Comparative Analysis of the Structural Hydrogeological Conditions of the High Temperature Geothermal Reservoirs and Oil Deposit in Volcanic Areas

Abstract

An oil-bearing volcanogenic reservoir exists in West Siberia, hosted in Triassic age rocks (rhyolite tuffs) at a depth between 2.5 and 2.8 km and overlain by low-permeable clay-argillite formations. Reservoir temperatures range from 120 to 130 oC, and pressures from 290 to 310 bars. Integrated analysis of the geological and geophysical data shows circulation patterns, where upflow zones can be identified by positive temperature and pressure anomalies, while downflow zones lead to negative anomalies. These circulation patterns coincide with the former Triassic volcano vents, which are related to volcanic breccias.
Conceptual TOUGH-modeling was used to verify the possibility of oil deposit accumulation in a clay-overlain Triassic rhyolite tuff reservoir fed by oil-bearing upflows from buried volcanic vents. The first approach was 3D numerical model of the reservoir covering 10 x 8 x 3 km3 and represented by a rectangular 10 x 8 x 30 grid. Inverse iTOUGH2-EOS1-modeling was used to estimate heat and mass flows and permeabilities. Next, direct T2VOC modeling used to reproduce oil distribution in the volcanogenic reservoir.