湖南常德地区牛蹄塘组页岩特征及含气性

Characteristics of Shale and Gas Content of Niutitang Formation in Changde Region of Hunan Province

下寒武统牛蹄塘组是常德地区重要的页岩气勘探层位之一,岩石类型主要为富炭硅质页岩、炭质页岩和石煤。以单井地质分析为基础,结合区域地质和露头资料,对常德地区牛蹄塘组黑色页岩有机地球化学、岩矿组成、储集空间类型、力学性质、含气性等进行了研究。该区牛蹄塘组地层相对稳定、分布范围广、页岩厚度大、有机碳含量高、有机质类型好、热演化程度高,孔隙和微裂缝发育,比表面积大、吸附气能力强,脆性矿物含量较高,具备良好的可压裂性。CY1井揭示牛蹄塘组页岩厚度大,含气量达到0.5~2.1m3/t,具有良好的储集条件。综合研究认为常德地区牛蹄塘组具有较好的页岩气勘探潜力。

The Lower Cambrian Niutitang Formation in Changde region of Hunan Province is regarded as an important shale gas exploration layer. The Niutitang Formation is mainly composed of carbon-enriched sili- ceous shale, carbonaceous shale and stone coal. Based on the observation of field outcrops, well cores and regional geology data, integrating with analysis of rock organic geochemistry, mineral content, reservoir space type, physical mechanical properties and gas content, the features of shale in Niutitang Formation are studied in detail. The results indicate that shale in the Niutitang Formation is characterized by stable thick- ness and wide distribution areas, high organic carbon content, high levels of thermal evolution, large specific surface area with micro pore and fracture, and good gas adsorption ability. The mineral composition is dom- inantly clastic quartz and clay minerals, with feldspar, calcite, dolomite, pyrite and so on. The shale reservoir with high brittle mineral is easy to fracture. The shale real thickness of CY1 well is more than 310m,and the gas content is 0.5-2. lm3/t. It shows good reservoir conditions. The comprehensive evaluations by this paper indicate that this area has good shale gas exploration prospect.