Modified drilling starch is the lowest-cost filtration-control additive in water-based drilling, and the default in saturated-salt and high-hardness systems where charged polymers struggle. Ironstone supplies drilling-grade modified starch with a certificate of analysis for every batch.
Drilling starch reduces fluid loss. It is pregelatinized — processed to hydrate in cold water without cooking — so its swollen particles are soft and deformable: they lodge in the pores of the filter cake and deform to seal them, cutting the filtrate. Because starch is non-ionic — the molecule carries no charge — salt does not switch it off, which is why it remains the default filtration additive in saturated-salt and high-hardness systems.
Standard modified starch is the lowest-cost filtrate control for normal-temperature sections and short exposure times. Temperature-stabilized grades are additionally modified or cross-linked for deeper, hotter sections where standard starch degrades and the filtrate climbs mid-section. If your current product carries an “HT” suffix, the temperature-stabilized grade is the one to match. Starch is organic material, so every grade has a temperature ceiling and — especially in lower-salinity systems — can ferment if the mud sits uncirculated without preservative.
| Parameter | Typical value | Basis |
|---|---|---|
| Appearance | Off-white to pale-yellow powder | Visual |
| Moisture | < 10% | — |
| pH (2% solution) | 6.0 – 7.5 | — |
| API fluid loss | ≤ 10 mL (in NaCl brine, per API Spec 13A) | API filter press |
| Viscosity (600 r/min dial) | Low — starch adds filtration, not viscosity | Rotational in brine |
| Ionic character | Non-ionic | — |
| Residue coarser than 2000 µm | None | Sieve |
Typical drilling-grade values. The API Spec 13A criterion for drilling starch is a filtrate of ≤ 10 mL; the certificate of analysis states the exact figures and the test brine for each batch.
Dosage is set by pilot test against your filtrate target in the brine you actually run — starch that performs in fresh water can behave differently in saturated salt, so test in your worst-case brine. We include the technical data sheet with dosage guidance and the temperature rating when we quote.
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.