NR holds GIG, a development group with the leading exploration companies operating on the Norwegian shelf.
The R&D consortium Geophysical Inversion to Geology (GIG) develops algorithms that invert seismic data and calculates the probability that the subsoil consists of various rocks such as sand, shale and clay filled with water, oil or gas.
Benefits and benefits to the sponsors
- Access to reports, publications and developed methods since the project started in 2016
- User support and training in the methods being developed
- Help with special challenges related to inversion studies
- Influence activities and focus areas in the project
- Attend regular status meetings
- Attend 1/2-year-old meetings where budgets and work plans are voted on
- Access to the PCube application
- Continuous access to new methods that are being developed
- Bug fix
The research and development in GIG is focused on the following areas:
- Better and faster algorithms, especially considering alternative approximations that can increase performance without compromising performance
- Tools for assessing the robustness of the inversion result and the geological prior model
- 4D seismic inversion by simultaneous inversion of several 3D seismic data sets
- Include lateral links in the inversion process to better take into account lateral correlations in geology
- More information from the inversion such as probability distributions of layer thicknesses, adjusted horizons with uncertainty and internal layering
- More flexible and correct definition of the geological prior model
NR can conduct independent inversion studies with the PCube application independently of GIG. These have often been carried out in close collaboration with the client and in such a way that they can continue the work on their own after the project is completed. Some of the examples below are taken from these studies.
The development work in GIG is implemented in a separate software application PCube. The application runs on Windows PCs in a separate graphical user interface or from Linux in a command line interface. The participants in the project have access to the PCube application and several of the sponsors use it in their daily work with seismic inversion. New methods and improvements in the PCube and PCube + algorithms, including PCube + 4D, are first developed and tested in the PCube application.
The PCube + algorithm is also commercially available in the PSPro program provided by Sharp Reflections. Through a collaboration with GIG, Sharp Reflections has access to the source code of the algorithm.
Several tools and methods are only available in the PCube application. In particular, this applies to tools for assessing the quality and robustness of the seismic inversion.
The algorithms are based on Bayesian seismic inversion for quantitative interpretation of seismic data. GIG further develops and improves the algorithms known as PCube and PCube +. The algorithms GIG develops use seismic data, elastic properties of rocks and a mathematical model of the subsoil where properties of the rock in a small point only depend on properties in neighboring points (Markov model).
The data are analyzed using Bayesian statistics that update the mathematical model of the subsurface so that it fits better with the seismic data. The updated model calculates the probability of the rocks at any point. In addition, it can calculate the depth of different depositional environments (horizons) and layer thicknesses (isochrons) of the rocks with an uncertainty. The methods can also be combined with rock models to calculate properties such as porosity, clay content and liquid saturation.