A method for calculating carbon-oxygen ratio based on regularized non-negative least square method

Abstract

The application discloses a kind of based on regularized non-negative least square method's production method carbon-oxygen ratio calculation method.There is following step: S1, obtains stratum common element and carbon-oxygen ratio logging instrument's inelastic gamma standard spectrum;S2, by carbon-oxygen ratio logging instrument to the stratum of place is measured, and the inelastic gamma mixed energy spectrum obtained by measurement is analyzed;S3, establish by each standard energy interval's inelastic gamma standard spectrum and inelastic gamma mixed spectrum count constitutes the contradictory linear equation group;S4, obtains the production of stratum carbon, oxygen element;S5, using the production of stratum carbon, oxygen element obtained in step S4 does ratio, obtains the production method carbon-oxygen ratio not by energy spectrum count statistics influence.The beneficial effect of the application is: improve the accuracy of production method carbon-oxygen ratio and the sensitivity of carbon-oxygen ratio to oil layer identification.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a production-based carbon-oxygen ratio calculation method based on regularized non-negative least squares. Background Technology

[0002] Carbon-oxygen ratio logging is a method that uses non-elastic gamma information generated by a pulsed neutron source to monitor changes in the carbon and oxygen atomic weight ratios in formations, playing a crucial role in oil-water identification and oil saturation calculation. Currently, carbon-oxygen ratio logging mainly obtains formation carbon-oxygen ratio values ​​through the energy window method and the production method. The energy window method calculates the formation carbon-oxygen ratio by counting non-elastic gamma spectra within the selected characteristic gamma energy ranges for carbon and oxygen elements, offering simple operation but relatively low sensitivity for oil-water identification. The production method, on the other hand, calculates the formation carbon-oxygen ratio by analyzing the carbon and oxygen element production using non-elastic gamma spectra, offering high sensitivity for oil-water identification but being significantly affected by the statistical nature of energy spectrum counting.

[0003] As oilfield exploration and development deepens, the sensitivity of the energy window method for calculating the carbon-oxygen ratio (C-O-R) is increasingly insufficient to meet field requirements, while the yield-based C-O-R method is rarely used due to its generally poor energy spectrum statistics. To address these issues, this invention proposes a yield-based C-O-R calculation method based on regularized non-negative least squares. This method utilizes regularization to avoid overfitting during the energy spectrum analysis process, reduces the impact of energy spectrum counting statistics on the yield-based C-O-R value, and improves the accuracy of the yield-based C-O-R method. Summary of the Invention

[0004] The purpose of this invention is to provide a production-based carbon-oxygen ratio calculation method based on regularized non-negative least squares. This method uses numerical simulation to establish non-elastic gamma standard spectra of common formation elements and carbon-oxygen ratio logging instruments, and then uses regularized non-negative least squares to solve for the carbon-oxygen ratio, thereby improving the accuracy of the production-based carbon-oxygen ratio and the sensitivity of the carbon-oxygen ratio for oil layer identification, making it more suitable for oil-bearing identification in buried hill wells.

[0005] To achieve the above objectives, the present invention adopts the following technical solution, including: S1. Run the carbon-oxygen ratio logging instrument into the formation, establish an instrument-casing well formation model based on the instrument parameters and formation parameters, and obtain the common elements in the formation and the non-elastic gamma standard spectrum of the carbon-oxygen ratio logging instrument through numerical simulation; analyze each non-elastic gamma standard spectrum and select the standard energy range. S2. The formation is measured using a carbon-oxygen ratio logging instrument, and the obtained non-elastic gamma mixed energy spectrum is analyzed to obtain the common elements in the formation and the counts of the carbon-oxygen ratio logging instrument in the standard energy range of the non-elastic gamma mixed energy spectrum. S3. The non-elastic gamma standard spectrum and the non-elastic gamma mixed spectrum have a linear relationship in their counts within the standard energy range. A contradictory linear equation system is established, consisting of the counts of the non-elastic gamma standard spectrum and the non-elastic gamma mixed spectrum in each standard energy range. S4. Solve the contradictory equations using the regularized nonnegative least squares method to obtain the production of carbon and oxygen elements in the formation; S5. Using the yield of formation carbon and oxygen elements obtained in step S4 as a ratio, the yield-based carbon-oxygen ratio, which is not affected by energy spectrum counting statistics, is obtained.

[0006] Preferably, in step S1, the instrument parameters include material, source distance, instrument operating sequence, and instrument size; the formation parameters include wellbore size, wellbore fluid, casing material, casing thickness, cement sheath material, cement sheath thickness, formation material, formation porosity, and formation pore fluid; the common elements in the formation are silicon, calcium, magnesium, carbon, and oxygen.

