A geosteering parameter modeling method suitable for complex thin layers

Abstract

The present invention belongs to the technical field of oil and gas drilling exploration and development, and discloses a method for modeling geological guidance parameters suitable for complex thin layers. Precise guidance is achieved through the steps of seismic data collection and geological profile evaluation, geological data analysis and target window feature determination, establishment of a drilling trajectory guidance model, dynamic drilling tracking and real-time wellbore correction. Target window control is performed by combining the layer thickness method and the segmentation method, and the "five images and one table" tracking method is used to monitor the drilling trajectory in real time to ensure the efficient passage of the drill bit within the target reservoir. This method significantly improves the drilling rate under narrow target window geological conditions, reduces drilling risks, and improves the development efficiency and economic benefits of shale gas wells.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas drilling exploration and development, and in particular relates to a geosteering parameter modeling method applicable to complex thin layers. Background Art

[0002] In the field of oil and gas exploration and development, as conventional oil and gas resources become increasingly depleted, unconventional oil and gas resources (such as shale gas and tight oil and gas) that are more difficult to explore have gradually become the focus of development, especially in narrow target window geological areas with very limited thickness and width. These unconventional resources are often found under complex geological conditions, especially narrow target window geology, where the target reservoir thickness and width are extremely limited, perhaps only a few meters or even less. Such geological conditions pose a huge challenge to drilling projects. Existing technologies mainly use conventional geosteering tools while drilling for trajectory control, but the accuracy is still insufficient in narrow target window geology, resulting in problems such as the drill bit easily deviating from the target window, short residence time in the target window, and inability to fully drill into the oil and gas layer. Summary of the Invention

[0003] The present invention aims to provide a method for modeling geosteering parameters suitable for complex thin layers. By establishing a fine geosteering model and combining it with real-time drilling monitoring and wellbore correction technology, it ensures that the drill bit can be accurately guided in the target layer, thereby improving the drilling rate and economic benefits.

[0004] To achieve the above object, the present invention provides a method for geosteering parameter modeling applicable to complex thin layers, comprising the following steps:

[0005] S1, Seismic data collection and drilling geological profile evaluation:

[0006] Collect 2D and 3D seismic data: Collect 2D and 3D seismic data within the work area, fully cover the target strata, and ensure the accuracy and integrity of the seismic data;

[0007] Conduct drilling geological profile evaluation and analysis: Identify formation characteristics, clarify formation interfaces and structural morphology through seismic data analysis. Combined with well logging curves, analyze the lithologic characteristics, gas-bearing characteristics, formation pressure and its changing patterns of each formation;

[0008] Drilling trajectory trend prediction: Based on the geological profile, predict the structural changes and formation inclinations that may be encountered during the drilling process, and preliminarily determine the drilling trajectory design plan;

[0009] S2, geological data analysis and target window feature determination:

[0010] Collect geological data: collect existing geological reports, well logging data, core analysis results, etc. in the work area.

[0011] Analyze the sedimentary and reservoir characteristics of the target layer: Analyze the sedimentary environment, reservoir properties, and gas-bearing characteristics of the target layer to clarify the storage capacity and production capacity of the target layer; divide the target layer into small layers, determine the landmark points and formation occurrence, and facilitate the target window determination and guidance control in subsequent geological guidance;

[0012] S3, establish drilling trajectory guidance model:

[0013] Integrated seismic and geological data: Combine 2D and 3D seismic data with geological data within the work area to establish a 3D geological model; use seismic inversion technology to predict stratum distribution characteristics and conduct comprehensive predictions of the fine features of the target window;

[0014] Drilling trajectory guidance model: Based on the geological model, a drilling trajectory guidance model is established to simulate the ideal trajectory of the wellbore within the target window. The target window position, shape and geological characteristics are modeled to ensure the maximum length of the wellbore trajectory within the target window.

