Multi-dimensional geosteering method for middle-deep layer coal bed gas horizontal well

Abstract

The invention discloses a multi-dimensional geosteering method for a middle-deep layer coal bed gas horizontal well. The method comprises the following steps that S1, three-dimensional earthquake-geologic models of a marker bed and a target coal bed are established; s2, the hole drift angle of each marker bed during drilling is determined; s3, predicting the depth, thickness, stratigraphic dip and spatial distribution characteristics of the target coal seam; s4, ensuring accurate target entering of the horizontal well by adopting a layer-by-layer approaching method; s5, comprehensively analyzing horizontal section data to ensure high drilling rate; the method is suitable for the technical field of coal bed gas development, the marker bed hole drift angle layer-by-layer approaching control target entering technology is adopted, the optimal hole drift angle of each marker bed is quantitatively determined, in the actual drilling process, geosteering personnel only need to judge whether the hole drift angle meets the design or not when drilling is carried out on each marker bed, the analysis content and steps are simplified, and the efficiency is improved. And the analysis time when the depth deviation with the designed marker bed is large is saved, and the drilling time efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coalbed methane development, and specifically is a multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells. Background Art

[0002] Medium- and deep-seated coalbed methane (CBM) refers to unconventional natural gas primarily composed of methane, found at depths of 1,200 to 1,800 meters and primarily adsorbed on the surface of coal particles. China's CBM resources are vast, estimated at 25 trillion cubic meters. Currently, the primary development technology utilizes a combination of high-penetration horizontal well drilling and large-scale volumetric fracturing. High-penetration horizontal well drilling provides the foundation for the commercial development of CBM resources.

[0003] High-drilling-rate horizontal well drilling technology aims to ensure the target coal seam's encounter rate by employing geosteering techniques to create a horizontal well within the target coal seam that conforms to the well's geological and engineering designs. For example, the invention patent "A Three-Dimensional Geological Steering Method for Horizontal Wells," published on July 6, 2016, with publication number CN105740639A, designs a three-dimensional geological steering method for horizontal wells. This patent utilizes parameters such as three-dimensional stratigraphic correlation, sedimentary microfacies analysis, while-drilling parameter tracking and evaluation, and geological model optimization to achieve a transition from qualitative to semi-quantitative geosteering, maximizing the effectiveness of horizontal well drilling. However, the establishment of its geological model is mainly based on the stratigraphic information revealed by the scattered distribution of drilled wells. The changes in geological characteristics between wells are only qualitatively analyzed and evaluated based on sedimentary microfacies analysis technology, which is subject to great multi-solutions and uncertainty. As a result, the actual changes in the three-dimensional spatial depth, thickness, stratigraphic dip and spatial distribution characteristics of the target layer cannot be accurately predicted. It cannot provide geological guidance personnel with early warning prompts to adjust the wellbore trajectory in advance to achieve the drilling purpose, and there are significant technical limitations. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells, comprising the following steps:

[0007] S1 establishes a 3D seismic-geological model of the marker layer and target coal seam;

[0008] S2 determines the well inclination angle of each marker layer encountered;

[0009] S3 predicts the depth, thickness, stratum dip and spatial distribution characteristics of the target coal seam;

[0010] S4 uses a layer-by-layer approach to ensure that horizontal wells are accurately targeted;

[0011] S5 comprehensively analyzes horizontal section data to ensure high drilling rate;

[0012] S6 adjustment and optimization model.

[0013] Preferably, the step S1 specifically includes:

[0014] Based on 3D seismic data and drilling data from adjacent wells, we first established multiple stratigraphic comparison framework sections in the target area, identified the stably developed marker layers in the target area, and used synthetic record calibration technology to calibrate the marker layers to the 3D seismic data. We then identified the seismic reflection events corresponding to each marker layer and established a 3D seismic-geological model of the marker layers and target coal seams.

[0015] Preferably, the step S2 specifically includes:

[0016] The designed horizontal wellbore trajectory data is imported into the 3D seismic data, and the well inclination angle of each marker layer encountered by the designed horizontal wellbore trajectory is determined layer by layer from deep to shallow, and the depth of each marker layer is predicted to ensure that the horizontal well successfully enters the target coal seam at the designed well inclination angle.

