页岩气田储层含气性测井评价——以四川盆地涪陵页岩气田J区块为例

Gasbearing property evaluation by petrophysical logging in shale gas reservoirs:a case study in J area of Fuling shale gas field,Sichuan Basin

页岩储层岩性较复杂、储集空间类型多样,现有的含气性测井综合评价方法体系还不够完善。为深化四川盆地涪陵页岩气田J区块页岩储层含气性评价认识,应用密度—中子叠合法、自然伽马—去铀伽马叠合法、铀—钍比值法开展含气储层定性识别,并对吸附气、游离气、孔隙度、含气饱和度等含气性参数进行了测井定量预测研究。在多参数对比研究的基础上,优选了有机碳含量、孔隙度、含气饱和度、硅质含量、埋深为影响含气性测井评价参数,采用灰色关联分析法构建出储层含气性测井评价指数GQ,建立了含气性评价标准,即Ⅰ类含气储层GQ≥0.57,Ⅱ类含气储层0.37<GQ<0.57,Ⅲ类含气储层GQ≤0.37。该方法应用于J区块表明,含气性参数定量预测模型精度较高,且含气性评价标准可以对储层含气性进行有效的评价和分类,具有很好的推广前景。

The lithology of shale reservoirs is complex and the types of storage porosity are diverse.The existing gasbearing property evaluation system by petrophysical logging is not perfect.In order to deepen the understanding of the gasbearing capacity evaluation of shale reservoirs in J area of the Fuling shale gas field in the Sichuan Basin,the density-neutron curve superposition method,natural gamma-deuranium gamma curve superposition method,and uranium-thorium ratio method are applied in qualitative recognition.Quantitative logging research was carried out on gasbearing parameters such as adsorbed gas,free gas,porosity,and gas saturation.Based on the multiparameter comparative study,organic carbon content,porosity,gas saturation,siliceous content,and burial depth are selected as the logging evaluation parameters that affect gasbearing properties.A logging evaluation index(GQ)for gasbearing capacity is constructed using fuzzy correlation analysis.The gasbearing evaluation criterion is established,that is,GQ≥0.57 for typeⅠgasbearing reservoirs,0.37<GQ<0.57 for typeⅡgasbearing reservoirs,and GQ≤0.37 for typeⅢgasbearing reservoirs.The application of this method in J area shows that the accuracy of the quantitative prediction model for gasbearing parameters is high,and the gasbearing evaluation criteria can effectively evaluate and classify the gasbearing properties of the reservoir.