Method for extracting, preparing and detecting organic clay complex in shale

Abstract

The invention relates to the technical field of test sample preparation, in particular to a method for extracting, preparing and detecting an organic clay complex in shale, which comprises the following steps: after more accurate organic clay complex particle extraction is carried out through three-level control, respectively collecting X-ray diffraction spectrum and attenuated total reflection infrared spectrum data of the organic clay complex; performing wavelet denoising process correction on attenuated total reflection infrared spectrum data of the organic clay complex, specifically, performing self-adaptive correction on a wavelet threshold value of each layer through baseline offset response represented by interlayer information change difference; therefore, the noise processing process has better adaptivity and robustness when reconstruction is carried out based on the corrected wavelet threshold, so that the finally obtained corrected infrared spectrum data is more accurate, and more accurate organic clay complex detection is carried out in combination with an X-ray diffraction spectrum.

Description

Technical Field

[0001] The present invention relates to the technical field of test sample preparation, and in particular to a method for extracting, preparing and detecting an organoclay complex in shale. Background Art

[0002] Organoclay complexes generally refer to complexes formed by the chemical bonding or mutual adsorption of organic matter and clay minerals. They include complexes formed by surface adsorption of clay minerals and interlayer incorporation of organic matter. Organoclay complexes are the core carriers of hydrocarbon occurrence and migration in unconventional reservoirs such as shale and mudstone. Their research involves multiple disciplines such as crystal chemistry, organic chemistry, geology, and soil science. They are a bridge connecting organic and inorganic, and have a significant impact on the study of shale hydrocarbon generation and migration. Therefore, the extraction, preparation, and detection of organoclay complexes in shale are very critical.

[0003] Existing methods for extracting organoclay complexes are similar to those for kerogen extraction in national standards, specifically including suspension extraction and acid washing. After extracting organoclay complex samples using suspension extraction or acid washing, the attenuated total reflectance infrared spectroscopy data is subjected to discrete wavelet transform denoising for organoclay complex detection. The suspension extraction method specifically involves crushing the shale sample and immersing it in deionized water, then using sedimentation and suspension to extract the smaller particles. The acid washing method specifically involves using hydrochloric acid and hydrofluoric acid to remove carbonate and silicate minerals from the shale, thereby separating the organic components.

[0004] However, considering that clay minerals are hydrophilic and have small particle sizes, extracts often contain excessive amounts of clay minerals, and not all clay minerals form organoclay complexes. Therefore, suspension extraction is ineffective for non-black shales with low organic matter content. Furthermore, the acid wash method, because strong acid is used to dissolve carbonate and silicate minerals, significantly destroys the original complex structure, resulting in an excessively high organic matter content in the extract, essentially encapsulating the organoclay complex. Therefore, the acid wash method is also less effective for extracting and preparing organoclay complexes. Furthermore, prior art methods typically employ a fixed wavelet threshold for denoising and reconstruction when performing wavelet decomposition and denoising on attenuated total reflection infrared spectroscopy data of organoclay complex samples. However, the degree of baseline shift typically varies under different environments. Using a fixed wavelet threshold for denoising can result in signal distortion or poor denoising, leading to poor detection accuracy for organoclay complexes. Consequently, prior art methods are less effective for extracting and preparing organoclay complexes from shale, as well as for detecting them accurately. Summary of the Invention

[0005] In order to solve the technical problem that the existing technology has poor extraction and preparation effect and detection accuracy of organoclay complexes in shale, the purpose of this application is to provide a method for extracting, preparing and detecting organoclay complexes in shale. The technical solution adopted is as follows:

[0006] This application proposes a method for detecting organoclay complexes in shale, which includes:

[0007] The shale sample was crushed into powder using a grinder and then added to a glass beaker; deionized water was poured into the glass beaker, the shale sample was soaked, and carbonaceous debris floating on the surface was skimmed off;

[0008] After wet grinding the soaked shale sample, soak it again and disperse it with ultrasound to obtain a suspension; after stirring the suspension and letting it stand, extract the upper liquid of the suspension and pour it into a polypropylene beaker to obtain a mixture solution;

[0009] After the mixture solution in the polypropylene beaker was dried at low temperature, powder was scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample;

[0010] Obtaining X-ray diffraction patterns and attenuated total reflection infrared spectroscopy data of the organoclay composite sample;

[0011] Decomposing the attenuated total reflection infrared spectrum data by discrete wavelet transform to obtain a wavelet coefficient curve corresponding to each layer; wherein the wavelet coefficient curve includes a high-frequency wavelet coefficient curve and a low-frequency wavelet coefficient curve; determining a baseline shift response value for each layer based on the difference in fluctuations between the wavelet coefficient curves corresponding to each layer and those of other layers;

[0012] The initial wavelet threshold of each layer is corrected using the baseline shift response value as a weight to determine the corresponding corrected wavelet threshold; the wavelet coefficient curve is subjected to baseline retention threshold processing and reconstructed according to the corrected wavelet threshold to determine a baseline spectrum curve; the attenuated total reflection infrared spectrum data is baseline corrected according to the baseline spectrum curve to determine corrected infrared spectrum data; and the organoclay complex is detected based on the X-ray diffraction pattern and the corrected infrared spectrum data.

