilic rock on rock surface simultaneously to greatly reduced the injection resistance, improved the aqueous phase permeability. After the treatment of the pressure-reducing nano injection-increasing liquid in the embodiments 2-4, the relative permeability of the water phase of the rock core sample is obviously improved by 40.3 percent on average, the water injection pressure is generally reduced, and the pressure-reducing rate of the rock core is 20-30 percent. Indicating that the modified silica fluid acts to reduce the resistance to water flow and injection pressure. After the treatment of the pressure reduction and the injection increase of the nanofluid in example 2, a scanning electron micrograph of the rock core which does not adsorb the hydrophobic nano-silica nanofluid is shown in fig. 4, and (a) in fig. 4 is an SEM image of the rock core which does not adsorb the hydrophobic nano-silica nanofluid; fig. 4 (b) is a core SEM image after adsorbing the hydrophobic nano-silica fluid; as can be seen from (a) and (b) in FIG. 4, the hydrophobic nano SiO2After the fluid is pumped into a target oil reservoir, the fluid can be well adsorbed on the surface of the rock core to form an interface micron-scale morphology constructed by spreading of nano particles, namely a micro-nano dual structure.
2 evaluation of rock surface wetting reversal Capacity
After the hydrophobic nano modified fluid prepared in example 2 is subjected to contact angle test, the modified nano SiO prepared by the invention2The particle scanning electron microscope is shown in fig. 6, the particle size distribution is 30-40nm, after the chemical modification is successful, the contact angle is increased from 19.5 degrees to 141.7 degrees, and the contact angle is shown in fig. 2 and fig. 3 and shows strong hydrophobic property; hydrophobic nano SiO2After the fluid is pumped into a target oil reservoir, the fluid can be well adsorbed on the surface of the rock core to form an interface micron-scale morphology constructed by spreading of nano particles, namely a micro-nano dual structure, and the wettability of the micro-nano dual structure is changed from hydrophilicity to hydrophobicity, so that the wettability is known to be reversed. After the core treated by the depressurization and injection-increasing nanofluid of example 2 is subjected to a contact angle test, the surface contact angle is increased from 59.1 degrees to 105.9 degrees, as shown in (a) and (b) of fig. 5. The pressure-reducing injection-increasing agent prepared by the invention has better wetting reversal capability, can increase the water absorption capability of the stratum and reduce the flow resistance of water, therebyThereby effectively reducing the pressure of water injection and realizing the purposes of pressure reduction and injection increase.
Example 5
The specific process of the hydrophobization modified nano silicon dioxide fluid pressure reduction and injection increase method is as follows:
(1) hydrophobically modified nano SiO2The preparation method comprises the following steps:
step one, weighing the nano SiO2Heating to 120 deg.C with stirring in a three-neck flask, and drying at constant temperature for 50 min. After drying, 120mL of absolute ethyl alcohol is measured, stirring and dispersing are continued for 10min, and nano SiO with the mass fraction of 4.8% is prepared2And (3) suspension.
Step two, to nano SiO2Nano SiO is added into the suspension liquid at one time2And (3) slowly adding 10mL of distilled water dropwise into 18% of dichlorodimethylsilane by mass, heating to 125 ℃ after the dropwise addition is finished, and refluxing for 60 min.
Step three, after the reaction is finished, centrifugally washing the suspension liquid for 3 times by using absolute ethyl alcohol, and drying to constant weight to obtain the modified nano SiO2And (3) granules.
(2) The pressure reduction and injection increase method of the hydrophobization modified nano silicon dioxide fluid suitable for the water injection operation of the ultra-low permeability reservoir comprises the following steps:
step one, preparing a pressure-reducing injection-increasing nano fluid, and mixing the following raw materials in percentage by mass: modified nano SiO20.1 percent of dispersant, 1 percent of dispersant, 0.2 percent of dispersing auxiliary agent, SDS as dispersant and the balance of water. Wherein the dispersing assistant is sodium hydroxide.
Step two, stirring for 12min at 6500r/min by adopting a high-speed stirrer to ensure that the nano particles can be fully and uniformly dispersed to obtain the nano SiO2A fluid. Mixing nano SiO2And adding the fluid into a water injection system, and pumping the fluid into a target stratum, wherein the injection amount of the nano silicon dioxide fluid is 10 times of the volume of the core in the target stratum.
Example 6
The specific process of the hydrophobization modified nano silicon dioxide fluid pressure reduction and injection increase method is as follows:
(1) hydrophobically modified nano SiO2Preparation method of (1)
Step one, weighing the nano SiO2Heating to 120 deg.C with stirring in a three-neck flask, and drying at constant temperature for 50 min. After drying, 120mL of absolute ethyl alcohol is measured, stirring and dispersing are continued for 10min, and nano SiO with the mass fraction of 4.9% is prepared2And (3) suspension.
Step two, to nano SiO2Nano SiO is added into the suspension liquid at one time2And slowly adding 15mL of distilled water dropwise into dichlorodimethylsilane with the mass of 16%, heating to 130 ℃ after the dropwise addition is finished, and refluxing for 50 min.
Step three, after the reaction is finished, centrifugally washing the suspension liquid for 3 times by using absolute ethyl alcohol, and drying to constant weight to obtain the modified nano SiO2And (3) granules.
