Pore systems

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
Link	Web page
Store	AAPG Store

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-port types. Combining both pore geometry and port 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.

Table 1 Typical rock types by pore class

Pore geometry/port type	Archie			Non-Archie
	Intergranular/interparticle	Intercrystalline	Clay cemented	Vuggy	Fracture
Mega/macro	Clean, coarse sandstone or carbonate grainstone	Coarsely crystalline carbonate Quartz- or carbonate-cemented coarse sandstone	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	Very fine to medium crystalline carbonate Quartz- or carbonate-cemented fine to medium sandstone	Chlorite or illite cemented (pore lining) fine to medium sandstone Kaolinite cemented (pore filling) coarse sandstone	Poorly connected vugs or vugs/oomolds in a fine to medium crystalline matrix	Fracture width 5-50µ
Micro	Clean clay-size to fine siltstone or clay-size carbonate	Silt-size crystalline carbonate Quartz- or carbonate-cemented silt to very fine sandstone	Sandstone with clay in pore throats	Disbursed vugs in microcrystalline matrix	Fracture width <5µ

See also

• Pore system fundamentals
• Pore system shapes
• Pore and pore throat sizes
• Connectivity and pore throat size
• Classifying pore systems
• Determining pore throat size from Pc curves

External links

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