Borehole Image Logs applied to Sequence Stratigraphy and Geothermal Exploration in Carbonates: an Integrated Workflow(UpperJurassic/Molasse basin).

Abstract

Summary Borehole image interpretation in carbonate reservoirs is very challenging. While fractures, faults and karst can often be recognized very well (especially if filled with conductive drilling mud) internal limestone texture is more challenging to identify. However, in some cases, diagenesis can significantly enhance such features and highlight details of the internal composition of carbonate rocks. This amount of detail allows classifying a total of 13 borehole image facies types for the Upper Jurassic limestone reservoir, which are calibrated with borehole cores and cuttings. The borehole image facies interpretation is now used to quality control seismic facies interpretation and further refine it. Vertical stacking of borehole image facies, important stratigraphic marker beds and surfaces reveal the sequence stratigraphic architecture and help to delineate genetically linked depositional units. Flow units (especially associated with karstification) are often found at sequence boundaries. Hence, a robust and validated sequence stratigraphic framework forms an essential part of the geothermal exploration strategy.