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Abstract

UDC: 550.83.053:553.98(571.5)

GRAVITY-STRUCTURAL MAPS AS NEW TOOL TO ANALYSE TGE SIBERIAN PLATFORM BEDDED-BLOCK STRUCTURE

S. M. Makeev, A. E. Anufriev

Relying on the fact that many traps are connected with deep Upper-Proterozoic deposits of the Siberian Platform, the assumption that reservoir properties of rocks at low depths and throughout a long geologic time can remain only if these rocks possess positive excess density in relation to their host medium is made. Furthermore, making a start from a well-known correlation between seismic wave velocities and rock densities, the paper states that favorable for hydrocarbon accumulations anticlinal domes, with rather dense rocks as their roofs, have to be followed by a positive gravitational effect besides seismic-structural anomalies. For verification of this statement, geological information contents of seismic-structural and gravity-structural maps of two joined areas promising for gas have been compared. It is shown that the gravity-structural map constructed by means of an original method of frequency-azimuth analysis reflects not only seismic-structural domes themselves, but also extended zones, “containing” these domes, probably of seismic-tectonic compaction of rocks. The conclusion regarding prospects of such zones on detecting fractured-type reservoirs and the need for integrating seismic exploration and non seismic methods to improve efficiency of prospecting for hydrocarbons in difficult conditions of the Siberian Platform bedded-block structure is drawn.

Key words: gravity-structural map, frequency-azimuth analysis, seismic-tectonic compaction, fracturedtype reservoirs, bedded-block structure, estimation of oil-and-gas content.

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