Multistage Pulse Fracturing for Uniform Coal Seam Fracture Networks
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Solution Overview
Problem
Conventional fracturing methods in directional long drilling of coal and rock seams in underground mines result in uneven distribution of fractures, with fractures being dense outside and sparse inside, and are limited by crustal stress, leading to poor gas extraction efficiency and safety concerns.
Innovation Solution
A method and equipment for multistage pulse hydraulic fracturing using high-frequency pulse water pressure to induce fatigue damage, forming multi-directional hydraulic fractures not controlled by crustal stress, and activating native fractures to create a uniform fractures network, facilitated by directional drilling rigs and advanced sealing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional constant-pumping rate fracturing is used, then the fracturing process is simple to implement, but fractures are unevenly distributed (dense outside and sparse inside) and controlled by crustal stress
Solution Approach 1:
The patent applies periodic pulse water pressure loading instead of constant pumping rate. The pulse frequency and amplitude are controlled to induce fatigue damage in the coal body, causing fractures to propagate in multiple directions不受 crustal stress control. This periodic action creates uniform fracture distribution throughout the reservoir while maintaining operational feasibility through automated pulse cycle control.
2Manufacturing precision
If high-frequency pulse water pressure is used to induce fatigue damage, then multi-directional hydraulic fractures are formed not controlled by crustal stress, but significant damage occurs to sealing equipment
Solution Approach 1:
The patent segments the fracturing process into multiple stages with progressive pulse intensity. The fracturing is divided into several intervals along the borehole depth, with each stage using appropriately controlled pulse parameters. This segmentation allows the sealing equipment to withstand the cumulative stress while still achieving the desired fracture network, as each stage builds upon the previous one without overwhelming the sealing system.
Solution Approach 2:
The patent implements beforehand cushioning by pre-installing multi-stage sealing devices that can withstand the anticipated pulse water pressure. The sealing equipment is designed and positioned in advance to absorb and distribute the high-frequency pulse stresses, protecting critical sealing points from damage while allowing the pulse energy to propagate and create fractures in the coal body.
3Area of stationary object
If directional long drilling is performed to reach deep coal seams, then the scope of reservoir transformation is expanded, but interference occurs between different fracturing intervals
Solution Approach 1:
The patent divides the long borehole into multiple discrete fracturing intervals or stages, each with its own sealing boundaries. This segmentation isolates the fracturing zones from one another, preventing interference between different intervals while allowing each to be treated independently. The multi-stage approach enables deep coal seam transformation without the harmful interactions that would occur in a single continuous fracturing zone.
Solution Approach 2:
The patent applies local quality by tailoring the pulse water pressure parameters (frequency, amplitude, duration) to the specific characteristics of each fracturing interval. Different sections of the long borehole receive customized pulse treatments based on local coal properties, depth, and stress conditions. This localized optimization ensures effective fracturing in each zone while minimizing interference with adjacent intervals.
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
The method forms a uniform fractures network, enhancing permeability and gas extraction efficiency, reducing impact hazards, and ensuring safe and efficient coal mine operations by forming a connected fractures network with uniform distribution.
Implementation Method 1
pulse hydraulic fracturing adopts pulse circulation pumping to cause fatigue damage to a coal body under the action of high-frequency pulse water pressure, thereby producing hydraulic fractures in various directions
Implementation Method 2
the high-frequency pulse water pressure impacts the coal body to easily activate natural fractures in the coal body, so that the hydraulic fractures are communicated with the natural fractures to form a complex fractures network
Data Source
AI summary
A method and a system for multistage pulse hydraulic fracturing in directional long drilling of coal and rock seams in underground mines are provided, which can perform multistage pulse hydraulic fracturing in directional long drilling of the coal and rock seams, thereby effectively solving the problem of uneven distribution of fractures caused by overall fracturing of long drilling, and the problem of fractures being “dense outside and sparse inside.” Further, a pressure of high-frequency pulse water in each stage induces fatigue damage to a coal-rock body, such that multi-directional hydraulic fractures that are not controlled by a crustal stress are formed, native fractures in the coal and rock seams are activated to form a fractures network. The pulse fractures network in each stage is expanded and connected, and an interconnected dense fractures network with uniform distribution of fractures is then formed in the directional long drilling.”