[0013] Furthermore, the process of crushing the shale sample into powder using a crusher and then adding the powder into a glass beaker includes:

[0014] The shale sample was first crushed to less than 1 mm using a jaw crusher, and 30 g of powder was weighed and placed in a 500 ml tall glass beaker.

[0015] Furthermore, the process of injecting deionized water into the glass beaker, soaking the shale sample, and skimming off carbonaceous debris floating on the surface thereof includes:

[0016] Pour 200 ml of deionized water into a glass beaker, soak the shale sample for 24 hours, and then use absorbent cotton to skim off the carbonaceous debris floating on the surface.

[0017] Furthermore, the process of obtaining the suspension includes:

[0018] The soaked sample was wet-ground in a grinding jar using a hybrid ball mill at a vibration frequency of 5 times per second for 10 minutes to obtain a wet-ground shale sample; the wet-ground shale sample was poured back into a glass beaker and filled with deionized water to obtain a mixed solution; the mixed solution was shaken by an ultrasonic disruptor to obtain a suspension.

[0019] Furthermore, the process of obtaining the mixture solution includes:

[0020] Repeat the stirring process, the standing process, the pouring process, and the water adding process in this order until the mixture solution in the polypropylene beaker reaches the preset sample volume requirement;

[0021] The stirring process includes stirring the suspension in the glass beaker; the standing process includes standing the suspension for 24 hours; the pouring process includes pouring 200 ml of the upper suspension into a 5000 ml polypropylene beaker; and the water adding process includes adding 200 ml of deionized water into the glass beaker.

[0022] Furthermore, the process of obtaining the organoclay complex sample includes:

[0023] The polypropylene beaker containing the mixture solution was placed in an oven in a tilted state and dried at a low temperature of 60 degrees Celsius. The powder on the wall of the polypropylene beaker was scraped off with a plastic tool to obtain an organoclay composite sample.

[0024] Furthermore, the process of obtaining the X-ray diffraction pattern includes:

[0025] The organoclay composite sample is placed in an agate mortar and ground until there is no granularity, and then a sample tablet is prepared by powder pressing. The sample tablet is processed by an X-ray diffractometer to obtain an X-ray diffraction pattern of the organoclay composite sample.

[0026] Furthermore, the process of obtaining the baseline shift response value includes:

[0027] Obtain the number of extreme points, upper envelope, and lower envelope of each wavelet coefficient curve; perform a uniform sampling operation on each wavelet coefficient curve based on the number of extreme points to obtain sampling points of each wavelet coefficient curve; arrange the numerical differences between the upper envelope and the lower envelope corresponding to all sampling points of each wavelet coefficient curve in sequence to form a sequence as the wavelet feature sequence of each wavelet coefficient curve; arrange the mean, variance, standard deviation, and range of all curve values ​​of the wavelet feature sequence in sequence to form a vector as the wavelet feature vector;

[0028] The cosine similarity between the wavelet feature vector of the high-frequency wavelet coefficient curve and the wavelet feature vector of the low-frequency wavelet coefficient curve corresponding to each layer is used as the feature similarity corresponding to each layer;

[0029] The baseline shift response value of each layer is determined by normalizing the mean difference between the feature similarity of each layer and the feature similarity of other layers.

[0030] Furthermore, the process of obtaining the modified wavelet threshold includes:

[0031] The product of the negative correlation mapping value of the baseline shift response value and the preset initial wavelet threshold corresponding to each layer is used as the modified wavelet threshold of each layer.

[0032] Furthermore, the process of obtaining the baseline spectrum curve includes:

[0033] According to the modified wavelet threshold, hard threshold processing is performed on the high-frequency wavelet coefficient curve of each layer to obtain a hard threshold processing curve; according to the modified wavelet threshold, soft threshold processing is performed on the low-frequency wavelet coefficient curve of each layer to obtain a soft threshold processing curve; wavelet reconstruction is performed using a reconstruction algorithm based on all soft threshold processing curves and all hard threshold processing curves corresponding to all layers to obtain a baseline spectral curve.

[0034] Furthermore, the process of obtaining the corrected infrared spectrum data includes:

[0035] The baseline spectrum curve is subtracted from the curve corresponding to the attenuated total reflection infrared spectrum data to obtain corrected infrared spectrum data.

