RE:RE:One well took 3 monthsGood question! The Rate of Pentration (ROP) does indicate the geology that is being drilled through, but it is more indicative of formation hardness, not necesarily hydrocarbon content. Generally there is no hydrocarbons in very hard formations like chert, but instantaneous ROP is indicative of these formation changes, and the only way we would know instantaneous ROP is to see the electronic drilling recorder (EDR) on the rig or through Pason.
The other thing to keep in mind is that these are strat wells, and ROP and drilling efficiency is not the priority, drilling a clean hole to get good logging data is. Also, when coring, the ROP is generally much slower than conventional drilling. The logging data will have a greater depth of investigation into the formation (depending on the specific toools run), and will give a graeter amount of "general" data than the cores. However, the cores are useful to "calibrate" and confirm the logging data.
The cores will provide excellent information based on the intervals that were cored. The side walls cores (at least the ones I have run on strat wells) are capable of taking a formatoin sample with the formation fluid at relatively virgin reservoir conditions intact. The conventional cores will be analysed for hydrocarbon content (what is left in the cores as conventional cores are not the greatest at mainting fluids in very permiable core samples), permiability and porosity however will be the 2 big ones (they can run a pressure differential test across the core to determine permiability). The cores will also give a very good indication of the stratigraphy of the borehole, and a very good indication of geology - eg. shale caps or sand zones, and potentially drilling problem areas like interbedded chert. Cores are probably one of the best ways to gain info on the formations, and really lend credence to log information.