Synthetic Seismic Volume Generation and Assisted History Matching
The CoViz 4D visualization environment is complemented and extended by an impressive array of 3D ⁄ 4D quantitative tools and functionality; a powerful example is the seismic history matching workflow accessed through the CoViz Sim2Seis and 4D Assisted History Matching modules.
The CoViz Sim2Seis workflow allows reservoir engineers and geophysicists access to powerful and flexible synthetic seismic volume creation tools from directly within the data fusion framework. This integrated workflow delivers rapid, more easily interpreted results, resulting in better, faster seismic history matching, 4D seismic feasibility studies, and geomechanical screening.
Quantitative comparison of a seismic inversion (Elastic Impedance) to a calculated Synthetic Impedance volume of the same extents. The input PEM cell model is also shown. The cross plot displays the observed and synthetic seismic extraction values on a horizon approximately at the top of the PEM cellular grid. Data used with permission of owner.
The Sim2Seis Workflow
The CoViz Sim2Seis workflow integrates several powerful quantitative tools to deliver seamless seismic assisted history matching for 4D seismic assets. The fundamental goal is to deliver reservoir simulation results which better represent the past, and future, of the reservoir flow state; this is done through integration of 4D seismic observations.
The dynamic reservoir model is taken through a fluid substitution and petroelastic modeling procedure to generate the best possible synthetic seismic volumes across the reservoir. These synthetic volumes are then qualitatively and quantitatively compared to the observed 4D seismic in the 4D Assisted History Matching (AHM) module. The output of that process is then fed to reservoir simulators to inform an improved history match.
Schematic illustrating how the CoViz Sim2Seis workflow, tightly coupled with qualitative and quantitative analysis in the CoViz 4D Viewer, offers full seismic history-matching capabilities.
Sim2Pem: Simulation to Petroelastic Model
The Sim2Pem module within the CoViz Sim2Seis workflow quickly and easily guides the user from flow ⁄ saturation model to petroelastic (velocity and density) model. Some of the available options include:
- Cellular model import from a variety of simulators ⁄ sources
- Creation of petroelastic models from rock physics parameters via Gassmann substitution
- Krief or polynomial options for expression of dry moduli
- Various options for rock moduli stress sensitivity
- Optional accommodation of time-varying porosity
- Optional Extended Elastic Impedance calculation
- Batzle-Wang or user-provided custom fluid calculations
- Up to 25 different lithology regions
- Tools and options for rapid interactive QC and scanning of the output attributes
Pem2Seis: Petroelastic Model to Synthetic Seismic
The creation of 4D synthetic seismic volumes from a petroelastic model (Pem2Seis) is the next step in the CoViz Sim2Seis workflow. Focused around an intuitive and easy-to-use graphical interface, the Pem2Seis module offers a wide variety of options for synthetic-seismic volume creation:
- Integrated Depth-to-Time and Time-to-Depth conversions
- Option for band-limited impedance or reflectivity volumes
- P-S mode conversion options
- Reservoir velocity change induced timing shifts
- Multiple options for modeling background shale properties: constants, trends, 2D & 3D grids, well data
- 4D difference volume outputs
- SEG-Y and other export options
- Multiple intermediate output options for QC
- Easily scripted/batched workflows for rapid looping, and sensitivity analysis
4D Assisted History Matching
Including 4D seismic when updating a reservoir simulation model to achieve a better history match results in a better constrained model and a greater understanding of its inherent uncertainty. The CoViz 4D Assisted History Matching (4D AHM) module simplifies the history matching workflow by computing seismic Match Quality information through generation and execution of a script for input to an external (non-CoViz) program containing the appropriate history matching algorithms.
Schematic of the 4D Assisted History Matching workflow in CoViz 4D (based on Figure 2 from Hodgson et al., Generating Value from 4D Through Efficient Integration: The Leading Edge, May 2017).
Match Quality (MQ) is calculated as a misfit ratio within a certain area of interest (polygon) from a composite attribute map produced by the AHM workflow. Three calculation options are available depending on the specific field and model being matched: MQArea, MQFeature/Sweep, and MQFeature/dEEI. The principal differences are in the physical assumptions made, required interpretation input, and the physical property being matched. The following anomaly types can be determined:
AVG = average of all amplitudes
SSA = sum of signed amplitudes
SNA = sum of negative amplitudes
SPA = sum of positive amplitudes
LNV = largest negative values
LPV = largest positive values
The 4D AHM Feature workflow reduces the reservoir physics and its simulation to a simple binary representation to show where the 4D seismic response and simulation model agree or disagree with each other; where there is 4D signal, green areas indicate a match and blue areas indicate a mismatch.
Quantitative Visualization and Seismic History Matches
Once the synthetic seismic volumes are created, the next step in the Sim2Seis workflow is the qualitative and quantitative comparison of the synthetic volumes with the field-measured (or inverted) seismic, and the reservoir simulation input. The CoViz 4D software includes built-in tools for rapid, integrated, quantitative analysis and statistical comparison of geometrically diverse, yet spatially overlapping 3D and 4D datasets. As the comparisons are made, information can be sent back to the reservoir simulation for adaptations and improvements in the seismic history match.
Some of the many quantitative analysis features include:
- Time-step arithmetic operations (rapid calculations of differences over time)
- Interactive tools for computing property sums and averages in seismic and cellular space
- Back-interpolation of properties between spatially and temporally overlapping data
- Statistical analysis, including histograms, probability plots, and cross-plotting of diverse data types
- Powerful interactive links between multiple statistical plots and the 3D ⁄ 4D viewing space
- On-the-fly volumetric calculations
- Integrated calculator for arithmetic operations on any quantitative CoViz 4D object
- Multiple output options to capture and export the results of the quantitative analysis
- All operations can be captured in code for automated operations and rigorous sensitivity analysis
4D seismic data sampled into cellular and well log space. Rapid and easy access to 4D functions is essential for comprehensive quantitative visualization.
CoViz 4D 13.0
offers vastly expanded support for DGI multigrid files; On-the-fly arithmetic in reservoir simulation time-series plots; New options for effective stress treatment in Sim2Pem; Cloud-native data loading support for select file types; Extensive new features and performance around LiDAR data.
ARTICLES & PAPERS
Hesham Ebaid, Kanglin Wang, Marcelo Seixas, Gautam Kumar, Graham Brew and Tracy Mashiotta examine enhanced workflows and solutions for optimizing the utility of Permanent Reservoir Monitoring data in a deepwater setting.
Graham Brew, Dynamic Graphics, Inc., USA, and Jane Wheelwright, Dynamic Graphics, Ltd, UK, discuss the integration of 4D seismic data into the reservoir management workflow.
A solution that offers a dynamic, temporal visualization environment for data fusion and integrated reservoir surveillance.
Dynamic Graphics has developed a tool which can visualize multiple datasets from an oil field simultaneously in 3D and 4D—from an overall view of the basin to a view of the individual wells and reservoirs—and you can see how it changed over time as well.