Method, device and equipment for detecting original oil content of core drilled by oil-based drilling fluid

Abstract

The present application relates to the technical field of core spectrum analysis, and particularly relates to a method, device and equipment for detecting original oil content of a core drilled by an oil-based drilling fluid, which first quantifies the wavelength-level oil-based interference degree and determines the fusion weight based on the local waveform similarity of the core and the drilling fluid spectrum, constructs a drilling fluid fusion spectrum sequence reflecting the current core contamination characteristics, and then finely corrects the core spectrum, detects the original oil content of the core according to the obtained corrected spectrum curve and the pre-constructed spectrum peak area-oil component volume percentage content relationship equation; the present application fully considers the non-homogeneity and wavelength interference difference of the drilling fluid, implements accurate denoising by constructing an adaptive background spectrum, effectively avoids the signal over-removal or residual problem caused by the traditional global difference method, makes the corrected spectrum curve after correction more truly restore the original characteristics of the core, and significantly improves the accuracy of detecting the original oil content of the contaminated core.

Description

Technical Field

[0001] This invention relates to the field of core spectral analysis technology, specifically to a method, apparatus, and equipment for detecting the original oil content in core samples obtained from oil-based drilling fluids. Background Technology

[0002] In the process of oil drilling, oil-based mud is usually used as drilling fluid for drilling operations in highly water-sensitive formations, high-temperature and high-pressure deep wells, high-angle wells, horizontal wells and extended reach wells. When core samples are obtained from the well and oil content is evaluated based on the core samples, the oil-based drilling fluid will contaminate the core samples, making it impossible to accurately evaluate the true oil content of the core samples.

[0003] Existing technologies typically acquire the spectral curves of contaminated core samples and drilling fluid samples directly. The difference in spectral intensity between the two is used to subtract drilling fluid components to determine the corrected spectral curve of the contaminated core, which is then used to detect the original oil content of the core. However, due to the complex and heterogeneous composition of oil-based drilling fluids, their interference with the core spectrum varies at different wavelengths, and the degree of contamination also differs at different locations within the core. This makes simple difference correction insufficient to accurately adapt to the interference characteristics of different wavelength bands, easily leading to over-removal of the true oil-bearing signal from the core or incomplete removal of the drilling fluid signal. Consequently, the obtained corrected spectral curve cannot accurately reflect the original oil-bearing spectral characteristics of the core. In other words, the accuracy of the corrected spectral curve of the drilling fluid-contaminated core, calculated by the global difference between the spectral curves of the drilling fluid-contaminated core and the drilling fluid sample, is low, thus affecting the accuracy of detecting the original oil content of the core based on the corrected spectral curve. Summary of the Invention

[0004] To address the low accuracy of corrected spectral curves for drilling fluid-contaminated cores calculated using the global difference between the spectral curves of the core samples and the drilling fluid samples, this application aims to provide a method, apparatus, and equipment for detecting the original oil content in core samples obtained from oil-based drilling fluids. The specific technical solution adopted is as follows:

[0005] The first aspect of this application provides a method for detecting the original oil content in core samples obtained from oil-based drilling fluid, including:

[0006] The laser spectrum curves of the core samples contaminated with drilling fluid and the laser spectrum curves of each drilling fluid sample were collected.

[0007] Based on the similarity of laser intensity changes between the core laser spectrum curve and the drilling fluid laser spectrum curve within the wavelength neighborhood of each wavelength, the oil-based interference degree of each drilling fluid sample at each wavelength is determined; based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths, the corresponding fusion weight is determined.

[0008] The laser spectral curves of all drilling fluids are weighted and fused according to the fusion weight of each drilling fluid sample to determine the fused spectral sequence of drilling fluid; the laser spectral curve of the core is corrected according to the fused spectral sequence of drilling fluid to determine the corrected spectral curve of the core contaminated by the drilling fluid to be tested; the original oil content of the core is detected according to the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0009] Furthermore, the process of obtaining the oil-based interference degree includes:

[0010] Each wavelength is sequentially taken as the target wavelength, and all wavelengths within the preset neighborhood wavelength window of the target wavelength are taken as the neighborhood wavelengths of the target wavelength.

[0011] The laser intensities corresponding to all neighboring wavelengths in the core laser spectral curve are arranged in ascending order of wavelength to determine the core spectral data sequence; the laser intensities corresponding to all neighboring wavelengths in the drilling fluid laser spectral curve are arranged in ascending order of wavelength to determine the drilling fluid spectral data sequence.

[0012] The Pearson correlation coefficient between the core spectral data sequence and the drilling fluid spectral data sequence is input into the ReLU function to output the oil-based interference degree of each drilling fluid sample at the target wavelength.

[0013] Furthermore, the process of obtaining the fusion weights includes:

[0014] The reference interference degree is determined based on the mean of the oil-based interference degree of each drilling fluid sample across all wavelengths; the overall interference degree is determined based on the sum of the reference interference degrees of all drilling fluid samples; and the fusion weight of each drilling fluid sample is determined based on the ratio between the reference interference degree and the overall interference degree.

[0015] Furthermore, the process of obtaining the drilling fluid fusion spectral sequence includes:

[0016] At each wavelength, the fusion reference intensity of each drilling fluid sample is determined by multiplying the laser intensity corresponding to the laser spectrum curve of the drilling fluid sample with the corresponding fusion weight. The fusion laser intensity of each wavelength is determined by summing the fusion reference intensities of all drilling fluid samples at each wavelength. The fusion laser intensities of all wavelengths are arranged in ascending order of wavelength to determine the corresponding drilling fluid fusion spectrum sequence.

