Lithology and Borehole Condition Independent Methods For Locating Tagged Proppant in Induced Subterranean Formation Fractures

摘要

Subterranean formation locations/heights of tagged proppant doped with a high thermal neutron capture cross-section material are determined using data obtained from before and after frac logging passes through a well of a logging tool having near and far neutron dectors. Proppant location inaccuracies arising from changes in lithology between a zone of no interest and a proppant-containing formation zone are made, after any required normalization for a between-log change in borehole fluid, using an observed difference between the near/far detector count rate ratios in the two passes to determine a count rate differential correction to be applied to the before frac detector count rate. The corrected before frac count rate log is then overlaid with the after frac count rate log such that suppression in the after frac count rate log relative to the corrected before frac count rate log indicates the presence of proppant.