A solids-control audit is a systematic inspection of the entire surface separation train — equipment condition, settings, plumbing arrangement and operating data — measured against the standard it is supposed to deliver. It is not a checklist for its own sake. Every item on the list corresponds to a failure mode with a cost, and the audit's value is in finding those failures before they run for a section.
What follows is a working audit framework, organised by equipment stage. It is structured around what to look at, what a fault looks like, and what leaving it unfound typically costs.
Shale shakers
- Screen condition: walk each panel and look for holes, worn spots and lifted edges. One holed panel bypasses the whole cut — fluid takes the path of least resistance. Cost of missing it: fines return to the active system for the rest of the section.
- Fluid pool (beach): a pool that runs off the end means the screen is overloaded or too fine for the flow. A nearly dry deck means you can go finer and remove more. Reading the beach costs nothing.
- Motion and G-force: check for vibrator motor symmetry (linear units) and measure or estimate G — a tired motor destroys conveyance before anything trips.
- Bypass gates and possum-belly overflow: an open bypass valve is silent and invisible from the control cabin. Walk the possum belly and confirm every gate is in the right position.
Hydrocyclones (desanders and desilters)
- Feed head: read the manifold gauge and calculate h = 19.2 × p ÷ ρ. Below ~75 ft, the cones are not cutting. This is the single most common and most missed fault on the cyclone train.
- Apex spray pattern: umbrella spray = healthy. Rope-like wet stream = overloaded or low head. Dry plugging apex = cut too aggressive. Walk every cone.
- Blocked or eroded apexes: a plugged apex passes everything to overflow. A worn apex changes the underflow geometry and coarsens the cut.
- Feed pump condition: the impeller is the most common reason head drops. If head has fallen since last inspection and nothing else changed, assume the impeller.
Decanting centrifuge
- Bowl speed and feed rate vs duty: confirm the machine is set for its intended duty (barite recovery or dewatering — not both at a compromise). Check the datasheet against the current settings.
- Conveyor torque: record it and compare to previous readings. Rising torque is cake accumulating — catch it before it packs the bowl.
- Vibration and bearing temperature: write down both. A bearing running five degrees hotter than last week is a warning.
- Flushing log: confirm that flush-at-shutdown is happening and documented. An unflushed bowl on the next start is a vibration trip or a packed bowl.
- Run hours vs generation rate: calculate fines generated from ROP and bit size; confirm the centrifuge is running enough hours to keep up.
Pit system and plumbing
- Weirs and compartment flow direction: trace the fluid path from dirty suction through each removal stage to the clean active pit. Any short-circuit — a removed weir, an open equalising valve — collapses the sequence.
- Agitator operation: confirm all agitators are running in the suction and centrifuge compartments. A still surface means solids on the floor.
- Mud gun coverage: mud guns in the active pit prevent barite sag; confirm they are operating.
- Active volume: record pit volumes at consistent clock times to track whether the system is gaining or losing fluid (a mass-balance input).
Cuttings handling
- Dryer feed rate and OOC: check that the cuttings dryer is being fed at a steady, controlled rate (PCP feed pump), and retort a discard sample for OOC. Eye-assessment of dryness is unreliable.
- Skip or skip-and-ship documentation: confirm waste volumes are being recorded by skip number and weight — the mass-balance close-out and the compliance record depend on this.
- Containment integrity: check for fluid on the cuttings-handling deck, around dryer discharge, and at skip connections. Spills are waste volume and a regulatory event.
The mass balance — the audit's bottom line
Pull the last 24 hours of drilling and mud reports and run a quick mass balance:
If the numbers don't close — if solids generated significantly exceed solids discarded — solids are accumulating in the active system and dilution will follow. This single calculation often surfaces what the equipment walk-around missed.
Key takeaways
A rig audit is not paperwork — it is a structured look at where the system is leaking value, before a section's worth of dilution makes that leak visible on the mud bill. Walk the train in order, write down what you see, calculate feed head and run the mass balance. The cost of an audit is a few hours; the cost of the faults it finds is usually measured in dilution barrels, disposal volume and rig time.
