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Explore Your Reservoirs Using Fluid Dynamics
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MassFLOW-3DT M simulation software, developed by the Norwegian company Complex Flow Design, generates in-depth analysis of turbidity currents, one of the main phenomena leading to the formation of hydrocarbon reservoirs in deep-water deposits.
Turbidity currents are the most important mechanism for the erosion, transport and deposition of sand in the deep-sea setting and one of the main phenomena leading to the formation of oil and gas reservoirs in deep water deposits. The flow characteristics of turbidity currents are difficult and expensive to observe and study from the modern environment, while their experimental small scale approximations are typically hampered by scaling issues, unrealistic flume geometries and short durations. Computational fluid dynamics (CFD) is a tool to provide numerical solution of the physical equations describing fluid flow and sediment transport. The method has been widely applied in the engineering branches of fluid mechanics, but has thus far been little used in sedimentological research and reservoir studies. Nowadays computational fluid dynamic analysis realised as numerical simulations is being developed to fill the gap between small and large scales, integrating data from theory, nature, and experiments. It can also shed light on flow parameters which are so far impossible to deduce from experimental and field studies.
MassFLOW-3D™ software was developed and used to construct a three-dimensional model for the simulation of turbidity currents. All principal hydraulic properties of the flow (e.g. velocity, density, sediment concentration, apparent viscosity, turbulence intensity, bottom shear stress) and its responses to topography can be continuously monitored in three dimensions over the whole durationof the vent. However, continuous customisation, implementation of subroutines aimed at sediment transport and deposition, and validationof these models are essential in improving the computational code and our understanding of the natural phenomena of multi-phase flow. Figure 1 shows the characteristic flow-pattern in the front head and the body in a turbidity current evolving along the sloping sea-bed.
The MassFLOW-3D™ software was used to simulate turbidite deposition in the Ormen Lange field, offshore Norway. The basin-floor topography used was the basal surface of the reservoir’s Egga Unit, derived from 3D seismics combined with back-stripping and decompaction tools. The deformation induced by the Storegga Slide was removed. The aim of these simulations was to assess the influence of basin-floor topography on the spatial pattern of sediment dispersalby turbidity currents in the Ormen Lange area, assuming a point-source scenario obtained from previous researchers. A few tens of identical large-scale turbidity currents were run over the topographic surface to monitor their changing velocity field and sediment dispersal pattern, (see Figure 2). The results show that turbidity currents are highly sensitive to subtle variations in the seafloor topography and confirm further the notion that the Ormen Lange sub-basin was supplied with sediment from a single main source in the southeast.
The main conclusions from the simulation work performed are:
- Turbidity currents are highly sensitive to subtle variation in basin-floor topography.
- The Ormen Lange depo-centres were probably supplied with sediment mainly from sources in the southeast.
- The sediment transport direction is still considered to be mainly to the north, due to subtle topographic confinement to the east and west.
- Coeval sedimentation occurs in the depo-centres with the areas in between possibly acting as a bypass zone, dominated by erosion and sediment re-suspension.
- As the primary topographic relief was gradually smoothed out by sediment accumulation, the whole area began to act increasingly as a bypass zone.
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