Nowadays crustal stress direction well profile continuous interpretation method

Abstract

The invention provides a current crustal stress direction well profile continuous interpretation method. The method comprises the steps that S1, the current crustal stress direction is interpreted through multi-source data; s2, analyzing the applicability of the current crustal stress direction interpretation method; and S3, determining the continuous current crustal stress direction of the well section. According to the method, the current crustal stress direction in the longitudinal direction of the complex structure area such as wrinkle deformation and fracture can be accurately and continuously explained, support is provided for track optimization and borehole wall stability analysis of the horizontal well in the complex structure area, and safe and efficient exploitation of unconventional oil and gas resources is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of in-situ stress direction interpretation, and more particularly, to a method for continuously interpreting the in-situ stress direction of a well profile in the present day. Background Art

[0002] With the continuous deepening of global oil and gas exploration and development, the production of conventional oilfields is decreasing at a certain natural decline rate, and the annual production decline rate of old oilfields is also relatively high, resulting in the gradual depletion of conventional oilfields. However, unconventional oil and gas resources are rich and have become an effective supplement to conventional oil and gas resources. Unconventional oil and gas resources are usually exploited by technologies such as horizontal drilling and hydraulic fracturing. To ensure the stability of the horizontal wellbore wall and the effectiveness of the fracture, it is urgent to accurately identify the in-situ stress direction in the present day. Currently, experimental tests or well logging data interpretation are mostly used to determine the in-situ stress direction of the formation in the present day, such as identifying borehole breakouts and drilling-induced fractures based on image logging data, and identifying shear wave anisotropy characteristics based on array acoustic logging. However, the above methods are affected by lithology, the development characteristics of natural fractures, and the horizontal two-way stress difference, and there are differences in the identification accuracy. In some cases, the in-situ stress direction cannot be identified in some intervals. In addition, affected by local tectonic activities such as tectonic deformation and faults, the in-situ stress direction varies longitudinally. To accurately identify the in-situ stress direction longitudinally, it is urgent to clarify the applicable conditions of each in-situ stress direction interpretation method, synthesize the interpretation results of multiple methods, and establish a technology for continuously interpreting the in-situ stress direction of the well profile.

[0003] The Chinese patent application with the publication number CN 114442191A and the invention name "Method for Determining the In-situ Stress Direction in the Wellbore in the Present Day Based on Core and Borehole Structure Restoration" discloses a method for determining the in-situ stress direction in the present day based on core and borehole structure, including Step 1. Identification of core-induced fractures. During the processes of drilling, coring, and handling, core-induced fractures will be formed. Therefore, first, macroscopically identify the induced fractures caused by the in-situ stress in the present day on the core, and mark the convergence direction of the induced fractures with a line, which is the direction of the relatively maximum horizontal principal stress. Step 2. Core orientation based on paleomagnetic experiments. On the basis of identifying the convergence direction of the core-induced fractures, use paleomagnetic experimental tests to orient the convergence direction of the induced fractures developed in the cored core. When the single-well borehole imaging data is unclear, since it is difficult to identify induced fractures in a single well section, the imaging characteristics of the induced fractures developed in this well section can be calibrated by combining core tests, so as to determine the in-situ stress direction in the present day of the single well section.

[0004] However, the above technology is limited to identifying the in-situ stress direction in the present day of the intervals where induced fractures exist, and cannot accurately identify the in-situ stress direction response of the entire wellbore. If there are differences in the induced fracture directions, it is impossible to judge whether the identification results are accurate. Summary of the Invention

[0005] In view of this, the present application provides a method for continuously interpreting the current in-situ stress direction of a well profile to solve the problems that it is difficult to judge the accuracy of a single in-situ stress identification method when the in-situ stress direction varies longitudinally, and the interpretation result of the in-situ stress direction is discontinuous.

[0006] To achieve the above object, the technical solution adopted in the present application is as follows: A method for continuously interpreting the current in-situ stress direction of a well profile, comprising: S1: Interpreting the current in-situ stress direction from multi-source data; S2: Analyzing the applicability of the method for interpreting the current in-situ stress direction; S3: Determining the continuous current in-situ stress direction of the well profile.

