3D imaging of the pore network in the Shuaiba Reservoir, Al Shaheen field

Carbonate reservoir rocks often possess highly complex pore spaces, exhibiting extreme heterogeneity in the size, shape and connectivity of their pores at multiple scales. These variable features strongly impact oil recovery and pose severe challenges to reliable measurement and simulation of flow properties. As a complement to parallel studies of the plugs by conventional petrographic and core analysis techniques, a set of samples from four wells in the Shuaiba reservoir of the Al Shaheen field was analysed by 2D mineral mapping (from QEMSCAN) of polished plug sections, and by 3D tomographic mapping (from micro-CT) of subsampled mini-plugs, as a complement to parallel studies of the plugs by conventional petrographic and core analysis techniques. QEMSCAN showed a high variability in measured porosity and pyrite content over all sampled length scales, from millimetres (across the polished plug faces) to feet (with depth in a given well) to kilometres (across the four wells). The porosity from QEMSCAN was generally found to be in good agreement with that measured on the conventional plugs. Two mini-plugs of 5 mm diameter were scanned using helical micro-CT, one of which was subsequently analysed to segment the macropores, microporosity, calcite and pyrite. Comparison with the QEMSCAN results from the section of the "parent" plug showed consistency in estimated porosity and pyrite content between the two methods. Simulations of conductivity and absolute permeability were performed on subvolumes of the segmented tomogram, and displayed a strong variability with the location and size of the chosen subvolume, although the overall trends remained in good agreement with core analysis.