Abstract: From Rocks to Models: Three-Dimensional Visualization as a Tool to Integrate Sedimentology and Sequence Stratigraphy into Reservoir Models

TINKER, SCOTT W.

If every subsurface reservoir had an exact analog exposed in a continuous outcrop, interpretation of subsurface frameworks would improve dramatically. Unfortunately, this is not the case. Three-dimensional visualization technology provides a tool that allows the interpreter to "visualize" the stratigraphic framework, in much the same way one would look at an outcrop. Used in this fashion, visualization becomes an interactive interpretation tool that relies on the remarkable ability of the human mind to process and comprehend a color, animated image. As such, visualization is a powerful component of reservoir characterization.

The 3-D reservoir model, which incorporates core, wireline log, seismic, and production data within a 3-D stratigraphic framework, is an important product of the reservoir characterization process. The model-building process is dynamic, with constant modification made as a function of visualization, new data, and fresh ideas. One of the risks of 3-D modeling is that the attractive visual result can mask an erroneous stratigraphic interpretation and/or poor choice of data-distribution methods. An erroneous 3-D model used as a reservoir development tool can actually have a negative impact on production results. In contrast, an accurate 3-D model provides a realistic matrix permeability interpretation, and is a powerful reservoir management tool.

The stratigraphic/structural framework plays an important role in 3-D reservoir modeling, because the framework constrains the distribution of data in 3-D space. A rigorous sequence-stratigraphic interpretation provides the best framework for 3-D data distribution. Reservoir-scale
If every subsurface reservoir had an exact analog exposed in a continuous outcrop, interpretation of subsurface frameworks would improve dramatically. Unfortunately, this is not the case. Three-dimensional visualization technology provides a tool that allows the interpreter to "visualize" the stratigraphic framework, in much the same way one would look at an outcrop. Used in this fashion, visualization becomes an interactive interpretation tool that relies on the remarkable ability of the human mind to process and comprehend a color, animated image. As such, visualization is a powerful component of reservoir characterization.

The 3-D reservoir model, which incorporates core, wireline log, seismic, and production data within a 3-D stratigraphic framework, is an important product of the reservoir characterization process. The model-building process is dynamic, with constant modification made as a function of visualization, new data, and fresh ideas. One of the risks of 3-D modeling is that the attractive visual result can mask an erroneous stratigraphic interpretation and/or poor choice of data-distribution methods. An erroneous 3-D model used as a reservoir development tool can actually have a negative impact on production results. In contrast, an accurate 3-D model provides a realistic matrix permeability interpretation, and is a powerful reservoir management tool.

The stratigraphic/structural framework plays an important role in 3-D reservoir modeling, because the framework constrains the distribution of data in 3-D space. A rigorous sequence-stratigraphic interpretation provides the best framework for 3-D data distribution. Reservoir-scale sequence stratigraphic interpretation involves a systematic process of 1-D, 2-D, and 3-D interpretation of core, wireline log, seismic, and production data. The result is a 3-D stratigraphic framework interpretation that is consistent and repeatable. The stratigraphic complexity, and therefore interpretation difficulty, increase as a function of depositional topography and magnitude of eustatic sea level change (icehouse vs. greenhouse). Although most reservoir-scale interpretations today are called sequence stratigraphic, some do not honor depositional environment and accommodation constraints. Examples of erroneous stratigraphic interpretations include horizontal stratigraphy in an actual clinoform setting (e.g., shelf margin), and clinoform stratigraphy in an actual horizontal setting (tidal flat); toplap with an associated erosional sequence boundary in an actual shelfward-thinning sigmoidal clinoform setting; and onlap onto an underlying margin in an actual high-angle sigmoidal clinoform setting.

Examples from several depositional settings will be used to illustrate the process of high-frequency sequence-stratigraphic interpretation and the 3-D geologic models that result, including "layer-cake" stratigraphy in a tidal flat setting, low-angle sigmoidal clinoforms in a ramp setting, high-angle sigmoidal clinoforms in a steep-rimmed margin setting, and complex sigmoid-oblique clinoforms in a steepened-ramp setting.

AAPG Search and Discovery Article #90938©1997-1998 AAPG Distinguished Lecturers