HIERARCHICAL MODELING OF DEEPWATER CHANNELIZED RESERVOIRS: THE DIFFERENCE THAT MAKES A DIFFERENCE

The fundamental building blocks of channelized deepwater depositional systems are individual channel elements and their fill. The basic condition or “rule” utilized for defining new elements is the process of avulsion, which is the sudden shift in channel location. Therefore, avulsions control the vertical and lateral stacking of channel elements. Deepwater channel complexes are defined as two or more elements of similar grain size, lithofacies, architectural style, and depositional trend. Outcrop and seismic datasets show complexes of channels stacked in organized or disorganized patterns.

The aforementioned deepwater stratigraphic hierarchy and its developmental conditions form the basis of rules-based reservoir modeling, such as surface-based and event-based geostatistics. Traditional geostatistical algorithms are limited in their ability to integrate information or “rules” related to depositional processes as they do not directly account for process and temporal sequence. Event-based modeling is a stochastic, forward, rules-based vectorial method that efficiently integrates empirical observation and expert knowledge with respect to depositional process and stratigraphic architecture. Resulting models exhibit a high level of complexity and realism at little computational cost. In addition to producing more robust reservoir models for training, flow simulation, and conditioning to sparse well data and seismic, event-based geostatistics can serve as a digital laboratory for testing stratigraphic frameworks and concepts.

Hierarchical deepwater stratigraphic concepts and rules allow for more accurate, event-based reservoir models with reduced degrees of model uncertainty. This is possible because hierarchy is amenable to quantification of stratigraphic inputs to models, including geobodies and their evolutionary patterns.