[0017] Preferably, the step S3 specifically includes:

[0018] Along the designed horizontal wellbore trajectory, the calibrated event axis of the target coal seam is horizontally tracked and interpreted in the 3D seismic data. The depth and thickness of the target coal seam along the horizontal wellbore trajectory are predicted at certain intervals. Possible local anomalies are identified, the horizontal section control points are determined, the inclination of each section of the target coal seam is calculated, the 3D spatial distribution characteristics of the target coal seam are precisely characterized, and wellbore trajectory adjustment measures are formulated in advance.

[0019] Preferably, the step S4 specifically includes:

[0020] The S41 uses logging cuttings data, gas logging data, measurement while drilling data, and data from adjacent wells to determine the current drilling layer in real time, compare and analyze the deviation between the actual drilling inclination angle of each marker layer and the designed well inclination angle, and formulate a wellbore trajectory adjustment plan;

[0021] Among them, if the actual drilling inclination angle is less than the designed well inclination angle, increase the wellbore inclination rate to ensure that the well inclination angle of the next marker layer meets the designed well inclination angle;

[0022] If the actual drilling inclination angle is equal to the designed well inclination angle, continue drilling according to the designed wellbore inclination rate;

[0023] If the actual drilling inclination angle is greater than the designed well inclination angle, the wellbore inclination rate should be appropriately adjusted according to the predicted vertical thickness between the upper and lower marker layers to avoid the failure of drilling into the target due to excessive well inclination when encountering the next marker layer;

[0024] S42 adopts the method of step S41, and conducts comparative analysis layer by layer from shallow to deep, and adjusts the wellbore trajectory in real time to gradually approach the target coal seam to ensure accurate target entry.

[0025] Preferably, the step S5 specifically includes:

[0026] S51 uses the coal seam structure, coal seam GR, coal seam gangue GR, roof and floor GR characteristics of the target coal seam in the adjacent well as the LWD measurement while drilling upper and lower gamma data, rock cuttings data, gas logging data, and drilling time data for comprehensive analysis to determine the current coal seam position of the drill bit;

[0027] S52 compares and analyzes the deviation between the predicted coal seam formation dip and the actual drilled coal seam dip, evaluates the accuracy of the predicted coal seam formation dip and the three-dimensional spatial distribution characteristics of the coal seam, provides a basis for subsequent wellbore trajectory adjustment plans, and ensures a high drilling rate of the target coal seam in horizontal wells.

[0028] Preferably, the step S6 specifically includes:

[0029] After drilling is completed, the deviation between the design and the actual drilling is analyzed. If the preset trajectory is not satisfied, steps S2-S5 are repeated to adjust the optimization model.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] 1. The present invention adopts a marker layer inclination angle layer-by-layer approach to control the target entry technology, quantitatively determining the optimal well inclination angle of each marker layer. During the actual drilling process, the geological guidance personnel only need to judge whether the well inclination angle meets the design when drilling each marker layer. This simplifies the analysis content and steps, saves analysis time when there is a large deviation from the designed marker layer depth, and improves drilling efficiency.

[0032] 2. The present invention develops a geosteering technology for horizontal wells with high drilling rates for medium- and deep-seated coalbed methane (CBM). Based on 3D seismic data, the dip angle of the coal seam along the horizontal wellbore trajectory is quantitatively predicted in advance, anomalies in the horizontal coal seam development are identified, control points are set, and wellbore trajectory adjustment measures are formulated. During actual drilling, the drill bit's coal seam position is determined in real time based on multi-dimensional data such as coal seam structure data from adjacent wells, LWD measurement while drilling data, rock cuttings data, gas logging data, and drilling time data. The accuracy of the predicted dip angle and anomalies is evaluated, and the wellbore trajectory adjustment plan is optimized to ensure a high drilling rate for the target coal seam. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of the present invention;

[0034] Figure 2 This is a schematic diagram of the well inclination angle control layer by layer approach control of the target in the present invention;

[0035] Figure 3 This is a schematic diagram for determining the position of the coal seam encountered during drilling in the horizontal section of the present invention;

