SC DrillTechKnowledge · Reference
Glossary & nomenclature
Every symbol, term and unit used across the site — solids control, drilling fluids and waste management — defined in plain field language.
Metrics & symbols
η — Removal efficiencyShare of drilled solids removed by the surface equipment before they recirculate. Field-typical 30–70%; >70% is healthy.
k — Build ratioVc/Ve: fluid actually built versus the dilution-only volume that would have been needed. Lower k means equipment is doing the work.
h — Feed headHydrocyclone inlet energy, in feet of fluid: h = 19.2·p/ρ. Target ≈ 75 ft for desilters.
G — G-forceAcceleration relative to gravity. Shaker/centrifuge: G = N²·s/70,414 (s = stroke for a shaker, bowl diameter for a centrifuge).
TOR — TurnoverTime for an agitator to move a compartment’s whole volume: TOR = (V/Q)×60, in seconds. Typical band ~40–85 s.
v — Line velocityFlow speed in a line: v = 0.4085·Q/d² (ft/s). Working band ~4–8 ft/s.
LGS — Low-gravity solidsDrilled formation solids (~2.6 SG). The quantity solids control exists to remove; held below ~5–6% by volume.
HGS — High-gravity solidsWeighting material, chiefly barite (~4.2 SG). Wanted in the mud; recovered, not discarded.
OOC — Oil on cuttingsOil retained on discarded cuttings. Vertical dryers reach ~3–5%; thermal methods (TCC) below 1%.
Cut point (D100)Particle size, in microns, at which a screen or cone retains essentially all larger solids.
ConductanceHow freely fluid passes a screen, in kD/mm. Trades off against cut point — finer cut, lower conductance.
MBTMethylene Blue Test — measures reactive (bentonite-equivalent) clay; a rising MBT signals dispersing colloidal solids.
RetortLab test that heats a mud sample to read its oil/water/solids split (API RP 13B-1/13B-2).
Equipment
Shale shakerFirst-stage vibrating screen; coarsest cut. Motion may be linear or balanced-elliptical; runs ~4–8 g.
DesanderLarger hydrocyclone removing sand-sized solids; runs on feed head, no moving parts.
DesilterSmaller hydrocyclone reaching the silt range; needs ~75 ft feed head to cut.
Mud cleanerDesilter cones over a fine screen — recovers barite on weighted mud while rejecting fine drilled solids.
Decanter centrifugeHigh-speed bowl + scroll; finest cut. Low speed recovers barite, high speed dewaters fines.
DegasserStrips entrained formation gas from returning mud; sits after the shakers and before the cyclones.
Cuttings dryerVertical centrifuge (OBM) or high-G shaker (WBM) that reclaims fluid and dries the discard.
TDU / TCCThermal Desorption Unit / Thermomechanical Cuttings Cleaner — heat-based cleaning to very low residual hydrocarbon.
CRICuttings Re-Injection — grinding waste to a slurry and pumping it down a dedicated disposal well.
Standards
API RP 13CDrilling-fluid processing-systems evaluation; labels shaker screens by cut point and conductance (ISO 13501; revises API RP 13E).
API RP 13B-1 / 13B-2Field testing of water-based (13B-1) and oil-based (13B-2) fluids — home of the retort and retention-on-cuttings methods.
API RP 13DRheology and hydraulics of drilling fluids.
EPA Method 1674Regulatory method (40 CFR 435) for base fluid retained on cuttings, derived from API RP 13B-2.
Units
ppgPounds per gallon — mud weight (density).
psi / ftPounds per square inch (pressure) and feet (head). 1 psi ≈ 19.2 ft ÷ ρ(ppg).
µm (micron)One-millionth of a metre — the unit of particle size and screen cut point.
SGSpecific gravity — density relative to water (barite ≈ 4.2, drilled solids ≈ 2.6).
bblBarrel (42 US gallons) — the unit of fluid and waste volume.