A method for resistivity anisotropy correction of high deviation / horizontal well based on electrical imaging logging

Abstract

This invention discloses a method for correcting resistivity anisotropy in highly deviated / horizontal wells based on electrical imaging logging. To address the problem of significant differences in resistivity measurements between highly deviated / horizontal wells and vertical wells due to formation anisotropy, which affects reservoir evaluation accuracy, this invention proposes selecting adjacent vertical wells with available electrical imaging logging data within the area of ​​the highly deviated / horizontal well. First, quantitative calculation of formation electrical anisotropy is performed using the electrical imaging logging data. Then, based on the constraints of a three-dimensional geological structure model, a three-dimensional anisotropic attribute model of the area where the highly deviated / horizontal well is located is established. Next, anisotropic attribute values ​​along the well trajectory are extracted from the three-dimensional attribute model to construct the electrical anisotropy curve of the highly deviated / horizontal well. Finally, resistivity anisotropy correction is performed based on the resistivity anisotropy inversion model, calculating horizontal and vertical resistivity, providing fundamental parameters for the refined interpretation of logging data in highly deviated / horizontal wells.

Description

Technical Field

[0001] This invention relates to the field of reservoir evaluation technology, and in particular to a method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging. Background Technology

[0002] To significantly improve oil and gas production and recovery rates, future drilling will primarily focus on high-angle / horizontal wells. Due to variations in the logging environment and the influence of formation electrical anisotropy, resistivity responses differ across wells at different inclination angles for the same target formation. Resistivity measurements from horizontal wells are unlikely to accurately reflect the true resistivity of the formation and require anisotropy correction before application in production.

[0003] Currently, resistivity anisotropy correction for highly deviated / horizontal wells mainly employs rock physics experiments and statistical methods. The rock physics experiment method involves measuring vertical and horizontal resistivity through core experiments, calculating the electrical anisotropy coefficient of each core, and averaging the results for correction. However, due to limitations in the number of core samples, the rock physics experiment method struggles to accurately characterize the anisotropy coefficient along the wellbore trajectory of highly deviated / horizontal wells. The statistical method involves selecting a segment from the control well of the highly deviated / horizontal well corresponding to the target layer of the horizontal well, creating resistivity histograms for both the horizontal well and its control well, obtaining their respective peak values, and determining the correction coefficient using the ratio of the peak values ​​of the control well and the horizontal well, or establishing a fitting relationship using the peak values ​​of the control well and the horizontal well. The correction coefficient and the fitting relationship are then used for correction. Because the lithology and physical properties of unconventional oil and gas reservoirs vary rapidly laterally, and the angle between the well trajectory and the formation is constantly changing, simple statistical fitting for correction can introduce significant errors. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for correcting the resistivity anisotropy of large-angle / horizontal wells based on electrical imaging logging. This method effectively solves the problems caused by the influence of formation anisotropy, such as the large difference between the resistivity measurements of large-angle / horizontal wells and those of vertical wells, which affects the accuracy of reservoir evaluation.

[0005] This invention is achieved through the following technical solution:

[0006] A method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging, comprising:

[0007] S1, select adjacent vertical wells with electrical imaging logging data in the area of ​​high-angle / horizontal wells, and quantitatively calculate the formation electrical anisotropy coefficient.

[0008] S2. Based on the formation electrical anisotropy coefficient, a three-dimensional anisotropic property model of the area where the high-angle / horizontal well is located is established under the constraints of the three-dimensional geological structure model.

[0009] S3, extract the anisotropic attribute values ​​along the well trajectory in the three-dimensional anisotropic attribute model, and construct the electrical anisotropy curve of large-angle / horizontal wells;

[0010] S4. Based on the constructed electrical anisotropy curves of high-angle / horizontal wells, combined with the resistivity anisotropy inversion model, the resistivity anisotropy correction of high-angle / horizontal wells is performed using the apparent formation resistivity measured by high-angle / horizontal wells, and the horizontal and vertical resistivities unaffected by anisotropy are calculated.

