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Engineering Knowledge Library

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Solids control, drilling fluids and drilling-waste management — 96 field-tested articles plus the Mud Plants & Bulk mega-guide, the working knowledge behind the train, written from 26+ years on the rig.

Engineering Calculations 10

Mud cleaner: when to use it
A mud cleaner is desilter cones over a fine screen, built to recover barite on weighted mud. Above ~10.5 ppg a bare desilter dumps barite. When it pays — and when a fine-screen shaker beats it.
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Sizing a hydrocyclone bank
Size the bank to process 100%+ of the flow into its suction tank, not the circulation rate. 10" desander ~500 gpm, 4" desilter ~60 gpm at 75 ft head, plus 100 gpm backflow.
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OBM vs SBM vs WBM solids control
The mud type sets the strategy: cheap WBM runs the full aggressive train; expensive OBM/SBM drop the cyclones for fine screens and a high-speed centrifuge to save the base fluid.
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Vertical cuttings dryer: the basics
Cuttings leave the shaker >12% oil. A vertical dryer (high-G screen centrifuge) recovers base fluid and drops OOC below ~5%.
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Cuttings re-injection (CRI) basics
CRI grinds cuttings into slurry and injects it below a fracture — permanent, contained, zero-discharge disposal. The full chain.
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Zero-discharge solids control
Zero discharge = nothing to the environment. The waste streams, the routes (dryer/CRI/haul), and why solids control decides the cost.
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Cyclone roping: field decision tree
Spray is the target, rope is the fault. Confirm head, then offload upstream, open the apex, add cones — not just crank pressure.
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Centrifuge wet-cake troubleshooting
A sloppy cake = not enough force/time on the beach. Work bowl speed, feed rate, pond depth in order to dry it without losing the cut.
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Top shale-shaker operating mistakes
The shaker sets the load on everything downstream. Flooded, wrong screen, wrong angle, bypass, poor tension, uneven feed — each fix.
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High LGS: root-cause decision tree
Above ~10% LGS the fluid is untreatable. A decision tree that separates a mechanical bypass from an ultrafine overload before you burn mud.
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Runaway dilution cost
Runaway dilution is a removal-efficiency problem, not chemistry. Because dilution costs 3–4× the volume, a few points move six figures.
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Daily solids-control checklist
A tour-by-tour round — shakers, cyclones, centrifuge, mud report, discard — that catches a stage dropping out before the retort does.
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How often to change shaker screens
Screen life runs 20 hrs to 22 days — but it's condition, not the clock. The four signals that say change now.
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What micron does a desilter remove?
A desilter removes ~15–44 micron solids with small 4–5in cones — finer than a desander, coarser than a centrifuge.
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Linear vs balanced-elliptical shakers
Linear: high-G, dry cuttings, more screen wear. Elliptical: gentler (3–4.5G), longer screen life, beats blinding in gumbo.
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What is a good solids-removal efficiency?
SRE runs 60–90%; above 70% is good, above 85% very good — held without dumping expensive mud. Benchmarks explained.
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Drilled-solids generation rate
Calculate how fast the bit makes solids — from hole size, ROP and porosity — to size the train and read removal efficiency.
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Normal drilled-solids percentage
Low-gravity drilled solids should stay below ~5% by volume. What's normal, how the retort splits it, and why 2 points move rig days.
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Oil–water ratio (OWR) from the retort
OWR straight from retort data — the ratio that sets emulsion stability on oil-based mud, with a worked example. API RP 13B-2…
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Chloride & salinity by titration
Chloride and NaCl salinity from a silver-nitrate titration — the formula, strength factors and a worked example. API RP 13B-1…
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Alkalinity Pf, Mf & lime content
What Pf, Mf and Pm mean, carbonate vs bicarbonate, and lime content as 0.26(Pm − Fw·Pf) — worked example. API RP 13B-1…
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LGS vs HGS from one retort
Split total retort solids into drilled solids and barite by a mud-weight material balance at SG 2.6 and 4.2…
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Stokes' Law settling velocity
Why fine drilled solids won't settle in a pit — and why the shaker and centrifuge, not gravity, must remove them…
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Decanter centrifuge G-force (RCF)
RCF = 1.118×10⁻⁵·r·N² — why G-force, not RPM, sets the cut point, with a worked example on an 18-inch bowl…
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Lag time & bottoms-up
Annular volume ÷ pump output — tie the cuttings on your shaker back to the depth they actually came from…
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Cuttings volume generated
How much solid a hole section really makes — hole capacity × interval × (1−porosity), the solids-control and waste load…
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Annular velocity & carrying capacity
AV = 24.5·Q/(Dh²−Dp²) and the transport ratio — hole cleaning vs the solids load hitting your shakers…
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Drilling-waste disposal cost
Turn cuttings volume into a disposal cost — bulk dry cuttings for retained fluid, then × the haul-and-treat rate…
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Equipment Performance & Optimization 11

