Seeing 250–500 psi oscillations at about 1 Hz during the first 12 hours of flowback through 3-in surface lines, and the slugs are spiking erosion at the first elbow; OLGA points to density-wave and choke-interaction effects. Has anyone had success damping this with staged choke ramps or adding 10–20 bbl of surge volume, and how did it impact proppant carryover and line integrity?
We knocked down similar about 1 Hz chatter by running a 3-step ramp — ‘26→32→38/64 with 15–20 min holds’ — and adding a 12–15 bbl buffer pot just upstream; sand carryover dropped about 30% and the first elbow quit getting sandblasted. Caveat: hold separator backpressure steady and keep a continuous bleed on the pot or it loads up and the oscillations creep back — how many feet from choke to first elbow?
Saw the same about 1 Hz on 3-in in the first 8–10 hours; what finally settled it was two chokes in series with about a 60/40 ΔP split and keeping 100–150 psi backpressure on the MP separator to damp the loop. @marvin_v1970’s buffer pot helps, but if you skip it, hold line velocity >8 ft/s and purge the sand trap every 20–30 min so carryover stays manageable.
Piggybacking on @renee_b95’s split-ΔP note, the biggest stabilizer for us was detuning the choke controller: add a 25–30 psi deadband, slow the integral (≥60 s), and rate‑limit moves (<1/64 every 10–15 s) so it stops chasing its tail; that cut swings to about 100 psi and trimmed sand bursts without adding surge volume. Minor tradeoff is slightly slower cleanup, so we held about 75–100 psi backpressure to keep drawdown — have you tried a small deadband yet?