CN113552149A - Method for quantitatively representing shale wettability by using small-angle neutron scattering - Google Patents
Method for quantitatively representing shale wettability by using small-angle neutron scattering Download PDFInfo
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- 238000009826 distribution Methods 0.000 claims abstract description 56
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Abstract
The application provides a method for quantitatively representing shale wettability by using small-angle neutron scattering, which comprises the following steps: s1, preparing a shale sample to be detected; s2, performing a small-angle neutron scattering experiment on the shale sample to be detected to respectively obtain a first shale pore volume and pore diameter distribution diagram of each shale sample to be detected; s3, preparing a mixed solution; s4, soaking the shale sample to be tested in the mixed solution; s5, performing a small-angle neutron scattering experiment on each shale sample to be detected respectively to obtain a second pore volume and pore diameter distribution map of each shale sample to be detected; and comparing and analyzing the result in the corresponding first pore volume and pore diameter distribution diagram with the result in the second pore volume and pore diameter distribution diagram, and quantitatively characterizing the shale wettability of each shale sample to be tested. The method can be used for accurately and quantitatively characterizing the wettability of the microscopic pores of the shale, and is small in error.
Description
Technical Field
The application relates to the field of unconventional natural gas, in particular to a method for quantitatively representing shale wettability by using small-angle neutron scattering.
Background
The wettability of shale is one of important parameters for representing rock physical characteristics, and has important influences on oil and gas distribution, residual oil saturation, capillary force, relative permeability, water flooding effect in the exploitation process and the like in a shale pore space. Therefore, the wettability of the reservoir can be accurately judged in the shale oil and gas exploitation process, and the method has indication significance for optimizing exploitation, backflow of fracturing fluid, water-rock interaction and selection of the fracturing fluid and additives.
The existing methods for researching wettability include two major types, namely quantitative analysis method and qualitative analysis method, wherein the quantitative analysis method comprises a contact angle method, a dripping experiment, a fluid self-absorption-displacement method, nuclear magnetic resonance, a water film flotation method and the like, and the qualitative analysis method comprises a self-absorption rate method, a microscopic observation method, a relative permeability method, a capillary pressure curve method, a well logging curve method and the like. It is noted that these methods all use different parameter criteria to judge the wettability characteristics of the rock, so different experimental means may obtain different results for the same sample, and multiple testing methods are required to be used for mutual verification.
Disclosure of Invention
One of the purposes of the present application is to provide a method for quantitatively characterizing shale wettability by using small-angle neutron scattering, which aims to solve the problem of low accuracy of existing shale wettability testing.
The technical scheme of the application is as follows:
a method for quantitatively characterizing shale wettability by small-angle neutron scattering, comprising the steps of:
s1, preparing a plurality of shale samples to be detected;
s2, performing a small-angle neutron scattering experiment on each shale sample to be detected respectively, obtaining accessible pore proportions on original different pore size distributions of each shale sample to be detected respectively, and obtaining a first-time shale pore volume and pore size distribution map of each shale sample to be detected respectively;
s3, respectively preparing mixed solutions matched with the average scattering length density value of the shale sample to be detected, wherein the average scattering length density value is required by the experiment;
s4, putting the shale samples to be tested into the prepared mixed solution, and fully infiltrating each shale sample to be tested;
s5, performing a small-angle neutron scattering experiment on each fully soaked shale sample to be detected respectively to obtain accessible pore proportions on different pore size distributions of each wetted shale sample to be detected respectively, and obtaining a second pore volume and pore size distribution map of each shale sample to be detected respectively; and comparing and analyzing the corresponding experimental result in the first pore volume and pore diameter distribution diagram with the experimental result in the second pore volume and pore diameter distribution diagram, and quantitatively characterizing the shale wettability of each shale sample to be tested.
As a technical solution of the present application, in step S1, the specific operation of preparing the shale sample to be tested is: and preparing the shale sample to be detected into a granular sample with the grain size of 0.5mm and uniform grain size.
As a technical solution of the present application, in step S2, before performing a small-angle neutron scattering experiment on the shale sample to be tested, the shale sample to be tested is first placed in an oven at 60 ℃ to be dried for more than 24 hours until the quality of the shale sample to be tested does not change any more.
