By Othman Soliman — Solids Control & Drilling-Waste specialist, 26+ yrs (GCC & MENA). Last reviewed .
WATCH · Watch — trend and planMud system →Illustrative cost exposure ≈ $35k+ / incident
Why it matters
Unyielded or unevenly mixed product means you pay for chemicals that never go to work, chase properties that drift, and risk dead material settling out. It quietly inflates mud cost and muddies every property reading. Cost basis: the headline figure is an illustrative exposure, not a measured incident cost or a validated typical value. No incident-specific inputs are provided for it. Estimate your case as incremental fluid loss or dilution (bbl/day × days × $/bbl), plus incremental waste treatment/disposal and documented NPT (hours × $/hour), avoiding double counting. Record the baseline, duration, fluid cost and verified change before claiming savings.
Likely causes
Eductor / hopper worn or under-powered — poor shear and draw.
Centrifugal mixing pump worn — low head to the eductor.
Agitator undersized / impeller worn for the tank.
Adding product too fast for the shear available.
Insufficient circulation / agitation time to yield.
Adding to a dead, unagitated corner of the pit.
High viscosity hindering blending.
Product needing time / shear to yield (e.g. bentonite).
How to diagnose it
Check eductor draw / hopper performance.
Confirm mixing-pump head and condition.
Check agitator coverage across the tank.
Confirm adequate circulation / yield time.
Sample for unyielded product / fisheyes.
The fix — step by step
Add product at a rate the shear can take — don't dump it.
Restore mixing-pump head; service the eductor / hopper.
Right-size and maintain agitators for full tank coverage.
Allow circulation time for product to yield before judging properties.
Add into an agitated zone; eliminate dead spots (see dead zones).
Confirm it's fixed
✓ Verify: Product fully yielded with consistent properties across the pits; no fisheyes after circulation.
Field note. Most ‘the product isn't working' calls are really ‘the product never yielded.’ Slow the addition, give it shear and time in an agitated zone, and check again before you treat over the top — over-treatment on top of unyielded product just buries the problem and the cost.
The 10 Solids-Control Numbers Every Engineer Must Track — what to measure, the formula, the field target and the red flag. Grounded in API RP 13B-1, RP 13C, EPA 40 CFR 435 & OSPAR.
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