A shale oil density curve wellbore environment correction method based on TRA experiment

Abstract

The present application relates to a kind of shale oil density curve wellbore environment correction method based on TRA experiment.Solve the problem of the distortion of shale oil formation density logging curve under the influence of the expansion condition, including the following steps: determining sample density by TRA experimental data;Combining test data and logging density, caliper curve, obtaining the relative change amount of expansion and the relative change amount of density;Fitting the relative change amount of expansion and the relative change amount of density, determine the correction coefficient;Finally, the corrected density curve is calculated.The present application innovatively combines TRA test, and calculates rock sample density value based on accurate rock skeleton density and porosity data, so as to gradually complete the purpose of correcting logging density curve, play an important role for subsequent calculation of shale oil porosity and reservoir evaluation, and provide reliable quality guarantee.

Description

Technical Field

[0001] This invention relates to a wellbore environment correction method for shale oil density curves based on TRA experiments, belonging to the field of oil and gas field development technology. Background Technology

[0002] Reservoir physical properties are crucial for reservoir classification, sweet spot evaluation, and reserve calculation. Generally, density logging plays a significant role in porosity calculation due to its high resolution. However, given the geological characteristics of shale oil, in shale formations with high clay content and well-developed laminae and microfractures, wellbore collapse and enlargement are common due to the lack of sandstone support. Density logging operates by measuring close to the wellbore wall; in cases of wellbore collapse or enlargement, the pusher cannot maintain close contact with the wellbore wall, leading to data distortion. Once density data is distorted by enlargement, accurate calculation of physical properties becomes impossible. Therefore, eliminating the influence of the wellbore environment and correcting density curves in shale oil reservoirs is essential.

[0003] Previous studies have extensively investigated correction methods for density logging. Commonly used environmental correction methods include borehole enlargement correction, standard layer statistical analysis, and rock physical modeling. Borehole enlargement correction involves establishing a threshold value in the enlarged borehole section to replace outliers in the curve. If the density measurement value decreases in the enlarged section, this threshold value replaces the decreased portion of the measurement. However, this method only removes outliers and does not reflect the curve's inherent variation patterns. Standard layer statistical analysis does not consider the irregularities in reservoir borehole enlargement. Rock physical modeling requires extensive basic data, involves complex procedures, and is time-consuming, making it difficult to master and widely adopted. Xiao Yufeng's "Wellbore Environment Correction Method for Density Logging [P]" (Patent No. CN113356833A, 2021-09-07) determines the estimated value of the density curve based on the relative change in borehole diameter and the change in density. He Wenyuan's "A Density Curve Distortion Correction Method for Helical Wellbores [P]" (Patent No. CN112412435A, 2021-02-26) uses the density curve of a reference well unaffected by the helical wellbore for spectral analysis to determine the noise frequency band of the well affected by the helical wellbore; a wavelet filter is constructed to reconstruct and correct the density curve affected by the helical wellbore. This method solves the problem of density curve distortion in helical wellbores, but it involves wavelet filters and spectral analysis, making it relatively complex. Ma Long published an article entitled "Research on Wellbore Correction Method for Density Logging under Special Conditions" in the 19th Special Issue of Chinese Geophysics 2013. The article proposes that, without considering the influence of mud invasion, the detection depth of density logging is positively correlated with the source distance of the instrument and negatively correlated with the density of the medium within the detection range. The corrected density logging model is established by using the readings of the long and short source distance detectors and the detection depth of the long and short source distance detectors.

