Lab #7

Fluid Saturation

By: Richard Frimpong Owusu

Group Leader: Alfred

Group Members: Alfred, Richard, Graham

Instructor: Liu Junchen

Petroleum Engineering
Missouri University of Science & Technology

Date Performed: October 10, 2023

Date Reported: October 31, 2023

Objective
To determine the oil, water, and gas saturation of core samples.

Introduction
Fluid saturation is defined as the ratio of the volume of fluid phase (oil, water or gas) in a
given core sample to the pore volume (porosity) of the sample. Fluid saturation is an
important factor to the petroleum engineer. Saturation data will help determine whether
or not a well will be economically productive. Water saturation data is commonly used as
one of the parameters that determine where a well should be perforated. Intervals in the
well that has high water saturation (and therefore low hydrocarbon saturation) will not be
perforated because high water production will result.
From a history of the formation of petroleum reservoirs, it is noted that the pores of the
rock were initially filled with water. The oil or gas then moved into the reservoir,
displacing the water to some minimum residual saturation. Thus, when a reservoir is
discovered, there may be oil, water and gas distributed in the reservoir. The direct
approach is the selecting of rock samples and measuring the saturation as they are
recovered from the reservoir rock.
Fluid saturations are usually determined using several different methods. In this
laboratory, U.S. Bureau of Mines procedures was used.

Equipment Listed
• Soxhlet extraction tube • Whatman thimble • Commercial grade toluene
• Liebig condenser • Electric heater • Cold water supply
• Water trap • Fume chamber • Analytical balance
• 500 ml boiling flask • Tongs • Core Samples

Principle of the Bubble Method

A Soxhlet extraction apparatus is the most common method for cleaning sample, and is
routinely used by most laboratories. As shown in Figure 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 120 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. Re-
condensed 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 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 presence of heavy residual
hydrocarbon deposit within the core. Low permeability rock may also require a long
extraction time.

Procedures (Flow Chart)

Figure 1 Soxhlet Extraction method Apparatus

Results and Analysis
Calculation from Water Saturation

Vp =8.5 cm3; Vb =34.5 cm3; Vw = 4 cm3

Sw = Vw/ Vp = 0.47 = 47%
So = 1-Sw = 53%

1. What are the influences of heavy oil on the running time and result?
• Heavy oil has a higher viscosity than lighter oils, which can make it more difficult
for the solvent to penetrate the pores of the sample and displace the oil. This can
lead to longer running times required to achieve complete extraction. Heavy oil
can also clog the thimble, which can restrict the flow of solvent and reduce the
efficiency of the extraction process

2. What are the influences of low permeability or porosity on the running time and result?
• Low permeability: Low permeability makes it difficult for the solvent to
penetrate the pores of the sample, which can increase the running time required to
achieve complete extraction.
• Low porosity: Low porosity means that there is less pore space for the solvent to
fill, which can reduce the running time required to achieve complete
extraction. However, if the sample is tightly packed, it can still be difficult for the
solvent to penetrate all of the pores, even with low porosity.

3. Do you think we can use other solvents to improve the results?

• Yes, the use of different solvents for fluid saturation can improve the results. For
example, solvents with lower viscosities are better able to penetrate pores, while
solvents with higher densities are better able to displace fluids.

4. Watch some videos and review some papers, then briefly introduce the other methods
to determine saturation.

I. Capillary Method
• The capillary method is a simple and accurate method for measuring fluid
saturation that measures the saturation of a porous medium with a fluid.

• It is based on the principle that capillary pressure will cause a fluid to rise in a
narrow tube to a height that is inversely proportional to the pore diameter.
• A porous medium sample is dried and weighed.
• The sample is then placed in a container containing a fluid.
• The sample is evacuated to remove any air from the pores.
• The fluid is then allowed to flow into the sample by capillary pressure.
• Once the sample is saturated, it is removed from the fluid and weighed again.
 • The saturation of the sample is then calculated as the difference in weight
between the dry sample and the saturated sample divided by the volume of the
sample.

II. Chloride Method

• The Chloride Method based on the principle that chloride ions will be adsorbed
onto the surfaces of the pores in a porous medium. The amount of chloride ions
adsorbed can then be measured to determine the saturation of the sample.

• A porous medium sample is dried and weighed.

• The sample is then placed in a container containing a solution of potassium
chloride.
• The sample is evacuated to remove any air from the pores.
• The potassium chloride solution is then allowed to flow into the sample by
capillary pressure.
• Once the sample is saturated, it is removed from the solution and weighed again.

• The saturation of the sample is then calculated as the difference in weight

between the dry sample and the saturated sample divided by the volume of the
sample and multiplied by the concentration of the potassium chloride solution.

III. Retort Method

• The Retort Method is based on the principle that heating a saturated porous
medium will cause the fluid to vaporize and be driven off. The volume of fluid
vaporized can then be measured to determine the saturation of the sample.

• A porous medium sample is weighed and placed in a retort.

• The retort is then heated to a temperature that is high enough to vaporize the fluid
in the sample.
• The vaporized fluid is then collected and condensed.
• The volume of condensed fluid is then measured.
• The saturation of the sample is then calculated as the volume of condensed fluid
divided by the volume of the sample.

IV. Vacuum Distillation Method

• It is based on the principle that heating a saturated porous medium under vacuum
will cause the fluid to vaporize and be driven off. The volume of fluid vaporized
can then be measured to determine the saturation of the sample.
 • A porous medium sample is weighed and placed in a vacuum distillation
apparatus.
• The apparatus is then evacuated to a low pressure.
• The sample is then heated to a temperature that is high enough to vaporize the
fluid in the sample.
• The vaporized fluid is then condensed and collected.
• The volume of condensed fluid is then measured.
• The saturation of the sample is then calculated as the volume of condensed fluid
divided by the volume of the sample.

References
1. Petrophysics Lab #7 Manual, Fluid Saturation, Petroleum Engineering
Department, Missouri S&T
2. SPE/DOE 97571 - Measurement of Fluid Saturation (2005)
3. Standard Test Method for Water and Oil Saturation of Core Samples by Retort
Distillation, ASTM D923-12
4. SPE/DOE 101107 - A New, Simplified Method for Determining Water Saturation
in Core Plugs (2006)
5. Standard Test Method for Measuring the Water Saturation of Core Samples by
Vacuum Distillation, ASTM D4796-88
6. Standard Test Method for Capillary Pressure-Saturation Relationships for Porous
Rock Materials, ASTM D4356-84
7. Core Laboratories Reservoir Description Services - Capillary Pressure and
Relative Permeability Testing (2023)