An oil-based mud (OBM) is an invert emulsion — water droplets suspended in an oil phase — and it needs a specific set of additives to build and hold that structure. Ironstone supplies the core OBM additives — emulsifiers, organophilic clay, wetting agents, and filtration-control products — with a certificate of analysis for every batch. Because OBM additives carry the performance of the whole system, we quote them with technical data and a defined trial plan, not just a price.
| Additive | Job in the system |
|---|---|
| Primary and secondary emulsifiers | Form and hold the water-in-oil emulsion so the water phase stays as fine, stable droplets. |
| Organophilic clay | Builds viscosity and suspension in the oil phase — the core rheology product. |
| Wetting agent | Keeps solids and weighting material oil-wet so they stay suspended and do not water-wet and settle. |
| Filtration-control additive | Tightens the filter cake at temperature to cut high-pressure filtrate. |
| Lime | Maintains alkalinity and supports the emulsifier chemistry. |
Ordinary drilling bentonite needs water to work and does nothing in oil. Organophilic clay is bentonite or hectorite whose surface has been treated so it disperses in oil instead of water. Once dispersed with enough shear, the treated clay platelets build the gel structure that gives the invert its viscosity and its ability to suspend barite and cuttings — the same role bentonite plays in a water-based mud, but in the oil phase. It is usually the core rheology product of the whole formulation. Our organophilic clay page covers grades and selection.
More carefully than a water-based commodity, because the failure cost is higher — a disturbed emulsion is a well problem, not a refill problem. The honest sequence is: build a lab invert matching your field formulation and base fluid, run the candidate and the incumbent side by side at equal dosage — high-pressure filtrate at your bottom-hole temperature, full rheology after hot-rolling, and electrical stability — then a pilot volume in a low-risk section before switching the program. Our equivalents pages for ECOTROL RD, BENTONE 38 / VG-69, and VERSATROL / BARABLOK set out exactly what each class must match.