Influence of discontinuous faults in the Jurassic part of the section on the structure of the Urna oil reservoir in the Vasyugan formation of Malyka field

Abstract

In the East Uvat district of the South of Tyumen region, five fields were discovered, in which the bulk of hydrocarbon potential is in deposits in upper Jurassic sediments (U1 reservoir of the Vasyugan formation). A feature of the structure of deposits is the block structure of reservoirs, which is reflected in the presence of different levels of the oilwater contact within the same deposit. The construction of such models is complicated by two main reasons: the first is the presence of non-amplitude faults, which are difficult to map in the seismic 3D survey, the second is results of tracer studies, according to which not all faults have shielding properties. In the Eastern regions of Uvat, fault models of the Vasyugan formation are constructed in four stages: at the first stage, based on the 3D seismic data, a framework of small faults is identified, which at the second stage are consolidated into large faults. At the third stage, based on the analysis of tracer studies, they are ranked into permeable and impermeable. At the fourth stage the kinematic nature of faults is studied using paragenetic methods and fit as the model of geodynamic development of the West Siberian Basin. Application of this approach made it possible to refine the model of the U1 reservoir of the Urnenskoye field. The faults model of the Jurassic interval of the section based on 3D seismic data is represented by a network of small faults of different orientations. Morphologically, the reservoir of the U1 reservoir is isolated into three hydrodynamically separated blocks, each of which has an independent oil-water contact level. Analysis of the history of the fault formation showed that during the formation of the sedimentary cover, the territory of the Urnenskoye field was in complex tectonic conditions, which was affected the structure of the modern framework of discontinuous faults.