Abstract
The Grosmont and Nisku carbonate formations combined contain more than 25% of Alberta's crude bitumen on the basis of initial in-place volumes, making carbonates a significant potential source of bitumen in Alberta. About 400 billion barrels of bitumen is estimated to be located in the Upper Grosmont units1. We have studied seven cores from increasing depth in the formation. X-Ray diffraction data of core particles showed pervasive dolomitization and only minor differences were observed in trace clay and calcites. The cores with trace clay and calcite impurities appeared to have the highest bitumen content. Dean-Stark analysis of four selected cores sub-samples revealed that bitumen contents ranged from 5.84 to 15.4 wt%, with negligible water present in the as-received samples. Photoacoustic Fourier transform infra red spectroscopic analysis (FTIR-PAS) of core solids surfaces before and after the bitumen was extracted showed minor differences among surfaces of the particulates from Upper Ireton (UIR) to Upper Grosmont carbonate (UGC). The organics coatings, not visible by the naked eye, were revealed earlier by fluorescence microscopy and from these previous studies showed how solubility in water was affected.2 Asphaltene contents of bitumens extracted from the cores were all higher than for typical Athabasca oilsand bitumens. Bitumen viscosities measured as a function of temperatures using a falling ball viscometer and a rotational rheometer with plate-plate geometry at constant low shear indicated small differences among the bitumen samples and between the dolomitic bitumens compared to oilsands and SAGD bitumens studied before. Arrhenius fits gave activation energies within experimental errors for the two methods used. Densities measured as a function of increased temperatures were above those of water and varied among samples.
