桂中坳陷南丹地区中—下泥盆统塘丁组富有机质页岩储层特征

Characteristics of Tangding Formation organic-rich shale in Nandan area, Guizhong Depression

滇黔桂盆地桂中坳陷南丹地区泥盆系页岩特征研究较少。为了进一步评价该地区下—中泥盆统塘丁组页岩气勘探前景,以野外露头剖面观察和钻井资料为基础,结合薄片鉴定,对该地区泥盆系页岩特征进行了研究。结果表明:(1)桂中坳陷泥盆纪广泛海侵和陆内裂陷使该地区发展成为"台—盆相间"格局,台盆环境发育大量页岩和碳质泥岩,其中塘丁组为一套黑色、深灰色、灰黑色泥页岩沉积,具有页岩气开发潜力;(2)塘丁组泥页岩厚度大,有机质丰度高(有机碳含量介于0.38%~4.21%),成熟度介于1.5%~3.6%,储层微孔隙发育,脆性矿物含量适中(介于44%~76%),具备形成页岩气的资源基础和成藏条件;(3)南丹地区塘丁组发育有连续且具一定厚度的页岩地层,其地化特征、物性特征及沉积厚度可与北美及四川页岩气储层对比。结论认为该区塘丁组页岩具有较好的页岩气勘探潜力,塘丁组上段页岩气开发潜力好于下段。

The characteristics of Devonian shale in the Nandan area of Guizhong Depression are less studied. In order to further evaluate the shale gas exploration potential of Tangding Formation, Lower-Middle Devonian in this area, the characteristics of Devonian shale in the Nandan area of Guizhong Depression were studied in this paper based on outcrop section observation and drilling data, combined with thin section analysis. It is shown that the ＂platform-basin＂ alternative pattern is developed in Nandan area due to Devonian extensive transgression and intracontinental rift in the Guizhong Depression. A great amount of shale and carbonaceous mudstone is developed in platform-basin environment. The Tangding Formation is a set of black, dark gray and gray black mud shale deposits, and it has the development potential of shale gas. The Tangding Formation mud shale is characterized by large thickness, high abundance of organic matter （TOC 0.38% -- 4.21%）, higher maturity （1.5% -- 3.6%）, presence of reservoir micropores and moderate brittle mineral content （44% - 76%）, so it provides the resource base and accumulation conditions of shale gas. In the Nandan area, shale strata are developed continuously with a certain thickness. Compared with the shale gas in North America and Sichuan from the aspects of geochemistry, physical property and sedimentary thickness, the Tangding Formation shale gas in the Nandan area is better in shale gas exploration potential. It is indicated that the shale gas development potential of the upper member of Tangding Formation is better than that of the lower member.