[0007] Further, the step S1 specifically includes: S1.1: Interpreting the current in-situ stress direction through core testing; S1.2: Based on the principle of wellbore structure restoration, using the borehole wall collapse and induced fractures identified by imaging logging to interpret the current in-situ stress direction; S1.3: Interpreting the current in-situ stress direction based on the anisotropic characteristics of the wave velocity around the well extracted by array acoustic logging.

[0008] Further, the step S1.1 includes: S1.11: Obtaining the angle between the marked line and the geographic north pole through a paleomagnetic orientation experiment β , to achieve core orientation; S1.12: Then conducting a wave velocity anisotropy experiment, and determining the angle 𝛼 between the maximum horizontal principal stress and the marked line according to the lowest point in the wave velocity anisotropy experiment result graph; S1.13: Calculating the current in-situ stress direction according to Equation (1) θ : (1).

[0009] Further, the step S2 specifically includes: S2.1: Analyzing the applicability of interpreting the current in-situ stress direction through core testing; S2.2: Analyzing the applicability of interpreting the current in-situ stress direction through wellbore structure restoration; S2.3: Analyzing the applicability of interpreting the current in-situ stress direction through wave velocity anisotropy around the well.

[0010] Further, the step S2.1 specifically includes: Plot the cross-plot of the horizontal two-way stress difference coefficient and the maximum and minimum longitudinal wave velocity differences obtained from experimental tests to clarify the geological conditions where the experimental tests can reflect the current in-situ stress direction. The horizontal two-way stress difference coefficient is the ratio of the difference between the horizontal maximum principal stress and the horizontal minimum principal stress to the horizontal minimum principal stress.

[0011] Further, the specific steps of S2.2 include: Plot the cross-plot of the horizontal two-way stress difference coefficient and the number of induced fractures identified by imaging logging in different lithologies, and plot the cross-plot of the horizontal two-way stress difference coefficient and the width of borehole wall sloughing to clarify the geological conditions where induced fractures and borehole wall sloughing can reflect the current in-situ stress direction.

[0012] Further, the specific steps of S2.3 include: Plot the cross-plot of the horizontal two-way stress difference coefficient and the variance of the current in-situ stress direction within a given section length to clarify the geological conditions where array acoustic logging can reflect the current in-situ stress direction.

[0013] Further, the specific steps of S3 include: S3.1: Segment evaluation of the current in-situ stress direction response information in the well profile; S3.2: Determination of the current in-situ stress direction in the natural fracture development section; S3.3: Determination of the current in-situ stress direction in the single data response section; S3.4: Determination of the current in-situ stress direction in the multi-source data response section; S3.5: Analysis of the blank section of the current in-situ stress direction response; S3.6: Plotting of the continuous current in-situ stress direction interpretation profile.

[0014] Further, the steps of S3.1 include: S3.11: First, divide the well profile into a natural fracture development section and a non-natural fracture development section; S3.12: In the non-natural fracture development section, classify according to the magnitude of the horizontal two-way stress difference coefficient. Specifically, if the horizontal two-way stress difference coefficient < 0.155, it is classified as a section with unclear stress direction, where the in-situ stress direction has little impact on drilling and fracturing, and there is no need to determine the current in-situ stress direction; if the horizontal two-way stress difference coefficient is 0.155 - 0.180, it is classified as a single data response section; if the horizontal two-way stress difference coefficient > 0.180, it is classified as a multi-source data response section; for some sections limited by data and without current in-situ stress direction response information, they are classified as blank sections of the current in-situ stress direction response.

[0015] Further, the specific steps of S3.5 are as follows: The average value of the current in-situ stress direction interpretation results of the upper and lower segments of the blank section of the current in-situ stress direction response is taken as the current in-situ stress direction of the blank section of the current in-situ stress direction response.