[0036] Figure 4 This is the seismic reflection axis characteristic map of the marker layer in the Yushe-Wuxiang block area of ​​the present invention;

[0037] Figure 5 It is a superposition diagram of the designed wellbore trajectory and seismic profile of Well X in the present invention;

[0038] Figure 6 This is the distribution map of the target coal seam stratum dip angle and control points in the horizontal section of Well X in the present invention;

[0039] Figure 7 This is the accurate target map for layer-by-layer approach of the well inclination angle control of the X-well inclination section of the present invention;

[0040] Figure 8 This is a wellbore trajectory diagram of the horizontal section of Well X in the present invention. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention are described in detail below.

[0042] The "ranges" disclosed herein are defined in the form of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a particular parameter, it is understood that ranges of 10 to 40 and 20 to 50 are also contemplated. Furthermore, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​listed are 3, 4, and 5, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are listed herein, and "0 to 5" is simply an abbreviation for these numerical combinations.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0044] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0045] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0046] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0047] Unless otherwise specified, the reaction is carried out at room temperature and pressure.

[0048] Unless otherwise specified, all parts or percentages are by weight.

[0049] In the present invention, all substances used are known substances and can be purchased or synthesized by known methods.

[0050] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0051] The following examples further illustrate a specific embodiment of a multi-dimensional geosteering method for a medium-deep coalbed methane horizontal well of the present invention. The multi-dimensional geosteering method for a medium-deep coalbed methane horizontal well of the present invention is not limited to the description of the following examples.

[0052] Example 1:

[0053] A multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells, such as Figure 1 As shown, the following steps are included:

[0054] Step 1: Build a reliable geological model

[0055] Based on 3D seismic data and drilling data from adjacent wells, we first established multiple stratigraphic comparison framework sections in the target area, identified the stably developed marker layers in the target area, and used synthetic record calibration technology to calibrate the marker layers to the 3D seismic data. We then identified the seismic reflection events corresponding to each marker layer and established a reliable 3D seismic-geological model of the marker layers and target coal seams.

[0056] Step 2: Determine the inclination angle of each marker layer encountered

[0057] The designed horizontal wellbore trajectory data is imported into the 3D seismic data. From deep to shallow, the wellbore trajectory of the designed horizontal well is determined layer by layer to drill each marker layer and predict the depth of each marker layer to ensure that the horizontal well successfully enters the target coal seam at the designed well inclination angle.

[0058] Step 3: Predict the depth, thickness, dip angle and spatial distribution characteristics of the target coal seam

[0059] Along the designed horizontal wellbore trajectory, the calibrated event axis of the target coal seam is horizontally tracked and interpreted in the 3D seismic data. The depth and thickness of the target coal seam along the horizontal wellbore trajectory are predicted at certain intervals. Possible local anomalies are identified, the horizontal section control points are determined, the inclination of each section of the target coal seam is calculated, the 3D spatial distribution characteristics of the target coal seam are precisely characterized, and wellbore trajectory adjustment measures are formulated in advance.

[0060] Step 4: If Figure 2 As shown, the layer-by-layer approach is used to ensure that the horizontal wells are accurately placed on the target.

[0061] During the actual drilling process, the current drilling layer position is determined in real time using logging cuttings data, gas logging data, measurement while drilling data, and data from adjacent wells. The deviation between the actual drilling inclination angle and the designed well inclination angle of each marker layer is compared and analyzed, and a wellbore trajectory adjustment plan is formulated: If the actual drilling inclination angle is less than the designed well inclination angle, the wellbore inclination rate needs to be increased to ensure that the wellbore inclination angle of the next marker layer meets the designed wellbore inclination angle; if the actual drilling inclination angle is equal to the designed wellbore inclination angle, drilling continues at the designed wellbore inclination rate; if the actual drilling inclination angle is greater than the designed wellbore inclination angle, the wellbore inclination rate needs to be appropriately adjusted according to the predicted vertical thickness between the upper and lower marker layers to avoid a failure to hit the target due to an excessively large well inclination angle when drilling into the next marker layer. Using the above method, from shallow to deep, layer by layer comparative analysis is carried out, and the wellbore trajectory is adjusted in real time to gradually approach the target coal seam to ensure accurate target entry.