[0015] S4, dynamic drilling tracking and real-time wellbore correction:

[0016] Real-time drilling tracking: During the drilling process, dynamically acquire logging data and geological parameters, track logging and mud logging information during the actual drilling process; compare measured data with predicted data in the geological model to verify the entry into the target window;

[0017] Real-time wellbore monitoring and correction: Geosteering software analyzes real-time geological data and uses gamma or resistivity logging to assess the relative position of the wellbore to the target window in real time. When the wellbore deviates from the target window, a rotary steerable system (RSS) is used to correct the trajectory to ensure that the horizontal well accurately enters the target, allowing the wellbore to pass through high-quality reservoirs and remain in the optimal position.

[0018] By collecting and analyzing seismic and well logging data, a detailed description of the stratigraphic profile is constructed, the geological characteristics of each layer are identified, and the specific location and characteristics of the target window are determined. Accurate geological profile evaluation improves the accuracy of wellbore trajectory planning, effectively reducing drilling risks and the possibility of crossing non-target window layers. Systematic analysis of geological data aims to gain a deeper understanding of the physical properties, sedimentary environment, and reservoir characteristics of the target layer, which directly influence wellbore trajectory planning and the development of the steering model. Analysis of sedimentary and reservoir characteristics can improve the accuracy of target window positioning, ensure that the wellbore trajectory matches high-quality reservoirs, and increase the drilling encounter rate. By combining geological and seismic data, formation characteristics are inverted and predicted, and a refined steering model is developed. The steering model simulates the ideal wellbore trajectory within the target window, ensuring that the wellbore remains within the target window for the maximum length, thereby improving drilling efficiency. LWD data and geosteering software are used to monitor wellbore trajectory deviations in real time and, in conjunction with the rotary steerable system, enable timely corrections. Real-time monitoring and correction can ensure that the wellbore is accurately placed in the target layer, achieve maximum drilling of high-quality reservoirs, and improve resource recovery.

[0019] Furthermore, in step S4, the determination of marker layers and marker points during the drilling process is based on the overall structural relationship of the work area and the differences in the electrical characteristics of the formations, and the geological marker layers and marker points are accurately found to serve as reference points for geological guidance; the precise target entry control method is to combine the layer thickness method and the segmentation method to perform precise target entry control, and through accurate measurement of the formation thickness, ensure that the drill bit remains in the effective target reservoir when entering the target window; the segmentation control technology subdivides the drilling process into multiple control nodes according to the changes in different geological conditions in the target window, and each node is monitored and adjusted in real time to ensure a high drilling rate in the overall target window.

[0020] By precisely identifying marker layers and points, and combining the layer thickness method with the segmentation method to control target entry, the wellbore trajectory is kept stable within the target window. This method ensures the accuracy of geosteering and effectively improves the drilling rate of the target layer within the narrow target window.

[0021] Further, in step S4, the "five Figure 1 The "chart" tracking method uses near-bit azimuth gamma data to analyze and determine drill bit inclination, updating the formation dip in real time. Combined with the trajectory guidance model, it controls drilling inclination in real time to ensure efficient drilling. Five charts and a tracking chart provide detailed tracking and analysis of the drilling process, ensuring real-time understanding of formation changes. This method allows for more intuitive monitoring of geological and trajectory changes during drilling, improving guidance accuracy and reducing potential risks encountered during drilling.

[0022] Furthermore, in step S4, the actual drilling logging parameters include drilling logging parameters, cuttings logging parameters, gas logging parameters, and near-bit natural gamma parameters. Comprehensive analysis of these different logging parameters can provide comprehensive information on formation characteristics. Real-time monitoring of multiple parameters can effectively predict geological changes and provide data support for timely adjustments to the wellbore trajectory.

[0023] Furthermore, the vertical depth calculation of the target point of the marker layer in the layer thickness method is as follows:

[0024] Case 1: For the well area in front of the target formation with a formation dip angle within 1°, the vertical depth of the target point = a + h;

[0025] Case 2: For the well area in front of the target formation with a formation dip angle greater than 1°, the vertical depth of the target point = a + △h*sinα + d*tanα;

[0026] Case 3: For the well area in front of the target formation where the formation dip angle changes complexly, the vertical depth of the target point = a + △h*sinα + △d*tanα.

[0027] Different vertical depth calculation methods are used according to the inclination of the formation to ensure the accuracy of the target position. Through accurate vertical depth calculation, the risk of the wellbore deviating from the target window during drilling is minimized.