[0016] Compared with the prior art, the beneficial effects of this application are as follows: 1. This application can accurately and continuously interpret the current in-situ stress direction in the vertical direction of complex structural areas such as fold deformation and faults, provide support for the optimization of horizontal well trajectories and the analysis of wellbore stability in complex structural areas, and achieve the safe and efficient exploitation of unconventional oil and gas resources.

[0017] 2. This application innovatively uses the multi-source information logic fusion technology for interpreting the current in-situ stress direction of deep tight reservoirs, and has a relatively high accuracy in interpreting the in-situ stress direction.

[0018] 3. The interpretation results of this application are continuous data lines in the vertical direction of the well profile, and the interpretation results can reflect the continuous variation characteristics of the in-situ stress direction in the vertical direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of this application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a flow chart of a method for continuously interpreting the current in-situ stress direction of a well profile in this application.

[0021] Figure 2 In (a) is the schematic diagram of the paleomagnetic experiment; (b) is the result diagram of the paleomagnetic experiment; (c) is the fitting result diagram of wave velocity anisotropy.

[0022] Figure 3 It is the result diagram of interpreting the current in-situ stress direction by imaging logging of Well A3.

[0023] Figure 4 It is the result diagram of interpreting the current in-situ stress direction by array acoustic logging.

[0024] Figure 5 It is the crossplot of the horizontal two-way stress difference coefficient and the maximum and minimum longitudinal wave velocity differences.

[0025] Figure 6 It is the crossplot of the number of induced fractures and the horizontal two-way stress difference coefficient.

[0026] Figure 7 It is the crossplot of the width of wellbore sloughing and the horizontal two-way stress difference coefficient.

[0027] Figure 8 It is a cross-plot of the variance of the current in-situ stress direction and the coefficient of the horizontal two-way stress difference.

[0028] Figure 9 It is a continuous interpretation profile of the current in-situ stress direction. Specific implementation manners

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application.

[0030] As Figure 1 shown, a method for continuously interpreting the current in-situ stress direction of a well profile includes: S1: Interpreting the current in-situ stress direction from multi-source data; Further, the step S1 specifically includes: S1.1: Interpreting the current in-situ stress direction through core testing; Further, the step S1.1 includes: S1.11: Obtaining the included angle of the marked line relative to the geographic north pole through a paleomagnetic orientation experiment β , realizing core orientation, as Figure 2 shown in (a) and (b) of S1.12: Then conducting a wave velocity anisotropy experiment, and determining the included angle 𝛼 of the maximum horizontal principal stress relative to the marked line according to the lowest point in the wave velocity anisotropy experiment result graph (as Figure 2 shown in (c) of S1.13: Calculating the current in-situ stress direction θ (referring to the maximum horizontal principal stress direction) according to formula (1): (1).

[0031] S1.2: Based on the principle of wellbore structure restoration, using the borehole wall sloughing and induced fractures identified by imaging logging to interpret the current in-situ stress direction; Identifying induced fractures and borehole wall sloughing through imaging logging data. The direction of the borehole wall sloughing is perpendicular to the direction of the maximum horizontal principal stress, and the direction of the induced fracture is consistent with the direction of the maximum horizontal principal stress. As Figure 3 shown, induced fractures and borehole wall sloughing were observed in the imaging logging image of Well A3 in the depth section of 5930 - 5940 m. The strike of the induced fracture is N185±5°E, and the direction of the borehole wall sloughing is N95±5°E. Therefore, it is determined that the direction of the maximum horizontal principal stress of Well A3 in the depth section of 5930 - 5940 m is N185±5°E.

[0032] S1.3: Interpret the current in-situ stress direction based on the anisotropic characteristics of the wave velocity around the well extracted from array acoustic waves.

[0033] Based on array acoustic waves, the logging data are used to separate the fast and slow shear waves (as Figure 4 shown). The direction of the fast shear wave in the non-fracture-developed area corresponds to the direction of the maximum horizontal principal stress.

