High Resolution Fracture Analyses and 3d DMX DFN Modeling of Triassic Dolomites;Wadi Bih,Ras Al Khaimah UAE

摘要

The present paper regards a high-resolution 3d fracture DMX modelling exercise applied to Triassic dolomites of the Ghail Fm,outcropping along Wadi Bih in the territory of Ras Al-Khaimah(UAE).The outcropping rocks show a low primary porosity,are well bedded and highly fractured(jointed)up to cm scale.They are an equivalent of the hydrocarbon producing Khuff Fm in the subsurface,and as such the exersice shows the relevance of applying new technologies to outcrop observations to confront with subsurface situations.Secondly,the exersize shows several new unique elements and related technologies not presented previously.The workflow presented which allows to arrive from observations to a 3d data driven fracture model,applying new technologies and algorithms using specific modules of the DMX protocol.Data collected comprise direct hand measurements of fractures and bedding planes,and 3d calibrated HR photographs.The scale of the model ranges from cm to meter scale fractures(core to borehole image scale).The parameters that have been analysed are size(length,height),orientation(set recognition),truncation relationships(BIXTV)between fractures and bedding planes,and spatial distribution(spacing)of the single fracture sets.The analyses and confrontation between the bedding tilt and the orientation of the 5 recognised fracture sets demonstrates that the fracture network is passively tilted with the bedding plane.A methodology is presented to arrive from in principle 1d(lineament)observations upon 2d sections(bedding planes surfaces and vertical sections)to statistical models and the usage in 3d fracture modeling.The resulting 3d model is generated as a Data Driven Model using the DMX protocol,which is directly connected to the observed features which are themselves present in the model,and comprises 5 sets with the following parameters reflecting the observed mathematical models:Specific spatial spacing relationships,size distributions(lengths and heights),relationships with modelled bedding plane surfaces,undulation of fractures,and 3d spatial truncations(XTV)between fractures and between fractures and bedding planes.This model is interrogated for 3d connectivity in different directions,P32 density(related to fracture porosity)and can be confronted with subsurface datasets from(preferably oriented)cores.The example shows for the first time how relatively simple and straightforward observations,which can be collected by hand,or with 3d stereofotogrammetrical techniques or drone technologies,can be used to build 3d analogue models that accurately mimic geological relationships.