[0017] Furthermore, the process of obtaining the corrected spectral curve includes:

[0018] Calculate the oil-based interference degree of the drilling fluid fusion spectral sequence at each wavelength to determine the fusion interference degree at each wavelength; determine the corresponding intensity correction value based on the fusion laser intensity of the drilling fluid fusion spectral sequence at each wavelength and the fusion interference degree.

[0019] At each wavelength, the corrected laser intensity for each wavelength is determined based on the difference between the laser intensity of the core laser spectrum curve and the corresponding intensity correction value. After arranging the corrected laser intensities of all wavelengths in ascending order of wavelength, curve fitting is performed to determine the corrected spectral curve of the core sample contaminated with drilling fluid.

[0020] Furthermore, the process of obtaining the intensity correction value includes:

[0021] At each wavelength, the intensity correction value for each wavelength is determined based on the product between the fused laser intensity of the drilling fluid fused spectral sequence and the corresponding fused interference degree.

[0022] Furthermore, the process of constructing the equation relating peak area to crude oil component volume percentage includes:

[0023] Obtain standard core laser spectral curves of at least two sets of uncontaminated core samples, and calculate the peak area of ​​the standard core laser spectral curves; perform three-dimensional scanning and volume modeling on the uncontaminated core samples, and calculate the volume percentage content of crude oil components in the uncontaminated core samples; perform polynomial fitting based on the peak area of ​​each uncontaminated core sample and the corresponding volume percentage content of crude oil components to determine the equation relating peak area and volume percentage content of crude oil components.

[0024] Furthermore, the process of calculating the peak area of ​​the standard sample spectral curve of the standard core laser spectrum includes:

[0025] The area enclosed by the standard core laser spectrum curve and the baseline is calculated using a multi-trapezoidal area calculation method. The multi-trapezoidal area calculation method is to sum the areas of the trapezoids formed by all adjacent wavelength points.

[0026] Furthermore, the process of performing three-dimensional scanning and volumetric modeling on the uncontaminated core standard includes:

[0027] Using a laser confocal microscope, the uncontaminated core sample is scanned point by point, line by line, surface by surface, and layer by layer within a specific size range above and below the representative observation field and the maximum focal plane to obtain a three-dimensional data volume. Volume modeling and surface modeling are performed on the three-dimensional data volume, and the oil storage units in the uncontaminated core sample are identified using data statistical functions.

[0028] Furthermore, the process of calculating the volume percentage content of crude oil components in the uncontaminated core standard sample includes:

[0029] The volume of crude oil components in the uncontaminated core standard is obtained by summing the volumes of all oil storage units. The volume percentage of crude oil components in the uncontaminated core standard is determined based on the ratio between the volume of crude oil components and the total volume of the representative observation field.

[0030] Furthermore, the polynomial fitting employs a quadratic or cubic polynomial.

[0031] Furthermore, the acquisition parameters of the core laser spectrum curve include: excitation source wavelength of 405nm; scanning band range covering 415nm to 800nm; and scanning step size of 5nm.

[0032] Furthermore, the preparation process of the drilling fluid contaminated core sample includes:

[0033] Core samples were cut into blocks or columns and fixed to glass slides using a non-fluorescent adhesive. The fixed core samples were then ground into flat rock slices with a thickness of 50 μm to 100 μm and the surface was polished.

[0034] Furthermore, the process of detecting the original oil content of the core based on the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage includes:

[0035] Based on the calculation principle of the standard sample peak area of ​​the standard core laser spectral curve, the corrected peak area of ​​the corrected spectral curve is calculated; the corrected peak area is input into the relationship equation between the peak area and the volume percentage of crude oil components, and the final volume percentage of crude oil components in the core contaminated by the drilling fluid is output.

[0036] Furthermore, the formula for calculating the area of ​​the trapezoid formed by the adjacent wavelength points includes:

[0037] ;in, Standard core laser spectrum curve The The wavelength point corresponding to the wavelength is related to the . The area of ​​the trapezoid formed by the wavelength points corresponding to each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The laser intensity corresponding to each wavelength; Standard core laser spectrum curve The The laser intensity corresponding to each wavelength.

[0038] Furthermore, the non-fluorescent adhesive is a non-fluorescent ethyl α-cyanoacrylate instant strong adhesive.

[0039] Furthermore, the specific size range above and below refers to the range from 10 μm above the maximum focal plane to 10 μm below it.

[0040] Furthermore, when the core sample is a rock block sample, its size is greater than or equal to 25mm × 25mm × 5mm.

[0041] Secondly, this application provides a device for detecting the original oil content of core samples obtained from oil-based drilling fluid, the device comprising:

[0042] The data acquisition module is used to acquire the laser spectrum curves of the core samples of drilling fluid contaminated rock cores and the laser spectrum curves of the drilling fluid for each sample.

[0043] The fusion weight determination module is used to determine the oil-based interference degree of each drilling fluid sample at each wavelength based on the similarity of laser intensity changes between the laser spectrum curve of the core and the laser spectrum curve of the drilling fluid at each wavelength; and to determine the corresponding fusion weight based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths.