[0011] Preferably, the specific process for quantitatively calculating the formation electrical anisotropy is as follows:

[0012] S11, Select static images from electrical imaging logging of a certain well section and form a data volume R with m rows × n columns, expressed as:

[0013] (1)

[0014] In the formula, m is the number of rows of resistivity data for a certain well section, and n is the number of each sampling point. This is electrical imaging data.

[0015] S12, considering the resistivity data of a certain well section m rows as composed of m parallel thin layers, based on the principle of resistivity series and parallel circuits, the vertical resistivity of the formation is composed of m thin layers connected in series, and the horizontal resistivity of the formation is composed of m thin layers connected in parallel. Their expressions are as follows:

[0016] ;

[0017] (2)

[0018] In the formula, Vertical resistivity of the formation, in Ω·m; The horizontal resistivity of the formation is expressed in Ω·m. For the first i Each thin layer occupies the volume of m thin layers. i It is a natural number greater than 0;

[0019] S13, through the vertical resistivity of the formation and formation horizontal resistivity Obtain the formation electrical anisotropy coefficient Its expression is:

[0020] (3)

[0021] In the formula, Vertical resistivity of the formation, in Ω·m. The horizontal resistivity of the formation is expressed in Ω·m.

[0022] Preferably, the formation electrical anisotropy is obtained by using static images from electrical imaging logging.

[0023] Preferably, the specific process of S2 is as follows:

[0024] By comparing stratigraphic data, a structural model of the top and bottom layers of the target area in the region where the high-angle / horizontal well is located is established. Combined with the formation electrical anisotropy coefficient calculated by electrical imaging logging of the adjacent vertical well, a three-dimensional electrical anisotropy property model is established.

[0025] Preferably, the process of establishing the top and bottom structural model of the target layer is as follows:

[0026] The stratigraphic correlation is based on marker beds as the main method and isoelastic correlation as a supplement. The stratigraphic division is determined by combining the trend of well logging curves to determine the top and bottom boundaries of the target layer, thereby establishing a structural model of the top and bottom of the target layer.

[0027] Preferably, the top and bottom structural model of the target layer is established using the Kriging mathematical method.

[0028] Preferably, the three-dimensional electrical anisotropy property model is established using a stochastic modeling method based on the variation function.

[0029] Preferably, the specific process for constructing the electrical anisotropy curve of a high-angle / horizontal well in S3 is as follows:

[0030] By combining the depth curve, inclination angle curve, and azimuth curve of a highly deviated / horizontal well, the wellbore trajectory of the highly deviated / horizontal well is plotted in a three-dimensional electrical anisotropy property model, and the electrical anisotropy property values ​​along the well trajectory are extracted, thereby constructing the electrical anisotropy curve of the highly deviated / horizontal well.

[0031] Preferably, the wellbore trajectory of the highly deviated / horizontal well is drawn using the minimum radius of curvature method.

[0032] Preferably, the specific process of S4 is as follows:

[0033] Based on the variation of resistivity with formation anisotropy and well inclination angle in the electrical anisotropy curve of high-angle / horizontal wells, the theoretical model of anisotropic resistivity is simplified to an elliptic equation, the expression of which is:

[0034] (4)

[0035] Points on the ellipse satisfy the equation of a straight line in polar coordinates:

[0036] (5)

[0037] By simultaneously solving the equations of the ellipse and the straight line in polar coordinates, the resistivity anisotropy inversion model for a well inclination angle of θ is obtained, and its expression is:

[0038] (6)

[0039] In the formula: The apparent formation resistivity is measured at a well inclination angle of θ, in Ω·m. Vertical resistivity, in Ω·m; θ represents the horizontal resistivity, in Ω·m; θ represents the well inclination angle, in °.

