关键词: 渤南洼陷, 古近系, 碎屑岩储集层, 黏土矿物, 垂向演化序列, 油气聚集

Abstract:

The characteristics of clay mineral in the Paleogene clastic reservoir of Bonan Sag were revealed by core observation, thin-section analysis, scan electricity microscope observation, X-ray analysis, physical property and oil-bearing level analysis.According to different types of clay minerals from bottom to top, the vertical sequence of clay mineral could be divided into 3 layers. Illite and chlorite are abundant at bottom layer, kaolinite is abundant in middle layer,and illite and illite-smectite mixed layer are abundant in the upper layer. The diagenetic evolution of clay mineral could be divided into 4 stages. In the sedimentary stage, sedimentary environments controlled the evolution of clay mineral,illite-smectite mixed layers and illite dominated the clay fraction composition. In the organic matter maturity stage, the evolution of clay mineral was influenced by diagenesis. In the tectonic activity stage, the evolution of clay mineral was influenced by hydrocarbon emplacement and deep fluid. In the oil-gas accumulation stage, the evolution of clay mineral was influenced by diagenesis, hydrocarbon emplacement, abnormally high pressure and deep fluid. Kaolinite in oil layer was protected, but kaolinite was changed into other clay mineral out of oil layer. High-content kaolinite zones correspond to oil layer. The total amount of clay mineral controls the type of reservoir spacing. The abnormally high-content kaolinite zone is an obvious index of oil-gas layer.

Key words: Bonan Sag, Paleogene, clastic reservoir, clay mineral, vertical evolution sequence, oil-gas accumulation