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82nd EAGE Annual Conference & Exhibition - Workshop Programme
- Conference date: October 18-21, 2021
- Location: Amsterdam, Netherlands / Online
- Published: 18 October 2021
21 - 40 of 45 results
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A New Role for Adaptive Filters in Marchenko Equation-Based Methods for the Attenuation of Internal Multiples
By M. StaringSummaryWe have seen many developments in Marchenko equation-based methods for internal multiple attenuation in the past years. Starting from a wave-equation based method that required a smooth velocity model, there are now Marchenko equation-based methods that do not require any model information or user-input. In principle, these methods accurately predict internal multiples. Therefore, the role of the adaptive filter has changed for these methods. Rather than needing an aggressive adaptive filter to compensate for inaccurate internal multiple predictions, only a conservative adaptive filter is needed to compensate for minor amplitude and/or phase errors in the internal multiple predictions caused by imperfect acquisition and preprocessing of the input data. We demonstate that a conservative adaptive filter can be used to improve the attenuation of internal multiples when applying a Marchenko multiple elimination (MME) method to a 2D line of streamer data. In addition, we suggest that an adaptive filter can be used as a feedback mechanism to improve the preprocessing of the input data.
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General Overview of Advanced Internal Multiple Attenuation Prediction Methods and Workflows
Authors F. Xavier de Melo and C. KostovSummaryThis work takes a close look at practical aspects when performing a complete internal multiple attenuation workflows. Along with advanced methodologies constantly adopted to improve the internal multiple prediction outcome, bridging the gap between the recorded multiple within the adaptive subtraction stage of the workflow requires understanding of the processing goals, the requirements of later processing stages, careful and meticulous quality assurance criteria and finally extensive parameter testing. Depending on the subsurface complexity and field maturity, different techniques and workflows are being applied to maximize the attenuation internal multiples while preserving underlying primary reflections.
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Multiples: Towards a Toolbox Perspective on Assumptions, Challenges and Options (an Invited Presentation)
Authors F. Xavier de Melo, J. Wu and F. Xavier de MeloSummaryIn this work we will touch on the fact that all seismic methods have assumptions and prerequisites. Understanding these assumptions is an important step to: (1) help understand what is needed to make a processing method effective, (2) define the role the seismic processing method could play in the seismic processing toolbox, when it would be the appropriate and indicated choice, and when to seek another option and (3) help understand what is behind the breakdown and failure of the algorithm. Embracing that all internal multiple prediction methods (attenuation and elimination) have advantages and limitations according to external environmental factors and physical assumptions, we encourage collaborative research whose goal would be to understand under what circumstances the Marchenko approaches and ISS methods might be the indicated and appropriate toolbox choice for removing multiples.
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Structural characterization and Diagenetic Study of Mineralized Fractures in Paleo-Geothermal Systems – the Geneva Basin
Authors M. Perret, M. Gasparrini, S. Omodeo-Salé, L. Guglielmetti, A. Moscariello and V. TelesSummaryGeothermal exploration in low- to medium-enthalpy settings, such as sedimentary basins, is gaining increasing interest worldwide. This local source of heat and/or electricity appears as a durable and sustainable energy source. The present project aims to reduce uncertainties and risks linked to the occurrence of cementation in potential geothermal reservoirs and to reconstruct paleo-fluid circulation conditions.
A multidisciplinary approach combining the study of paleo-geothermal systems and the active present ones is used in the Geneva Basin (Switzerland and France). The workflow consists in : 1) a characterization of the structural framework of faults and fractures in an exhumed fossil geothermal system (Mont Vuache); 2) a petrographic study of the diagenesis of fractures (cementation, dissolutions) to infer the origin of paleo-fluids (timing, temperature, pressure, composition) and their circulation conditions in natural conduits of the fractured reservoirs; 3) fluid-rock interaction simulations to verify the thermodynamic validity of conceptual models related to diagenetic processes at the origin of cements, and to evaluate the volumes and spatial distribution of cementation.
This paper focuses on mineralized fractures (veins) sampled in cores at depths between 300 and 3050 metres, as well as in outcrops in the Mont Vuache, South-Western area of the Geneva Basin.
