Darcylog: measurement of permeability on drill cuttings
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DarcyLog: Porosity and Permeability measurements from Drill Cuttings – DarcyLog Commercial Brochure
Measurements on cuttings
Measurements on cuttings (small rock samples of a few mm in length) can improve reservoir characterization when cores are not available. In most wells, properties measured on cuttings are representative of the matrix properties.
Domains of application
- Dry and clean cuttings. Size: 1- 5 mm.
- Permeability: 0.01 to 100 mDarcy.
Cuttings Requirements
- Minimum volume of 3 cc after cleaning and sieving.
- Porosity > 5%.
Principle
- Air is trapped inside the cuttings during an imbibition in a viscous liquid.
- Pressure is applied (10 bar) 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.
Limitations
- 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.
PERMEABILITY MEASUREMENT ON SMALL ROCK SAMPLES, R. Lenormand, F. Bauget, G. Ringot, Society of Core Analysts, paper SCA-2010-A073 – pdf file