[0062] Step 5: Comprehensively analyze horizontal section data to ensure high drilling rate

[0063] Based on the coal seam structure, coal seam GR, coal seam interbedded GR, roof and floor GR characteristics of the target coal seam in the adjacent well, the current coal seam position of the drill bit is determined by comprehensive analysis of the upper and lower gamma data of LWD while drilling measurement, rock cuttings data, gas logging data, and drilling time data (such as Figure 3Compare and analyze the deviation between the predicted coal seam formation dip and the actual drilled coal seam dip, evaluate the accuracy of the predicted coal seam formation dip and the three-dimensional spatial distribution characteristics of the coal seam, provide a basis for subsequent wellbore trajectory adjustment plans, and ensure a high drilling rate of the target coal seam of the horizontal well.

[0064] Step 6: Adjust the optimization model

[0065] After drilling is completed, timely analysis of the deviation between design and actual drilling is carried out to adjust the optimization model.

[0066] By adopting the above technical solutions:

[0067] This multi-dimensional geosteering method, centered on controlling well inclination to achieve accurate target placement layer by layer and using real-time deviation correction to predict horizontal coal seam dip angles to control horizontal wellbore trajectory adjustments, relies on 3D seismic data, actual drilling data from adjacent wells, actual drilling logging and cuttings data, gas logging data, drilling time data, and LWD measurement while drilling data to achieve accurate horizontal well targeting and a high coal seam penetration rate in horizontal sections. Based on 3D seismic and adjacent well data, the method first predicts the well inclination angles of each major marker layer encountered and the coal seam dip angle along the horizontal wellbore trajectory. Then, by comparing and analyzing the deviations between the actual drilled well inclination angles and the predicted well inclination angles for each major marker layer, trajectory adjustment measures are formulated layer by layer to achieve accurate target placement according to the designed well inclination angle. Next, during horizontal drilling, the location of the drilled coal seam and the actual coal seam dip angle are determined section by section based on the coal seam structure of adjacent wells and LWD measurement while drilling data, and the horizontal wellbore trajectory and adjustment plan are corrected in real time. The system is simple to operate, real-time and efficient, and enhances the role of 3D seismic data in the horizontal well drilling process. It ensures the coal seam drilling rate based on a variety of data and greatly improves the horizontal well construction cycle.

[0068] Example 2:

[0069] The technical approach of this invention was implemented in the Yushe-Wuxiang block, located in the central-eastern Qinshui Basin. The primary coal seam, the Taiyuan Formation No. 15 coal, is buried at a depth of 1,200 to 1,800 meters and 4 to 7 meters thick, making it a typical medium- to deep-seated coalbed methane (CBM) zone. Three-dimensional seismic data confirms that the block exhibits east-west zoning: a complex syncline with alternating northeast-trending uplifts and depressions in the west, and a west-dipping monocline in the east. Faults with throws greater than 10 meters are undeveloped, making it suitable for large-scale horizontal well development. The multi-dimensional geosteering method proposed in this invention for medium- to deep-seated CBM horizontal wells has been applied in this area with promising results.

[0070] Well X is located in the eastern slope of the Yushe-Wuxiang block. It was designed as a horizontal well with a designed depth of 2771.60 meters. Through the implementation of the geosteering method of this invention, the 15# coal seam of the Taiyuan Formation was accurately targeted in one go, achieving a 100% penetration rate in the horizontal section. The implementation steps are as follows:

[0071] Step 1: If Figure 4 As shown, regional stratigraphic comparison, identification of stable marker layers and calibration of their seismic reflection events

[0072] Stratigraphic correlations conducted through 28 vertical wells confirmed that above the 15# coal seam of the Taiyuan Formation in the Yushe-Wuxiang block, four sets of stable, correlative marker layers are developed, from deep to shallow: the Taiyuan Formation K2 limestone, K4 limestone, 9# coal, and the Shanxi Formation 3# coal. These four marker layers have distinct seismic reflection event characteristics, making them easy to track and interpret throughout the entire area. Therefore, these four marker layers were selected as key target layers.