[0044] The core raw oil content detection module is used to perform weighted fusion of all drilling fluid laser spectrum curves according to the fusion weight of each drilling fluid sample to determine the fused spectral sequence of the drilling fluid; to perform data correction on the core laser spectrum curve according to the fused spectral sequence of the drilling fluid to determine the corrected spectral curve of the core contaminated by the drilling fluid to be tested; and to detect the raw oil content of the core according to the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0045] Thirdly, this application also proposes an equipment for detecting the original oil content of core samples taken from oil-based drilling fluid, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any of the steps of a method for detecting the original oil content of core samples taken from oil-based drilling fluid.

[0046] This application has the following beneficial effects:

[0047] This invention, based on the similarity of laser intensity changes between the laser spectral curves of the core samples contaminated with drilling fluid and the laser spectral curves of each drilling fluid sample, precisely quantifies the oil-based interference degree of each drilling fluid sample at different wavelengths. Based on this, a fusion weight is determined to construct a fused spectral sequence of drilling fluid reflecting the current core contamination characteristics. This sequence is then used to perform wavelength-level fine data correction on the core laser spectral curve, determining the corrected spectral curve of the core contaminated with drilling fluid. This method fully considers the heterogeneity of oil-based drilling fluid components and the differences in interference levels at different wavelengths. Through local waveform similarity analysis, it accurately identifies and matches the current core contamination characteristics, constructing a drilling fluid background spectrum that best reflects the actual contamination situation. Adaptive spectral correction is then implemented, effectively avoiding the excessive signal removal or residue problems caused by traditional global difference methods. This results in a more accurate corrected spectral curve that more realistically restores the original spectral characteristics of the core. Ultimately, this leads to higher accuracy in detecting the original oil content of the core based on the corrected spectral curve and a pre-constructed equation relating peak area to crude oil component volume percentage. Attached Figure Description

[0048] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of a method for detecting the original oil content in core samples obtained from oil-based drilling fluid, provided in one embodiment of the present invention.

[0050] Figure 2 A schematic diagram of the laser spectrum curve of a core sample of a drilling fluid-contaminated core provided in an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the laser spectrum curve of a drilling fluid sample provided in an embodiment of the present invention;

[0052] Figure 4This is a structural diagram of a device for detecting the original oil content in core samples obtained from oil-based drilling fluid, provided in one embodiment of the present invention. Detailed Implementation

[0053] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method, apparatus, and equipment for detecting the original oil content of core samples obtained from oil-based drilling fluid according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment, and specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0054] Unless otherwise defined, 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 pertains.

[0055] The following description, in conjunction with the accompanying drawings, details the specific scheme of the method, apparatus, and equipment for detecting the original oil content in core samples obtained from oil-based drilling fluids provided by this invention.

[0056] This application provides a method for detecting the original oil content in core samples obtained from oil-based drilling fluid. Please refer to [link to relevant documentation]. Figure 1 The diagram illustrates a flowchart of a method for detecting the original oil content in core samples obtained from oil-based drilling fluid, according to an embodiment of the present invention. The method includes:

[0057] Step S101: Collect the laser spectrum curve of the core sample of the drilling fluid contaminated core and the laser spectrum curve of the drilling fluid for each drilling fluid sample.

[0058] Based on the test wells within the test area, oil-based drilling sampling was conducted to obtain core samples from the target oil layer. Since oil-based drilling mud was used as the drilling fluid during production, the obtained core samples were contaminated with the test drilling fluid. Based on the core samples, either block or column samples were cut. For block samples, the dimensions must be greater than or equal to 25mm × 25mm × 5mm; for column samples, the dimensions must be greater than or equal to 25mm × 5mm. The prepared samples must not be soaked in organic solvents before preparation and must use non-fluorescent solvents. - Use ethyl cyanoacrylate instant strong adhesive to bond the polished rock blocks or columns onto a glass slide, and cut them into flat rock slices with a thickness of 1.5mm. Then, depending on the lithology and particle size, coarsely grind, medium grind, fine grind, and fine grind the rock slices to a thickness of 50μm-100μm to ensure a flat and bright surface. If necessary, cryogenic argon ion polishing can be used to polish the surface to a mirror-like shine.

[0059] The prepared thin section of oil-bearing rock was placed on the stage of a laser confocal microscope. The motorized stage of the laser confocal microscope was adjusted to obtain a representative observation time domain and the maximum focal plane. A specific wavelength of 405nm laser was selected as the excitation source. A specific laser intensity was selected, and a 50× short focal length objective lens was selected for observation. The XYλ scanning mode was selected, and the signal intensity of each channel was adjusted to the maximum value below the overexposure tolerance. The scanning step size was set to 5nm. Scanning was performed within the scanning band range of the excitation source to determine the core laser spectrum curve of the core sample contaminated with drilling fluid. Specifically, when using 405nm wavelength laser as the excitation light, the scanning band range was set to 415nm-800nm. Based on the 5nm scanning step size, the core laser spectrum curve corresponded to the laser intensity at 78 wavelengths. The objective magnification and scanning step size can be adjusted according to the specific implementation environment, which will not be elaborated further here. The method for obtaining the laser spectrum curve of the drilling fluid sample is the same as that for obtaining the laser spectrum curve of the core. The drilling fluid sample is obtained by acquiring oil-based drilling fluid at the corresponding core depth layer, and then using a pipette to drop the oil-based drilling fluid into a special glass-bottomed culture dish for laser confocal microscopy. In this embodiment of the invention, the number of drilling fluid samples is set to 20, which can be adjusted as needed. In another specific implementation of this embodiment, a wavelength of 488nm can also be used as the excitation light source, and the scanning band range can be set to 500nm-800nm, which will not be further elaborated here.

