"seismology" lol, I knew there was a word for "acoustics from explosions" 15k is deep. We used to drill ~12k. The deepest hole any rig I was on drilled to 18k and at the time that was on of the deepest ever drilled in the US as I recall. Tech has changed a lot. You were probably fracking which is after my time in the oil patch. Hell directional drilling was a nightmare when I was in. Now I understand it's pretty straight forward. What kind of scratch were you making? I'd guess tax free if you stayed out of the country long enough.