Radioactive tracers are used to evaluate fluid and proppant placement during hydraulic fracturing. Small amounts of radioactive material are embedded in the proppant or added to specific stages, allowing their locations to be detected after the treatment using gamma-ray logging tools.
Modern tracers are typically embedded in ceramic proppant particles, which behave similarly to conventional proppants. This improves measurement reliability compared to earlier tracer methods that suffered from wash-off or signal loss.
After the treatment, a spectral gamma ray logging tool is run in the wellbore to detect radiation emitted by the tracers. By analyzing the energy levels of the detected signals, different tracers can be identified, and their distribution along the wellbore can be determined.
Radioactive tracers are used to:
- Measure fracture height near the wellbore
- Evaluate stage efficiency and zonal isolation
- Assess proppant placement and distribution
- Identify connectivity between stages or clusters
Different isotopes with short half-lives (on the order of months) are used to provide sufficient measurement time without long-term environmental impact. These tracers are often placed at different stages or within different parts of a stage to distinguish fluid and proppant placement.
Overall, radioactive tracers provide a quantitative method for evaluating near-wellbore fracture behavior and improving treatment design.
