Caught In A Misfire
One out of 24 ain't bad. Look closely at the core barrel laid up next to the misfire and you can see it bleeding green oil. Once pressed out of the barrels into little bottles, these side wall cores can be looked at, smelled, tasted and viewed under a black light for fluorescence before sending them off to the lab for analysis. Old hands can often tell whether they have made a well or not before the analysis is ever received.