CN112627788A - Method for simulating petroleum recovery by using cellulose nanofiber polymer - Google Patents
Method for simulating petroleum recovery by using cellulose nanofiber polymer Download PDFInfo
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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
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- C—CHEMISTRY; METALLURGY
- 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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- C—CHEMISTRY; METALLURGY
- 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
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/84—Compositions based on water or polar solvents
- C09K8/86—Compositions based on water or polar solvents containing organic compounds
- C09K8/88—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
- C09K8/90—Compositions based on water or polar solvents containing organic compounds macromolecular compounds of natural origin, e.g. polysaccharides, cellulose
- C09K8/905—Biopolymers
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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
- E21B47/00—Survey of boreholes or wells
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- C—CHEMISTRY; METALLURGY
- 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
- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/08—Fiber-containing well treatment fluids
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- C—CHEMISTRY; METALLURGY
- 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
- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/10—Nanoparticle-containing well treatment fluids
Abstract
The invention discloses a method for simulating petroleum recovery by using a cellulose nanofiber polymer, which comprises the following steps: treating the crude oil; preparing a cellulose nanofiber polymer-sodium chloride mixed colloidal solution, and screening out a proper concentration beneficial to petroleum recovery; establishing a model main body for simulating the distribution of petroleum in the sandstone core according to geological parameters stored in the crude oil, slowly injecting the filtered crude oil into the pretreated sandstone core, and counting the injection amount of the crude oil in real time; injecting the secondarily screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution into the model main body according to a twice-displacement mode, and calculating the ratio of the injection amount of the produced liquid to the injection amount of the crude oil to compare the recovery ratio of the twice-displacement mode; the method is based on the amount of the oil injected into the sandstone, and the influence of the displacement experiment of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution on oil recovery and the data change of the oil recovery rate are calculated.
Description
Technical Field
The invention relates to the technical field of petroleum recovery simulation experiment methods, in particular to a method for simulating petroleum recovery by using a cellulose nanofiber polymer.
Background
The polymer flooding method is a method for increasing the viscosity of water by using a water-soluble high molecular polymer and using the water-soluble high molecular polymer as an oil field development injection agent to improve the oil recovery rate. The basic principle of polymer flooding for improving oil recovery is that the fluidity of an oil displacement agent is reduced by increasing the viscosity of injected water, so that fingering and channeling are reduced, and the sweep efficiency is increased to improve the oil recovery.
Currently, the most commonly used polymers for polymer flooding methods are partially Hydrolyzed Polyacrylamide (HPAM) and xanthan gum, both of which reduce its flowability by increasing the viscosity of the water. However, both of these materials have substantial performance limitations in enhanced oil recovery: xanthan gum is easily degraded by bacteria, fragments easily cause pore blockage, and thermal stability is poor; HPAM is susceptible to a variety of chemical, thermal, and mechanical degradation effects, and thus its viscosifying effect gradually decreases as it passes through the pore media. Because many polymers used in current polymer flooding are toxic and environmentally hazardous, polymer flooding requires a stable, environmentally friendly polymer for enhanced oil recovery.
In an experiment for simulating the influence of the polymer on the oil recovery rate, the polymer is generally injected into sandstone containing oil and the produced fluid of a core is collected to measure the produced oil quantity, but the internal crude oil quantity of the sandstone containing oil cannot be calculated, so that the material rate of simulated oil recovery of different polymers cannot be calculated, and finally, the oil recovery rate cannot be transversely compared with different polymers, and the oil recovery rate cannot be longitudinally compared with the same polymer at different time intervals.
Disclosure of Invention
The invention aims to provide a method for simulating oil recovery by using a cellulose nanofiber polymer, which aims to solve the technical problems that in the prior art, different polymers cannot be used for carrying out transverse comparison on oil recovery ratio, and the same polymer cannot be used for carrying out longitudinal comparison on the oil recovery ratio in different time periods.