(2) The pressure reduction and injection increase method of the hydrophobization modified nano silicon dioxide fluid suitable for the water injection operation of the ultra-low permeability reservoir comprises the following steps:
step one, preparing a pressure-reducing injection-increasing nano fluid, and mixing the following raw materials in percentage by mass: modified nano SiO20.2 percent of dispersant, 0.5 percent of dispersing agent, 0.3 percent of dispersing auxiliary agent, SDS as dispersant and the balance of water. Wherein the dispersing assistant is sodium hydroxide.
Step two, stirring for 12min at 6500r/min by adopting a high-speed stirrer to ensure that the nano particles can be fully and uniformly dispersed to obtain the nano SiO2A fluid. Mixing nano SiO2And adding the fluid into a water injection system, and pumping the fluid into a target stratum, wherein the injection amount of the nano silicon dioxide fluid is 8 times of the volume of the rock core in the target stratum.
Example 7
The specific process of the hydrophobization modified nano silicon dioxide fluid pressure reduction and injection increase method is as follows:
(1) hydrophobically modified nano SiO2Preparation method of (1)
Step one, weighing the nano SiO2Heating to 120 deg.C with stirring in a three-neck flask, and drying at constant temperature for 50 min. After the drying is finished, 120mL of the powder is measuredStirring and dispersing for 10min with anhydrous ethanol to obtain 5% nanometer SiO2And (3) suspension.
Step two, to nano SiO2Nano SiO is added into the suspension liquid at one time2And (3) adding 17% by mass of dichlorodimethylsilane, slowly dropwise adding 12mL of distilled water, after dropwise adding, heating to 127 ℃, and refluxing for 50 min.
Step three, after the reaction is finished, centrifugally washing the suspension liquid for 3 times by using absolute ethyl alcohol, and drying to constant weight to obtain the modified nano SiO2And (3) granules.
(2) The pressure reduction and injection increase method of the hydrophobization modified nano silicon dioxide fluid suitable for the water injection operation of the ultra-low permeability reservoir comprises the following steps:
step one, preparing a pressure-reducing injection-increasing nano fluid, and mixing the following raw materials in percentage by mass: modified nano SiO20.3 percent of dispersant, 0.7 percent of dispersing agent, 0.5 percent of dispersing auxiliary agent, SDS as dispersant and the balance of water. Wherein the dispersing assistant is sodium hydroxide.
Step two, stirring for 12min at 6500r/min by adopting a high-speed stirrer to ensure that the nano particles can be fully and uniformly dispersed to obtain the nano SiO2A fluid. Mixing nano SiO2And adding the fluid into a water injection system, and pumping the fluid into a target stratum, wherein the injection amount of the nano silicon dioxide fluid is 9 times of the volume of the core in the target stratum.
Claims (10)
1. A method for reducing pressure and increasing injection of a hydrophobic modified nano-silica fluid is characterized by comprising the following steps:
step 1, according to the mass percentage, 0.1 to 0.5 percent of modified nano SiO20.3 to 1 percent of dispersant, 0.1 to 0.5 percent of dispersing auxiliary agent and the balance of water are evenly mixed to obtain SiO2A nanofluid;
step 2, mixing the nano SiO2Fluid is added to the injection system and pumped into the target formation.
2. The method as claimed in claim 1, wherein the step 1 of uniformly mixing is performed by stirring at 6500-7000r/min for 10-12 min.
3. The method for depressurizing and injecting a hydrophobized modified nano-silica fluid according to claim 1, wherein in the step 1, the dispersant is sodium dodecyl sulfate.
4. The method for depressurizing and injecting a hydrophobized modified nano-silica fluid according to claim 1, wherein in the step 1, the dispersing auxiliary agent is ethanol or sodium hydroxide.
5. The method for depressurizing and injecting the hydrophobized modified nano-silica fluid according to claim 1, wherein in the step 1, the modified nano-SiO2Is prepared by the following steps:
1) drying the nano SiO2Adding into absolute ethyl alcohol, dispersing uniformly to obtain nano SiO2A suspension;
2) to nano SiO2Adding dichlorodimethylsilane into the suspension, dripping distilled water, and refluxing at 125-130 deg.C for 50-60min to obtain modified nanometer SiO2。
6. The method for depressurizing and injecting the hydrophobized modified nano-silica fluid according to claim 5, wherein in the step 1), the nano-SiO2The particle size is 30-40 nm.
7. The method for depressurizing and injecting the hydrophobized modified nano-silica fluid according to claim 5, wherein in the step 1), the nano-SiO2Nano SiO in suspension2The mass fraction of (A) is 4.8-5.0%.
8. The method for depressurizing and injecting the hydrophobized modified nano-silica fluid according to claim 5, wherein in the step 2), the addition amount of the dichlorodimethylsilane is nano SiO216-18% of the mass.
9. The method for depressurizing and injecting the hydrophobized modified nano-silica fluid according to claim 5, wherein in the step 2), the volume ratio of the distilled water to the absolute ethyl alcohol is (10-15): (120-125).
10. The method for reducing pressure and increasing injection of the hydrophobized modified nano-silica fluid according to claim 1, wherein in the step 2), the injection amount of the nano-silica fluid is 8-10 times of the core volume of the target formation.
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| CN113426367A (en) * | 2021-06-23 | 2021-09-24 | 西安石油大学 | Method for realizing stabilization of aqueous-phase foam through surface modification of nano silicon dioxide |
| CN114687714A (en) * | 2022-04-12 | 2022-07-01 | 中国矿业大学 | Nano-particle composite low-salinity water-enhanced CO2Method of injection capability |
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