1. Laboratory Determination of Fluid Saturations.

2. Conventional Core Analysis
Two common methods will be discussed
Retort Distillation
Solvent Extraction

3. Retort Distillation Apparatus
Core
sample
Heating
element F
Cooling
water in
Using this technique, the water and oil saturation can be measured directly.
Procedure:
Heat small sample of rock
Water vaporizes first at lower temperature (212º F), The sample temperature remains at 212º F until all pore water is vaporized.
After Water is vaporized, the retort temperature increases to º F vaporizing oil.
Both water and oil are condensed into a graduated cylinder
Record volumes of water and oil vs time
Correct volume of oil for coking and cracking effects
Determine volume of water from pores (not counting water of crystallization from clays)
Determine saturations volumetrically
Cooling
water out
Condenser
Graduated Cylinder

4. Retort Distillation Method
Advantages
Rapid (less than one hour)
Direct measurement of both oil and water volumes recovered
Adequate accuracy

5. Retort Distillation Method
Disadvantages
High temperatures (1, ,100 F):
destroys core sample
water of crystallization in clays may vaporize – and must be accounted for
cracking and coking of oil
cracking is breaking of long chain hydrocarbons into smaller chain hydrocarbons, which may not be recondensed
coke is impure carbon residue formed from oil

6. Determining Water of Crystallization
Water from pores is recovered first
If flattening of curve is not apparent then estimating water recovered from pore space can be innaccurate
Later, water of crystallization is recovered at higher temperatures
This is destroys the core sample

7. Effects of Coking and Cracking of Oil
Coking and cracking tend to cause only part of oil from pores to be recovered
We must scale up the volume of recovered oil to reflect the volume of oil originally in the pores
Scaling factor depends on API gravity of oil
Coke formation destroys core sample
Retort Distillation: Scaling Factor for Recovered Oil

8. Retort Distillation Calculations
Vw = Volume of water, cm3
Vo = Volume of oil, cm3
Vp = Pore volume, cm3
Fcorrection = Volume correction factor,
dimensionless

9. Solvent Extraction Apparatus
Condenser
Using this technique the water content is measured directly and oil content is measured indirectly from the change in weight
Procedure
Weigh fresh core sample
Apply heat - water in pore space of core vaporizes, then condenses in the condenser and falls into the trap where water volume is measured
Boiling point of solvent must be higher than the boiling point of formation water
Heating rate must be high enough to ensure that condensation of water occurs in the condenser, so that water falls into the trap
Solvent leaches hydrocarbons from the pore space and oil remains in dissolved in the solvent
Dry core
Re-weigh core
Graduate tube
Thimble and core
Solvent
Electric Heater
Modified from Amyx, Bass and Whiting, 1960

10. Solvent Extraction Method
Advantages
accurate determination of water saturation
non-destructive to core samples
determination of water saturation by solvent extraction can be made part of the core sample cleaning process for small incremental cost

11. Solvent Extraction Method
Disadvantages
slow (can take several days)
oil volume not directly measured
oil remains in solvent

12. Solvent Extraction Calculations
Wi = Initial core weight, gm
Wdry = Core weight after leaching, gm
Vw = Volume of water collected, cm3
Vo = Volume of oil, cm3
Vp = Pore volume, cm3
w = Density of water, gm/cm3
o = Density of oil, gm/cm3
g = Density of gas is assumed negligible