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| GEOTECH Homepage > Services > Petroleum Geochemistry Division > Sample Selection and Requirements | |
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Sample Selection and Requirements |
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Geochemistry can be performed on a variety of sample types: Sediments Geochemical analyses can be carried out on sidewall cores, conventional cores, outcrop samples and cuttings samples (wet or dry). If available, core samples are recommended over cuttings samples. If cutting samples are submitted for analysis, it is preferred that samples be washed and dried. However, in some cases (e.g. very fine-grained lithologies), unwashed samples are more suitable. Samples should not be stored in direct contact with plastic for long periods of time. It is recommended that any sample treatment be discussed with GEOTECH's geochemistry staff. In general, a full suite of source rock analyses can be carried out on 30-50g of material. It is sometimes possible to work with less than 30g, particularly with SWCs or with composite samples. For source rock screening analyses (TOC, Rock Eval) only a few grams of sediment is required. In the case of headspace analysis, cans (250ml minimum), three quarters filled with wet cuttings, are required. Oil Samples Oil samples (eg DST, MDT or stock tank samples) submitted for analysis should be as clean and representative as possible. Filtrates can be analysed as long as there is a sufficient oil layer to allow the sample to be skimmed from the surface. In some cases, solvent extraction of the filtrate is required in order to isolate the hydrocarbons. Liquid samples should ideally be stored in glass bottles and refrigerated. Oils should not be stored in plastic containers. Most oil analyses can be carried out on around 30ml of sample. However, for the determinations of some physical properties, larger volumes are necessary. Gas Samples Gases can be submitted for analysis either in gas cylinders or gas bags. Sample cylinders should be clearly marked with the sampling conditions, especially the cylinder pressure. A gas pressure of between 300psi and 500psi is ideal, but analyses can be performed on samples with lower or higher gas pressures. Gases should be at least 150cc in volume. After completion of analyses, clients will be contacted to determine whether samples need to be returned, disposed of, or stored at GEOTECH. |
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