In order to solve the technical problems, the invention specifically provides the following technical scheme:
a method for simulating oil recovery using a cellulose nanofiber polymer comprising the steps of:
step 100, processing crude oil, and filtering the crude oil by using a vacuum filter and filter paper;
200, preparing a cellulose nanofiber polymer-sodium chloride mixed colloidal solution, screening the stability of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution by a stability measurement mode, and screening the concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution beneficial to harvesting from the solution screened at the first time by an interfacial tension measurement mode and a contact angle measurement mode;
step 300, establishing a model main body for simulating the distribution of petroleum in the sandstone core according to geological parameters stored in crude oil, slowly injecting the crude oil filtered in the step 100 into the pretreated sandstone core to simulate the storage environment of the crude oil in the sandstone core, and counting the injection amount of the crude oil in real time;
step 400, injecting the secondarily screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution into the model main body according to a twice-displacement mode, comparing output liquids of the twice-displacement mode, and calculating the recovery ratio of the twice-displacement mode by calculating the ratio of the output liquids to the injection amount of crude oil.
As a preferred embodiment of the present invention, in step 300, the implementation method for establishing a model body for simulating crude oil distribution and formation storage according to the geological parameters of crude oil storage is as follows:
performing pretreatment operation on the Berea sandstone core, wherein the pretreatment operation comprises cleaning and drying the Berea sandstone core and saturated soaking by using saline water;
and injecting crude oil into the pretreated Berea sandstone core, and saturating the Berea sandstone core by the crude oil at a low flow rate of 1mL/min and a high flow rate of 10mL/min in the injection process.
As a preferred scheme of the invention, the concrete implementation steps of the pretreatment operation on the Berea sandstone core are as follows:
washing the Berea sandstone core by using a 3% NaCl solution and methanol, drying, and measuring the dry weight, porosity and air permeability of the dried Berea sandstone core;
soaking the Berea sandstone core by using a vacuum and saturated 0.1 wt% NaCl solution, and weighing the saturated wet weight of the Berea sandstone core;
and (3) injecting the filtered crude oil obtained in the step (100) into the Berea sandstone core, displacing NaCl solution in the Berea sandstone core to leach until the inlet flow and the outlet flow of the crude oil are consistent, and calculating the saturation of the irreducible water of the Berea sandstone core at the moment.
As a preferable embodiment of the present invention, when the filtered crude oil obtained in step 100 is injected into the Berea sandstone core, the crude oil is injected into the sandstone core at a low flow rate of 1mL/min, and after stabilization, the crude oil is injected into the sandstone core at a high flow rate of 10 mL/min.
As a preferable scheme of the present invention, after the filtered crude oil obtained in step 100 is injected into the Berea sandstone core and the irreducible water saturation of the Berea sandstone core at that time is calculated, the Berea sandstone core is soaked in the crude oil obtained in step 100 and is kept still, so that the pores of the Berea sandstone core are fully saturated with the crude oil.
As a preferred embodiment of the present invention, in step 200, the preparation of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution is implemented by the following steps:
obtaining an original concentrated solution of cellulose nanofiber polymer colloid;
mixing and diluting deionized water and the original cellulose nanofiber polymer to form cellulose nanofiber polymer colloid solutions with different concentrations;
mixing sodium chloride solutions with different concentrations with the original cellulose nano-fiber polymer colloidal solution to dilute the cellulose nano-fiber polymer colloidal solution into different concentrations and generate different classes of the cellulose nano-fiber polymer-sodium chloride mixed colloidal solution;
uniformly stirring the cellulose nanofiber polymer-sodium chloride mixed colloidal solution of the same category, dividing the mixed colloidal solution into two groups, respectively storing the two groups of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution in constant temperature boxes at 20 ℃ and 60 ℃, and judging the stability of all the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions by regularly measuring the particle size and zeta potential.
As a preferred embodiment of the present invention, in step 200, a specific implementation method for screening the stable concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution by using a stability measurement manner includes:
sampling the cellulose nanofiber polymer-sodium chloride mixed colloidal solution stored in a constant temperature box at 20 ℃ and 60 ℃ at regular time to carry out a stability measurement experiment;
and comparing the measurement results of each stability measurement experiment, and screening out the cellulose nano-fiber polymer-sodium chloride colloidal solution which is still stable after being prepared for one month.