[0060] Please see Figure 2 This diagram illustrates a core laser spectrum curve of a core sample contaminated with drilling fluid, provided by an embodiment of the present invention; please refer to [link / reference]. Figure 3 It shows a schematic diagram of the laser spectrum curve of a drilling fluid sample provided in an embodiment of the present invention; in Figure 2 and Figure 3 In the diagram, the horizontal axis represents wavelength in nm, and the vertical axis represents laser intensity in au (arbitrary unit). This is because the fluorescence signal intensity detected by the laser confocal microscope is the relative response value of the photomultiplier tube (PMT) to photon counting. Its value depends on parameters such as the instrument's gain setting and laser power, rather than the absolute physical quantity of optical power. However, under the same test conditions, this relative intensity is proportional to the content of the substance and is sufficient to meet the needs of quantitative analysis.

[0061] Step S102: Based on the similarity of laser intensity changes between the core laser spectrum curve and the drilling fluid laser spectrum curve in the wavelength neighborhood of each wavelength, determine the oil-based interference degree of each drilling fluid sample at each wavelength; determine the corresponding fusion weight based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths.

[0062] Based on the obtained core laser spectrum and drilling fluid laser spectrum, directly subtracting drilling fluid through global difference calculation would ignore the heterogeneity of oil-based drilling fluid components and the differences in interference levels across different wavelength bands, leading to loss of effective signals or residual noise. Therefore, to accurately identify which wavelength bands in the core spectrum are significantly interfered with by the drilling fluid and the degree of interference, it is necessary to delve deeper into the microscopic wavelength scale, analyze the similarity of the core spectrum and drilling fluid spectrum in local waveforms, and use waveform similarity to characterize the degree of oil-based interference. This provides a quantitative basis for subsequently constructing an adaptive fused background spectrum and implementing wavelength-level fine-tuning, ensuring the accuracy of interference identification.

[0063] Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the oil-based interference degree includes:

[0064] Each wavelength is sequentially used as the target wavelength, and all wavelengths within a preset neighborhood wavelength window of the target wavelength are used as the neighborhood wavelengths of the target wavelength. The laser intensities corresponding to all neighborhood wavelengths in the core laser spectrum curve are arranged in ascending order of their corresponding wavelengths to determine the core spectral data sequence. The laser intensities corresponding to all neighborhood wavelengths in the drilling fluid laser spectrum curve are arranged in ascending order of their corresponding wavelengths to determine the drilling fluid spectral data sequence. The Pearson correlation coefficient between the core spectral data sequence and the drilling fluid spectral data sequence is input into the ReLU function to output the oil-based interference degree of each drilling fluid sample at the target wavelength.

[0065] In one specific implementation of this invention, the preset neighborhood wavelength window is set as a wavelength window corresponding to 9 wavelengths centered on the target wavelength. The length of the preset neighborhood wavelength window can be adjusted according to the specific implementation environment. When the target wavelength is located at the boundary position such that there are less than 4 wavelengths on the left or right, the window formed by the target wavelength and its 8 nearest wavelengths is used as the preset neighborhood wavelength window. This will not be elaborated further here. For the target wavelength, if the fluctuations of all neighboring wavelengths within the corresponding preset neighborhood wavelength window in the core laser spectrum curve are more similar to those in the drilling fluid laser spectrum curve, it indicates that the laser intensity of the target wavelength in the core laser spectrum curve of the core contaminated by the drilling fluid is more likely to be caused by interference from oil-based drilling fluid. Therefore, according to the principle of Pearson correlation coefficient, the greater the oil-based interference, the more consistent the spectral characteristics of the core at the current wavelength are with the spectral characteristics of the drilling fluid. The deeper the contamination of this location by the drilling fluid, the lower the reliability of its signal. Therefore, this interference can be accurately used as a quantitative indicator to guide the calculation of fusion weights and the attenuation correction of the core spectral data in subsequent steps, thereby achieving precise suppression of strong interference bands. It should be noted that the Pearson correlation coefficient is input into the ReLU function here because a negative Pearson correlation coefficient means that the fluctuation trends of the core spectrum and the drilling fluid spectrum are opposite in a local band. This physically indicates that the band is not affected by the in-phase superposition interference of the drilling fluid, and should be regarded as having no interference (i.e., the interference degree is 0). If no truncation is performed, the negative value will cancel out the positive interference values ​​of other bands or samples, resulting in an underestimation of the overall interference, or even causing errors in subsequent weight calculations. Therefore, the ReLU function is used to map it to the non-negative interval to ensure the consistency between the physical meaning and the mathematical calculation.

[0066] After determining the interference level of each drilling fluid sample at various wavelengths, considering the complex and heterogeneous composition of the drilling fluid that comes into contact with the core during actual drilling, the spectral characteristics of a single drilling fluid sample may not fully match the actual contamination status of the current core being tested. Therefore, in order to construct a background spectrum that can best reproduce the contamination characteristics of the current core, it is necessary to select the sample combination most similar to the current core contamination characteristics from all collected drilling fluid samples, and assign fusion weights based on their overall matching degree with the core spectrum. This weighted fusion generates an adaptive drilling fluid fusion spectral sequence, providing an accurate background reference for subsequent high-precision spectral correction and effectively overcoming correction errors caused by the heterogeneity of drilling fluid components. Therefore, this embodiment of the invention further determines the corresponding fusion weight based on the overall relative magnitude of the oil-based interference level of each drilling fluid sample at all wavelengths.