[0036] This application also proposes a method for extracting and preparing an organoclay complex from shale, the preparation method comprising:

[0037] The shale sample was crushed into powder using a grinder and then added to a glass beaker; deionized water was poured into the glass beaker, the shale sample was soaked, and carbonaceous debris floating on the surface was skimmed off;

[0038] After wet grinding the soaked shale sample, soak it again and disperse it with ultrasound to obtain a suspension; after stirring the suspension and letting it stand, extract the upper liquid of the suspension and pour it into a polypropylene beaker to obtain a mixture solution;

[0039] After the mixture solution in the polypropylene beaker was dried at low temperature, powder was scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample.

[0040] This application has the following beneficial effects:

[0041] This application is mainly based on the characteristics of a large number of shale samples of organic clay complex particles with small particle size, low density, and easy adhesion to the surface of plastic beakers. The solution comprehensively uses the suspension extraction method to control the particle size of the extracted particles to clay grade; through adsorption on the surface of the polypropylene beaker, the particles compounded with organic components are screened out. In addition, by skimming the organic debris floating on the surface, the non-composite organic components are eliminated, and the organic clay complex particles that meet the requirements can be selected through three-level control; when crushing the sample, it is mainly through long-term low-frequency wet grinding to reversely simulate the sedimentation process, so as to achieve both sufficient dissolution of shale particles and avoid the destruction of mineral particles and organic clay complex particles during the mechanical grinding process in the existing method; in addition, the extraction of clay complex particles adopts the method of low-temperature drying, which can avoid the problem of insufficient centrifugal speed in the centrifuge method, which makes it impossible to destroy the colloidal state of the organic clay complex in the solution and prevent effective precipitation.

[0042] In the process of denoising the attenuated total reflection infrared spectral data, in order to further accurately analyze the baseline shift phenomenon caused by interference factors in the infrared spectral data of organic clay complexes at different scales and frequency ranges, the acquired attenuated total reflection infrared spectral data are decomposed, and then the information change differences between the different decomposed layers are compared and analyzed. The baseline shift response value obtained according to the comparative analysis results is adaptively corrected by the wavelet threshold, so that the noise processing process has better adaptability and robustness when reconstructing based on the corrected wavelet threshold, making the final corrected infrared spectral data more accurate, thereby combining with the X-ray diffraction pattern for more accurate detection of organic clay complexes.

[0043] In summary, the method for extracting, preparing and detecting an organoclay complex in shale provided in this application has higher accuracy in extracting, preparing and detecting an organoclay complex in shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0045] Figure 1 A flow chart of a method for detecting organoclay complexes in shale provided by one embodiment of the present invention;

[0046] Figure 2 A schematic diagram of a scraping process for an organoclay composite sample provided by one embodiment of the present invention;

[0047] Figure 3 A schematic diagram of the scraping results of an organoclay composite sample provided by one embodiment of the present invention;

[0048] Figure 4 An X-ray diffraction pattern of an organoclay composite sample provided by one embodiment of the present invention;

[0049] Figure 5 A calibrated infrared spectrum data curve of an organoclay composite sample provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a method for extracting, preparing, and detecting organic clay complexes in shale according to the present invention, its specific implementation, structure, features, and effects. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. The specific features, structures, or characteristics of one or more embodiments may be combined in any suitable form. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood to imply or suggest relative importance or implicitly indicate the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of such features.

[0051] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0052] The following describes in detail a method for extracting, preparing and detecting an organoclay complex in shale provided by the present invention with reference to the accompanying drawings.

[0053] This application embodiment provides a method for detecting organoclay complexes in shale. Figure 1 , which shows a flow chart of a method for detecting organoclay complexes in shale provided by one embodiment of the present invention, the method comprising:

[0054] Step S101: crush the shale sample into powder using a grinder and add the powder into a glass beaker; inject deionized water into the glass beaker, soak the shale sample and skim off carbonaceous debris floating on the surface.

[0055] In a specific implementation of an embodiment of the present invention, the shale sample used to extract the organoclay complex is first crushed using a jaw crusher. After the sample is crushed to a particle size of less than 1 mm, 30 grams of powder is weighed and placed in a 500 ml tall glass beaker. It should be noted that when selecting a grinding device, do not use equipment such as a vibration grinder. Excessive mechanical crushing will destroy the structure of the organoclay complex and cause extraction failure. Therefore, this application is based on crushing the sample using a jaw crusher to a particle size of less than 1 mm, which meets the crushing requirements while retaining the structure of the organoclay complex.

[0056] In one specific implementation of the present invention, 200 milliliters of deionized water was poured into a glass beaker. After soaking the shale sample for 24 hours, the carbonaceous debris floating on the surface was skimmed off with cotton wool. Deionized water can control the pH of the solution to near neutrality, preventing ion exchange between metal ions such as calcium and magnesium and clay minerals. It is also relatively pure, thus preventing contamination by impurities to a certain extent. The carbonaceous debris, primarily composed of organic matter such as asphalt, represents an overmature organoclay complex and is not a target for selection. During the soaking process, the carbonaceous debris rises due to buoyancy, and after skimming, it can avoid interfering with the subsequent organoclay complex separation process.