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A Modular Wavefield Inversion Process, Including Internal Multiples, Transmission and Converted Waves
Authors E. Verschuur and L. HoogerbruggeSummaryOver the last two decades the full waveform inversion (FWI) method has established itself as one of the main methods for seismic velocity model estimation. However, due to its computational expenses its full 3D application is limited to the lower frequency range, especially with the extension to the elastic situation in mind. Therefore, we need additional full waveform tools for velocity updating that is more geared towards broadband reflection data, e.g. via reflection waveform inversion. The nice feature of migration-based methods is that the sampling requirements are only dictated by the Nyquist sampling criterion. Extending the reflection tomography to include converted waves can in principle be done at the same spatial sampling as the PP reflection inversion, especially in a marine environment. The proposed full wavefield migration and joint migration inversion methodology is based on the building blocks of one-way propagation and reflection/transmission at both sides of a discontinuity. This method can be used to effectively estimate velocity model and images without multiples cross-talk imprint. Furthermore, this approach can also be naturally extended to include converted waves, with the ability to reduce converted wave cross-talk and actually use it to estimate a consistent P/S reflection image and P/S-wave velocity models.
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Enhancing Internal Multiple Prediction by Using the Inverse Scattering Series
Authors J. Wu, Z. James Wu, F. Xavier de Melo, C. Lapilli and C. KostovSummaryWe report several factors to enhance the application of the inverse scattering series method for internal multiple prediction to field data. Firstly, there are challenges related to data conditioning in the inverse scattering series method. In addition to other data conditioning steps, we introduce an efficient data regularization strategy by applying nearest neighbor search and differential move out to accommodate various acquisition situations. Secondly, improving the model’s quality is always preferable and significant. The strategy includes correctly incorporating the 3D source effect and obliquity factor to enhance amplitude fidelity in terms frequency spectrum and angle information. Thirdly, the cost is another challenge for the method. We apply the angle constraints over the dip and opening angles to reduce the computational cost without compromising the model’s quality, and propose an automatic solution for parameterization. Fourthly, the segmented prediction by limiting the range of the multiple’s generator can benefit the subsequent adaptive subtraction. We will illustrate all these points with a field-data example in the presentation.
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Marchenko Multiple Elimination
More LessSummaryMarchenko methods compute a focusing function for a receiver at the acquisition surface and a virtual source in the subsurface. Computing the focusing function requires subsurface information. The method has been modified to operate at the acquisition surface. The focusing function becomes a fundamental wave field as known since many decades. These can be computed from the up- and down-going parts of the data without any subsurface information. The up- and down-going parts can be obtained from up-down decomposition, or from up-down decomposition of the data followed by free surface multiple removal and wavelet deconvolution. The primary reflection dataset is obtained from applying the fundamental wave field to the data, or directly from the up-going part of the fundamental wave field. In the first option, the obtained primary reflections are the same as in the data, with all transmission effects and possibly the source ghost and source wavelet. In the second option, the obtained dataset is a primary reflection impulse response where the amplitudes have been compensated for transmission effects.
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Internal Multiple Attenuation: Using the Low Frequencies to Protect the Primaries
Authors P. Hugonnet, F. Haouam, L. Vivin, T. Rebert, A. Pica, S. Leroy and A. El EmamSummaryHorizontally layered geological media are challenging for the modeling and subtraction of multiples. As both the primaries and the multiples are flat, it is very difficult to adaptively subtract a model of multiples while preserving the primaries. A model of primaries, if available, can be used together with the multiple model to perform a simultaneous adaptive subtraction and to protect the primaries. We propose herein a method to build primary models by considering that in some geological contexts characterized by fine layering, the internal multiples are virtually absent from the lowest frequency part of the data; therefore, a blind deconvolution algorithm is used to restore a full band from this low frequency part. The validity of this approach is demonstrated on onshore field data from Kuwait.
