Studies of turbidite channel complexes in outcrops, wells, and 3D seismic-reflection data suggest a general model of turbidite channel behavior related to three critical measures: (1) the thickness of channel elements; (2)the thickness of abandonment facies within each element; and (3) the thickness of overbank aggradation. These measures constrain channel stacking pattern and can be integrated into event-based geostatistical reservoir models that provide probabilistic predictions of net reservoir volume and element stacking pattern. Although channel and overbank thicknesses are measured routinely, this model provides a predictive framework that also emphasizes the importance of recognizing the presence and thickness of shale-rich abandonment facies at the top of sand-rich channel elements in outcrops.
For a given flow composition, the deposits of thick channel elements (thickness of active fill plus abandonment facies) tend to have relatively low sand percentage, abundant bypass facies, and thick abandonment facies (underfilled channels). Underfilled channel elements with high topographic relief, from levee crest to channel thalweg, at the time of abandonment influence the location of subsequent elements, resulting in an organized channel stacking pattern. The deposits of relatively thin channel elements tend to have higher sand percentage, small volumes of bypass facies and thin/absent abandonment facies. Filled channel elements with low topographic relief at the time of abandonment had little influence on the location of subsequent elements, which resulted in a disorganized channel stacking pattern. Channel ‘‘relief ’’ corresponds to the depth of erosion plus the height of the levee crest above the initial sea floor. We observe that erosion relief can correlate strongly with downslope gradient. Flow composition also is critical because the rate of overbank aggradation is strongly influenced by mud volume. Muddy flows tend to produce thick overbank aggradation, high confinement, and under-filled channels with an organized stacking pattern. Sand-rich flows tend to produce relatively low overbank aggradation, low confinement (unless erosion relief is high), and filled channels with a disorganized stacking pattern.