FLUID CONVECTION IN SEDIMENT-HOSTED RESERVOIRS DUE TO THERMAL ACTION OF DIKES AND SILLS

Abstract

Flow regimes of pore fluid were studied, with the steam-water phase transition near cooling intrusions of dikes and sills in a sedimentary basin taken into account. The study was based on a computer program simulating a one- or two-phase flow of the steam-water mixture depending on the phase state of the fluid. An actual section of the Yenisei-Khatanga basin northwest of the Siberian Platform is analyzed. Two types of models were used: (1) intrusion of a sill into the basement of the basin, beneath a reservoir bed, and between two reservoirs; (2) the same situations but with a vertical dike and an off-branching sill. Simulations were carried out to study the effect exerted on convection by pore fluid of a single sill or a dike combined with sill that intrude into the sediment. The results of the calculations permit prediction of the beginning of convection depending on the type of intrusion, its location in the section of sedimentary basin, initial temperature, and physical parameters of rocks. Patterns of evolution of temperature field and velocities of fluid flows in the sediment around cooling intrusions have been obtained. The problem is important for predicting the behavior of both water and hydrocarbon fluids in basins where trap magmatism is expressed.