As a preferred embodiment of the present invention, in step 200, the cellulose nanofiber polymer-sodium chloride mixed colloidal solution with a stable concentration range is screened out by detecting an interfacial tension measurement mode and a contact angle measurement mode to obtain a concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution that is beneficial for improving the recovery ratio, and the specific implementation method is as follows:
performing an interfacial tension measurement experiment on crude oil and the cellulose nano-fiber polymer-sodium chloride colloidal solution screened to maintain stability, and a measurement experiment on a contact angle between the cellulose nano-fiber polymer-sodium chloride colloidal solution and the sandstone surface, further screening out the cellulose nano-fiber polymer-sodium chloride colloidal solution with a proper concentration range from the stable cellulose nano-fiber polymer-sodium chloride colloidal solution to screen out the concentration of the cellulose nano-fiber polymer-sodium chloride colloidal system affecting the permeability in sandstone,
specifically, the contact angle between the cellulose nanofiber polymer-sodium chloride mixed colloidal solution and the sandstone surface is calculated by using a contact angle measurement mode, namely, pre-soaking the polished sandstone in the crude oil environment in the step 100 for saturation and aging, and calculating the contact angle of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution drop on the polished sandstone surface.
As a preferred scheme of the present invention, in step 400, the cellulose nanofiber polymer-sodium chloride mixed colloidal solution is injected into the model main body, oil exploitation is simulated through two displacement modes, and a specific implementation method for calculating the oil exploitation rate of each displacement mode includes:
step 401, performing a primary oil recovery displacement experiment on a 0.1 wt% sodium chloride solution by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a first output liquid by using a test tube with scales;
step 402, stopping injecting the sodium chloride solution when no obvious oil drop is visible in the produced liquid and the pressure difference is stable, performing a secondary oil recovery displacement experiment on the screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution with the appropriate concentration range by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a second produced liquid again;
and step 403, stopping injecting the cellulose nanofiber polymer-sodium chloride mixed colloidal solution when no obvious oil drop is visible in the second output liquid and the pressure difference is stable.
And 404, respectively calculating the recovery ratio of the primary oil recovery displacement experiment and the recovery ratio of the secondary oil recovery displacement experiment, and calculating the recovery ratio enhancement range of the secondary oil recovery displacement experiment by using the cellulose nanofiber polymer-sodium chloride mixed colloidal solution.
As a preferable embodiment of the present invention, in step 403, after stopping the injection of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution, a 0.1 wt% sodium chloride solution is injected to flush out the retained cellulose nanofiber polymer in the Berea sandstone core.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, through the cleaning and drying operations of the sandstone without petroleum, a proper amount of petroleum is injected until the sandstone is saturated according to the porosity and the air permeability of the sandstone, so that the amount of the petroleum injected into the sandstone can be calculated in real time, and the influence of a displacement experiment of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution on petroleum recovery and the data change of the petroleum recovery ratio are calculated on the basis of the amount of the petroleum injected into the sandstone.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
FIG. 1 is a schematic flow chart of a simulation experiment method according to an embodiment of the present invention;
fig. 2 is a solution sample ratio, namely a labeled diagram, of a cellulose nanofiber polymer-sodium chloride mixed colloidal solution according to an embodiment of the present invention;
FIG. 3 is a graph showing the measurement results of the particle size of particles provided in the examples of the present invention;
FIG. 4 is a graph showing the results of measurement of zeta potential provided by an embodiment of the present invention;
FIG. 5 is a graph of interfacial tension and crude oil to sandstone contact angle measurements provided by an example of the present invention;
FIG. 6 is a representation of core data for simulated oil production provided by an embodiment of the present invention;
FIG. 7 is a schematic diagram of the amount of oil produced in simulating oil production according to an embodiment of the present invention;
fig. 8 is a schematic operation flow diagram of an experimental method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the present invention provides a method for simulating oil recovery using cellulose nanofiber polymer,
according to the injectability of the cellulose nanofiber polymer-sodium chloride solution colloid system in sandstone, the concentration range of colloid components is screened, and the risk of pore throat blockage caused by instability of the colloid system due to overhigh concentration is reduced; compared with cellulose nanocrystals, due to the fact that Tempo-CNF particles are large, the flow velocity of water molecules is larger than that of nanofiber particles due to the fact that the particles and the water molecules are remarkably poor in mass, large particles are gradually accumulated at the throat, and recovery efficiency is improved by improving oil washing efficiency and increasing sweep efficiency.
The method specifically comprises the following steps:
step 100, processing crude oil, and filtering the crude oil by using a vacuum filter and filter paper;
200, preparing a cellulose nanofiber polymer-sodium chloride mixed colloidal solution, primarily screening the stability of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution by using a stability measurement mode, and secondarily screening the concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution which is beneficial to recovery from the primarily screened solution by using an interfacial tension measurement mode and a contact angle measurement mode.
