煤层割理的形成机理及在煤层气勘探开发评价中的意义

MECHANISM OF COALBED CLEAT AND INS SIGNIFICANCE IN EVALUATION OF COALBED METHANE EXPLORATION AND DEVELOPMENT

在系统研究鄂尔多斯东缘晚古生代煤层割理的基础上，结合煤化作用和油气生成研究新成果，对煤层割理的形成机理进行了探讨。认为割理是煤化作用过程中，煤因生成水、烃及其它气体而产生收缩内应力和高孔隙流体压力，当其超过煤的力学强度时，致使煤发生张性破裂而形成。割理的原始走向受割理形成时期的古地应力场控制。进而指出中变质光亮煤和半亮煤中割理最发育，因此这些煤层分布区是煤层气勘探开发的优选靶区。

This paper discussed the mechanism of coalbed cleat formation, basing on thesystematic studies of the coalbed cleat of the late Paleozoic coal seams in the eastern marginof ordos and the recent results of the study of coalification and hydrocarbon generation. It issuggested that cleats are extensional fractures in coal seams and formed by the contractioninner stress and the high porosity pressure,which are resulted from the water,hydrocarbonand other gases generations of coals in coalification process,The primary strikes of coalbedcleats are controlled by the paleo-stress field.It is also proposed that the cleats were welldeveloped in bright and semi-bright coals and the areas where bright and semi-bright coalsoccur are the favourable targets for the exploration and development of coalbed methane.