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3-D Geologic and Reservoir Modelling of a Distributive Fluvial System Derived From Lidar: A Case Study of the Huesca Fluvial Fan

Abstract

The Huesca fluvial fan is a well-documented, Oligocene – Miocene age distributive fluvial system in the northern extent of the Ebro Basin, and is used extensively as an outcrop analogue for modelling fluvial hydrocarbon reservoirs. To further improve understanding of the system, modern mapping and modelling techniques using lidar integrated with Differential Global Navigation Satellite System (DGNSS) measurements were used to create sub-meter (spatially) accurate geologic models of the medial-distal portions of the system. In addition to the digital terrain data, traditional field data was also collected near the town of Piracés in a series of amphitheatres and canal cuts that expose excellent two and three-dimensional views of the strata in the medial-distal portion of the fluvial system. The geologic models and subsequent analyses derived from the data will provide a quantitative tool to further understand the depositional architecture, geometric relationship and lithologic characteristics across the studied portion of the system. Utilizing the inherent quantitative nature of the terrain data in combination with the traditional field data collected, an outcrop based geocellular model of the studied section has been constructed by using several geostatistical modelling approaches to describe geo-body geometries (thickness, width and flow direction) for the associated fluvial architecture, as well as facies distribution and petrophysical characteristics. The resolution of the digital terrain data (<10cm) allowed for an accurate integration of the field observations (palaeoflow, sedimentary structures and grain size distributions) into a more complete model of fluvial system. The three-dimensionality of the exposure lends well to using lidar as a tool when mapping geo-body geometry and architecture across several kilometres. This approach leads to more accurate, quantitative reservoir and depositional models of the distributive fluvial system.