Improving the quality of Velocity Models and Seismic Images. Alice Chanvin-Laaouissi

Velocity Volumes Challenges 1. Define sealed 3D framework for velocity interpolation 2. Perform geologically constrained velocity models 3. Update velocity models 2

How to define a sealed 3D framework for velocity modeling? By construction SKUA models are built in 3D volumes SKUA models = Sealed models Perfect data carrier for velocity modeling studies 3D framework automatically built with structural model no time loss UVT transform Geologically constrained velocity model 3

Creation of geologically constrained velocity models SKUA can model any structural and stratigraphic complexities Framework for velocity modeling is a perfect representation of the geological reality hence reduces uncertainties on time/depth conversion SKUA model in extensive environment, complex fault network SKUA model in compressive environment SKUA Model around intrusive structure SKUA model built around a Salt structure and related velocity model - perfect framework for velocity modeling 4

Creation of geologically constrained velocity models Simple to advanced interpolation of velocity: Multiple data input: Stacking velocities, checkshot, sonic, well markers Multiple geostatistical methods (from simple interpolation to kriging with external drift), allowing noise removal SKUA Geological grid = ideal support for geostatistics computation (no cell distorsion) Improved model accuracy by combining different velocity data sources and by using appropriate methods for velocity interpolation along stratigraphy SKUA grid built around a Salt structure and related geologically constrained velocity model Velocity inputs can be interpolated within the SKUA model using various geostatistics methods

Example of Velocity model creation from Sonic Logs Import Sonic as well log Display and QC Sonic in Log display On Wells defined velocity log derived from Sonic On Geologic grid use kriging with external drift (hard data= velocity logs) and drift property derived from Depth Conversion law Sonic displayed in Well section Variogram analysis on residuals SKUA model in extensive environment, filled with Sonic derived velocity Velocity law V=f(TWT) derived from Sonic

Property model editor to fully take advantage of the SKUA model Various methods available to interpolate velocity on sealed SKUA model Ability to combine multiple velocity inputs and use multiple velocity methods for advanced velocity modeling Easily create multiple velocity models within the same study for better understanding of structural uncertainty Geologically constrained Vint transferred from SKUA model to seismic cube. Co-rendering of seismic amplitude and Vint. Methods: Constant Linear function Exponential function User defined equations Linear Function of Property Interpolated Property From Grid Property From Surface of Layer Boundary Property 7

Goal Use the SKUA structural and stratigraphic model building capabilities in the depth imaging workflow. In particular important in geological regimes defined by faults, salt bodies, unconformities, etc. Background velocity model creation Depth imaging Depth Interpretation Model-building in SKUA (for complex models) Tomography updates/well tie updates 9

Paradigm 15: Current Status Horizon and fault picking (3D Canvas)* Epos-link SKUA model creation Grid-based tomography workflow Illumination studies Epos-link Volumes creations (Dip, Az, Formation, Velocity) Tsurfaces (Horizons and Faults) Improvements for grid based tomography and illumination. *Automatic picking of horizon (stratigraphic) patches can be performed to better constrain SKUA Model internal stratigraphic layering style 10

Support for Volumes In GeoDepth, seamlessly support Attribute Volumes created from SKUA models [epos-link]: Velocity Geological formation Dip, Azimuth Volumes exported in 32bit float format No NDVs to match Geodepth requirements 11

Dip and Azimuth Volumes New in P15 Dip and Azimuth Cube: Voxet > Compute > SKUA Model Curvature Varying Dip values within conformable stratigraphic layers 12

Dip and Azimuth Volumes New in P15 Example with erosions Varying Dip values within eroded stratigraphic layers 13

Stratigraphic patch extraction Additional automatic picking of horizon (stratigraphic) patches can be performed to better constrain internal stratigraphic layering style of the SKUA model Structural Model Building QC, interpretation and modeling validation Paleospace Computation Seed Generation Patch Propagation Geological Time Computation Geological Grid Building

Usage of Formation Volume Tomography - Build Matrix, Interactive Ray Tracing Ray filtering by formations relevant for models containing salt bodies. 16

Usage of Formation Volume Grid Tomography- Solve Matrix: Final interpolation according to formation volume: Updated volumes better honor the structure. Update limits per formation. Update constraints per formation. Smoothing and sensitivity factors per formation. 17

Grid Tomography Interpolation Example Without Formation Volume With Formation Volume 18

An example of Salt Model Building Workflow Migration with Sediment Velocity Tomography Update for Sediments Migration and Pick Top of Salt Create Model with Salt flooding + Vel Modeling Grid Tomography With formation volume for filtering rays through salt body Migration and pick bottom of salt Build SKUA MODEL with Salt Grid Tomography using formation volume with no update of salt region 19

Inserting Salt Velocity Initial interpretation Related SKUA model and formation volume Pick top of salt Build salt surface with vertical flanks Sediment VINT Updated VINT Use background velocity model for sediment layers (Sediment VINT) Add Salt velocity with property model editor Create new SKUA model including Salt 20

Velocity model update with salt Per layer velocity model update 21

Advantages Geologically derived Dip/Azimuth volumes Geological formation volume can guide and control the Tomography updates for complex models. Faults and other discontinuities are honored properly in the velocity model to avoid imaging artifacts. Illumination workflow with complex models. 23

SKUA Model update from Tomography SKUA model update from vertical displacement in pencils

SKUA-GeoDepth Integration Plan P15: SKUA Volumes Enhances: Grid-Based Tomography Illumination RTM Modeling P15.5: SKUA Pencils Enhances: Model-Based Tomography workflow P16: Stratigraphic Column P16.5: SKUA Geological (coarse) grid for Tomography 26

SKUA-GeoDepth Integration Plan P15.5/P16 P15.5: SKUA Pencils Enhances: Model-Based Tomography workflow Benefits for the user: Pencils can be generated directly in SKUA from SKUA model (P15.5) Model-based Tomography provides updates that fully honors the structure. Use the depth updates to update a SKUA model - Sealed model remain sealed after Tomo iteration 27

Paradigm 15.5: Model-based Tomography Workflow Time Gathers Initial Interval Velocity Prestack Depth Migration Depth Gathers Depth Volume FastVel /Velocity Navigator AutoPicker Pencil Database Run Tomography Depth Interpretation Build Model in SKUA Updated Interval Velocity Rebuild Model from Displacements in Pencils (P16) Extract Pencils 28