As one technical solution of the present application, in step S3, the mixed solutions with different scattering length density values are configured according to different experimental contents, and the scattering length density values of the different mixed solutions are calculated by the following formula:
if the volume ratio of the components of the mixed solution is known as V1: v2: v3: … … Vi: … … Vn, the scattering length density of the mixed solution can be calculated by the following formula:
ρmix＝x1ρ1+x2ρ2+…+xiρi+…+xnρn；
in the formula: rho i is the scattering length density of the ith component in the mixed solution; chi i is the volume percentage of the ith component, namely:
χi＝Vi/(V1+V2+V3+…+Vn)。
as one technical solution of the present application, in step S3, the mixed solution is a water mixed solution and a toluene mixed solution.
As a technical solution of the present application, in step S4, the corresponding shale particles of each shale sample to be tested and the mixed solution are loaded into a standard quartz container with a thickness of 1mm, and the shale particles of the shale sample to be tested are fully soaked in the mixed solution.
As a technical solution of the present application, in step S5, the specific operation of quantitatively characterizing the shale wettability of each shale sample to be tested is as follows:
performing a small-angle neutron scattering experiment on the shale sample to be detected prepared in the step S1 to obtain a first pore volume distribution-pore diameter distribution curve of the shale sample to be detected; performing a small-angle neutron scattering experiment on the shale sample to be detected which is fully soaked in the step S4 to obtain a second pore volume distribution-pore diameter distribution curve of the shale sample to be detected; and comparing and analyzing the obtained first pore volume distribution-pore diameter distribution curve and the obtained second pore volume distribution-pore diameter distribution curve, and carrying out quantitative characterization on the shale wettability of the shale sample to be tested.
The beneficial effect of this application:
the method for quantitatively representing the wettability of the shale by using the small-angle neutron scattering is combined with the small-angle neutron scattering technology, the accessibility of different fluids in the shale can be detected, so that a new way for quantitatively representing the wettability of the shale at home and abroad is provided, the method is economical and rapid, the wettability of microscopic pores of the shale can be quantitatively represented more accurately, the error is small, and the precision is high.
Drawings
In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that for those skilled in the art, other related drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic diagram of a comparative shale matrix matching experiment provided in an example of the present application;
FIG. 2 is a graph comparing pore volume distribution versus pore diameter curves for three small angle neutron scattering experiments for a sample of W201-2 provided in an example of the present application;
FIG. 3 is a graph of a wettability index distribution of a W201-2 sample provided in an embodiment of the present application;
FIG. 4 is a graph comparing pore volume distribution versus pore diameter curves for three small angle neutron scattering experiments for samples of W201-8 provided in examples herein;
FIG. 5 is a graph of the wettability index distribution of a sample W201-8 provided in an embodiment of the present application;
FIG. 6 is a graph comparing pore volume distribution versus pore diameter curves for three small angle neutron scattering experiments for TY1-20 samples provided in examples herein;
FIG. 7 is a graph of the wettability index profile of a TY1-20 sample provided in an example of the present application;
FIG. 8 is a graph comparing pore volume distribution versus pore diameter curves for three small angle neutron scattering experiments for RY2-18 samples provided in examples herein;
FIG. 9 is a graph of the wettability index distribution of RY2-18 samples provided in the examples herein.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. 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 application.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present application, it should be noted that the terms "upper", "lower", and the like refer to orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the present invention are conventionally placed in use, and are used for convenience in describing the present application and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present application.
Further, in the present application, unless expressly stated or limited otherwise, the first feature may be directly contacting the second feature or may be directly contacting the second feature, or the first and second features may be contacted with each other through another feature therebetween, not directly contacting the second feature. Also, the first feature being above, on or above the second feature includes the first feature being directly above and obliquely above the second feature, or merely means that the first feature is at a higher level than the second feature. A first feature that underlies, and underlies a second feature includes a first feature that is directly under and obliquely under a second feature, or simply means that the first feature is at a lesser level than the second feature.
Furthermore, the terms "horizontal", "vertical" and the like do not imply that the components are required to be absolutely horizontal or pendant, but rather may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.
