But it will fail to recognize the gas bearing bed buried deeper by the two methods as its porosity log feature is not obvious, especially when density porosity is lower than neutron porosity.

但是，对埋藏较深的气层而言，由于其孔隙度曲线特征并不明显，故用常规方法识别十分困难，特别是当密度孔隙低于中子孔隙度时，上述两方法识别气层均失败。

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The porosity and permeability of coal-bearing strata have important influence to the exhaust and mining of coal bed gas, but the production of coal bed gas is precondition of its richen.

煤系地层孔隙性和渗透率对煤层气的抽放、排采具有重要影响，但煤层气的生成却是其富集的先决条件。

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Experiments showed decreased porosity of the filter bed along the filtering direction.

试验发现，短纤维束滤料滤层的孔隙率沿过滤方向由大到小，为变孔隙滤层。

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