Last week in Yuma County, the state hydrogeologic map pointed to uniform fine sand, but a 6-in pilot hole with gamma showed silty interbeds every 3–5 ft, so I cut the screen to 10 ft with 0.020-in slots and went 10/20 gravel to keep entrance velocity under 0.1 ft/s. When your pre-drill survey clashes with cuttings and logs, do you pause for a quick resistivity line or just redesign on the fly?
I’ll usually pause long enough to run a short dipole–dipole resistivity line when gamma shows interbeds; when I can’t, I field‑sieve a bailer grab and shift to 16/30 with 0.015-in slots to hedge against fines. “Trust the hole,” but beware mud skin — give it a quick surge before logging so resistivity isn’t lying. @OP that’s saved me from sanding-in twice while still keeping entrance velocity under 0.1 ft/s.
And on jobs like your 6‑in pilot in Yuma, I drop a 3‑ft “test screen” and do a 10‑minute airlift at the planned rate; if it pushes fines at “0.1 ft/s,” I swap to 0.015‑in and pre‑pack only across the interbedded zones. It adds about 45 minutes and needs a stable hole, but it’s saved me from sand pumping after the cut.