Regional Stratigraphically Discordant Dolomite Mapping Based on Dolomitization Mechanism on the Arabian Carbonate Shelf

Dolomite mapping as a first step towards a carbonate diagenetic modelling, is critical for understanding the dolomitization mechanism, and reservoir quality prediction. Stratigraphically discordant dolomite bodies within the Upper Jurassic intervals have long been studied on the Arabian Shelf. The proposed dolomitization mechanisms show that fluid movement is a key factor in dolomitization processes, and fracture as conduits of fluid movement controlling dolomite geometry. Therefore, faults/fractures served as migration conduits, determine dolomitization distribution by controlling fluid movement. Dolomite delineation in the study area is driven by the diagenetic mechanisms and comprehensive characterization of fracture systems in multiple scales. The complex fracture in the subsurface are categorized into macroscale, mesoscale, and microscale fractures according to the fracture size and seismic wavelength. Macroscale fractures, i.e. faults, are much greater than seismic wavelength and can be easily picked on seismic sections due to obvious seismic response. Mesoscale fractures are slightly greater or equal to seismic wavelength and can be recognized using seismic attributes. Microscale fractures are far smaller than seismic wavelength and can be observed mainly on core samples and thin-sections. The dolomite mapping workflow includes three steps: 1) calibrate seismic attribute characteristics with borehole image logs and core interpretations; 2) implement multiscale fracture characterization using multiple seismic attributes; and 3) interpret dolomite bodies based on fracture characterization and geological modelling. The mapping results show that massive dolomite bodies are heterogeneously developed and distributed mainly in the northeastern part of the study area, with a southward decrease in dolomite content, which is validated by well-based geological model. The results clearly demonstrate that multiscale fracture systems play critical roles in the massive dolomitization, which provides new insights on the dolomitization mechanism and subsurface reservoir and seal.