How laminae structure controls the storage of hydrocarbons in lacustrine shale: A perspective from micropore networks

Clarifying coupling among lamina structure， pore structure， and oil occurrence is essential for efficient subsurface resource development. Core， thin-section observations， SEM， MICP， N₂ adsorption， 2D-NMR tests and CMR-NG logging are used to conduct this research. Results show that laminated， layered， and massive structures correspond to distinct pore systems. Four lamina types (felsic， clay， carbonate， mixed) and five superimposition patterns (Types I-V) are identified， together with three pore-structure types (A， B， C). Layered， laminated， and massive structures correlate with types A， B， and C， respectively. Layered structure has the best reservoir quality; massive rocks are poorest. Clay laminae promote organic pore formation and high oil saturation during thermal evolution but reduce hydrocarbon mobility and degrade pore networks during diagenesis. Laminae control fluid occurrence， content， and distribution; laminated structure， felsic laminae， and Type I superimposition show optimal oil-bearing properties and mobility. Lamina-pore coupling controls hydrocarbon enrichment， migration， and source-reservoir assemblages. Laminated reservoirs with type B pore structure mainly produce shale gas (Type III kerogen) with unmigrated oil， while layered rocks with mature Type I kerogen have strong oil generation capacity， with oil expelled from large pores into adjacent brittle mineral laminae. These findings deepen the understanding of laminae-controlled oil distribution， and offer guidance for sweet spot exploration and development.