[0067] Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the fusion weight includes: determining the corresponding reference interference degree based on the average oil-based interference degree of each drilling fluid sample at all wavelengths; determining the overall interference degree based on the cumulative value of the reference interference degrees of all drilling fluid samples; and determining the fusion weight of each drilling fluid sample based on the ratio between the reference interference degree and the overall interference degree.

[0068] The process of obtaining the fusion weights is essentially a linear normalization of the reference interference. The sum of the fusion weights for all drilling fluid samples is 1. This aims to transform the overall similarity between each drilling fluid sample and the core spectrum into a probability distribution of weight values. This ensures that samples with a high degree of matching with the core contamination characteristics occupy a larger proportion during fusion, thereby ensuring that the generated fused spectral sequence accurately reflects the main contamination component characteristics of the current core and improving the fitting accuracy of the background spectrum. To prevent calculation failure due to a zero denominator, this embodiment adds a very small positive number as a parameter adjustment factor to the overall interference when performing ratio calculations. In this embodiment, the value of this very small positive number is set to 0.001 to ensure the numerical stability of the calculation process.

[0069] Step S103: Weighted fusion of all drilling fluid laser spectral curves is performed according to the fusion weight of each drilling fluid sample to determine the fused spectral sequence of drilling fluid; data correction is performed on the core laser spectral curve according to the fused spectral sequence of drilling fluid to determine the corrected spectral curve of the core contaminated by the drilling fluid to be tested; the original oil content of the core is detected according to the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0070] After obtaining the fusion weights that reflect the degree of matching between each drilling fluid sample and the current core contamination characteristics, and considering that these fusion weights characterize the contribution of the spectral characteristics of each drilling fluid sample to the actual contamination signal of the current core, targeted weighted superposition can be performed based on the fusion weights to synthesize equivalent background spectral information reflecting the current heterogeneous contamination state. Therefore, the laser spectral curves of all drilling fluids are further weighted and fused according to the fusion weights of each drilling fluid sample to determine the drilling fluid fusion spectral sequence. This drilling fluid fusion spectral sequence can simulate the mixed contamination signal of the core to the greatest extent in terms of waveform characteristics, thereby providing a high-confidence reference benchmark for subsequent fine correction based on wavelength-level differences, ensuring that drilling fluid components can be accurately separated from the contaminated core spectrum.

[0071] Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the drilling fluid fusion spectral sequence includes: at each wavelength, multiplying the laser intensity corresponding to the drilling fluid laser spectrum curve of each drilling fluid sample with the corresponding fusion weight to determine the fusion reference intensity of each drilling fluid sample at each wavelength; determining the fusion laser intensity of each wavelength based on the cumulative value of the fusion reference intensities of all drilling fluid samples at each wavelength; and arranging the fusion laser intensities of all wavelengths in ascending order of wavelength to determine the corresponding drilling fluid fusion spectral sequence.

[0072] Since the sum of the fusion weights of all drilling fluid samples is 1, the fusion laser intensity of each wavelength is determined by summing the products of the laser intensity of all drilling fluid samples at the same wavelength and their respective fusion weights. This fusion laser intensity represents the equivalent background interference intensity at the current wavelength after comprehensively considering the influence of the heterogeneous components of the drilling fluid. After further arranging the fusion laser intensities of all wavelengths, a drilling fluid fusion spectral sequence that comprehensively represents the spectral characteristics of the overall drilling fluid contamination of the current core can be obtained. Compared with the spectrum of a single drilling fluid sample, this sequence has higher robustness and fidelity to the actual contamination situation, laying an accurate data foundation for subsequent high-precision spectral correction.

[0073] Since the drilling fluid fusion spectral sequence characterizes the comprehensive background interference pattern and intensity distribution of the current core at various wavelength positions, and its waveform characteristics are highly consistent with the noise components in the core spectrum, the core laser spectral curve can be further corrected by the drilling fluid fusion spectral sequence. This allows the corrected spectral curve to accurately eliminate false spectral signals caused by oil-based drilling fluids, while fully preserving the oil-bearing characteristic signals of the core itself. This effectively solves the problem of oil content detection deviation caused by inaccurate background subtraction in traditional methods, and significantly improves the accuracy and reliability of the original oil content detection of the core.

[0074] Preferably, in some possible implementations of the embodiments of the present invention, the process of obtaining the calibration spectral curve includes:

[0075] The oil-based interference degree of the drilling fluid fusion spectral sequence at each wavelength is calculated to determine the fusion interference degree at each wavelength. Based on the fusion laser intensity of the drilling fluid fusion spectral sequence at each wavelength and the fusion interference degree, a corresponding intensity correction value is determined. Specifically, at each wavelength, the intensity correction value is determined by multiplying the fusion laser intensity of the drilling fluid fusion spectral sequence by the corresponding fusion interference degree. The calculation principle for the oil-based interference degree of the drilling fluid fusion spectral sequence at each wavelength is the same as that for the drilling fluid laser spectral curve of each drilling fluid sample at each wavelength, and will not be elaborated further here.