[0040] Compared with the prior art, the present invention has the following beneficial technical effects:

[0041] The purpose of this invention is to address the problem that the resistivity measurements of highly deviated / horizontal wells differ significantly from those of vertical wells due to formation anisotropy, affecting the accuracy of reservoir evaluation. The invention proposes selecting adjacent vertical wells with available electrical imaging logging data within the area of ​​highly deviated / horizontal wells. First, quantitative calculations of formation electrical anisotropy are performed using the electrical imaging logging data. Then, based on the constraints of a three-dimensional geological structure model, a three-dimensional anisotropic attribute model of the area where the highly deviated / horizontal well is located is established. Next, anisotropic attribute values ​​along the well trajectory are extracted from the three-dimensional attribute model to construct the electrical anisotropy curve of the highly deviated / horizontal well. Finally, resistivity anisotropy correction is performed based on the resistivity anisotropy inversion model, yielding horizontal and vertical resistivities unaffected by anisotropy. This provides fundamental parameters for the refined interpretation of logging data in highly deviated / horizontal wells. This invention provides a method for correcting resistivity anisotropy in highly deviated / horizontal wells based on electrical imaging logging. It effectively solves the problems of "difficulty in core sampling and limited experimental data," while also considering issues such as "well trajectory and lateral formation distribution variations." It has already achieved good application results in some regions. This invention has a rigorous theoretical foundation and clear physical meaning in its formulas. In practical applications, it combines logging data with theoretical models to solve for formation resistivity anisotropy coefficients, performing resistivity anisotropy correction in highly deviated / horizontal wells. The corrected horizontal resistivity shows good consistency with the resistivity of adjacent vertical wells, providing fundamental parameters for detailed logging interpretation of highly deviated / horizontal wells. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A flowchart of a method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging, provided in an embodiment of the present invention;

[0044] Figure 2This is a result image of the formation electrical anisotropy calculated by electrical imaging logging according to an embodiment of the present invention;

[0045] Figure 3 The three-dimensional electrical anisotropy property model provided in the embodiments of the present invention;

[0046] Figure 4 The electric anisotropy curves along the well trajectory are constructed in the three-dimensional model provided in the embodiments of the present invention;

[0047] Figure 5 This is a diagram showing the results of the resistivity anisotropy correction processing for high-angle / horizontal wells as described in an embodiment of the present invention.

[0048] Figure 6 This is a comparison diagram of the corrected horizontal resistivity and the resistivity of the adjacent vertical well, as described in an embodiment of the present invention. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention. Specific Implementation

[0052] See Figure 1 This invention provides a method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging, comprising the following steps:

[0053] Step 1: Select adjacent vertical wells with electrical imaging logging data in the area of ​​high-angle / horizontal wells, and perform quantitative calculation of formation electrical anisotropy based on static images from electrical imaging logging.

[0054] Select static images from electrical imaging logging of a certain well section and construct a data volume R with m rows × n columns, expressed as:

[0055] (1)

[0056] In the formula, m is the number of rows of resistivity data for a certain well section, and n is the number of each sampling point. This is electrical imaging data.

[0057] The resistivity data of a certain well section (m rows) can be considered as composed of m parallel thin layers. Based on the principle of series and parallel resistivity circuits, the vertical resistivity of the formation is composed of m thin layers connected in series, and the horizontal resistivity of the formation is composed of m thin layers connected in parallel. The expression is:

[0058] ; (2)

[0059] In the formula, The vertical resistivity of the formation is given in Ω·m. Formation horizontal resistivity, Ω·m; The volume of the i-th thin layer relative to the volume of m thin layers is expressed as a decimal.

[0060] Formation electrical anisotropy coefficient :

[0061] (3)

[0062] Figure 2 This document presents the results of quantitative calculations of formation electrical anisotropy using electrical imaging logging. The method involves programming the system to determine the number of data points and window length using the column count and sampling interval of the static curve matrix data from the control well's electrical imaging, thereby calculating the electrical imaging anisotropy coefficient λ. In the image, the resistivity data at the boundary between light and dark areas in the electrical imaging image differ significantly, indicating stronger formation anisotropy in that area. Consequently, the calculated electrical anisotropy value for this area is larger than that for well sections with uniform light and dark areas.

