I have sat many drilling rigs and evaluated many wells with wire line cores and drill stem tests in my day. Hardly anyone I know anymore even knows how wire line cores are taken before the well is TD'd; they never even heard of 'em. A good wire line core hand smells, and tastes his cores looking for hydrocarbons. DST's are a blast; there is absolutely nothing more fun in the exploration business than when oil and gas flows thru drill pipe to the surface. It'll give a fella goose bumps every time.
"Kids" now days sitting 2000 HP diesel electric rigs drilling horizontal laterals park their hinies in air conditioned trailers and monitor rate of penetration, weight on bit, torque and a host of other parameters via transducers in the bottom hole assembly above the drill bit. They seldom leave the comfort of their desks to go up on the rig floor, or around to the shakers. These company trailers often have entire banks of computer screens to watch every aspect of the rig operation, even damn cameras that watch hands making connections, doctoring drilling mud and eating baloney sandwiches in the doghouse.
Geolographs are an old school way of measuring rate of penetration and looking for drill breaks indicative of potential pay zones. Not too many folks these days even know what a geolograph is, or what its used for. Here is a brief explanation via Petrowiki:
"The geolograph, or drilling recorder, mechanically monitors depth and records drilling parameters in time. These parameters are recorded on a paper chart, graduated in minutes, that is wrapped around a drum. The drum rotates one revolution in 8, 12, or 24 hr. To record depth, a small cable is run from the geolograph to the top of the kelly via a pulley on the crown of the derrick (see Land rigs). Kelly height can then be measured and directly related to bit depth. As each foot is drilled, an ink pen on the geolograph places a small mark on the chart. Every 5 ft the pen places a larger mark on the chart (Figure 1).
Geolographs are very useful (lots of rigs I use still have them) when drilling in wide open spaces, looking for new stuff, or when stepping way out from old stuff, and when drill breaks occur they'll tell you to stop and circulate bottoms up to see what 'ya got. Its old school, and it works really well. Geolographs are handy, sometimes, if you are looking for core points in the well and trying to figure out when to pull out of the hole and pick up a core barrel.
Full hole coring a potential pay zone is also a whole lot of fun, by the way, almost as fun as drill stem tests. Breaking out the core bit with the barrel still hanging in the block and having crude oil run out all over the floor is very cool.
When I am drilling infill development wells, say less than a thousand feet apart, and targeting new zones in stacked plays, or I am trying not to penetrate a known oil water contact in the bottom of a clastic sand, I often need to be more precise than measuring rate of penetration every five feet with a geolograph. That's when I drag out the 'ol stop watch and do some old fashion, really old school... time drilling. I mark the kelly in two foot intervals and measure time to drill those intervals with a stop watch, then plot them on a linear scale, rate of penetration chart. I can then correlate my time log to an open hole log presented on the same linear scales, etc. The whole process sort of looks like this, below:
Time drilling in this manner I pretty much know where I am at all times. I've gotten pretty good at it over the years and occasionally don't even open hole log an infill well when I feel comfortable with my formation tops and don't see any missing sections that might suggest faults or thinning of the stratigraphic interval. I can determine sub-sea datums using the time log and know where I am structurally in the field or on regional strike to wells I am keying off.
After I set casing I then run an array of cased hole logs, like gamma ray/neutron logs and almost always my ROP plot will lay over nicely to the gamma ray curve. If I am more than a few feet off, which is rare, I get pretty mule-lipped and vow a much higher degree of accuracy on the next well I drill. All this works great until Mother Nature slips a fault splinter into the section, then its hell figuring out where you are.
Almost always this time drilling shit happens at 03:00 in the morning in the cold, and rain, with your fingers freezing and mud splattering everywhere, or coffee blotches on the log.
In this particular well my time log is on the left and I did, in fact, run an open hole induction log behind it, on the right. By my time log I believed I was actually 4-5 feet structurally high on my primary pay zone at 2,257 TMD to an offset well. After open hole logging I was pretty much flat to the offset. By my time log I was able to circulate bottoms up looking for mud shows from various pays and I always make notes on my log about WOB, if the mud weight was cut by gas, sheen on the pits, etc. Because of the time plot I avoided a known water sand below 2,312 in this well. I called for casing delivery the same time I called the open hole loggers. After a short trip and circulating I strapped the drill pipe and BHA out of the hole and found 2.5 feet of error in the measurements, which then put my time log to within 1.5 to 2.0 feet of the induction log. What the hell...that's pretty close.
Its old school but puts you in touch with the well, start to finish, the way it should be for any drilling consultant, particularly if you have your own money plopped down on the damn thing. From the primary pay at 2,257 feet the well was ultimately perforated underbalanced from 2,258 to 2,264 feet with 6 shots per foot, no stimulation. It IP'd for 37 BOPD and no water on rod lift. Its now nearing payout and on its way to a very, very healthy ROI.