8.2 Measurement Methods 8.2.1 Direct Injection of Solvent
The solvent is injected into the sample in a continuous process. The sample is held in a rubber
sleeve thus forcing the flow to be uniaxial.
8.2.2 Centrifuge Flushing
A centrifuge which has been fitted with a special head sprays warm solvent onto the sample.
The centrifugal force then moves the solvent through the sample. The used solvent can be
collected and recycled.
8.2.3 Gas Driven Solvent Extraction
The sample is placed in a pressurized atmosphere of solvent containing dissolved gas. The
solvent fills the pores of sample. When the pressure is decreased, the gas comes out of
solution, expands, and drives fluids out of the rock pore space. This process can be repeated
as many times as necessary.
8.2.4 Soxhlet Extraction
A Soxhlet extraction apparatus is the most common method for cleaning sample, and is
routinely used by most laboratories. As shown in Figure 8.1, toluene is brought to a slow boil
in a Pyrex flask; its vapors move upwards and the core becomes engulfed in the toluene
vapors (at approximately 110°C). Eventual water within the core sample in the thimble will
be vaporized. The toluene and water vapors enter the inner chamber of the condenser, the
cold water circulating about the inner chamber condenses both vapors to immiscible liquids.
Recondensed toluene together with liquid water falls from the base of the condenser onto the
core sample in the thimble; the toluene soaks the core sample and dissolves any oil with
which it come into contact. When the liquid level within the Soxhlet tube reaches the top of
the siphon tube arrangement, the liquids within the Soxhlet tube are automatically emptied bya siphon effect and flow into the boiling flask .the toluene is then ready to start another cycle. A complete extraction may take several days to several weeks in the case of low:API gravity crude or presence of heavy residual hydrocarbon deposit within the core low permeability rock may also require a long extraction time
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