[0063] Step two involves stratigraphic correlation, using a combination of marker beds as the primary method and contour correlation as a secondary method, along with the trend of well logging curves, to determine the top and bottom boundaries of the target layer. A structural model of the top and bottom of the target layer is then established based on Kriging mathematics. Based on this structural model, electrical anisotropy is calculated using electrical imaging logging, and a three-dimensional anisotropic property model is established using a stochastic modeling method based on variograms. Figure 3 The three-dimensional electrical anisotropy property model is shown. The darkened area represents the wellbore trajectory of the horizontal well #Hwell. #A, #B, #C, and #D are four control wells near the horizontal well #Hwell with electrical imaging logging data. Based on the anisotropy of the four control wells, a three-dimensional electrical anisotropy property model of the #Hwell region was established. The gradient of color from dark gray to light gray represents the change of electrical anisotropy value from low to high. The dark area indicates relatively strong anisotropy.

[0064] Step 3: Combining the depth curve, inclination angle curve, and azimuth curve of the highly deviated / horizontal well, the wellbore trajectory is drawn using the minimum radius of curvature method. The electrical anisotropy attribute values ​​along the well trajectory are extracted from the 3D attribute model, and the electrical anisotropy curve of the highly deviated / horizontal well is constructed, such as... Figure 4As shown, the black curve along the well trajectory is the electrical anisotropy coefficient curve of a high-angle / horizontal well extracted and constructed from the three-dimensional attribute volume.

[0065] Step 4: Based on the variation of resistivity with formation anisotropy and well inclination angle, use the simplified elliptical model equation and the linear equation in polar coordinate system to perform resistivity anisotropy correction for high-angle / horizontal wells, and calculate the horizontal and vertical resistivity.

[0066] The equation for the elliptic model is:

[0067] (4)

[0068] Points on an ellipse satisfy the equation of a straight line in polar coordinates:

[0069] (5)

[0070] Combining equations (4) and (5), we can obtain the resistivity anisotropy inversion model when the well inclination angle is θ, and the expression is:

[0071] (6)

[0072] In the formula: The apparent formation resistivity, in Ω·m, is measured at a well inclination angle of θ. Vertical resistivity, Ω·m; θ represents the horizontal resistivity, in Ω·m; θ represents the well inclination angle, in °.

[0073] Figure 5 This is a diagram showing the results of resistivity anisotropy correction for high-angle / horizontal wells. The diagram shows the correction results for the horizontal section of the #Hwell horizontal well, which is the horizontal and vertical resistivity calculated by the inversion model. The correction amount is the difference between the measured resistivity of the horizontal well and the corrected horizontal resistivity. Figure 6 The graph shows the comparison between the corrected horizontal resistivity and the resistivity of adjacent control wells. Before correction, the peak resistivity of the horizontal well from the target point (A) to the final target point (B) on the normal distribution map was 24 Ω·m, while the peak resistivity of the corresponding oil layer section in the vertical well was 16.7 Ω·m, showing a certain difference. After correction, the peak horizontal resistivity of the horizontal well was 17 Ω·m, which is close to the peak resistivity of the vertical well, showing good consistency and demonstrating the feasibility of this method.

[0074] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging, characterized in that, include, S1, select adjacent vertical wells with electrical imaging logging data in the area of ​​high-angle / horizontal wells, and quantitatively calculate the formation electrical anisotropy coefficient. S2. Based on the formation electrical anisotropy coefficient, a three-dimensional anisotropic property model of the area where the high-angle / horizontal well is located is established under the constraints of the three-dimensional geological structure model. S3, extract the anisotropic attribute values ​​along the well trajectory in the three-dimensional anisotropic attribute model, and construct the electrical anisotropy curve of large-angle / horizontal wells; S4. Based on the constructed electrical anisotropy curve of the high-angle / horizontal well, combined with the resistivity anisotropy inversion model, the resistivity anisotropy of the high-angle / horizontal well is corrected by using the well inclination angle of the high-angle / horizontal well and the apparent formation resistivity corresponding to the measured well inclination angle, so as to obtain the horizontal resistivity and vertical resistivity that are not affected by anisotropy.

2. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that, The specific process for quantitatively calculating the formation electrical anisotropy coefficient is as follows: S11, Select static images from electrical imaging logging of a certain well section and form a data volume R with m rows × n columns, expressed as: （1） In the formula, m is the number of rows of resistivity data for a certain well section, and n is the number of each sampling point. For electrical imaging data; S12, considering the resistivity data of a certain well section m rows as composed of m parallel thin layers, based on the principle of resistivity series and parallel circuits, the vertical resistivity of the formation is composed of m thin layers connected in series, and the horizontal resistivity of the formation is composed of m thin layers connected in parallel. Their expressions are as follows: ； （2） In the formula, Vertical resistivity of the formation, in Ω·m; The horizontal resistivity of the formation is expressed in Ω·m. For the first i Each thin layer occupies the volume of m thin layers. i It is a natural number greater than 0; S13, through the vertical resistivity of the formation and formation horizontal resistivity Obtain the formation electrical anisotropy coefficient Its expression is: （3） In the formula, Vertical resistivity of the formation, in Ω·m. The horizontal resistivity of the formation is expressed in Ω·m.

3. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that, The formation electrical anisotropy was obtained using static images from electrical imaging logging.

4. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that, The specific process of S2 is as follows: By comparing stratigraphic data, a structural model of the top and bottom layers of the target area in the region of highly deviated / horizontal wells is established. Combined with the formation electrical anisotropy coefficients calculated by electrical imaging logging of adjacent vertical wells, a three-dimensional electrical anisotropy property model is established.

5. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 4, characterized in that, The specific process for establishing the top and bottom structural model of the target layer is as follows: The stratigraphic correlation is based on marker beds as the main method and isoelastic correlation as a supplement. The stratigraphic division is determined by combining the trend of well logging curves to determine the top and bottom boundaries of the target layer, thereby establishing a structural model of the top and bottom of the target layer.

6. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 4, characterized in that, The top and bottom structural model of the target layer was established using Kriging mathematics.

7. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 4, characterized in that, The three-dimensional electrical anisotropy property model is established using a stochastic modeling method based on the variation function.

8. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that, The specific process for constructing electrical anisotropy curves for high-angle / horizontal wells in S3 is as follows: By combining the depth curve, inclination angle curve, and azimuth curve of a highly deviated / horizontal well, the wellbore trajectory of the highly deviated / horizontal well is plotted in a three-dimensional electrical anisotropy property model, and the electrical anisotropy property values ​​along the well trajectory are extracted, thereby constructing the electrical anisotropy curve of the highly deviated / horizontal well.

9. A method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 8, characterized in that, The wellbore trajectory of the highly deviated / horizontal wells was drawn using the minimum radius of curvature method.

10. The method for correcting resistivity anisotropy in high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that, The specific process of S4 is as follows: Based on the variation of resistivity with formation anisotropy and well inclination angle in the electrical anisotropy curve of high-angle / horizontal wells, the theoretical model of anisotropic resistivity is simplified to an elliptic equation, the expression of which is: （4） Points on the ellipse satisfy the equation of a straight line in polar coordinates: （5） By simultaneously solving the equations of the ellipse and the straight line in polar coordinates, the resistivity anisotropy inversion model for a well inclination angle of θ is obtained, and its expression is: （6） In the formula: The apparent formation resistivity is measured at a well inclination angle of θ, in Ω·m. Vertical resistivity, in Ω·m; θ represents the horizontal resistivity, in Ω·m; θ represents the well inclination angle, in °.

Images