What is reservoir heterogeneity and how does it impact porosity and permeability estimation?

In adition to what mentioned; reservoir heterogeneity can develop in a mature reservoir at a later stage, often through processes used for enhanced oil recovery such as steam injection, chemical injection, or gas injection.

One example of reservoir heterogeneity after a long period of production during mid or late life, the cavitation appearance especially after massive sand production this will severely affect porosity and permeability in unconsolidated sandstone reservoirs

Reservoir heterogeneity refers to unevenness in rock properties within an oil or gas reservoir. These variations impact porosity (space in rocks for fluids) and permeability (ability of fluids to move through rocks). Heterogeneity makes estimating porosity and permeability challenging as they vary across the reservoir, affecting fluid movement and resource extraction.

Em um reservatório heterogêneo, a presença de camadas argilosas pode reduzir a permeabilidade em certas zonas, enquanto arenitos mais porosos podem aumentá-la em outras. Isso exige uma análise detalhada, como apresentado no estudo do meu estágio profissional sobre a estimativa de porosidade e permeabilidade de um campo maduro, onde diferentes fácies foram consideradas para calcular essas propriedades em um reservatório específico.

Core plugs are often cut from more homogeneous parts of the cores and thus may only be affected by smaller-scale heterogeneities such as small-scale laminations. However, permeability estimated from well testing involves a much larger scale, and thus includes larger-scale heterogeneities such as fractures or vugs. A mismatch between these two sources of data may be an indication of large-scale heterogeneity. For example, if well test permeabilities in a reservoir are much larger than typical core permeabilities (e.g. by a factor of 10 or so) it may be an indication of a fractured reservoir.

The uneven nature of these reservoirs makes it difficult to accurately measure and predict their behavior using standard tools and models. Here's how it impacts in-situ bitumen recovery in oil sands: Thief Zones: In recovery methods like Steam Assisted Gravity Drainage (SAGD), steam can preferentially flow into high permeability layers or 'thief zones'. This leads to inefficient heating of the bitumen, making it harder to mobilize and extract. The most drastic impact is caused by multiple barrier layers in the reservoir. These barrier layers can severely impede the development of a steam chamber and the drainage of oil. Flow Control Devices (FCD)s may be viable technology to help mitigate imbalanced reservoir flow in Geothermal operations.