Abstract:

In order to explore the influence of basalt eruption on reservoir diagenesis in Huanghekou sag, clay mineral, zeolite and trace elements in the Laibei slope zone were studied to make it clear that the pore fluid changes in different formation of Paleogene and then to establish the reservoir diagenesis and pore evolution model in igneous rocks area. In the period of the first and second members of the Shahejie Formation, under the influence of alkaline water medium formed in the small-scale basalt eruption environment and arid-semiarid climate, albitization and carbonate cementation developed universally and dolomite coat grew on grain surface, also we can see the phenomena of quartz dissolution. In the third member of the Dongying Formation, the delta reservoir was influenced by the brine precipitation in dark mudstones of the first member of Shahejie Formation and terrestrial freshwater input, also late rich mafic pore water mixing effect, so the main diagenesis are zeolite dissolution, clay mineral transformation and albitization in alkalescence water medium conditions. In the period of the first and second members of the Dongying Formation, it is characterized by extensive eruption basalt, strong hydrolysis of minerals rich in iron and magnesium element which led to the pore fluid rich in mafic, and the precipitation and dissolution of low silica zeolite. The local precipitate and dissolution of zeolite and “I-shaped” framework associated with basalt eruption is in favour of sandstone pore preservation of Dongying Formation. During the deposition of the first and second members of Shahejie Formation, pectinate dolomite coat which inhibited the quartz overgrowth under the alkaline water medium and the phenomena of quartz dissolution is beneficial to the preservation of the sandstone pore.

Key words: pore fluid, diagenesis, controlling factor of reservoir quality, basalt