首页|Exploring a carbonate reef reservoir - nuclear magnetic resonance and computed microtomography confronted with narrow channel and fracture porosity
Exploring a carbonate reef reservoir - nuclear magnetic resonance and computed microtomography confronted with narrow channel and fracture porosity
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NSTL
Elsevier
The complexity of hydrocarbon reservoirs, comprising numerous moulds, vugs, fractures and channel porosity, requires a specific set of methods to be used in order to obtain plausible petrophysical information. Both computed microtomography (mu CT) and nuclear magnetic resonance (NMR) are nowadays commonly utilized in pore space investigation. The principal aim of this paper is to propose an alternative, quick and easily executable approach, enabling a thorough understanding of the complicated interiors of the carbonate hydrocarbon reservoir rocks. Highly porous and fractured Zechstein bioclastic packstones from the Bronsko Reef, located in West Poland were studied. Having examined 20 thin sections coming from two different well bores, 10 corresponding core samples were subjected to both mu CT and NMR experiments. After a preliminary mu CT-based image analysis, 9.4 [T] high-field zero echo time (ZTE) imaging, using a very short repetition time (RT) of 2 [mu s] was conducted. Taking into consideration the risk of internal gradients' generation, the reliability of ZTE was verified by 0.6 [T] Single Point Imaging (SPI), during which such a phenomenon is much less probable. Both narrow channels and fractures of different apertures appeared to be common within the studied rocks. Their detailed description was therefore undertaken based on an additional tool - the spatially-resolved 0.05 [T] T2 profiling. According to the obtained results, ZTE seems to be especially suitable for studying porous and fractured carbonate rocks, as little disturbance to the signal appears. This can be confirmed by the SPI, indicating the negligible impact of the internal gradients on the registered ZTE images. Both NMR imaging and mu CT allowed for locating the most porous intervals including well-developed mouldic porosity, as well as the contrasting impermeable structures, such as the stylolites and anhydrite veins. The 3D low-field profiling, in turn, showed the fracture aperture variations
ZTE imagingNuclear magnetic resonance relaxometryComputed microtomographyCarbonate reservoirFracture modelingChannel porosity
NSTL
Elsevier
