Common Drilling Fluid Additives
Drilling fluid additives can be categorized into several functional groups:
1. Polymers
- Polyacrylamide (PAM): Flocculates drill cuttings, maintains low solids, and prevents wellbore collapse.
- Potassium polyacrylate (K-PAM): Inhibits shale hydration and swelling, preventing wellbore instability.
- Chelated metal polymer (CMP): Increases viscosity and stabilizes the wellbore.
- Film-forming anti-collapse agent (BLC-1): Controls fluid loss and improves lubricity.
- Viscosifier and fluid loss reducer (KF-1): Enhances liquid-phase viscosity and improves cuttings-carrying capacity.
2. Fine Dispersants
- Sodium carboxymethyl cellulose (CMC): Increases viscosity and reduces fluid loss.
- Caustic soda (NaOH): Adjusts pH and promotes clay dispersion.
- Soda ash (Na₂CO₃): Adjusts pH and precipitates calcium ions.
- Silicon-fluoride anti-collapse and fluid loss reducer (SF): Improves fluidity and mud cake quality.
3. Lost Circulation Materials (LCMs)
- Unidirectional pressure sealing agent (DF-A): Used for sealing permeable formations.
- Composite lost circulation material (HD-I, HD-II): Used for fractured formations.
- Bridging and plugging agent (QD-I, QD-II): Used for fractured formations.
4. Weighting Agents
- Limestone powder (CaCO₃): Increases density (≤1.30 g/cm³).
- Barite (BaSO₄): Increases density (≥2.00 g/cm³).
- Calcium bromide (CaBr₂): Used in solids-free completion fluids for density adjustment.
5. Lubricants
- Non-polar anti-sticking lubricant (BLR-1): Reduces friction and prevents differential sticking.
- Synthetic ester lubricant (HCZ): Low toxicity, resistant to high temperature and salinity.
- Graphite: Improves mud cake lubricity and withstands high temperatures.
6. Surfactants
- Sodium dodecylbenzene sulfonate: Reduces surface tension and friction.
- Emulsifiers (e.g., OP-10): Used in oil-based drilling fluids.
7. High-Temperature & Salt-Resistant Additives
- High-temperature-resistant starch (CMS-K FSL): Suitable for high-temperature, high-salinity, and high-calcium environments.
- Thermal and salt-resistant viscosifier and fluid loss reducer (SL-II): Used in deep wells with high-temperature conditions.
These additives are selected and combined based on the drilling fluid system (e.g., water-based, oil-based, polymer-based) and formation conditions (e.g., high temperature, high salinity, unstable formations). For more detailed application data, refer to relevant literature or industry standards.