Method and system for correcting anisotropy of longitudinal wave time difference of highly-deviated horizontal well

Abstract

The invention provides a highly-deviated horizontal well longitudinal wave time difference anisotropy correction method and system, and the method comprises the steps: building a longitudinal wave time difference anisotropy inversion model based on an elliptic equation, building a longitudinal wave time difference correction chart, and building a longitudinal wave anisotropy coefficient logging interpretation model through the longitudinal wave time difference logging information of multiple wells at the same layer in a research area; and finally, longitudinal wave time differences in the vertical direction and the horizontal direction which are not influenced by anisotropy are calculated by combining the longitudinal wave time differences measured in the high-inclination / horizontal well, natural gamma and a hole drift angle logging curve. The method has both theoretical basis and actual data, the objective rule obtained through combination of theory and reality is high in universality and precision, can be operated by general interpretation personnel, and is beneficial to rapid and large-scale application in production.

Description

Technical Field

[0001] The invention belongs to the technical field of reservoir evaluation, and relates to a method and system for correcting anisotropy of P-wave time difference in a highly deviated horizontal well. Background Art

[0002] With the rapid development of oil and gas exploration and development, there will be more and more high-angle horizontal wells. Since there is a certain angle between the high-angle horizontal well and the actual formation, the P-wave time difference measured by the high-angle horizontal well is very different from that of the vertical well in the same formation. As the angle increases, the anisotropy will be more affected, and there will be obvious velocity anisotropy in the vertical and horizontal directions. Therefore, before using the P-wave time difference logging curve of the high-angle / horizontal well, the curve needs to be corrected.

[0003] At present, the correction of P-wave time difference in horizontal wells is mainly carried out by core experimental analysis and statistical translation method. The core experimental analysis method is the most direct method to study the acoustic anisotropy of horizontal wells. The P-wave time difference in the vertical and horizontal directions is measured by core experiments, the P-wave anisotropy coefficient of the core is calculated, and then the average value of the regional P-wave anisotropy coefficient is determined, and finally the linear model is used for correction. In the statistical translation method, the layer section corresponding to the target layer of the horizontal well is first selected in the control well of the horizontal well, and the frequency histogram of the P-wave time difference of the horizontal well and its control well is made respectively to obtain the respective peak values, and then the P-wave time difference curve of the horizontal well is translated and corrected, and the correction amount is the difference between the peak values ​​of the two. In the later research process, it was found that due to the rapid lateral distribution of the lithology, physical properties and other attributes of unconventional oil and gas reservoirs, and the angle between the well trajectory and the formation is constantly changing, simple linear fitting and translation correction will have large errors. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to solve the problems that due to the influence of formation anisotropy, the P-wave time difference measurement value of highly inclined horizontal wells is greatly different from that of vertical wells, which affects the accuracy of reservoir evaluation. A method and system for anisotropy correction of P-wave time difference of highly inclined horizontal wells are proposed, which calculate the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy, and provide basic data for subsequent fine evaluation of horizontal well reservoirs.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells comprises the following steps:

[0007] Based on the variation law of P-wave time difference with well inclination and mathematical method, an anisotropic inversion model of P-wave time difference is established;

[0008] The P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients is established through the P-wave time difference anisotropy inversion model;

[0009] The P-wave time-difference logging data of multiple wells in the same layer of the study area were selected, and the P-wave anisotropy coefficient logging interpretation model was established using the least squares method.

[0010] According to the logging interpretation model of P-wave anisotropy coefficient and based on the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, the P-wave time difference logging curves measured in highly deviated horizontal wells are corrected to obtain the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy.

[0011] Preferably, the longitudinal wave time difference anisotropy inversion model is constructed using an elliptical model, and the specific process is:

[0012] The ellipse model equation is:

[0013]

[0014] The points on the ellipse satisfy the equation of the line in polar coordinates:

[0015] y=ctg(θ)·x (2)

[0016] By combining equations (1) and (2), we can get the anisotropic inversion model of P-wave time difference when the well inclination angle is θ, which is expressed as:

[0017]

[0018] Where: AC θ is the longitudinal wave time difference when the well inclination angle is θ, in μs / ft; AC v is the vertical longitudinal wave time difference, in μs / ft; AC h is the horizontal longitudinal wave time difference, in μs / ft; θ is the well inclination, in degrees.

