From Conventional Outcrop Datasets to Flow Simulation: the Fluvial Strata in Pont de Montanyana (Ypresian, Southern Pyrenees)

The study and modelling of outcrops as reservoir analogues have been widely used in the oil industry to understand the complexity in the subsurface. Some uncertainties faced by geologists, geophysicists and engineers in the... [ view full abstract ]

The study and modelling of outcrops as reservoir analogues have been widely used in the oil industry to understand the complexity in the subsurface. Some uncertainties faced by geologists, geophysicists and engineers in the management of hydrocarbon reservoirs are associated to the type and distribution of facies, which in turn control the petrophysical properties of rocks, and influence directly the way in which the hydrocarbon is produced. The Pont de Montanyana outcrop is among the world class outcrops in southern Pyrenees and is visited by many industry and academic schools. The outcrop exposes strata that deposited in poorly drained alluvial plains and meandering streams in the context of the Tremp-Graus piggy back basin. Point bar deposits up to 10 m thick and 600 m wide are present in the outcrop at two stratigraphic positions. The upper point bar was the subject of our research, aimed at producing a very detailed 3D facies model to be used as a playground to test and compare reservoir production strategies. The initial dataset resulted from a combination of conventional outcrop descriptions (correlated logs and paleocurrent data) with 3D interpretations of Digital Outcrop Models acquired using DGPS, LiDAR and Multiview 3D technologies. The 3D outcrop dataset was then used to produce a horizon framework in the uppermost channel-fill body, and this was followed by the creation of modeling grids that reproduce the bedding characteristic of each channel evolution’s stage. A combination of deterministic and stochastic methods was used to build a facies model which was constrained to field-measured stratigraphic logs and pseudowells derived from the digital outcrop model. The 3D grid was populated with petrophysical data from point bar reservoirs available in the literature and constrained to the facies model. Moreover, several flow simulations, based on water injection strategies, were performed. The results show that more than 20% of moveable oil is trapped at the upper part of the point-bar deposits, revealing the strong control of the facies distribution on the efficiency of this type of reservoirs. We acknowledge financial support from Project SEROS CGL2014-55900-P. Schlumberger and ROXAR are acknowledged for donation of Petrel and RMS licenses, respectively.