Application of 3D outcrop data in reservoir geology on the examples of fractured carbonates in the Upper Rhine Graben

3D field applications have a high potential to gain large amounts of data in a relatively fast time from former inaccessible reservoir analog outcrops. We apply terrestrial laser scanning (t-LiDAR) and UAV-based Structure from Motion (SfM) on fractured Muschelkalk outcrops on the graben shoulder of the Upper Rhine Graben. Upper Muschelkalk carbonates are an important E&P target in the Upper Rhine Graben, but reservoir characterization from 1D subsurface data is insufficient for a broad understanding of fracture networks in the tight carbonates. Therefore, we work in well exposed open pit mines with the aim to unravel fracture spacing, orientation and history and help improve reservoir exploration and production.

Our terrestrial laser scanner (Lidar) derives the fracture orientation and spacing from steep inaccessible vertical quarry walls with an in-house developed workflow. Additionally, quarry floors can be imaged by our UAVs, resulting in high resolution orthophotos from which we derive relative age relationships and lateral continuity of fractures. Based on quarry data, we build a discrete static 3D fracture network and are able to simulate fluid flow with state of the art software tools such as FracMan, FracaFlow and Petrel.
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The Upper Muschelkalk in the studied outcrop reveals m-scale kink-bands and buckling in highly anisotropic layers of carbonates and shales revealing the tectonic history of the area generally driven by the alpine stress field and more recent evolution of the Upper Rhine Graben.

A minimum of five fracture generations were derived from quarry wall- and floor data. Based on abutting relationships, the oldest and most persistent fractures strike N-S. However, N-S striking fractures, which are often carbonate cemented, abutting on WNW- ESE striking fractures can also be observed pointing to fracture reactivation. We measured open fractures across steep faults but were not able to establish fault related fracture corridors, but cemented carbonate veins.

First results show that our automated fracture detection workflow based on point cloud data in combination with field observations are a promising tool for reservoir scale outcrop characterization. We suggest that the fractured carbonates in the Rhine graben region show a different structural history than originally thought.