[0007] Preferably, in step S1, the standard energy range refers to the energy range of ±0.25 MeV centered on the characteristic peaks of each element.

[0008] Preferably, in step S3, the contradictory linear equation system is: (1) Where n is the number of elements in the standard spectrum, the (n+1)th element refers specifically to the instrument, a is the number of energy ranges selected in step S2, and b i It is the count of the mixed inelastic gamma spectrum in the i-th energy range, m i,j c represents the counting distribution probability of the characteristic inelastic gamma standard spectrum of the j-th element in the i-th energy interval. j This represents the count contribution of the j-th element to the mixed energy spectrum, also known as yield.

[0009] Preferably, in step S4, the regularization factor λ is selected to be in the range of 0-0.01; the spectral result of the regularized nonnegative least squares method is as follows: (2) Where C is the output matrix, M is the standard spectrum matrix, λI is the regularization term, λ is the regularization factor, I is the unit diagonal matrix, and N is the mixed spectrum matrix.

[0010] The beneficial effects of this invention are: by using numerical simulation methods to establish non-elastic gamma standard spectra of common formation elements and carbon-oxygen ratio logging instruments, the carbon-oxygen ratio can be solved using regularized non-negative least squares method, thereby improving the accuracy of the production method carbon-oxygen ratio and the sensitivity of the carbon-oxygen ratio for oil layer identification, so that it can be better applied to the identification of oil-bearing properties in buried hill wells. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the instrument-casing well formation model in this invention; Figure 2 This is the non-elastic gamma standard spectrum in the embodiments of the present invention; Figure 3 This is the non-elastic gamma mixture spectrum in an embodiment of the present invention; Figure 4 This is a schematic diagram of the energy spectrum quality in an embodiment of the present invention; Figure 5 This is a schematic diagram of the spectral resolution effect when the regularization factor is 0 in an embodiment of the present invention; Figure 6 This is a schematic diagram of the spectral resolution effect when the regularization factor is 0.0005 in an embodiment of the present invention; Figure 7 This is a schematic diagram of the spectral interpretation effect when the regularization factor is 0.01 in an embodiment of the present invention. Detailed Implementation

[0012] The invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0013] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0014] Example like Figure 1-7 As shown, the present invention provides a method for calculating the carbon-oxygen ratio based on the regularized nonnegative least squares method using the output method, comprising: To achieve the above objectives, the present invention adopts the following technical solution, including: S1. Lower the carbon-oxygen ratio logging instrument into the formation, such as... Figure 1 A casing-instrument formation model was established based on instrument parameters and formation parameters. The non-elastic gamma standard spectra of common elements and carbon-oxygen ratio in the formation were obtained using numerical simulation methods. Figure 2The instrument parameters include material, source distance, instrument operating sequence, and instrument dimensions. For example, the instrument shell is made of stainless steel, the shield is made of tungsten-nickel-iron alloy, the source distance is 30cm, the length is 110cm, and the radius is 2.15cm. The formation parameters include wellbore size, wellbore fluid, casing material, casing thickness, cement sheath material, cement sheath thickness, formation material, formation porosity, and formation pore fluid. For example, the wellbore radius is 10.8cm, the wellbore fluid is fresh water, the casing thickness is 0.1cm, the cement sheath thickness is 3cm, the formation is sandstone, the porosity is 0-20%, and the pore fluid is oil. Common formation elements are silicon, calcium, magnesium, carbon, and oxygen. Analysis of various non-elastic gamma standard spectra is performed to select standard energy ranges. The standard energy range refers to the energy range of ±0.25MeV centered on the characteristic peaks of each element. Figure 3 ; S2. Measurements are taken of the formation using a carbon-oxygen ratio logging instrument, and the obtained inelastic gamma-ray mixed energy spectrum is analyzed, such as... Figure 4 Furthermore, the counts of common formation elements and carbon-oxygen ratio logging instruments in the standard energy range of the non-elastic gamma-ray mixed energy spectrum are obtained; S3. The inelastic gamma standard spectrum and the inelastic gamma mixed spectrum have a linear relationship in their counts within the standard energy range. A contradictory linear equation system is established, consisting of the counts of the inelastic gamma standard spectrum and the inelastic gamma mixed spectrum in each standard energy range. The contradictory linear equation system is as follows: (1) Where n is the number of elements in the standard spectrum, the (n+1)th element refers specifically to the instrument, a is the number of energy ranges selected in step S2, and b i It is the count of the mixed inelastic gamma spectrum in the i-th energy range, m i,j c represents the counting distribution probability of the characteristic inelastic gamma standard spectrum of the j-th element in the i-th energy interval. j This represents the count contribution of the j-th element to the mixed energy spectrum, also known as yield; S4. Solve the contradictory equations using the regularized nonnegative least squares method to obtain the formation carbon and oxygen yields; select a regularization factor λ in the range of 0-0.01, with an optimal regularization factor λ of 0.0005; the spectral results of the regularized nonnegative least squares method are as follows: (2) Where C is the output matrix, M is the standard spectrum matrix, λI is the regularization term, λ is the regularization factor, I is the unit diagonal matrix, and N is the mixed spectrum matrix.

