Upward Bound 2016
Lab 2:
Geoscience and Petroleum Engineering
Porosity
Introduction:
Good morning class and welcome to our second lab experience! Today we will be
splitting up into teams of three, to work on two experiments. Please begin this lab by
reading through the below information, then get started with your group. If you have any
questions or need help at any time, please ask your lab instructor.
In Petroleum Engineering, the main goal is the removal of oil and gas from the
earth. These deposits of oil and gas sit in reservoirs thousands of feet underneath the
surface. These reservoirs are not big underground pools of oil and gas, but areas where
rock is filled with fluid. The rocks act like sponges and contain small holes and crevices
called pores. Across the entire rock these small pores add up to create a pore volume,
where the oil and gas resides. The area that is solid rock contains no extra area to hold
fluid. Beach sand is a great representation of this. A single grain of sand has no room for
fluid, but in a container of sand there is room for liquids between the grains. This room is
the pore volume, in between the grain volume. An illustration of this can be seen below:
Vg, Grain Volume
Vp, Pore Volume
Figure 1: Pore Volume in Rock
These terms and values are instrumental in petroleum engineering. The best
reservoirs will have a lot of pore volume and a small amount of grain volume. A ratio of
pore volume to grain volume therefore would be greatly helpful in the industry. There is a
term to describe this ratio and it is called porosity. Porosity is the fraction of pore volume
over the total volume. This total or bulk volume can only be made up of two things, the
pore volume and the grain volume. Therefore the equation for porosity is:
Porosity (Φ) = Pore Volume (Vp)/ Bulk Volume (Vb) [Eqn. 1]
Or
Porosity (Φ) = Pore Volume (Vb) / (Pore Volume (Vp) + Grain Volume (Vg)) [Eqn.2]
Description:
This lab is designed to introduce students to the concept of porosity. The lab will teach
students two different ways to calculate porosity, as well as how it is used in the oil and
gas industry.
Time to Complete:
Students should be able to complete all aspects of this lab in 1 hour and 45 minutes.
Tools Needed:
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Upward Bound 2016
-15-20 marbles per group
-Large 200ml beaker
-Small 10ml beaker
-Digital scale
-10 lb. Sand or similar material to test
Geoscience and Petroleum Engineering
-Rulers, or calipers if accessible
-Calculator for each group
-200 ml of water, preferably distilled
-Sealable tube (Pringles Can) for each
group
Safety:
Safety is the first priority in any lab. This lab includes small items and glassware. All
students must be responsible and careful while handling glass. Students must wear closed
shoes and eye protection while glassware is present. Any accidents or spills should be
immediately reported to the instructor for clean up.
Experiment 1: Finding the Porosity of Marbles
Marbles are a representation of spherical grains in rocks. Many rocks in the earth’s
subsurface are made of similar grains and can be represented by marbles.
Step 1: Gather your materials:
Grab the water, beakers, marbles, ruler and calculator.
Step 2: Analyze the marbles and as a group predict a value for the porosity of
marbles.
Hypothesis: Φ =____________________%
Step 3: Choose 15 marbles of similar size and measure their diameter (width).
Create a table of marble number tested and diameter in cm, titled “Table 1”, located
in the appendix. Also include in the table the average of these diameter values as
davg.
Step 4: Add the 15 marbles to the large beaker, pushing them down to create a flat
horizontal line representing the top of the marbles.
Step 5: Pour water into the small beaker, filling up to the 10ml line. Add this water
into the large beaker. Repeat this step until the water line matches the horizontal
plane created in Step 4. Count the total volume of water added, using 10ml for each
pour, minus the remaining volume in the small beaker. This volume is your pore
volume.
Pore Volume (Vp): ________________mL
Step 6: Calculate the grain volume, by finding the volume of the marbles. This can be
done using the equation for the volume of a sphere:
V= 1/6 π d3
Use your average diameter and multiply by the number of marbles in the container.
This is your grain volume.
Grain Volume (Vg): ________________mL
Step 7: Compute the found porosity using Eqn. 2. Keep in mind that 1ml= 1cm3.
Report this value and compare to your hypothesized value:
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Geoscience and Petroleum Engineering
Results: Φ =____________________%
Comments:
Experiment 2: Finding the Porosity of Sand
Sand is a more realistic representation of a reservoir rock. Many famous oil
reservoirs are in sandstones, which are rocks made of deposited sand grains that
fused together over time to form a single rock.
Step 1: Gather your Materials:
Grab the sand, sealable container, water and scale.
Step 2: Analyze the sand and as a group predict a value for the porosity of sand.
Hypothesis: Φ =____________________%
Step 3: Measure the bulk volume of the container:
Do this by finding the diameter (width) of the inside of the tube, and finding the
length:
Diameter (d): ____________________cm
Length (L): ____________________cm
Solve for bulk volume using the equation for a cylinder:
V= π/4 d2 L
Bulk Volume (Vb): ____________cm3
Step 4: Add sand to the container, packing as much sand into the container as possible,
making sure the lid can still go on with no spilling out.
Step 5: Weigh the container in grams
M1: ______________g
Step 6: Add water to the container:
Remove the lid and slowly pour water into the container until it slightly begins to
overflow. Be careful to make sure only water is leaving the container and all sand stays
inside.
Step 7: Weigh the container again, and find the weight of water added.
M2: ______________g
MWater: _______________g
Step 8: Find the pore volume. Take the mass of water added to the beaker, and find it’s
volume using the density of water, 1gram/cm3.
Pore Volume (Vp): ________________mL
Step 9: Compute the found porosity using Eqn. 1. Report this value and compare to
your hypothesized value:
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Upward Bound 2016
Geoscience and Petroleum Engineering
Results: Φ =____________________%
Comments:
Compare your results from Experiment 1 and Experiment 2, and comment below:
Appendix:
Table 1. Marble Diameters
Marble # Measured d (cm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
davg
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