High-inclination / horizontal well resistivity anisotropy correction method based on electrical imaging logging

Abstract

The invention discloses a high-inclination / horizontal well resistivity anisotropy correction method based on electric imaging logging, and aims to solve the problems that due to the influence of formation anisotropy, the difference between a high-inclination / horizontal well resistivity measurement value and a vertical well is large, and the reservoir evaluation precision is influenced. The method comprises the following steps: selecting an adjacent vertical well with electric imaging logging information in a region where a high-inclination / horizontal well is located, performing stratum electric anisotropy quantitative calculation by utilizing the electric imaging logging information, and then establishing a three-dimensional anisotropic attribute model of the region where the high-inclination / horizontal well is located on the basis of a three-dimensional geologic structure model constraint; the method comprises the steps that firstly, a three-dimensional attribute model is established, anisotropy attribute values in the three-dimensional attribute model along a well trajectory are extracted, a high-inclination / horizontal well electric anisotropy curve is established, finally, high-inclination / horizontal well resistivity anisotropy correction is conducted based on a resistivity anisotropy inversion model, horizontal resistivity and vertical resistivity are calculated, and basic parameters are provided for well logging fine interpretation of a high-inclination / horizontal well.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir evaluation, and in particular to a resistivity anisotropy correction method for a highly deviated / horizontal well based on electrical imaging logging. Background Art

[0002] In order to significantly increase the productivity and recovery rate of oil and gas single wells, the future drilling types will mainly be high-angle / horizontal wells. Due to changes in the logging environment and the influence of the electrical anisotropy of the formation, the resistivity response of the same target layer at different well inclination angles is different. The resistivity measured by the horizontal well is difficult to reflect the true resistivity of the formation and needs to be anisotropically corrected before it can be used in production.

[0003] At present, the main methods for resistivity anisotropy correction of highly deviated / horizontal wells are rock physics experimental method and statistical method. The rock physics experimental method is to measure the vertical and horizontal resistivity through core experiments, calculate the electrical anisotropy coefficient of each core, and take the average value for correction. Due to the limitation of the number of cores, it is difficult for the rock physics experimental method to accurately characterize the anisotropy coefficient along the wellbore trajectory of highly deviated / horizontal wells. The statistical method is to select the layer section corresponding to the target layer of the horizontal well from the control well of the highly deviated / horizontal well to make the resistivity histogram of the horizontal well and its control well respectively, obtain their respective peak values, determine the correction coefficient by the peak ratio of the control well and the horizontal well, or establish a fitting relationship by using the peak values ​​of the control well and the horizontal well, so as to use the correction coefficient and the fitting relationship for correction. Since the lithology, physical properties and other attributes of unconventional oil and gas reservoirs change rapidly in the lateral distribution, and the angle between the well trajectory and the formation is constantly changing, simple statistical fitting for correction will result in large errors. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a resistivity anisotropy correction method for highly inclined / horizontal wells based on electrical imaging logging, which effectively solves the problems of large differences in resistivity measurement values ​​of highly inclined / horizontal wells and vertical wells due to the influence of formation anisotropy, affecting the accuracy of reservoir evaluation, etc.

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

[0006] A method for correcting resistivity anisotropy of a highly deviated / horizontal well based on electrical imaging logging, comprising:

[0007] S1, select adjacent vertical wells with electrical imaging logging data in the area where the highly deviated / horizontal wells are located, and quantitatively calculate the formation electrical anisotropy to obtain the formation electrical anisotropy coefficient;

[0008] S2, based on the formation electrical anisotropy coefficient, a three-dimensional anisotropic attribute model of the area where the high-angle / horizontal wells are located is established on the basis of the constraints of the three-dimensional geological structure model;

[0009] S3, extracting the anisotropic property values ​​along the well trajectory in the three-dimensional anisotropic property model and constructing the electrical anisotropy curve of the highly deviated / horizontal well;

[0010] S4, based on the constructed electrical anisotropy curve of highly deviated / horizontal wells, combined with the resistivity anisotropy inversion model, uses the apparent formation resistivity measured in highly deviated / horizontal wells to perform resistivity anisotropy correction for highly deviated / horizontal wells, and calculates the horizontal resistivity and vertical resistivity that are not affected by anisotropy.

[0011] Preferably, the specific process of quantitatively calculating the formation electrical anisotropy is:

[0012] S11, select the static image of the electrical imaging logging of a certain section in the highly deviated / horizontal well to form a data volume R with m rows and n columns, which is expressed as:

[0013]

[0014] Where m is the number of rows of resistivity data in a certain well section, n is the number of each sampling point, R ij For electrical imaging data.