[0073] Step 2: If Figure 5 As shown in the figure, the horizontal wellbore trajectory is designed to determine the four key layer well inclination angles.

[0074] With the target well inclination angle of 88° to 90°, a three-stage or five-stage horizontal wellbore trajectory design method was used to design the wellbore trajectory and project it onto the 3D seismic data. The wellbore inclination angles at the intersections with the four key layers were determined: the wellbore inclination angle at the 3# coal top of the Shanxi Formation was 47°, the wellbore inclination angle at the 9# coal top of the Taiyuan Formation was 60°, the wellbore inclination angle at the K4 limestone top of the Taiyuan Formation was 62°, and the wellbore inclination angle at the K2 limestone top of the Taiyuan Formation was 72°.

[0075] Step 3: If Figure 6 As shown, predict the target coal seam stratum dip and identify the control points, and formulate adjustment measures

[0076] Along the horizontal section, the designed trajectory direction is measured at intervals of 20 meters. The depth difference h between the target coal seam top surface is measured between two intervals. The coal seam formation dip angle at each interval is calculated using the formula arctan = h / 20 and marked on the seismic reflection phase axis of the coal seam top surface. Simultaneously, the formation dip trend is analyzed, and points with steep increases in formation dip are identified as control points for trajectory adjustment. Preemptive inclination increases are performed to prevent coal from leaking from the floor, ensuring that the wellbore trajectory remains within the coal seam.

[0077] Step 4: If Figure 7 As shown, the well inclination angle is controlled layer by layer to accurately enter the target

[0078] Before drilling into the Shanxi Formation, the wellbore trajectory proceeded normally according to the planned trajectory. After reaching the Shanxi Formation, real-time comparisons of logging data, gas logging data, and drilling time data with data from adjacent wells were performed. Depth data for the four key target marker layers were obtained and provided to the geosteering personnel for comparison of the actual drilling inclination with the planned inclination. When Well X encountered the Shanxi Formation's 3# coal seam, the actual inclination was 49°, 2° higher than the planned inclination. The vertical distance to the Taiyuan Formation's 9# coal seam was estimated to be approximately 60m, and a 5° / 30m inclination rate was sufficient to adjust the inclination to 60°. Therefore, drilling continued at this rate. This method was applied layer by layer, with inclination deviations compared layer by layer. The inclination rate was adjusted in real time until the inclination at the target layer, the 15# coal roof of the Taiyuan Formation, reached 89°, achieving accurate target engagement.

[0079] Step 5: Figure 8 As shown, the horizontal section real-time correction of the predicted coal seam inclination and optimization of trajectory adjustment measures

[0080] During the horizontal section, along the predicted coal seam dip, the drill bit's position in the coal seam was determined in real time based on LWD measurement-while-drilling data, mud logging data, gas logging data, drilling time data, and coal seam structure information from adjacent wells. Furthermore, the coal seam dip, calculated from the LWD measurement-while-drilling data, was 7° upward, close to the predicted dip. Therefore, during the horizontal section, trajectory adjustments were made only at control points according to the trajectory adjustment plan. The well achieved a 100% coal seam encounter rate and a well construction period of 20 days.

[0081] Step 6: Post-drilling evaluation

[0082] The actual drilling process of Well X confirmed that the multi-dimensional geosteering method proposed in the present invention has a reliable process, reasonable parameter selection and model, and the model can continue to be used for geosteering in horizontal well drilling.

[0083] By adopting the above technical solutions:

[0084] Based on 3D seismic data and drilling data from adjacent wells, the well inclination angles of the main marker layers and the dip angles of the target coal seams in the horizontal section along the wellbore trajectory are quantitatively determined. A reliable geological model is established and the depth, thickness, dip angle and spatial distribution characteristics of the target coal seams are predicted. Combined with various parameters such as horizontal well drilling cuttings data, gas logging data, drilling time data, and LWD measurement while drilling data, the stratigraphic level encountered in the actual drilling, the well inclination angle, and the location of the target coal seam in the horizontal section of the wellbore trajectory are accurately determined. The deviation between the actual drilling data and the designed wellbore trajectory is analyzed, and a wellbore trajectory adjustment plan is formulated to achieve accurate target entry of the horizontal well and a high encounter rate of the target coal seam in the horizontal section, thereby meeting the purpose of rapid well construction and drilling of single horizontal wells.

