黔北地区龙马溪组页岩裂缝发育特征及地质意义

Fracture development characteristics and geological significance of Longmaxi Formation shale in northern Guizhou

谷阳,徐晟,张炜,徐佳佳,翟中杨

中国地质调查局地学文献中心，北京 100083 中国地质图书馆，北京 100083 中国石油华北油田分公司第四采油厂，河北 廊坊 062550

Geoscience Documentation Center, CGS, Beijing 100083, China National Geological Library of China, Beijing 100083, China No.4 Oil Production Plant, Huabei Oilfield Company, PetroChina, Langfang 062550, China

天然裂缝的发育不但改善了页岩储层的储集品质，也为开发阶段水力压裂形成大规模的缝网提供了有利条件。以黔北地区凤冈区块下志留统龙马溪组页岩为例，通过野外露头观测、岩心裂缝统计、含气性分析等方法，深入分析了研究区宏观裂缝发育特征和页岩气保存条件。结果表明：龙马溪组页岩裂缝类型以构造裂缝为主；根据构造应力强弱、构造变形样式及裂缝发育类型等特征，将研究区构造保存有利区进一步划分为稳定区和弱变形区，稳定区地层变形较弱，构造主体为宽缓背斜和紧闭向斜，断裂不发育，裂缝多以非构造裂缝为主，致使页岩气自封闭性良好，有利气体富集，是页岩气保存的有利区。分析裂缝与含气量关系发现，龙马溪组页岩储层中裂缝发育程度和含气量有着良好的对应关系。

The development of natural fractures not only improves the reservoir quality of shale reservoir, but also provides favorable conditions for the formation of large-scale fracture network in the development stage of hydraulic fracturing. Taking Longmaxi shale of Lower Silurian in Fenggang Block of northern Guizhou as an example, through the methods of outcrop observation, core fracture statistics and gas bearing analysis, the macro fracture development characteristics and shale gas preservation conditions in the study area are analyzed in depth. The results show that the fracture types of Longmaxi shale are mainly structural fractures. According to the characteristics of structural stress, structural deformation pattern and fracture development type, the study area is further divided into stable area and weak deformation area. In the stable area, the formation deformation is relatively weak, the main structure is wide and gentle anticline and tight syncline, the fault is not developed, and the fracture is mainly non structural fracture, resulting in good self sealing of shale gas and favorable gas enrichment, which is a favorable area for shale gas preservation. By analyzing the relationship between fracture and gas bearing property, it is found that there is a good corresponding relationship between fracture development degree and gas bearing property in Longmaxi Formation shale.

10.6056/dkyqt202106003