[0057] By crushing the shale samples and removing the carbonaceous debris floating on their surface, the shale samples were initially separated, and the influence of larger impurities on the organic clay complex was preliminarily removed. This is a pretreatment process before the subsequent separation process, which further improves the separation accuracy.

[0058] Step S102: wet-grinding the soaked shale sample, soaking it again and dispersing it with ultrasound to obtain a suspension; stirring the suspension and then letting it stand, extracting the upper liquid of the suspension and pouring it into a polypropylene beaker to obtain a mixture solution.

[0059] In a specific implementation of an embodiment of the present invention, a hybrid ball mill is used to wet-grind the soaked sample in a grinding jar at a vibration frequency of 5 times per second for 10 minutes to obtain a wet-grinded shale sample; the wet-grinded shale sample is poured back into a glass beaker and filled with deionized water to obtain a mixed solution; the mixed solution is shaken by an ultrasonic crusher to obtain a suspension. By long-term low-frequency wet grinding, the sedimentation process is reversely simulated, so that the shale particles can be fully disintegrated while avoiding the damage to the mineral particles and organic clay complex particles during the mechanical grinding process in the existing method. After the wet grinding process, the particles are shaken and suspended, so that the particle size of the extracted particles is controlled to the clay grade based on the principle of the suspension extraction method, thereby improving the accuracy of the separation of the organic clay complex; it is further necessary to extract the required upper suspension from the suspension. In a specific implementation of an embodiment of the present invention, the process of obtaining the mixture solution includes:

[0060] The stirring process, the standing process, the pouring process, and the water addition process are repeated in this order until the mixture solution in the polypropylene beaker reaches the preset sample volume requirement; wherein the stirring process includes stirring the suspension in the glass beaker; the standing process includes standing the suspension for 24 hours; the pouring process includes pouring 200 ml of the upper suspension into a 5000 ml polypropylene beaker; and the water addition process includes adding 200 ml of deionized water to the glass beaker. In other words, the specific process is to first stir the suspension in the glass beaker and then stand it for 24 hours, then gently and slowly pour 200 ml of the upper suspension into the polypropylene beaker, and then add an equal amount of deionized water, i.e., 200 ml, to the glass beaker for dilution and repeat the stirring process, and continue the cycle until the required sample volume is reached in the polypropylene beaker. In a specific implementation of the embodiment of the present invention, the preset sample volume requirement is set to 1 liter of mixture solution, which can be adjusted according to the specific implementation environment. By repeatedly extracting the mixture solution, as much of the required mixture solution containing the organoclay complex components as possible is extracted.

[0061] Step S103: After the mixture solution in the polypropylene beaker is dried at low temperature, powder is scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample.

[0062] The organoclay composite particles have the characteristics of small particle size, low density, and easy adhesion to the surface of the plastic beaker. After the mixture solution is obtained based on the small particle size and low density, it is dried at low temperature based on its easy adhesion to the surface of the plastic beaker to obtain a powder corresponding to the organoclay composite sample attached to the beaker wall. Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the organoclay composite sample includes:

[0063] The polypropylene beaker containing the mixture solution is placed in an oven in a tilted state and dried at a low temperature of 60 degrees Celsius. Then, a plastic tool is used to scrape the powder on the wall of the polypropylene beaker to obtain an organoclay complex sample. It should be noted that a centrifuge cannot be used here to accelerate sedimentation. The reason is that the density of the organoclay complex is relatively low, and a high-speed centrifuge is required. However, the capacity of a high-speed centrifuge is relatively small, resulting in lower efficiency. On the other hand, the organoclay complex with low maturity is lighter in color and can be easily poured away as clean water. Therefore, the low-temperature drying method can avoid the problem of insufficient centrifugal speed in the centrifuge method, which makes it impossible to destroy the colloidal state of the organoclay complex in the solution and prevent effective precipitation. In addition, it should be noted that a considerable part of the powder at the bottom of the cup is clay minerals, which contain low or no organoclay complex content. Therefore, there is no need to collect the powder at the bottom of the cup. Please refer to Figure 2 , which shows a schematic diagram of a process for scraping an organoclay composite sample provided by one embodiment of the present invention, Figure 2 The powder on the wall of the polypropylene beaker has been scraped off, while most of the powder on the bottom of the beaker has been retained. Figure 3 , which shows a schematic diagram of the scraping results of an organoclay complex sample provided by one embodiment of the present invention, that is, the organoclay complex sample that needs to be tested later in this application.

[0064] Step S104: Obtain X-ray diffraction patterns and attenuated total reflection infrared spectrum data of the organoclay composite sample.