In the step, the preparation of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution is realized by the following steps:
(1) obtaining the original concentrated solution of cellulose nanofiber polymer colloid.
(2) Mixing and diluting deionized water and the original cellulose nanofiber polymer to form cellulose nanofiber polymer colloid solutions with different concentrations.
(3) Mixing sodium chloride solutions with different concentrations with the original cellulose nano-fiber polymer colloid solution to dilute the cellulose nano-fiber polymer colloid solution into different concentrations, and generating different types of cellulose nano-fiber polymer-sodium chloride mixed colloid solutions.
Specifically, in the step (2), the original concentrated colloidal solution of the cellulose nanofiber polymer is diluted into a colloidal solution of the cellulose nanofiber polymer with the concentration of 0.05 wt% and 0.1 wt% by using deionized water.
In the step (3), 0.1 wt% and 0.5 wt% sodium chloride (NaCl for short) solutions are mixed with the original concentrated colloidal solution of cellulose nanofiber polymer (Tempo-CNF for short), respectively, and the original concentrated colloidal solution of cellulose nanofiber polymer is diluted into 0.05 wt% and 0.1 wt% colloidal solutions of cellulose nanofiber polymer, respectively.
(4) The method comprises the steps of uniformly stirring cellulose nanofiber polymer-sodium chloride mixed colloidal solutions of the same category, dividing the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions into two groups, respectively storing the two groups of the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions in constant temperature boxes at 20 ℃ and 60 ℃, judging the stability of all the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions by regularly measuring particle size and zeta potential, and obtaining 12 colloidal solutions by using the specifically prepared solution sample ratios, namely the reference numerals, of the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions as shown in figure 2.
It should be added that when sodium chloride solutions with different solubilities are mixed with the diluted cellulose nanofiber polymer colloidal solution, a dispersion machine is used to stir the colloidal solution to make the particles distributed more uniformly so as to avoid aggregating together to form agglomeration and sedimentation.
The 12 colloidal solutions are respectively measured for particle size and zeta potential according to planned time points, and the specific implementation method for screening the stable concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution by a stability measurement mode at one time comprises the following steps:
firstly, sampling cellulose nano-fiber polymer-sodium chloride mixed colloid solution stored in a constant temperature box at 20 ℃ and 60 ℃ at regular time to carry out stability measurement experiment. Wherein, the time selection points for timing sampling measurement are the day, 24 hours, one week and one month of solution preparation.
And (II) comparing the measurement results of each stability measurement experiment, and screening out the cellulose nano-fiber polymer-sodium chloride colloidal solution which is still stable after being prepared for one month.
It should be added that the parameters for measuring the stability of the prepared cellulose nanofiber polymer-sodium chloride mixed colloidal solution are as follows: the particle size of the colloidal solution measured at the above sampling time point and the zeta potential of the colloidal solution measured at the sampling time point are shown in fig. 3 and 4.
In addition, a nanometer-scale Malvern Zetasizer Nano ZS potential analyzer was used in particle measurement experiments to sample the cellulose nanofiber polymer-sodium chloride mixed colloidal solution for the measurement of nanoparticle size and Zeta potential.
According to the experimental result, the particle size of the colloidal solution at high temperature is generally larger than that at room temperature; the unstable solution with the particle size exceeding 1000 nanometers corresponds to the unstable solution with the zeta potential absolute value lower than 30mV in number and is a colloidal solution at high temperature.
When the concentration of the sodium chloride solution dispersant is 0.5 wt%, the Tempo-CNF colloidal solution at all concentrations is unstable at high temperature; the colloidal solution with 0.1 wt% of Tempo-CNF concentration can generate flocculation precipitation at high temperature, and can not keep stable state for a long time.
Combining the results of fig. 3 and 4, 0.1 wt% of a colloid solution of Tempo-CNF formulated with 0.1 wt% sodium chloride solution was selected as the displacement fluid for the enhanced oil recovery displacement experiments.
In addition, the stability of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution is tested to select the cellulose nanofiber polymer-sodium chloride mixed colloidal solution with a proper concentration range so as to improve the injectability, and the concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution which is beneficial to recovery is secondarily screened from the primarily screened solution in an interfacial tension measurement mode and a contact angle measurement mode.
