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EXPERIENCE OF D. HOUSKNEСHT DIAGRAM FOR IMPACT ASSESMENT OF CONSOLIDATION AND CEMENTATION ON POROSITY OF THE LOWER-MIDDLE JURASSIC SANDSTONES OF THE NYUROLKA DEPRESSION AND THE KOLTOGOR-URENGOY MEGATROUGH

E. A. Predtechenskaya

Siberian reseatch Institut of Geology, Geophysics and Mineral Resources, Novosibirsk, Russia

Using D. U. Hausknecht diagram, the degree of impact of authigenic cementation, pressure solution and mechanical consolidation on the reduction of porosity and intergranular volume of the Lower - Middle Jurassic sandstones in the territory of the Tomsk region was determined. Sandstones of the Nadoyakha (Lower Toarcian – Lower Aalenian, bed Yu15), Vymskoye (Lower Bajocian, beds Yu11–Yu14), Leontievskiy (Lower-Upper Bajocian, beds Yu8–Yu10) and Malyshevka (Upper Bajocian – Bathonian, beds Yu3–Yu6) were analyzed horizons penetrated by a number of wells in western regions of the Nyurolka depression and the southern part of the Koltogor-Urengoy megatrough in the depth interval 2702–3326 m. It was found that the reduction in the intergranular volume of studied rocks is associated not only with their genesis, material composition, and structural and textural features, but also with the amount, type and composition of cement. It was revealed that the main factor influencing the reduction of the primary volume of the pore space of terrigenous rocks to a depth of ~ 2900–3000 m is the authigenic cementation, and below 3000 m the leading role is played by mechanical consolidation and dissolution of detrital grains under pressure. For Late Toarсian-Aalenian sandstones in the studied areas, the contribution of the factor of mechanical consolidation and pressure solution on the reduction of the primary intergranular volume was 38–53%, and for sandstones of the Bajocian – 20–30%. For the latter, the share of authigenic cementation was 24–56%. The work also considers circumstances that limit this method and possibilities of its application for other types of rocks.

Keywords: consolidation, cementation, pressure solution, porosity, intergranular volume, hydrocarbon reservoirs, sandstones, Lower-Middle Jurassic, Western Siberia.

DOI 10.20403/2078-0575-2020-3-30-42