A method for accurately recovering a resource exploration drilling trajectory

Abstract

This application relates to a calculation method for accurate recovery of borehole trajectory in resource exploration, comprising: S1, establishing an original data file; S2, determining the initial boundary conditions for azimuth and zenith angle based on the original data file; S3, using mathematical algorithms to fit curves of azimuth and zenith angle as a function of drilling depth H throughout the well section, based on borehole inclination measurement data from well logging and the initial boundary conditions; S4, converting the fitted curves into dense point discrete data; S5, accurately recovering the entire borehole trajectory using an integral method; according to resource exploration requirements, the spatial position of the drilling depth corresponding to a certain interface is obtained using an integral method, thereby achieving a higher accuracy calculation than the conventional borehole inclination correction method; this application features a simple method that is easy to program and implement, simple operation, and the ability to visualize three-dimensional trajectory; the more complex the borehole trajectory, the higher its accuracy compared to the traditional piecewise linear method.

Description

Technical Field

[0001] This application relates to the technical field of resource exploration boreholes, and in particular to a calculation method for accurate recovery of resource exploration borehole trajectories. Background Technology

[0002] Resource exploration boreholes are cylindrical holes with small diameters and depths of hundreds or even thousands of meters, drilled into the ground using drilling equipment. During resource exploration operations, borehole deviation often occurs. Although this is a common phenomenon, due to insufficient accuracy in borehole deviation data calculation and the inability to accurately reconstruct the borehole trajectory, significant deviations can greatly affect the borehole rating and even result in abandoned boreholes.

[0003] The causes of deviation during drilling include factors such as lithology, drilling equipment performance, and drilling operations. Firstly, the anisotropy of the rock generates a tilting moment at the drill bit, causing the large-diameter drill string to tilt and resulting in borehole deviation. Secondly, when drilling through soft and hard interlayers, a pressure difference occurs at the drill bit, or the drill bit slips along rock joints. Thirdly, encountering karst caves or large fissures during drilling. Fourthly, drilling through gravel layers. Reasons related to drilling technology and operations include: changing diameters without guidance or the large-diameter drill string itself being bent; excessive flushing fluid scouring the borehole wall, causing excessive clearance and resulting in a deflection angle between the large-diameter drill string or core tube and the borehole axis; excessive drilling pressure and excessively high rotation speed cause the drill string to bend under axial pressure and rotation, affecting the stability of the drill string and causing the large-diameter drill string to tilt.

[0004] Deflection causes the borehole trajectory to change from the designed vertical straight line to a curved spatial curve, manifesting as significant deviations in the zenith and azimuth angles at certain depths, in most well sections, and even throughout the entire well section from the design. This phenomenon is generally called borehole deviation. Significant borehole deviation or problems in advanced exploration stages necessitate correction. Currently, the most common method used by exploration units is to calculate and correct deviations based on borehole deviation measurement data from well logging using a broken-line method. This method is complex, lacks accuracy, and is prone to human error during the calculation and table filling process. It is necessary to propose a more accurate and adaptable borehole deviation correction method.

[0005] However, to accurately determine the degree of borehole deviation during exploration, it is necessary to obtain the accurate spatial trajectory of the borehole. The usual practice is to measure borehole deviation data at regular intervals during drilling, such as 50m or 25m. This data includes the zenith angle, azimuth angle, and depth. Based on these fundamental elements—zenith angle, azimuth angle, and depth—the spatial coordinates of each measuring point are calculated using a piecewise linear method. For the stratigraphic interface between two measuring points, linear interpolation is used for calculation.

[0006] Previous studies on borehole inclination correction have been numerous, but they have mostly followed the principle of piecewise progressive calculation using the polyline method. These methods generally focus only on calculating the spatial coordinates of a few layers relevant to the exploration mission. While some have achieved automated calculations, they haven't eliminated the errors introduced by the polyline method. Even with local (mostly resource-bound) densification during field logging, systematic errors before the densified section cannot be eliminated. These methods all suffer from limited, fixed known data and lack a logical approach to mathematically increasing the calculated data, thus failing to achieve accurate drilling trajectory recovery. Therefore, piecewise progressive calculations using limited data inevitably contain errors due to the limited number of measurement points. Furthermore, calculating more layers requires manual work such as identifying or indicating the polyline segment location of each layer.

