STRUCTURAL AND LITHOLOGICAL TRAPS OF OIL AND GAS IN THE UPPER JURASSIC SEDIMENTS OF THE SREDNEVASYUGANSKY MEGASWELL

Abstract

Link for citation: Belozerov V.B. Structural and lithological traps of oil and gas in the Upper Jurassic sediments of the Srednevasyugansky megaswell. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 137-145. In Rus. Relevance. Industrial development of oil and gas-bearing territories, on the one hand, forms a developed oil production infrastructure, and on the other, depletes its oil and gas potential, as a result of which, after a certain period of time, the created infrastructure becomes unclaimed. For its effective use, it is necessary to constantly increase the mineral resource base of the territory. As a rule, at the first stage of prospecting and exploration, deposits of hydrocarbons of a structural type are identified and, as the geological and geophysical knowledge of the territory increases, the transition to the search for hydrocarbon deposits in complex traps is carried out. Preparation of structural and lithological search objects may also include several stages, depending on the detail of the study of the territory by seismic data. An example of such an approach is the sequence of prospecting and exploration work in the sediments of the Vasyugan formation of the Kelloway-Oxford age of the Srnevasyugasnky megaswell in the southeastern part of Western Siberia. At the first stage (until 1989), a number of structural and lithological traps were identified in the oil-prospective Upper Oxfordian reservoir Yu1/1 on the basis of seismogeological analysis of drilling data and wave characteristics of the time interval of seismic horizons IIa-Ib, reflecting the structure of the Vasyugan formation. Subsequent exploratory drilling was carried out only within the previously discovered fields in order to prepare them for industrial development. As part of the second stage, on the basis of new seismic studies, the promising oil and gas zone associated with traps of structural-lithological type was expanded. At the same time, the criteria for predicting the development zone of the reservoir Y1/1 were justified by two-dimensional seismogeological modeling. This made it possible to compare and combine the results of the seismogeological interpretation performed at the first and second stages. In addition, the analysis of the results of deep drilling carried out during the additional exploration of fields showed the reliability of a number of forecast oil and gas zones allocated at the first stage, which implies purposeful drilling within the allocated non-anticlinal search facilities. Taking into account the developed oil production infrastructure of the territory under consideration, their development will significantly increase its hydrocarbon potential. The object is the terrigenous deposits of the Kelloway-Oxford of the Vasyuga formation within the eastern slope of the Srednevasyugansky megaswell. The method is two-dimensional seismogeological modeling when evaluating the forecast criteria for the development zone of the productive reservoir Yu1/1 according to seismic data. Results. The criteria for predicting the development zone of the Yu1/1 formation are determined on the basis of two-dimensional seismogeological modeling. New non-anticline oil-prospective facilities were prepared. According to the drilling results, the productivity of a number of previously allocated oil-prospective sites was confirmed. The prospects of filling the allocated structural and lithological objects with coal-bearing plants are estimated based on the analysis of the value of the generation potential of the Bazhenov formation within the development zone of the Yu1/1 formation.