Feed-pump TDH & system head curve
Total dynamic head, the system curve, and where a feed pump actually runs — so your cyclones get their design head. Worked example.
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Vertical cuttings dryer & ROC
How a vertical cuttings dryer strips base oil off OBM/SBM cuttings, what retention-on-cuttings (ROC) means, and the recovery it delivers.
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Shaker deck angle & conveyance
How deck angle trades fluid throughput against cuttings conveyance, why +3° is the ceiling, and reading the pool and beach to set it.
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Centrifuge bowl tip speed & wear
Why tip speed — not just G-force — sets the mechanical limit and the wear rate on a decanter bowl. v = πDN with a worked example.
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Screen blinding & near-size particles
Why shakers plug: near-size particles wedge and blind screens. Plugging vs blinding, and the opposite fixes for each.
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Feed-pump NPSH & cavitation
The silent killer of cyclone and centrifuge feed. Calculate NPSH available and stop starving your pumps. Worked example.
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Sizing hydrocyclone banks by cone count
How many desander/desilter cones you actually need: 100–125% of suction flow ÷ per-cone capacity, with feed-head target.
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Pump affinity laws
Flow scales with speed, head with the square, power with the cube. Tune feed head without tripping the motor. Worked example.
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Centrifuge sizing by sigma (Σ)
The equivalent settling area that scales a centrifuge from pilot to field. The tubular-bowl formula and the Q/Σ scale-up law.
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Vacuum degasser & gas-cut mud
Why a 50% surface density cut is only ~3% at bottomhole, when to reach for the degasser vs weighting up. Grounded in JPT.
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Agitator sizing & tank turnover
Sizing mud-tank agitators by turnover rate so barite and drilled solids stay suspended instead of sagging. Worked TOR example.
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Shale, Stability & Equipment Efficiency 5

Shale dispersion (hot-roll recovery)
Measure shale reactivity with %R = W1/W0 — and why dispersed shale dumps fines your shakers can't catch. Hot-roll recovery test.
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Shale accretion & bit balling
The accretion bar test, the accretion % formula, and why sticky clay wrecks ROP, torque and the solids reaching surface.
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Drilled solids, ECD & the stability window
How weak solids control raises ECD until it crosses the fracture gradient and the section starts losing mud. Grounded in API RP 59.
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Centrifuge recovery efficiency
The solids mass balance that tells you what RPM won't: how much of the feed solids actually left in the cake.
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Shale shaker capacity & solids loading
Match screen throughput to flow and solids rate — and why reactive-shale cavings surges flood the deck.
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Mud Plants & Bulk Systems 41

