Sequence stratigraphy western desert

Symbols Used in Log InteSymbols Used in Log Interpretationrpretation

Resistivities:

Rt    - Resistivity of the formation  in the virgin zone, ohm-m

Rxo  - Resistivity of the flushed zone, ohm-m

Rs   - Resistivity of the shoulder (adjacent) beds, ohm-m

Rm  - Resistivity of the mud, ohm-m                                  Rmc - Resistivity of the mud cake, ohm-m

Rw   - Resistivity of 100%  formation water, ohm-m

Rmf  - Resistivity of 100%  mud filtrate      , ohm-m

Saturations:

Sxo  -Mud filtrate saturation in the flushed zone, %

Sw   - Water saturation in the virgin zone, fraction of pore volume in, %

Diameters:

dh   - Diameter of the hole, m                                                                di    - Diameter of the flushed zone, m

DRi    - Diameter of the flushed and transition zones together, m

Thicknesses:

h    -Height of the bed being logged , m                           hmc  - Thickness of the mud cake, m

BASIC OPEN HOLE LOGGING AND FORMATION EVALUATION

SourceRock

organic‐rich sediments                   

  Deposited under airless conditions 

Types of source rocks:

are classified from the types of kerogen that they contain

• source rocks are formed from algal remains deposited under anoxic conditions in deep lakes: they tend to generate waxy crude oils when submitted to thermal stress during deep burial

• Source rocks are formed from marine planktonic remains preserved under anoxic conditions in marine environments: they produce both oil and gas when thermally cracked

during deep burial.

• Source rocks are formed from terrestrial plant material that has been decomposed by bacteria and fungi under oxic or sub‐oxic conditions: they tend to generate mostly gas with associated light oils when thermally cracked during deep burial. Most coals and coaly shales are generally Type 3 source rocks.

Example: Shale - Limestone