[Notes] Petroleum Geology Part 2

 Porosity = (bulk volume - grain volume)/bulk volume x 100

Range of Porosity in %

1. 0-5 - negligible
2. 5-10 - poor
3. 10-15 - fair
4. 15-20 - good
5. 20+ - very good

Nature of Porosity

1. Primary

- rock possesses this at the end of its depositional phase

- void of unaltered, fractured or dissolved grains

- depends on:

        * degree of uniformity

        * shapes of grains

        * packing

        * effects of compaction, during and after deposition

2. Secondary

- additional void space due to post-depositional or diagenetic processes

Rock samples

1. Sandstones - compaction, contact-solution and redeposition and to cementation

2. Carbonates - modification by solution, recrystallization, fracturing and cementation