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Using Dempster-Shafer Theory to Model Uncertainty in Petrophysical Interpretation
By F.M. MiottiSummaryThe analysis of the uncertainty is a key element of the reservoir characterization because it provides effective support in ranking potential plays and contributes to reduce the risk of unproductive drilling. Various approaches are detailed in the technical literature: some studies addressed the uncertainty of petrophysical parameters through joint inversion of geophysical attributes ( Miotti et al. 2018 ) while other methodologies exploited the stochastic framework to model the uncertainty of reservoir parameters, ( Bachrach 2006 ). This study leverages the Evidence Theory or Dempster Shafer (DS) theory ( Helton 2009 ) to rank the potential reservoir zones through evidential intervals. The presented workflow shows how the log measurements can be combined together through the DS theory to identify and rank the reservoir play in the well. The procedure is tested on a well log dataset to assess the robustness of the methodology. The workflow outcomes are then validated through a comparison with the benchmark petrophysical interpretation.
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CSEM Search for Geothermal Water for Combined Heat and Power
Authors A. Ziolkowski and P. StoffaSummaryGeothermal energy is under-used in the energy strategies of many countries. Groundwater is the obvious means to move heat from depth to the surface for use in combined heat and power plants. If the water temperature at depth (normally > 3 km) is greater than 100 °C, it vaporises at atmospheric pressure, releasing 2,260 kJ/kg. This is a huge resource. The problem is to locate hot water in subsurface reservoir rocks before drilling. We present a new approach to find hot subsurface groundwater using controlled-source electromagnetics (CSEM). EM propagation in conducting media satisfies the diffusion equation, not the wave equation. There are no identifiable arrivals associated with travel paths defined by ray theory and there is no theory to enable the diffusive responses from different source-receiver pairs to be combined to increase signal-to-noise (S/N) ratio. We propose that the time-domain impulse responses obtained from broad bandwidth CSEM data be transformed into equivalent waves, which may then be processed using seismic methods to increase S/N and yield high-resolution 3D images of conducting bodies down to 4 km depth. Using the analytic response of an impulsive current dipole source in a full space, we show that the required transformation is feasible.
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GPOS Evaluation for Geothermal Projects in the Netherlands
More LessSummaryEvery subsurface project has the risk of failure or disappointment if the predictions made by the subsurface evaluation team are incorrect. In some cases the reality is so much different from the expected that no production is possible or allowed. This is well known for hydrocarbon wells, but also in geothermal projects prediction errors are possible that could result in a total write off of the well or the project. To cater for these risks a fit-for-purpose GPOS evaluation scheme for geothermal projects has been developed within EBN. A consistent GPOS evaluation will help EBN to determine the correct usage of funds in its mission to explore for and accelerate the use of geothermal energy in the Netherlands. Five subsurface aspects are seen as the main parameters determining the technical success of a geothermal project in the Netherlands: Aquifer, Permeability, Fluid Compatibility, Temperature and Connectivity.
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Acoustic FWI for Salt and Sub-Salt Update from Simple Initial Models
Authors C. Wang, P. Farmer, C. Calderon, I. Jones and J. BrittanSummaryWe will show our newest FWI technology that allows us to start from simple velocity model and push acoustic FWI as far as we can for salt and sub-salt update.
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Visualisation of Uncertainty in Voxel Models of the Shallow Subsurface of the Netherlands
Authors J. Stafleu, D. Maljers and J. GunninkSummaryTNO – Geological Survey of the Netherlands builds and maintains a national 3D voxel model of the shallow subsurface. Each voxel contains the following properties: (1) the stratigraphical unit the voxel belongs to; (2) the lithological class that is representative for the voxel; and (3) a set of probabilities of occurrence for each of the lithological classes that may be present in the voxel.
The probabilities of occurrence provide us with a measure of model uncertainty. The probabilities of an individual voxel can be displayed in a bar graph. Similar displays are possible in visualizations of virtual boreholes. However in 2D and 3D visualizations it is no longer possible to show all probabilities in a single view: the user will always be presented with one probability at a time.
To solve this problem, Wellmann and Regenauer-Lieb (2012) proposed to use information entropy as a measure of uncertainty in 3D models. The information entropy of a voxel is a single value ranging from 0 to 1 that can easily be calculated from each of the probabilities of lithological class. Based on this concept, we added two measures of uncertainty to the model: one for lithological class and one for stratigraphical unit.
