Traditional radioactive tracers pose risks
Traditional proppant placement evaluation in hydraulic fractures utilizes detection of radioactive (R/A) tracers that are manufactured in nuclear reactors and then shipped to the wellsite and pumped downhole with the frac slurry. Although this technique has proven useful, it involves environmental, safety, and regulatory issues.
Alternative technology offers non-radioactive (NRT) tracers
Recently a new technology has become available that offers a viable alternative to radioactive tracers. The new technology utilizes a non-radioactive ceramic proppant that contains a high thermal neutron capture compound (HTNCC). This high thermal neutron capture compound is in sufficiently low concentration so as not to affect proppant properties. The non-radioactive tracer proppant (CARBONRT) is detected using standard pulsed neutron capture tools or compensated neutron tools.
Advantages of new method
First, the HTNCC tag material is inseparably incorporated into each ceramic proppant grain during manufacturing. This ensures that tag material will be present in direct proportion to the amount of proppant. Traditional R/A taggants are added to the proppant slurry flowstream in very low concentrations during pumping, thereby providing the possibility for non-uniform R/A distribution in the slurry. This can lead to “false positives” when the presence of merely a few highly radioactive particles near the wellbore can incorrectly suggest the presence of a significant fracture.
Second, and more important, this new NRT methodology utilizes only inert materials in the frac slurry, thereby eliminating the hazards and regulatory issues associated with handling, transporting, pumping and flowing back radioactive materials, hence providing a much more environmentally and logistically friendly option.
Presented: SPWLA 54th Annual Logging Symposium, June 22-26, 2013
Author(s): Robert Duenckel, Xiaogang Han, Harry D. Smith Jr.