[0076] The reason for introducing fusion interference here is to further quantify the waveform similarity between the drilling fluid fusion spectral sequence and the core spectrum. Since the spectral signal of the drilling fluid typically appears as background noise superimposed on the oil-bearing signal of the core, and the drilling fluid fusion spectral sequence has already reflected the current contaminated component characteristics of the core (i.e., the baseline intensity of the background noise) through weighted fusion, while fusion interference reflects the probability of contamination at that wavelength (i.e., the confidence level of noise presence), multiplying the fusion laser intensity by the fusion interference yields the effective background noise intensity to be subtracted at that wavelength (i.e., the intensity correction value). Furthermore, at each wavelength, the corrected laser intensity is determined based on the difference between the laser intensity of the core laser spectrum curve and the corresponding intensity correction value. Due to actual measurement errors, the difference calculation may produce negative values, which is physically unreasonable. Therefore, if the corrected laser intensity is less than a preset non-negative threshold, the corrected laser intensity is forcibly adjusted to the preset non-negative threshold to ensure the non-negativity of the spectral intensity. In this embodiment, the preset non-negative threshold is set to 0, which can be adjusted according to the specific implementation environment. After arranging the intensity of all corrected laser wavelengths in ascending order of wavelength, curve fitting is performed to determine the corrected spectral curve of the drilling fluid contaminated core sample. In a specific implementation of this invention, the curve fitting method adopts the least squares method, which can be adjusted according to the specific implementation environment.

[0077] The calibrated spectral curve characterizes the true spectral response of the oil-bearing components in the core under uncontaminated conditions. Its spectral intensity has an essential physical correspondence with the original crude oil content in the core, eliminating the masking and confusion caused by external contaminants. Therefore, the original oil content of the core is finally detected based on the calibrated spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0078] Preferably, in some possible implementations of the embodiments of the present invention, the process of constructing the equation relating peak area to crude oil component volume percentage includes:

[0079] Obtain at least two sets of standard core laser spectral curves of uncontaminated core samples, and calculate the peak area of ​​the standard core laser spectral curves. Specifically, use a multi-trapezoidal area calculation method to calculate the area of ​​the region enclosed by the standard core laser spectral curve and the baseline. The multi-trapezoidal area calculation method is to accumulate the trapezoidal areas formed by all adjacent wavelength points. In a specific implementation of this invention, the formula for calculating the trapezoidal area formed by adjacent wavelength points includes:

[0080] ;in, Standard core laser spectrum curve The The wavelength point corresponding to the wavelength is related to the . The area of ​​the trapezoid formed by the wavelength points corresponding to each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The laser intensity corresponding to each wavelength; Standard core laser spectrum curve The The formula corresponds to the laser intensity of each wavelength. This formula is a standard trapezoidal rule, so its meaning will not be elaborated further here.

[0081] Furthermore, a polynomial fitting is performed on the peak area of ​​each uncontaminated core sample and the corresponding volume percentage of crude oil components to determine the equation relating peak area and volume percentage of crude oil components. In one specific implementation of this invention, a quadratic or cubic polynomial fitting is used.

[0082] Preferably, in some possible implementations of the present invention, the process of obtaining the volume percentage of crude oil components includes: calculating the volume percentage of crude oil components in the uncontaminated core sample by performing three-dimensional scanning and volume modeling on the uncontaminated core sample; specifically: using a laser confocal microscope, scanning the uncontaminated core sample point by point, line by line, surface by surface, and layer by layer within a specific size range above and below the representative observation field and the maximum focal plane to obtain a three-dimensional data volume, wherein the specific size range above and below the maximum focal plane is 10 μm above and 10 μm below the maximum focal plane; performing volume modeling and surface modeling on the three-dimensional data volume, and using data statistical functions to identify oil storage units in the uncontaminated core sample; then calculating the sum of the volumes of all oil storage units to obtain the volume of crude oil components in the uncontaminated core sample; and determining the volume percentage of crude oil components in the uncontaminated core sample based on the ratio between the volume of crude oil components and the total volume of the representative observation field.

[0083] The peak area can characterize the overall fluorescence response intensity of a substance under excitation light, and its value is directly proportional to the total amount of oil-bearing substances excited. Therefore, there is a clear quantitative coupling relationship between the peak area and the volume percentage of crude oil components, which characterizes the volume of crude oil in the core pores. By constructing the equation of relationship between peak area and volume percentage of crude oil components using the standard core laser spectrum curve of uncontaminated core samples, it is possible to ensure that this quantitative relationship is based on a pure core benchmark, suppress background noise interference as much as possible, and make the equation have extremely high prediction accuracy and universality. Finally, by substituting the spectral area of ​​contaminated cores after high-precision correction into the equation, the accurate and reliable original oil saturation can be output, thereby improving the accuracy of original oil content detection in cores.

