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Clean core samples using soxhelt.pdf
1. Summary
Certain additives used in drilling and completion fluids may alter the wettability of core. For example,
the surfactants in invert-oil-emulsion drilling muds are known to alter the wettability of core. Because
routine cleaning methods do not remove these surfactants, core that is to be used for special laboratory
analyses, such as relative permeability, capillary pressure, and saturation exponent, is left with an
altered wettability. Experiments with such core will obviously produce erroneous data. To obtain
reliable results, cleaning methods must be developed to remove these surfactants, allowing restoration
of plugs to their natural wettability. Once the core is cleaned, the wettability of the cleaned core can be
restored by saturating with synthetic formation brine and uncontaminated reservoir crude, then aging
at the reservoir temperature.
AL-FARABI UNIVERSITY COLLEGE
Clean core samples using soxhelt
Petroleum Engineering Department
Reservoir Lab
Third stage-class A Group B
Laith Ali Ahmed
11/4/2022
3. page 2
Introduction
A prerequisite to the evaluation and management of oil properties is accurate information derived from
the analysis of core samples; but reliable data, such as porosity and permeability, can result only if all oil
and water have been removed from the core samples analyzed. The most common method of core
cleaning used to date has been Soxhlet extraction-a somewhat static technique, which depends upon
the slow diffusion of hot solvent through the core sample. Soxhlet extraction performs satisfactorily
only with highly permeable samples and at best requires long cleaning periods. The centrifuge method
was developed in 1951 by Continental Oil Co. to overcome the inefficiencies inherent in the Soxhlet
method. The new method is basically an operation in which hot solvents are caused to flow through the
samples under the influence of centrifugal force. The centrifuge unit has proved so successful that
samples which formerly required days for partial extraction can now be completely cleaned in
approximately one hour. The original idea was conceived in 1950 by Elmer S. Messer, whose early
experiments consisted of flowing solvent over sandstone samples suspended in a revolving basket and
driven by a vertically mounted vacuum cleaner motor. Results were so outstanding that more
permanent units were constructed. A modified model using this basic design was recently built by Core
Laboratories, Inc., and is now used regularly in their operations.
Aim
The main objective of this experiment is to clean the basic components obtained from hydrocarbons and
to calculate the porosity of the core.
Theory
A Soxhlet extractor is the most common method for cleaning a sample, and is routinely used by most
laboratories. Toluene is brought to a slow boiling point in a Pyrex flask, its vapors move up and the pulp
is swallowed up in toluene vapors (at about 110°C). Eventually, the water in the core sample will be
evaporated into the thimble. Toluene and water vapors enter the inner chamber of the condenser, and
cold water circulating around the inner chamber condenses both vapors into non-toxic liquids. The inner
chamber condenses both vapors into immiscible liquids. Recompensed toluene with liquid water falls
from the base of the condenser to the core sample in the thimble; Toluene absorbs the base sample
and dissolves any oil it comes in contact with. When the fluid level inside the Soxhlet tube reaches the
top of the siphon tube arrangement, the fluid inside the Soxhlet tube is automatically emptied. by a
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
4. page 3
presence of heavy residual hydrocarbon deposit within the core. Low permeability rock may also require
a long extraction time.
Fig 1-1 soxhelt extractor
toluene
5. page 4
Procedure
1. We put an amount of toluene ranging between 250-280 ml in the flask.
2. We put the core sample in the core chamber
*note : (Put it at a 90 degree angle so it doesn't break the core chamber).
3. We collect the parts of the device and put them on the heater.
*note : flask on heating , core chamber on flask and condenser top of core
chamber
4. We turn on the electricity on the device and make sure that it arrives.
5. We turn on the cooling system.
6. Start heating.
*note : We must watch the toluene so that we do not have problems during
the process of adjusting the temperature.
7. We adjust the heater control knob between 6-7.
8. The distillation process will begin when the toluene reaches a temperature
of 113 degrees Celsius.
9. When toluene turns transparent, we will know that the core sample have
been completely cleaned.
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Discussion
We must be aware of some things that may happen
and the most important
1- human safety.
2 -To set the temperature well.
3 -We make sure that there is no water in the samples to be cleaned, and when there is water,
we put some glass beads in the vial to prevent explosions.
4- We must pay attention to the cooling system as working properly.
5- And it must be ensured that there is a substance that prevents the evaporation of toluene
when we put the cooling system above the core chamber.
Thank you
