Assessing slip tendency of cryptic faults in southern Kansas with a new open source, extensible tool: Introducing pyFaultSlip

Abstract:

A significant obstacle that operators, stakeholders, and regulators face with safe injection of fluids for enhanced oil recovery, wastewater disposal, or CO2 storage is quantifying the risk of induced slip / seismicity. While there are several existing software packages to assess ‘slip tendency’, they do not fully meet our requirements to provide an assessment of induced slip hazard for a proposed CO2 repository in SW Kansas, and are not open source, so there is no ability to extend those software packages as a member of the scientific community. We have developed pyFaultSlip, an open source package written in python that can perform a 2D (e.g. lineaments or mapped fault traces) or 3D (mapped fault planes from 3D seismic) slip tendency analysis. Slip occurs during fluid injection when the effective normal stress on a fault is sufficiently reduced, causing the the ratio of shear stress to effective normal stress to exceed the coefficient of friction for that fault. We use a 3D stress representation imposed onto a planar fault geometry. Uncertainty in input / assumed parameters is propagated using a monte carlo approach and results are represented using the fluid pressure that correlates to a selected probabilistic cutoff. We will show several use cases for assessing slip hazard for areas with cryptic faults observed in 3D seismic data in southwestern Kansas, as well as potential slip hazards associated with lineaments documented from analysis of well tops data in southern Kansas. We hope this tool will provide a starting framework for future open source and community-based contributions to aid in the safe implementation of deep fluid injection.