[0034] S2: Analysis of the applicability of the current in-situ stress direction interpretation method; Furthermore, the step S2 specifically includes: S2.1: Analysis of the applicability of core test to interpret the current in-situ stress direction; Furthermore, the step S2.1 specifically includes: Plot the cross-plot of the horizontal two-way stress difference coefficient and the maximum and minimum longitudinal wave velocity differences obtained from experimental tests to clarify the geological conditions under which the experimental tests can reflect the current in-situ stress direction.

[0035] Plot the cross-plot of the horizontal two-way stress difference coefficient (which is the ratio of the difference between the maximum horizontal principal stress and the minimum horizontal principal stress to the minimum horizontal principal stress) and the maximum and minimum longitudinal wave velocity differences (as Figure 5 shown). There is a good positive correlation between the two. Extend the trend line to the point where the maximum and minimum longitudinal wave velocity differences are 0, and the corresponding horizontal two-way stress difference coefficient is 0.155, indicating that when the horizontal two-way stress difference coefficient < 0.155, the experimental tests cannot reflect the current in-situ stress direction.

[0036] S2.2: Analysis of the applicability of wellbore structure restoration to interpret the current in-situ stress direction; Furthermore, the step S2.2 specifically includes: Plot the cross-plot of the horizontal two-way stress difference coefficient and the number of induced fractures identified by imaging logging in different lithologies, and plot the cross-plot of the horizontal two-way stress difference coefficient and the width of wellbore breakouts to clarify the geological conditions under which induced fractures and wellbore breakouts can reflect the current in-situ stress direction.

[0037] Plot the cross-plot of the number of induced fractures, the width of wellbore breakouts and the horizontal two-way stress difference coefficient. Induced fractures develop in both sandstone and mudstone sections, and there is a positive correlation between the number of induced fractures and the stress difference coefficient. Extend the trend line. When the stress difference coefficients of sandstone and mudstone are < 0.250 and 0.180 respectively, there are no induced fractures (as Figure 6 shown). Wellbore breakouts only develop in the mudstone section, and there is a positive correlation between the width of wellbore breakouts and the stress difference coefficient. When the stress difference coefficient < 0.180, there are no wellbore breakouts (as Figure 7 shown).

[0038] S2.3: Analysis of the applicability of wave velocity anisotropy around the well to interpret the current in-situ stress direction.

[0039] Further, the step S2.3 specifically includes: Draw a crossplot of the horizontal two-way stress difference coefficient and the variance of the current in-situ stress direction interpreted by array acoustic logging within a given section length to clarify the geological conditions under which array acoustic logging can reflect the current in-situ stress direction.

[0040] In specific implementation, read the current in-situ stress direction interpreted by array acoustic logging at equal intervals of 0.125 m, calculate the variance of the current in-situ stress direction within a given section length, and draw a crossplot of it and the stress difference coefficient (as shown in Figure 8 ), and there is a negative correlation between the two. When the stress difference coefficient < 0.180, the variance > 30, indicating that the current in-situ stress direction interpreted by array acoustic logging within this section is relatively discrete and cannot accurately reflect the actual current in-situ stress direction.

[0041] Therefore, the present application innovates the multi-source information logic fusion technology for interpreting the current in-situ stress direction of deep tight reservoirs. Deeply analyze the influence of characteristics such as formation lithology and horizontal two-way stress difference on the accuracy and applicability of interpreting the current in-situ stress direction from data such as core experimental tests, electrical imaging logging, and array acoustic logging, and give the geological conditions suitable for different current in-situ stress direction interpretation methods.

[0042] S3: Determine the continuous current in-situ stress direction of the well profile.

[0043] Further, the step S3 specifically includes: S3.1: Segmentally evaluate the response information of the current in-situ stress direction of the well profile; Further, the step S3.1 includes: S3.11: First, divide the well profile into a natural fracture development section and a non-natural fracture development section; S3.12: In the non-natural fracture development section, classify according to the magnitude of the horizontal two-way stress difference coefficient. Specifically: if the horizontal two-way stress difference coefficient < 0.155, it is classified as a section with an unclear stress direction, and the in-situ stress direction in this section has little influence on drilling and fracturing, and there is no need to determine the current in-situ stress direction; if the horizontal two-way stress difference coefficient is 0.155 - 0.180, it is classified as a single data response section; if the horizontal two-way stress difference coefficient > 0.180, it is classified as a multi-source data response section; for some layers with limited data and no response information on the current in-situ stress direction, it is classified as a blank section for the response of the current in-situ stress direction.

