Sulfonated asphalt — sodium asphalt sulfonate — is a shale-stability and filtration additive used in both water-based and oil-based mud. Ironstone supplies drilling-grade sulfonated asphalt with a certificate of analysis for every batch.
It is asphalt treated so part of the material becomes water-soluble (as a sodium salt) while part stays oil-soluble. In the mud it does three jobs at once: it stabilizes reactive shale by plating onto the shale surface, it lowers high-temperature filtrate by adding fine deformable material to the filter cake, and it reduces friction between the drill string and the wellbore. One low-cost sack covering three jobs is why it stays on so many procurement lists.
No — and this is a useful check when comparing offers. Genuine sulfonated asphalt does not soften and melt the way raw asphalt or gilsonite does; the sulfonation reaction changes the material. If a product sold as “sulfonated asphalt” quotes a softening point, it may be unreacted asphalt or an asphalt blend rather than true sodium asphalt sulfonate. The parameter that defines the grade is the water-soluble fraction, not a softening point.
| Parameter | Typical value | Basis |
|---|---|---|
| Appearance | Black to brown free-flowing powder | Visual |
| Water-soluble content | ≥ 70% | Water solubility |
| Oil-soluble content | ≥ 25% | — |
| Sodium sulfonate group | ≥ 10% | — |
| Acid-precipitate content | ≤ 15% | — |
| Moisture | ≤ 10% | — |
| pH (solution) | 8.0 – 10.0 | — |
| HPHT filtrate reduction | Stated on the certificate of analysis | HPHT filter press |
Typical drilling-grade values (CAS 68201-32-1). The certificate of analysis states the exact figures for each batch.
Dosage is set to the shale-stability and high-temperature-filtrate targets by pilot test, in the mud system you run. Sulfonated asphalt ships as a bagged powder. We include the technical data sheet with dosage guidance and confirm the pack on the quotation.
Indicative CIF price on request; indicative FOB ranges appear in the monthly Price Letter. For a firm price, send your volume and port on WhatsApp.