A series of qualitative descriptions and quantitative analyses was used to determine the lithofacies characteristics and recognize the favorable shale intervals of Dawuba Formation in the Ziyun area of South Qian Depression. The qualitative descriptions include core description and scanning electron microscope (SEM) observation. The quantitative analyses include X-ray diffraction, total organic content analysis, vitrinite reflectance, maceral composition, porosity, and permeability, as well as gas and element composition. The Dawuba Formation could be divided into four members. In general, the shale in the first and third members showed similarly high organic matter content with most samples in range of 2–2.5% and higher brittle mineral content with a content of quartz 40.53% and 33.21%, respectively, compared with the other two members, as well as high gas content. However, the first member shale samples exhibited much higher porosity and permeability than the third member shale samples. Furthermore, the shale gas in the first member was chiefly composed of methane (average: 83.63%), while that in the third member mainly consisted of nitrogen (average: 79.92%). Hence, the first member should be regarded as the most favorable target.

中文翻译：

---

黔南坳陷紫云地区大乌坝组页岩气有利层段评价

通过一系列定性描述和定量分析，确定了南黔南坳陷紫云地区大乌坝组的岩相特征和有利页岩层段。定性描述包括岩心描述和扫描电子显微镜（SEM）观察。定量分析包括 X 射线衍射、总有机物含量分析、镜质体反射率、微晶成分、孔隙度和渗透率，以及气体和元素组成。大乌巴组可分为四段。总体上，一、三段页岩有机质含量较高，大部分样品在 2-2.5% 之间，脆性矿物含量较高，石英含量分别为 40.53% 和 33.21%。会员，以及高含气量。然而，第一段页岩样品表现出比第三段页岩样品高得多的孔隙度和渗透率。此外，一段页岩气以甲烷为主（平均83.63%），三段页岩气以氮为主（平均79.92%）。因此，第一个成员应该被视为最有利的目标。