[0004] The above methods can achieve good results in density logging environment correction under ordinary sandstone and mudstone conditions. However, they are not suitable for shale formations with well-developed laminae. Shale oil reservoirs experience irregular distortion data due to well diameter enlargement, making it impossible to correct density logging values ​​using well diameter and density curve fitting alone. Summary of the Invention

[0005] This invention aims to overcome the problem in the prior art where density logging curves in existing shale oil reservoirs are severely distorted due to non-formation factors under conditions of poor wellbore and mud quality. Instead, it provides a wellbore environment correction method for shale oil density curves based on TRA (Rapid Tracing and Refining) experiments. This TRA-based method, combined with TRA experiments, calculates the density value of rock samples based on accurate rock skeleton density and porosity data, thereby gradually correcting the logging density curve. This plays a crucial role in subsequent calculations of shale oil porosity and reservoir evaluation, providing reliable quality assurance.

[0006] The present invention solves its problem through the following technical solution: the shale oil density curve well environment correction method based on TRA experiments includes the following steps: S1: Perform well logging on shale oil reservoirs to obtain logging curves; S2: Collect TRA experimental data through TRA experiments; calculate the density value DEN of the experimental sample. 实验样品 To characterize the physical properties of the reservoir; S3: Obtain the relative change in borehole enlargement based on the borehole diameter data obtained from the logging curve; S4: Density value DEN of the experimental sample calculated based on step S2 实验样品 By comparing the density curve obtained from well logging measurements, the relative change in density of the experimental sample can be obtained; S5: Based on the calculated relative change in diameter expansion and the relative change in density of the experimental sample, establish a cross-plot of the relative change in diameter expansion and the relative change in density of the experimental sample, and determine the response equation by fitting the relationship; obtain the relative change in density of the density curve of the entire well section based on the response equation determined by the fitting relationship. S6: Based on the density relative change (DENV) of the density curve of the whole well section obtained in step S5 and the density curve to be corrected in the logging, determine the corrected density curve.

[0007] Furthermore, the logging curves include: volume density curve (DEN), dual-diameter logging curves (CALX, CALY), and bit diameter curves (BIT). The density value DEN is obtained through the bulk density curve; the logging diameter data is obtained through the dual-diameter logging curve, which includes the logging measurement of the horizontal diameter CALX and the logging measurement of the vertical diameter CALY; and the drill bit diameter BIT is obtained through the drill bit diameter curve.

[0008] Furthermore, the TRA experimental data in S2 includes density skeleton ρma and porosity φ; And / or, The density of the test sample was calculated using the following formula: DEN 实验样品 =(1-φ)*ρ ma +φ*ρ f In the formula: DEN experimental samples The calculated density value of the test sample, φ To test and measure porosity, ρ ma The rock skeleton values ​​measured in the experiment, ρ f ρ represents the fluid density resistivity.

[0009] Furthermore, the method for obtaining the relative change in the diameter of S3 is as follows: Obtain the horizontal wellbore diameter from logging measurements CALX ; Obtain the vertical wellbore diameter CALY from well logging measurements; Obtain drill bit diameter BIT ; Through the relative change in diameter expansion CALV and CALX CALY BIT relational calculation yields The relative change in diameter; calculate Relative change in diameter The relation is: CALV = (CALX + CALY) - BIT * 2 In the formula: CALV This represents the relative change in diameter. CALX CALY is for measuring the horizontal wellbore diameter in well logging, and CALY is for measuring the vertical wellbore diameter in well logging. BIT This refers to the drill bit diameter, which is typically 21.6 cm.

[0010] Furthermore, step S4 is based on the density value DEN of the experimental sample. 实验样品 The method for obtaining the relative change in density of the experimental sample is as follows: Obtain the density data (DEN) to be corrected from well logging measurements and the calculated density values ​​of the experimental samples. DEN experimental samples ; Using the relative change in density of the experimental sample DENV 实验样品With DEN and DEN 实验样品 The relative change in density of the experimental sample was calculated using the relational formula. And / or, The formula for calculating the relative change in density of the experimental sample is as follows: DENV 实验样品 =DEN-DEN 实验样品 In the formula: DENV 实验样品 The density of the experimental sample is the relative change in density, and DEN is the density data to be corrected from well logging measurements. DEN experimental samples This is the calculated sample test density value.

