Geomechanical Injection Scenario Toolkit (GIST)

Geomechanical Injection Scenario Toolkit, or GIST, uses simplified pore pressure models to give a general understanding (i.e., the gist) of the evolution of subsurface pressures at areas of interest. Capabilities include modeling the relative contribution of saltwater disposal wells to pressure at a seismic event location (existing or hypothetical). GIST can also inform operational changes in response to, or to proactively prevent, seismicity.

GIST, like Fault Slip Potential (FSP), combines Theis' pore pressure solution for a uniform aquifer (1935) with Monte Carlo sampling of subsurface parameters. While no individual model produces a defensible result, the ensemble of models can aid decision making and information collection.

The GIST webtool uses an open-source (BSD 3-clause) Python library, available on the TexNet GitHub.com page. The repository also includes notebooks with examples and comparisons to known results.

ExxonMobil and TexNet released the GIST webtool in early 2025 on the TexNet Software Portal. Desktop computers or tablets are required because of the need to manipulate .csv files.

For software inquires, updates, and registration, join our mailing list: gist@utlists.utexas.edu

Disclaimer:

The results of GIST are entirely dependent upon the inputs provided, which may be incomplete or inaccurate.

There are other potentially plausible earthquake inducement scenarios that are not currently considered, including fluid migration into the basement, out-of-zone poroelastic stressing, or hydraulic fracturing.

None of the individual models produced by GIST accurately represent what happens in the subsurface and cannot be credibly used to accurately assign liability or
responsibility for seismicity.

"All models are wrong, but some are useful" - George Box, 1976

References:

Rapid Geomechanical Analysis of Injection-Related Earthquakes (IMAGE 2022)
GIST: An Open-Source Toolkit for Rapid Geomechanical Analysis of Injection-Related Earthquakes (ARMA Induced Seismicity Webinar, 2023)
The relation between the lowering of the Piezometric surface and the rate and duration of discharge of a well using ground-water storage (Transactions of the American Geophysical Union, 1935)