Porosity logging

Department of petroleum engineering

Soran university

Present by : Reband azad raza

الرحيم الرحمن الله بسم

• Porosity Logs Sonic log Density Log

None of this Logs can directly measures porosityCombination of these tools ,will give good indication

for porosity

• A log that measures interval transit time (Δt) of a compressional sound wave travelling through the formation

Sonic log

• Dense rock – faster travel time• Porous rock – slower travel time

How would you find a porosity from sonic curve diagram ?!

There is two method to measure porosity from sonic Log :

1- Equation 2-Sonic porosity chart

1-

2-

1-Porosity – By equation method –sonic toolFirst step indicate a wanted depth porosity

11500 m

11700 m

Apply this equation :

From Curve

c

Fresh water mud in well =189

salt water mud= 185

Equation method

dolomite

4c

salt water mud= 185

79 ∆ 𝑡𝑙𝑜𝑔=¿

So,

Dolomite from chart

Chart – sonic log - porosity

Density log

The density logging tool is made up of: - a radioactive source of either Cs-137 or Co-60

The gamma rays enter the surrounding rocks where some are absorbed.

It has 2 detectors

• Long range

• Short range

There is two method to measure porosity from density Log:1- Equation 2-density porosity chart

Apply this equation :

Equation method

Pe 

Material 

2.648 

Sand 

3.76 

Shale 

2.71 

Limestone 

2.876 

Dolomite 

2.032 

Salt 

2.977 

Anhydrite 

From curve

Fresh water mud in well =1.0

salt water mud= 1

dolomite2

2

salt water mud= 1

So,

Chart – density log - porosity

Any Question ? !