In the description of the present application, it is also to be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
Example (b):
the method for quantitatively representing the shale wettability by using the small-angle neutron scattering is implemented based on the following principle:
after the neutron beam is generated, the incident beam is collimated and irradiated onto the shale sample. Due to the different scattering length densities of the pore space and the shale solid matrix, the incident beam will elastically scatter in the shale sample. The SLD (i.e., the scattering length density) of each component in shale depends on its chemical composition and density, reflecting the scattering power per unit volume of that component. Therefore, the small-angle neutron scattering experiments are respectively carried out on the original shale sample and the sample after the shale and the mixed solution are completely soaked, and different results can be obtained: as shown in fig. 1, panel a in fig. 1 is the original shale void network diagram, panel b in fig. 1 is the graph of the connected void space occupied by the contrast matched fluid obtained after infiltration of shale particles into the same fluid as the SLD of the shale matrix, and panel c in fig. 1 is the graph of the pores inaccessible to the small angle neutron scattering characterization shale fluid.
Based on the above principle, scattering intensity information is analyzed by using an IRENA plug-in interface of IGORPro (data analysis and mapping software) and a polydisperse sphere model, so as to obtain the pore structure parameters of the scatterer. Fitting the small-angle neutron scattering curve of the shale sample by a non-negative least square method, further solving the porosity, the pore number density (the number of pores in unit volume), the specific surface area and the pore size distribution of the shale sample by a polydisperse pore size distribution model, and then carrying out quantitative characterization on the comparative shale wettability by different experimental data.
In view of the foregoing principle, referring to fig. 1 in combination with fig. 2 to 9, the present application provides a method for quantitatively characterizing shale wettability by using small-angle neutron scattering, which mainly includes the following steps:
s1, preparing a plurality of shale samples to be tested: in this embodiment, the preparation method of the shale sample to be tested includes: in the experiment, four different shale samples to be detected, namely W201-2, W201-8, TY1-20 and RY2-18 are selected for preparing the shale sample to be detected; preparing the four shale samples to be detected into particle powder samples with the particle size of about 0.5mm and uniform particle size; then, respectively placing the four shale samples to be tested in an oven at 60 ℃ for drying for more than 24 hours until the mass of the four shale samples to be tested is not changed;
s2, performing a small-angle neutron scattering experiment on each shale sample to be tested, and obtaining a first shale pore volume and pore size distribution map (as shown in fig. 2, 4, 6, and 8) of each shale sample to be tested;
s3, preparing the mixed fluid required for the experiment: because of the difference of different experimental contents, mixed fluids with different SLD values (namely scattering length density) need to be configured according to the experimental contents; for example, to study the accessibility of water in shale, a mixed solution matching the average SLD value of the shale matrix needs to be prepared; the calculation principle is that, for the calculation of different SLD mixed solutions, if the volume ratio of each component of the mixed solution is known as V1: v2: v3: … … Vi: … …: vn, the scattering length density of the mixed solution can be calculated by the following formula:
ρmix＝x1ρ1+x2ρ2+…+xiρi+…+xnρn；
in the formula: rho i is the scattering length density of the ith component in the mixed solution; chi i is the volume percentage of the ith component, namely:
χi＝Vi/(V1+V2+V3+…+Vn)；
in order to study the wetting conditions of water and toluene in shale, a water mixed solution and a toluene mixed solution which are matched with the average SLD value of the shale matrix are respectively prepared based on the principle;
s4, after the mixed solution and the shale sample to be tested are prepared, the mixed solution and the shale particles are filled into a standard quartz container, and the shale particles are fully soaked in the mixed solution, wherein the soaking time is selected according to the purpose of the experiment; in the experiment, different shale samples to be tested are respectively wetted by the water mixed solution and the toluene mixed solution, and the natural imbibition time is 12 hours and 72 hours;
s5, performing a small-angle neutron scattering experiment on each shale sample to be tested which is fully infiltrated in step S4, respectively obtaining accessible pore proportions in different pore size distributions of each shale sample to be tested after being wetted, and respectively obtaining a second pore volume and pore size distribution map (as shown in fig. 2, fig. 4, fig. 6 and fig. 8) of each shale sample to be tested; and comparing and analyzing the corresponding experimental result in the pore volume and pore diameter distribution diagram of each first time shale with the experimental result in the pore volume and pore diameter distribution diagram of the second time shale, and respectively and quantitatively characterizing the shale wettability of each shale sample to be tested (as shown in fig. 3, fig. 5, fig. 7 and fig. 9).
