“Cuttings” and “drilled solids” get used as if they mean the same thing. They don't — and the difference is the whole game in solids control. Both come off the bit as the same rock, but their fate splits at the shale shaker: what you catch and throw away is a cutting; what slips through and stays in the mud is a drilled solid. One is waste you handle; the other is contamination you fight.
Same origin, opposite fate
Every particle starts identically: rock crushed or sheared off the formation by the bit and lifted to surface by the mud. What happens next is what separates the two terms. The drill cuttings are the fragments the surface solids-control equipment separates out on the first pass — the discrete, visible rock that leaves over the shaker screen and becomes drilling waste. Industry references put it plainly: cuttings separated from the fluid at surface, plus some unrecoverable mud, are the major source of drilling waste.
Drilled solids are what is left behind. As the standard definition goes, drilled and formation solids sized smaller than the solids-control equipment can remove are reported as drill solids — and some quantity of them accumulates in the fluid and must be removed mechanically or reduced by dilution. So the shaker is the fork in the road: coarse enough to catch = a cutting, out it goes; fine enough to pass = a drilled solid, into the active system it goes. Knowing which fraction you are actually generating is what Rig IQ is built to quantify from your shift data.
Why the drilled-solids fraction is the enemy
Cuttings are a handling problem — you convey them, dry them, and dispose of them. Drilled solids are a performance problem, because they are inside the fluid driving plastic viscosity and gel strengths up, abrading pumps, and forcing dilution. Worse, they do not stay the size they entered: solids that survive the first pass are mechanically degraded by the bit, reamers and mud pumps on every circulation, grinding progressively finer until they are too small for any mechanical device to catch.
That is why the governing principle is to remove solids as far upstream as possible — catch them while they are still cuttings, before they degrade into un-removable drilled solids. Low-gravity solids sit around specific gravity 2.6, close enough to many drilled solids that separating them from the barite (SG 4.2) you want to keep is a genuine engineering problem, not a switch you flip. Tracking how much of your generated solids is ending up as drilled solids in the mud — versus leaving as cuttings — is exactly the balance Rig IQ reports on.
The size line and the economics
There is a rough size hierarchy worth carrying in your head: large drilled solids — cuttings — run about 440 microns and up, and the classification descends through the mechanically removable range down to colloids at half a micron and smaller (for scale, one inch is 25,400 microns). The shaker takes the top of that range; desanders, desilters and the centrifuge chase progressively finer fractions. But once a particle degrades into the ultrafine and colloidal range, no mechanical device removes it, and dilution is the only lever left — at three to four barrels of fresh fluid per barrel of retained solids.
So the economics follow the terminology directly. A cutting removed on the first pass costs you a screen and some disposal. The same particle, if it becomes a degraded drilled solid, costs you dilution, fluid loss, pump wear and rig time — many times more. The entire justification for a tuned removal train is to convert as much of your solids as possible into cuttings you discard, and as little as possible into drilled solids you carry. Putting real numbers on that trade — solids generated, fraction removed, dilution avoided — is what Rig IQ does on live data.
The distinction
Drill cuttings: the rock the surface equipment removes on the first pass (≈ 440 µm and up). Discrete, visible → drilling waste you handle and dispose of.
Drilled solids: the finer fraction too small to remove that slips through and accumulates in the fluid. Removed mechanically downstream or reduced by dilution.
Same origin (the bit) — opposite fate (out as waste vs. in as contamination). Both are low-gravity solids (SG ≈ 2.6).
Cuttings and drilled solids are the same rock at different stages. Cuttings are removed at surface on the first pass and handled as waste; drilled solids are the finer fraction that escapes into the mud, degrades with every circulation, and must be removed mechanically or diluted out. The whole point of a tuned removal train is to turn as much as possible into cuttings you discard — and as little as possible into drilled solids you carry.
Common questions
What is the difference between drill cuttings and drilled solids?
Drill cuttings are the rock fragments the surface solids-control equipment removes on the first pass — discrete, visible material that becomes drilling waste. Drilled solids are the finer fraction, too small for the equipment to catch, that slips through and accumulates in the drilling fluid, where it must be removed mechanically downstream or reduced by dilution. Same origin at the bit, opposite fate.
Are drilled solids and low-gravity solids the same thing?
Drilled solids are the largest component of low-gravity solids (LGS), but LGS also includes added materials like bentonite. Both sit around specific gravity 2.6 — much lighter than barite at 4.2 — which is why separating drilled solids from weighting material is a real engineering problem rather than a simple screen.
Why are drilled solids harder to remove than cuttings?
Because they are smaller and they keep shrinking. Solids that survive the first pass are mechanically degraded by the bit, reamers and mud pumps on every circulation, grinding progressively finer. Once they degrade below roughly 8–10 microns, no mechanical device can remove them and dilution is the only remaining option.
