Differential compaction over Late Miocene submarine channels in SE Brazil: Implications for trap formation

Abstract

We used high-quality three-dimensional (3-D) seismic data to quantify the timing and magnitude of differential compaction over a Late Miocene submarine channel complex in SE Brazil (Espírito Santo Basin). A thicknessrelief method was applied to quantify the thickness variations in strata deposited over the channel complex. We found that differential compaction started after the channel complex was buried by ~200 m of strata, as revealed by thinning horizons observed over a compaction-related anticline. The size of the anticline is greatest in the south of the study area, reaching heights of 41 ms (~50 m). Fluid expelled through faults on the margins of the channel complex formed large depressions. These depressions increased in size after deep-water currents removed the fluid-rich sediment filling them. Differential compaction also occurred over deposits downslope of knickpoints, reaching maximum heights of 29 ms (~35 m). Seismic reflections onlap the knickpoint face and are believed to comprise slumped strata and debrites. Two-way traveltime isochron and amplitude maps indicate that there are limited connectivity and lateral continuity of the coarse-grained units. Differential compaction over these deposits created anticlines with four-way dip closure. As a consequence, isolated reservoirs were closed vertically by the compaction anticlines and laterally by strata onlapping the knickpoint face. These unique reservoirs could have been charged by migration of hydrocarbons along sands at the base of the channel complex. A fill-to-spill model is hypothesized using the above mechanism: Once an isolated anticlinal trap reached spill point, hydrocarbons migrated upslope into the next trap. Traps like these could form above submarine channels in similar basins around the world (e.g., Gulf of Mexico, west coast of Africa) after early burial.

Reutilisation of hydrothermal vent complexes for focused fluid flow on continental margins (Modgunn Arch, Norwegian Sea)

“…Schmiedel et al. (2017) also showed that the dome above the Tulipan sill was formed by a combination of syn‐sill‐emplacement forced folding and post‐emplacement differential compaction, the latter of which is an important mechanism for forming subtle traps for hydrocarbons (Ward, Alves, & Blenkinsop, 2018). This work also shows that hydrothermal vent complexes play an important role in controlling the plumbing system of a volcanic sedimentary basin.…”

“…If forced folds are created above saucer-shaped sills, this creates a possible trapping mechanism as evidenced by the Tulipan well in the outer Møre Basin, where a small gas discovery was recorded in a dome above a saucer-shaped sill (Holford et al, 2012;Kjoberg et al, 2017;Polteau et al, 2008;Schmiedel et al, 2017). Schmiedel et al (2017) also showed that the dome above the Tulipan sill was formed by a combination of syn-sill-emplacement forced folding and post-emplacement differential compaction, the latter of which is an important mechanism for forming subtle traps for hydrocarbons (Ward, Alves, & Blenkinsop, 2018). This work also shows that hydrothermal vent complexes play an important role in controlling the plumbing system of a volcanic sedimentary basin.…”

Turbidites, topography and tectonics: Evolution of submarine channel‐lobe systems in the salt‐influenced Kwanza Basin, offshore Angola

“…In addition, pre‐existing sedimentary features may have an expression on the sea‐floor, such as differential compaction of stacked channels (e.g. Ward, Alves, & Blenkinsop, 2017) and mass transport deposits (e.g. Ortiz‐Karpf, Hodgson, & Mccaffrey, 2015; Zhao, Qi, Patacci, Tan, & Xie, 2019).…”

“…Instead, in the decay stage, subtle structural highs control major avulsion nodes along or immediately down-dip of fold flanks due to occasional re-activation of salt movement through squeezing (Figure 18c). Differential compaction of thicker minibasin fill (>200 m burial sensu Ward et al, 2017) may also play an important role in controlling avulsion node localities through creating gradual gradients. Although most of the salt-cored structures are low-relief during this stage, some large structures may be long-lived and continue blocking sediment transport pathways and ponding sediments ( Figure 18c).…”

An alternative interpretation for the formation of doubly plunging folds in sandstone terrains

“…Domes caused by differential compaction of the local heterogeneous stratigraphy (e.g. Ward, Alves, & Blenkinsop, 2018). Elongated domes created by crystalline basement rock uplifted along faults that parallel the long axis of the dome structures (e.g.…”