Experimental Procedure

Be sure to record exactly what you do, what readings you take, what valves you open or close at various stages in this experiment. THINK ABOUT WHAT PARTS OF THE SYSTEM ARE CONNECTED AT ALL TIMES.

****DANGER!!!! NEVER OPEN THE SYSTEM WITHOUT FIRST LETTING OUT THE GAS SO THE PRESSURE DROPS TO ZERO.****

1. Measure the length and the diameter of your sample. Repeat the 5 times.

   	1	2	3	4	5	Average
   Diameter ()
   $\pm$
   Length ()
   $\pm$

2. Determine the volume of the sample cell, $V_{cell}$, and expansion cell, $V_{exp}$, of the porosimeter
   1. Ensure V1 is closed tight. Open V2 and V3. Wait until the reading on the multimeter is stable. Record the voltage corresponding to the atmospheric pressure.

   2. Ensure V2 and V3 are closed tight. Open V1 to let gas flow into sample cell only. When reading on multimeter stabilize, close V1. Record reading.

   3. Ensure V1 and V2 are closed tight. Open V3 to let the gas flow to the expansion cell. Record reading.

   4. Open V2 to release the gas from the system. Make sure V3 is open. Close V3.

   5. Measure the diameter of the calibration sphere using the caliper. Take 5 measurements.

      	1	2	3	4	5	Average
      Diameter ()
      $\pm$

   6. Ensure that V1 is shut tight and that no gas is left in the system. Open the sample cell by unscrewing the lid and place the calibration sphere inside. Close the lid properly.

   7. Repeat the steps (b) through (d).

3. Calculate the volume of the sample cell, $V_{cell}$, and of the expansion cell, $V_{exp}$. Make sure you have a clean account of your calculations. Don't forget to correct for the atmospheric pressure. If you set the problem right, you should end up with 2 equations and 2 unknowns that are $V_{cell}$ and $V_{exp}$. Make sure that your solution is an expression of a volume by looking at the unit and verify that the order of magnitude is consistent with the size of the components of the porosimeter (e.g. a volume of $1\,\mathrm{km}^3$ would be excessive).

4. Determine the porosity of your rock sample
   1. Ensure that V1 is shut tight and that no gas is left in the system. Open the sample cell by unscrewing the lid and place your sample inside. Close the lid properly.

   2. Ensure V2 and V3 are closed tight. Open V1 to let gas flow into sample cell only. When reading on multimeter stabilize, close V1. Record reading.

   3. Ensure V1 and V2 are closed tight. Open V3 to let the gas flow to the expansion cell. Record reading.

   4. Open V2 to release the gas from the system. Make sure V3 is open. Close V3.

5. Calculate the effective volume of your sample (i.e. the volume that is not filled with helium) using $V_{cell}$ and $V_{exp}$. Now use this value to find the its porosity. Before you do your calculations, think about which volume you are measuring. Are all the pores filled with helium? What is the difference between water and helium? Is the maximum saturation different when using helium instead of water? Please comment on that in your discussion.