It should be noted that, in this embodiment, in step S2, in this test, a granular sample is selected to obtain the pore structure information with average orientation, and the comparison and matching small-angle neutron scattering experiment is facilitated. The granules were screened to a particle size of 0.5mm and using the same particle size a lateral comparison was made with other tests such as mercury intrusion, N2 adsorption experiments. Then, a proper sample fixing mode is selected according to the form of the sample, the sheet sample can be directly fixed on the sample rack, the granular sample needs to be loaded by the sample pool, the powder sample needs to be uniformly and fully distributed in the sample pool, the powder sample needs to be compacted as much as possible, and the scattering performance of the used sample pool needs to be measured before the test. If contrast matched neutron scattering experiments are required, the corresponding fluid should be injected into a specially made sample bin prior to sample testing, using at least two standard quartz containers per sample for the experiments: one was used for SANS experiments in dry environments and the remainder for contrast-matched small-angle neutron scattering experiments.
Meanwhile, before each shale sample to be tested is tested on the computer, a spectrometer worker generally finishes the work of detector efficiency correction, wavelength correction, background correction, transmittance measurement and the like required by the sample of the batch. In the testing process of the shale sample to be tested, the thickness of the sample, the testing time and the wavelength of the adopted neutron beam current need to be recorded for subsequent data processing work.
It should be noted that, in step S5, in fig. 2, in the present embodiment, a first small-angle neutron scattering experiment is performed on a shale sample W201-2 to be tested, so as to obtain an original shale pore volume and pore size distribution curve of the sample W201-2 in the drawing; then, after the sample W201-2 is placed into a water mixed solution matched with the average SLD value of the experimental shale matrix for sufficient infiltration, a second small-angle neutron scattering experiment is carried out to obtain a shale pore volume and pore size distribution curve of the water mixed solution of the sample W201-2 in the graph; and finally, putting another sample which is subjected to the first small-angle neutron scattering experiment and is the same as the sample W201-2 into a toluene mixed solution matched with the average SLD value of the experimental shale matrix for full infiltration, and then performing a third small-angle neutron scattering experiment to obtain a shale pore volume and pore size distribution curve of the toluene mixed solution of the sample W201-2 in the graph.
Similarly, in fig. 4, a first small-angle neutron scattering experiment is performed on the shale sample W201-8 to be tested to obtain an original shale pore volume and pore size distribution curve of the sample W201-8 in the diagram; then, after the sample W201-8 is placed into a water mixed solution matched with the average SLD value of the experimental shale matrix for sufficient infiltration, a second small-angle neutron scattering experiment is carried out to obtain a shale pore volume and pore size distribution curve of the water mixed solution of the sample W201-8 in the graph; and finally, placing another sample which is subjected to the first small-angle neutron scattering experiment and is the same as the sample W201-8 into a toluene mixed solution matched with the average SLD value of the experimental shale matrix for full infiltration, and then performing a third small-angle neutron scattering experiment to obtain a shale pore volume and pore size distribution curve of the toluene mixed solution of the sample W201-8 in the graph.
Similarly, in fig. 6, firstly, a first small-angle neutron scattering experiment is performed on the shale sample TY1-20 to be tested, so as to obtain an original shale pore volume and pore size distribution curve of the sample TY1-20 in the diagram; then placing the sample TY1-20 into a water mixed solution matched with the average SLD value of the experimental shale matrix for sufficient infiltration, and then performing a second small-angle neutron scattering experiment to obtain a shale pore volume and pore size distribution curve of the water mixed solution of the sample TY1-20 in the figure; and finally, after another sample which is subjected to the first small-angle neutron scattering experiment and is the same as the sample TY1-20 is placed into a toluene mixed solution matched with the average SLD value of the experimental shale matrix to be fully soaked, a third small-angle neutron scattering experiment is carried out, and the shale pore volume and pore size distribution curve of the toluene mixed solution of the sample TY1-20 in the graph is obtained.
Similarly, in fig. 8, first, a first small-angle neutron scattering experiment is performed on the shale sample RY2-18 to be tested, so as to obtain an original shale pore volume and pore size distribution curve of the sample RY2-18 in the diagram; then placing the sample RY2-18 into a water mixed solution matched with the average SLD value of the experimental shale matrix for full infiltration, and then performing a second small-angle neutron scattering experiment to obtain a shale pore volume and pore size distribution curve of the water mixed solution of the sample RY2-18 in the figure; and finally, another sample which is subjected to the first small-angle neutron scattering experiment and is the same as the sample RY2-18 is placed into a toluene mixed solution matched with the average SLD value of the experimental shale matrix to be fully soaked, and then the third small-angle neutron scattering experiment is carried out, so that the shale pore volume and pore size distribution curve of the toluene mixed solution of the sample RY2-18 in the graph is obtained.
