黔东北铜仁地区牛蹄塘组烃源岩成熟度评价

Maturity Evaluation of Niutitang Formation Source Rocks in Tongren Area,Northeast Guizhou

为确定贵州黔东北铜仁地区寒武系牛蹄塘组页岩气勘探潜力,在X射线衍射实验基础上,采用沥青反射率法、伊利石结晶度法和激光拉曼光谱法,对黔铜地1井牛蹄塘组—变马冲组页岩进行成熟度测试。结果表明:黔铜地1井牛蹄塘组—变马冲组页岩缺乏镜质体,难以采用常规镜质体反射率对其成熟度进行评价;受沥青复杂成因及非均质性影响,采用沥青反射率法对页岩评价的效果欠佳;伊利石结晶度法只能给出大致范围,同时受黏土矿物影响,其误差也较大;激光拉曼光谱法受非均质性影响较小,且具有制样简单、无损检测等优势,是较为理想的测试手段;研究区牛蹄塘组黑色页岩等效镜质体反射率为3.41%~3.50%,属过成熟阶段晚期。

To determine the exploration potential of the shale gas in the Cambrian Niutitang formation in the Tongren area,northeast Gui-zhou,on the basis of X-ray diffraction experiments,the maturity of the shale of Niutitang formation-Bianmachong formation from Well QTD-1 was tested by using methods of bitumen reflectance,illite crystallinity and laser Raman spectroscopy.The results show that the shale of Niutitang formation-Bianmachong formation lacks vitrinite,making its maturity difficult to be evaluated using conventional vitrinite reflec-tance.The shale is not evaluated satisfactorily by using the reflectance of bitumen,due to its complex genesis and the impact of bitumen heterogeneity.The illite crystallinity method can only provide a rough range of maturity,with relatively large error due to the presence of clay minerals.In contrast,the laser Raman spectroscopy method is less affected by heterogeneity and has advantages such as simple sample preparation and non-destructive testing,which proves to be a more ideal testing approach.The equivalent vitrinite reflectance of the black shale of Niutitang formation in the study area ranges from 3.41%to 3.50%,indicating a late overmature stage.