[0011] Further, in step S5, a cross-plot is established between the relative change in diameter expansion and the relative change in density of the experimental sample. The response equation determined by the fitting relationship is: DENV =0.0164 e0.1786*CALV (1) In the formula: DENV represents the relative change in density of the density curve throughout the entire well section. e is the power exponent, CALV This represents the relative change in diameter.

[0012] And / or, Furthermore, the response equation determined by the fitted relationship is applicable to cases where the well diameter change is less than twice the drill bit diameter.

[0013] Further, in step S5, a cross-plot is established between the relative change in diameter expansion and the relative change in density of the experimental sample. The response equation determined by the fitting relationship is: DENV =0.0145*CALV-0.0089 (2) Furthermore, the response equation determined by the fitted relationship is applicable to cases where the well diameter variation is greater than twice the drill bit diameter.

[0014] Furthermore, the formula for calculating the corrected density curve DENC in step S6 is as follows: DENC = DEN + DENV In the formula: DENC is the corrected density curve, and DEN is the density curve to be corrected from well logging measurements. DENV This represents the relative change in the density curve across the entire well section.

[0015] Compared with the above-mentioned background technology, the present invention has the following beneficial effects: This invention presents a wellbore environment correction method for shale oil density curves based on TRA (Radar Transformation) experiments. Applicable to shale oil formations, it addresses the issue of inconsistent distortion data due to wellbore enlargement in shale oil, making it impossible to correct density logging values ​​using only wellbore diameter and density curves. This method solves the problem of density logging curve distortion caused by wellbore enlargement in shale oil formations. The method involves determining the sample density using TRA experimental data; combining experimental data with logging density and wellbore diameter curves to obtain the relative changes in wellbore enlargement and density; fitting the relationship between the relative changes in wellbore enlargement and density to determine the correction coefficients; and finally, calculating the corrected density curve. This invention innovatively combines TRA experiments with precise rock skeleton density and porosity data to calculate rock sample density values, thereby gradually correcting the logging density curve. This plays a crucial role in subsequent calculations of shale oil porosity and reservoir evaluation, providing reliable quality assurance. The method can be implemented through computer programming, is simple and efficient, and highly practical. Attached Figure Description

[0016] Appendix Figure 1 This is a flowchart of the density correction method according to an embodiment of the present invention; Appendix Figure 2a This is a form density wellbore environment correction diagram according to an embodiment of the present invention; Appendix Figure 2b This is another form of density wellbore environment correction diagram according to an embodiment of the present invention; Appendix Figure 3 This is a density error analysis diagram according to an embodiment of the present invention; Appendix Figure 4 This is a diagram illustrating the results of density wellbore correction curves in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the following will take the specific implementation process of the shale oil density curve well environment correction method based on TRA experiment in the Jilin Oilfield shale oil H258 well as an example, and describe the embodiments of this invention in further detail with reference to the accompanying drawings.

[0018] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0019] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0020] The concept of this invention is as follows: Well logging is performed on shale oil reservoirs to obtain volumetric density and dual-diameter logging curves; experimental data, well diameter measurements, and wellbore diameter and density measurements are collected; the density of the experimental sample is obtained based on the skeleton density and porosity data measured by TRA experiments; the relative change in diameter and density are obtained based on the logging data; the relationship between the relative change in diameter and density is fitted to determine the correction coefficient; and the corrected density curve is determined based on the correction coefficient, the density curve to be corrected, and the actual density measurement value. This achieves the purpose of correcting the density curve of the shale oil reservoir.

[0021] like Figure 1 As shown, to realize this inventive concept, this shale oil density curve well environment correction method based on TRA experiments includes the following steps: Step S101: Perform well logging on the shale oil reservoir to obtain well logging curves, which include: volume density curve DEN, dual-diameter well logging curves (CALX, CALY), and drill bit diameter curves (BIT); wherein, the volume density curve is used for subsequent calculation of density change, and the dual-diameter curves and drill bit diameter are used to calculate well diameter change.