[0019] Preferably, the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients is established by simulating and analyzing the change law of P-wave time difference response under different well inclination angles and different P-wave anisotropy coefficients.

[0020] Preferably, in the simulation analysis process, the well inclination angle θ is changed from the vertical direction to the horizontal direction at a change interval of 5°, from 0°, 5°, 10°, ..., 90°; the longitudinal wave anisotropy coefficient ε is changed at a change interval of 0.05, from 0, 0.05, 0.1, ..., 0.5 to analyze the ratio of the longitudinal wave time difference to the vertical direction longitudinal wave time difference at different well inclination angles The changing law of the P-wave time difference is obtained, thus establishing the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients.

[0021] Preferably, the expression of the longitudinal wave anisotropy coefficient ε is:

[0022]

[0023] In the formula, AC v is the vertical longitudinal wave time difference, in μs / ft; AC h It is the time difference of longitudinal wave in horizontal direction, and its unit is μs / ft.

[0024] Preferably, the P-wave anisotropy coefficient logging interpretation model uses the logging acoustic data of multiple wells in the same layer to establish the relationship between the P-wave anisotropy coefficient and the shale content. The specific process is:

[0025] Based on the same layer in the study area, the layer section corresponding to the target layer of the horizontal well is selected in the control well of the horizontal well to make the frequency histogram of the longitudinal wave time difference between the horizontal well and the control well, and obtain their respective peaks, including the horizontal longitudinal wave time difference AC h and the vertical longitudinal wave time difference AC v , and the volume content of mud in the control well V sh .

[0026] Preferably, the shale volume content V of the control well is sh The natural gamma logging curve is used to obtain the expression:

[0027]

[0028] Among them, V sh is the volume content of mud, in %; ΔGR is the relative value of natural potential; GR is the natural gamma logging value, GR min is the natural gamma value of the pure sandstone section, GR max is the natural gamma value of the pure mudstone section; GCUR is the Hilch coefficient.

[0029] Preferably, the longitudinal wave anisotropy coefficient ε is established by the least square method. sh The statistical model relationship is expressed as:

[0030]

[0031] Where a and b are the fitting coefficients of the model.

[0032] Preferably, the P-wave time difference, natural gamma and well inclination logging curves measured in highly deviated / horizontal wells are combined, according to the P-wave anisotropy coefficient logging interpretation model, and based on the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, the vertical and horizontal P-wave time differences in highly deviated / horizontal wells that are not affected by anisotropy are calculated.

[0033] A P-wave time difference anisotropy correction system for highly deviated horizontal wells, comprising:

[0034] The inversion model building module is used to build an anisotropic inversion model of P-wave time difference based on the variation law of P-wave time difference with well inclination and mathematical methods;

[0035] Correction chart module, used to establish P-wave time difference correction charts under different well inclination angles and different P-wave anisotropy coefficients;

[0036] The interpretation model building module is used to select the P-wave time difference logging data of multiple wells in the same layer of the study area and establish the P-wave anisotropy coefficient logging interpretation model using the least squares method;

[0037] The P-wave time difference correction module is used to correct the P-wave time difference logging curve measured in the highly deviated horizontal well according to the P-wave anisotropy coefficient logging interpretation model and the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, so as to obtain the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy.

[0038] Compared with the prior art, the present invention has the following beneficial technical effects:

[0039] The present invention provides a method and system for correcting the anisotropy of P-wave time difference in highly deviated horizontal wells. The method constructs an inversion model of P-wave time difference anisotropy based on elliptic equations; establishes a P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients; uses P-wave time difference logging data of multiple wells in the same layer of the study area, and adopts the least square method to establish a logging interpretation model of P-wave anisotropy coefficient; combines the P-wave time difference, natural gamma and well inclination logging curves measured in highly deviated / horizontal wells to calculate the vertical and horizontal P-wave time differences that are not affected by anisotropy. The present invention has both theoretical basis and practical data. The objective law obtained by combining theory with practice has strong universality and high precision. It can be operated by general interpreters and is conducive to rapid large-scale application in production. In order to solve the problem that the P-wave time difference measurement value of highly inclined horizontal wells is greatly different from that of vertical wells due to the influence of formation anisotropy, which affects the accuracy of reservoir evaluation, a P-wave time difference correction method for highly inclined horizontal wells based on elliptical model is proposed. The P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy are calculated to provide basic data for subsequent fine evaluation of horizontal well reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A flow chart of a method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells provided by an embodiment of the present invention;

