Abstract:

Carbonate laminae in saline lacustrine shale sequences are widely developed, and their diverse combinations and spatial stacking patterns represent a key geological factor controlling the differential enrichment of lacustrine shale oil. These laminae, composed of micro- to millimeter-scale thin layers of minerals such as calcite and dolomite, serve as preferred targets for saline lacustrine shale oil “sweet spots” due to their significant economic potential and development prospects. The laminae exhibit various structures, including cryptocrystalline, sparitic, and fibrous structures, which originate from diverse formation mechanisms—mechanical, physicochemical, and biochemical processes—leading to distinct mineralogical and structural heterogeneities. In terms of pore-fracture systems, carbonate laminae develop advantageous pore types such as intercrystalline, dissolved, and intergranular pores. Their high brittleness promotes the formation of heterogeneous fracture networks, including bedding-parallel and structural fractures. During diagenesis, organic acid dissolution and recrystallization further enhance pore connectivity, significantly improving in storage capacity and permeability. This facilitates the micro-migration and enrichment of light hydrocarbons within the laminae, forming movable oil. The control of carbonate laminae on shale oil sweet spots is manifested in four aspects: extensive distribution facilitates segmental and areal sweet spot development; high organic matter content provides the material basis for hydrocarbon generation; high-quality source-reservoir configurations promote near-source migration and enrichment; high brittleness enhances reservoir fracability and development potential. In conclusion, detailed study of carbonate laminae provides critical guidance for shale oil exploration and sweet spot prediction in saline lacustrine basins.

Key words: saline lacustrine basins, carbonate laminae, lacustrine shale, shale oil, ‘sweet spots’

摘要：

碳酸盐质纹层在咸化湖盆页岩层系中广泛发育，其多类型组合与空间叠置模式是控制陆相页岩油差异富集的关键地质因素之一。碳酸盐质纹层是由方解石、白云石等矿物组成的微米~毫米级薄层结构。研究表明，富含碳酸盐质纹层的页岩层段是页岩油“甜点”的优选目标，具备良好的经济开采价值和开发潜力。碳酸盐质纹层主要包括隐晶、亮晶及纤维状结构。其形成机制多样，包括机械物理、电化学以及生物化学成因机制，这些机制导致纹层在矿物成分和结构上呈现分异性。在孔缝系统方面，碳酸盐质纹层发育晶间孔、溶蚀孔和粒间孔等优势孔隙类型，同时因脆性较高易形成层理缝、构造裂缝等非均质裂缝网络。成岩演化过程中，有机酸溶蚀和重结晶作用进一步优化了孔隙连通性，显著提升了储层的储集空间和渗透能力，促进轻质烃类通过微运移在碳酸盐质纹层中富集形成可动油。碳酸盐质纹层对页岩油甜点的控制主要体现在4个方面：广泛分布性利于甜点呈段状、区带状分布；高有机质含量提供生烃物质基础；优质源-储组合促进近源运移与富集；高脆性特征增强储层可压裂性，提高开发潜力。碳酸盐质纹层的精细研究为咸化湖盆页岩油勘探与甜点预测提供参考。

关键词: 咸化湖盆, 碳酸盐质纹层, 陆相页岩, 页岩油, “甜点”

CLC Number: 

• P618.13

• TE122