Rock Mechanics Manicure (Part II)

The black shale contained crude oil and I thrilled the first time I smelled it! By the middle of the third day, though, I saw the room moving. Then I looked down – my stool had wheels.

While Tech only needed one meaty hand on the spindle to core, I needed both hands and some body weight to get the bit through my rocks. Coring bits use water (or sometimes hydraulic oil) to keep cool as they grind their way through the rock. With this drill press, the water is collected in a large metal pan that needs to be emptied periodically. I was not strong enough to hang on to the rock while emptying the water pan, so every second or third drilled core I removed the rock, emptied the pan, and reset my rock for the next core sample.


For a few of my rock specimens harvested from outcrop, I oriented the rock itself to North. Depending on the stress fields in the rock, this may impact the way it fractures (DYNAMICALLY!) when subjected to tensile stress. Knowing which direction the rock will fracture determines which direction petroleum engineers place the wellbore for greatest oil and gas production. The black lines and red lines above allow me to know which direction the core sat in the rock even after I’ve drilled it. No matter how the core comes out, I know red is on the right and black on the left.

The picture above and the main picture are the same rock, pre- and post-coring. It isn’t evident from the photos, but the rock specimen does not have uniform thickness. My samples need to be as close to 1″ diameter by 2″ in length as possible, so I drilled my cores through the thickest part of the rock specimen.

Each sample went into a labeled Ziploc freezer bag. The labels read Formation, Sample Number, Group, and Orientation (perpendicular, parallel or at an angle to bedding plane). By the time I transport my precious samples home for fracturing (DYNAMICALLY!) I will have no idea which sample corresponds with what formation. A fine point Sharpee and a Ziploc saves me from future heartache.

It takes 30 samples for a statistically significant set, but more is better. I set my Base Goal for 100 and my Reach Goal for 150. At the end of each day, I took my precious cores back to the apartment and catalogued their details: Day 1, 50 cores. By Day 2 I had 92 cores for testing. At the end of Day 3 I made it to 140.

My hands swelled and ached from the holding rocks against the vibration of the drill press. My shoulders hurt from lifting rocks and water pans full of silty water. My eyes burned and head hurt from the off-gassing rocks. I did not quite make my reach goal, but at the end of Day 3 I had enough for my research. Ok, I was a little disappointed (a lot disappointed) I did not make my Reach Goal, but it’s fine. Time to close up shop.

The next morning I came in to start on the next project only to find Tech got me over the hurdle for my Reach Goal. He cored the last bit of rock so I could make my 150. That, friends, is kindness.


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