变渗透率条件下煤层气井的产能预测

煤层气储集特征、渗流机理均不同于常规砂岩气藏，导致产能评价难度较大。引入煤层气多组分的基质收缩效应，建立了近井地带紊流效应影响下的二项式产能模型，并进行了实际单井的应用及分析。结果表明:煤储层渗透率受到应力形变和基质收缩效应的双重影响，呈现先下降后上升的特征，且杂质气体含量越高，煤层渗透率恢复程度越弱。实际应用证明采用变渗透率的产能模型可对常规方法无法解释的煤层气井测试数据进行解释，解释结果能用于准确评价煤层气井的产能。 

Prediction of CBM well productivity under variable permeability

The accumulation characteristics and the percolation mechanism of CBM reservoir are different from those of conventional sandstone gas reservoir, resulting in big difficuty in productivity evaluation. The conclusion of investigation indicated that all previous researches have used material balance method or numerical simulation to predict the productivity. This paper builds up binomial deliverability model under the effects of turbulence by introdicing matrix shrinkage of multi-components of CBM, applied and analized the model in actual single well. The research results prove that coal reservoir permeability is affected by stress deformation and matrix shrinkage, decreases at beginning and increases later. And coalbed permeability recovery will be weakened more with higher impure content. Actual application demonstrated that productivity model for variable permeability can interpret well test data that conventional methods can't explain, the interpretation results can precisely assess the productivity of a CBM well.