页岩岩相的测井曲线识别方法——以焦石坝地区五峰组—龙马溪组为例

页岩岩相的识别是页岩气勘探开发的基础工作,不同类型页岩具有不同物质组分与组构,进而具有不同的脆性度和物性,目前利用测井曲线来识别页岩岩相的研究较为薄弱。以焦石坝地区五峰组—龙马溪组3口井的测井资料、岩心测试数据为基础,通过多参数优选、多元线性拟合,分别建立了黏土矿物、硅质矿物相对含量的预测方程,探讨利用测井曲线识别页岩的方法。结果表明:黏土质页岩具有高DEN,CNL,K,KTh,低U,U/Th的特征;混合质页岩具有中DEN,U,CNL,K,KTh,U/Th的特征;硅质页岩具有高U,U/TH,低DEN,CNL,K,KTh的特征,并以此为依据,建立了页岩岩相识别雷达图版,不同岩相所对应的测井曲线数值在图版中有不同的分布范围,该图版可以有效识别页岩岩相,并能够对预测方程识别错误的岩相进行纠正,预测结果与实测值吻合度高。将预测方程定量识别岩相和雷达图版定性识别岩相结合起来,通过双重约束,可以很好地识别焦石坝地区五峰组—龙马溪组页岩岩相。

Identification method of shale lithofacies by logging curves:a case study fromWufeng-Longmaxi Formation in Jiaoshiba area,SW China

Identification of shale lithofacies is the basis of shale gas exploration and development.Different types of shale have different material components and textures,and thus the brittleness and physical properties are different.At present,the study on shale lithofacies identification by logging curves is relatively weak.Based on logging data and core test data of three wells from Wufeng-Longmaxi Formation in Jiaoshiba area,through multi-parameter optimization and multivariate linear fitting,the prediction equations of relative content of clay minerals and siliceous minerals were established respectively,and the identification method of shale lithofacies by logging curves was discussed.The results show that argillaceous shale lithofacies has the characteristics of high DEN,CNL,K,KTh,and low U,U/Th,the mixed shale lithofacies has the characteristics of middle DEN,CNL,K,KTh,U,U/Th,and siliceous shale lithofacies has the characteristics of high U,U/Th and low DEN,CNL,K,KTh.Furthermore,a radar chart for shale facies identification was established.After corresponding processing,the logging curve values corresponding to different lithofacies have different distribution ranges in the chart.The chart can effectively identify shale lithofacies and correct the lithofacies identified by the prediction equation.The predicted results are in agreement with the measured values.Combining quantitative identification of lithofacies by prediction equation and qualitative identification of lithofacies by radar chart,shale lithofacies ofWufeng-Longmaxi Formation in Jiaoshiba area can be well identified through double constraints.