[0065] In one specific implementation of an embodiment of the present invention, a 30 mg sample of the organoclay complex was ground in an agate mortar until free of grains. The sample tablet was then pressed using a powder press. The sample tablet was then processed using an X-ray diffractometer to obtain an X-ray diffraction pattern of the organoclay complex sample. A 5 mg sample of the organoclay complex was then selected, and attenuated total reflection infrared spectroscopy data of the organoclay complex sample was collected using an attenuated total reflection infrared spectrometer. Both X-ray diffraction analysis and infrared spectroscopy can simultaneously interpret organic matter and clay minerals. The former focuses on clay minerals and can analyze the type and content of clay minerals, while the latter focuses on the detection of organic functional groups and is more suitable for qualitative analysis of organic matter. Therefore, the X-ray diffraction pattern and attenuated total reflection infrared spectroscopy data of the organoclay complex sample were collected simultaneously for comprehensive analysis.

[0066] This application takes into account that the collection process of attenuated total reflection infrared spectroscopy data is easily disturbed by the external environment, resulting in poor data quality of the collected attenuated total reflection infrared spectroscopy data. Therefore, the attenuated total reflection infrared spectroscopy data is further denoised to make the detection of organic clay complexes more accurate.

[0067] Step S105: Decompose the attenuated total reflection infrared spectrum data through discrete wavelet transform to obtain the wavelet coefficient curve corresponding to each layer; wherein the wavelet coefficient curve includes a high-frequency wavelet coefficient curve and a low-frequency wavelet coefficient curve; determine the baseline shift response value of each layer according to the difference in fluctuation changes of the wavelet coefficient curves corresponding to each layer and other layers.

[0068] Denoising based on wavelet transform is a commonly used signal denoising method. Its basic principle is to decompose the signal and, based on the relatively small wavelet coefficients of the noise, select an appropriate threshold to remove the noise and then reconstruct it to obtain the denoised signal. In one specific implementation of the embodiment of the present invention, the Daubechies wavelet is used as the wavelet basis. The implementer can select other wavelet bases from the wavelet basis function library according to the specific implementation environment. Further details will not be given here.

[0069] Then, considering that the organic clay complex samples show significant characteristic differences in the interference effects in each frequency range during the detection process, after decomposing into the wavelet coefficient curve of each layer, the baseline shift phenomenon caused by interference factors in the infrared spectrum data of the organic clay complex at different scales and frequency ranges is accurately analyzed, and the wavelet threshold of each layer is adaptively corrected, so that the noise removal is more in line with the objective situation of the signal, the noise removal effect is better, and the accuracy of the subsequent denoised and corrected infrared spectrum data is improved.

[0070] Therefore, based on the need for decomposition, the attenuated total reflection infrared spectrum data is decomposed by discrete wavelet transform to obtain the wavelet coefficient curve corresponding to each layer; wherein the wavelet coefficient curve includes a high-frequency wavelet coefficient curve and a low-frequency wavelet coefficient curve; the high-frequency wavelet coefficient curve is the detail coefficient curve, and the low-frequency wavelet coefficient curve is the approximate coefficient curve, both of which are inherent technical terms in discrete wavelet transform decomposition, and discrete wavelet transform decomposition is a technical means well known to those skilled in the art, and will not be further defined or elaborated here.

[0071] The low-frequency wavelet coefficient curve is a smoothed version of the signal curve before decomposition. Compared to the original signal, it removes most high-frequency noise and fine details, resulting in a smoother curve that reflects the overall trend of the signal. If the original hyperspectral signal contains small fluctuations caused by measurement noise, these fluctuations will be attenuated or eliminated in the low-frequency wavelet coefficient curve. For example, sharp peaks in the original signal may be smoothed in the low-frequency wavelet coefficient curve. The low-frequency wavelet coefficients better highlight the overall trend of the signal, such as whether it is a gradual rise or fall or has some broad peaks and valleys. The high-frequency wavelet coefficient curve, on the other hand, contains the high-frequency components of the original signal and reflects its details and variations. In the figure, the high-frequency wavelet coefficient curve may show more positive and negative fluctuations. If the original hyperspectral signal has rapid changes at certain wavelengths, such as sharp changes caused by the absorption or emission characteristics of a substance, these changes will be reflected as larger amplitudes in the high-frequency wavelet coefficient curve. If the original signal contains noise, the noise is mainly concentrated in the high-frequency portion, so the high-frequency wavelet coefficient curve will also show some irregular fluctuations, which are mixed with the actual signal details.

