Binary Composite Liquid Fracturing for Coal Seam Gas Extraction
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Solution Overview
Problem
Current methods for controlling gas in steeply-inclined ultra-thick coal seams face challenges such as low permeability, difficulty in hydraulic fracturing due to undeveloped fissures, and pollution from traditional fracturing fluids, leading to inefficient gas extraction and safety concerns in coal mining.
Innovation Solution
A binary composite liquid system is developed, comprising a clean fracturing fluid and a novel microemulsion, which is injected into coal masses using high-pressure hydraulic fracturing and water jet slotting to improve permeability and enhance gas extraction, featuring a worm-like micelle fracturing fluid and a surfactant-based microemulsion for improved wetting and flowback prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional fracturing fluid is used for hydraulic fracturing, then the coal seam permeability can be improved, but the fluid causes severe pollution to formations and has low viscosity leading to incomplete flowback
Solution Approach 1:
The patent changes the physical and chemical parameters of the fracturing fluid by developing a binary composite liquid system with adjustable viscosity (5-500 mPa·s) and surface tension (20-80 mN/m). The fluid composition can be modified by changing the ratio of clean fracturing fluid to microemulsion, allowing optimization of both pollution control and gas extraction efficiency for different coal seam conditions
Solution Approach 2:
The patent creates a composite fracturing fluid system combining two different fluid types: clean fracturing fluid (water-based or oil-based) and microemulsion. This composite structure allows the fluid to simultaneously achieve good wetting properties, appropriate viscosity for carrying proppant, and environmental compatibility through the synergistic effects of its components
2Ease of operation
If water-based fracturing fluid is used, then the fluid has good flowability, but the coal seam surface hydrophobicity prevents normal wetting and spreading
Solution Approach 1:
The patent introduces microemulsion as an intermediary substance that mediates between the water-based fracturing fluid and the hydrophobic coal seam surface. The microemulsion contains surfactants that reduce surface tension and enable the fluid to wet and spread on coal surfaces while maintaining good flowability through its liquid state
Solution Approach 2:
The patent modifies the surface tension parameter of the fracturing fluid from the typical 70-80 mN/m of pure water to 20-80 mN/m by adding microemulsion. This parameter change enables the fluid to overcome coal seam hydrophobicity and achieve normal wetting and spreading while retaining flowability
3Productivity
If hydraulic fracturing is performed on steeply-inclined ultra-thick coal seams with undeveloped fissures, then gas extraction can be enhanced, but the operation becomes extremely difficult with mining depth increase
Solution Approach 1:
The patent changes the viscosity parameter of the fracturing fluid to 5-500 mPa·s, which is higher than traditional fluids. This increased viscosity provides better suspension and transport capability for proppant and debris in steeply-inclined seams, preventing fluid loss and improving fracturing effectiveness in difficult geological conditions
Solution Approach 2:
The binary composite liquid structure provides both the flowability needed for deep well injection and the viscosity required for effective fracturing in steeply-inclined seams. The microemulsion component enhances wetting of coal surfaces created by fracturing, ensuring proper proppant placement and maintaining fracture conductivity
4Object-affected harmful factors
If high viscosity fracturing fluid is used to prevent pollution, then the fluid carries proppant well, but the fluid cannot spread normally on coal seam surface
Solution Approach 1:
The patent independently optimizes two critical parameters: viscosity (5-500 mPa·s) for proppant transport and surface tension (20-80 mN/m) for surface spreading. The binary composite liquid system allows these parameters to be adjusted separately through composition ratio changes, resolving the trade-off between pollution control and spreading capability
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 effectively increases gas extraction flow rates, permeability, and desorption speed, ensuring safer and more efficient coal mining operations by forming a rapid and efficient gas control technology system.
Implementation Method 1
forming a rapid and efficient coal mass gas extraction promotion technology system of binary composite liquid fracturing and permeability improvement by means of the technical approaches such as high-pressure hydraulic slotting and fracturing
Implementation Method 2
the coal seam surface has hydrophobic and oleophilic properties, and a water-coal contact face has excessive large surface tension, so that water cannot spread normally on the coal seam surface
Implementation Method 3
a novel efficient and wetting microemulsion
Implementation Method 4
a clean and non-flowback fracturing fluid with a worm-like micelle
Implementation Method 5
a traditional fracturing fluid has a low viscosity and incomplete flowback, and thus will cause severe pollution to formations
Implementation Method 6
investigation and analysis are performed for a gas control effect of the steeply-inclined ultra-thick coal seam according to change characteristics and analysis of gas extraction flow rate, change characteristics and analysis of permeability coefficient of coal seam, change characteristics and analysis of gas natural desorption speed of coal mass
Data Source
AI summary
A steeply-inclined ultra-thick coal seam gas control method based on a binary composite liquid. The method includes taking a clean fracturing fluid system and a microemulsion as a binary composite liquid. The method includes injecting the binary composite liquid into a coal mass by means of a main hydraulic fracturing and permeability improvement method of hydraulic fracturing and water jet slotting to form a coal mass gas extraction system of binary composite liquid fracturing and permeability improvement. The method includes investigating and analyzing a gas control effect of the steeply-inclined ultra-thick coal seam according to change characteristics and analysis of gas extraction flow rate, change characteristics and analysis of permeability coefficient of coal seam, change characteristics and analysis of gas natural desorption speed of coal mass, change characteristics and analysis of gas concentration of return air flow of working face and theoretical analysis of drilling cuttings index.