|Exploring for Oil and Gas Traps|
|Series||Treatise in Petroleum Geology|
|Part||Predicting the occurrence of oil and gas traps|
|Chapter||Predicting reservoir system quality and performance|
|Author||Dan J. Hartmann, Edward A. Beaumont|
Rocks can be classified on the basis of their pore geometry into four major pore categories that can be divided into ten subcategories. Extensive experience and laboratory analysis show that these pore type categories have a particular behavior when interacting with fluids that can be used to predict the behavior of reservoir systems over time.
Pore geometry is categorized as intergranular, intercrystalline, vuggy/moldic, or fracture. Pore throat sizes are categorized into mega-, macro-, meso-, and micro-pore types. Combining both pore geometry and pore type into a classification scheme is an effective method of describing pore systems. For example, a very fine-grained sandstone might be classified as having intergranular mesoporosity or a limestone as having vuggy macroporosity.
Table 1 describes a typical rock type for each pore type in the classification.
|Pore geometry/pore type||Archie||Non-Archie|
|Mega/macro||Clean, coarse sandstone or carbonate grainstone||
||Chlorite- or illite-cemented (pore-lining) coarse sandstone||Connected vugs or vugs in a crystalline matrix||Fracture width >50µ|
|Meso||Clean, coarse silt to very fine sandstone or carbonate grainstone||
||Poorly connected vugs or oomolds in a fine to medium crystalline matrix||Fracture width 5-50µ|
|Micro||Clean clay-size to fine siltstone or clay-size carbonate||
||Sandstone with clay in pore throats||Dispersed vugs in microcrystalline matrix||Fracture width <5µ|
- Pore system fundamentals
- Pore system shapes
- Pore and pore throat sizes
- Pore throat size and connectivity
- Capillary pressure (Pc) curves: pore throat size determination