[0044] Based on the applicability condition analysis of different methods in Step 2, the present in-situ stress direction response information of the well profile is segmented and evaluated. It is divided into five types: natural fracture development section, stress direction not obvious section, single data response section, multi-source data response section, and blank section of present in-situ stress direction response. Since the above methods are not applicable to the natural fracture development interval, the well profile is first divided into a natural fracture development section and a non-natural fracture development section. In the non-natural fracture development section, it is classified according to the magnitude of the horizontal two-way stress difference coefficient. The specific segmentation results are shown in Table 1, and the data available for in-situ stress direction interpretation are given according to the lithology and the range of horizontal two-way stress difference; limited by the actual data, there may be some intervals without present in-situ stress direction response information, and this section is defined as the blank section of present in-situ stress direction response.

[0045] Table 1 Segmented evaluation table of present in-situ stress direction response information of well profile

[0046] S3.2: Determination of present in-situ stress direction in natural fracture development section; In the natural fracture development section, the dominant group direction of effective fractures is determined as the present in-situ stress direction.

[0047] S3.3: Determination of present in-situ stress direction in single data response section; The present in-situ stress direction is given according to the core test results in the single data response section.

[0048] S3.4: Determination of present in-situ stress direction in multi-source data response section; The present in-situ stress direction in the multi-source data response section is determined as the average value of the present in-situ stress direction interpreted from multi-source data.

[0049] S3.5: Analysis of blank section of present in-situ stress direction response; The average value of the present in-situ stress direction interpretation results of the upper and lower sections of the blank section of present in-situ stress direction response is used as the present in-situ stress direction of the blank section of present in-situ stress direction response.

[0050] S3.6: Drawing of continuous present in-situ stress direction interpretation profile.

[0051] Based on the results in the above steps S3.1~S3.5, draw a continuous present in-situ stress direction interpretation profile (as Figure 9 shown).

[0052] In summary, this application interprets the current in-situ stress direction by integrating multi-source data such as core test experiments, imaging logging, and array acoustic logging; determines the applicability of each interpretation method based on characteristics such as formation lithology and horizontal two-way stress difference; evaluates the current in-situ stress direction response information of the entire wellbore section by section according to the applicability of each method, and presents an optimized method for selecting the current in-situ stress direction interpretation data and a method for determining the current in-situ stress direction in different sections. Finally, a comprehensive evaluation profile of the continuous in-situ stress direction of the well profile is constructed. This application can accurately and continuously interpret the current in-situ stress direction in the vertical direction in complex structural areas such as fold deformation and faults, provide support for the horizontal well trajectory optimization and wellbore stability analysis in complex structural areas, and achieve the safe and efficient exploitation of unconventional oil and gas resources.

[0053] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed by this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

1. A continuous interpretation method for the present in-situ stress direction well profile, characterized in that, Including: S1: Interpreting the current in-situ stress direction from multi-source data; S2: Analyzing the applicability of the current in-situ stress direction interpretation method; S3: Determining the continuous current in-situ stress direction of the well profile.

2. The continuous interpretation method of the current in-situ stress direction well profile according to claim 1, wherein, The specific steps of step S1 include: S1.1: Interpreting the current in-situ stress direction through core testing; S1.2: Based on the principle of wellbore structure restoration, using borehole wall sloughing and induced fractures identified by imaging logging to interpret the current in-situ stress direction; S1.3: Interpreting the current in-situ stress direction based on the anisotropic characteristics of the wave velocity around the well extracted by array acoustic logging.

