Design method for well section casing pipe with spacing smaller than 6m based on well group well track

Abstract

The invention discloses a well section casing design method based on well group well track spacing smaller than 6m, and belongs to the technical field of oil and gas well drilling and completion engineering design and construction.The well section casing design method comprises the steps that the spatial position and the minimum spacing of each well are known, a magnetic detection tool is used while drilling, and magnetic force lines of surrounding well casing strings are detected in the drilling process; relative position data of the drilling hole and the surrounding holes are calculated and transmitted back to the ground; according to the returned relative position data, the bending righting degree of the casing string of the vertical well section of each well is calculated; the outer diameter size and the twisting direction of the centralizer are adjusted according to the distance between a well hole and an adjacent well; drilling is completed; pigging the well; friction data and friction distribution conditions are recorded and analyzed in the drifting process; and when the maximum friction resistance is in the obstacle-avoiding well section, determining a main obstacle-avoiding well section, and using a coupling larger casing pipe. The design of the casing can be optimized, and the risk of sealing failure of the casing tripping-in thread is reduced.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well drilling and completion engineering design and construction, specifically to a casing design method for well sections with a spacing of less than 6m based on the wellbore trajectory of the well group. Background Technology

[0002] In recent years, due to stricter environmental protection policies, the number of shale oil and gas wells using well cluster development models has increased year by year. Changqing Shale Oil has adopted multi-layered, large-well-cluster, and three-dimensional development models in recent years. For example, the Hua H100 platform deploys 31 horizontal wells on a single platform, with a wellhead spacing of 8 meters and a wellhead row spacing of 31 meters, creating significant pressure to prevent collisions in the diameter and inclined sections. In the Bai 409 well area of ​​the Tenth Oil Production Plant, the Guan 18-78 well site deploys 73 vertical wells and highly deviated wells, with wellhead spacing of 4-8 meters, making collision prevention in the inclined sections difficult. Adjustment and infill drilling in older areas are all conducted at the original well sites, and the well site area is limited, making collision prevention between vertical wells difficult during new drilling. In 2021, the group company deployed a pilot project for in-situ conversion of Changqing Shale Oil to small-spacing horizontal well cluster drilling and completion technology, creating an urgent need for collision prevention tools. Meanwhile, drilling data from the 1990s and earlier are often inaccurate or even missing due to their age and storage methods, leading to unprecedented pressure on collision prevention during secondary operations. However, magnetic detection collision prevention tools must quickly change their wellbore trajectory when detecting casing from adjacent wells, resulting in significant bending and friction in local well sections, which limits their ability to safely run casing into operation.

[0003] Therefore, while developing passive precision magnetic detection anti-collision tools, we should improve the quality of casing installation, thereby improving the application of passive magnetic detection anti-collision tools and wellbore sealing to meet different production needs, and filling the industry gap in this technology.

[0004] Extensive technical research was conducted on the safe running of casing after downhole anti-collision operations, and the following similar technical measures are currently available: Firstly, as the Fuling shale gas field gradually forms a three-dimensional development well network, collision prevention analysis in the main area plays an increasingly important role in drilling operations within the complex space of upper and lower layers and densely packed wells. Taking the Jiaoye X6HF well as an example, to prevent collision accidents, conventional and three-dimensional scanning verifications were performed on the well's designed trajectory. By adjusting the trajectory, the collision prevention requirements of well depths of 2000-3000m and above, with a minimum distance of >40m, were met. Currently, the adjusted deployment well is located in the Jiaoshiba main area. The collision prevention scanning analysis process can be used in the Jiangdong and Pingqiao areas, and can also be promoted in the market, enabling repeated promotion and use.

[0005] Secondly, to achieve active ranging and directional drilling, a ground-penetrating radar (GPR)-based adjacent well detection technology is proposed, and its working principle and detection method are studied through simulation. By establishing a downhole radar detection model, theoretical analyses are conducted on issues such as the absorption boundary of the propagation medium, the dispersive medium model, and iterative algorithms. An antenna simulation model is built using XFDTD to simulate the propagation of radar signals in the formation within the time domain. The results show that GPR technology can be used for downhole adjacent well detection, especially when adjacent wells are close together, enabling precise collision avoidance.