[0022] Step S102: Collect TRA experimental data and calculate the density value DEN of the experimental sample using the formula. 实验样品 .

[0023] The TRA experimental data includes density skeleton ρma and porosity φ, and the density value DEN of the experimental sample is calculated using a formula. 实验样品 The density of the test sample is calculated using the following formula to characterize the physical properties of the reservoir: DEN 实验样品 =(1-φ)*ρ ma +φ*ρ f In the formula: DEN experimental samples For calculation Experimental sample density value, φ To test and measure porosity, ρ ma The rock skeleton values ​​measured in the experiment, ρ f ρ represents the fluid density resistivity.

[0024] Step S103: Using well logging caliper data, obtain the relative change in enlargement, whereby the well logging caliper data includes dual-caliper logging curves (CALX, CALY) and bit diameter curves (BIT); the relative change in enlargement is obtained by calculating it using the following formula: CALV = (CALX + CALY) - BIT * 2 In the formula: CALV This represents the relative change in diameter. CALX CALY is for measuring the horizontal wellbore diameter in well logging, and CALY is for measuring the vertical wellbore diameter in well logging. BIT This refers to the drill bit diameter, which is typically 21.6 cm.

[0025] Step S104: Based on the experimental sample density data calculated above and the well logging density curve, obtain the relative change in density of the experimental sample. The calculation formula is as follows: DENV 实验样品 =DEN-DEN 实验样品 In the formula: DENV 实验样品 The density of the experimental sample is the relative change in density, and DEN is the density data to be corrected from well logging measurements. DEN 实验样品 This represents the calculated density value of the experimental sample.

[0026] Step S105: Establish a cross-plot between the relative change in diameter expansion and the relative change in density of the experimental sample. Use the change in diameter expansion to characterize the change in density, and fit the relationship to determine the two response equations. The two response equations are as follows: DENV=0.0164 e0.1786*CALV (1) DENV = 0.0145 * CALV - 0.0089 (2) In the formula: DENV Let e ​​represent the relative change in density across the entire well section density curve, where e is the power exponent. CALV This represents the relative change in diameter.

[0027] Equation (1) applies to well diameter changes less than twice the drill bit diameter; Equation (2) applies to well diameter changes greater than twice the drill bit diameter.

[0028] Step S106: Based on the relative density change (DENV) of the obtained density curve for the entire well section and the corrected density curve of the well to be logged, determine the corrected density curve. The formula for calculating the corrected density curve (DENC) is as follows: DENC = DEN + DENV In the formula: DENC is the corrected density curve, and DEN is the density curve to be corrected in the well logging. DENV This represents the relative change in density across the entire well section density curve.

[0029] The corrected density curve can be obtained by programming to execute the wellbore environment correction method for shale oil density curves based on TRA experiments. This method is simpler and more efficient. Example

[0030] The specific implementation of this invention is illustrated by its application in the H258 shale oil well in the Jilin Oilfield, using the well environment correction method for shale oil density curves based on TRA experiments. The embodiments disclosed herein employ the following technical solutions.

[0031] Specifically, this method will be further explained using a well in a certain oil field as an example. Figure 4 This is a density curve correction result diagram of an embodiment of this disclosure, such as... Figure 4 As shown in the figure, channels 1-4 are the original curves from well logging and well logging measurements, and channels 5-9 are the experimental analysis and result curves. The first channel is the interpretation conclusion, the second channel is the lithology curve, including the dual-diameter curves CALX and CALY, the third channel is the difference between the dual-diameter curves and the well diameter, and the corrected well diameter curve, the fourth channel is the depth channel, the fifth channel is the core description, the sixth channel is the TRAL experiment density skeleton value bar chart, the sixth channel is the effective porosity of the TRAL experiment, the seventh channel is the density value calculated from the TRAL experiment data and the original well logging density, and the ninth channel is the density bar chart based on the TRAL experiment, the corrected density calculation value and the original well logging density curve.