Note that, in the present embodiment, in step S3, the shale SLD ≈ 3.4 × 1010cm-2-4.7×1010cm-2(ii) a Meanwhile, the method for preparing the water mixed solution comprises the following steps: the SLD value of water is known to be H2O＝-0.56×1010cm-2The SLD value of deuterated water is D2O＝6.39×1010cm-2And mixing the two into a numerical value which is the same as the SLD value of the shale in the embodiment according to a certain proportion. In this experiment, two solutions were used for the preparation of the aqueous mixed solution, so that n is 2, and the values of i and n are determined by the prepared solution, and are generally 2; the specific volume is calculated according to the above formula.
In addition, in this embodiment, in step S3, the method for preparing the toluene mixed solution is as follows: the SLD value of toluene is known to be C7H8＝0.94×1010cm-2，C7D8Has an SLD value of 5.64X 1010cm-2And mixing the two into a numerical value which is the same as the SLD value of the shale in the embodiment according to a certain proportion.
In this embodiment, in step S5, as can be seen from fig. 2 to 9, the wettability of different shale samples to be tested is different and changes with the change of the pore diameter. In the W201-2 shale sample, the curve shows that at pore diameters less than 10nm, the volume of toluene in the pores is greater than the volume of water, indicating that more water is impregnated into the shale matrix of the shale sample to be tested within the pores, the water is more readily absorbed and therefore the sample is more hydrophilic in the range of less than 10 nm. When the pore diameter is larger than 10nm, the curve changes to that the water volume in the pores is larger than the toluene volume, which indicates that the toluene is more easily absorbed in the interval, namely when the pores are directly 10-100 nm, the sample shows lipophilicity. Similarly, the W201-8 and TY1-20 shale samples have the same characteristics, and both show hydrophilicity when the pore diameter is less than 10nm and show lipophilicity when the pore diameter is 10-100 nm. Unlike the first three samples, the RY2-18 shale sample curve indicates that the volume of toluene in the pores is always greater than the volume of water, indicating that hydrophilicity is always present in the pore range.
On the basis of the above-mentioned figure, further, according to the formula:
in the formula:
in order to be of a hydrophilic porosity,
is oleophilic porosity;
the difference between the two is used to reflect the wettability. Wherein the porosity is hydrophilic
The calculation method comprises the following steps: under the condition that the abscissa in the figure 2 is unchanged, subtracting the pore volume distribution value after the sample W201-2 in the figure 2 is completely soaked with the water mixed solution from the original shale pore volume distribution value, so as to obtain the hydrophilic porosity of the sample W201-2
A value of (d); similarly, the oleophylic porosity of the sample W201-2 can be obtained by subtracting the pore volume distribution after the completely soaking of the toluene mixed solution from the original shale pore volume distribution of the sample W201-2 in FIG. 2
Then, according to the formula, obtaining the wettability index Iw of the sample W201-2; the same treatment is then applied to all abscissas in fig. 2, resulting in the overall wettability index profile 3. And by analogy, the integral wettability index distribution curve chart of other three samples can be obtained.
As can be seen from fig. 2 to 9, when the Iw value is +1, it represents that the test sample is completely hydrophilic; when the Iw value is-1, the test sample is completely oleophilic; when the Iw value is 0, the test sample is neutral. Where a closer Iw value to +1 indicates a more hydrophilic, a closer value to-1 indicates a more lipophilic. The research results are shown in fig. 3, fig. 5, fig. 7 and fig. 9, and the same conclusion as the conclusion is reached, the wettability characteristics can be more intuitively shown on the image.