The concentration of the cellulose nano-fiber polymer-sodium chloride mixed colloidal solution which is beneficial to improving the recovery ratio is secondarily screened out by detecting an interfacial tension measuring mode and a contact angle measuring mode from the cellulose nano-fiber polymer-sodium chloride mixed colloidal solution with a stable concentration range, and the specific realization method is as follows:
and (3) performing an interfacial tension measurement experiment on the crude oil and the screened cellulose nanofiber polymer-sodium chloride colloidal solution with the maintained stability, performing a measurement experiment on a contact angle between the cellulose nanofiber polymer-sodium chloride colloidal solution and the sandstone surface, and further screening out a cellulose nanofiber polymer-sodium chloride colloidal solution with a proper concentration range from the stable cellulose nanofiber polymer-sodium chloride colloidal solution so as to screen out the concentration of the cellulose nanofiber polymer-sodium chloride colloidal system influencing the permeability in the sandstone.
Specifically, the contact angle of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution and the sandstone surface is calculated by using a contact angle measurement mode, namely, pre-soaking the polished sandstone in the crude oil environment of the step 100 for saturation and aging, and calculating the contact angle of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution drop on the polished sandstone surface.
Specifically, the interfacial tension measurement mode and the contact angle measurement mode are used for analyzing the cellulose nanofiber polymer-sodium chloride mixed colloid solution from the aspect of permeability influence factors (interfacial tension and contact angle) so as to reduce the interfacial tension and increase the contact angle of crude oil and sandstone, so that the fact that the recovery ratio can be improved by adding TEMPO-CNF is inferred.
In this step, the crude oil from the North sea was filtered through a vacuum filter and 5 μm filter paper, and then the interfacial tension between the 24 colloidal solutions and the crude oil as shown in FIG. 2 was measured, and the contact angle of each colloidal solution drop in the crude oil with the polished quartz surface was measured.
12 interfacial tension of the colloidal solution and crude oil, and contact angle of crude oil droplets with a polished quartz surface in a colloidal solution environment are shown in fig. 5.
From the interfacial tension data, the interfacial tension of the crude oil and the Tempo-CNF colloidal solution is slightly lower at 60'C than at 20' C; as can be seen from the contact angle data, the contact angle of the colloidal solution with sandstone is less at 60' C than at 20' C, i.e., the contact angle of the crude oil with sandstone surface is greater at 20' C. The larger the contact angle is, the lower the wettability of the crude oil to quartz is, the higher the wettability of the colloidal solution to quartz is, the crude oil is easier to be separated from the rock surface and is easier to be extracted, and because the temperature of the oil reservoir environment is generally higher than room temperature, for the displacement experiment performed later, the effect under the oil reservoir condition is deduced from the experiment result to be better than the result obtained by the displacement simulation experiment at room temperature.
Step 300, establishing a model main body for simulating the distribution of petroleum in the sandstone core according to the geological parameters stored in the crude oil, slowly injecting the crude oil filtered in the step 100 into the pretreated sandstone core to simulate the storage environment of the crude oil in the sandstone core, and counting the injection amount of the crude oil in real time, wherein a specific experimental flow chart is shown in fig. 8.
The model body specifically includes: the operation chamber that keeps high temperature high pressure environment, the board is put to the multilayer of setting in the operation chamber, put the central point that the board put at every layer and put and be equipped with the parcel recess, it is equipped with the voltage-sharing injection tube to vertically pass all parcel recesses, and the voltage-sharing injection tube includes sodium chloride solution injection tube and crude oil injection tube respectively, sodium chloride solution injection tube and crude oil injection tube all are equipped with the export respectively in the position of every parcel recess, in order to pour into sodium chloride solution and crude oil respectively in the sandstone rock core, consequently can disposable realization to the experiment of a plurality of sandstone rock cores.
It should be further added that, in the present embodiment, the cellulose nanofiber polymer-sodium chloride mixed colloidal solution may not only be used for simulating oil exploitation, but also for simulating hydrate exploitation, as for the stability screening and permeability screening of the cellulose nanofiber polymer-sodium chloride colloidal solution are not changed, the creation mode of the model body is changed to establish a storage environment (low temperature and high pressure) for simulating natural gas hydrate in the formation, and the development amount of the cellulose nanofiber polymer-sodium chloride colloidal solution for natural gas hydrate and the specific exploitation rate increase range for natural gas hydrate may be calculated by injecting the cellulose nanofiber polymer-sodium chloride colloidal solution and collecting the yield of natural gas.