[0032] Analysis of the well logging curves indicates that in well-logged layers 93-94, the CALX curve shows a depth of 25-32 cm, and the CALY curve shows a depth of 23-28 cm. The CALV curve shows a significant enlargement, ranging from 2.48-16 cm. The lithology is mudstone and shale. The TRAL experimental density skeleton values ​​range from 2.6-2.8 g / cm³. 3 Between these values, the effective porosity from the TRAL test was 2-4%, and the density calculated from the TRAL test data ranged from 2.5-2.8 g / cm³. 3 The original density from well logging ranged from 2.3 to 2.7, with actual density values ​​ranging from 2.4 to 2.6 g / cm³. 3 The enlargement of the wellbore caused severe distortion of the density curve, resulting in inconsistency with the density measured in the TEAL experiment. After subsequent density correction using the method of this invention, the calculated density values ​​were consistent with the TEAL experimental density, showing a good correlation, thus proving the feasibility of the density correction method of this invention.

[0033] Well logging interpretation layers 97-99 show CALX values ​​of 23-37 cm and CALY values ​​of 25-27 cm in the dual-diameter curves. The CALV value ranges from 2.4-6.8 cm, with no significant enlargement observed. The lithology is shale with argillaceous bands. The TRAL experimental density skeleton values ​​range from 2.6-2.7 g / cm³. 3 Between these values, the effective porosity from the TRAL test was 2.6%–4.3%, and the density calculated from the TRAL test data ranged from 2.5%–2.64 g / cm³. 3The original density from well logging ranged from 2.3 to 2.7, with actual density values ​​ranging from 2.5 to 2.65 g / cm³. 3 Since no diameter expansion occurred, the consistency difference was only observed in the range of 2434.4-2435.2m. After subsequent density correction using the method of this invention, the calculated density values ​​showed a high degree of matching and good correlation with the TEAL experimental density, proving the feasibility of the density correction method of this invention.

[0034] In the density environment correction chart, the density change is calculated by fitting the density difference data between the dual wellbore diameter and drill bit diameter with the density difference data from TRA and logging. DENV=0.0164 e0.1786*CALV (1) DENV = 0.0145 * CALV - 0.0089 (2) The correlation coefficients were 0.7375 and 0.7788, indicating a good correlation. In the cross plot, the Y-axis represents the density change (DENV), and the X-axis represents the diameter expansion change (CALV) (see...). Figure 2a , Figure 2b ).

[0035] The density values ​​analyzed by the TRAL experiment were compared with the corrected density values. In the cross-plot, the Y-axis represents the density values ​​analyzed by the TRAL experiment, and the X-axis represents the calculated density value (DENC). The correlation coefficient is around 0.8726 (see...). Figure 3 ).

[0036] The above methods eliminate the density curve distortion caused by the enlargement of shale oil reservoirs, playing an important role in subsequent porosity calculations and laying the foundation for reservoir evaluation.

[0037] Those skilled in the art will understand that, in the above-described method of the specific implementation, the order in which each step is written does not imply a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic.