In summary, the method for quantitatively characterizing the shale wettability by using the small-angle neutron scattering according to the application has the characteristic of mixed wetting, so that increasing the shale oil and gas yield and recovery ratio by wettability inversion in the shale oil and gas development process is more and more emphasized. The method is combined with a small-angle neutron scattering technology, the accessibility of different fluids in the shale can be detected, so that a new way for quantitatively representing the wettability of the shale at home and abroad is provided, the method is economical and rapid, the wettability of the microscopic pores of the shale can be quantitatively represented more accurately, and the error is small.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (7)
1. A method for quantitatively characterizing shale wettability by using small-angle neutron scattering is characterized by comprising the following steps of:
s1, preparing a plurality of shale samples to be detected;
s2, performing a small-angle neutron scattering experiment on each shale sample to be detected respectively, obtaining accessible pore proportions on original different pore size distributions of each shale sample to be detected respectively, and obtaining a first-time shale pore volume and pore size distribution map of each shale sample to be detected respectively;
s3, respectively preparing mixed solutions matched with the average scattering length density value of the shale sample to be detected, wherein the average scattering length density value is required by the experiment;
s4, putting the shale samples to be tested into the prepared mixed solution, and fully infiltrating each shale sample to be tested;
s5, performing a small-angle neutron scattering experiment on each fully soaked shale sample to be detected respectively to obtain accessible pore proportions on different pore size distributions of each wetted shale sample to be detected respectively, and obtaining a second pore volume and pore size distribution map of each shale sample to be detected respectively; and comparing and analyzing the corresponding experimental result in the first pore volume and pore diameter distribution diagram with the experimental result in the second pore volume and pore diameter distribution diagram, and quantitatively characterizing the shale wettability of each shale sample to be tested.
2. The method for quantitatively characterizing shale wettability by using small-angle neutron scattering according to claim 1, wherein in step S1, the specific operation of preparing the shale sample to be tested is: and preparing the shale sample to be detected into a granular sample with the grain size of 0.5mm and uniform grain size.
3. The method for quantitatively characterizing shale wettability by using small-angle neutron scattering according to claim 1, wherein in step S2, before the small-angle neutron scattering experiment is performed on the shale sample to be tested, the shale sample to be tested is dried in an oven at 60 ℃ for more than 24 hours until the quality of the shale sample to be tested does not change any more.
4. The method for quantitative characterization of shale wettability by small-angle neutron scattering according to claim 1, wherein in step S3, said mixed solutions with different scattering length density values are configured according to different experimental contents, and the scattering length density values of different said mixed solutions are calculated by the following formula:
if the volume ratio of the components of the mixed solution is known as V1: v2: v3: … … Vi: … … Vn, the scattering length density of the mixed solution can be calculated by the following formula:
ρmix＝x1ρ1+x2ρ2+…+xiρi+…+xnρn；
in the formula: rho i is the scattering length density of the ith component in the mixed solution; chi i is the volume percentage of the ith component, namely:
χi＝Vi/(V1+V2+V3+…+Vn)。
5. the method for quantitatively characterizing shale wettability by using small-angle neutron scattering according to claim 1, wherein in step S3, the mixed solution is a water mixed solution and a toluene mixed solution.
6. The method for quantitatively characterizing shale wettability by using small-angle neutron scattering according to claim 1, wherein in step S4, the corresponding shale particles of each shale sample to be tested and the mixed solution are filled into a standard quartz container with a thickness of 1mm, and the shale particles of the shale sample to be tested are fully infiltrated in the mixed solution.
7. The method for quantitatively characterizing shale wettability by using small-angle neutron scattering according to claim 1, wherein in step S5, the specific operation of quantitatively characterizing the shale wettability of each shale sample to be tested is as follows:
performing a small-angle neutron scattering experiment on the shale sample to be detected prepared in the step S1 to obtain a first pore volume distribution-pore diameter distribution curve of the shale sample to be detected; performing a small-angle neutron scattering experiment on the shale sample to be detected which is fully soaked in the step S4 to obtain a second pore volume distribution-pore diameter distribution curve of the shale sample to be detected; and comparing and analyzing the obtained first pore volume distribution-pore diameter distribution curve and the obtained second pore volume distribution-pore diameter distribution curve, and carrying out quantitative characterization on the shale wettability of the shale sample to be tested.
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Effective date of registration: 20230809 Address after: 100728 No. 22 North Main Street, Chaoyang District, Beijing, Chaoyangmen Applicant after: CHINA PETROLEUM & CHEMICAL Corp. Applicant after: JIANGHAN OILFIELD BRANCH, CHINA PETROLEUM & CHEMICAL Corp. Address before: 430223 No. 18, University Park Road, Donghu high tech Zone, Wuhan City, Hubei Province (Huashi science and Technology Park) Applicant before: EXPLORATION AND DEVELOPMENT RESEARCH INSTITUTE OF SINOPEC JIANGHAN OILFIELD CO. |