[0015] S12, consider the m lines of resistivity data of a well section as 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 in series, and the horizontal resistivity of the formation is composed of m thin layers in parallel. Their expressions are:

[0016]

[0017]

[0018] In the formula, R v is the vertical resistivity of the formation, in Ω.m; R h is the horizontal resistivity of the formation, in Ω.m; v i is the volume of m thin layers occupied by the i-th thin layer, i is a natural number greater than 0;

[0019] S13, through the vertical resistivity R v and the horizontal resistivity R h , the formation electrical anisotropy coefficient λ is obtained, and its expression is:

[0020]

[0021] In the formula, R v is the vertical resistivity of the formation, in Ω.m, R h The horizontal resistivity of the formation, in Ω.m.

[0022] Preferably, the formation electrical anisotropy is obtained by obtaining static images based on electrical imaging logging.

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

[0024] Through stratigraphic comparison, the top and bottom structural models of the target area where the highly deviated / horizontal wells are located are established, and the three-dimensional electrical anisotropy attribute model is established by combining the formation electrical anisotropy coefficient calculated by electrical imaging logging of adjacent vertical wells;

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

[0026] The stratigraphic comparison adopts the marker layer as the main method and the equal elevation comparison division as the auxiliary method, and combines the change trend of the logging curve to perform stratigraphic division to determine the top and bottom boundaries of the target layer, so as to establish the top and bottom structural model 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 of variogram.

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

[0030] Combined with the depth curve, inclination angle curve and azimuth curve of the highly deviated / horizontal well, the wellbore trajectory of the highly deviated / horizontal well is drawn in the three-dimensional electrical anisotropy attribute model, and the electrical anisotropy attribute values ​​along the well trajectory are extracted to construct the electrical anisotropy curve of the highly deviated / horizontal well.

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

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

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

[0034]

[0035] Among them, the points on the ellipse satisfy the equation of the line in the polar coordinate system:

[0036] y=ctg(θ)·x (5)

[0037] By combining the elliptic equation and the linear equation in the polar coordinate system, the resistivity anisotropy inversion model when the well inclination angle is θ is obtained, and its expression is:

[0038]

[0039] Where: Rt θ is the apparent formation resistivity measured when the well inclination angle is θ, in Ω.m; R v is the vertical resistivity, in Ω.m; R h is the horizontal resistivity, Ω.m; θ is the well inclination, in degrees.

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

[0041] The purpose of the present invention is to solve the problems that the resistivity measurement value of highly deviated / horizontal wells is greatly different from that of vertical wells due to the influence of formation anisotropy, which affects the accuracy of reservoir evaluation. It is proposed to select adjacent vertical wells with electrical imaging logging data in the area where the highly deviated / horizontal wells are located, use the electrical imaging logging data to first perform quantitative calculation of formation electrical anisotropy, then establish a three-dimensional anisotropic attribute model of the area where the highly deviated / horizontal wells are located based on the constraints of the three-dimensional geological structure model, then extract the anisotropic attribute values ​​along the well trajectory in the three-dimensional attribute model, construct the electrical anisotropy curve of the highly deviated / horizontal wells, and finally perform resistivity anisotropy correction of the highly deviated / horizontal wells based on the resistivity anisotropy inversion model, obtain the horizontal resistivity and vertical resistivity that are not affected by anisotropy, and provide basic parameters for the fine logging interpretation of the highly deviated / horizontal wells. The present invention provides a method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging, which effectively solves the problem of "difficulty in coring and lack of experimental data", while also considering the problem of "well trajectory and lateral distribution change of formation", and has achieved good application results in some regional tests. The present invention has a rigorous theoretical basis and a clear physical meaning of the formula. In practical applications, the well logging data is combined with the theoretical model to solve the anisotropy coefficient of the formation resistivity, and the resistivity anisotropy of highly deviated / horizontal wells is corrected. The corrected horizontal resistivity has a good consistency with the resistivity of the adjacent vertical well, providing basic parameters for the fine interpretation of logging of highly deviated / horizontal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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.

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

[0044] Figure 2A result diagram of the electrical anisotropy calculation of the formation by electrical imaging logging provided in an embodiment of the present invention;

[0045] Figure 3 A three-dimensional electrical anisotropy property model provided by an embodiment of the present invention;

[0046] Figure 4 Constructing an electrical anisotropy curve graph along the well trajectory in the three-dimensional model provided by the embodiment of the present invention;

[0047] Figure 5 This is a result diagram of resistivity anisotropy correction processing for highly deviated / horizontal wells according to 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 wells described in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] 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.