[0028] Furthermore, the “Five Figure 1 The tracking methods of the "Five Tables" include single well logging comprehensive histogram, horizontal section trajectory model diagram, well connection comparison diagram, well trajectory projection structural plan diagram, well trajectory projection seismic profile diagram, drilling well tracking analysis and undrilled formation prediction table. Figure 1 The "table" tracking method provides a comprehensive and integrated tracking and analysis system for geosteering, enabling effective monitoring and guidance of the drilling process across multiple dimensions. Intuitive data display: Graphs provide a visual display of formations, wellbore trajectories, and geological features, facilitating quick judgment and decision-making. Real-time adjustment capability: By combining actual drilling logging data with information from adjacent wells, comparative analysis, and real-time monitoring, the drilling trajectory can be adjusted in real time to ensure the wellbore maintains its maximum length through high-quality reservoirs. Improved steering accuracy: Multi-dimensional comparison and tracking effectively improves drilling accuracy within narrow target windows and reduces the risk of crossing non-target formations.

[0029] "five Figure 1 The "table" tracking method is a method that comprehensively utilizes multi-dimensional data to monitor and analyze the drilling process in real time. By combining five charts and a prediction table, it comprehensively tracks the wellbore trajectory and formation changes to ensure accurate guidance during the drilling process.

[0030] 1. Comprehensive histogram of single well logging

[0031] Content: Includes logging parameters such as drilling time, cuttings, gas logging, and comprehensive display of logging while drilling data.

[0032] The characteristics and parameter changes of each stratum are presented intuitively in the form of a bar chart.

[0033] Applications and Benefits: Single-well logging histograms help geosteering personnel gain a comprehensive understanding of the geological characteristics of each layer during drilling and adjust the wellbore trajectory based on measured data. This comprehensive display allows for intuitive comparison and analysis of drilling time variations, cuttings characteristics, and gas content across different formations, determining whether the wellbore is located within a high-quality reservoir.

[0034] 2. Horizontal segment trajectory model diagram

[0035] Content: Describes the trajectory of horizontal drilling and displays the relative position of the wellbore to the target layer. This includes the relationship between the depth range, shape, thickness, etc. of the target reservoir and the actual wellbore trajectory.

[0036] Uses and Benefits: Used to track the progress of horizontal wellbore within the target window, ensuring the wellbore trajectory remains within the target layer. By comparing the wellbore trajectory with the target layer position, geosteering personnel can adjust the drilling direction in a timely manner to maintain the well within the high-quality reservoir.

[0037] 3. Comparison chart of connected wells

[0038] Content: Contains stratigraphic comparison maps of multiple adjacent wells, showing stratigraphic divisions, marker layer depths, wellbore trajectories, and reservoir characteristics for each well.

[0039] Applications and Advantages: By comparing data from adjacent wells, the spatial variation and connectivity of strata within the work area can be understood, allowing adjustments and optimization of the current well trajectory. This can help determine the variation and extension of the target stratum between different wells, thereby improving the drilling rate.

[0040] 4. Well trajectory projection structural plan

[0041] Content: Displays the projection of the wellbore trajectory in the structural plane, including the structural morphology, dip angle and distribution of marker points of the target layer.

[0042] Applications and Benefits: Used to understand the relative position of the wellbore trajectory in the horizontal structural plane, especially the relationship between the wellbore and the formation structure. This ensures that the wellbore trajectory matches the structural characteristics, effectively avoiding formation faults and non-target areas, thereby improving drilling efficiency.

[0043] 5. Well trajectory projection seismic profile

[0044] Content: Combined with seismic data, the projection of the wellbore trajectory on the seismic section is displayed, showing the depth and changes relative to the formation during the wellbore's passage.

[0045] Uses and Benefits: Used to track the trajectory of a wellbore through the formation on a seismic profile, helping to determine whether the wellbore is within the target reservoir. This projection method directly demonstrates the alignment of the wellbore trajectory with the formation, ensuring that the wellbore follows the expected trajectory from the seismic profile.

