Electric Pulse Detention Fracturing for Coalbed Methane Permeability
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Solution Overview
Problem
Conventional hydrofracturing techniques for coalbed methane wells result in a limited number of small cracks in the coal bed, leading to low efficiency and high costs in coalbed methane exploitation, as the shock waves produced by existing electric pulse methods attenuate quickly and have a limited effective impact range.
Innovation Solution
The method involves constructing positive and negative electrode wellbores and using a high-voltage electric pulse device to create a plasma channel in the coal bed, where high-energy discharges form a large number of cracks through high-temperature thermal expansion and shock waves, increasing the permeability coefficient by 150 to 350 times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional hydrofracturing technique is used, then the coalbed methane well can be constructed, but the number of cracks is small and the cracks extend in a small range resulting in low yield
Solution Approach 1:
The patent replaces the conventional mechanical hydrofracturing system with an electric pulse detonation system. High-voltage electric pulses are applied to detonate explosive charges placed in the coalbed, creating shock waves that propagate through the formation. This substitution enables the creation of numerous cracks extending over 10 meters from the wellbore, significantly increasing the number of cracks compared to conventional hydrofracturing while improving methane yield.
2Reliability
If high-power electric pulse techniques are used to increase permeability, then the permeability can be increased, but the shock waves attenuate fast and have limited effective impact range
Solution Approach 1:
The patent introduces explosive charges as an intermediary medium between the electric pulse source and the coalbed formation. The electric pulses detonate these charges, which then generate shock waves that propagate through the coalbed. This intermediary approach allows the energy to be concentrated and transmitted effectively over distances exceeding 10 meters, overcoming the rapid attenuation problem of direct electric pulse techniques while maintaining reliable permeability enhancement.
3Productivity
If more cracks are created to increase yield, then the permeability improves, but the construction complexity and cost increase
Solution Approach 1:
The patent divides the fracturing process into discrete segments by placing multiple small explosive charges at different locations and depths within the coalbed. Each charge creates a localized fracture zone, and the combined effect of multiple segmented charges produces an extensive network of cracks throughout the formation. This segmentation approach achieves high permeability enhancement and increased methane yield while keeping individual charge units simple and the overall system manageable.
Data Source
AI summary
A permeability enhancement method for coalbed methane wells by using electric pulse detonation fracturing technology is applicable to exploitation of coalbed methane wells in coal beds with low permeability. Firstly, a positive electrode coalbed methane wellbore and a negative electrode coalbed methane wellbore are constructed from the ground surface to a coal bed. A fixed platform installed with a positive electrode and a high-voltage pulse device are placed, by using a derrick, downwards to a predetermined permeability enhancement portion of the coal bed in the positive electrode coalbed methane wellbore, and another fixed platform installed with a negative electrode is placed, by using a derrick, downwards to a predetermined permeability enhancement portion of the coal bed in the negative electrode coalbed methane wellbore. The coal bed between the positive electrode and the negative electrode is broken down by using a high voltage, and coalbed methane extraction is carried out in the positive electrode coalbed methane wellbore and the negative electrode coalbed methane wellbore. A large amount of energy produced by high-voltage electric pulse directly acts on the coal reservoir to form a plasma channel in the coal bed between the positive electrode and the negative electrode. The large amount of energy instantly passes through the plasma channel, and the produced high-temperature thermal expansion force and shock waves act on the coal bed, such that the number of cracks in the coal bed is effectively increased and a favorable condition is created for flowing of coalbed methane.