[0042] Figure 2 A schematic diagram of an anisotropic inversion model of longitudinal wave time difference according to an embodiment of the present invention;

[0043] Figure 3 The longitudinal wave time difference correction chart under the conditions of different well inclination angles and different longitudinal wave anisotropy coefficients described in the embodiment of the present invention;

[0044] Figure 4 The P-wave anisotropy coefficient logging interpretation model described in the embodiment of the present invention;

[0045] Figure 5 A schematic diagram of a P-wave time difference correction result for a highly deviated horizontal well according to an embodiment of the present invention;

[0046] Figure 6 This is a comparison diagram of the corrected longitudinal wave time difference and the vertical longitudinal wave time difference described in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0048] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0049] See also Figure 1 The embodiment of the present invention provides a method for correcting anisotropy of P-wave time difference in a highly deviated horizontal well, comprising the following steps:

[0050] Step 1: Based on the variation law of P-wave time difference with well inclination angle and mathematical methods, an anisotropic inversion model of P-wave time difference is established. The inversion model is a simplified elliptic equation, such as Figure 2 As shown, the expression is:

[0051]

[0052] The points on the ellipse satisfy the equation of the line in polar coordinates:

[0053] y=ctg(θ)·x (2)

[0054] By combining equations (1) and (2), we can get the P-wave time difference anisotropy inversion model when the well inclination angle is θ, which is expressed as:

[0055]

[0056] Where: AC θ is the longitudinal wave time difference when the well inclination angle is θ, μs / ft; AC v is the vertical longitudinal wave time difference, μs / ft; AC h is the horizontal longitudinal wave time difference, μs / ft; θ is the well inclination, degrees.

[0057] Step 2: By simulating and analyzing the change law of P-wave time difference response under different well inclination angles and different P-wave anisotropy coefficients, a P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients was established, as shown in Figure 2. Figure 3 As shown. Among them, the well inclination angle θ changes from the vertical direction to the horizontal direction at an interval of 5°, 0°, 5°, 10°, ..., 90°; the longitudinal wave anisotropy coefficient ε changes from 0, 0.05, 0.1, ..., 0.5 at an interval of 0.05. The expression of the longitudinal wave anisotropy coefficient ε is:

[0058]

[0059] Step 3: Using the same layer in the study area, select the layer section corresponding to the target layer of the horizontal well in the control well of the horizontal well to make the frequency histogram of the P-wave time difference between the horizontal well and the control well, and obtain their respective peak values, namely, the horizontal P-wave time difference AC h and the vertical longitudinal wave time difference AC v , and the shale content V of the control well sh .

[0060] Volume content of mud in the formation V sh The natural gamma logging curve is used to obtain the expression:

[0061]

[0062] Among them, V sh is the mud content, %; ΔGR is the relative value of natural potential, decimal; GR is the natural gamma logging value, API; GR minis the natural gamma value of pure sandstone section, API; GR max is the natural gamma value of pure mudstone section, API; GCUR is the Hilch coefficient.

[0063] The logging interpretation model of the P-wave anisotropy coefficient ε is established by the least squares method. sh Statistical relationships, such as Figure 4 As shown, the expression is:

[0064]

[0065] In the formula, a and b are the fitting coefficients of the model, a=0.0113, b=0.0378, and the correlation coefficient of the model reaches 0.7051.

[0066] Step 4: Combine the P-wave time difference, natural gamma and well inclination logging curves measured in highly deviated horizontal wells, according to the P-wave anisotropy coefficient logging interpretation model, and based on the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, calculate the vertical and horizontal P-wave time differences in highly deviated / horizontal wells that are not affected by anisotropy.

