Fluctuation of fracturing curves indicates in-situ brittleness and reservoir fracturing characteristics in unconventional energy exploitation

Reservoir brittleness is a key index to evaluate the fracability and to predict the fracturing characteristics in unconventional energy exploitation. Traditional brittleness indices could only be derived from labo-ratory experiments, which are far from the field conditions and may lead to deviations. In this paper, a fracturing-curve based in-situ brittleness evaluation method is proposed and the in-situ brittleness of Woodford Shale is derived under field stress and temperature conditions. Based on the analysis of real-time micro-seismic data, it is confirmed that the real-time fracturing characteristics can be known by observing the fluctuations in the fracturing curves. Results showed that the in-situ brittleness is much lower than that derived in laboratory experiments. About 78% of micro-seismic events happen at the extreme value and the fastest fluctuation of the fracturing curve. These provide guidance for accurate formulation and real-time optimization of exploitation scheme. (c) 2022 Elsevier Ltd. All rights reserved