Weekly · Technical Field Insights · Nov 2026 · W13 · 7 min read

The rig solids-control audit: what to measure and why

Over three months we built the pieces: mass balance, shaker settings, cyclone tuning, centrifuge levers, mud rheology, waste accounting. This month we assemble them into the deliverable that ties it all together — the rig solids-control audit. This week: what to measure, why each number matters, and how an audit turns a pile of readings into a decision.

Written by Othman Soliman — Founder, SC DrillTech · 26+ years in solids control, drilling fluids & waste management. Grounded in API RP 13C practice and field auditing.

Why audit at all

An audit is not paperwork — it is the difference between "the equipment is running" and "the equipment is performing." Every issue we have covered can look fine on a walk-round and still be quietly costing money: a shaker under 4 G, a cyclone roping, a centrifuge discarding barite, LGS creeping up. An audit is a structured, repeatable measurement of the whole train against defined acceptance criteria, so performance becomes a number you can defend to an operator and trend over time — not an opinion that changes with whoever is on tour.

What to measure — the checklist

A complete solids-control audit walks the train in order and captures both settings and outcomes:

System overview — active volume, mud type and weight, LGS%, PV/YP/gels, and the dilution used over the interval (the mass-balance inputs).
Shakers — screen API numbers fitted, deck G-force (stroke and RPM), pool position, screen condition, and whether flow is bypassing.
Hydrocyclones — feed head at the manifold, apex discharge (spray vs rope), cone condition, and whether they are correctly on/off for the mud type.
Centrifuge — bowl speed and G, pool (weir) setting, differential, feed rate, and mode (barite recovery vs fines discard) versus the mud.
Outcomes — solids-removal efficiency from the mass balance, LGS trend, and (on NAF) ROC on the discharged cuttings.

Why each number matters

The power of an audit is that the readings interlock. A high dilution volume points you to a low removal efficiency; a low efficiency sends you to the shaker G-force and screen selection; a good shaker with rising ECD sends you to the centrifuge and LGS. Each measurement is a branch in a diagnostic tree the audit walks for you. Recorded in isolation, they are trivia. Recorded together against acceptance criteria, they localise the problem to a specific piece of equipment and a specific setting — which is the whole point.

From readings to a decision

An audit produces three things, in order: a snapshot (every setting and outcome, dated and signed), a diagnosis (which stage is under-performing and why, from the interlocking numbers), and a recommendation (the specific change — this screen, this G-force, this weir setting — with the expected effect). A report that stops at the snapshot is data. A report that reaches the recommendation is engineering. The audit format should force you all the way to the third step.

Make it repeatable

The value compounds when the audit is standardised. Same measurements, same acceptance criteria, same format, every time — so results are comparable across tours, wells and rigs, and a trend emerges. A one-off audit finds today's problem; a standardised, repeated audit finds the drift before it becomes a problem and proves improvement after a change. That is why a defined audit standard beats an ad-hoc inspection: it makes performance a tracked metric, not a periodic surprise.

The takeaway

The solids-control audit is where the whole system comes together: it measures the train end to end, uses the interlocking numbers to localise under-performance, and drives all the way to a specific, defensible recommendation. Do it to a fixed standard and repeat it, and you convert solids control from a thing you hope is working into a metric you manage. Everything in the last three months was preparation for this: measured, structured, and proven — not guessed.

Educational field guidance based on API RP 13C practice and standard solids-control auditing. Acceptance criteria depend on mud, hole and program — verify against your own well and standard before acting.

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This brief is the field summary. For the full reference, see: