Retention on cuttings is a retained-fluid measurement, not a visual dryness judgement. For US offshore synthetic-base-fluid discharge, the compliance method is EPA Method 1674, a retort chamber method derived from API RP 13B-2 practice.
What ROC Measures
In drilling-waste work, ROC is used to describe fluid retained on discharged cuttings. For synthetic-base-fluid discharge compliance, the critical value is base fluid retained on cuttings, measured on the required wet-cuttings basis for the fluid class and permit.
EPA Method 1674 Basis
EPA Method 1674 uses a known mass of cuttings in a retort chamber. The sample is heated, recovered liquids are condensed, and the non-aqueous base fluid and water are measured separately. That separation is the reason the method can support a base-fluid retained result.
BFROC (%) = (mass of NAF base fluid / mass of wet cuttings sample) x 100Report the result on the exact regulatory or permit basis for the fluid class and location.Regulatory Context
In the US offshore SBF framework, the retained-base-fluid limits are class-specific. Commonly cited examples include 6.9 g base fluid per 100 g wet cuttings for C16-C18 internal olefin and 9.4 g per 100 g wet cuttings for specified ester classes. These values should not be presented as global NAF limits.
Field Sampling Discipline
| Step | What to control | Why it matters |
|---|---|---|
| Sample stream | Shaker discard, dryer discharge or treatment outlet clearly identified | Different streams answer different questions |
| Sample timing | Collect fresh representative material | Drainage and evaporation distort retained-fluid results |
| Retort measurement | Separate base fluid and water volumes/mass as specified | Compliance depends on base fluid, not total wet/dry loss |
| Reporting basis | Fluid class, wet-cuttings mass basis and permit condition | Prevents applying one regional limit globally |
Operational Interpretation
ROC/BFROC trends help diagnose overfeeding, screen-basket wear, poor dryer residence time, cold or viscous feed, effluent backup and treatment-train limits. The number should be read together with feed rate, solids loading, fluid type and discharge stream.
Key Takeaway
Use retort-based base-fluid measurement for regulatory ROC/BFROC claims. Wet/dry loss can be a rough field observation, but it cannot identify how much retained material is base fluid versus water.
