A Practical Introduction to Seismic Inversion
A Practical Introduction to Seismic Inversion - training course
This practical course explains the principles and practice of inversion of seismic reflection data to yield a variety of volume properties and suggests how these results may be used. It illustrates potential benefits of seismic inversion but recognises the inherent non-uniqueness in the process and the various ways of handling both this and the information, low frequency especially, that is missing in the seismic data.
Suitability - Who should attend?
Geophysicists and geologists working in exploration, appraisal or development using quantitative methods to estimate rock properties. Though not highly mathematical, an understanding of basic mathematics and geophysics (seismic acquisition and processing) is required. Although some advanced geophysical techniques are discussed this should not deter people without an in-depth knowledge of geophysics from attending.
Outcome / Qualification etc.
Participants will learn to:1. Understand the potential advantages of using Seismic Inversion in Exploration and through Appraisal and Production stages of a field’s development.2. Differentiate the various methods of seismic inversion, understanding the assumptions and limitations underlying each type.3. Determine which method might be appropriate in given circumstances. Appreciate the relative cost in terms of time, effort and money.4. Understand how Seismic Inversion and Rock Physics are linked and how ﬂuid replacement analysis, porosity modelling and wedge based synthetics may be applied to assess the potential usefulness of inversion.5. Understand the convolutional model and that this is a useful simplification. Understand the nature of the embedded wavelet, especially phase and polarity aspects.6. Understand various types of inversion: run-sum and similar inversions, coloured inversions, sparse spike and model-based; post-stack and pre-stack; relative and absolute forms; stochastic and probabilistic inversion types.7. Appreciate that traditional deterministic inversions are non-unique.8. Understand the apparent resolution enhancing properties of some inversions and the interaction with non-uniqueness.9. Understand the critical requirements for seismic data quality and be able to assess whether any given seismic dataset is adequate for a proposed inversion study.10. Assess the quality of the logs that are used to calibrate the seismic data and understand that they may need conditioning if there are problems.11. Understand how the well-tie process works and how the wavelet “embedded” in the seismic data may be estimated. Understand the pitfalls that such estimations may encounter and how to avoid them.12. Appreciate the pros and cons of “DIY” (do it yourself) versus using a specialist service provider (contractor or in-house specialist team).13. Manage the planning and execution of a seismic inversion project, from feasibility study to interpretation.
Training Course Content
The course covers the principles behind seismic inversions of various types including: non-uniqueness in inversion; basic log QC and upscaling; depth to time conversion; seismic QC and conditioning; well-tie and zero-phasing issues; wavelet estimation; Acoustic Impedance Inversion; Elastic (pre-stack) inversion, including Elastic and Extended Elastic Impedance; specialist inversions. Stochastic and Probabilistic Seismic Inversion Methods are discussed. Finally, pitfalls in inversion and recommendations for robust work-flows and best practice will be addressed. Theory is related to practice through exercises and examples.
- Principles of standard inversion
Relationship with forward modelling, non-uniqueness. Seismic inversion as just one application of inversion principles. Single volume and multi-volume inversions. Use of inversion products including estimation of reservoir properties such as porosity, net/gross and saturation.
- Basic Log QC and Upscaling
Basics of P and S wave sonic, density, and other relevant logs and their limitations. Use of log transforms for QC and to replace missing data. Principles of fluid substitution and synthetic modelling for feasibility study. Importance of upscaling from log to seismic resolution.
- Seismic QC and Conditioning
Critical issues with the seismic data that is input to inversion, including bandwidth, relative amplitude fidelity, stability of the wavelet in depth/time and space. Requirements for careful acquisition and processing/reprocessing. Recent advances. How to recognise when inversion is not appropriate.
- Well Ties, Zero Phasing and Wavelet Estimation
The process of matching seismic to well data, including the recognition of reasons why they may not match. Methods of estimating the phase of the data and bringing the data to zero phase when needed. Methods of wavelet estimation including statistical and deterministic methods and error estimation. Analysis of results in terms of time shifts, phase shifts and amplitude scalars.
- Acoustic Impedance Inversion
The missing low (and high) frequency information and approaches to replacing this; relative vs Absolute Inversion. Sensitivity to phase and amplitude of the input data. Hierarchy of methods from trace integration and Coloured Inversion through model based and GLI methods. Validity (or otherwise) of typical seismic data used in the process.
- Multi-Offset Inversion
Inversion of non-zero-offset data for volume attributes including Poisson’s Ratio, Shear Impedance, Lambda-Rho and Mu-Rho. Different approaches including angle stack inversion, intercept-gradient inversion and ‘simultaneous inversion’. Advantages and disadvantages of each approach. Difficulties with inversion for density. Concepts of ‘Elastic Impedance’ and ‘Extended Elastic Impedance’ and relationship to rock properties. Fluid and Lithology volumes; EEI “tuning”.
- Extensions of Deterministic Inversions
Discussions of inversion of 4D seismic data and joint PP and PS inversion.
- Stochastic and Probabilistic Seismic Inversion
The problems of a) non-uniqueness, b) missing high frequency information and c) low frequency model building. Stochastic inversion as a tool to tackle these issues and provide valuable uncertainty estimates to augment the inversion results. Direct inversion for reservoir properties such as porosity, water saturation, net/gross etc, with uncertainty estimates using Probabilistic Seismic Inversion.
- Pitfalls and Best Practice
Practical examples of pitfalls if assumptions and/or data quality is not well understood. Non-unique nature of the process and ways to capture and characterise this. Suggestions for best practice.
- How to get the best out of an inversion project
Practical advice on how to manage a seismic inversion project, including: conducting and evaluating a feasibility study, managing the work using specialists and specialist software, quality control and interpretation of the results.
The cost of this training course is GBP 2572 per delegate.
Nautilus can also deliver this training course on an in-house basis, helping your staff achieve their professional development goals. With a customised, In-House Training solution, you can tailor the course content to individual company requirements by incorporating your data, your software, or specific case studies.
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