[0007] Borehole deviation is a common phenomenon in resource drilling, and accurate reconstruction of the borehole's spatial trajectory is necessary to achieve deviation correction. Currently, the mathematical expression of borehole deviation is based on finite discrete measurements of azimuth, zenith angle, and well depth from well logging results. Previous methods to improve the accuracy of deviation calculations have focused on increasing the density of measuring points, but this typically only applies to the resource layer, leaving the upper layers still controlled by a sparser density of measuring points. Therefore, it is currently necessary to develop a more accurate and adaptable borehole deviation correction method. Summary of the Invention

[0008] In order to propose a more accurate and adaptable borehole inclination correction method, this application provides a calculation method for accurate recovery of borehole trajectory in resource exploration.

[0009] The calculation method for accurate recovery of borehole trajectories in resource exploration provided in this application adopts the following technical solution: A calculation method for accurate recovery of borehole trajectories in resource exploration includes: S1. Establish raw data files: Raw data includes the borehole coordinates and elevation of the exploration borehole, and borehole inclination measurement data obtained from well logging; Borehole inclination measurement data includes zenith angle and azimuth angle data corresponding to the drilling depth at intervals; S2. Based on the original data file, determine the initial boundary conditions for the azimuth and zenith angles; the initial value of the azimuth angle can be extended to the wellhead according to the trend of the scatter curve, and the initial value of the zenith angle is set to 0. S3. Based on the borehole inclination measurement data and the determined initial boundary conditions, various calculation methods can be selected, including linear interpolation, spline curve interpolation, polynomial fitting interpolation, and parabolic interpolation, to achieve the purpose of fitting the curves of azimuth and zenith angle as a function of drilling depth H. S4. Convert the fitted curve into dense discrete data: perform dense sampling on the fitted curve; dense sampling interval. The available parameters are 1, 2, and 5 m. The principle for selection is that the more complex the logging curve and the higher the required calculation accuracy, the smaller the selected dense sampling interval should be; 2 m is generally sufficient to accurately recover the actual borehole trajectory, and the default is 2 m.

[0010] S5. Determine the drilling trajectory: Starting from the wellhead, at the i-th well depth interval... Horizontal projection length It can be obtained from the following formula: ; the i-th well depth interval vertical projection length It can be obtained from the following formula: ; the i-th well depth interval The geographic coordinate increment corresponding to the horizontal projection and It can be obtained from the following formula: ,in Zenith angle, It is the azimuth angle; Let the elevation and coordinates of the borehole opening be respectively... Then the spatial coordinates and elevation of the end point of the Mth segment of the borehole Calculated using the following formulas respectively: After calculating M=1 using the above formula until the number of samples corresponding to the maximum well depth is reached, the actual borehole trajectory can be obtained.

[0011] By adopting the above technical solution, a continuous curve with the required accuracy can be obtained from limited well logging borehole inclination data, i.e. These two curves can accurately represent the borehole trajectory. This approach solves the problem of insufficient data sources when previous researchers were reconstructing borehole trajectories. It also reduces the inefficiency and potential borehole accidents caused by repeatedly logging with multiple sampling intervals in current practical logging work in order to improve accuracy.

[0012] For any stratigraphic interface at a known depth, this method can automatically calculate its location under the premise of dense sampling interval. Specifically, when the stratigraphic interface is located between the Mth and M+1th sampling points, after completing the calculation of segment M, the coordinate and elevation increments within segment M+1 are accumulated. The elevation increment is set accordingly. Calculated by the following formula: .

[0013] By adopting the above technical solutions, the problem of insufficient computational data sources can be solved, thereby improving computational accuracy; at the same time, spatial coordinates at any well depth can be calculated, laying a solid foundation for digital modeling of mines.

[0014] In step S4 when By selecting 1, 2, and 5 meters and performing the calculations in step S5, the calculation accuracy is significantly higher than that of traditional methods, and under normal circumstances, it can accurately recover the actual borehole trajectory.

[0015] The calculation method for accurate recovery of borehole trajectory in resource exploration according to claim 2 is characterized in that: the dense point sampling interval in step S4 is... The optional parameters include 1, 2, and 5m. After selecting the dense sampling interval, the calculation in step S5 is performed. The smaller the dense sampling interval, the better the drilling trajectory recovery effect, that is, the higher the accuracy. Setting the dense sampling interval to the default 2m can generally achieve the purpose of accurately recovering the actual drilling trajectory.