[0006] Thirdly, application number 202010467593.8, "A Safety Assessment Method and System for Running Casing in Long-Section Horizontal Wells of Shale Gas," includes the following technical contents: using a three-dimensional soft rod string model to perform sensitivity analysis on the hook suspension weight and casing string friction coefficient to determine the predicted well casing running depth range; calculating the cumulative value of the actual drilling trajectory dogleg with well depth and comparing it with the cumulative trajectory dogleg of adjacent wells and the actual friction data of casing running to determine the critical cumulative dogleg value for casing running in the predicted well; calculating the well diameter variation coefficient using well diameter observation values ​​at regular intervals, analyzing the relationship between the well diameter variation coefficient of adjacent wells and the measured friction data of casing running, and determining the critical well diameter variation coefficient for casing running in the predicted well; determining the range of friction coefficient for casing running in adjacent wells through measured casing running data; determining the friction coefficient of the predicted well based on the above results; and determining the maximum well depth and risk level for different casing running methods based on the predicted well friction coefficient, generating a safety assessment result.

[0007] Fourth, based on an extensive survey of the current research status of collision prevention technology for dense cluster wells both domestically and internationally, and combined with field experience in collision prevention monitoring, this paper analyzes and summarizes the causes of wellbore collisions. It also analyzes existing wellbore trajectory optimization design methods, precise wellbore trajectory control technology, wellbore trajectory error models, real-time 3D visualization of wellbore trajectories, collision prevention risk assessment indicators, collision prevention operation requirements, and collision prevention monitoring technologies. Furthermore, based on the application of big data and artificial intelligence in oil and gas field development, it discusses the future development trends of collision prevention technology for dense cluster wells. This survey and analysis of the current research status of collision prevention technology for dense cluster wells can provide guidance for ensuring safe drilling of dense cluster wells.

[0008] Fifth, with the continuous advancement of drilling technology and measuring instruments, platform cluster wells are becoming increasingly popular due to their unique advantages, leading to a surge in the construction of large platform cluster wells. Ensuring no collisions between wellbores is a key aspect of platform cluster well construction. Therefore, the drilling platform must first be optimized, and then wellbore collision prevention measures are implemented from the drilling design stage based on the optimization results. During construction, calculations are performed based on actual inclination data, and collision prevention scanning calculations are conducted to guarantee that no wellbore collisions occur. In the platform collision prevention construction of 10 wells in Block F, techniques such as optimizing the build-up point, conducting three-dimensional torsional azimuth design, and applying MWD for drilling tracking were employed, achieving safe construction and accumulating experience for collision prevention of similar wells.

[0009] The above information addresses the issue of safe casing installation after downhole anti-collision operations, mainly proposing methods and measures from the aspects of on-site measures, tool signal anti-interference, well group trajectory optimization, radar detection models, magnetic ranging anti-collision while drilling, and real-time three-dimensional visualization of wellbore trajectory. However, it does not provide technical measures for the complex wellbore trajectory and significant increase in friction in the construction section after magnetic anti-collision tools have bypassed obstacles, which makes casing installation difficult. Summary of the Invention

[0010] The present invention aims to solve the problem that there are no technical measures in the existing technology for the complex wellbore trajectory after magnetic exploration anti-collision tools avoid obstacles and the difficulty of casing installation due to the significant increase in friction in the construction section. The present invention proposes a casing design method based on the wellbore trajectory spacing of the well group of less than 6m.

