Geoscientists today are faced with working in areas of increasing depositional and structural complexity and are under increasing pressure to produce and deliver highquality interpretation results within shorter deadlines. Many geoscientists today employ a number of 3D interpretation methodologies to help assist in this task. There are, in essence, two end-member methodologies that are used to visualize depositional systems, surface-based approaches and volume-based approaches (Fig. 1). Surface-based approaches rely on high-precision horizon auto-picking which captures subtle depositional features along the surface being mapped. Techniques such as volume lighting, surface attribute displays (e.g., curvature), or draped volume attributes are then used to enhance subtle details. Visualization along time/depth slices or inclined dipping planes within 3D surveys fall into this end-member category as they only reveal data along a single interface.

Volume-based visualization of depositional systems, which represents my primary focus here, relies on the use of opacity on targeted parts of the data sets. When working in reconnaissance mode, volume-based visualization is often performed with minimal horizon interpretation. Typically, when more detailed analysis is performed, a structural and sequence stratigraphic framework is used to focus the volume-visualization to targeted intervals.

Methods

My colleagues and I used both reconnaissance and detailed volume-based structural and stratigraphic extraction techniques to improve vertical and lateral understanding of depositional systems. A key part of using volume-based approaches is to understand which tool or combination of tools needs to be applied to isolate and visualize geological intervals of interest in order for analysis to take place (Fig. 2). Use of additional seismic attributes such as spectral decomposition can further improve the effectiveness of these techniques. Depositional systems can be viewed separately and also collectively in 3D using volume-based visualization approaches. Figure 3 shows an illustration of how geobody extraction and sequence sculpting are used together to examine the relationship of two separate depositional systems. Depositional systems are often segmented compartmentalized by faulting of various scales. Automated fault-extraction methods produce non-biased results and provide information about fault timing and depositional processes, which are not easily observed when performing manual fault interpretation and provide significant information that increases understanding of reservoir production behavior.

Figure 1. The two end-member visualization types used in 3D visualization.

Figure 2. This figure illustrates several examples of frequently used approaches to isolate depositional systems within 3D seismic data sets.

Figure 3. Composite image of multiple depositional features built to visualize and observe complex geological history in this area.

Summary and Conclusions

During a study of the West of Shetland’s area, we utilized automated horizon interpretation, sequence sculpting, and geobody detection to isolate depositional systems and elements in order to perform focused stratigraphic analysis and interpretation. Opacity rendering was used to enhance the subtle depositional fabric within this complex depositional setting. Coherence cube, spectral decomposition, and instantaneous attributes enabled me to delineate and understand the nature of the internal reservoir architecture.