[0067] The natural gamma and well inclination logging curves measured in highly deviated horizontal wells are two important curves used to obtain formation information in the well. Measuring natural gamma and well inclination in highly deviated horizontal wells requires the use of special logging tools and techniques, which usually involves using logging tools to go down the well and record data. For natural gamma measurement, gamma ray detectors are usually used, while well inclination measurement is usually obtained using inclination sensors and direction sensors;

[0068] In the actual data processing process, a method for correcting the anisotropy of the P-wave time difference in highly inclined / horizontal wells is implemented by writing a program. Figure 5 This is a schematic diagram of the correction results of the longitudinal wave time difference of a high-angle horizontal well. The well section shown in the figure includes the entry point (A) of the horizontal well, with a depth of 4217.0m. The well inclination angle of this section ranges from 55° to 90°. Before correction, the longitudinal wave time difference distribution range from the entry point (A) to the final target point (B) of the horizontal well on the logging curve is 56.2 to 66.4μs / ft, and the longitudinal wave time difference distribution range of the corresponding vertical well oil layer section is 60.1 to 67.2μs / ft. The normal distribution diagram shows that the central value of the longitudinal wave time difference of the horizontal well is 61.4μs / ft, and the central value of the longitudinal wave time difference of the vertical well is 63.6μs / ft. There is a certain difference between the two ( Figure 6 ). Correct the P-wave time difference curve of the horizontal well, such as Figure 5 Shown are the P-wave anisotropy coefficient calculated by equation (6) (Track 5 in the figure), the P-wave time difference before and after correction (Track 6 in the figure), and the correction amount of the P-wave time difference (Track 7 in the figure). Figure 6This is a comparison chart of the corrected P-wave time difference value and the distribution range of the P-wave time difference value of the vertical well. After correction, the distribution range of the P-wave time difference curve of the horizontal well is 57.9-69.7μs / ft, and the central value is 63.7μs / ft, which is close to the central value of the P-wave time difference of the vertical well, indicating that the correction effect is good.

[0069] A P-wave time difference anisotropy correction system for highly deviated horizontal wells, comprising:

[0070] The inversion model building module is used to build an anisotropic inversion model of P-wave time difference based on the variation law of P-wave time difference with well inclination and mathematical methods;

[0071] Correction chart module, used to establish P-wave time difference correction charts under different well inclination angles and different P-wave anisotropy coefficients;

[0072] The interpretation model building module is used to select the P-wave time difference logging data of multiple wells in the same layer of the study area and establish the P-wave anisotropy coefficient logging interpretation model using the least squares method;

[0073] The P-wave time difference correction module is used to correct the P-wave time difference logging curve measured in the highly deviated horizontal well according to the P-wave anisotropy coefficient logging interpretation model and the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, so as to obtain the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy.

[0074] The method provided by the embodiment of the present invention constructs a P-wave time difference anisotropy inversion model based on the elliptic equation; establishes a P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients; uses the logging acoustic wave data of multiple wells in the same layer of the study area, and adopts the least square method to establish a P-wave anisotropy coefficient logging interpretation model; combines the P-wave time difference, natural gamma and well inclination logging curves measured in highly deviated horizontal wells to calculate the vertical and horizontal P-wave time differences that are not affected by anisotropy. The present invention has both theoretical basis and practical data. The objective law obtained by combining theory with practice has strong universality and high precision. It can be operated by general interpreters, is conducive to rapid large-scale application in production, and has good promotion value.

[0075] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatus.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells, characterized in that: The steps include: Based on the variation law of P-wave time difference with well inclination and mathematical method, an anisotropic inversion model of P-wave time difference is established; The P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients is established through the P-wave time difference anisotropy inversion model; The P-wave time-difference logging data of multiple wells in the same layer of the study area were selected, and the P-wave anisotropy coefficient logging interpretation model was established using the least squares method. According to the logging interpretation model of P-wave anisotropy coefficient and based on the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, the P-wave time difference logging curves measured in highly deviated horizontal wells are corrected to obtain the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy.

2. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 1, characterized in that: The P-wave time difference anisotropy inversion model is constructed using an elliptical model, and the specific process is as follows: The ellipse model equation is: The points on the ellipse satisfy the equation of the line in polar coordinates: y=ctg(θ)·x (2) By combining equations (1) and (2), we can get the P-wave time difference anisotropy inversion model when the well inclination angle is θ, which is expressed as: Where: AC θ is the longitudinal wave time difference when the well inclination angle is θ, in μs / ft; AC v is the vertical longitudinal wave time difference, in μs / ft; AC h is the horizontal longitudinal wave time difference, in μs / ft; θ is the well inclination angle, in degrees.

3. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 2, characterized in that: The P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients is established by simulating and analyzing the change law of P-wave time difference response under different well inclination angles and different P-wave anisotropy coefficients.

4. A method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 3, characterized in that: In the simulation analysis process, the well inclination angle θ changes from the vertical direction to the horizontal direction at a change interval of 5°, from 0°, 5°, 10°, ..., 90°; the P-wave anisotropy coefficient ε changes from 0, 0.05, 0.1, ..., 0.5 at a change interval of 0.05 to analyze the ratio of the P-wave time difference to the vertical P-wave time difference at different well inclination angles. The changing law of the P-wave time difference is obtained, thus establishing the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients.

5. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 4, characterized in that: The expression of the longitudinal wave anisotropy coefficient ε is: In the formula, AC v is the vertical longitudinal wave time difference, in μs / ft; AC h It is the time difference of longitudinal wave in horizontal direction, and its unit is μs / ft.

6. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 1, characterized in that: The P-wave anisotropy coefficient logging interpretation model uses the logging acoustic data of multiple wells in the same layer to establish the relationship between the P-wave anisotropy coefficient and the shale content. The specific process is as follows: Based on the same layer in the study area, the layer section corresponding to the target layer of the horizontal well is selected in the control well of the horizontal well to make the frequency histogram of the longitudinal wave time difference between the horizontal well and the control well, and obtain their respective peaks, including the horizontal longitudinal wave time difference AC h and the vertical longitudinal wave time difference AC v , and the volume content of mud in the control well V sh .

7. A method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 6, characterized in that: The volume content of mud in the control well is V sh The natural gamma logging curve is used to obtain the expression: Among them, V sh is the volume content of mud, in %; ΔGR is the relative value of natural potential; GR is the natural gamma logging value, GR min is the natural gamma value of the pure sandstone section, GR max is the natural gamma value of the pure mudstone section; GCUR is the Hilch coefficient.

8. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 7, characterized in that: The longitudinal wave anisotropy coefficient ε is used to establish the longitudinal wave anisotropy coefficient ε and the mud volume content V by the least square method. sh The statistical model relationship is expressed as: Where a and b are the fitting coefficients of the model.

9. The method for correcting anisotropy of P-wave time difference in highly deviated horizontal wells according to claim 1, characterized in that: Combining the P-wave time difference, natural gamma and well inclination logging curves measured in highly deviated / horizontal wells, according to the P-wave anisotropy coefficient logging interpretation model and based on the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, the vertical and horizontal P-wave time differences in highly deviated / horizontal wells that are not affected by anisotropy are calculated.

10. A P-wave anisotropy correction system for highly deviated horizontal wells, based on the P-wave anisotropy correction method for highly deviated horizontal wells according to any one of claims 1 to 9, characterized in that: include, The inversion model building module is used to build an anisotropic inversion model of P-wave time difference based on the variation law of P-wave time difference with well inclination and mathematical methods; Correction chart module, used to establish P-wave time difference correction charts under different well inclination angles and different P-wave anisotropy coefficients; The interpretation model building module is used to select the P-wave time difference logging data of multiple wells in the same layer of the study area and establish the P-wave anisotropy coefficient logging interpretation model using the least squares method; The P-wave time difference correction module is used to correct the P-wave time difference logging curve measured in the highly deviated horizontal well according to the P-wave anisotropy coefficient logging interpretation model and the P-wave time difference correction chart under different well inclination angles and different P-wave anisotropy coefficients, so as to obtain the P-wave time differences in the vertical and horizontal directions that are not affected by anisotropy.

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