[0084] In summary, a method for detecting the original oil content in core samples from oil-based drilling fluids is based on the similarity of laser intensity changes between the laser spectral curves of the core sample contaminated with the drilling fluid and the laser spectral curves of each drilling fluid sample. This method accurately quantifies the oil-based interference degree of each drilling fluid sample at different wavelengths and determines the fusion weights accordingly to construct a fused spectral sequence of drilling fluids reflecting the current core contamination characteristics. This sequence is then used to perform wavelength-level fine data correction on the core laser spectral curves to determine the corrected spectral curve of the core sample contaminated with the drilling fluid. This method fully considers the heterogeneity of oil-based drilling fluid components. By analyzing the differences in the quality and interference levels at different wavelengths, local waveform similarity analysis is used to accurately identify and match the current core contamination characteristics, constructing a drilling fluid background spectrum that best reflects the actual contamination situation, and implementing adaptive spectral correction. This effectively avoids the problem of excessive signal removal or residue caused by the traditional global difference method, resulting in a more accurate corrected spectral curve that can more realistically restore the original spectral characteristics of the core. Ultimately, this leads to higher accuracy in detecting the original oil content of the core based on the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0085] This application also provides a device for detecting the original oil content in core samples obtained from oil-based drilling fluids. Please refer to [link / reference needed]. Figure 4 The diagram shows a structural diagram of an oil-based drilling fluid core core original oil content detection device according to an embodiment of the present invention. The device includes: a data acquisition module 401, a fusion weight determination module 402, and a core original oil content detection module 403.

[0086] The data acquisition module 401 is used to acquire the laser spectrum curve of the core of the drilling fluid contaminated core and the laser spectrum curve of the drilling fluid for each drilling fluid sample.

[0087] The fusion weight determination module 402 is used to determine the oil-based interference degree of each drilling fluid sample at each wavelength based on the similarity of laser intensity changes between the core laser spectrum curve and the drilling fluid laser spectrum curve at each wavelength neighborhood; and to determine the corresponding fusion weight based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths.

[0088] The core original oil content detection module 403 is used to perform weighted fusion of all drilling fluid laser spectrum curves according to the fusion weight of each drilling fluid sample to determine the drilling fluid fusion spectrum sequence; to perform data correction on the core laser spectrum curve according to the drilling fluid fusion spectrum sequence to determine the corrected spectrum curve of the core contaminated by the drilling fluid to be tested; and to detect the original oil content of the core according to the corrected spectrum curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

[0089] It should be noted that the apparatus provided in the above embodiments is only an example of the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the computer equipment can be divided into different functional modules to complete all or part of the functions described above. In addition, the oil-based drilling fluid core sample original oil content detection device and the oil-based drilling fluid core sample original oil content detection method embodiment provided in the above embodiments belong to the same concept, and their specific implementation process is detailed in the method embodiment, and will not be repeated here.

[0090] This application also proposes a device for detecting the original oil content of core samples obtained from oil-based drilling fluid, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements any of the steps of a method for detecting the original oil content of core samples obtained from oil-based drilling fluid.

[0091] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0092] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for detecting the original oil content in core samples obtained from oil-based drilling fluid, characterized in that, The method includes: The laser spectrum curves of the core samples contaminated with drilling fluid and the laser spectrum curves of each drilling fluid sample were collected. Based on the similarity of laser intensity changes between the core laser spectrum curve and the drilling fluid laser spectrum curve within the wavelength neighborhood of each wavelength, the oil-based interference degree of each drilling fluid sample at each wavelength is determined; based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths, the corresponding fusion weight is determined. The laser spectral curves of all drilling fluids are weighted and fused according to the fusion weight of each drilling fluid sample to determine the fused spectral sequence of the drilling fluid; the laser spectral curve of the core is corrected according to the fused spectral sequence of the drilling fluid to determine the corrected spectral curve of the core contaminated with drilling fluid; the original oil content of the core is detected according to the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage. The process of obtaining the oil-based interference degree includes: Each wavelength is sequentially taken as the target wavelength, and all wavelengths within the preset neighborhood wavelength window of the target wavelength are taken as the neighborhood wavelengths of the target wavelength. The laser intensities corresponding to all neighboring wavelengths in the core laser spectral curve are arranged in ascending order of wavelength to determine the core spectral data sequence; the laser intensities corresponding to all neighboring wavelengths in the drilling fluid laser spectral curve are arranged in ascending order of wavelength to determine the drilling fluid spectral data sequence. The Pearson correlation coefficient between the core spectral data sequence and the drilling fluid spectral data sequence is input into the ReLU function to output the oil-based interference degree of each drilling fluid sample at the target wavelength.

2. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 1, characterized in that, The process of obtaining the fusion weights includes: The reference interference degree is determined based on the mean of the oil-based interference degree of each drilling fluid sample across all wavelengths; the overall interference degree is determined based on the sum of the reference interference degrees of all drilling fluid samples; and the fusion weight of each drilling fluid sample is determined based on the ratio between the reference interference degree and the overall interference degree.

3. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 1, characterized in that, The process of obtaining the drilling fluid fusion spectral sequence includes: At each wavelength, the fusion reference intensity of each drilling fluid sample is determined by multiplying the laser intensity corresponding to the laser spectrum curve of the drilling fluid sample with the corresponding fusion weight. The fusion laser intensity of each wavelength is determined by summing the fusion reference intensities of all drilling fluid samples at each wavelength. The fusion laser intensities of all wavelengths are arranged in ascending order of wavelength to determine the corresponding drilling fluid fusion spectrum sequence.

4. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 3, characterized in that, The process of obtaining the corrected spectral curve includes: Calculate the oil-based interference degree of the drilling fluid fusion spectral sequence at each wavelength to determine the fusion interference degree at each wavelength; determine the corresponding intensity correction value based on the fusion laser intensity of the drilling fluid fusion spectral sequence at each wavelength and the fusion interference degree. At each wavelength, the corrected laser intensity for each wavelength is determined based on the difference between the laser intensity of the core laser spectrum curve and the corresponding intensity correction value. After arranging the corrected laser intensities of all wavelengths in ascending order of wavelength, curve fitting is performed to determine the corrected spectral curve of the core sample contaminated with drilling fluid.

5. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 4, characterized in that, The process of obtaining the intensity correction value includes: At each wavelength, the intensity correction value for each wavelength is determined based on the product between the fused laser intensity of the drilling fluid fused spectral sequence and the corresponding fused interference degree.

6. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 1, characterized in that, The process of constructing the equation relating peak area to crude oil component volume percentage includes: Obtain standard core laser spectral curves of at least two sets of uncontaminated core samples, and calculate the peak area of ​​the standard core laser spectral curves; perform three-dimensional scanning and volume modeling on the uncontaminated core samples, and calculate the volume percentage content of crude oil components in the uncontaminated core samples; perform polynomial fitting based on the peak area of ​​each uncontaminated core sample and the corresponding volume percentage content of crude oil components to determine the equation relating peak area and volume percentage content of crude oil components.

7. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 6, characterized in that, The process of calculating the peak area of ​​the standard core laser spectrum curve includes: The area enclosed by the standard core laser spectrum curve and the baseline is calculated using a multi-trapezoidal area calculation method. The multi-trapezoidal area calculation method is to sum the areas of the trapezoids formed by all adjacent wavelength points.

8. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 6, characterized in that, The process of performing three-dimensional scanning and volumetric modeling on the uncontaminated core standard includes: Using a laser confocal microscope, the uncontaminated core sample is scanned point by point, line by line, surface by surface, and layer by layer within a specific size range above and below the representative observation field and the maximum focal plane to obtain a three-dimensional data volume. Volume modeling and surface modeling are performed on the three-dimensional data volume, and the oil storage units in the uncontaminated core sample are identified using data statistical functions.

9. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 8, characterized in that, The process of calculating the volume percentage of crude oil components in the uncontaminated core standard includes: The volume of crude oil components in the uncontaminated core standard is obtained by summing the volumes of all oil storage units. The volume percentage of crude oil components in the uncontaminated core standard is determined based on the ratio between the volume of crude oil components and the total volume of the representative observation field.

10. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 6, characterized in that, The polynomial fitting uses a quadratic or cubic polynomial.

11. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 1, characterized in that, The acquisition parameters of the core laser spectrum curve include: excitation source wavelength of 405nm; scanning band range covering 415nm to 800nm; and scanning step size of 5nm.

12. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 1, characterized in that, The preparation process of the core sample contaminated with the drilling fluid to be tested includes: Core samples were cut into blocks or columns and fixed to glass slides using a non-fluorescent adhesive. The fixed core samples were then ground into flat rock slices with a thickness of 50 μm to 100 μm and the surface was polished.

13. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 6, characterized in that, The process of detecting the original oil content of the core based on the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage includes: Based on the calculation principle of the standard sample peak area of ​​the standard core laser spectral curve, the corrected peak area of ​​the corrected spectral curve is calculated; the corrected peak area is input into the relationship equation between the peak area and the volume percentage of crude oil components, and the final volume percentage of crude oil components in the core contaminated by the drilling fluid is output.

14. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 7, characterized in that, The formula for calculating the area of ​​the trapezoid formed by adjacent wavelength points includes: ;in, Standard core laser spectrum curve The The wavelength point corresponding to the wavelength is related to the . The area of ​​the trapezoid formed by the wavelength points corresponding to each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The numerical value of each wavelength; Standard core laser spectrum curve The The laser intensity corresponding to each wavelength; Standard core laser spectrum curve The The laser intensity corresponding to each wavelength.

15. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 12, characterized in that, The non-fluorescent adhesive is a non-fluorescent ethyl α-cyanoacrylate instant strong adhesive.

16. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 8, characterized in that, The specific size range is from 10 μm above the maximum focal plane to 10 μm below it.

17. The method for detecting the original oil content in core samples obtained from oil-based drilling fluid according to claim 12, characterized in that, When the core sample is a rock block sample, its size is greater than or equal to 25mm × 25mm × 5mm.

18. A device for detecting the original oil content of core samples obtained from oil-based drilling fluid, characterized in that, The apparatus is used to implement the method for detecting the original oil content in core samples obtained from oil-based drilling fluid as described in any one of claims 1 to 17; the apparatus comprises: The data acquisition module is used to acquire the laser spectrum curves of the core samples of drilling fluid contaminated rock cores and the laser spectrum curves of the drilling fluid for each sample. The fusion weight determination module is used to determine the oil-based interference degree of each drilling fluid sample at each wavelength based on the similarity of laser intensity changes between the laser spectrum curve of the core and the laser spectrum curve of the drilling fluid at each wavelength; and to determine the corresponding fusion weight based on the overall relative magnitude of the oil-based interference degree of each drilling fluid sample at all wavelengths. The core raw oil content detection module is used to perform weighted fusion of all drilling fluid laser spectrum curves according to the fusion weight of each drilling fluid sample to determine the fused spectral sequence of the drilling fluid; to perform data correction on the core laser spectrum curve according to the fused spectral sequence of the drilling fluid to determine the corrected spectral curve of the core contaminated by the drilling fluid to be tested; and to detect the raw oil content of the core according to the corrected spectral curve and the pre-constructed equation relating peak area to crude oil component volume percentage.

19. A device for detecting the original oil content of core samples obtained from oil-based drilling fluid, the device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting the original oil content of core samples obtained from oil-based drilling fluid as described in any one of claims 1 to 17.

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