★ Complete guide — start here
The full Mud Plants & Bulk pillar: 41 articles across 11 clusters — storage, mixing, bulk, transfer, reconditi…
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Inside a liquid mud plant
A map of the liquid mud plant (LMP): the bulk-silo side, the mixing system, the segregated…
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What a mud plant does that the rig can't
Why drilling-fluid operations are centralised at a liquid mud plant rather than handled at…
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The supply base & offshore logistics
How a liquid mud plant fits the offshore supply base: the flow of bulk and fluids between…
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Mud plant layout & plot plan
How a liquid mud plant is zoned and laid out: the plot plan that separates bulk, mixing,…
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Storage tank farm & segregation
How a mud plant stores finished and in-process fluids: the segregated tank farm with…
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Agitation: keeping mud uniform
Why stored drilling mud must be continuously agitated: the physics of barite settling,…
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Base oil & brine storage
How a mud plant stores base oil and clear brines: hydrocarbon vapour, flash point and fire…
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The mixing & shearing system
How a mud plant mixes and shears drilling fluid: jet hoppers and eductors for wetting and…
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Jet hoppers & eductors
How jet hoppers and eductors disperse additives into drilling fluid: the venturi principle…
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Building & weighting a mud system
How a mud plant builds and weights a drilling-fluid system: starting from base fluid,…
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Bulk silo systems
How a mud plant stores and meters dry bulk: the pressure silo and aerated cone, the rotary…
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Pneumatic conveying & weighing
How a mud plant conveys and weighs dry bulk: dense-phase versus dilute-phase pneumatic…
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Dust collection & control
How a mud plant controls dust: bin vents on silos, central baghouses and filter-receivers…
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Barite & bentonite handling
How a mud plant handles barite and bentonite: bulk receipt and silo storage, the cohesive…
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Bulk transfer to/from vessels
How dry bulk is transferred between a mud plant and a supply vessel: dense-phase conveying…
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Liquid mud transfer operations
How a mud plant moves liquid fluids in operation: tank-to-tank and tank-to-vessel…
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Vacuum units & recovery
How a mud plant recovers spilled and residual fluid: vacuum units that lift dirty fluid…
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Ship-to-shore transfer operations
How fluids and bulk are transferred between a mud plant and a supply vessel: the ship-shore…
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Transfer line cleaning & pigging
How a mud plant clears transfer lines between fluids: why the heel contaminates the next…
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Reconditioning returned mud
How a mud plant reconditions mud returned from the well: removing accumulated low-gravity…
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Solids removal at the plant
How a mud plant removes drilled solids from returned fluid: shale shakers for the coarse…
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Slops collection & segregation
How a mud plant collects and segregates slops: capturing line flushes, sump and bund…
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Drilling waste at the supply base
How drilling waste is handled at the supply base: receiving back-loaded cuttings and waste…
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Wash water & effluent management
How a mud plant manages wash water and effluent: capturing deck and equipment wash-down,…
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The mud plant laboratory
What the mud plant laboratory does: the API RP 13B tests it runs — density, rheology, fluid…
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Quality control before supply
How a mud plant assures quality before fluid leaves: confirming each batch against the…
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Mud plant HSE & hazardous areas
The HSE essentials of a liquid mud plant: hazardous-area classification and ignition…
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Spill containment & environmental
How a mud plant prevents and contains spills: bunding and secondary containment sized to a…
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Confined space & safe handling
Two everyday mud-plant hazards: confined-space entry into tanks and silos with permits,…
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Tank farm design & bunding
How a mud plant's storage tank farm is designed: vertical agitated tanks sized for…
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Piping, manifolds & hoses
The fluid and bulk transfer network of a mud plant: dedicated piping per fluid, manifolds…
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Pump selection
How a mud plant chooses pumps: centrifugal pumps for transfer and circulation,…
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Power, air & utilities
The utilities behind a mud plant: electrical power and distribution to motors and…
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Instrumentation & controls
How a mud plant measures and controls itself: load-cell weigh systems, level, density and…
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Commissioning & installation
What it takes to install and commission a liquid mud plant: civil and mechanical…
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Barite sag in storage
Why barite settles in mud-plant storage and how to prevent it: the physics of sag in static…
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Silo bridging & conveying faults
The common dry-bulk faults in a mud plant: silo bridging and rat-holing, blocked or worn…
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Cross-contamination between fluids
How fluids get cross-contaminated in a mud plant — shared lines and pumps, residual heels,…
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Dust & emissions problems
Dust and emission faults at a mud plant: blinded or failed bin vents, baghouse problems,…
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Transfer & vessel-loading problems
What goes wrong during mud-plant to vessel transfer: slow or blocked bulk and liquid…
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LMP audit & advisory
Independent, vendor-neutral liquid mud plant audits and advisory from SC DrillTech: bulk…
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Solids Control 3

