Jeroen Soete

A three-dimensional classification for mathematical pore shape description in complex carbonate reservoir rocks

Porous carbonates display some of the most complex porosity networks in reservoir rocks. This requires a quantitative geometric description of the complex (micro)structure of the rocks. Modern computer tomography techniques permit acquiring detailed information concerning the porosity network in three dimensions. These datasets allow a more objective pore classification based on mathematical parameters. In this study, ratios of the longest, intermediate, shortest dimensions and compactness of the pore shapes, based on an approximating ellipsoid, are analysed to obtain a thorough and objective description of pore shapes. Using intrinsic properties of the latter, the classification can be used at every resolution scale. Five shape classes are defined: rod, blade, plate, cuboid and cube. An additional advantage of this classification is that the data provide information about the orientation of the pores. This allows assessing the anisotropy of the porosity parameter. Apart from having an objective pore-type classification, analysing the shape and orientation of the pores permits to study the relationship with other important petrophysical rock characteristics such as permeability, acoustic properties and rock mechanical behaviour.

Multiscale approach to (micro)porosity quantification in continental spring carbonate facies: Case study from the Cakmak quarry (Denizli, Turkey)

Carbonate spring deposits gained renewed interest as potential contributors to subsurface reservoirs and as continental archives of environmental changes. In contrast to their fabrics, petrophysical characteristics - and especially the importance of microporosity (< 1 mu m) - are less understood. This study presents the combination of advanced petrophysical and imaging techniques to investigate the pore network characteristics of three, common and widespread spring carbonate facies, as exposed in the Pleistocene Cakmak quarry (Denizli, Turkey): the extended Pond, the dipping crystalline Proximal Slope Facies and the draping Apron and Channel Facies deposits formed by encrustation of biological substrate. Integrating mercury injection capillary pressure, bulk and diffusion Nuclear Magnetic Resonance (NMR), NMR profiling and Brunauer-Emmett-Teller (BET) measurements with microscopy and micro-computer tomography (mu-CT), shows that NMR T-2 distributions systematically display a single group of micro-sized pore bodies, making up between 6 and 33% of the pore space (average NMR T-2 cut-off value: 62 ms). Micropore bodies are systematically located within cloudy crystal cores of granular and dendritic crystal textures in all facies. The investigated properties therefore do not reveal differences in micropore size or shape with respect to more or less biology-associated facies. The pore network of the travertine facies is distinctive in terms of (i) the percentage of microporosity, (ii) the connectivity of micropores with meso- to macropores, and (ii) the degree of heterogeneity at micro- and macroscale. Results show that an approach involving different NMR experiments provided the most complete view on the 3-D pore network especially when microporosity and connectivity are of interest.

Applications of CT for Non-destructive Testing and Materials Characterization

Several important technological and economic trends are shaping the research on non-destructive testing techniques. X-ray computed tomography is also a NDT product of these ongoing developments and has become a very important tool for doctors, material scientists, geologists, biologists, civil engineers, bio-engineers, dentists, quality engineers, etc., all dealing with materials of which the fine internal structure or the changes within the material are of outmost importance to understand the behaviour of the material or to have insights in the processes going on. X-ray CT with micron- and submicron resolution is now well accepted in those disciplines. In the next paragraphs a wide variety of application fields will be addressed in order to show how X-ray CT can be applied as an NDT technique for quality control, the study of the material behaviour and its functional properties under specified environmental conditions, and for production and material optimization.

Lattice Boltzmann Simulations of Fluid Flow in Continental Carbonate Reservoir Rocks and in Upscaled Rock Models Generated with Multiple-Point Geostatistics

Microcomputed tomography (μCT) and Lattice Boltzmann Method (LBM) simulations were applied to continental carbonates to quantify fluid flow. Fluid flow characteristics in these complex carbonates with multiscale pore networks are unique and the applied method allows studying their heterogeneity and anisotropy. 3D pore network models were introduced to single-phase flow simulations in Palabos, a software tool for particle-based modelling of classic computational fluid dynamics. In addition, permeability simulations were also performed on rock models generated with multiple-point geostatistics (MPS). This allowed assessing the applicability of MPS in upscaling high-resolution porosity patterns into large rock models that exceed the volume limitations of the μCT. Porosity and tortuosity control fluid flow in these porous media. Micro- and mesopores influence flow properties at larger scales in continental carbonates. Upscaling with MPS is therefore necessary to overcome volume-resolution problems of CT scanning equipment. The presented LBM-MPS workflow is applicable to other lithologies, comprising different pore types, shapes, and pore networks altogether. The lack of straightforward porosity-permeability relationships in complex carbonates highlights the necessity for a 3D approach. 3D fluid flow studies provide the best understanding of flow through porous media, which is of crucial importance in reservoir modelling.