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Obsidian

Obsidian is a set of tools designed to perform probabilistic inference with geophysical sensor data to produce models of the sub-surface. It is written primarily in C++ and runs on GNU/Linux and Unix operating systems.

Description

The software is designed to perform geophysical inversions in regions relevant to the geothermal industry: specifically sedimentary basins overlying a basement into which granites may or may not be intruding. This flexibility allows us to model both Enhanced Geothermal Systems (EGS) such as the Cooper Basin, and (Hot Sedimentary Acquifier) HSA systems such as the Otway basin.

Probabilistic inversions are generally computationally expensive, but Obsidian can parallelise the workload over a cluster by delegating expensive sensor simulations to workers to significantly improve performance. Obsidian has been successfully used to perform large scale inversions on cluster architectures such as Amazon EC2.

Contact Us

Please feel free to contact the developers at NICTA if you have questions about building, running or interpreting results from Obsidian. Best to email Lachlan McCalman ([email protected]).

This fork of the repository also contains configuration and sensor data files for recent geophysical inversion papers written using Obsidian (see "Literature" below). These configurations are meant to be self-contained and can be run to reproduce the plots and behavior in the papers in which they appear. For more information, email Richard Scalzo ([email protected]) or David Kohn ([email protected]).

System Support

Currently, Obsidian runs on Linux-based operating systems only.

Compiler Support

Obsidian successfully compiles under GCC 4.9.

Prerequisites

Obsidian requires the following libraries as prerequisites:

  • Boost 1.55
  • Eigen 3.2.0
  • google-log (glog) 0.3.3
  • google-test (gtest) 1.7.0
  • zeromq 4.0.3
  • cppzeromq 2358037407 (commit hash)
  • Protocol-buffers (protobuf) 2.5.0
  • leveldb 1.15.0

Please note that the actual source of google-test is required, so don't attempt to use a pre-compiled version from a package manager. Obsidian compiles libraries from google-test as part of the build process. The prereqs folder contains some instructions for building each of the above libraries from source code. There is also a script for downloading and building prerequisites in the prereqs folder.

Building

There is a build.sh script included with Obsidian in that can be used to easily build the project using CMake, by specifying environment variables corresponding to the locations of the prerequisite libraries. If you have installed them all into /usr/local, you can probably ignore them and just run CMake. Once you have run CMake in your build directory, a simple make command will suffice to build the project.

Documentation

There is doxygen documentaion available here. To compile the documentation locally, just run make doc

Literature

  • Original Obsidian methods paper: McCalman et al. 2014, "Distributed Bayesian Geophysical Inversions." Proceedings of the Thirty-Ninth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 24-26, 2014.
  • Original application to the Moomba gas field: Beardsmore et al. 2016 "A Bayesian inference tool for geophysical joint inversions." ASEG Extended Abstracts, 2016, 1–10, 2016.
  • Model development paper exploring sampler behavior, prior + likelihood sensitivity: Scalzo et al. 2018, "Efficiency and robustness in Monte Carlo sampling of 3-D geophysical inversions with Obsidian v0.1.2: Setting up for success." Submitted to Geoscientific Model Development, arXiv link pending. Configurations to reproduce runs found in examples/scalzo18 subdirectory.

Current Limitations

  • The ground surface is currently assumed to be flat.
  • Only a very basic visulation script is included.
  • Rock properties are assumed to be multivariate Gaussians.

Licence

Obsidian is released under the GNU Affero General Public License Version 3 or later. Please see COPYRIGHT.

Obsidian incorporates a modifed version of cnpy, which is copyright (c) Carl Rogers, 2011 and distributed under the MIT license. The modified copy of cnpy can be found along with the license in the src/io directory.

Bug Reports

If you find a bug, please open an issue.

Contributing

Contributions and comments are welcome. Please read our style guide before submitting a pull request.