Full text loading...
-
Correlation Between Spatial and Magnitude Distributions of Microearthquakes during Hydraulic Fracture Stimulation
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 75th EAGE Conference & Exhibition incorporating SPE EUROPEC 2013, Jun 2013, cp-348-00554
- ISBN: 978-90-73834-48-4
Abstract
Seismic and microseismic event populations can be characterized by their spatial and magnitude distributions. The magnitude distribution is described by the Gutenberg-Richter b value. The spatial distribution can be described by the two-point correlation coefficient, Dc. We observe spatio-temporal variations in both b and Dc during hydraulic fracture stimulation in the Cotton Valley tight gas reservoir. We find that during the initial stages of the fracture stimulations, b is high while Dc is low, implying that deformation is dominated by smaller events clustered at points near the injection well. As injection progresses, b decreases and Dc increases. We investigate correlation between b values and Dc, which can be indicative of the style of fracturing. Initially, b and Dc are negatively correlated, consistent with mechanical weakening during the early stages of fracturing. As the stimulation progresses, b and Dc become positively correlated, consistent with later stabilization of the fractures and mechanical hardening when the induced fracture intersects a pre-existing fault. The mechanism of hardening may be crack blunting while propagating into a pre-existing fractured or damaged zone.