The realization principle of improving the oil recovery ratio by using the cellulose nano-fiber polymer-sodium chloride colloidal solution is as follows: after the cellulose nanofiber polymer-sodium chloride colloidal solution with a certain concentration and stable determination is injected into a stratum, the cellulose nanofiber polymer-sodium chloride colloidal solution flows into a communicating pore with a larger throat radius at first, and along with the flow of fluid, the cellulose nanofiber polymer is retained at the throat, so that the throat radius is narrowed, the inflow pressure is increased, and then the fluid flows into a passage with a narrower throat radius, the sweep efficiency is improved, and the recovery ratio is improved.
In the step, the implementation method for establishing the model body for simulating the distribution of the petroleum in the sandstone core according to the geological parameters stored in the crude oil comprises the following steps:
(a) performing pretreatment operation on the Berea sandstone core, wherein the pretreatment operation comprises cleaning and drying the Berea sandstone core and saturated soaking by using saline water;
(b) and injecting crude oil into the pretreated Berea sandstone core, and saturating the Berea sandstone core by the crude oil at a low flow rate of 1mL/min and at a high flow rate of 10mL/min in the injection process.
In addition, the concrete implementation steps of the pretreatment operation on the Berea sandstone core are as follows:
(I) cleaning the Berea sandstone core by using a 3% NaCl solution and methanol, drying, and measuring the dry weight, porosity and air permeability of the dried Berea sandstone core;
(II) soaking the Berea sandstone core by using a vacuum and saturated 0.1 wt% NaCl solution, and weighing the saturated wet weight of the Berea sandstone core;
(III) injecting the filtered crude oil obtained in the step 100 into the Berea sandstone core, displacing NaCl solution in the Berea sandstone core to leach until the inflow and outflow of the crude oil are consistent, and calculating the irreducible water saturation of the Berea sandstone core at the moment, wherein the irreducible water saturation of the Berea sandstone core measured by the embodiment is 46.74%;
when the filtered crude oil obtained in the step 100 is injected into the Berea sandstone core, the crude oil is injected at the low speed of 1mL/min, and after the crude oil is stabilized, the crude oil is injected at the high speed of 10 mL/min.
It should be added that, after the filtered crude oil obtained in the step 100 is injected into the Berea sandstone core and the irreducible water saturation of the Berea sandstone core at this time is calculated, the Berea sandstone core is soaked in the crude oil obtained in the step 100 and stands still, so that the pores of the Berea sandstone core are fully saturated with the crude oil.
As one of the innovative points of the embodiment, the amount of oil injected into the sandstone can be calculated in real time by injecting an appropriate amount of oil until saturation according to the porosity and air permeability of the sandstone, and the influence of the displacement experiment of the cellulose nanofiber polymer-sodium chloride mixed colloid solution on oil recovery and the data change of oil recovery rate can be calculated based on the amount of oil injected into the sandstone.
Step 400, injecting the screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution into the model main body according to a twice-displacement mode, comparing output liquid of the twice-displacement mode, and comparing the recovery ratio of the twice-displacement mode by calculating the ratio of the output liquid to the injection amount of crude oil.
It should be particularly noted that in steps 300 and 400, the sandstone core is always placed in a high-temperature and high-pressure environment for pretreatment and crude oil injection to simulate a real crude oil storage environment, so as to simulate real crude oil development efficiency.
Specifically, when the cellulose nanofiber polymer-sodium chloride mixed colloidal solution is injected into the model main body, two displacement tests are carried out to simulate oil recovery, and the specific implementation method comprises the following steps:
step 401, performing a primary oil recovery displacement experiment on a 0.1 wt% sodium chloride solution by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a first output liquid by using a test tube with scales;
step 402, stopping injecting the sodium chloride solution when no obvious oil drop is visible in the produced liquid and the pressure difference is stable, performing a secondary oil recovery displacement experiment on the screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution with the appropriate concentration range by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a second produced liquid again;
and step 403, stopping injecting the cellulose nanofiber polymer-sodium chloride mixed colloidal solution when no obvious oil drop is visible in the second output liquid and the pressure difference is stable.
And step 404, respectively calculating the recovery ratio of the primary oil recovery displacement experiment and the recovery ratio of the secondary oil recovery displacement experiment, and calculating the recovery ratio enhancement range of the secondary oil recovery displacement experiment by using the cellulose nanofiber polymer-sodium chloride mixed colloidal solution.
