Darcylog: measurement of permeability on drill cuttings
Domains of application
- Dry and clean cuttings. Size: 1- 5 mm.
- Permeability: 0.05 to 100 mDarcy.
- Minimum volume of 3 cc after cleaning and sieving.
- Porosity > 5%.
- Air is trapped inside the cuttings during an imbibition in a viscous liquid.
- Pressure is applied (10 bars) on the liquid to force it to enter into the cuttings and compress trapped air bubbles.
- Permeability is derived from the transient pressure drop, similar to a well test.
- Darcylog is not a “push-button” apparatus. Interpretation of the relaxation curve requires experience and expertise, and can be difficult in case of mixture of formations during sampling.
- Cuttings are not always representative of the reservoir: high permeability sandstone can be crushed into sand, and cuttings can sometime only represent shale layers.
- Cuttings represent only the “matrix” permeability; fractures and vugs are lost during drilling.