Precise geological modeling depicting intricate relationships among lithology, rock properties, and faults in structurally complex reservoirs are essential to successful hydrocarbon production. With access to detailed models geologists, geophysicists, and reservoir and production engineers are better informed to make critical decisions affecting reservoir development and operations.
For many operators, combining the various datasets to create accurate geological models remains one of the biggest obstacles to obtaining the greatest value from the data. The ability to visualize and apply analytic tools to geological models can further enhance the value of these data, allowing reservoir teams to explore and evaluate models to determine optimal recovery strategies.
Data, Algorithms, and Visualization Enhance the Value of Geological Modeling
EarthVision from Dynamic Graphics, Inc. is designed for analysis, synthesis, modeling, and visualization of spatially referenced data. It integrates geophysical and geological data such as seismic, wells, outcrops, and fluid samples. Using a proprietary set of gridding algorithms, EarthVision combines and verifies data to create accurate geologic models of complex structures. Throughout the life of a reservoir, it can automatically update geological models as new data becomes available.
The resulting models that characterize complex geologic geometries can be visualized in 2D and 3D structural contour maps, cross-sections annotated with geophysical logs, and three-dimensional property distribution within fault blocks. This level of detail provides a better understanding of geological models and facilitates collaborative decision making among reservoir team members.
This level of detail provides a better understanding of geological models and facilitates collaborative decision making among reservoir team members.
Combine Relevant Subsurface Data to Create Detailed Geological Models
EarthVision integrates all relevant data such as interpreted 2D and 3D seismic surveys, interpreted well logs, processed gravity and magnetic surveys, and borehole data (core samples, temperature, and pressure, etc.). Essentially any data with x/y/z location and associated attributes can be incorporated into the subsurface model. EarthVision uses a variety of algorithms to build the models, including capabilities to:
- Define faults and lithology surfaces using three-dimensional surfaces.
- Automatically calculate fault block 3D intersections and truncations.
- Grid horizon and property information in geometrically restored, unfaulted space to ensure consistency.
- Spatially sort horizon information by fault block with horizon surfaces generated for each block.
- Calculate intermediate surfaces based on a reference surface and limited intermediate horizon picks where horizon data are scarce.
- Integrate seismic interpretations in time with depth models using geo-model-driven velocity and time-to-depth conversion.
- Apply 2D and 3D minimum tension gridding algorithms to calculate a smooth surface that closely fits input data values.
- Employ kriging techniques to create 2D or 3D grids.
These algorithms are applied as part of a workflow (explained below) that guides the review of data and geological modeling. Upon completion, three-dimensional visual verification by reservoir teams provides a unique opportunity to discover fundamental relationships in scattered data, site information, and surfaces hidden in other graphic representations. The data resulting from this synergistic verification process provide an improved data “foundation” for all subsequent modeling and scientific investigation.
Workflow Facilitates Model Development
Workflow facilitates the development of geological models. A modeling workflow begins by assessing the available input data and examining them for consistency, detecting and correcting data when necessary.
Each data component (fault data, geologic horizons, rock properties, etc.) is reviewed, analyzed, cleaned up, and edited to improve data quality. Data are then used to calculate specific parts of the model.
- Fault data generate a model of each fault surface. Fault surfaces are then compared to all the other faults for consistency. A fault hierarchy or fault tree is generated to define how fault blocks in an area fit together.
- Geologic horizons data are examined together and compared to check for consistency and “geologic sense.”
- Fault and horizon data are combined to create a “zoneblock” model with all of the fault blocks and all the geologic zones inside them. These zoneblocks are rock containers—bounded by faults and geologic horizons.
- With zoneblocks created, the property modeling process begins. Rock properties such as porosity, permeability, shale content, gamma ray values, resistivity, etc., are modeled inside the 3D rock containers.
With property modeling completed, a wide range of calculations and analyses are now available. Volumetric calculations answer questions such as, “How much volume of oil could potentially be inside ‘Sand A’ of ‘Faultblock B’ where porosity is >35%, resistivity >200 ohms, permeability >90 millidarcies, and everything is above the oil-water contact at –7,500?”
Proper representations of layer juxtaposition across faults are critical to volumetric analysis, fluid migration, and hydrocarbon entrapment analyses. The 3D property models built with EarthVision’s geometric restoration technique provide rigorous representations of faulted reservoirs. The accuracy of the resulting models allows for greater confidence in well placement and reservoir management decisions.
Visualization for Data and Model Verification & Analysis of Complex Relationships
EarthVision excels in 3D geological modeling, analysis, and visualization. Customizable workflows streamline the process of building complex models that provide accurate representations of reverse faults, major fault gaps, and fault-wedge contours. These geological models facilitate a wide range of reservoir analyses including volumetric, hydrocarbon entrapment, and fluid migration. Powerful visualization capabilities enable model review and verification in full geologic context, helping reservoir teams to collaboratively determine the best development strategies.