Fracture-Network 3D Characterization in a Deformed Chalk Reservoir Analogue-the Lägerdorf Case

Abstract

Summary Quantitative descriptions of 3D fracture networks in terms of fracture characteristics and connectivity are necessary for reservoir evaluation, management, and EOR programs of fractured reservoirs. Our research has focused on an analogue to North Sea fractured chalk reservoirs that is excellently exposed near Lägerdorf, northwest Germary. An underlying salt diapir uplifted and deformed Upper Cretaceous chalk; the cement industry now exploits it. The fracture network in the production wall of the quarry was characterized and mapped at different scales, and 12 profiles of a 230-m wide and 35-m high production wall were investigated as the wall receded 25 m. In addition, three wells were drilled into the chalk volume. The wells were cored and the wellbores were imaged with both the resistivity formation micro scanner (FMS) and the sonic circumferential borehole image logger (CBIL). The large amount of fracture data was analyzed with respect to parameters, such as fracture density distribution, orientation, and length distribution, and in terms of the representativity and predictability of data sets collected from restricted rock volumes.