Reactive vs inert solids
Both read as low-gravity solids — but one you inhibit and the other you remove. Treat them the same and you pay…
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Primary vs secondary solids control
The shaker is primary; cyclones, mud cleaner and centrifuge are secondary — dividing the cut by…
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Removal efficiency (η)
Drilled-solids removal efficiency — written η (eta) — is the single most useful number in solid…
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Equipment 10

Mud cleaner vs desilter
The same cones — but the screen underneath decides whether you keep your barite or pay to dump it on weighted…
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Shaker screen API → micron chart
The full API RP 13C cut-point chart, why mesh is obsolete, and how to read a screen…
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Degasser vs mud-gas separator
Entrained gas vs free gas, conditioning vs well control — and the poor-boy naming…
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Hydrocyclone feed head
Hydrocyclones — desanders and desilters — are the only major piece of solids-control equipment …
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The pit train in order
You can buy the best shakers, the sharpest cones and the biggest centrifuge on the market and s…
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Shaker motion and G-force
Two shakers can carry identical API RP 13C screens and perform completely differently — because…
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Desanders and desilters
Desanders and desilters are the same machine at two sizes. Both are banks of hydrocyclones — co…
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The degasser
Of all the equipment in the pit room, the degasser is the one most likely to be misunderstood a…
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Tanks, agitation and turnover
Spend on the best shakers, cones and centrifuge on the market and you can still run a poor soli…
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The mud cleaner
On a weighted mud, a bank of desilters becomes a liability: barite is ground to pass 200 mesh (…
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Method 10

Reading a shaker
Pick a shaker screen by “mesh” alone and you are guessing. Mesh count never described what a sc…
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The sand content test
The sand content test is the cheapest, fastest measurement in the entire mud-check kit — a glas…
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The daily solids-control report
Most solids-control losses are invisible not because they are hard to see, but because no one i…
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Microns, mesh and cut points
Strip solids control down to one sentence and it is this: sorting particles by size, and removi…
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Retention on cuttings (ROC)
Retention on cuttings (ROC) is the mass of fluid clinging to discharged solids after the separa…
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The solids-control rig audit
A solids-control audit is a systematic inspection of the entire surface separation train — equi…
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The methylene blue test
What the MBT tells the solids engineer — how much of your solids load is reactive clay versus inert grind, and what to do…
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The retort test
The most honest instrument on the mud bench — oil, water and solids, and how to split solids into LGS versus barite…
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The fluid-loss test
API and HPHT filtration, what filtrate and cake really tell you, and why your drilled-solids load decides the cake…
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The electrical stability test
How tough your invert emulsion is — the fast ES read, and why water-wet solids quietly drag the number down…
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Centrifuge 7

High-speed dewatering vs barite recovery
A decanting centrifuge is the most flexible machine on the solids-control train — and the most …
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How a decanter centrifuge works
Bowl, scroll, pool and a 2–5 micron cut — the working principle and its two opposite jobs…
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Pool depth & differential speed
The two levers — deep pool for the cut, shallow for volume; low differential for dry cake…
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Centrifuge feed rate & the cut
Feed rate is retention time — your cut-point dial from outside the bowl, balanced against torque…
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Dual-centrifuge setups
Slow then fast — middle-speed keeps the barite, high-speed dumps the fines, in series…
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Why centrifuges fail
The decanting centrifuge is the most capable machine on the solids-control train and the one mo…
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Centrifuge capacity and run hours
A decanting centrifuge that sits idle while dilution climbs is one of the most common and least…
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Drilling Fluids 9

Plastic viscosity & yield point
Two viscometer readings, opposite meanings — PV is your solids gauge, YP your carrying capacity. The Bingham model and the…
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Gel strength & thixotropy
How your mud holds barite when the pumps stop — the 10-second and 10-minute gels, and what the gap between them…
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Bingham vs power law vs Herschel-Bulkley
Three rheology models from the same viscometer — and why the simplest one over-predicts exactly where it…
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OBM vs SBM
Same invert family, different base fluid — and the base decides toxicity, discharge and total…
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Low-gravity solids, the retort, and the dilution they force
Every problem solids control exists to solve comes down to one quantity: low-gravity solids (LG…
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Marsh funnel viscosity
The Marsh funnel is the most-used and most-misunderstood instrument on the rig. It is quick, ru…
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Mud weight, barite and sag
Solids control spends most of its attention on the solids it wants out — but it has an equally …
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Plastic viscosity, yield point and what they tell the solids engineer
To diagnose what solids are doing to the mud, you need two numbers from a rotational viscometer…
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Non-aqueous drilling fluids
Non-aqueous drilling fluids (NADF) — OBM and SBM — change the solids-control job in fundamental…
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Completion Filtration 4

