Producing Oil Sands Thin Sections for Reservoir Characterization

Reservoir quality of oil sands can be observed directly in thin sections. Direct observation of important geological factors that control reservoir quality include: texture, grain size and sorting; grain orientation and packing; and any cementation if present. Additionally fines, which include silts and clays, such as clay infilling of pore spaces and the size as well as the shape of voids can be observed. Thin sections provide a means of detecting secondary physical/chemical processes that have altered the primary depositional texture which affects the final geometry of the pore structure. Geologic factors are known to directly impact reservoir porosity and permeability. As part of a large 2D to 3D case study, on the pore to grain scale, of oil sands from the Upper McMurray Formation thin section analysis was carried out. Samples used were obtained from a non-industry outcrop and non-industry cores with no industry funding in order to ensure fair practice. Oil sands as observed under the microscope exhibit a 2D fabric which is the result of the components including: primary grains; fines, such as silt and clay; bitumen and voids along with their spatial relationship. How oil sand fabric fit together going from 2D to 3D determine flow through the reservoir during recovery. The routine method of producing thin sections in unconsolidated material were employed for the oil sands samples with few modifications applied in order to identify an approach that would least alter the bitumen contained in the samples. Due to the unconsolidated nature of oil sands reservoirs, application of conventional thin sections methods must be modified and tailored for the unique nature of the oil sands. This short methods paper discusses producing thin sections from non-frozen samples and common artefacts which can occur during production.