Abstract
The carbonate reservoirs are a major source of oil and gas throughout the world. The biggest reserves of oil in the world in the middle-east are primarily carbonate reservoirs. Carbonate reservoirs usually have good reservoir quality and are prolific producers.
Carbonates have a highly heterogeneous grain structure as compared to sandstones. The sandstones house all the fluids in the intergranular spaces whereas the carbonated have most of their fluids in the intragranular pore spaces. The path of transport of fluids in the carbonates is through the intergranular pore space. There are different kinds of intragranular porosities in carbonates and all of them interact in a different manner with intergranular porosity. So, we can easily see that it is much easier to characterize and model flow in sandstones as compared to carbonates due to the relatively homogeneous pore structure in sandstones as compared with carbonates.
The general definition of a homogeneous porosity and permeability is applicable to sandstones but not to carbonates. Therefore, the simple lab tests for permeability and porosity will give erroneous results in case of carbonates. At any particular place in a carbonate sample, there are pore spaces of different length scales and different connectivity interacting with each other. These type of heterogeneities can't be captured by simple lab tests run on core samples. Therefore, we have tested computational methods based on transient methodology on a carbonate pore network obtained from a carbonate core Micro-CT scan sample. This method has also been validated on a synthetic sandstone model.