3. The continuous interpretation method of the present in-situ stress direction well profile according to claim 2, wherein, The steps of step S1.1 include: S1.11: Obtain the angle between the marked line and the geographic north pole through the paleomagnetic orientation experiment β , and achieve core orientation; S1.12: Conducting wave velocity anisotropy experiments, and determining the angle 𝛼 between the maximum horizontal principal stress and the reference line according to the lowest point in the wave velocity anisotropy experiment result diagram; S1.13: Calculate the current in-situ stress direction according to Equation (1) θ :[[]]END]] （1）。 4. A method for continuously interpreting the well profile of the current in-situ stress direction according to any one of claims 1 to 3, characterized in that, The specific steps of step S2 include: S2.1: Analyzing the applicability of interpreting the current in-situ stress direction through core testing; S2.2: Analyzing the applicability of interpreting the current in-situ stress direction through wellbore structure restoration; S2.3: Analyzing the applicability of interpreting the current in-situ stress direction through wave velocity anisotropy around the well.

5. The continuous interpretation method of the current in-situ stress direction well profile according to claim 4, characterized in that, The specific steps of step S2.1 include: Drawing a crossplot of the horizontal two-way stress difference coefficient and the maximum and minimum longitudinal wave velocity differences obtained from experimental tests, and clarifying the geological conditions under which the experimental tests can reflect the current in-situ stress direction. The horizontal two-way stress difference coefficient is the ratio of the difference between the horizontal maximum principal stress and the horizontal minimum principal stress to the horizontal minimum principal stress.

6. A method for continuously interpreting the present in-situ stress direction well profile according to claim 5, characterized in that The specific steps of step S2.2 include: Drawing a crossplot of the horizontal two-way stress difference coefficient and the number of induced fractures identified by imaging logging in different lithologies, and drawing a crossplot of the horizontal two-way stress difference coefficient and the width of borehole wall sloughing, and clarifying the geological conditions under which induced fractures and borehole wall sloughing can reflect the current in-situ stress direction.

7. The continuous interpretation method of the current in-situ stress direction well profile according to claim 6, characterized in that, The specific steps of step S2.3 include: Drawing a crossplot of the horizontal two-way stress difference coefficient and the variance of the current in-situ stress direction within a given section length, and clarifying the geological conditions under which array acoustic logging can reflect the current in-situ stress direction.

8. A method for continuously interpreting the well profile of the current in-situ stress direction as described in claim 7, characterized in that, The specific steps of step S3 include: S3.1: Segmentally evaluating the response information of the current in-situ stress direction of the well profile; S3.2: Determining the current in-situ stress direction in the natural fracture development section; S3.3: Determining the current in-situ stress direction in the single data response section; S3.4: Determining the current in-situ stress direction in the multi-source data response section; S3.5: Analyzing the blank section of the current in-situ stress direction response; S3.6: Drawing the continuous current in-situ stress direction interpretation profile.

9. A method for continuously interpreting the well profile of the current in-situ stress direction as described in claim 8, characterized in that, The steps of step S3.1 include: S3.11: First, divide the well profile into a natural fracture development section and a non-natural fracture development section; S3.12: In the non-natural fracture development section, classify according to the magnitude of the horizontal two-way stress difference coefficient. Specifically, if the horizontal two-way stress difference coefficient < 0.155, it is classified as a section with an unclear stress direction, and the in-situ stress direction in this section has little impact on drilling and fracturing, and there is no need to determine the current in-situ stress direction; if the horizontal two-way stress difference coefficient is 0.155 - 0.180, it is classified as a single data response section; if the horizontal two-way stress difference coefficient > 0.180, it is classified as a multi-source data response section; for some layers with limited data and no current in-situ stress direction response information, they are classified as blank sections of the current in-situ stress direction response.

10. A method for continuously interpreting the well profile of the current in-situ stress direction according to claim 9, characterized in that, The specific content of step S3.5 is: The average value of the present-day in-situ stress direction interpretation results of the upper and lower segments of the blank segment of the present-day in-situ stress direction response is taken as the present-day in-situ stress direction of the blank segment of the present-day in-situ stress direction response.

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