[0015] S5. Using the formation carbon and oxygen yields obtained in step S4, a ratio is calculated to obtain the yield-based carbon-oxygen ratio, which is unaffected by energy dispersive spectral counting statistics, as shown in Table 1 and... Figures 5-7 .

[0016] Table 1. Application effect of regularized nonnegative least squares method in carbon-oxygen ratio logging In summary, a production-based carbon-oxygen ratio (C-O-R) calculation method based on regularized non-negative least squares is proposed. This method utilizes numerical simulation to establish non-elastic gamma standard spectra of common formation elements and C-O-R logging instruments. The regularized non-negative least squares method is then used to solve for the C-O-R, improving the accuracy of the production-based C-O-R and its sensitivity to oil layer identification, thus enabling its better application in identifying oil-bearing properties in buried hill wells.

[0017] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for calculating the carbon-oxygen ratio based on the output method using regularized nonnegative least squares, characterized in that, Includes the following steps: S1. Run the carbon-oxygen ratio logging instrument into the formation, establish an instrument-casing well formation model based on the instrument parameters and formation parameters, and obtain the common elements in the formation and the non-elastic gamma standard spectrum of the carbon-oxygen ratio logging instrument through numerical simulation; analyze each non-elastic gamma standard spectrum and select the standard energy range. S2. The formation is measured using a carbon-oxygen ratio logging instrument, and the obtained non-elastic gamma mixed energy spectrum is analyzed to obtain the common elements in the formation and the counts of the carbon-oxygen ratio logging instrument in the standard energy range of the non-elastic gamma mixed energy spectrum. S3. The non-elastic gamma standard spectrum and the non-elastic gamma mixed spectrum have a linear relationship in their counts within the standard energy range. A contradictory linear equation system is established, consisting of the counts of the non-elastic gamma standard spectrum and the non-elastic gamma mixed spectrum in each standard energy range. S4. Solve the contradictory equations using the regularized nonnegative least squares method to obtain the production of carbon and oxygen elements in the formation; S5. Using the yield of formation carbon and oxygen elements obtained in step S4 as a ratio, the yield-based carbon-oxygen ratio, which is not affected by energy spectrum counting statistics, is obtained.

2. The carbon-oxygen ratio calculation method based on regularized nonnegative least squares as described in claim 1, characterized in that: In step S1, the instrument parameters include material, source distance, instrument operating sequence, and instrument size; the formation parameters include wellbore size, wellbore fluid, casing material, casing thickness, cement sheath material, cement sheath thickness, formation material, formation porosity, and formation pore fluid; the common elements in the formation are silicon, calcium, magnesium, carbon, and oxygen.

3. The carbon-oxygen ratio calculation method based on regularized nonnegative least squares as described in claim 1, characterized in that: In step S1, the standard energy range refers to the energy range of ±0.25 MeV centered on the characteristic peaks of each element.

4. The carbon-oxygen ratio calculation method based on regularized nonnegative least squares as described in claim 1, characterized in that, In step S3, the contradictory linear equation system is: （1） Where n is the number of elements in the standard spectrum, the (n+1)th element refers specifically to the instrument, a is the number of energy ranges selected in step S2, and b i It is the count of the mixed inelastic gamma spectrum in the i-th energy range, m i,j c represents the counting distribution probability of the characteristic inelastic gamma standard spectrum of the j-th element in the i-th energy interval. j This represents the count contribution of the j-th element to the mixed energy spectrum, also known as yield.

5. The carbon-oxygen ratio calculation method based on regularized nonnegative least squares as described in claim 1, characterized in that: In step S4, the regularization factor λ is selected to be in the range of 0-0.01; the spectral result of the regularized nonnegative least squares method is as follows: （2） Where C is the output matrix, M is the standard spectrum matrix, λI is the regularization term, λ is the regularization factor, I is the unit diagonal matrix, and N is the mixed spectrum matrix.

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