[0011] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A casing design method for well sections with spacing less than 6m based on wellbore trajectories in well groups, characterized by the following steps: Step a: Understand the spatial location and minimum spacing of each wellbore, and use magnetic exploration tools while drilling to detect the magnetic lines of force of the surrounding well casing string during the drilling process; Step b: Calculate the relative position data between the borehole and surrounding wells, and transmit the data back to the surface; Step c: Based on the returned relative position data, calculate the degree of bending and straightening of the casing string in the vertical section of each well. Step d: Adjust the outer diameter and azimuth of the centralizer according to the distance between the borehole and the adjacent well; Step e: Drilling completed; well cleaning; during well cleaning, record and analyze friction data and friction distribution. Step f: When the maximum friction is in the obstacle bypass section, determine the main obstacle bypass section and use a larger casing with couplings in the obstacle bypass section.

[0012] Furthermore, in step a, the environment in which the magnetic exploration tool is used should be selected appropriately to prevent excessive curvature during obstacle-around drilling.

[0013] Furthermore, in step a, the drilling tool structure used in the drilling process is: PDC drill bit + screw + reducer centralizer + magnetic anti-collision tool + MWD + drill collar + weighted drill pipe + drill pipe.

[0014] Furthermore, in step d, when the borehole is 8-10m away from the adjacent well, the outer diameter and azimuth of the centralizer are changed, and drilling monitoring continues.

[0015] Furthermore, in step d, when the distance between the borehole and the adjacent well is 5-6m, the outer diameter and azimuth of the centralizer are changed again to quickly deviate from the original trend in the borehole.

[0016] Furthermore, in step e, the drill string structure used is: original size drill bit + weighted drill pipe + original size centralizer + drill pipe.

[0017] Furthermore, in step f, a larger casing with couplings is used 100m above and below the obstacle-avoiding well section.

[0018] Furthermore, the outer diameter of the larger sleeve of the coupling is 162mm.

[0019] Furthermore, when the borehole is 8-10m away from the adjacent well, the outer diameter of the centralizer changes from 215mm to 210mm, and the azimuth changes by 5-6 degrees.

[0020] Furthermore, in step d, when the distance between the borehole and the adjacent well is 5-6m, the outer diameter of the centralizer changes from 210mm to 206mm, and the azimuth changes by 6-8 degrees.

[0021] In summary, the present invention has the following advantages: 1. This invention first designs and establishes a three-dimensional database of wellbore trajectories between well groups based on the wellbore trajectories of the drilling and completion of the well group, so as to enhance the spatial position of each wellbore; the drilling of the well group uses a magnetic exploration tool while drilling to monitor the trajectories of the surrounding wellbore in real time during the drilling process, and adjusts the wellbore trajectory in a timely manner to complete drilling and well completion and analyze the friction distribution, thereby optimizing the casing design and reducing the risk of casing thread seal failure. 2. The design concept of this invention can improve the impact resistance safety factor of the casing when it is lowered and lifted due to obstruction, ensure the integrity and sealing of the casing threads under overload compression, and provide a platform for subsequent multi-stage volumetric fracturing. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of one embodiment of the present invention; In the picture: 1. Horizontal well casing string; 2. Horizontal well borehole; 3. Horizontal well casing with enlarged outer diameter coupling; 4. Horizontal well casing string; 5. Well spacing; 6. Horizontal well borehole; Detailed Implementation

[0023] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0024] This invention provides a casing design method for well sections with spacing less than 6m based on wellbore trajectories, such as... Figure 1 As shown, it includes the following steps: Step 1: Choose the appropriate environment for using anti-collision tools to prevent excessive curvature during obstacle avoidance and drilling.

[0025] In practice, select a suitable well group with 8-10 wells; familiarize yourself with the drilling and completion design of each well in the well group; and design and establish a spatial well trajectory diagram for the well group based on the well trajectory of each drilled and completed well.

[0026] Step 2: Understand the spatial location and minimum spacing of each wellbore, and use magnetic exploration tools while drilling to detect the magnetic lines of force of the surrounding well casing string during the drilling process.

[0027] In this step, the drill string structure used, from bottom to top, is as follows: PDC drill bit + screw + reducer (215mm) + magnetic collision avoidance tool + MWD + drill collar + weighted drill pipe + drill pipe Step 3: Calculate the relative position data between the borehole and surrounding wells. The data is uploaded to the surface via the downhole MWD instrument, and the surface system display shows the accurate position of the casing string of each vertical section of the well group. Step 4: Based on the returned relative position data, calculate the degree of bending and straightening of the casing string in the vertical section of each well.