[0046] 6. Tracking analysis of drilling wells and prediction table of undrilled formations

[0047] Content: Includes analysis of actual drilling data from the current well, stratigraphic marker penetration information, and predictions for undrilled strata. Provides geological characteristics and risk assessments for undrilled strata, extrapolated from existing seismic and adjacent well data.

[0048] Uses and Advantages: Used to track and record current drilling, including predictions of strata already traversed and those yet to be encountered. This helps geologists predict the characteristics of upcoming strata, adjust drilling parameters, reduce drilling risks, and ensure efficient stratum penetration. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A flowchart of the process steps of an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the layer thickness method of an embodiment of the present invention; DETAILED DESCRIPTION

[0051] The following is further described in detail through specific implementation methods:

[0052] Example: During shale gas well drilling in the Hongxing region, the target window is narrow and thin, requiring precise control of the wellbore trajectory to ensure that the wellbore enters and remains in the target layer for a long time. To achieve this, this example uses a combination of layer thickness and segmentation methods for wellbore guidance, ensuring the drill bit maximizes penetration in high-quality reservoirs.

[0053] Step 1: Steering control of the deflection section

[0054] Determine marker depth during drilling: Collect regional 2D and 3D seismic data and information from adjacent wells to determine the depth of key markers in the buildup section. Verify and correct the marker position in real time using well logging data to ensure accurate identification during the actual drilling process.

[0055] Determination of the thickness of the pre-target marker layer:

[0056] The thickness of the marker layer in front of the target window is determined based on seismic inversion results and formation logging curves. The marker layer is a key reference point in drilling guidance, and ensuring its thickness is accurate can significantly improve the accuracy of target entry.

[0057] Target vertical depth calculation (layer thickness method):

[0058] Calculate the vertical depth of the target using the layer thickness method: Case 1: For areas with gentle strata in front of the target (stratum dip angle within 1°), use the constant thickness method. The target vertical depth is calculated as: target vertical depth = a + h, where a is the vertical depth of the bottomhole marker layer and h is the difference in vertical depth between the marker layer and the target layer.

[0059] Case 2: For well areas with large formation dips, the equal thickness method combined with the overall formation dip method is used. The target vertical depth is calculated as follows: target vertical depth = a + Δh·sinα + d·tanα, where α is the vertical depth of the bottomhole marker layer, Δh is the vertical thickness between the marker layer and the target layer, d is the distance to the target, and α is the formation dip.

[0060] Case 3: For areas with complex formation dip variations, the equal thickness combined with the overall formation dip method is used. The target vertical depth is calculated as follows: target vertical depth = a + Δh·sinα + Δd·tanα; where a is the bottomhole vertical depth, d is the remaining distance to the target, Δd is the distance to the target below the marker, h is the vertical thickness of the two markers in the standard well, and Δh is the vertical thickness of the two markers in the build-up section.

[0061] Establish a steering model for the build section: Combine the vertical depth calculation of the target point with the seismic structural characteristics to establish a geosteering model for the build section. The model includes the depth, thickness, and inclination of the target layer, guiding the design and adjustment of the build section trajectory.

[0062] Correcting the targeting guidance model: During drilling, the accuracy of the model is verified using real-time data collected from logging while drilling. If the actual formation parameters do not match the predictions, the guidance model is readjusted and the wellbore trajectory is corrected to ensure smooth targeting during the buildup section.

[0063] Redesign the wellbore trajectory: Based on the correction results of the guidance model, redesign the wellbore trajectory, adjust the well inclination angle and wellbore direction to ensure accurate target entry.

[0064] Step 2: Horizontal Segment Guidance Control

[0065] Analysis of formation rock electrical characteristics: Gamma logging and resistivity logging data are used to analyze the rock electrical characteristics of the target layer to ensure that the wellbore can always remain at the target layer during horizontal drilling.

[0066] Pre-target occurrence prediction and marker layer identification (segmentation method): Before entering the horizontal section, combine the electrical characteristics of the formation and the occurrence prediction to identify important marker layers, which serve as key reference points in drilling guidance.

[0067] Statistical analysis was conducted based on the vertical difference between the key well inclination marker layer and the upper target frame of the target layer at the bottom of the Changxing Formation: the well inclination at the marker point at a vertical depth of about 35 meters above the bottom of the Changxing Formation was controlled at around 60°, serving as the control node for entering the horizontal section; the well inclination at the bottom of the Changxing Formation was controlled at around 77.5°, and was assisted in adjustment in combination with the marker point of the Wu II section.

[0068] Build a horizontal section steering model: A horizontal section steering model is constructed by combining formation rock and electrical characteristics with data from adjacent wells. The model includes the depth, thickness, occurrence, and geological variations of the target layer. During drilling, the model is modified in real time to adapt to actual geological conditions, ensuring the wellbore trajectory remains in the optimal position.

[0069] Real-time drilling data acquisition and adjustment: During horizontal drilling, real-time acquisition of gamma-ray logging, density logging, and cuttings data is used to determine whether the current wellbore position is within the target reservoir. Based on changes in formation dip and occurrence, the wellbore trajectory is adjusted to maintain the drill bit within the target reservoir.

[0070] Application of the segmented control method: The segmented method is used to precisely control the wellbore trajectory, dividing the horizontal drilling process within the target window into multiple control nodes: Node 1: Using the upper marker point on the bottom of the Changxing Formation, the wellbore inclination angle is adjusted within a vertical depth of 35 meters, maintaining a wellbore inclination angle of 60° to enter the target layer; Node 2: The wellbore inclination at the bottom of the Changxing Formation is controlled at around 77.5° to ensure that the wellbore can smoothly pass through the high-quality reservoir; Node 3: Combined with the Wu II member marker, further auxiliary adjustments are made to ensure that the wellbore trajectory of each segment remains in the optimal position within the target window.

[0071] Real-time model correction and trajectory adjustment: Based on the comparison of geological data collected while drilling and the steering model, the steering model is corrected in real time. The deflection angle of the rotary steerable system (RSS) is adjusted to ensure that the wellbore trajectory always stays within the target reservoir, thereby maximizing the reservoir penetration rate.

[0072] Summarize the adjustment rules of complex strata:

[0073] After drilling is completed, the actual changes in the formation are compared with the geological model, the adjustment process of the wellbore in the complex formation is analyzed, and the regularity of the horizontal section guidance is summarized to provide experience support for the construction of subsequent wells.

[0074] Implementation Effect

[0075] Improve the drilling rate of high-quality reservoirs: By combining the layer thickness method and the segmentation method, the wellbore trajectory is accurately controlled to ensure the efficient penetration of the wellbore within the target window, effectively increasing the probability of drilling into high-quality reservoirs.

[0076] Reduce the risk of target deviation: Combined with marker layer and segment control, the wellbore trajectory is ensured to match the formation characteristics, reducing the risk of deviation from the target window and target layer.

[0077] Improve drilling efficiency and economic benefits: Accurate target vertical depth calculation, real-time model correction and trajectory adjustment significantly improve drilling efficiency, reduce ineffective drilling and formation crossing errors, and enhance the economic benefits of shale gas well development.

[0078] Real-time adjustment and correction: During the drilling process, the use of logging while drilling, geological imaging, real-time data fusion and steering model correction enables dynamic adjustment of the wellbore trajectory and reduces the risk of wellbore deviation.

[0079] Improved steering management: By establishing and modifying the steering model and adjusting the wellbore trajectory, a systematic steering management process has been established, enabling precise control of the drilling process under complex geological conditions.

[0080] The above description is merely an embodiment of the present invention. Common knowledge regarding the specific structure and characteristics of the solution is not described in detail herein. It should be noted that those skilled in the art may make various modifications and improvements without departing from the structure of the present invention. These modifications and improvements should also be considered within the scope of protection of the present invention and will not affect the effectiveness and practicality of the present invention. The specific embodiments and other descriptions in the specification may be used to interpret the content of the claims.

