Tracer eluting proppants for hydraulic fracture characterization

Abstract

Existing fracture characterization methods (e.g., microseismic) detect fractures created during hydraulic fracturing, but cannot determine whether the fractures are propped or not. The goal of this work is to develop a tracer-eluting proppant technique that can indicate the extent of propped fractures. A polymer coating is developed for common proppants which can release a tracer after being placed in a fracture. A small slug of coated proppants can be injected at the end or middle of the regular proppant injection during hydraulic fracturing. The released tracer can be collected during flow back and be used to better understand proppant location in fracture systems. Laboratory-scale batch tracer release experiments show that the tracer release can be triggered by an increase in temperature, salinity or pH. A proof of concept experiment was conducted in a model single fracture system. The tracer was successfully detected in the flow-back fluid and the tracer concentration was accurately estimated by a numerical tracer release model. The location of the tracer eluting proppants can be estimated from the peak tracer time in the flow-back water. This technique can be used for a wide range of proppants and tracers. Different tracers can be used in different stages.