[0050] 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. Specific embodiments

[0052] See also Figure 1 The embodiment of the present invention provides a method for correcting resistivity anisotropy of a highly deviated / horizontal well based on electrical imaging logging, comprising the following steps:

[0053] Step 1: Select adjacent vertical wells with electrical imaging logging data in the area where the highly deviated / horizontal wells are located, and perform quantitative calculation of formation electrical anisotropy based on static images of electrical imaging logging.

[0054] Select the static image of electrical imaging logging of a certain well section to form a data volume R with m rows and n columns, which is expressed as:

[0055]

[0056] Where m is the number of rows of resistivity data in a certain well section, n is the number of each sampling point, R ij For electrical imaging data.

[0057] The m lines of resistivity data in a well section can be regarded 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 in series, and the horizontal resistivity of the formation is composed of m thin layers in parallel. The expression is:

[0058]

[0059] In the formula, R v is the vertical resistivity of the formation, Ω.m; R h Horizontal resistivity of formation, Ω.m; v i is the volume of the i-th thin layer occupied by m thin layers, a decimal.

[0060] Formation electrical anisotropy coefficient λ:

[0061]

[0062] Figure 2 The result diagram of the quantitative calculation of the electrical anisotropy of the formation by electrical imaging logging is realized by writing a program. The number of columns and sampling interval of the static curve matrix data of the electrical imaging of the control well are used to determine the number of points and the window length, and the electrical imaging anisotropy coefficient λ is calculated. The resistivity data of the depth section corresponding to the light and dark boundary of the electrical imaging image in the figure are quite different, which means that the formation anisotropy of this section is strong. Correspondingly, the electrical anisotropy value calculated in this section is larger than the electrical anisotropy value of the light and dark uniform well section.

[0063] Step 2: Through stratigraphic comparison, the stratigraphic division is carried out by using the marker layer as the main and the equal elevation comparison division as the auxiliary combined with the change trend of the logging curve to determine the top and bottom boundaries of the target layer, and the top and bottom structural model of the target layer is established based on the Kriging mathematical method. On the basis of the structural model, the electrical anisotropy is calculated based on the electrical imaging logging, and the three-dimensional anisotropic attribute model is established using the random modeling method of the variogram. Figure 3 It is a three-dimensional electrical anisotropy attribute model. The oblique line deepening area is the wellbore trajectory of the horizontal well #Hwell. #A, #B, #C, and #D are the four control wells with electrical imaging logging data near the horizontal well #Hwell. Based on the anisotropy of the four control wells, a three-dimensional electrical anisotropy attribute model of the #Hwell area was established. The gradient from dark gray to light color represents the change of electrical anisotropy value from low to high. The dark area indicates that the anisotropy is relatively strong.

[0064] Step 3: Combine the depth curve, well inclination curve and azimuth curve of the highly deviated / horizontal well and use the minimum curvature radius method to draw the wellbore trajectory. Extract the electrical anisotropy attribute value along the well trajectory in the three-dimensional attribute model to construct the electrical anisotropy curve of the highly deviated / horizontal well, such as Figure 4 As shown in FIG. 1 , the black curve along the well trajectory is the electrical anisotropy coefficient curve of the high-angle / horizontal well extracted and constructed by the three-dimensional attribute body.

[0065] Step 4: According to the variation law of resistivity with formation anisotropy and well inclination, the simplified elliptical model equation and the straight line equation in the polar coordinate system are used to perform resistivity anisotropy correction for high-angle / horizontal wells and calculate horizontal and vertical resistivities.

[0066] The ellipse model equation is:

[0067]

[0068] The points on the ellipse satisfy the equation of the line in polar coordinates:

[0069] y=ctg(θ)·x (5)

[0070] By combining equations (4) and (5), we can get the resistivity anisotropy inversion model when the well inclination angle is θ, which is expressed as:

[0071]

[0072] Where: Rt θ is the apparent formation resistivity measured when the well inclination angle is θ, Ω.m; R v is the vertical resistivity, Ω.m; R h is the horizontal resistivity, Ω.m; θ is the well inclination, °.