[0016] Through calculation and analysis using multiple models, and setting the sampling interval of the fitted dense points to 2m, the accuracy of borehole trajectory recovery can be met in most cases.

[0017] In summary, this application includes at least one of the following beneficial technical effects: By fitting discrete curves relating zenith angle, azimuth angle, and borehole depth using various mathematical curve fitting algorithms, continuous curves of azimuth angle and zenith angle with borehole depth can be obtained. These curves can be regarded as the true continuous curves of azimuth angle and zenith angle with borehole depth. By sampling dense points on the obtained curves and then using an integral algorithm for calculation, the accurate recovery of the borehole trajectory can be achieved. Programming using this method offers a clear approach, is simple to implement, and can achieve interactive input of raw data, automatic output of calculation result tables, and the generation of 3D stereoscopic display and planar profile projection of borehole trajectories. Furthermore, this method improves the calculation process, increases work efficiency and result accuracy, and avoids the errors that easily arise from manual table filling and selection steps in previous methods. Using the calculation method of this application, the spatial coordinates of any specified layer within the borehole can be obtained. The calculated spatial coordinates of any layer can be directly used to compile the planar results map of that layer. Furthermore, based on the accurate restoration of the borehole trajectory, borehole projection onto any geological profile with arbitrary strike can also be achieved. The accurately restored borehole trajectory is also one of the important basic data for digital mines. All of these can be implemented through programming. Attached Figure Description

[0018] Figure 1 The azimuth angles are for the two theoretical models; Figure 2 The zenith angle curves for the two theoretical models; Figure 3 The horizontal projection of the borehole trajectory in Theory 2; Figure 4A comparison is made between the horizontal projection of the borehole trajectory calculated by the traditional broken line method and the borehole trajectory of the theoretical model under different inclination point intervals (50, 20, 10, 5m). Figure 5 The horizontal projection of the borehole trajectory calculated by parabolic interpolation and traditional broken line method is compared with the horizontal projection of the borehole trajectory in the theoretical model when the interval between inclinometer points is 50m. Figure 6 The horizontal projection of the borehole trajectory calculated by parabolic interpolation and traditional broken line method is compared with the horizontal projection of the borehole trajectory in the theoretical model when the interval between inclinometer points is 20m. Figure 7 For the theoretical model, inclinometer points were sampled at 50m intervals. In the resource section, the inclinometer points were densified to 20m and 10m, and the horizontal projection of the borehole trajectory was calculated using the traditional broken line method. Figure 8 For the theoretical model, inclinometer points were sampled at 20m intervals. When the inclinometer points were densified to 10m in the resource section, the horizontal projection of the borehole trajectory was calculated using the traditional broken line method. Figure 9 This is a schematic diagram comparing the complexity of the borehole inclination parameter curve of the theoretical model with that of the actual well logging curve. Figure 10 This is a schematic diagram illustrating the determination of the initial value of the azimuth angle. Figure 11 This is a schematic diagram of various projections and increments for the i-th segment. Detailed Implementation

[0019] The following is in conjunction with the appendix Figure 1-11 This application will be described in further detail.

[0020] This application discloses a calculation method for accurate recovery of borehole trajectories in resource exploration.

[0021] A calculation method for accurate recovery of borehole trajectories in resource exploration includes: establishing an original data file; the data basis for this calculation method is the borehole inclination measurement data from well logging (the correspondence between zenith angle and azimuth angle and observation depth. Local densification measurement and corresponding data are not required when the observation interval does not exceed 20m) and the borehole head coordinates and elevation; the drilling depth corresponding to the interface (or other target) of engineering concern (compiling the result map).

[0022] First, determine the azimuth angle based on the discrete curve of the initial well logging data. and zenith The boundary conditions (initial values) are as follows: the initial value of the zenith angle is always 0; the initial value of the azimuth angle can be determined by reasonably extending the measured curve along the trend to the wellhead.

[0023] Based on well logging and inclination data, mathematical interpolation methods are selected, such as linear interpolation, spline curve interpolation, polynomial fitting interpolation, and parabolic interpolation. These methods all have mature mathematical formulas and algorithms. The azimuth angle is then fitted. and zenith As drilling depth The curve of change, that is, a continuous curve with acceptable accuracy that can be obtained from limited well logging borehole inclination data, i.e. These two curves can accurately represent the borehole trajectory. This approach solves the problem of insufficient data sources when previous researchers were reconstructing borehole trajectories. It also reduces the inefficiency and potential borehole accidents caused by repeated logging at multiple sampling intervals in current practical logging work in order to improve accuracy.

