Most submarine canyons are erosive conduits cut deeply into the world's continental shelves through which sediment is transported from areas of high coastal sediment supply onto large submarine fans. However, many submarine canyons in areas of low sediment supply do not have associated submarine fans and show significantly different morphologies and depositional processes from those of 'classic' canyons. Using three-dimensional seismic reflection and core data, this study contrasts these two types of submarine canyons and proposes a bipartite classification scheme.The continental margin of Equatorial Guinea, West Africa during the late Cretaceous was dominated by a classic, erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was reactivated in the Miocene during tectonic uplift. A subsequent decrease in sediment supply resulted in a drastic transformation in canyon morphology and activity, initiating the 'Benito' canyon system. This non-typical canyon system is aggradational rather than erosional, does not indent the shelf edge and has no downslope sediment apron. Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the canyons. Intra-canyon lateral accretion 2 deposits indicate that canyon concavity is maintained by thick (> 150 m), dilute, turbidity currents. There is little evidence for erosion, mass wasting, or sand-rich deposition in the Benito canyon system. When a canyon loses flow access, usually due to piracy, it is abandoned and eventually filled. During canyon abandonment, fluid escape causes the successive formation of 'cross-canyon ridges' and pockmark trains along buried canyon axes.Based on comparison of canyons in the study area, we recognize two main types of submarine canyons: 'Type I' canyons indent the shelf edge and are linked to areas of high coarse-grained sediment supply, generating erosive canyon morphologies, sandrich fill, and large downslope submarine fans/aprons. 'Type II' canyons do not indent the shelf edge and exhibit smooth, aggradational morphologies, mud-rich fill, and a lack of downslope fans/aprons. Type I canyons are dominated by erosive, sandy turbidity currents and mass wasting, whereas hemipelagic deposition and dilute, sluggish turbidity currents are the main depositional processes sculpting Type II canyons. This morphology-based classification scheme can be used to help predict depositional processes, grain size distributions, and petroleum prospectivity of any submarine canyon.

Most submarine canyons are erosive conduits cut deeply into the world’s continental shelves through which sediment is transported from areas of high coastal sediment supply onto large submarine fans. However, many submarine canyons in areas of low sediment supply do not have associated submarine fans and show significantly different morphologies and depositional processes from those of ‘classic’ canyons. Using three-dimensional seismic reflection and core data, this study contrasts these two types of submarine canyons and proposes a bipartite classification scheme.The continental margin of Equatorial Guinea, West Africa during the late Cretaceous was dominated by a classic, erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was re- activated in the Miocene during tectonic uplift. A subsequent decrease in sediment supply resulted in a drastic transformation in canyon morphology and activity, initiating the ‘Benito’ canyon system. This non-typical canyon system is aggradational rather than erosional, does not indent the shelf edge and has no downslope sediment apron. Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the canyons. Intra-canyon lateral accretion deposits indicate that canyon concavity is maintained by thick (> 150 m), dilute, turbidity currents. There is little evidence for erosion, mass wasting, or sand-rich deposition in the Benito canyon system. When a canyon loses flow access, usually due to piracy, it is abandoned and eventually filled. During canyon abandonment, fluid escape causes the successive formation of ‘cross-canyon ridges’ and pockmark trains along buried canyon axes.Based on comparison of canyons in the study area, we recognize two main types of submarine canyons: ‘Type I’ canyons indent the shelf edge and are linked to areas of high coarse-grained sediment supply, generating erosive canyon morphologies, sand- rich fill, and large downslope submarine fans/aprons. ‘Type II’ canyons do not indent the shelf edge and exhibit smooth, aggradational morphologies, mud-rich fill, and a lack of downslope fans/aprons. Type I canyons are dominated by erosive, sandy turbidity currents and mass wasting, whereas hemipelagic deposition and dilute, sluggish turbidity currents are the main depositional processes sculpting Type II canyons. This morphology-based classification scheme can be used to help predict depositional processes, grain size distributions, and petroleum prospectivity of any submarine canyon.

Petroleum system modeling provides the timing, type and volume of fluids entering a reservoir, among other things. However, there has been little modeling of the fluid processes that take place within the reservoir in geologic time, yet these processes have a dramatic impact on production. Modeling and understanding of the reservoir then reinitiates with simulation of production for optimization purposes. The new discipline "reservoir fluid geodynamics" (RFG) establishes the link between the petroleum system context or modeling and present day reservoir realizations. This new discipline has been enabled by scientific developments of the new asphaltene equation of state and by the technology of downhole fluid analysis (DFA). Gas-liquid equilibria are treated with the traditional cubic EoS. Crude oil fluid- asphaltene equilibria are treated with the Flory-Huggins-Zuo equation of state with its reliance on the Yen-Mullins model of asphaltenes. Thermodynamic treatment is essential in order to identify the extent of equilibrium in oil columns, thereby identifying fluid dynamics in geologic time. DFA is shown to be very effective for establishing asphaltene gradients vertically and laterally in reservoir fluids with great accuracy. In turn, this data tightly constrains the thermodynamic analyses. These methods have been applied to a large number of reservoir case studies over a period of ten years. For example, case studies are shown that indicate baffling and lower production for parts of the reservoir that have slower rates of fluid equilibration. In addition, the newly revealed lateral sweep in trap filling is established via RFG case studies. Underlying systematics, especially for gas charge into oil reservoirs, have been revealed for a large number of fluid and tar distributions that enable a unifying and simplified treatment for seemingly intractable complexities. A case study is presented that shows three very different reservoir realizations in adjacent fault blocks for the same petroleum system model, where RFG explains all these differences. This enables key reservoir properties to be projected away from wellbore in ways not previously possible. Finally, universal work flows are shown which enable broad application of these methods through all phases of reservoir exploration and production.

Deposition of organic solids high in asphaltene content (tar, bitumen) in reservoirs from natural processes is a routine occurrence around the world. Nevertheless, there is a bewildering array of deposition characteristics as shown in recent case studies. Sometimes this tar or bitumen (both are really the same material) is at or near the crest; sometimes it is on interlayers within a heterolithic sequence (baffles) or at the base of the reservoir which can be tens of kilometers away from the crest. Sometimes the bitumen deposition is such that the corresponding formation remains permeable; sometimes the tar zone is totally impermeable. Sometimes the tar at the base of the reservoir represents a more or less continuous increase in asphaltenes from the oil immediately above the tar; sometimes there is a sharp, discontinuous increase in asphaltene content from the oil to the tar. And particularly for upstructure bitumen, sometimes the bitumen is deposited throughout the entire producing interval (in a well); at other times the bitumen deposition is only at the base of the producing interval. This paper shows that ALL of these variable tar or bitumen characteristics can be understood within simple concepts that treat the dissolved asphaltene in crude oils and the deposited asphaltene within the same framework. This framework utilizes simple chemical solution characterisitcs that are formally expressed in the Flory-Huggins-Zuo Equation of State for asphaltene gradients with its reliance on the Yen-Mullins model of asphaltenes. Multiple charges of incompatible fluids lead to asphaltene deposition. The extent of slow, diffusive destabilization from density stacking charge fluids versus rapid destabilization from a secondary lateral fluid front controls much of the characteristics of deposited asphaltene. Consequently, the proximity of the well to reservoir charge points as well as petrophysical parameters of the formations are very important parameters. The ideas herein enable projection of the nature of asphaltene deposition away from a wellbore to other locations in the reservoir. This capability greatly assists the ability to understand the impact of asphaltene deposition on production.

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