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Uncertainty of the Geological Framework Model of the Netherlands
Authors W. Dabekaussen and H.J. HummelmanSummaryTNO – Geological Survey of the Netherlands builds and maintains models of the shallow subsurface of the Netherlands, up to a depth of about 500 m below mean sea level. Various property models, for instance populated with lithological or hydrological parameters, rely on a national stratigraphic framework model to constrain interpolation of borehole information. With increasing interest in the uncertainty of subsurface models, there is a need for accurate quantification of the uncertainty of the stratigraphic framework model. This is not an easy task, as geological modelling tends to rely heavily on expert geological knowledge to help interpolation of structures from sparse borehole information. It is shown that a mixed approach using cross-validation and kriging variance can be used to accurately estimate model uncertainty of the stratigraphic framework model. The next challenge will be how to visualize this uncertainty and to quantify how the uncertainty of the stratigraphic framework model will propagate into that of derived property models.
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What Can the High-resolution Velocities from Full-Waveform Inversion Offer for Seismic Interpretation?
Authors J. Mann-Kalil, G. Duval and A. RatcliffeSummaryWe present a wide range of full-waveform inversion (FWI) velocity model build case studies from around the world, but highlight these from an interpreter’s point of view and show how the accuracy and resolution in the FWI velocity field can be used to de-reisk and enhance the geological interpretation. Additionally, we highlight that increases in compute power and algorithm efficiency allow FWI to be regularly run on large, basin-scale areas, and also that recent advances in FWI technology are allowing deeper updates, and ever more accurate velocity models, to be obtained.
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Play-Based Exploration and Development Plan for Geothermal Energy in the Netherlands
Authors F. Vinci, J. De Jager, J. Schellekens and C. LeoSummaryThe presented ‘Play-based Exploration and Development Plan for Geothermal Energy in the Netherlands’ provides an up-to-date overview of how and where geothermal heat can be developed safely, responsibly, sustainably and cost effectively.
To reach this goal, a play-based portfolio approach was adopted, allowing to extract best value from available information and to guide further exploration steps. Using current knowledge, Common Risk Segment (CRS) maps of the six main aquifers of the Dutch subsurface were generated. However, since the deployment of geothermal heat is not only influenced by subsurface geology, but also by local heat demand and presence of heat networks, CRS maps were integrated with this type of surface data. As a result, the presented Exploration and Development Plan brings together in one map subsurface knowledge, heat networks and heat demand, opening to a new world for understanding, steering, planning and budgeting for long term geothermal development.
This makes it a valuable source of information not only for geoscientists, but for also for regional governments, civil society organizations and commercial operators that have to make choices between the development of geothermal heat or applying other renewable sources.
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Modelling of mineralisation in Geothermal Projects: a Stirred tank Approach
Authors A. Hussain, N. Khoshnevis, B. Meulenbroek, H. Bruining, A. Reerink and K. WolfSummaryMineralisation in geothermal projects is an important issue. The precipitate ensuing from mineralisation within the doublet restricts the flow path of the water. Consequently, more energy is wasted on the process. Thus, mineralisation in a geothermal reservoir may result in additional costs and thereby reduces the project’s economic return.
But, modelling precipitation and dissolution over the complete doublet in a connected manner can be challenging when attempting to account for all physical and chemical processes. This involves among others the mineralisation reactions coupled to the heat and mass transport equations in surface facilities and porous media.
Here we model the mineralisation in a volume of produced water as a function of time, accounting for the decrease in pressure and temperature, and model the reactions based on a kinetically controlled approach. PHREEQC allows us to model the amount and composition of the mineralization over time. We find that precipitate formed in the heat-exchanger consists mainly of Pyrolusite, Barite and Calcite. Barite, Chalcedony and Quartz are the main minerals to be formed downstream of the heat-exchanger, but upstream of the reservoir.
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Elastic Versus Acoustic Asymptotic Extended Born Inversion for Marine Acquisition Surveys
Authors M. Farshad and H. ChaurisSummaryWave-equation based asymptotic Born inversion was originally developed for pure acoustic media. Recently, the applicability of approximate Born inversion has been extended to variable-density acoustic and elastic media, all assuming marine towed-streamer data. Even if only pressure waves propagate in the water layer, we study the impact of elastic effects: we compare the elastic and acoustic imaging results based on the asymptotic pseudo-inverse Born operator. We conduct two numerical experiments, for a simple layered model and part of the 2004 BP salt model. Numerical results illustrate the superiority of the elastic inversion compared to the acoustic version, especially due to converted waves around the salt interface.
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