[0024] The continuous curve is converted into discrete data through dense sampling. Based on the accuracy requirements, resampling of the fitted curve is selected, with the dense sampling interval set to [value missing]. The resampling interval for the fitted curve is selected, such as 1m, 2m, 5m, 10m, etc. Through calculations using theoretical models and actual well logging data, and comprehensive analysis, Not greater than The accuracy requirements under normal circumstances can be met; It can meet the accuracy requirements in more complex situations. Therefore, Set as the default parameter.

[0025] After performing dense sampling on the fitted curve, the number of sampling intervals for the drilling depth can be calculated; alternatively, the i-th sampling interval can be determined. Horizontal projection length and vertical projection length .

[0026] Accurate drilling trajectory acquisition (recovery). Counting from the wellhead, the i-th well depth interval... Horizontal projection length It can be obtained from the following formula: (1) The i-th well depth interval vertical projection length It can be obtained from the following formula: (2) The i-th well depth interval The geographic coordinate increment corresponding to the horizontal projection It can be obtained from the following formula: (3) (4) Let the elevation and coordinates of the borehole opening be respectively... Then the spatial coordinates and elevation of the end point of the Mth segment of the borehole Calculated using the following formulas respectively: (5) (6) (7) After calculating M=1 using the above formula until the number of samples corresponding to the maximum well depth is reached, we can accurately obtain (or recover) the actual borehole trajectory.

[0027] If a stratigraphic boundary lies between the Mth and M+1th sampling points, we can, based on the calculation of the Mth segment, set the small increments of coordinates and elevations within the M+1th segment (correspondingly denoted as MM). Simply add it in; the calculation formula is shown below: (8) (9) (10) For any interface depth, first determine the number of sampling segments it belongs to according to the selected calculation interval, and then perform the corresponding calculations according to formulas (5) to (10) to obtain the spatial coordinates of the borehole at that layer. All of these can be implemented by programming.

[0028] When programming, we set the fitting encryption interval. The options include 1, 2, 5, 10, 20, 25, and 50m. The 10, 20, 25, and 50m options are primarily used for accuracy comparison analysis between this method and commonly used methods, thereby testing the calculation method and programming effectiveness; they are not selected in actual application. The 1, 2, and 5m fitting refinement intervals are used for accurate borehole trajectory recovery. When the zenith angle given by borehole inclination logging is small and the azimuth angle changes slowly, a larger interval can be selected, such as 5m or 10m; otherwise, when the situation is more complex and the changes are drastic, a smaller interval should be selected. By default, we set the fitting refinement interval to 2m, which can meet the needs of most cases.

[0029] refer to Figure 1 and Figure 2 The two theoretical models shown exhibit more dramatic changes in borehole azimuth angle than the actual borehole azimuth angle. The results show that the borehole trajectory of the design model can be accurately recovered under such circumstances. The accuracy of the method will be even higher when applied to actual situations.

[0030] refer to Figure 3 The complexity of the theoretical model can be seen from the horizontal projection of the borehole trajectory.

[0031] refer to Figure 4 As the sampling intervals for borehole inclination logging across the entire well section become increasingly dense, the traditional broken-line method can accurately reconstruct the borehole trajectory. However, this approach is not feasible in practice, as it leads to low logging efficiency and increases the risk of in-hole accidents causing significant losses. Excessively dense sampling intervals also generate a large amount of redundant data, complicating the operation and calculation of conventional tables. This application achieves the desired encryption effect and accuracy without excessive densification; moreover, this method does not require equal-interval sampling during actual logging operations.

[0032] refer to Figure 5 Even when using inclinometer data at 50m intervals, the borehole trajectory obtained using this method is very close to the actual situation; if used for calculations on simpler models that are similar to most actual situations, the accuracy can still be improved.

[0033] refer to Figure 6 Using this method, borehole trajectories obtained from 20m interval survey data almost perfectly match the actual borehole conditions, achieving the required accuracy. The results were consistent when using other fitted curves. This demonstrates that this method requires only one borehole survey result with a normal sampling interval, eliminating the need for additional measurements, to ensure accurate borehole recovery.

