Process-Based Simulations of Sediment Gravity Flows as Mechanisms for the Formation of Hydrocarbon Reservoirs in Deep Marine Environments

Basani, Riccardo ¹; Janocko, Michael ²; Hansen, Ernst W.¹; Tantserev, Evgeniy ¹; Rouzairol, Romain ¹; Heimsund, Snorre ³; Aas, Tor E.⁴; Howell, John A.⁴
(1)Complex Flow Design AS, Trondheim, Norway. (2) Department of Earth Science, University of Bergen, Bergen, Norway. (3) Norwegian Energy Company ASA, Stavanger, Norway. (4) Centre for Integrated Petroleum Research, Bergen, Norway.

Turbidity currents are important mechanism for the dispersal and deposition of sand in the deep-sea setting and one of the main phenomena leading to the formation of oil and gas reservoirs. The flow characteristics of turbidity currents are difficult to observe 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 for 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 CFD analysis realized as numerical simulations is being developed to fill the gap between small and large scale, 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. Novel CFD software, called MassFLOW-3D™, has been developed and successfully used to construct a 3-dimensional model for the simulation of turbidity currents. All principal hydraulic properties of the flow (e.g., velocity, density, sediment concentration, turbulence intensity,shear stress) and its responses to topography can be continuously monitored in 3 dimension. In the work here presented, we apply MassFLOW-3D™ to investigate the geometry of turbidite successions on a basin scale. A number of simulations have been run on 3D surfaces representing the palaeoseafloor bathymetry of the Peïra Cava Basin and the Ormen Lange field, North Sea. Special attention has been given to the response of turbidity currents to basin-floor topography and its effect on differential stacking of consecutive deposits by flow ponding or spill-over, which bears direct implications for the succession’s primary heterogeneities (lateral and vertical facies changes, sand net/gross variation, sand pinchouts).The location of the source point, as well as characteristics of the flow, such as velocity, flow height, width and sediment concentration play a fundamental role in the resulting geometry of the deposited sand. The wide range of simulated cases in combination with the palaeogeomorphological seafloor maps may thus offer unprecedented new insight into the flow behaviour of turbidity currents, and the geometry of hydrocarbon-hosting turbidite successions.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.