Petrophysics of fine-grained mass-transport deposits: A critical review

Abstract

Highlights 1. Fine-grained MTDs comprise a 'main body' and a 'basal shear zone'; 2. The main bodies of MTD have contrasting petrophysical properties to their basal

Stacked debris flows offshore Sakarya Canyon, western Black Sea: morphology, seismic characterization and formation processes

“…The only exception for this hypothesis is a part of DB6 debris flow (Figure 8a), some part of which is located directly beneath a BSR reflection. We tentatively interpret that the gas hydrates occurring directly above DB6 in this area might be formed by in-situ biogenic gas production, or there would be a lateral gas migration especially along fractured basal shear of the debris as suggested by Sun and Alves (2020). In fact, this suggestion needs further investigation, especially applying gas chromatography analyses.…”

“…There are many different agents that trigger submarine mass failures. These include seismicity or seismic loading, slope oversteepening, sea-level variations, local fault activity, submarine fluid-flow/gas hydrate dissociation, high sedimentation rates causing excess pore pressures as well as submarine erosional processes (e.g., Cauchon-Voyer et al, 2008;Mulder et al, 2009;Dondurur et al, 2013;Ducassou et al, 2013;Rovere et al, 2014;Çukur et al, 2016;Sun and Alves, 2020). Although the earthquake loading is considered to be the most effective factor for the mass movements, in most cases, multiple factors are effective on the failures.…”

“…In most cases, there is no BSR in the shallower sediments if there is a debris flow beneath (Figure 9). Several researchers (e.g., Dugan, 2012;Reece et al, 2012;Hornbach et al, 2015;Sun et al, 2018;Sun and Alves, 2020) suggested that the debrites can be characterized by their high velocity, bulk density and shear strength as well as their lower porosity, water content and permeability as compared to the surrounding sediments because of the over-consolidation of the debris material formed during their emplacement and burial. They also proposed that debris flow deposits can be considered as good seal units to prevent the vertical fluid migration after their emplacement.…”

“…Evaluation of downslope mass movements and investigation of slope stability of a region as well as their formation and triggering mechanisms draw attention in recent years since they are quite important for the risk analyses related to the possible natural disasters (Cauchon-Voyer et al, 2008). This is because they (i) reshape the continental slopes, (ii) directly affect the sedimentary structure of the slope and deep basins, (iii) carry large amounts of sediments to deep basins, (iv) have the potential to create destructive tsunamis, (v) may damage to offshore geoengineering structures such as pipelines or submarine cables, and (vi) constitute good cap rocks for deeper hydrocarbons due to their low permeability and porosity (e.g., von Huene et al, 2004;Krastel et al, 2006;Dondurur and Çifçi, 2007;Reece et al, 2012;Dondurur et al, 2013;Sun and Alves, 2020;Sun and Leslie, 2020). In addition, subaqueous sediment gravity flow deposits are considered as a major reservoir plays in lacustrine basins today (Yang et al 2019).…”

Thrust Faults Promoted Hydrocarbon Leakage at the Compressional Zone of Fine-Grained Mass-Transport Deposits

“…Thrust faults are mainly imaged by geophysical data (e.g., seismic reflection data) and shown as imbricated structures (Lamarche et al, 2008;Lackey et al, 2018). Because of the shear compaction and dewatering during the mass movement (e.g., decreases of porosities and permeability), MTDs, especially those mainly composed of unlithified fine-grained sediments, are proposed as seal/barrier for the vertical fluid flow (Dugan, 2012;Alves et al, 2014;Sun and Alves, 2020). Furthermore, failed sediments are inclined to accumulate and thus thicken at the compressional toe zones (Moscardelli et al, 2006;Lamarche et al, 2008).…”