Effect of oil composition on fluid substitution in heavy oil reservoirs

Abstract

Unlike light oils, heavy oils do not have a well‐established scheme for modelling elastic moduli from dynamic reservoir properties. One of the main challenges in the fluid substitution of heavy oils is their viscoelastic nature, which is controlled by temperature, pressure, and fluid composition. Here, we develop a framework for fluid substitution modelling that is reliable yet practical for a wide range of cold and thermal recovery scenarios in producing heavy oils and that takes into account the reservoir fluid composition, grounded on the effective‐medium theories for estimating elastic moduli of an oil–rock system. We investigate the effect of fluid composition variations on oil–rock elastic moduli with temperature changes. The fluid compositional behaviour is determined by flash calculations. Elastic moduli are then determined using the double‐porosity coherent potential approximation method and the calculated viscosity based on the fluid composition. An increase in temperature imposes two opposing mechanisms on the viscosity behaviour of a heavy‐oil sample: gas liberation, which tends to increase the viscosity, and melting, which decreases the viscosity. We demonstrate that melting dominates gas liberation, and as a result, the viscosity and, consequently, the shear modulus of the heavy oils always decrease with increasing temperature. Furthermore, it turns out that one can disregard the effects of gas in the solution when modelling the elastic moduli of heavy oils. Here, we compare oil–rock elastic moduli when the rock is saturated with fluids that have different viscosity levels. The objective is to characterize a unique relation between the temperature, the frequency, and the elastic moduli of an oil–rock system. We have proposed an approach that takes advantage of this relation to find the temperature and, consequently, the viscosity in different regions of the reservoir.

Mechanisms of Fluid Migration and CO2 Storage in Low Permeability Heavy Oil Reservoirs Using High-Pressure Microfluidic CO2 Flooding Experiment

“…Heavy oil is characterized by its high viscosity and a significant presence of colloids and asphaltenes, which make it less mobile and more challenging to exploit when compared to light crude oil. , Currently, global proven heavy oil resources have surpassed 700 billion barrels, with countries like Canada, Venezuela, Russia, and the United States holding significant reserves. − Given the substantial proportion of heavy oil in the overall oil reserves, heavy oil reservoirs are gaining prominence as crucial future energy sources to meet the growing global energy demand. , …”