[0038] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A wellbore environment correction method for shale oil density curves based on TRA experiments, characterized in that: Includes the following steps: S1: Perform well logging on shale oil reservoirs to obtain logging curves; S2: Collect TRA experimental data through TRA experiments; The density value DEN of the experimental sample was calculated. 实验样品 To characterize the physical properties of the reservoir; S3: Obtain the relative change in borehole enlargement based on the borehole diameter data obtained from the logging curve; S4: Density value (DEN) of the experimental sample calculated based on S2 实验样品 By comparing the density curve obtained from well logging measurements, the relative change in density of the experimental sample can be obtained; S5: Based on the calculated relative change in diameter expansion and the relative change in density of the experimental sample, establish a cross-plot of the relative change in diameter expansion and the relative change in density of the experimental sample, and determine the response equation by fitting the relationship; obtain the relative change in density of the density curve of the entire well section based on the response equation determined by the fitting relationship. S6: Based on the density relative change (DENV) of the density curve of the whole well section obtained in S5 and the density curve to be corrected in the logging, determine the corrected density curve; The response equation determined by the S5 fitting relationship is: DENV =0.0164e 0.1786*CALV (1) In the formula: DENV represents the relative change in density of the density curve throughout the entire well section. e is the power exponent, CALV This represents the relative change in diameter. Formula (1) The response equation determined by the fitting relationship is applicable to cases where the well diameter change is less than twice the drill bit diameter; The response equation determined by the fitting relationship is: DENV =0.0145*CALV-0.0089 (2) The response equation determined by the fitting relationship in formula (2) is applicable to cases where the well diameter change is greater than twice the drill bit diameter.

2. The wellbore environment correction method for shale oil density curves based on TRA experiments according to claim 1, characterized in that: The logging curves include: bulk density curve, dual-diameter logging curve, and drill bit diameter curve; And / or, The density value DEN is obtained through the bulk density curve; the logging diameter data is obtained through the dual-diameter logging curve, which includes the logging measurement of the horizontal diameter CALX and the logging measurement of the vertical diameter CALY; and the drill bit diameter BIT is obtained through the drill bit diameter curve.

3. The wellbore environment correction method for shale oil density curves based on TRA experiments according to claim 1, characterized in that: The TRA experimental data in S2 include density skeleton ρma and porosity φ; And / or, The density of the experimental sample was calculated using the following formula: DEN 实验样品 =(1-φ)*ρ ma +φ*ρ f In the formula: DEN 实验样品 The calculated density value of the experimental sample, φ To test and measure porosity, ρ ma The rock skeleton values ​​measured in the experiment, ρ f ρ represents the fluid density resistivity.

4. The wellbore environment correction method for shale oil density curves based on TRA experiments according to claim 1, characterized in that: The method for obtaining the relative change in the diameter expansion of S3 is as follows: Obtain the horizontal wellbore diameter from logging measurements CALX ; Obtain the vertical wellbore diameter CALY from well logging measurements; Obtain drill bit diameter BIT ; The relative change in diameter is calculated using the relationship between CALV and CALX, CALY, and BIT; the relationship for calculating the relative change in diameter is: CALV = (CALX + CALY) - BIT * 2 In the formula: CALV This represents the relative change in diameter. CALX CALY is for measuring the horizontal wellbore diameter in well logging; CALY is for measuring the vertical wellbore diameter in well logging. BIT The drill bit diameter is 21.6 cm.

5. The wellbore environment correction method for shale oil density curves based on TRA experiments according to claim 1, characterized in that: S4 is based on the density value DEN of the experimental sample. 实验样品 The method for obtaining the relative change in density of the experimental sample is as follows: Obtain the density data (DEN) to be corrected from well logging measurements and the calculated density values ​​of the experimental samples. DEN 实验样品 ; Using the relative change in density of the experimental sample DENV 实验样品 With DEN and DEN 实验样品 The relative change in density of the experimental sample was calculated using the relational formula. And / or, The formula for calculating the relative change in density of the experimental sample is as follows: DENV 实验样品 =DEN-DEN 实验样品 In the formula: DENV 实验样品 The density of the experimental sample is the relative change in density, and DEN is the density data to be corrected from well logging measurements. DEN 实验样品 This represents the calculated density value of the experimental sample.

6. The wellbore environment correction method for shale oil density curves based on TRA experiments according to claim 1, characterized in that: The formula for calculating the corrected density curve DENC in S6 is: DENC = DEN + DENV In the formula: DENC is the corrected density curve, and DEN is the density curve to be corrected from well logging measurements. DENV This represents the relative change in the density curve across the entire well section.

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