Claims

1. A method for geosteering parameter modeling suitable for complex thin layers, characterized by: The following steps are involved: S1, Seismic data collection and drilling geological profile evaluation: Collect 2D and 3D seismic data: Collect 2D and 3D seismic data within the work area, fully cover the target strata, and ensure the accuracy and integrity of the seismic data; Conduct drilling geological profile evaluation and analysis: Identify formation characteristics, clarify formation interfaces and structural morphology through seismic data analysis; analyze the lithologic characteristics, gas-bearing characteristics, formation pressure and its changing patterns of each formation in combination with well logging curves; Drilling trajectory trend prediction: Based on the geological profile, predict the structural changes and formation inclinations that may be encountered during the drilling process, and preliminarily determine the drilling trajectory design plan; S2, geological data analysis and target window feature determination: Collect geological data: collect existing geological reports, well logging data, and core analysis results in the work area; Analyze the sedimentary and reservoir characteristics of the target layer: Analyze the sedimentary environment, reservoir properties, and gas-bearing characteristics of the target layer to clarify the storage capacity and production capacity of the target layer; divide the target layer into small layers, determine the landmark points and formation occurrence, and facilitate the target window determination and guidance control in subsequent geological guidance; S3, establish drilling trajectory guidance model: Integrated seismic and geological data: Combine 2D and 3D seismic data with geological data within the work area to establish a 3D geological model; use seismic inversion technology to predict stratum distribution characteristics and conduct comprehensive predictions of the fine features of the target window; Drilling trajectory guidance model: Based on the geological model, a drilling trajectory guidance model is established to simulate the ideal trajectory of the wellbore within the target window. The target window position, shape and geological characteristics are modeled to ensure the maximum length of the wellbore trajectory within the target window. S4, dynamic drilling tracking and real-time wellbore correction: Real-time drilling tracking: During the drilling process, dynamically acquire logging data and geological parameters, track logging and mud logging information during the actual drilling process; compare measured data with predicted data in the geological model to verify the entry into the target window; Real-time wellbore monitoring and correction: Geosteering software analyzes real-time geological data and uses gamma or resistivity logging to assess the relative position of the wellbore to the target window. When the wellbore deviates from the target window, the rotary steering system is used to correct the trajectory, ensuring that the horizontal well accurately enters the target and that the wellbore remains in the optimal position while passing through high-quality reservoirs. During the drilling process, marker layers and marker points are identified based on the overall structural relationship of the work area and the differences in the electrical characteristics of the formations. These are then used as reference points for geosteering. The precise target entry control method combines the layer thickness method with the segmentation method for precise target entry control. By accurately measuring the formation thickness, the drill bit is ensured to remain in the effective target reservoir when entering the target window. The segmentation control technology subdivides the drilling process into multiple control nodes based on the changes in different geological conditions within the target window. Each node is monitored and adjusted in real time to ensure a high drilling rate within the overall target window. The calculation formula for the vertical depth of the target point of the marker layer in the layer thickness method is as follows: Case 1: For the well area in front of the target formation with a formation dip angle within 1°, the vertical depth of the target point = a + h; Case 2: For the well area in front of the target formation with a formation dip angle greater than 1°, the vertical depth of the target point = a + △h*sinα + d*tanα; Case 3: For the well area in front of the target formation where the formation dip angle changes complexly, the vertical depth of the target point = a + △h*sinα + △d*tanα.

2. The method for geosteering parameter modeling applicable to complex thin layers according to claim 1, characterized in that: In step S4, the "five-graph-one-table" tracking method is used to analyze and determine the drill bit's inclination based on the near-bit azimuth gamma data. The inclination of the formation being penetrated is updated in real time. Combined with the trajectory guidance model, the drilling inclination is controlled in real time to ensure efficient drilling.

3. The method for geosteering parameter modeling applicable to complex thin layers according to claim 1, characterized in that: In step S4, the actual drilling logging parameters include drilling logging parameters, cuttings logging parameters, gas logging parameters, and near-bit natural gamma parameters.

4. The method for geosteering parameter modeling applicable to complex thin layers according to claim 2, characterized in that: The "five charts and one table" tracking method includes a comprehensive histogram of single well logging, a horizontal section trajectory model diagram, a well connection comparison diagram, a well trajectory projection structural plan diagram, a well trajectory projection seismic profile diagram, a drilling well tracking analysis, and an undrilled formation prediction table.

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