[0072] Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the baseline shift response value includes:

[0073] Obtain the number of extreme points, upper envelope and lower envelope of each wavelet coefficient curve; perform uniform sampling operation on each wavelet coefficient curve based on the number of extreme points to obtain the sampling points of each wavelet coefficient curve; arrange the numerical differences between the upper envelope and the lower envelope corresponding to all sampling points of each wavelet coefficient curve in sequence to form a sequence as the wavelet feature sequence of each wavelet coefficient curve; arrange the mean, variance, standard deviation and range of all curve values ​​of the wavelet feature sequence in sequence to form a vector as the wavelet feature vector; take the cosine similarity between the wavelet feature vector of the high-frequency wavelet coefficient curve and the wavelet feature vector of the low-frequency wavelet coefficient curve corresponding to each layer as the feature similarity corresponding to each layer; normalize the feature similarity of each layer with the mean of the difference values ​​between the feature similarities of other layers to determine the baseline shift response value of each layer.

[0074] Based on the envelope, more accurate baseline information extraction is performed, and the mean is used to characterize the overall amplitude characteristics of the signal. The variance, range, and standard deviation all characterize the overall fluctuation of the signal. After forming the wavelet eigenvector, the similarity of the wavelet eigenvectors between the high-frequency wavelet coefficient curve and the low-frequency wavelet coefficient curve of each layer is used to characterize the similarity of information changes, and vice versa. The information change differences between different layers are then compared and analyzed to quantify the degree of baseline shift after decomposition of different layers, that is, the baseline shift response value. The greater the difference between the feature similarity between the corresponding high frequency and low frequency compared with the feature similarity of other layers, the more likely the wavelet coefficient curve of the layer is affected, resulting in baseline shift. At this time, the baseline is more affected by the shift, that is, the more significant the impact of the baseline shift at the corresponding scale and frequency during the infrared spectrum acquisition of the organic clay complex is. At this time, a smaller threshold should be given to effectively remove the interference of the offset while protecting the effective signal; conversely, if the baseline shift response value is smaller, it means that the impact of the baseline shift at the corresponding scale and frequency during the infrared spectrum acquisition of the organic clay complex is less significant. At this time, the threshold should not be corrected, and conventional denoising should be performed on the basis of retaining the original threshold.

[0075] In a specific implementation of the embodiment of the present invention, the process of obtaining the baseline shift response value is expressed by the formula: Among them, F k is the baseline shift response value of the kth layer; N k is the number of all layers except the kth layer; S k is the cosine similarity between the wavelet eigenvector of the high-frequency wavelet coefficient curve and the wavelet eigenvector of the low-frequency wavelet coefficient curve corresponding to the k-th layer, that is, the feature similarity corresponding to the k-th layer; S k,i It is the cosine similarity between the wavelet eigenvector of the high-frequency wavelet coefficient curve corresponding to the i-th layer outside the k-th layer and the wavelet eigenvector of the low-frequency wavelet coefficient curve, that is, the feature similarity corresponding to the i-th layer outside the k-th layer; Norm() is a linear normalization function.

[0076] Step S106: Using the baseline shift response value as a weight to correct the initial wavelet threshold of each layer, and determine the corresponding corrected wavelet threshold; performing baseline-preserving threshold processing on the wavelet coefficient curve and reconstructing it according to the corrected wavelet threshold to determine the baseline spectrum curve; performing baseline correction on the attenuated total reflection infrared spectrum data according to the baseline spectrum curve to determine the corrected infrared spectrum data; and performing organoclay complex detection based on the X-ray diffraction pattern and the corrected infrared spectrum data.

[0077] Further, based on the influence of the baseline shift response value on the threshold setting, in a specific implementation of the embodiment of the present invention, the process of obtaining the modified wavelet threshold includes:

[0078] The product of the negative correlation mapping value of the baseline shift response value and the preset initial wavelet threshold corresponding to each layer is used as the modified wavelet threshold of each layer. After the baseline shift response value is negatively correlated, the characteristic of the negative correlation relationship between the baseline shift response value and the modified wavelet threshold is met. In a specific implementation of the embodiment of the present invention, the process of obtaining the modified wavelet threshold is expressed by the formula: R ′ k =R k ×(1-F k ); where R ′ k is the modified wavelet threshold of the kth layer; R k is the preset initial wavelet threshold of the kth layer; F k is the baseline shift response value of the kth layer; in a specific implementation of an embodiment of the present invention, the preset initial wavelet threshold selects the VisuShrink threshold commonly used in wavelet denoising in the prior art, that is, the general threshold. The SureShrink threshold, Minimax threshold, BayesShrink threshold, etc. can also be selected according to the specific implementation environment, which will not be further elaborated here.

