Analyses of Microseismicity and Induced Earthquakes During Hydraulic Fraction to Infer Tress Changes and Interactions from Case Studies

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

It is known that hydraulic fracturing, an unconventional approach of oil & gas exploration, may lead to the occurrence of induced earthquakes due to multiple factors. During hydraulic fracturing process, liquid is injected into perforations to break the rock and create fracture. The microseismicity cloud (typically have magnitudes below 0) can be used to infer the fracture geometry and distributions. However, occasionally, pre-existing faults can be re-activated due to stress changes from hydraulic fracturing or fluid leakage due to connectivity with newly created fractures, leading induced earthquakes that may be felt by human or even cause damages in some cases.

To understand how the hydraulic fracturing influences natural fault slipping, it is important to investigate the stress change associated with events during hydraulic fracturing. In the Cotton Valley experiment, both hydraulically created fractures and pre-existing natural fractures are identified. Our source parameter analysis suggests that the two sets of fractures have different stress drops. The events along triggered natural fractures have similar stress drop levels to natural earthquakes, while events along created fractures have much lower stress drop that are at least one order of magnitude lower than natural earthquakes. Different types of source parameters can be used to effectively detect whether pre-existing fractures have been triggered. In the light of the experience in Cotton Valley experiment, we extend the analysis to microseismic dataset collected during a hydraulic fracturing experiment. Accurate event detection and location will be performed from borehole monitoring networks to the new dataset, source parameter and stress analysis will be performed to better understand stress changes during hydraulic fracturing. Comparison of two different datasets with different tectonic environments and different operation parameters would enable us to better understand similarities and differences of induced fault slip between different operations and along different types of fractures.

Presenting Author: Jiewen Zhang

Authors