This reference is for an abstract only. A full paper was not submitted for this conference.


Oil and gas content in the Paleozoic superface under conditions of the West-Siberian plate is generally connected with Pre-Jurassic outcrop of carbonate or carbonate terrigenous units. This regularity is primarily caused by the ability of carbonate units to form reservoirs of high storage capacities. Reservoirs are formed by the action of secondary processes (fracturing, cavernosity, karstification) both at the stage of peneplain formation and during the Mesozoic period. A great number of hydrocarbon fields, confined to the disintegrated roof of those carbonate units, have been discovered all over the West Siberian plate. As a result, the detection and mapping of carbonate massifs outcropping in the Pre-Jurassic period or overlapped by thin effusive-sedimentary Triassic formations become extremely important. With this in mind we have used seismic tomography to interpret regional refraction observations.

In central West Siberia this method has made possible the reinterpretation of the first waves of regional seismic profiles more than 1 000 km in extent and about 80 000 km2 in area. In consequence of the reinterpretation of the first waves by seismic tomography we have got velocity sections of the shallowearth's crust down to depth of about 8 km. They allow us to determine large-scale features of the structure and composition of Paleozoic formations. We have identified two separate massifs of high-velocity (Vokt; 5800 m/sec)formations predicted as carbonate objects. Data from a number of deep wells drilled before in this area make the forecast of those massifs reliable.

All the revealed commercial hydrocarbon reservoirs in the Paleozoic superface occur within the Pre-Jurassic outcrop of high-velocity carbonate units. Their greatest amount is accumulated within the identified central carbonate massif.

The carried out investigations demonstrate that seismic tomography used for interpretation of the first waves of regional seismic observations is an effective method for detecting and forecasting carbonate massifs in Paleozoic deposits promising for oil and gas.

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