煤类 meaning in English

coal types

First of all , the substance foundation of low - rank coal cbm generation in the basin has been discussed according to the development of coal reservoir , coal petrography , coal properties , coal rank , coal genera , coal facies feature of lower jurassic badaowan formation ( jlb ) and middle jurassic xishanyao formation ( j2x )
首先，根据下侏罗统八道湾组( j _ 1b )和中侏罗统西山窑组( j _ 2x )煤储层发育、煤岩、煤质、煤级、煤类、煤相地质特征论述了本区低煤级煤层气生成的物质基础。