SC DRILLTECH · COMPLETE GUIDE

Drilling fluids, kept in spec.

Drilling fluid does the work of the well — it carries cuttings, balances pressure, cools the bit and stabilises the hole. Almost every property that matters is made or wrecked by solids: how many, how fine, how well controlled. This guide connects the fluid you test in the mud lab to the equipment that keeps it in spec, and links out to the fundamentals and to each property in depth.

Mud types in one pass

Water-base mud (WBM) — cheapest and most common; tolerant of full hydrocyclone use on unweighted systems. Non-aqueous fluids (NAF) — oil- and synthetic-base mud for shale stability, high temperature and lubricity; expensive, regulated, and unforgiving of poor solids control because every barrel lost to dilution or ROC is costly. Where solids control matters most on NAF →

The properties solids control protects

Density (mud weight) — set with barite; drilled solids creep it up uncontrollably if not removed, and barite that settles causes sag. Mud weight, barite and sag →

Rheology (PV / YP) — plastic viscosity tracks solids loading almost directly; a rising PV is usually a solids-control problem before it’s a chemistry problem. PV, YP and what they tell solids control →

Low-gravity solids (LGS) — the drilled fines you’re trying to keep out; the retort and a simple mass balance reveal how much dilution they’re forcing. LGS, the retort and dilution →

Funnel viscosity — the quick field check; what 46 seconds actually means. Marsh funnel viscosity →

Particle size distribution ties it together

Every property above is really a statement about particle size. The shaker, the cones and the centrifuge each own a band of the PSD curve; what one stage misses, the next must catch — or the fluid carries it and dilution pays. Reading the curve, not just the retort, is how you find where the solids are escaping. The Drilling Fluids Fundamentals page covers the testing and rheology in depth.

From the lab back to the machines

A mud check is a to-do list for the solids-control train. PV up? Read the centrifuge and cones. Weight creeping with no barite added? Drilled solids aren’t coming out — check the shakers. Sag appearing? Look at low-side dynamic settling and centrifuge balance. Every fluid symptom points back to a machine, and the Troubleshooting Center takes it from there. It all starts with solids control done right.

Frequently asked

How do drilling fluids relate to solids control?

Most drilling-fluid properties — density, plastic viscosity, yield point and sag — are controlled by how well solids control removes drilled solids. Poor solids removal shows up first as rising PV and uncontrolled mud weight.

Why does plastic viscosity rise?

Plastic viscosity tracks solids loading. A steady rise usually means the solids-control train is letting fines accumulate — a centrifuge or hydrocyclone problem — before it is a chemistry issue.

What are low-gravity solids (LGS)?

LGS are drilled fines (clays, silt) with low specific gravity that you want to remove. High LGS forces dilution to keep the mud in spec, which is why removal efficiency matters.

Why is solids control more critical on oil-base mud?

Non-aqueous fluids are expensive and regulated. Every barrel lost to dilution or stuck to cuttings as ROC costs far more than on water-base mud, so removal efficiency and dryer performance matter more.

Go deeper

Drilling Fluids Fundamentals →Particle Size Distribution →PV & YP article →Solids Control guide →

Want this applied to your rig?

Send your shift data — we read it against API RP 13C and tell you exactly what to change. Remote, vendor-neutral.

Request a remote evaluation →