But just wrapped a nodal 3D in Reeves County with 25 m node spacing, 50 m VP spacing, and 4–80 Hz, 14 s sweeps; ran 2–10 Hz acoustic FWI on field shots before RTM and saw cleaner Wolfcamp channel edges and about 18 ms tightening around 2.7 km. For those who’ve tried similar land workflows, did that uplift persist after full anisotropic RTM, or are we mostly seeing near-surface corrections that refraction + surface-consistent statics could deliver — and would you push FWI to 12–15 Hz with this sweep?
Did similar in Loving Co.: early 2–8 Hz acoustic FWI cleaned channel edges and about 12 ms RMO persisted after TTI RTM once we tapered updates below Wolfcamp and ran a quick ε/δ scan; your ‘18 ms tightening’ should stick if anisotropy isn’t being soaked into isotropic FWI. If low‑freq S/N dips near 2.7 km, it can unwind — mask to long wavelengths and spot‑check a blind well, like cleaning your glasses without bending the frame.
On a Ward Co. nodal 3D, early 1.5–9 Hz viscoacoustic FWI on field shots gave about 10–12 ms tightening at 2.6–2.9 km and about 60–70% of that stuck after VTI RTM once we nudged shallow η and applied 3–5 ms receiver statics — like tightening a loose guitar string. @gabriel94’s point is spot on: keep ε/δ frozen during FWI, feed a consistent pilot and Q, then do a quick ε/δ scan; otherwise anisotropy leakage can undo the apparent uplift.
On a Reeves nodal patch, the early 2–10 Hz field-shot FWI carried through after full TTI RTM when we capped offsets at about 6 km and “froze ε/δ in FWI, then nudged them with a short tomo.” If we let FWI chase shallow Q or anisotropy, the apparent uplift melted away — RTM loosened it back up like a drumhead in humidity.