The above image in CoViz 4D depicts a seismic horizon and velocity model in the time domain (top) and the same horizon, depth converted, along with the depth converted seismic cube, wellbores and horizon picks in the depth domain (bottom).
Reservoir engineers have the benefit of ever-greater volumes and varieties of reservoir data available to drive development and operational decisions. Yet, utilizing these data sources to provide a more detailed and accurate model of subsurface conditions remains one of the biggest industry challenges. Fortunately, a software solution, CoViz 4D from Dynamic Graphics, Inc., is helping reservoir engineers address these challenges and obtain greater value from reservoir data to reduce subsurface uncertainties.
In this blog, we explain how the integration of a wide range of subsurface data
, quantitative analytic tools, and the ability to visualize data in a collaborative 3D environment
are helping reservoir teams reduce subsurface uncertainty and are supporting well-informed reservoir development and operational decisions.
Better Velocity Modeling Reduces Seismic Uncertainty
Depth uncertainty can result in costly mistakes associated with well planning and drilling. Miscalculation of a target depth can result in significant cost overruns tied to rig time, drill pipe expenses, and bottom hole assembly damages when actual stratigraphy and targets don’t coincide with drilling plans.
CoViz 4D helps reduce subsurface uncertainty by offering a unique velocity modelling workflow
to transform seismic data into the depth domain by minimizing the depth residual at the wells. To build these 3D structural models CoViz 4D uses a series of 3D time horizons as inputs.
Depth uncertainty can be seen in the CoViz 4D image above to be increasing away from well control. The actual depth uncertainty value can be imported as a wellpath attribute and displayed as a lathe plot where the radius represents the value of depth uncertainty.
The velocity model begins by calculating a scalar value from well pick residuals. This approach reduces depth uncertainty by then applying the scalar value, layer by layer, to the interval velocity to produce a corrected velocity model. The process corrects the first layer by applying the scalar correction to the instantaneous velocity of the layer above, then repeats the calculation for the remaining layers, correcting each in turn. The end result is a ‘tied to wells’ average velocity volume. This product will allow more accurate representations of the interpreted time horizons in depth and will greatly enhance the confidence in planning wells and calculating hydrocarbon volumetrics.
As a byproduct of the velocity correction workflow, CoViz 4D allows the calculation of a depth uncertainty model, to help reservoir teams predict depths and reduce drilling risks in undeveloped regions.
Additional Well Data Further Reduces Subsurface Uncertainty
As a field is developed, CoViz 4D facilitates the use of additional well log data from new or infill wells
to further reduce depth uncertainty. CoViz 4D makes it easy to incorporate additional data and recalculate the velocity model. Using a customizable workflow, in a matter of minutes, a reservoir engineer specifies the source of the new data then re-runs the workflow to improve the accuracy of the velocity and depth conversions. As additional wells are drilled and velocity models are recalculated using the newly-acquired data, the accuracy of velocity and depth conversions continue to improve, leading to greater confidence in planning and executing reservoir development activities.
In addition to offering a velocity model that reduces depth uncertainty errors, CoViz 4D enhances the understanding of subsurface environments by visualizing wells in the context of the updated velocity models that give reservoir engineers a clearer understanding of subsurface environments.
Improved Accuracy in Locating Targets
Geoscientists determine drilling targets using a combination of seismic, geologic, and reservoir models. Traditionally, the target information is then passed to well planners and drilling engineers via spreadsheets. This approach ignores the value of developing drilling plans in the context of the actual geology. Without a visual understanding of proposed well plans in the context of geology, well planners cannot achieve optimal well placement within a reservoir, and/or may lack the understanding of crucial hazards or markers.
Visualizing drilling targets (yellow spheres) in the context of geology and seismic with CoViz 4D can greatly enhance the understanding of risks and uncertainties. Data courtesy Rocky Mountain Oilfield Technology Center and USDOE.
CoViz 4D overcomes this limitation, enabling drilling engineers to more readily identify geologic risks and uncertainties, by incorporating the geologic model into the planning and drilling phases. Geoscientists, well planners, and drilling engineers can collaborate using the 3D environment that renders geologic data in detail. Targets are easily defined directly in CoViz 4D using 2D and 3D shapes. As the well plan is drilled, the geologist and drilling engineer can update their position relative to the geologic model, verify the accuracy of the model, and, if necessary, make appropriate modifications to geometrically steer the well to its ideal location.
Data Integration, Unique Velocity Modeling, and Visualization Reduce Subsurface Uncertainty
CoViz 4D is unique in its ability to integrate a wide range of reservoir data—including geologic models developed with other vendors’ software products such as Schlumberger’s Petrel. With CoViz 4D, users have access to a unique velocity model that incorporates well data to improve accuracy, and then, they can visualize all of these data to help reduce subsurface uncertainty. The synergy of data integration, more accurate velocity modeling, and a collaborative visualization environment significantly enhance the value of reservoir data, enabling multidisciplinary teams to more confidently assess subsurface conditions and recommend development strategies.