[0073] Figure 5 This is the result of the resistivity anisotropy correction processing of the high-angle / horizontal well. The figure shows the correction result of the horizontal section of the horizontal well #Hwell, that is, the horizontal and vertical resistivities 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 This is a graph showing the contrast between the corrected horizontal resistivity and the resistivity of the adjacent control well. Before correction, the resistivity peak value from the horizontal well entry point (A) to the final target point (B) on the normal distribution graph is 24Ω.m, and the corresponding resistivity peak value of the vertical well oil layer section is 16.7Ω.m, which is a certain difference. After correction, the horizontal resistivity peak value of the horizontal well is 17Ω.m, which is close to the resistivity peak value of the vertical well, and has good consistency, indicating the feasibility of this method.

[0074] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

[0075] 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 resistivity anisotropy in highly deviated / horizontal wells based on electrical imaging logging, characterized in that: include, S1, select adjacent vertical wells with electrical imaging logging data in the area where the highly deviated / horizontal wells are located, and quantitatively calculate the formation electrical anisotropy to obtain the formation electrical anisotropy coefficient; S2, based on the formation electrical anisotropy coefficient, a three-dimensional anisotropic attribute model of the area where the high-angle / horizontal wells are located is established on the basis of the constraints of the three-dimensional geological structure model; S3, extracting the anisotropic property values ​​along the well trajectory in the three-dimensional anisotropic property model and constructing the electrical anisotropy curve of the highly deviated / horizontal well; S4, based on the constructed electrical anisotropy curve of highly deviated / horizontal wells, combined with the resistivity anisotropy inversion model, uses the apparent formation resistivity measured in highly deviated / horizontal wells to perform resistivity anisotropy correction for highly deviated / horizontal wells, and obtains horizontal resistivity and vertical resistivity that are not affected by anisotropy.

2. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 1, characterized in that: The quantitative calculation of the formation electrical anisotropy to obtain the formation electrical anisotropy coefficient is specifically carried out as follows: S11, select the static image of the electrical imaging logging of a certain section in the highly deviated / horizontal well to form a data volume R with m rows and n columns, which is expressed as: Where m is the number of rows of resistivity data in a certain well section, n is the number of each sampling point, R ij For electrical imaging data; S12, consider the m lines of resistivity data of a well section as 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 in series, and the horizontal resistivity of the formation is composed of m thin layers in parallel. Their expressions are: In the formula, R v is the vertical resistivity of the formation, in Ω.m; R h is the horizontal resistivity of the formation, in Ω.m; v i is the volume of m thin layers occupied by the i-th thin layer, i is a natural number greater than 0; S13, through the vertical resistivity R v and the horizontal resistivity R h , the formation electrical anisotropy coefficient λ is obtained, and its expression is: In the formula, R v is the vertical resistivity of the formation, in Ω.m, R h The horizontal resistivity of the formation, in Ω.m.

3. The resistivity anisotropy correction method for high-angle / horizontal wells based on electrical imaging logging according to claim 1, characterized in that: The formation electrical anisotropy is obtained through static images based on electrical imaging logging.

4. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 1, characterized in that: The specific process of S2 is: Through stratigraphic comparison, the top and bottom structural models of the target areas where highly deviated / horizontal wells are located are established, and a three-dimensional electrical anisotropy attribute model is established by combining the formation electrical anisotropy coefficient calculated by electrical imaging logging of adjacent vertical wells.

5. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 4, characterized in that: The process of establishing the top and bottom structural model of the target layer is specifically as follows: The stratigraphic comparison adopts the marker layer as the main method and the equal elevation comparison division as the auxiliary method, and combines the change trend of the logging curve to perform stratigraphic division to determine the top and bottom boundaries of the target layer, so as to establish the top and bottom structural model of the target layer.

6. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 4, characterized in that: The top and bottom structural model of the target layer is established by using the Kriging mathematical method.

7. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 4, characterized in that: The three-dimensional electrical anisotropy property model is established by adopting a stochastic modeling method of variogram.

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

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

10. The method for correcting resistivity anisotropy of highly deviated / horizontal wells based on electrical imaging logging according to claim 1, characterized in that: The specific process of S4 is: According to the variation law of resistivity in the electrical anisotropy curve of high-angle / horizontal wells with formation anisotropy and well inclination, the anisotropic resistivity theoretical model is simplified to an elliptic equation, which is expressed as follows: Among them, the points on the ellipse satisfy the equation of the line in the polar coordinate system: y=ctg(θ)·x (5) By combining the elliptic equation and the linear equation in the polar coordinate system, the resistivity anisotropy inversion model when the well inclination angle is θ is obtained, and its expression is: Where: Rt θ is the apparent formation resistivity measured when the well inclination angle is θ, in Ω.m; R v is the vertical resistivity, in Ω.m; R h is the horizontal resistivity, in Ω.m; θ is the well inclination, in degrees.

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