Experimental Study on Gas Loss Derived from Positive Pressure.

Area of Science:

• Geosciences
• Mining Engineering
• Coal Bed Methane Research

Background:

• Positive pressure sampling is used for rapid coal sample acquisition.
• Current methods for calculating gas loss under positive pressure rely on atmospheric pressure models, causing significant errors.

Purpose of the Study:

• To investigate the influence of positive pressure on gas loss during coal sampling.
• To determine the key factors affecting gas loss and improve the accuracy of gas content determination.

Main Methods:

• Experimental testing of gas desorption from anthracite coal under varying positive pressures and adsorption equilibrium pressures.
• Analysis of gas desorption rates and gas loss fluctuations.
• Comparison of gas loss values under different pressure conditions.

Main Results:

• Positive pressure is the primary factor influencing gas desorption, more so than adsorption equilibrium pressure.
• Positive pressure inhibits gas desorption, with decreasing desorption rates over time and with increasing positive pressure.
• Gas loss error rates increase significantly with positive pressure, reaching 63-180% relative error.

Conclusions:

• Positive pressure significantly affects gas desorption and introduces substantial errors in gas loss determination.
• The findings necessitate revising current methods for calculating gas loss under positive pressure.
• This research provides a theoretical and practical basis for accurate in-situ gas content determination in coal seams.