渝东南下志留统龙马溪组页岩矿物成分及脆性特征实验研究

水力压裂作业已被公认为实现页岩气工业开采的关键技术，压裂方案的设计离不开地层脆性特征分析。本文选取了渝东南龙马溪组露头页岩，从脆性角度对其压裂可行性进行了实验研究。结果显示：该区域页岩具有层理发育，致密、低孔、低渗等特点，具有储层改造的必要性；从矿物组分结果来看，龙马溪组页岩石英、碳酸盐等脆性矿物含量高，在49%-65%范围变化，平均含量为57%，粘土矿物含量低，同时不含强水化膨胀性的高岭土和蒙脱石；在此基础上，利用矿物成分及动态弹性参数计算得到的页岩脆性系数在49%-77%范围变化，平均值在57%以上，显示该地层脆性较好；与北美成功开采的储层数据对比，渝东南龙马溪组地层更适合压裂作业。根据北美页岩压裂实践经验，建议本区块页岩压裂设计中考虑到岩石脆性，选择液体用量多、支撑剂浓度低、支撑剂用量少的压裂液。

Experimental study of Mineral composition and Brittle characteristics in Longmaxi Formation of Lower Silurian, southeast Chongqing

Water fracturing has been recognized as the key technologies for commercial exploitation of the shale, and the fracturing design are based on the analysis of brittleness. This article studies Longmaxi exposures in southeast of Chongqing, and carries on experiments to analysis the feasibility of the fracturing from the aspect of brittleness. The results show that the shale is well bedded, tight, low porosity and low permeability in this area. And it needs to be reconstructed. The analysis of the mineral components shows that Longmaxi shale has a high content of brittle minerals, such as quartz and carbonate, and the content of these brittle minerals range from 49% to 65%, with an average of 57%. While the clay mineral content is low, and there is no kaolinite or montmorillonite which contain serious hydration expansion, on the basis of it .these, the shale brittleness coefficient calculated by the mineral composition and dynamic elastic parameters range from 49% to 77% and the average brittleness coefficient is higher than 57%, which shows the formation is brittle. Comparison with the successful exploitation of the North American shale reservoir, Longmaxi shale in southeast of Chongqing is fit to fracturing operations. According to the North American shale fracturing practical experience, we suggest that the rock brittleness should be taken into consideration in the fracturing design process, and the fracturing fluid should be with large volume of fluid, low proppant content and less proppant consuming.