Occurrence Mechanism and Risk Assessment of Dynamic of Coal and Rock Disasters in the Low-Temperature Oxidation Process of a Coal-Bed Methane Reservoir

Abstract

The aim of this research is to explore the occurrence mechanism of dynamic disasters of coal and rocks in low-temperature oxidation of coal-bed methane (CBM) reservoirs. For this purpose, the occurrence probability of dynamic disasters at different oxidizing temperatures was assessed by using the comprehensive predictive index K for dynamic disasters involving coal and rocks. By employing nuclear magnetic resonance (NMR) technology, the evolution law of diameter and quantity of pores inside coal was detected during low-temperature oxidation of coal masses. In addition, fracture development of coal masses was monitored and analyzed by applying various instruments, including an instrument for measuring ΔP, hardness tester, gas chromatograph, and measuring system for rocks using the P-wave. The results showed that both the diameter and quantity of pores inside coal increased with the rise of the oxidizing temperature of the coal masses: the porosity increased by 72.2% as the temperature rose by 200 °C. The gas chromatograph and industrial analytical experiment proved that the whole fracture development process of coal masses was divided into two stages during low-temperature oxidation. In the initial stage of low-temperature oxidation (30–130 °C), water inside coal masses was lost and evaporated, resulting in the expansion and connection of micropores to mesopores. In the later period of low-temperature oxidation (130–230 °C), mesopores expanded and connected to macropores and microfractures because of oxygenolysis of the macromolecules and volatiles in coal. On the basis of the comprehensive predictive index K for dynamic coal disasters, the occurrence probability of dynamic disasters in low-temperature oxidation of CBM reservoirs was verified to increase with the increasing oxidizing temperature according to the measured data. In addition, the maximum allowable oxidizing temperature of the CBM reservoir where the specimen was collected was 130 °C.

Experimental Study on Electric Potential Response Characteristics of Gas-Bearing Coal During Deformation and Fracturing Process

“…(5) Experimental parameters were set. (6) The load was applied on the specimen by using the press to further synchronously measure various data such as EP and AE. (7) After the specimen was damaged, the experiment was ended and gas in the gas cylinder was released.…”

“…For example, in 2014, a coal burst damaged mine equipment seriously and resulted in the death of two miners in the Austar coal mine in Australia [5]. Therefore, the research on revealing the initiation and generation mechanism of coal and gas outburst disasters is of great significance for monitoring the stability of coal-rock mass while mining, and predicting the generation of coal and gas outburst disaster [6].…”

“…For example, in 2014, a coal burst damaged mine equipment seriously and resulted in the death of two miners in the Austar coal mine in Australia [5]. Therefore, the research on revealing the initiation and generation mechanism of coal and gas outburst disasters is of great significance for monitoring the stability of coal-rock mass while mining, and predicting the generation of coal and gas outburst disaster [6].Under the combined effect of ground stress, mining-induced stress, and gas pressure, the internal damage of coal-rock mass constantly changes to finally trigger structural instability and dynamic failure, which causes the coal and gas outburst disaster [7]. Monitoring the stress state and damage-evolution process of coal-rock mass is the key to monitoring and early-warning of coal and rock outburst disasters [8].…”

Development, Status, and Prospects of Coal Tar Hydrogenation Technology

“…The liquid products are separated into liquefied gas, naphtha, and diesel fractions by uisng a distilling apparatus. Tail oil from the bottom of the distilling apparatus is recycled into the hydrogenation reactor …”

Three‐dimensional characterization of open and closed coal nanopores based on a multi‐scale analysis including CO2 adsorption, mercury intrusion, low‐temperature nitrogen adsorption, and small‐angle X‐ray scattering

“…In addition, coal resources in the deeper strata have been exploited. Nearly half of the coalmines in China have become high gas mines with abundant coalbed methane (CBM) resources in their coal reservoirs …”