[0085] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells, characterized by: The following steps are involved: S1 establishes a 3D seismic-geological model of the marker layer and target coal seam; S2 determines the well inclination angle of each marker layer encountered; S3 predicts the depth, thickness, stratum dip and spatial distribution characteristics of the target coal seam; S4 uses a layer-by-layer approach to ensure that horizontal wells are accurately targeted; S5 comprehensively analyzes horizontal section data to ensure high drilling rate; S6 adjustment and optimization model.

2. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S1 specifically includes: Based on 3D seismic data and drilling data from adjacent wells, we first established multiple stratigraphic comparison framework sections in the target area, identified the stably developed marker layers in the target area, and used synthetic record calibration technology to calibrate the marker layers to the 3D seismic data. We then identified the seismic reflection events corresponding to each marker layer and established a 3D seismic-geological model of the marker layers and target coal seams.

3. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S2 specifically includes: The designed horizontal wellbore trajectory data is imported into the 3D seismic data, and the well inclination angle of each marker layer encountered by the designed horizontal wellbore trajectory is determined layer by layer from deep to shallow, and the depth of each marker layer is predicted to ensure that the horizontal well successfully enters the target coal seam at the designed well inclination angle.

4. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S3 specifically includes: Along the designed horizontal wellbore trajectory, the calibrated event axis of the target coal seam is horizontally tracked and interpreted in the 3D seismic data. The depth and thickness of the target coal seam along the horizontal wellbore trajectory are predicted at certain intervals. Possible local anomalies are identified, the horizontal section control points are determined, the inclination of each section of the target coal seam is calculated, the 3D spatial distribution characteristics of the target coal seam are precisely characterized, and wellbore trajectory adjustment measures are formulated in advance.

5. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S4 specifically includes: The S41 uses logging cuttings data, gas logging data, measurement while drilling data, and data from adjacent wells to determine the current drilling layer in real time, compare and analyze the deviation between the actual drilling inclination angle of each marker layer and the designed well inclination angle, and formulate a wellbore trajectory adjustment plan; Among them, if the actual drilling inclination angle is less than the designed well inclination angle, increase the wellbore inclination rate to ensure that the well inclination angle of the next marker layer meets the designed well inclination angle; If the actual drilling inclination angle is equal to the designed well inclination angle, continue drilling according to the designed wellbore inclination rate; If the actual drilling inclination angle is greater than the designed well inclination angle, the wellbore inclination rate should be appropriately adjusted according to the predicted vertical thickness between the upper and lower marker layers to avoid the failure of drilling into the target due to excessive well inclination when encountering the next marker layer; S42 adopts the method of step S41, and conducts comparative analysis layer by layer from shallow to deep, and adjusts the wellbore trajectory in real time to gradually approach the target coal seam to ensure accurate target entry.

6. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S5 specifically includes: S51 uses the coal seam structure, coal seam GR, coal seam gangue GR, roof and floor GR characteristics of the target coal seam in the adjacent well as the LWD measurement while drilling upper and lower gamma data, rock cuttings data, gas logging data, and drilling time data for comprehensive analysis to determine the current coal seam position of the drill bit; S52 compares and analyzes the deviation between the predicted coal seam formation dip and the actual drilled coal seam dip, evaluates the accuracy of the predicted coal seam formation dip and the three-dimensional spatial distribution characteristics of the coal seam, provides a basis for subsequent wellbore trajectory adjustment plans, and ensures a high drilling rate of the target coal seam in horizontal wells.

7. The multi-dimensional geosteering method for medium-deep coalbed methane horizontal wells according to claim 1, characterized in that: The step S6 specifically includes: After drilling is completed, the deviation between the design and the actual drilling is analyzed. If the preset trajectory is not satisfied, steps S2-S5 are repeated to adjust the optimization model.

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