Solids control is usually treated as an overhead — a box of equipment that runs and costs money. Cost per foot flips that: it turns solids control into a measurable performance number you can defend, compare and improve. Every barrel of drilled solids you remove mechanically avoids several barrels of expensive dilution, and the difference between a good system and a poor one is measured in six figures a well. Here is what goes into cost per foot, and why it is the number that proves solids control pays.
What cost per foot actually captures
Cost per foot is the total fluid and solids-handling spend for a section divided by the footage drilled — and its value is that it forces every hidden cost onto one line. Those costs fall into a few buckets: the dilution spend (clean fluid and chemicals built into mud and then discarded to hold solids down), the disposal cost of the waste that leaves the rig, the consumables and running cost of the equipment (screens, power, maintenance), and the wider penalties poor control creates. Put them over footage and you get a number that compares one well, section or system against another.
The reason it matters is that the biggest cost is the least visible. Dilution doesn’t show up as a solids-control line item — it hides in the daily mud spend — yet field figures put the savings from good solids control at a 50–70% reduction in dilution, which on an oil-based mud at a few hundred dollars a barrel can exceed half a million dollars on a single deep well. Cost per foot is what drags that hidden dilution into the light. Building that number from the real streams — what was diluted, disposed and run — is exactly what Rig IQ is designed to do.
Mechanical removal versus dilution: the barrel math
The engine under cost per foot is a simple, brutal comparison: mechanical removal of solids costs less than dilution, and it isn’t close. When you remove a barrel of drilled solids on the shakers, cyclones or centrifuge, it leaves in a concentrated discard. When you remove it by dilution, you don’t remove a barrel — you have to add many barrels of built mud and discard the surplus to bring the concentration down. Leon Robinson’s classic analysis makes it concrete: at typical mud costs, mechanically removing a modest volume of low-gravity solids can save tens of thousands of dollars in avoided dilution, because each barrel of solids left in demands several barrels of dilution to manage.
That ratio is the whole economic case for the equipment. Every point of removal efficiency you gain converts directly into dilution you never had to build — and dilution is the expensive exit. So a rising cost per foot is almost always a removal problem: solids the equipment missed are being diluted out instead, at a multiple of the cost. Reading cost per foot back to the removal efficiency that drives it is precisely the connection Rig IQ makes on live data.
The costs beyond the mud
Dilution and disposal are only the direct costs; poor solids control bills you again indirectly. Abrasive drilled solids wear the circulating system — field data shows good solids control roughly doubling pump-liner life and extending bit life 20–30% — so every hour of dirty mud is money spent on parts and trips. High solids slow the bit: reducing low-gravity solids from around 10% to 5% has been shown to lift rate of penetration 20–30%, and faster drilling directly cuts rig time that runs to tens or hundreds of thousands of dollars a day. And un-removed fines raise rheology and ECD, which in a tight window invites losses.
This is why cost per foot, done properly, includes more than the mud invoice — the wear, the ROP penalty, the disposal volume and the risk all trace back to the same drilled solids. A clean system pays for itself several times over, but only if you count all the lines. Putting the full cost — direct and indirect — over footage is the honest way to prove a solids-control investment, and it’s the calculation Rig IQ is built to run rather than leaving the value invisible.
Cost per foot, in short
Cost per foot = total fluid + solids-handling spend ÷ footage drilled. Forces every hidden cost onto one comparable line.
Buckets: dilution (built mud discarded) + disposal + consumables/running + indirect penalties.
The engine: mechanical removal « dilution. One barrel of solids left in demands several barrels of dilution — so rising cost per foot = a removal problem.
Indirect: pump-liner life ~×2, bit life +20–30%, ROP +20–30% (LGS 10%→5%). Good solids control saves 50–70% of dilution — six figures a well.
Cost per foot is the total fluid and solids-handling spend for a section divided by footage — it makes solids control a measurable performance number. Its biggest component is usually dilution, which hides in the daily mud spend; good solids control cuts dilution 50–70%, saving six figures a well. The core economics: mechanical removal beats dilution because one barrel of solids left in demands several barrels of dilution to manage. Done properly it also counts the indirect costs — pump and bit wear, ROP loss, ECD-driven losses — which all trace back to drilled solids.
Common questions
What goes into solids-control cost per foot?
It is the total fluid and solids-handling spend for a section divided by the footage drilled. The components are the dilution cost (clean fluid and chemicals built into mud then discarded to control solids), the waste disposal cost, the equipment consumables and running cost (screens, power, maintenance), and the indirect penalties of poor control — accelerated pump and bit wear, lost rate of penetration, and ECD-driven losses.
Why is mechanical removal cheaper than dilution?
Because removing a barrel of drilled solids mechanically discharges it in a concentrated stream, while removing it by dilution requires adding many barrels of built mud and discarding the surplus to bring the concentration down. So one barrel of solids left in the system demands several barrels of dilution to manage. Every point of removal efficiency gained is dilution you never had to build — the expensive exit avoided.
How much can good solids control save?
Field figures put the dilution reduction from good solids control at 50 to 70 percent, which on an oil-based mud at a few hundred dollars per barrel can exceed half a million dollars on a single deep well. Beyond dilution, it roughly doubles pump-liner life, extends bit life 20 to 30 percent, and can raise rate of penetration 20 to 30 percent by cutting low-gravity solids — each of which cuts rig time and cost further.
