Accurate assessment of intervals receiving proppant and the determination of near-wellbore fracture heights are valuable in assessing and optimizing stimulation strategies. Proppant-placement evaluation in hydraulic fractures has traditionally involved the detection of radioactive (R/A) tracers pumped downhole with the proppant. However, as environmental regulations regarding this technique have tightened, and with increased scrutiny by the public and regulatory bodies of the industry in general and hydraulic fracturing in particular, the need for an alternative to R/A tracers has become paramount.
A new technology for assessing intervals receiving proppant and determining fracture heights by use of a non-R/A detectable proppant has been introduced recently. The technology has found global acceptance and has proved to be a robust and accurate method of locating proppant in the near-wellbore region. In addition to eliminating the safety and environmental concerns with R/A tracers, this new method also provides a permanent indication of the proppant location near the wellbore. Unlike traditional R/A tracers that must be logged before the radioisotopes completely decay, this new method will allow investigation of the proppant pack many years or decades in the future, which will provide critical information during remedial or redevelopment work that cannot be determined with conventional approaches.
A review of the current state of regulatory impediments to the use of R/A tracers in key producing regions around the world is presented, highlighting the need for an alternative diagnostic technology. The technology used in the application of the non-R/A detectable proppant is described, and comparisons with other fracture-diagnostic technologies are presented. Several case histories are shown that illustrate various applications of the technology in regions around the globe. These case histories include applications performed in Asia, the Middle East, Europe, and North America. In addition to identifying proppant location and fracture height, this technology can be used in other applications such as the evaluation of gravel-pack quality. If the current trends in regulatory actions related to hydraulic fracturing continue, it is anticipated that the use of R/A tracers will be restricted to fewer and fewer locales. At the same time, reliable fracture diagnostics for optimization of hydraulic fracturing, from both a wellperformance and a cost-control standpoint, remains extremely important.