[0034] refer to Figure 7 When the inclination measurement points are spaced 50m apart, if point A is considered the resource layer at depth, and inclination measurements are performed in this section, the borehole trajectory calculated using the traditional broken-line method will consist of two segments. Clearly, the borehole trajectory shape in the resource layer is closer to the actual situation, but it cannot eliminate the error caused by the large intervals in the segment above point A. If point B is considered the resource layer at depth, and inclination measurements are performed in this section, the conclusion is the same as for point A.

[0035] refer to Figure 8 When the inclination measurement point interval is 20m, if point A is considered the resource layer at depth, and inclination measurements are performed in this segment to a depth of 10m, the borehole trajectory calculated using the traditional broken-line method still consists of two segments. The borehole trajectory shape in the resource segment is closer to the actual situation, but there is no fundamental improvement. If point B is considered the resource layer at depth, and inclination measurements are performed in this segment with additional density, the conclusion is the same as that of point A. This figure shows that when the sampling interval reaches a certain level, densifying the collected data does not significantly improve the accuracy of borehole trajectory recovery.

[0036] refer to Figure 9 The borehole inclination in actual resource drilling is significantly simpler than that in theoretical models, making it easier to ensure the accuracy of this method. A sampling interval of 50m for actual borehole inclination is generally sufficient. However, to be on the safe side, it is recommended to select a sampling interval of 20m or 25m when conducting actual borehole inclination measurements.

[0037] refer to Figure 10 When logging in actual wells, the borehole inclination measurement data does not provide data at the wellhead, i.e., initial values ​​are missing. The initial values ​​for azimuth and zenith angles are determined based on... Figure 6 The method shown is used to determine this.

[0038] refer to Figure 11 This visually illustrates the relationship between various projections and increments in the i-th segment.

[0039] This application does not require that the data sampling intervals be equal, as long as the average sampling interval is around 20~25m and there are no particularly large gaps. A particularly large gap refers to more than 2~3 times the average interval.

[0040] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A calculation method for accurate recovery of borehole trajectories in resource exploration, characterized in that: include: S1. Establish raw data files: Raw data includes the borehole coordinates and elevation of the exploration borehole, and borehole inclination measurement data obtained from well logging; Borehole inclination measurement data refers to the zenith angle and azimuth angle data corresponding to the drilling depth with sampling intervals set according to current specifications. S2. Based on the original data file, determine the initial boundary conditions for the azimuth and zenith angles; the initial value of the azimuth angle can be obtained by extending the scatter curve trend to the wellhead, and the initial value of the zenith angle is set to 0. S3. Based on the borehole inclination measurement data and the determined initial boundary conditions, select multiple calculation methods, including linear interpolation, spline curve interpolation, polynomial fitting interpolation and parabolic interpolation, to achieve the purpose of fitting the curves of azimuth and zenith angle as a function of drilling depth H. S4. Convert the fitted curve into dense discrete data: perform dense sampling on the fitted curve; the dense sampling interval is significantly smaller than the well depth sampling interval for borehole inclination measurement during logging, and multiple options can be designed according to accuracy requirements; S5. Determine the drilling trajectory: Starting from the wellhead, at the i-th well depth interval... Horizontal projection length It can be obtained from the following formula: ; the i-th well depth interval Vertical projection length It can be obtained from the following formula: ; the i-th well depth interval The geographic coordinate increment corresponding to the horizontal projection and It can be obtained from the following formula: in Zenith angle, It is the azimuth angle; Let the elevation and coordinates of the borehole opening be respectively... Then the spatial coordinates and elevation of the end point of the Mth segment of the borehole Calculated using the following formulas respectively: After calculating M=1 according to the above formula until the number of samples corresponding to the maximum well depth is reached, the actual borehole trajectory can be obtained.

2. The calculation method for accurate recovery of borehole trajectory in resource exploration according to claim 1, characterized in that: In step S5, when the stratigraphic interface is located between the Mth and M+1th sampling points, based on the completion of the Mth segment calculation, the increments of coordinates and elevations within the M+1th segment are accumulated, and the increments of coordinates and elevations are set accordingly. Calculated by the following formula: ； ； The elevation and coordinate increments corresponding to the well depth increments between the Mth and M+1th sampling points are calculated using the formula in step S5.

3. The calculation method for accurate recovery of borehole trajectory in resource exploration according to claim 2, characterized in that: In step S4, the selectable parameters for the dense sampling interval are 1m, 2m, and 5m. After selecting the dense sampling interval, the calculation in step S5 is performed, and 2m is set as the default value.

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