Scanning Electron Microscope–Mineral Liberation Analysis (SEM–MLA) can be used to discriminate between hematite and magnetite in iron ores. However, achieving backscattered electron (BSE) segmentation between the two minerals is difficult for particles ≤75 µm using typical preparation and analysis methods for the MLA method based on a tungsten filament SEM (Quanta 400) with 25 kV high voltage. Preparing iron ore sample mounts using a slow-speed polishing method, and conducting the experiment on a field emission gun SEM–MLA (Quanta 650) with the high voltage setting lowered to 15 kV reduces instrument noise and results in very clean BSE images and segmentation. This method requires new X-ray standards for each mineral at 15 kV because of major changes in the spectra at lower kV. However, once these X-ray spectra are added to the mineral reference list, effective segmentation can be achieved and an accurate analysis obtained.

A novel approach to creating a trans-vertical grain mount embedded in epoxy has been demonstrated through the creation of a new mounting mould, as well as a polisher adapter and sample holder for the Quanta 400 SEM. These rectangular moulds result in a sample that is 30 mm long × 10 mm high × 17 mm wide, thus leading to the ability to polish 10 samples at once. Up to 14 samples may fit in the SEM holder for analysis. This represents an increase in efficiency of over 50%, and with a slow-speed polishing method, the consumables used are reduced by at least a factor of 4. This has the potential to lead to significant financial savings. A comparison of mounting techniques using a −100+200 mesh size fraction of an iron-ore sample from Labrador demonstrates that this new mounting system removes any bias in analysis resulting from density stratification during the sample preparation. These moulds yield similar modal mineralogy abundances and standard deviation as the two-step trans-vertical method, but they are less labour-intensive to make and more efficient to analyse.

Single-step trans-vertical moulds have been shown to increase the throughput of automated mineralogy systems. Owing to the small particle size of iron ore grains in the −200 mesh size fraction (<75 µm), not all of the surface area on a mould is needed for measurement in achieving good statistical representation. Trimming the excess area of a mould results in superfluous material being removed, leaving only the necessary analyte. This allows maximum packing in the sample chamber and promotes efficiency by increasing the quantity of samples that can fit in a newly designed trans-vertical adapter for an FEI MLA™ 650 field emission gun SEM. The analysis was completed using a newly designed sample block holder capable of holding 98 samples. This study represents the most expedient method yet reported to prepare well-polished samples and analyse them in a timely manner that can allow for quicker results in process mineralogy.

In reservoir engineering, special core analysis experiments (SCAL) are performed in the lab to evaluate the production capabilities of an oil reservoir. A critical component of SCAL experiments is core wettability restoration to its original wettability, i.e., oil wet condition. Typically, aging is performed by saturating the core with oil and aging at reservoir temperature where time is the variable in question dictating whether the resulting restored core is strongly or weakly oil-wet. In the lab, core wettability is often experimentally validated using contact angle measurements or USBM (United States Bureau of Mines) wettability tests, which are often time consuming, expensive and prone to error. In this study we developed a novel method by using Scanning Electron Microscope (SEM) and mineral liberation analysis (MLA) imaging (at low vacuum conditions) to determine the wettability of rocks saturated with reservoir fluids such as oil and brine. For this work a systematic approach was applied with comparing the SEM-MLA method against conventional methods to quantify the degree of uncertainty linked to a) wettability estimation and b) the aging time. We have used a comprehensive suite of core samples such as Berea, Silurian Dolomite and Chalk to represent the bulk of oil reservoirs in the world.

Single-step trans-vertical moulds used to prepare grain mounts for SEM-automated-mineralogy based instruments have been shown to lead to more representative sample statistics. For samples that contain a variety of mineral phases, denser phases can settle to the bottom of an epoxy mould during the curing phase. Slicing and polishing a cross section through density-stratified moulds of the sample material can compensate for this. Aliquots from offshore drill well cuttings were prepared using three different methods: (1) traditional epoxy mounting, (2) two-step trans-vertical moulds, and (3) single-step trans-vertical moulds. All were analysed with a FEI Quanta 650 FEG instrument using MLA software with similar acquisition parameters. The results indicate that the single-step trans-vertical moulds are reproducible, lead to more accurate statistics, and yield MLA calculated elemental assays that closely match with data from standard analytical methods. In addition, these moulds can be made in half the time of the two-step trans-vertical moulds, and because of the unique geometry of the custom-made SEM holders, the analytical throughput is doubled. Depending on the size fraction of the well cuttings, the throughput can be further increased by slicing off the remaining epoxy to allow for more samples in the 26x TV holder. A unique cell holder was created to accommodate these trans-vertical samples, allowing them to fit into a LA-ICP-MS instrument such that detailed follow-up microanalyses can be conducted on specific minerals. For instance geochronology can be conducted on grains of interest (e.g., zircons), which had been mapped by the SEM-MLA.