[0028] Step 5: When the distance between the borehole and the adjacent well is 8-10m, change the outer diameter of the centralizer to 210mm and the azimuth to 5-6 degrees / 30m; continue drilling and monitoring.

[0029] Step Six: When the distance between the borehole and the adjacent well is 5-6m, change the outer diameter of the centralizer to 208mm and the azimuth to 6-8 degrees / 30m, so that the borehole can quickly break away from the original trend.

[0030] Step 7: Drilling completed; Well cleaning; Drill string configuration: original size drill bit + weighted drill pipe + original size centralizer + drill pipe; Record and analyze friction data and friction distribution during well cleaning. Step 8: When the maximum friction is in the obstacle bypass section, determine the main obstacle bypass section (50-120m), and use larger casing with couplings 100m above and below the obstacle bypass section (250-320m).

[0031] like Figure 1 As shown, since the closest distance between horizontal wells No. 1 and No. 2 in the well group is 6m based on the trajectory, and the casing friction of horizontal well No. 1 is relatively large, in order to ensure the continuous integrity of the wellbore seal, a casing with a larger outer diameter of the coupling is designed in the dangerous section (for example, a casing with a coupling outer diameter of 162mm and a body outer diameter of 139.7mm is preferred) to prevent the casing thread from being damaged and the seal from failing during the running process.

[0032] The method of this invention can improve the impact resistance safety factor of casing during obstruction-induced lifting and lowering by 1.6-1.8; ensure the integrity and sealing of the casing threads under overload compression conditions, and provide a platform for subsequent multi-stage volumetric fracturing.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A casing design method for well sections with spacing less than 6m based on wellbore trajectories in well groups, characterized in that, Includes the following steps: Step a: Understand the spatial location and minimum spacing of each wellbore, and use magnetic exploration tools while drilling to detect the magnetic lines of force of the surrounding well casing string during the drilling process; Step b: Calculate the relative position data between the borehole and surrounding wells, and transmit the data back to the surface; Step c: Based on the returned relative position data, calculate the degree of bending and straightening of the casing string in the vertical section of each well. Step d: Adjust the outer diameter and azimuth of the centralizer according to the distance between the borehole and the adjacent well; Step e: Drilling completed; well cleaning; during well cleaning, record and analyze friction data and friction distribution. Step f: When the maximum friction is in the obstacle bypass section, determine the main obstacle bypass section and use a larger casing with couplings.

2. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step a, the environment in which the magnetic exploration tool is used should be selected appropriately to prevent excessive curvature during obstacle-bypass drilling.

3. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step a, the drilling tool structure used in the drilling process is: PDC drill bit + screw + reducer centralizer + magnetic anti-collision tool + MWD + drill collar + weighted drill pipe + drill pipe.

4. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step d, when the borehole is 8-10m away from the adjacent well, change the outer diameter and azimuth of the centralizer and continue drilling and monitoring.

5. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step d, when the distance between the borehole and the adjacent well is 5-6m, the outer diameter and azimuth of the centralizer are changed again to quickly deviate from the original trend in the borehole.

6. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step e, the drill string structure used is: original size drill bit + weighted drill pipe + original size centralizer + drill pipe.

7. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, In step f, a larger casing with couplings is used 100m above and below the obstacle-avoiding well section.

8. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 1, characterized in that, The outer diameter of the larger sleeve of the coupling is 162mm.

9. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 4, characterized in that, When the borehole is 8-10m away from the adjacent well, the outer diameter of the centralizer changes from 215mm to 210mm, and the azimuth changes by 5-6 degrees.

10. The casing design method for well sections with a spacing of less than 6m based on wellbore trajectories in well groups as described in claim 5, characterized in that, In step d, when the distance between the borehole and the adjacent well is 5-6m, the outer diameter of the centralizer changes from 210mm to 206mm, and the azimuth changes by 6-8 degrees.

Images