RE: coil rigsBigbil, I never worked on a coil rig but I would imagine they can go pretty quick on shallow holes. That is the reason why they use them.
The first person to know if theyit gas is the motorman on the rig(if he is smart enough to know what the signs are) The motorman collects the samples and takes over to the geologist. You can see and smell the oil when working on the rig, especially if you are the one cathing the samples. You will sample all the way down the hole after surface drilled. If you are getting close to the pay zone the geoligist make ask you take saples every 5 minute or so. I have been on a rig doing a tight hole(high security) and had to take samples every 2.5 minutes. It was nice cause I didn't ahve to do any of the other work on the rig, just sit at the shaker(where the drill mud gets separated from the rock, or shale, or sand) and took samples for eight straiight hours.