EFFECT OF COAL METAMORPHISM ON METHANE CONTENT AND PERMEABILITY OF COAL IN NORTH CHINA
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摘要: 通过华北和美国煤层气地质条件的对比, 基于华北煤变质特点, 指出了区域岩浆热变质有利于提高煤层含气量和渗透率, 并对其作用机理进行了初步探讨.在中国, 经受燕山期岩浆侵入影响之前的煤级较低, 因此在快速增温的高温作用下, 煤层气再次发生即“叠加生烃”或“叠加成气”的潜力大, 孔、裂隙系统发育更趋完善, 区域岩浆热变质的生气时间晚而利于煤层气保存.叠加有区域岩浆热变质形成的煤级分带, 包括高煤级煤和中煤级煤在内都将明显提高煤的含气量和渗透率, 因此, 华北地区应重视在区域岩浆热变质煤中寻找煤层气勘探目标.Abstract: The contrast in geological conditions for the coalbed methane between North China and United States indicates that the telemagmatic thermal metamorphism is favorable for the increase of the coalbed methane volume and permeability characteristic of coal metamorphism in North China. Additionally, the mechanism of the telemagmatic thermal metamorphism is discussed in this paper. The majority of coals in North China were ranked in the low level before the intrusion of Yanshanian magma. Therefore, at the high temperature caused by the rapid increase of the temperature, the coalbed methane occurred the second time. That is to say the coalbed was of great potential to the "superimposed hydrocarbon generation" or "superimposed coalbed-methane generation". The porosity and fissure system turned more developed. Moreover, the late generation of the coalbed methane derived from the telemagmatic thermal metamorphism favored the reservation of the coalbed methane. The coal-rank zonings superimposed by the telemagmatic thermal metamorphism, including high-rank and middle-rank coals, increase distinctively the methane content and the permeability. Therefore, special attention should be paid to the location of the coalbed-methane prospecting target in the telemagmatic thermal metamorphic coals.
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Key words:
- coalbed methane /
- coal metamorphism /
- methane content /
- permeability /
- North China
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图版Ⅰ 热压处理煤和区域岩浆热变质的气孔构造
1 长焰煤, 加热300 ℃, 油浸反光, 320 ×;
2 肥煤, 加热300 ℃, 油浸反光, 320 ×;
3 长焰煤, 加热450 ℃, 油浸反光, 320 ×;
4 气煤, 加热400 ℃, 油浸反光, 320 ×;
5 荥巩煤田无烟煤, 油浸反光, 190 ×;
6 荥巩煤田无烟煤, 油浸反光, 204 ×;
7 永夏煤田天然焦, 油浸反光, 360 ×.表 1 一些煤田(矿区) 煤变质程度、含气量与渗透率
Table 1. Variations of coal rank, methane content and permeability in some coalfield (mining)
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