Experimental and Numerical Investigation of Steam Flooding in Heterogeneous Porous Media Containing Heavy Oil

Abstract

Thermal recovery methods and especially steam flooding have long been considered as the most effective methods to unlock heavy oil reservoirs. These highly viscous hydrocarbon deposits are proven to constitute a huge proportion of total world oil reserves. Large volumes of heavy oil are located in heterogeneous porous media containing high permeable wormholes or non-permeable shale barriers. High permeable zones can be the results of sand migration in loose and unconsolidated sandstones. There is a question of how these non-homogeneities can possibly enhance or hinder the flow of high viscous oil, steam and condensed water under a steam injection process. This paper addresses experimental and simulation study of steam flooding in heterogeneous porous media that contains Athabasca heavy oil. Some PVT properties of Athabasca crude oil have been measured experimentally and simulation study was accomplished using a numerical thermal reservoir simulator. A horizontal layer of high porosity and permeability was assumed in the middle of a core to verify the performance of steam injection in a 20 cm long sandstone core with a permeability of 640 mD saturated with Athabasca heavy crude. High permeable zone had a permeability of 5 D. Different shale barrier configurations were also considered to examine the effect of these no flow layers. Considering a heterogeneous system, sensitivity analyses were focused on the effect of injection rate, porosity, permeability contrast and thickness of high permeable zone. Different steam temperature and quality cases for core flooding experiment in this system were also investigated. The most important conclusion is that there is an optimum steam temperature and quality for most efficient steam injection. It was figured out that shale barriers in the model can hinder the flow of oil and cause high residual oil, but their impact is dependent on permeability distribution in the core. The permeability contrast between the high and low permeable layers should be smaller considering both oil production and steam oil ratio (SOR), which is a measure of economy. Although core permeability of 640 mD provides satisfactory recovery and SOR, higher permeability can cause faster recovery and lower SOR, since the injection can stop earlier. Porosity of the model is found to have an inverse relation with the oil recovery and SOR. Results also clearly show that higher injection rates improve the oil recovery. However, SOR should also be considered at the same time. There is a trade-off between recovery and SOR. It is also clear that lower thickness for the high permeable zone results in better recovery while causing high injection pressure at the inlet. This corresponds with lower permeability contrast case.