[0079] After obtaining the threshold, further denoising and reconstruction processing is performed using the threshold. Preferably, the process of obtaining the baseline spectrum curve includes:

[0080] According to the modified wavelet threshold, hard threshold processing is performed on the high-frequency wavelet coefficient curve of each layer to obtain a hard threshold processing curve; according to the modified wavelet threshold, soft threshold processing is performed on the low-frequency wavelet coefficient curve of each layer to obtain a soft threshold processing curve; wavelet reconstruction is performed using a reconstruction algorithm based on all soft threshold processing curves and all hard threshold processing curves corresponding to all layers to obtain a baseline spectrum curve. It should be noted that curve reconstruction, hard threshold processing and soft threshold processing are commonly used technical means in wavelet denoising, and their specific processes will not be further described here. By hard thresholding the high-frequency wavelet coefficient curve, the influence of interference information other than the baseline in the high-frequency information can be removed as much as possible, while the low-frequency wavelet coefficients that retain more baselines are subjected to softer soft threshold processing for baseline correction, avoiding excessive processing and loss of baseline features, so that the baseline spectrum curve after subsequent reconstruction retains the baseline information more completely and excludes interference from other information as much as possible.

[0081] After obtaining the reconstructed baseline spectrum, the baseline spectrum curve is subtracted from the curve corresponding to the attenuated total reflection infrared spectrum data to obtain the corrected infrared spectrum data after baseline correction, so as to perform more accurate organic functional group detection based on the corrected infrared spectrum data;

[0082] Finally, the organoclay complex is tested based on the corrected infrared spectrum data and X-ray diffraction pattern after baseline correction. In the corrected infrared spectrum data curve, the organic component functional group peaks at 2920cm-1 and 2860cm-1 are usually present, as well as the silicate functional group peak at 1100cm-1. Figure 4 , which shows an X-ray diffraction pattern of an organoclay composite sample provided by one embodiment of the present invention. Figure 4 In the , the peak of clay minerals, namely illite, and the peak of organic matter coexist; see Figure 5 , which shows a calibrated infrared spectrum data curve of an organoclay composite sample provided by one embodiment of the present invention, including a CH2 vibration peak corresponding to an organic functional group and a peak corresponding to a silicate functional group near 1100 cm-1.

[0083] In summary, a method for detecting organoclay complexes in shale performs more accurate extraction of organoclay complex particles through three-level control, collects X-ray diffraction patterns and attenuated total reflection infrared spectroscopy data of the organoclay complex, and corrects the attenuated total reflection infrared spectroscopy data of the organoclay complex through a wavelet denoising process. Specifically, the wavelet threshold of each layer is adaptively corrected through the baseline offset response represented by the information change difference between layers, so that the noise processing process has better adaptability and robustness when reconstructing based on the corrected wavelet threshold, making the final corrected infrared spectroscopy data more accurate, thereby combining with the X-ray diffraction pattern for more accurate organoclay complex detection.

[0084] The present application also provides a method for extracting and preparing an organoclay complex from shale, which specifically includes:

[0085] The shale sample was crushed into powder using a grinder and then added to a glass beaker; deionized water was poured into the glass beaker, the shale sample was soaked, and carbonaceous debris floating on the surface was skimmed off;

[0086] After wet grinding the soaked shale sample, soak it again and disperse it with ultrasound to obtain a suspension; after stirring the suspension and letting it stand, extract the upper liquid of the suspension and pour it into a polypropylene beaker to obtain a mixture solution;

[0087] After the mixture solution in the polypropylene beaker was dried at low temperature, powder was scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample.

[0088] It should be noted that the above embodiment provides a method for extracting and preparing an organic clay complex in shale, which is based on the same concept as an embodiment of a method for detecting an organic clay complex in shale. The specific implementation process is detailed in the method embodiment and will not be repeated here.

[0089] It should be noted that the order in which the embodiments of the present invention are described above is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0090] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

Claims

1. A method for detecting organoclay complexes in shale, characterized in that: The detection method comprises: The shale sample was crushed into powder using a grinder and then added to a glass beaker; deionized water was poured into the glass beaker, the shale sample was soaked, and carbonaceous debris floating on the surface was skimmed off; After wet grinding the soaked shale sample, soak it again and disperse it with ultrasound to obtain a suspension; after stirring the suspension and letting it stand, extract the upper liquid of the suspension and pour it into a polypropylene beaker to obtain a mixture solution; After the mixture solution in the polypropylene beaker was dried at low temperature, powder was scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample; Obtaining X-ray diffraction patterns and attenuated total reflection infrared spectroscopy data of the organoclay composite sample; Decomposing the attenuated total reflection infrared spectrum data by discrete wavelet transform to obtain a wavelet coefficient curve corresponding to each layer; wherein the wavelet coefficient curve includes a high-frequency wavelet coefficient curve and a low-frequency wavelet coefficient curve; determining a baseline shift response value for each layer based on the difference in fluctuations between the wavelet coefficient curves corresponding to each layer and those of other layers; The initial wavelet threshold of each layer is corrected using the baseline shift response value as a weight to determine the corresponding corrected wavelet threshold; the wavelet coefficient curve is subjected to baseline retention threshold processing and reconstructed according to the corrected wavelet threshold to determine a baseline spectrum curve; the attenuated total reflection infrared spectrum data is baseline corrected according to the baseline spectrum curve to determine corrected infrared spectrum data; and the organoclay complex is detected based on the X-ray diffraction pattern and the corrected infrared spectrum data.

2. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of crushing the shale sample into powder using a crusher and then adding the powder into a glass beaker comprises: The shale sample was first crushed to less than 1 mm using a jaw crusher, and 30 g of powder was weighed and placed in a 500 ml tall glass beaker.

3. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of injecting deionized water into the glass beaker, soaking the shale sample, and skimming off carbonaceous debris floating on the surface of the shale sample comprises: Pour 200 ml of deionized water into a glass beaker, soak the shale sample for 24 hours, and then use absorbent cotton to skim off the carbonaceous debris floating on the surface.

4. The method for detecting organoclay complexes in shale according to claim 1, wherein: The process of obtaining the suspension includes: The soaked sample was wet-ground in a grinding jar using a hybrid ball mill at a vibration frequency of 5 times per second for 10 minutes to obtain a wet-ground shale sample; the wet-ground shale sample was poured back into a glass beaker and filled with deionized water to obtain a mixed solution; the mixed solution was shaken by an ultrasonic disruptor to obtain a suspension.

5. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the mixture solution includes: Repeat the stirring process, the standing process, the pouring process, and the water adding process in this order until the mixture solution in the polypropylene beaker reaches the preset sample volume requirement; The stirring process includes stirring the suspension in the glass beaker; the standing process includes standing the suspension for 24 hours; the pouring process includes pouring 200 ml of the upper suspension into a 5000 ml polypropylene beaker; and the water adding process includes adding 200 ml of deionized water into the glass beaker.

6. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the organoclay complex sample includes: The polypropylene beaker containing the mixture solution was placed in an oven in a tilted state and dried at a low temperature of 60 degrees Celsius. The powder on the wall of the polypropylene beaker was scraped off with a plastic tool to obtain an organoclay composite sample.

7. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the X-ray diffraction pattern includes: The organoclay composite sample is placed in an agate mortar and ground until there is no granularity, and then a sample tablet is prepared by powder pressing. The sample tablet is processed by an X-ray diffractometer to obtain an X-ray diffraction pattern of the organoclay composite sample.

8. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the baseline shift response value includes: Obtain the number of extreme points, upper envelope, and lower envelope of each wavelet coefficient curve; perform a uniform sampling operation on each wavelet coefficient curve based on the number of extreme points to obtain sampling points of each wavelet coefficient curve; arrange the numerical differences between the upper envelope and the lower envelope corresponding to all sampling points of each wavelet coefficient curve in sequence to form a sequence as the wavelet feature sequence of each wavelet coefficient curve; arrange the mean, variance, standard deviation, and range of all curve values ​​of the wavelet feature sequence in sequence to form a vector as the wavelet feature vector; The cosine similarity between the wavelet feature vector of the high-frequency wavelet coefficient curve and the wavelet feature vector of the low-frequency wavelet coefficient curve corresponding to each layer is used as the feature similarity corresponding to each layer; The baseline shift response value of each layer is determined by normalizing the mean difference between the feature similarity of each layer and the feature similarity of other layers.

9. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the modified wavelet threshold includes: The product of the negative correlation mapping value of the baseline shift response value and the preset initial wavelet threshold corresponding to each layer is used as the modified wavelet threshold of each layer.

10. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The process of obtaining the baseline spectrum curve includes: According to the modified wavelet threshold, hard threshold processing is performed on the high-frequency wavelet coefficient curve of each layer to obtain a hard threshold processing curve; according to the modified wavelet threshold, soft threshold processing is performed on the low-frequency wavelet coefficient curve of each layer to obtain a soft threshold processing curve; wavelet reconstruction is performed using a reconstruction algorithm based on all soft threshold processing curves and all hard threshold processing curves corresponding to all layers to obtain a baseline spectral curve.

11. The method for detecting organoclay complexes in shale according to claim 1, characterized in that: The acquisition process of the corrected infrared spectrum data includes: The baseline spectrum curve is subtracted from the curve corresponding to the attenuated total reflection infrared spectrum data to obtain corrected infrared spectrum data.

12. A method for extracting and preparing an organoclay complex from shale, characterized in that: The preparation method comprises: The shale sample was crushed into powder using a grinder and then added to a glass beaker; deionized water was poured into the glass beaker, the shale sample was soaked, and carbonaceous debris floating on the surface was skimmed off; After wet grinding the soaked shale sample, soak it again and disperse it with ultrasound to obtain a suspension; after stirring the suspension and letting it stand, extract the upper liquid of the suspension and pour it into a polypropylene beaker to obtain a mixture solution; After the mixture solution in the polypropylene beaker was dried at low temperature, powder was scraped from the wall of the polypropylene beaker to obtain an organoclay composite sample.

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