Effect of the Hydrate Saturation of the Pores of Coal Bed on the Gradient of Gas Pressure and the Rise of Outburst Danger

Vyacheslav Smirnov,Tatyana Kim,Valery Dyrdin,Andrey Manakov,M Tyulenev,A Khoreshok,D Marasová,Y Tan,S Zhironkin,D Nuray,P Stefanek,S Vöth,S Anyona,A Abay,M Cehlár,J Janocko

doi:10.1051/e3sconf/201910501044

Abstract

A substantial fraction of methane in undisturbed coal beds is present in the condensed latent state, so that methane evolution from coal may be not always quantitatively predicted reliably. On the basis of experimental data, an equation expressing the amount of gas hydrate through the sorption capacity and actual humidity of coal is obtained. Analysis showed that the gradient of gas pressure in the marginal zone of a coal bed is linearly dependent on the saturation of the pore space with the hydrate. The high gradient of gas pressure and high gas content of coal beds along with local disruption of coal and re-distribution of rock pressure are the major factors causing instantaneous outbursts of coal and gas.

Highlights

Sudden outburst of coal and gas is a complex multifactorial process, and its description within the known physical models is rather complicated [1,2,3,4]
The potential energy realized during a sudden outburst of coal and gas is formed in the elastic deformations of coal bed and host rocks, as well as in coal methane which is under high pressure
In the present work we discuss the results of experiments on the measurement of the amount of gas hydrate in natural coal with different degree of metamorphism, and estimate the effect of gas evolved during the decomposition of the gas hydrate on the gradient of gas pressure in the marginal zone of the coal bed

Summary

Introduction

Sudden outburst of coal and gas is a complex multifactorial process, and its description within the known physical models is rather complicated [1,2,3,4]. To take into account the integrated action of the formation pressure, elastic deformations of the bed, gas content etc., each of the parameters is expressed through the forces accompanying or preventing the outburst or through the accumulated elastic energy and the work necessary for the destruction of coal and its transport into the mine [8,9,10,11]. The major contribution into the active forces accompanying a sudden outburst of coal and gas is made by the gradient of rock and gas pressure in the marginal zone of the bed. The potential energy realized during a sudden outburst of coal and gas is formed in the elastic deformations of coal bed and host rocks, as well as in coal methane which is under high pressure. The total amount of gas present in coal and the rate of initial gas evolution determine the danger of outburst from the marginal zone, so it becomes urgent to study the forms connecting coal methane with the solid substance of coal [8,9, 12,13]

Materials and Methods

Results and discussion

Conclusions