Directional Drilling for Coal Mine Goaf Dewatering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for dewatering coal mine goafs are limited as they cannot cross neighboring goafs, leading to incomplete drainage and safety hazards, with conventional rotary drilling methods having issues with drilling length and trajectory deviation.
Innovation Solution
A method involving directional drilling with the calculation of a critical hydraulic connection value to determine the need for multiple holes, using a water stop casing, and ensuring accurate drilling through polyurethane sealing and pressure testing to achieve stable drainage across neighboring goafs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional rotary drilling method is used for goaf water detection and drainage, then the drilling operation is simple and equipment is easy to operate, but the drilling length is limited and trajectory deviation occurs making it impossible to cross neighboring goafs
Solution Approach 1:
The drilling operation is divided into multiple directional drilling sections with intermediate stopping points for trajectory adjustment. The drill hole is constructed in segments rather than a single continuous operation, allowing the trajectory to be redirected at intermediate points to achieve the desired long-range crossing path through the coal pillar and into the target goaf.
Solution Approach 2:
The drilling trajectory is made dynamic and adjustable rather than fixed. The drill direction can be changed at intermediate stopping points based on real-time trajectory monitoring and geological conditions. This dynamic adjustment capability enables the drill to compensate for deviations and achieve the intended long-range target that would be impossible with a static, single-pass drilling approach.
2Ease of operation
If conventional rotary drilling method is used, then the equipment is simple and easy to operate, but the drilling trajectory deviates from design parameters making it hard to accurately drill to the designed target layer
Solution Approach 1:
Real-time monitoring of drilling trajectory parameters is implemented during the directional drilling operation. The actual drill path is continuously measured and compared against the designed trajectory. This feedback information is used to make real-time adjustments to the drill direction at intermediate stopping points, ensuring the final hole accurately reaches the target goaf despite variations in geological conditions.
Solution Approach 2:
The drilling system transitions from a static, fixed-trajectory approach to a dynamic, adjustable-trajectory system. The drill direction can be modified at intermediate points based on real-time trajectory data and geological feedback. This dynamic control mechanism enables high precision in achieving the target location while maintaining operational simplicity through standardized adjustment procedures.
3Productivity
If only one directional hole is drilled, then the drilling operation is simpler and faster, but incomplete dewatering occurs when goafs are hydraulically isolated, creating safety hazards
Solution Approach 1:
The number of drill holes and their trajectories are adjusted based on the hydraulic connection parameters between goafs. By calculating the critical thickness of the coal pillar and assessing hydraulic connectivity, the system determines whether one or multiple directional holes are needed. This parameter-based decision-making ensures complete dewatering by adapting the drilling configuration to the specific hydrogeological conditions of each case.
Solution Approach 2:
Hydraulic connection assessment and critical thickness calculation are performed before the drilling operation to determine the optimal number and configuration of directional holes. This preliminary analysis allows the drilling plan to be optimized in advance, ensuring that the correct number of holes is drilled to achieve complete dewatering while avoiding unnecessary additional drilling operations.
4Length of moving object
If directional drilling to cross neighboring goaf is implemented, then extended drilling range and accurate dewatering of inaccessible goafs is achieved, but the device complexity and drilling process complexity increase
Solution Approach 1:
The complex directional drilling operation is segmented into standardized phases: initial drilling to first stopping point, trajectory adjustment, continued drilling to second stopping point, and final trajectory correction. Each phase uses standardized procedures and equipment configurations. This segmentation makes the complex process more manageable and reduces the need for highly specialized equipment by breaking down the complexity into repeatable, standardized steps.
Solution Approach 2:
The drilling system incorporates dynamic trajectory adjustment capabilities that are activated only when needed during the drilling process. The base equipment remains relatively simple, but includes the capability to adjust drill direction at intermediate stopping points. This dynamic flexibility is built into the standard equipment design, allowing extended drilling range without requiring overly complex specialized equipment for every operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for extended drilling range and accurate dewatering of previously inaccessible goafs, enhancing safety and efficiency by ensuring complete drainage and preventing leakage, thus mitigating the risks associated with goaf water in coal mines.
Implementation Method 1
inserting a water stop casing into the first directional hole drilled, cementing the water stop casing
Implementation Method 2
cementing the water stop casing, and carrying out a pressure test until a qualified pressure
Implementation Method 3
carrying out a pressure test until a qualified pressure
Implementation Method 4
first directional hole and the second directional hole are drilled separately... extending through the coal seam floor into a second goaf and a third goaf
Data Source
AI summary
A method for dewatering a coal mine goaf by crossing a neighboring goaf is applicable to a scenario including a first goaf, a second goaf, and a third goaf located sequentially at one side of a roadway. A directional hole mechanism is provided between the roadway and the second goaf as well as between the roadway and the third goaf. The directional hole mechanism passes through a coal seam floor at a bottom of the goaf and is communicated to the second goaf and the third goaf. The directional hole includes a first directional hole and a second directional hole. The first directional hole is communicated to the second goaf, the second directional hole is communicated to the third goaf, and the first directional hole is provided with a casing structure.