淮南煤田构造热演化特征与煤层气资源的初步研究

PRELIMINARY STUDY OF TECTONO-THERMAL EVOLUTION CHRACTERISTICS AND COALBED METHANE RESOURCE IN HUAINAN COALFIELD

本文应用磷灰石裂变径迹法研究淮南煤田的构造热演化特征 ,探讨其煤层气资源潜力。结果表明 :研究区自晚古生代以来 ,至少发生过三次明显的构造热事件 ,分别在 2 40 ,1 40和 80Ma左右 ;古地温梯度比现地温梯度低 ,估计本区整个剥蚀厚度大于 2 0 0 0m。从该区的构造热演化特征可以得出以下初步结论 :该区煤化作用主要发生在 2 40～ 1 40Ma之间 ,即中生代以来的第一、二次构造热事件使晚古生代煤逐渐变质为气煤级 ,少部分达肥煤级。煤层气生气量不是太高 ,白垩纪晚期的构造热运动导致热成因煤层气逸失 ,构造发育的地区逸失较多 ,煤层气资源潜力可能不大 ;构造不发育的地区逸失较少 ,可能是煤层气开发较为有利的地区。

This paper studies tectono thermal evolution characteristics and coalbed methane resource in the Huainan coalfield by fission track analysis.The results show that:① at least three thermal events have occurred since Late Paleozoic at about 240,140 and 80 Ma, respectively;②paleo geothermal gradient was higher than that at the present.The study estimated that denudation thickness of the area was more than 2000 meters. On the basis of the characteristics of tectono thermal evolution of the Huainan coalfield, the preliminary conclusions will be drawn as follows: the first and second tectono thermal events happened at 240～140 Ma during the Mesozoic, so that most of the coal formed in Late Paleozoic was gradually metamorphosed into gaseous one and a minor amount of it into fat coal. Production of coalbed methane was not too much, and the tectono thermal events in the Late Cretaceous led to the release of coalbed methane into the sky. In general, more gas will release from the regions where structures are better developed than that from the regions lacking structures, which may be suitable for the development of coalbed methane. This method may be applicable to coalbed methane exploration and development.