It should be added that cellulose nanofibers are entangled macromolecules with a length of up to micrometer scale. Unlike cellulose nanofiber polymers, it contains both crystalline and amorphous regions. Due to the ultra-high aspect ratio and the winding degree of the nanofiber, the nanofiber has higher strength and modulus under the same concentration of the nanocellulose.
Specific experimental results are shown in fig. 6 and 7, and the experimental results show that the entanglement of the elongated particles makes the ultra-low concentration dispersion highly viscous, and does not flow out even if the test tube containing the displacement fluid is inverted. In the tertiary oil recovery displacement process, the colloidal solution firstly flows into the channel with smaller resistance, and when the colloidal solution flows through the throat, the flow velocity is increased due to the small inner diameter.
As a second innovation of the present embodiment, since the Tempo-CNF particles are large, the significant mass difference between the particles and water molecules makes the flow velocity of water molecules larger than that of nanofiber particles, which causes large particles to gradually accumulate at the throat. This phenomenon causes a decrease in permeability, an increase in injection pressure, and displacement fluid flows to the pore throats with greater resistance, displacing more crude oil. In principle, the method increases the recovery ratio by increasing the sweep efficiency. In addition, the TEMPO-CNF-NaCl colloidal solution has high viscosity, so that the fluidity ratio of the displacement phase to the displaced phase is reduced, and the method belongs to the field of improving the oil washing efficiency and improving the recovery ratio in principle. The experimental result shows that the recovery ratio of the 0.1 wt% Tempo-CNF colloid solution prepared by 0.1 wt% sodium chloride solution for three times of displacement is 39.13% on the basis of the 0.1 wt% sodium chloride solution for two times of displacement.
The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to be within the scope of the present application.
Claims (10)
1. A method for simulating oil recovery by using a cellulose nanofiber polymer is characterized by comprising the following steps:
step 100, processing crude oil, and filtering the crude oil by using a vacuum filter and filter paper;
200, preparing a cellulose nanofiber polymer-sodium chloride mixed colloidal solution, and screening out the concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution beneficial to petroleum recovery;
step 300, establishing a model main body for simulating the distribution of petroleum in the sandstone core according to geological parameters stored in crude oil, slowly injecting the crude oil filtered in the step 100 into the pretreated sandstone core to simulate the storage environment of the crude oil in the sandstone core, and counting the injection amount of the crude oil in real time;
step 400, injecting the secondarily screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution into the model main body according to a twice-displacement mode, comparing output liquids of the twice-displacement mode, and comparing the recovery ratio of the twice-displacement mode by calculating the ratio of the output liquid to the injection amount of crude oil.
2. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 1, wherein the step 300 of establishing a model body for simulating crude oil distribution and formation storage according to the geological parameters of crude oil storage is implemented by:
performing pretreatment operation on the Berea sandstone core, wherein the pretreatment operation comprises cleaning and drying the Berea sandstone core and saturated soaking by using saline water;
and injecting crude oil into the pretreated Berea sandstone core, and saturating the Berea sandstone core by the crude oil at a low flow rate of 1mL/min and a high flow rate of 10mL/min in the injection process.
3. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 2, characterized in that: the concrete implementation steps of carrying out pretreatment operation on the Berea sandstone core are as follows:
washing the Berea sandstone core by using a 3% NaCl solution and methanol, drying, and measuring the dry weight, porosity and air permeability of the dried Berea sandstone core;
soaking the Berea sandstone core by using a vacuum and saturated 0.1 wt% NaCl solution, and weighing the saturated wet weight of the Berea sandstone core;
and (3) injecting the filtered crude oil obtained in the step (100) into the Berea sandstone core, displacing NaCl solution in the Berea sandstone core to leach until the inlet flow and the outlet flow of the crude oil are consistent, and calculating the saturation of the irreducible water of the Berea sandstone core at the moment.
4. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 3, characterized in that: when the filtered crude oil obtained in the step 100 is injected into the Berea sandstone core, the crude oil is injected according to the frequency of 1mL/min, and the crude oil is injected at the frequency of 10mL/min after the crude oil is stabilized.
5. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 3, characterized in that: and injecting the filtered crude oil obtained in the step 100 into the Berea sandstone core, calculating the saturation of the irreducible water of the Berea sandstone core at the moment, soaking the Berea sandstone core in the crude oil obtained in the step 100, and standing to fully saturate the pores of the Berea sandstone core with the crude oil.
6. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 1, wherein the step of preparing the cellulose nanofiber polymer-sodium chloride mixed colloidal solution in step 200 is implemented by the steps of:
obtaining an original concentrated solution of cellulose nanofiber polymer colloid;
mixing and diluting deionized water and the original cellulose nanofiber polymer to form cellulose nanofiber polymer colloid solutions with different concentrations;
mixing sodium chloride solutions with different concentrations with the original cellulose nano-fiber polymer colloidal solution to dilute the cellulose nano-fiber polymer colloidal solution into different concentrations and generate different classes of the cellulose nano-fiber polymer-sodium chloride mixed colloidal solution;
uniformly stirring the cellulose nanofiber polymer-sodium chloride mixed colloidal solution of the same category, dividing the mixed colloidal solution into two groups, respectively storing the two groups of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution in constant temperature boxes at 20 ℃ and 60 ℃, and judging the stability of all the cellulose nanofiber polymer-sodium chloride mixed colloidal solutions by regularly measuring the particle size and zeta potential.
7. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 6, wherein the specific implementation method for screening the stable concentration of the cellulose nanofiber polymer-sodium chloride mixed colloid solution by using the stability measuring method in step 200 is as follows:
sampling the cellulose nanofiber polymer-sodium chloride mixed colloidal solution stored in a constant temperature box at 20 ℃ and 60 ℃ at regular time to carry out a stability measurement experiment;
and comparing the measurement results of each stability measurement experiment, and screening out the cellulose nano-fiber polymer-sodium chloride colloidal solution which is still stable after being prepared for one month.
8. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 6, characterized in that: in step 200, the cellulose nanofiber polymer-sodium chloride mixed colloidal solution with a stable concentration range is screened out by detecting an interfacial tension measurement mode and a contact angle measurement mode to obtain the concentration of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution which is beneficial to improving the recovery ratio, and the specific implementation method is as follows:
performing an interfacial tension measurement experiment on crude oil and the cellulose nano-fiber polymer-sodium chloride colloidal solution screened to maintain stability, performing a measurement experiment on a contact angle between the cellulose nano-fiber polymer-sodium chloride colloidal solution and the sandstone surface, further screening the cellulose nano-fiber polymer-sodium chloride colloidal solution with a proper concentration range from the stable cellulose nano-fiber polymer-sodium chloride colloidal solution to screen out the concentration of the cellulose nano-fiber polymer-sodium chloride colloidal system affecting the permeability in the sandstone,
specifically, the contact angle between the cellulose nanofiber polymer-sodium chloride mixed colloidal solution and the sandstone surface is calculated by using a contact angle measurement mode, namely, the polished sandstone is soaked in the crude oil environment in step 100 in advance to be saturated and aged, and the contact angle of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution drop on the polished sandstone surface is calculated.
9. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 8, wherein in step 400, the cellulose nanofiber polymer-sodium chloride mixed colloid solution is injected into the model main body, oil recovery is simulated by two-time displacement mode, and the specific implementation method for calculating the oil recovery rate of each displacement mode is as follows:
step 401, performing a primary oil recovery displacement experiment on a 0.1 wt% sodium chloride solution by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a first output liquid by using a test tube with scales;
step 402, stopping injecting the sodium chloride solution when no obvious oil drop is visible in the produced liquid and the pressure difference is stable, performing a secondary oil recovery displacement experiment on the screened cellulose nanofiber polymer-sodium chloride mixed colloidal solution with the appropriate concentration range by adopting a sequence of low flow rate of 0.3mL/min and high flow rate of 3mL/min, and collecting a second produced liquid again;
and step 403, stopping injecting the cellulose nanofiber polymer-sodium chloride mixed colloidal solution when no obvious oil drop is visible in the second output liquid and the pressure difference is stable.
And 404, respectively calculating the recovery ratio of the primary oil recovery displacement experiment and the recovery ratio of the secondary oil recovery displacement experiment, and calculating the recovery ratio enhancement range of the secondary oil recovery displacement experiment by using the cellulose nanofiber polymer-sodium chloride mixed colloidal solution.
10. The method for simulating oil recovery using cellulose nanofiber polymer as claimed in claim 9, characterized in that: in step 403, after stopping the injection of the cellulose nanofiber polymer-sodium chloride mixed colloidal solution, a 0.1 wt% sodium chloride solution is injected to flush out the retained cellulose nanofiber polymer in the Berea sandstone core.
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