Brine clarity & NTU
What “clean” completion brine actually means — turbidity targets, API RP 13J, and why particle size matters as much as NTU…
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The filter press (DE)
Diatomaceous-earth filtration for bulk solids — precoat, body feed, and where the press sits in the brine train…
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Cartridge & bag filtration units
The final polish to NTU spec — micron ratings, nominal vs absolute, Beta-rating and coarse-to-fine staging…
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Brine filtration troubleshooting
Hitting NTU without killing throughput — blinding, breakthrough, DE release and the staging that fixes them…
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Regional / MENA 4

Drilling waste disposal: GCC & MENA
Where Gulf drilling waste goes — CRI, thermal, landfarming, evaporation, and the move to zero discharge…
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Onshore desert operations
Evaporation pits, landfarming, CRI and thermal — running desert waste so the climate works for you…
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Cuttings disposal routes
Injection, thermal and land — the real routes for drill cuttings and how to choose between them…
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Oil on cuttings & discharge limits
The OSPAR 1% limit, EPA no-free-oil rule and GCC zero-discharge — the number that decides where waste goes…
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DWM 8

Coagulation vs flocculation
Two chemical steps that let a centrifuge pull clean water from waste mud — charge neutralization, then polymer…
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Cuttings dryer vs centrifuge
Two machines, one recovery train — the dryer recovers the fluid, the centrifuge cleans…
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Five drilling-waste-management mistakes that quietly cost you money
Drilling waste management is where solids control meets the environment — and the budget. The h…
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Cuttings dryers
On an oil- or synthetic-based-mud well, the cuttings dryer is usually the single biggest lever …
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Dewatering chemistry
A dewatering unit is only as good as the chemistry feeding it. The centrifuge, the filter press…
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Closed-loop and zero-discharge
A closed-loop system removes the one thing solids control has always quietly leaned on: the res…
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Cuttings re-injection (CRI)
Cuttings re-injection (CRI) takes drilling waste, converts it into a pumpable slurry, and injec…
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Thermal desorption units (TDU)
The vertical cuttings dryer drives OOC to roughly 3–5%. For many regulatory environments that i…
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Solids Control Performance 4

Solids control performance KPIs
The six numbers that decide it — SRE, LGS, dilution ratio, ROC, screen life and cost per foot…
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Solids loading & ROP
The feedback loop — drilled solids you don’t remove slow the bit, and the slow bit makes more solids…
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The cut-point cascade
Shaker to centrifuge — each stage catches a finer band, and a dropped band is where LGS climbs…
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Screen conductance & utilization
Cut point vs conductance, NBA and utilization — the API RP 13C numbers that set the shaker’s ceiling…
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Performance 5

D50 vs D100 cut point
A cut point is one number on a curve — D50 is the median, D100 is total separation, and which one changes the…
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Efficiency that keeps the bit turning
Solids control is often filed under “cost centre” — equipment you run because you have to. That…
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Differential sticking
Differential sticking is the most expensive single failure mode in drilling — and one of the mo…
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Solids control on HPHT wells
HPHT drilling — BHT above 150 °C and/or pore pressures exceeding 10,000 psi — is where the soli…
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ECD management
Equivalent circulating density (ECD) is the effective mud weight the formation sees while the p…
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Economics 1

Cutting dilution cost
Most solids-control losses are invisible because the system never stops running. Nothing trips,…
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Compliance 1

Drilling-waste environmental compliance
Environmental compliance used to be paperwork the HSE department handled after the well was dri…
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History 1

The history of solids control
Most people assume solids control started on a drilling rig. It didn’t. The equipment standing …
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