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Publisher Summary This chapter discusses the important aspects of flow of fluids through carbonate formations. The main rock-fluid properties entering into the fundamental flow equations that describe the flow of fluids through porous media are briefly discussed, with emphasis on carbonate reservoirs. The main rock–fluid properties are: (1) wettability, (2) capillary pressure, and (3) relative permeability. The main difference between the flow of fluids through carbonate rocks and sandstones is due to the extremely heterogeneous nature of carbonate formations. Diagenetic changes can strongly modify the original formation characteristics of carbonate rocks and, in some cases, can completely change the original properties—such as texture, porosity types, and their distributions—of the rocks. The carbonate pore space systems are usually more complex than sandstone-type systems. Even the primary or original porosity in carbonates is more variable owing to the diversity of size and shape of the particles, in addition to the fact that many types of particles may have internal porosity. The latter is characteristic of the fragments of original organisms and is referred to as intragranular porosity. Another prominent effect in the flow of fluids through carbonate formations is that of high-velocity flow, that is, the flow region where Darcy's law, which implicitly considers the proportionality between pressure (potential) drop and velocity through the porous media, does not hold. |
