Cuttings re-injection (CRI) takes drilling waste, converts it into a pumpable slurry, and injects it under pressure into a permeable formation — either the well annulus or a dedicated disposal well. For offshore zero-discharge operations, it is often the only route for OBM cuttings that are too voluminous to ship to shore.
From solid waste to injected slurry
- Slurrification: cuttings fed into a high-energy grinder with water, creating a homogeneous slurry at 15–25% solids by weight.
- De-trashing: large debris removed before grinding to avoid plugging.
- High-pressure injection: slurry pumped into a casing annulus or perforated disposal well.
Annular vs dedicated disposal well
| Route | Suited to |
|---|---|
| Annular injection | Moderate volumes; no separate well needed |
| Dedicated disposal well | Large volumes; long-term field waste management |
Regulatory requirements
Continuous monitoring of injection pressure, flow rate and slurry density is required. In US offshore context, CRI is managed under EPA 40 CFR Part 435 and requires a UIC permit.
Key takeaways
CRI converts a disposal problem into an engineering problem. Grind the cuttings, create a stable slurry, inject under controlled pressure into a formation with sufficient injectivity, and document the operation. The constraint is always the geology.