From Drone-Based Remote Sensing to Digital Outcrop Modeling: Integrated Workflow for Quantitative Outcrop Interpretation

Abstract

Oil and gas exploration applies numerical modeling techniques to understand the development of hydrocarbon- bearing basins and to provide quantitative subsurface models. The accuracy of any prediction depends on several factors, such as the modeling approach, data acquisition, and data interpretation. Unfortunately, in the oil and gas industry the quantity of reliable data available to build models is very limited compared to the size of sedimentary basins. Outcrops are valuable sources of information that should be used to characterize the subsurface. Unfortunately, we are far from achieving the objective of fully benefiting from outcrops. Despite the fact that an outcrop is directly accessible, its quantitative modeling and integration remain an issue. Usually, we organize field trips where several experienced geologists are involved to collect descriptive data from outcrops, which include rock samples, measured sections, and photos. The outcomes from these field trips are mainly conceptual and qualitative models of the surface geology without any quantitative impact on the subsurface modeling and characterization workflows. Moreover, accessibility to cliffs or canyons in any outcrop is a major safety obstacle when conducting field trips. The main goal of this work is to investigate and develop new technologies for high resolution 3D outcrop modeling (cm to mm scale). High resolution outcrop models will constitute a virtual dataset that a geologist can visit at any time from his desktop. The proposed solution for this challenge is to develop an integrated workflow for remote geological assessment based on drones and remote sensing technologies. The general workflow starts with the selection of an area of interest using any geographic information system (GIS) to plan the flight route of the unmanned aerial vehicle (UAV). This is then followed by selection of the model type, for instance digital elevation, texture, and/or mineral composition as well as the required resolution. After acquiring the data using drones equipped with the appropriate sensors, we proceed to data processing, where the acquired data is converted to geological models that geologists can use to study the outcrop. Finally, general-purpose software is used for outcrop model visualization. This workflow was successfully applied to the Wadi Dirab outcrop in Central Saudi Arabia. Keywords: