Proppants coated by piezoelectric or magnetostrictive materials, or by mixtures or combinations thereof, to enable their tracking in a downhole environment

Abstract

A method for “tagging” proppants so that they can be tracked and monitored in a downhole environment, based on the use of composite proppant compositions comprising a particulate substrate coated by a material whose electromagnetic properties change at a detectable level under a mechanical stress such as the closure stress of a fracture. In another aspect, the invention relates to composite proppant compositions comprising coatings whose electromagnetic properties change under a mechanical stress such as the closure stress of a fracture. The substantially spherical composite proppants may comprise a thermoset nanocomposite particulate substrate where the matrix material comprises a terpolymer of styrene, ethylvinylbenzene and divinylbenzene, and carbon black particles possessing a length that is less than 0.5 microns in at least one principal axis direction incorporated as a nanofiller; upon which particulate substrate is placed a coating comprising a PZT alloy manifesting a strong piezoelectric effect or Terfenol-D manifesting giant magnetostrictive behavior to provide the ability to track in a downhole environment.

Dependencies are inferred from the claim text.